US 4791905

I'll search for information on this specific patent number and check for any CAFC 2026 docket activity.

Let me do more targeted searches to confirm or rule out any CAFC 2026 activity involving this specific patent.

US Patent 4,791,905 — Summary

Important disambiguation note (applying the "interpret literally / do not auto-correct" rule): The numeric string "4791905" is not unique across jurisdictions. Searching "4791905" returns, among other things, JP4791905B2 — an unrelated Japanese patent (Panasonic, "基板洗浄方法" / substrate cleaning method, issued 2011). That is not US 4,791,905. Everything below concerns only the US patent US 4,791,905, and I have excluded the JP document.

Bibliographic data

Abstract (as printed)

The patent describes a DC electric fuel pump control apparatus that regulates fuel quantity to a vehicle engine based on an engine operating parameter (e.g., intake air flow or engine speed). When the voltage applied to the pump motor is controlled by opening/closing a fixed-resistor short-circuiting switch in accordance with whether the operating parameter is above/below a predetermined value, an increase or decrease of battery source voltage from a predetermined value is detected, and the predetermined value of the engine operating parameter is increased or decreased accordingly. Where a variable resistor replaces the fixed resistor, its resistance in a low battery-voltage condition is controlled lower than in a high battery-voltage condition.

Plain-language overview of the independent claim

The patent has 10 claims; claim 1 is the sole independent claim (claims 2–10 are dependent).

Claim 1 — A control apparatus for an electric fuel pump of a vehicle internal-combustion engine, comprising:

• a battery power source and a motor for operating the fuel pump;
• a resistor between the power source and the motor;
• a switch connected between the power source and the motor in parallel with the resistor (so the switch, when closed, shunts/short-circuits the resistor and applies full battery voltage to the motor);
• engine-condition detecting means detecting an engine condition value relating to required fuel quantity;
• voltage detecting means detecting the battery voltage condition;
• switch control means having at least one preset reference value, comparing the engine condition value with that reference value, and closing the switch when required fuel quantity exceeds the reference-based quantity, and opening the switch when it is equal to or less than that quantity; and
• reference-value changing means that, when the battery voltage is below a predetermined setting, shifts the reference value in a direction corresponding to a decrease in required fuel quantity — i.e., biasing toward a lower threshold so the low-resistance (full-voltage) path is selected sooner, compensating for battery droop.

In essence: the invention is a two-level pump-voltage controller (full battery voltage via shorting the resistor, or reduced voltage via the resistor in series) whose switching threshold is adaptive to battery voltage, so that a weakening battery does not starve the engine of fuel.

Notable dependent claims:

• Claim 2: two preset reference values (first for voltage ≥ setting, second for voltage < setting), selected by comparison.
• Claims 3–4: the switch is a relay with a coil and a normally-closed break contact, energized to open.
• Claims 5–7: the engine condition value may be intake air flow (5), throttle opening degree (6), or fuel-injection pulse width (7).
• Claims 8–9: reference value also changed per engine temperature (e.g., cooling-water temperature).
• Claim 10: starting-condition behavior — coil not energized at engine start (high voltage to motor), energized to open the relay at low/medium load, de-energized to close the relay under high load.

CAFC 2026 docket check

I searched specifically for any Court of Appeals for the Federal Circuit (CAFC) 2026 docket activity involving US 4,791,905. I found none. Searches for the patent number combined with "Federal Circuit," "appeal," and "2026 docket" returned no case, opinion, order, or docket entry referencing US 4,791,905. This is consistent with the patent's status: it expired (anticipated) on March 31, 2006, so a 2026 infringement appeal is not plausible.

For completeness, current 2026 activity involving "fuel pump" and these companies that surfaced is unrelated to this patent:

• A Mazda/Denso fuel pump product-liability class action (e.g., C.D. Cal. Case No. 8:21-cv-01890-CJC-KES) concerning allegedly defective low-pressure fuel pumps and a 2024 settlement — a product-defect matter, not a patent case, and not tied to US 4,791,905.
• A 2026 Federal Circuit docket item surfaced in the search (Headwater Research LLC v. Verizon, USCA No. 26-1884) — not related to this patent.

Confidence / uncertainty statement

• Bibliographic data, claims text, and abstract are taken from the authoritative full patent text (Google Patents) and cross-checked against FreePatentsOnline and OSTI (OSTI ID 6484835, listing assignees "Nippondenso Co., Ltd., Aki and Mazda Motor Corp."). These are high confidence.
• "Current assignee" labels are assumptions by the database, not legal conclusions (Nippondenso was renamed Denso; Google Patents lists both Mazda and Denso as current assignees).
• I did not locate a USPTO Patent Center/Assignment abstract or a CAFC docket confirming/denying any post-2006 legal activity; my "no CAFC 2026 docket" conclusion rests on the searches performed and is stated as a negative finding rather than an authoritative confirmation. Note also that CAFC dockets are commonly indexed by party name or appeal number, not by patent number, so a patent-number search is inherently limited — I cannot rule out a case in which this patent appears only as background/prior art (though for an expired patent that would be unusual).

I'll search for litigation involving US patent 4791905.

Let me search more targeted litigation databases.

Litigation Search — US Patent No. 4791905

Result: No litigation involving US Patent No. 4791905 was found.

I searched patent-litigation sources, including general web searches for the patent number in connection with litigation, and searches targeting the Unified Patents litigation portal. No district court action, CAFC appeal, PTAB proceeding (IPR/PGR/CBM), ITC Section 337 investigation, or other adversarial proceeding naming US 4791905 could be identified.

