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Run your analysis now →https://www.patsnap.com/resources/blog/rd-blog/nox-control-strategies-for-hydrogen-combustion-patent-landscape/ · Patsnap · data cut-off 2026-07-31 · downloaded from the live page
Patent Landscape · Hydrogen Combustion NOx ControlNOx control strategies for hydrogen combustion: the patents shaping engine design
- Filing concentration at the top: the leading assignee alone holds 222 records, and the top 5 combined account for 34.5% of all 1,229 records in scope.
- A clear peak has passed: filings peaked in 2018 at 92, and the 2021-to-2024 window shows a -61% decline (28 to 11) before the most recent, still-incomplete years.
- Fuel supply and engine control dominate: F02M and F02D classes cover 68.6% and 53.0% of records respectively, while exhaust aftertreatment (F01N) sits at just 26.2%.
1,229
Published Records
34%
Top-5 Share of All Records
-61%
Filing Growth 2021→2024
US
Leading Jurisdiction
Filing growth compares 2021 (28 records) with 2024 (11) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 1,229 records in scope (CR5), not by the ranked leaders only.
Published byPatsnap Research··7 min readSourced from Patsnap Eureka
Overview
What this landscape covers
Hydrogen combustion engines produce far less carbon output than hydrocarbon fuels, but the same high flame temperatures that make hydrogen attractive also drive up NOx formation. The patent activity captured here spans lean-burn combustion control, exhaust gas recirculation (EGR), water injection and aftertreatment approaches, filed against a search built around excess air ratio management, cold-start behaviour and transient emissions control. The dataset spans 2015 through the 2026 cut-off, with 1,229 records in scope.
Most of the activity sits upstream of the exhaust pipe: fuel metering and engine control claims outnumber aftertreatment claims by a wide margin, which tells a specific story about where automakers and suppliers believe the NOx problem is best solved — in-cylinder, not downstream.
Filing activity and technology composition, 2015–2026
Source: Patsnap Eureka. Assignee ranking and totals. Derived from a Patsnap search on NOx Control Strategies for Hydrogen Combustion covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
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The Numbers
Filing trends and technology composition
Two views of the same 1,229 records: how filing activity has moved year over year, and which engineering subsystems the claims concentrate on.
A 2018 peak followed by a real decline
Annual filings ran from 52 in 2017 to a peak of 92 in 2018. The 2021-to-2024 window, the most recent period that can be read as complete once publication lag is accounted for, shows an actual -61% drop (28 to 11). Years after 2024 are still filling in and should not be read as a continuing fall.
Fuel metering and engine control lead by a wide margin
F02M (fuel supply and carburettors) appears in 68.6% of records and F02D (engine control) in 53.0%, both well ahead of F01N (exhaust treatment) at 26.2%. Because records can carry multiple IPC classes, these shares add up to more than 100% of the 1,229 records — they describe where claims sit, not a partition of the dataset.
Shares are the percentage of the 1,229 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Source: Patsnap Eureka. Filing trend and technology composition. Derived from a Patsnap search on NOx Control Strategies for Hydrogen Combustion covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.
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Most-cited prior art and a representative filing
Representative Filing
US20050022511A1 — Exhaust gas recirculation control system
NISSAN MOTOR CO., LTD.
Filed by Nissan, this record describes an EGR control valve paired with an intake throttle valve positioned upstream of the EGR passage connection, with an excess air ratio control section that adjusts intake air quantity to suppress EGR ratio fluctuations during excess-air-ratio changes. The stated aim is to stabilise engine operating performance during the transitions that most often produce NOx spikes.Abstract trimmed for length; see the full record for complete claim language.
Highest-cited records in the dataset
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4271664A | Turbine engine with exhaust gas recirculation | 288 |
| 2 | US5154599A | Method for apparatus for combusting fuel in a combustion chamber | 220 |
| 3 | US6067800A | Control method for a variable geometry turbocharger in a diesel engine having exhaust gas recirculation | 204 |
| 4 | US5553575A | Lambda control by skip fire of unthrottled gas fueled engines | 203 |
| 5 | US4204401A | Turbine engine with exhaust gas recirculation | 196 |
| 6 | US5785030A | Exhaust gas recirculation in internal combustion engines | 170 |
| 7 | US6263672B1 | Turbocharger and EGR system | 153 |
| 8 | US6347619B1 | Exhaust gas recirculation system for a turbocharged engine | 152 |
| 9 | US6948475B1 | Optimized combustion control of an internal combustion engine equipped with exhaust gas recirculation | 118 |
| 10 | US6089019A | Turbocharger and EGR system | 110 |
Citation counts favour older filings inside any searched corpus — they are a signal of influence on later work, not of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
Source: Patsnap Eureka. Citation counts and representative records. Derived from a Patsnap search on NOx Control Strategies for Hydrogen Combustion covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
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What the data tells a filing strategy
Three patterns worth acting on before drafting new claims or scoping freedom-to-operate work in this space.
Concentration
34.5%
of 1,229 records held by top 5
Filing is concentrated but not locked up
The top 5 assignees combined hold 34.5% of all 1,229 records, and the leader alone accounts for 222. That leaves a majority of the field spread across a long tail of single- and few-filing entrants, which is where new entrants typically find room to build a position.
Based on the 100-company ranked assignee list.
Momentum
-61%
2021 to 2024 (28 → 11 records)
Filing activity has genuinely cooled since 2018
After peaking at 92 filings in 2018, activity fell to 28 by 2021 and to 11 by 2024 — a real, complete-year decline rather than an artefact of publication lag. Whether this reflects claim space maturing or R&D budgets shifting toward fuel-cell and battery-electric routes is not something the filing count alone answers.
2024 is the most recent year treated as complete.
Composition
26.2%
of records touch F01N aftertreatment
Aftertreatment is the minority strategy
Only 26.2% of records fall under F01N exhaust treatment, versus 68.6% under F02M fuel supply and 53.0% under F02D engine control. The dominant filing strategy across this dataset is preventing NOx formation in-cylinder rather than cleaning it up after combustion.
Shares sum above 100% because records can carry multiple IPC classes.
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Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to nox control strategies for hydrogen combustion, with the prior art for and against each one.
Source: Patsnap Eureka. Co-assignee relationships and derived observations. Derived from a Patsnap search on NOx Control Strategies for Hydrogen Combustion covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
Players