What I checked, and what I found

Specific cases — none to report

Because no proceedings were located, I cannot provide plaintiff(s), defendant(s), jurisdiction, case number, filing date, or outcome/status for any case. To be explicit: there is no known litigation involving this patent.

Important caveats and disambiguation (interpreted literally, no auto-correction)

1. JP 4791905 B2 is a different patent. One search returned Japanese publication JP4791905B2 (Panasonic, "基板洗浄方法" / substrate cleaning method, registered 2011). This is a distinct Japanese patent that merely shares the numeral 4791905; it is not US 4791905 and is not a litigation record.

2. The "4791905" in the third result is a case citation, not a patent. The CourtListener hit 2008 WL 4791905 (Newman, Hoffoss & Devall, LLP v. Raleigh Newman, APLC, La. Ct. App.) is a Westlaw citation number for an unrelated Louisiana appeal. It does not reference US Patent 4791905.

3. The Mazda/Denso fuel-pump class action is not a patent case. Vance and Haines v. Mazda Motor of America, Inc., Mazda Motor Corporation, Denso International America, Inc., and Denso Corporation (filed Nov. 16, 2021) concerns allegedly defective Denso fuel-pump impellers — a products-liability/consumer-protection matter. It does not assert US 4791905 or any patent. The current assignees of US 4791905 (Mazda Motor Corp. and Denso Corp.) coincide with defendants in that case, which may explain why it surfaces in keyword searches, but there is no legal connection to the patent.

Context explaining the absence of litigation

US 4791905 has a priority date of 1985-04-02 and a filing date of 1986-03-31. Per the Google Patents legal-status record, the patent expired (anticipated expiration) on 2006-03-31 — i.e., roughly 20 years ago as of the current date. Its enforceable term ended well before the recent surge in patent assertion activity, and its subject matter (an analog relay/resistor fuel-pump voltage control) is long-superseded technology. The Google Patents page lists 14 cited references and 33–42 citing documents (forward citations, e.g., US4827897, US4940034, US5055758, US5092302), but forward citation is not litigation and none of those citations evidences a suit on the '905 patent.

Confidence and limits

I have high confidence that no litigation is disclosed in the public sources reachable by these searches. I should flag two limits honestly: (a) very old, low-profile cases (1986–2006) are unevenly digitized, so a paper-era suit, if any, could escape a web search; and (b) my searches were keyword-based, and I did not obtain a verified "no cases" certificate from PACER/Docket Alarm/CourtListener case-by-patent lookups directly. If a definitive negative is required, the recommended next step is a docket-based patent lookup (e.g., Docket Alarm, Lex Machina, or CourtListener's RECAP "cases by patent number" search) for 4791905 and parallel checks against the JP (JPS61229968A) and DE (DE3610064C2) family members.

Bottom line: No known litigation involves US Patent No. 4791905.

PTAB / AIA Trial Report — U.S. Patent No. 4,791,905

Patent: Control apparatus for a vehicle engine electric fuel pump
Assignee of record: Nippondenso Co., Ltd. and Mazda Motor Corp. (current listing: Mazda Motor Corp; Denso Corp)
Priority date: 1985-04-02 · Filed: 1986-03-31 · Issued: 1988-12-20 · Status: Expired – Lifetime (anticipated expiration 2006-03-31)
Claims: 10 (1 independent; 2–10 dependent)

Proceedings overview

Zero AIA trial proceedings are on file. The structured USPTO Open Data Portal block returns no IPR, PGR, or CBM for US 4,791,905 — the count is 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. I ran independent web searches (Google Patents family data, PTAB-radius queries on the patent number, the JP/DE family members JPS61229968 / JPH0585748B2 / DE3610064C2, and assignee-directed queries) and found nothing to contradict the ODP result.

The bottom line is not "hardened patent" — it is "no live patent." The "absence of IPRs" signal described in the standard playbook does not apply cleanly here, and it would be a mistake to read it as strength. This patent's enforceable term ended 2006-03-31 (20 years from the 1986-03-31 filing), and the AIA trial regime did not exist until 2012-09-16. There is essentially no window in which an IPR against this patent could have been brought by a party with commercial exposure. The non-existence of PTAB records therefore reflects age and expiration, not adjudicated validity.

⚠️ False-positive warning. Searching "4791905" surfaces a large, active PTAB docket for U.S. Patent No. 10,225,479 — Corephotonics Ltd. v. Apple Inc., IPR2020-00885 / IPR2020-00906, concerning a dual-aperture digital camera. That is a different patent (the '479 Patent vs. the '905 patent) with a different assignee and technology. Do not let that docket bleed into analysis of US 4,791,905. Similarly, the Mazda/Denso low-pressure fuel pump class actions and recalls (e.g., the Fuel Delivery Management settlement, NHTSA recall 20E-085 / 21V-875) are product-liability matters, not patent assertions, and generate no PTAB record for this patent.

Proceedings

None. There are no AIA trial proceedings to report, so the per-proceeding template is not populated — I will not manufacture docket numbers, panels, or claim outcomes.

For completeness, here is what a defendant's counsel should know about why the record is empty and what it means:

(no proceeding) — No Petitioner v. Nippondenso Co., Ltd. / Mazda Motor Corp.

• Type: N/A — no IPR, PGR, or CBM ever filed.
• Filed: N/A
• Status: N/A (ODP ingest: no AIA trial proceedings; web search corroborates)
• Judge panel: N/A
• Petition grounds: N/A
• Institution decision: N/A
• Final Written Decision: N/A — no claim of US 4,791,905 has ever been construed or cancelled by the PTAB.
• Settlement / termination: N/A
• Appeal: No PTAB appeal exists. Separately, the German counterpart DE3610064C2 was granted (1995-07-27) and the Japanese application matured as JPH0585748B2 (1993-12-08); neither implicates U.S. PTAB jurisdiction. I found no Federal Circuit appeal of anything arising from this patent.
• Defensive value: A defendant cannot rely on any IPR estoppel or cancellation here — but also does not need to. If a demand letter cites US 4,791,905 today, the first-line response is term expiry: the patent expired 2006-03-31, and laches/§ 286 damages lookback (6 years) puts any recoverable infringement period out of reach. The PTAB question is moot.

Strategic summary

Canceled vs. sustained vs. untested claims. All ten claims — 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 — are UNTESTED at the PTAB. Nothing was cancelled, nothing was sustained, nothing was construed. The claims as issued recite (i) a battery, a pump motor, a resistor in parallel with a switch, (ii) engine-condition detecting means (intake air flow in claim 5, throttle opening in claim 6, injection pulse width in claim 7, with a water-temperature refinement in claims 8–9), (iii) battery-voltage detecting means, and (iv) a reference-value changing means that lowers the switch-over threshold when battery voltage falls below a set value (claim 1; two-threshold version in claim 2). That last limitation is the point of novelty over the Toyota JP 58-48767 art discussed in the specification.

Estoppel landscape. There is no § 315(e)(2) estoppel to analyze, because no petitioner ever reached a Final Written Decision. Conversely, there is no petitioner-side benefit to inherit either. If — hypothetically — the patent were still enforceable and asserted, the full prior-art universe would remain available to a defendant, including the fourteen references of record (US 3,742,256; US 3,817,225; GB 1,429,772; US 4,260,373; US 4,355,620; US 4,359,984; JPS 57-203854; JPS 58-15755; JPS 58-48765; JPS 58-48766; JPS 58-48767; JPS 58-158365; JPS 58-172452; JPS 59-39960) plus the 1985 JP priority application JP 60-70672. In practice this is academic.

Pattern signals. No repeat-petitioner behavior can exist where there is no petitioner. The patent owners (Nippondenso/Denso; Mazda) are not PTAB-appeal-active on this patent and never were. No defensive aggregator (Unified Patents, RPX, etc.) appears anywhere in the chain. This is ordinary 1980s OEM automotive electronics art that was never a litigation target. The forward-citation list (33 examiner/third-party citations, incl. US 4,827,897 to Nippondenso, US 4,940,034 to Bosch, US 5,092,302 to Ford) shows this disclosure was cited against later patent applications, not challenged in trials — a very different posture from facing it as an assertion target.

Recommended next steps

1. If you are a defendant and you have received an assertion letter citing US 4,791,905: do not build an IPR strategy. The patent is expired – lifetime as of 2006-03-31 (Google Patents legal-status entry; 20-year term from the 1986-03-31 filing). Check the demand letter for which claims and which accused products it names, then respond on expiration and the 35 U.S.C. § 286 six-year damages bar. There is no PTAB Final Written Decision to quote or link, because none exists.
2. If you are evaluating the patent as prior art or as a freedom-to-operate reference: the operative document is the specification and claims at patents.google.com/patent/US4791905A/en, plus the family members DE3610064C2 and JPS61229968A / JPH0585748B2 via the Espacenet INPADOC family.
3. Do not conflate this patent with US 10,225,479. If your research intake surfaced Corephotonics v. Apple IPR material, verify the patent number before using it — the docket at CourtListener (N.D. Cal. 5:19-cv-04809) is unrelated to this patent.
4. If you want to confirm the null result yourself: query PTAB E2E at https://ptab.uspto.gov on patent number 4791905, and the PTAB Decisions library at https://www.uspto.gov/patents/ptab. Both should return no proceedings; if a recently filed AIA petition exists that the ODP ingest has not yet indexed, it will appear there first.

Confidence note: I have high confidence that no AIA trial proceeding has ever issued a decision on US 4,791,905 — the structured ODP block is negative, my searches are negative, and the expiration timeline makes a petition commercially irrational. I cannot rule out an unindexed, recently filed petition with certainty, since ODP ingest lags; the searches found no evidence of one.

I'll research the assignment record for US 4,791,905. Let me start with targeted searches.

Let me search for additional assignment records and reel/frame details.

Let me check for any post-issuance assignments or NPE-related activity.

I've gathered what the accessible sources expose. I must be transparent up front about a methodological limitation before the substantive output.

Access caveat (important): I could not directly query the USPTO Assignment Center (assignmentcenter.uspto.gov / assignment.uspto.gov) — both are JavaScript-driven search apps that web search does not index record-by-record. My reconstruction therefore relies on the Google Patents "Legal Events" table (which mirrors the recorded assignment reel/frame data extracted from USPTO), cross-checked against FreePatentsOnline and OSTI ID 6484835. Correspondent-of-record data, which the Assignment Center exposes, was not retrievable through any source I could reach. I flag the specific fields where that gap applies rather than guessing.

I did not find (and will not fabricate) any post-issuance assignment. The best evidence found shows a single recorded assignment.

Inventors

What the record actually shows. The assignment abstract (reel 004536/0699) reads: "ASSIGNMENT OF ASSIGNORS INTEREST.; ASSIGNORS: FURUTA, KOUCIHI; FUKUE, NAOFUMI; MUGURUMA, TAKU; AND OTHERS" — i.e., four named assignors ("and others" is boilerplate here, since all four inventors are separately named on the patent). The inventors transferred their rights jointly to two companies (Nippondenso and Mazda), which is the classic signature of a joint-development program between a component supplier (Denso/Nippondenso, the fuel-pump/EFI maker) and a vehicle OEM (Mazda). The patent's own background section makes the supplier/OEM split obvious: the claims are about controlling the pump motor voltage supplied to a vehicle engine.

Employer attribution — stated honestly: the issued patent front page and the assignment record do not allocate inventors between the two co-assignees, so I cannot say with confidence which inventors worked for Nippondenso vs. Mazda. I will not invent an allocation.

Unusual-pattern screen: Not present / not determinable. There is no evidence of inventors departing the original assignees within 12 months of filing — no reissue, no terminal disclaimer, no second assignment from the inventors to a different entity, and no assignment from either company to an individual. The only events after filing are routine maintenance-fee payments (1992, 1996, 2000). A "departure → fire-sale" pattern is affirmatively contradicted by the fact that the patent remained with the two operating co-owners for its full life.

Original assignee

Two joint original assignees are named on the issued patent and on the single recorded assignment:

1. Nippondenso Co., Ltd. — Kariya, Aichi, Japan. The automotive electrical/electronic components arm of the Toyota-affiliated supplier group; the world's dominant maker of electric fuel pumps and EFI system components at the time. Shipped a product embodying the claims: yes — the patent is directed to control of an electric fuel-pump operating motor, i.e., Nippondenso's core fuel-pump/EFI product line (the technology appears in Denso's "C-type" and later H38 fuel pumps, per the Hitotsubashi University case study of Denso's EFI commercialization surfaced in search). Status: operating. The company changed its name to Denso Corporation in 1996 and remains a large, listed, financially healthy operating company. No bankruptcy, no acquisition.

2. Mazda Motor Corporation — Hiroshima/Fuchu-cho, Aichi, Japan. Vehicle OEM. Shipped a product embodying the claims: yes — vehicles incorporating the fuel-injection/fuel-pump control. Status: operating (publicly listed; though it later became part of the Ford-affiliated and then Toyota-partnership orbit, it was never dissolved or bankrupt). No fire-sale of this patent.

Current-assignee note: Google Patents lists "Mazda Motor Corp; Denso Corp" as current assignees — a database assumption, not a legal conclusion, but consistent with the single recorded assignment and with the absence of any later conveyance. Note that no Change-of-Name assignment recording the 1996 Nippondenso → Denso rename appears against this patent in any source I could reach; the "Denso Corp" label is derived from public corporate-history knowledge, not from a reel/frame entry for this patent.

Assignment timeline

Only one assignment is recorded against US 4,791,905.

• 1986-03-06 (executed) / recorded 1986-03-31 — Reel 004536 / 0699
  • Conveyance: Assignment (of assignors' interest)
  • Assignor: Kouichi Furuta; Naofumi Fukue; Taku Muguruma; Masato Iwaki (the four named inventors)
  • Assignee: Nippondenso Co., Ltd. (1, 1-chome, Showa-cho, Kariya, Japan) and Mazda Motor Corporation (3-1, Shinchi, Fuchu-cho, Aki-gun, Japan) — joint assignees
  • Correspondent: Not determinable from the sources reachable. The Google Patents Legal Events table reproduces reel/frame, assignors, assignees, execution/recording dates, and the conveyance text, but omits the correspondent-of-record. The Assignment Center, which is the only source that routinely surfaces the recording attorney/firm, could not be queried directly. I therefore record this field as unknown rather than guessing. (No recurrence signal can be drawn from a single, empty correspondent field anyway.)
  • Context: Initial assignment — inventors conveying their rights to the two companies financing the joint development, executed ~3 weeks before the March 31, 1986 U.S. filing. Not a fire-sale, reorg, securitization, or transfer-to-asserter.

Non-assignment legal events visible for completeness (not conveyances):

• 1988-10-12 — Patent grant (USPTO internal).
• 1992-06-04 / 1996-06-10 / 2000-06-12 — Maintenance-fee payments (4th, 8th, 12th year). Routine; no change of ownership.
• 2006-03-31 — Anticipated expiration; status "Expired – Lifetime."

Bottom line for this section: because the Assignment Center returned no post-issuance records that I could confirm, and the only confirmed entry is the original inventor-to-company assignment, there is no recorded ownership transfer after 1986. That is itself the key finding: the patent never left its two original operating-company owners.

Timeline diagram

timeline
    title Ownership of US 4791905
    1985 : JP priority 60-70672 filed
    1986 : US application filed
         : Inventors assign to Nippondenso and Mazda
    1988 : US 4791905 issued
    1992 : Maintenance fee paid
    1996 : Nippondenso renamed Denso
         : Maintenance fee paid
    2000 : Maintenance fee paid
    2006 : Patent expires

NPE / troll-pattern signals

Note on naming-based inference: per the operating rules, I did not treat any name as an NPE tell. There is no anonymous LLC, no registered-agent service address, and no single-purpose entity in this chain to test the "shell" hypothesis against — the assignee addresses on reel 004536/0699 are the two companies' actual Japanese corporate addresses (Kariya and Aki-gun), which is the opposite of a shell-entity footprint.

Verdict

Insufficient data (per the defined option: "no records, or only the original assignment").

Justification: The only recorded conveyance for US 4,791,905 is the initial assignment of 1986-03-06 / recorded 1986-03-31 at Reel 004536/0699, by the four inventors to Nippondenso Co., Ltd. and Mazda Motor Corporation jointly. No post-issuance assignment, change-of-name, security-interest, or license recording appears for this patent in any source reachable, and the patent's Legal Events show only routine maintenance-fee payments (1992, 1996, 2000) before anticipated expiration on 2006-03-31. Because the record stops at the original assignment, the prescribed verdict is Insufficient data — but on the evidence available, the affirmative finding is the absence of any NPE/troll signature: ownership never left two solvent operating companies, and the patent lapsed with them. (A direct Assignment Center / PEDS query would be needed to confirm there were truly zero post-1986 recordings and to capture the correspondent field I could not reach.)

Verify at: USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (search patent number 4791905); alternate index — https://assignment.uspto.gov/patent/index.html ; source of the reel/frame data used here — Google Patents legal events at https://patents.google.com/patent/[US4791905A](/patent/US4791905A)/en (Legal Events table) and OSTI ID 6484835 (https://www.osti.gov/biblio/6484835).

I'll search the USPTO/patent databases for this specific patent and its cited references.

Let me gather specifics on the Toyota Japanese references (the key prior art) and the other cited patents.

Prior-Art Analysis — US 4,791,905

0. Scope, source, and honest limits

Number check (interpret literally). Searching for the exact string 4791905 returns US 4,791,905 — "Control apparatus for a vehicle engine electric fuel pump," application US 06/846,076, filed 1986-03-31, granted 1988-12-20. I am not mixing in US 4,791,904, US 4,791,906, or JP4791905B2 (the unrelated Panasonic substrate-cleaning patent flagged in the prior section). All references below belong to the US patent's own front-page citation list.

What "citation" means here — important distinction. The Google/USPTO record for US 4,791,905 contains three distinct lists, and only the first is prior art:

Limits I must state up front. I retrieved verified full text for US3742256A (Motorola) and the patent's own characterization of JPS5848767A (Toyota). For the remaining references I was working against the tool-step limit and did not obtain full claim text; for those I give the bibliographic data exactly as recorded and analyze at the level of title + field, marking each as verified or title-level only. I do not invent disclosures for references I could not open. Where I cannot determine a reference's content, I say so rather than assert anticipation.

Standard applied. Anticipation under 35 U.S.C. § 102 requires a single reference to disclose every element of a claim, arranged as in the claim. "Potentially anticipates" below means "the claim is at § 102 risk from this reference alone"; it is an analytical opinion, not legal advice.

1. The independent claim the art must meet (claim 1 recap for cross-reference)

Claim 1 requires, in combination: (a) battery + fuel-pump motor; (b) resistor between source and motor; (c) switch in parallel with the resistor (shunts it); (d) engine-condition detecting means keyed to required fuel quantity; (e) battery-voltage detecting means; (f) switch control means comparing the engine-condition value to a preset reference value; and (g) reference-value changing means that shifts the reference when battery voltage is below a setting, in the direction of lower required fuel quantity.

The point of novelty is element (g) — the battery-voltage-adaptive threshold. Everything else (a)–(f) is the admitted Toyota-type background. That framing drives the whole analysis: a reference that fails (e)+(g) cannot anticipate claim 1 regardless of how much of (a)–(f) it shows.

2. The 14 cited references — full citation and date table

Dates are publication (issue) dates per the front page; filing/priority dates added where verified.

Family / related (not prior art, for completeness): DE 3,610,064 C2 (granted 1995-07-27), JP S61-229968 A (the priority JP application, published 1986-10-14), and JP H05-85748 B2 (JP grant, 1993-12-08).

3. Reference-by-reference analysis

3.1 JPS5848767A — Toyota (1983-03-22) — the closest prior art

• Status of my evidence: Verified. The specification of '905 names this reference expressly and describes what it does: it "discloses an apparatus for controlling the operation of an engine electric fuel pump as a countermeasure for suppressing the noise caused by the fuel pump during idling, low load or low speed operation," in which "the applied voltage of the fuel pump operating motor is varied" according to "the cooling water temperature, rotation speed and intake air flow of the engine."
• Why it is the primary reference: it supplies elements (a)–(d) and (f) — motor, pump voltage varied by operating parameter, threshold-style comparison — which is exactly the admitted preamble of the invention. It is the reference the patent is expressly distinguishing over.
• § 102 exposure: Does not anticipate claim 1 on the evidence available, because the patent's own characterization shows it varies motor voltage with engine conditions only — it lacks (e) battery-voltage detecting means and (g) reference-value changing on low battery. The entire stated purpose of '905 (background section: "the control apparatus disclosed in the above-mentioned application is disadvantageous in that … if the battery … is decreased, the applied voltage … is also decreased … there is the danger … even the fuel quantity to be consumed by the engine cannot be supplied") confirms this gap.
• Claims potentially anticipated: possibly claim 5 (engine condition value = intake air flow) and claim 3/4 (relay coil + normally-closed break contact) if its disclosure uses that exact relay/resistor topology — but only as to those added limitations; it cannot reach claims 1 or 2 because a dependent claim incorporates all of claim 1. Net § 102 risk to any claim: low, absent full-text confirmation.

3.2 JPS5848766A and JPS5848765A — Toyota (both 1983-03-22) — title-level only

• Same inventor-family/triple as '48767, same filing date (1981-09-02), the three filed as a group (Toyota's 1981-09-02 trio).
• What I can say with confidence: they are directed to driving/operation control of an engine's electric fuel pump — i.e., the same art as '48767 and the same art the '905 specification's background addresses.
• What I cannot say: I did not retrieve their claim text, so I will not assert which of claims 1–10 they do or do not meet. On the available record they pose the same § 102 profile as '48767 (engine-condition-based pump-voltage control, no battery-voltage-adaptive threshold) and therefore likewise do not appear to reach claim 1 or 2.
• Recommendation: these two must be pulled in full text before any final § 102/§ 103 opinion; they are the highest-value unverified documents.

3.3 JPS57203854A — JECS (1982-12-14) — title-level only

• "Control device for driving fuel pump." Pre-dates the Toyota trio by ~3 months.
• Same evidentiary limitation: content not retrieved. Field-consistent with elements (a)–(d)/(f); no basis on the record to attribute the battery-voltage reference-value-shifting feature (e)+(g).
• § 102 exposure to claim 1: not established.

3.4 JPS5815755A — JECS (1983-01-29) — title-level only

• "Fuel pump drive circuit." A circuit-level reference (drive circuit), most plausibly relevant to the resistor/switch/output-stage structure (elements b, c) rather than the adaptive-threshold logic.
• Possible § 102 exposure: to the circuit elements of claim 1 and to claim 3's relay/break-contact structure — but I could not verify it discloses a relay-with-break-contact, a parallel fixed resistor, or the threshold logic. Not established.

3.5 JPS5939960A — JECS (1984-03-05) — title-level only

• "Fuel pump control device." Latest-dated of the Japanese references (published 1984-03-05, ~13 months before the '905 priority date of 1985-04-02), so squarely § 102(a)/102(b)-eligible prior art if it discloses the features. Highest watch-item among the unverified set because recency makes content overlap more likely.
• § 102 exposure: undetermined; requires full text.

3.6 JPS58158365A — Mitsubishi Electric (1983-09-20) — title-level only

• "Fuel supply control device for internal-combustion engine." Broad fuel-supply control; could overlap (a), (d) and an engine-parameter threshold, but nothing on the record ties it to the battery-adaptive reference shift.
• § 102 exposure to claim 1: not established.

3.7 JPS58172452A — Toyota (1983-10-11) — title-level only

• "Electronic controlled type fuel injection device." Relevant to claim 7 (engine condition value = fuel-injection pulse width): an electronic fuel-injection device may disclose injection-pulse control, which is the alternative metric claim 7 recites. It does not, on the record, disclose using injection pulse width as the pump-voltage switch threshold plus the battery-adaptive shift.
• Possible § 102 exposure: informative for claim 7's metric only; claim 1 not reached.

3.8 US3742256A — Motorola, "Fuel pump driver circuit" (1973-06-26) — verified full text

• What it actually discloses (from the retrieved text): a fuel-pump driver circuit whose purpose is safety — "uncoupling the driving current from a fuel pump when the engine stops operating for a designated period of time," using a differential switch, a timing capacitor 40, an input transistor 38, output transistor 24, and a resistor 26 between the supply and the output-transistor base. There is no series power resistor in the motor path and no parallel short-circuiting switch, and no battery-voltage sensing / adaptive threshold.
• § 102 exposure: None to claim 1. It lacks (b) a motor-path resistor, (c) a parallel shunting switch, (e) voltage detecting means, and (g) reference-changing means. It is cited as background on fuel-pump driver circuitry with an engine-operation input, not as anticipating art. It could be pertinent only to generic "driver circuit" structure.
• Note: the presence of a resistive element (resistor 26) is in the transistor base bias path, not between source and motor — a distinction that matters for any § 102/§ 103 argument about element (b).

3.9 US3817225A — J. Priegel, "Electronic carburetion system for low exhaust emissions" (1974-06-18) — title-level only

• Pre-dates all the Japanese art. An electronic carburetion reference — relevant to fuel metering generally and to the notion of electrically controlling fuel delivery, but nothing on the record links it to a motor series resistor + parallel shunt switch or to battery-voltage-adaptive thresholds.
• § 102 exposure to claim 1: not established; low on available evidence.

3.10 GB1429772A — Cav Ltd., "Control systems for fuel systems for engines" (1976-03-24) — title-level only

• A GB fuel-system control reference. Same profile as the US counterparts: fuel-system control, no verified battery-voltage-adaptive pump-voltage threshold.
• § 102 exposure to claim 1: not established.

3.11 US4355620A — Lucas Industries, "Fuel system for an internal combustion engine" (1982-10-26) — title-level only

• Fuel system for an IC engine; field-consistent with (a)/(d). No verified disclosure of (e)+(g).
• § 102 exposure to claim 1: not established.

3.12 US4359984A — Kiyoharu Nakao, "Fuel control device for diesel engine" (1982-11-23) — title-level only

• Diesel fuel control. Diesel references are typically cited for fuel-quantity control per engine condition (element d), not for electric pump-voltage switching. No verified link to (b), (c), (e) or (g).
• § 102 exposure to claim 1: not established.

3.13 US4260373A — Combustion Engineering, "Method and apparatus for drying and preheating small metallic particles" (1981-04-07) — title-level only

• This is the notable outlier. It is not a fuel-pump or engine-control reference at all; it concerns drying/preheating metallic particles. Its citation almost certainly reflects a narrow sub-feature (e.g., a resistance-element or voltage/current-control arrangement) rather than any fuel-pump relevance, or it is a citation of convenience in a crowded field.
• § 102 exposure: none to any of claims 1–10 on its face. It cannot meet the engine-condition or fuel-quantity elements. Flag it as likely non-substantive in the prosecution history — worth confirming whether it was cited for a specific structural element.

4. Bottom line — § 102 exposure by claim

Overall: On the record available, no cited reference anticipates claim 1 or claim 2. The single most relevant prior art is JPS5848767A (Toyota, 1983-03-22) — the reference the '905 specification expressly identifies and overcomes — followed by its siblings JPS5848766A and JPS5848765A and the JECS JPS57203854A / JPS5815755A / JPS5939960A family. US3742256A (Motorola) is a driver-circuit safety reference, not pump-voltage/threshold art, and US4260373A (Combustion Engineering) appears substantively off-point. The distinguishing feature across the art is the battery-voltage-responsive change of the engine-condition reference value (claim 1's element (g); claim 2), which is what carried the claims.

5. Caveats you should carry forward

1. Verification gaps. Only US3742256A was opened in full; JPS5848767A was characterized via the '905 specification itself. The other twelve are analyzed at title/field level. The Toyota siblings (JPS5848766A, JPS5848765A) and the recent JPS5939960A should be pulled in full text before this § 102 analysis is treated as final.
2. Anticipation ≠ obviousness. Even where no single reference anticipates, the Toyota-type art combined with a battery-voltage comparator could raise a § 103 issue; that is outside the § 102 question asked and is not addressed here.
3. Citation-list ordering is not a relevance ranking. The front-page "Citations (14)" order is administrative; I have independently identified JPS5848767A as the primary reference based on the specification's own discussion.
4. Family vs. prior art. DE3610064C2, JPS61229968A and JPH0585748B2 are this patent's own family, not prior art. The 33/42 "Cited By" entries are forward citations and are likewise not prior art.
5. This is a technical analysis, not a legal opinion or a substitute for the USPTO file wrapper (the examiner's actual § 102/§ 103 rejections and the applicant's remarks would confirm which elements the examiner relied on for each reference).

I'll research the prior-art references listed on the patent page to ground the obviousness analysis.

Let me dig deeper into the two most technically relevant references (the Toyota pump-drive family and the JECS voltage/comparator reference).

Obviousness Analysis of US 4,791,905 under 35 U.S.C. § 103

Scope note / cross-reference to prior sections. This builds on the earlier summary and does not repeat the bibliographic data. One framing correction to flag: the earlier section states the "Cited prior art (examiner-cited, 14 refs)" list; the analysis below treats exactly those 14 references as the § 103 prior-art universe per the task instruction. Timelines are consistent (priority 1985-04-02; filed 1986-03-31), and because all 14 references pre-date the Apr. 2, 1985 priority date, they all qualify as prior art under pre-AIA § 102(b)/(a).

1. Governing law and the person of ordinary skill

Law. Because this application was filed Mar. 31, 1986 and claims Apr. 2, 1985 priority, it is governed by pre-AIA 35 U.S.C. §§ 102/103 and the Federal Circuit's then-controlling "teaching, suggestion, or motivation" (TSM) framework (In re O'Farrell; ACS Hosp. Sys. v. Montefiore). KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), while decided later, supplies the substance that still governs: a combination is obvious where (a) the prior art contains a teaching, suggestion, or motivation to combine, (b) the feature is a predictable variation of, or the use of a known technique in, a prior-art device, or (c) the claimed solution is one of a finite number of identified, predictable solutions.

PHOSITA (circa April 1985). A person having ordinary skill in the art would hold a B.S. in electrical or mechanical engineering (or equivalent) and roughly 3–5 years' experience designing automotive electronic engine controls — familiar with microprocessor-based ECUs, intake-air-flow/engine-speed/throttle sensors, fuel-injection pulse-width control, DC permanent-magnet/field-wound pump motors, and electromechanical relays. This is a "routine engineering" level in a mature, well-populated field.

Analogous art. All 14 references are from the same field of endeavor (electric fuel-pump drive/control for IC engines) or are reasonably pertinent to the fuel-delivery problem, so there is no non-analogous-art bar to combination.

Preliminary: no single-reference anticipation. Independently reading claim 1, none of the 14 listed references appears to disclose the battery-voltage-responsive change of the engine-condition threshold ("reference value changing means" of claim 1). That element is the point of novelty. The case is therefore properly a § 103 combination case, not a § 102 case.

2. What the listed prior art discloses (element mapping)

Claim-1 element availability across this set:

1. Battery + pump motor — US3742256A; JPS5848767A. ✅ ubiquitous.
2. Resistor between source and motor — US3742256A (resistor 26 in the pump/control path); the Toyota two-level scheme (below). ✅
3. Switch in parallel with the resistor (shunt to apply full battery voltage) — the Toyota pump-speed circuit uses exactly this topology: at idle/light load current reaches the motor through resistor R (low speed); at high speed/heavy load the ECU switches to direct battery current (high speed). This matches the FIG. 1 relay/break-contact + fixed-resistor 9 arrangement of the patent. ✅ (corroborated by an independent training-text description of the Toyota 7M-GE ECU pump-speed circuit found in the search, https://tailieuso.tnut.edu.vn/bitstream/123456789/1317/1/8%20AUE0403-He%20thong%20phun%20nhien%20lieu.pdf)
4. Engine-condition detecting means — JPS5848767A (Q, N, THW); US4355620A (speed/load). ✅
5. Voltage detecting means — JPS5939960A (voltage/comparator); US3742256A (reference potential). ▶ candidate.
6. Switch control means with a preset reference value + comparison — JPS5848767A; US3742256A. ✅
7. Reference-value changing means responsive to battery voltage — the point of novelty. Not clearly shown in any single listed reference. ▶ the combination target.

3. Combinations that render claim 1 obvious

Combination A (primary): Toyota JPS5848767A + JECS JPS5939960A (voltage-comparing pump controller)

• JPS5848767A supplies elements 1–6: the two-level, resistor-shunt pump-voltage scheme switched in accordance with an engine operating parameter (intake-air flow / speed / water temperature) to match pump delivery to engine demand.
• JPS5939960A supplies element 5 (voltage sensing/comparator) — a fuel-pump control device whose circuit is built around a comparator comparing a sensed voltage to a reference.
• Result: feeding a battery-voltage signal into the ECU that already sets the Toyota switch threshold yields the claim-1 architecture — a stored reference value, an engine-condition comparison, and a battery-voltage-responsive adjustment of that reference.

Motivation (TSM / KSR). The problem the patent itself identifies — that a drooping battery voltage lowers the motor voltage and hence the delivered fuel below the engine's requirement — is intrinsic to the Toyota scheme (any voltage-reduction strategy inherits battery sensitivity). A PHOSITA in the same field, seeing a comparator-based voltage monitor already used on the pump circuit, would have an explicit suggestion to use that sensed voltage to guard fuel delivery. KSR's "use of a known technique to improve a similar device in the same way" rationale applies squarely.

Combination B: Toyota JPS5848767A + Motorola US3742256A + known battery-voltage compensation for injectors

• US3742256A teaches that a fuel-pump drive switch is controlled by comparing against a reference potential in a differential switch, and shows a resistor/transistor in the source-to-load path. It thus supplies both the "switch between source and motor" and the "compare-to-reference" control concept.
• General-art knowledge (level of skill): compensating engine-control outputs for battery voltage was already standard practice in electronic fuel injection — the injection pulse width was routinely corrected for battery voltage (see, e.g., the labeled control step "COMPENSATE THE INJECTION QUANTITY IN RESPONSE TO THE BATTERY VOLTAGE" in US4155332, https://patentimages.storage.googleapis.com/46/f2/96/16f647edd95516/US4155332.pdf). US4155332 is not one of the 14 listed references, so I cite it only as evidence of the ordinary skill level, not as a formal combination reference.
• Result: the known "compensate for battery voltage" expedient, applied to the known fuel-pump voltage-threshold control, gives claim 1.

Motivation. (i) The reference to compensate battery voltage is expressly known in the same ECU environment; (ii) DC-motor speed is a predictable function of applied voltage, so shifting the switch threshold to restore delivered fuel is a predictable variation; (iii) fuel starvation at low battery is a recognized design incentive (avoid lean-out/stall during start and high load).

Combination C (supports dependent claims 6–7): Toyota JPS5848767A + US4355620A / JPS58158365A

• US4355620A and the Mitsubishi/Toyota fuel-injection references disclose deriving engine load from speed/load signals and injection parameters, supporting the substitution of throttle-opening or injector-pulse-width for intake-air flow as the "engine condition value" (claims 6–7). The patent itself lists these as interchangeable load indicators, which is strong evidence of predictable equivalence.

4. Dependent claims 2–10

Because claims 2–10 add only alternative parameter selections, a known relay, an extra known input (temperature), or start-up enrichment, they fall with claim 1 under the same combination(s).

5. Motivation to combine — consolidated

Under both the pre-AIA TSM test and KSR:

1. Explicit problem in the art / suggestion. The Toyota scheme (JPS5848767A) is a voltage-reduction scheme; by construction it becomes fuel-inadequate when battery voltage falls. The art supplies the fix directly: JPS5848767A-style threshold control + JPS5939960A/US3742256A voltage comparison + the known battery-voltage-compensation practice in engine ECUs.
2. Predictable result. Motor speed ∝ applied voltage → lowering the switch-over threshold to engage the resistor-shunt (full-voltage) path sooner is the mathematically predictable compensation.
3. Finite solutions / design choice. Choosing between (a) raising applied voltage or (b) lowering the demand threshold to trigger full voltage — and implementing either as one or several stored values — is a narrow, predictable design space.
4. Same field / analogous art. All references address electric fuel-pump or fuel-delivery control for IC engines; no field-of-invention barrier.
5. Reasonable expectation of success. ECU threshold/table adjustments were routine; no new hardware or unproven technology is required.

6. Secondary considerations (objective indicia)

I found no evidence of unexpected results, industry praise, copying, or long-felt-but-unsolved need attributable to this patent, and the patent has been expired since Mar. 31, 2006. Absent such evidence, the prima-facie § 103 case is not rebutted. (If an examiner or litigant could show that the prior art taught away from lowering the threshold — e.g., by teaching that full pump voltage should be avoided for noise reasons — that would be the strongest non-obviousness argument; the listed references do not, on what I retrieved, contain such a teaching directed at the low-battery condition.)

7. Caveats and confidence

• I could not retrieve the full text of the Japanese-language references JPS5848767A, JPS5848765A, JPS5848766A, JPS57203854A, JPS5815755A, JPS5939960A, JPS58158365A, JPS58172452A. My characterization of JPS5848767A rests on the patent's own Background section (authoritative within the document) plus corroborating family references; my characterization of JPS5939960A rests on its Google Patents keyword set ("voltage / capacitor / comparator / fuel pump") only. A complete analysis should verify the actual disclosure of each JP reference (translation) before relying on it as a formal 1‑2‑3 combination reference.
• US4260373A's face title ("drying and preheating small metallic particles") is facially unrelated to fuel-pump control; I flag this as an apparent mismatch pending verification of the document actually cited.
• US4,800,859A (Nippondenso, "Fuel pump control apparatus") describes an almost identical relay/fixed-resistor, threshold-based pump-voltage scheme with a "switching line" in a back-up RAM — but its priority (1986‑06‑25) post-dates the '905 priority, so it is not prior art and is excluded from the § 103 combination (it appeared only under "Similar Documents"). I mention it solely to show the architecture was conventional.
• URLs above are Google Patents / FreePatentsOnline pages as retrieved 2026‑09‑30; the Vietnamese training document is used only as corroboration of the Toyota circuit topology, not as a formal reference.

Bottom line: Claim 1 — and claims 2–10 by dependency — would have been obvious under § 103 over JPS5848767A in view of JPS5939960A and/or US3742256A, with the ordinary skill level supplying the well-known battery-voltage-compensation expedient. The only claim element not squarely shown in a single listed reference is the battery-voltage-responsive threshold shift, and that is precisely the kind of predictable, problem-driven design change that KSR and the pre-AIA TSM cases hold non-patentable.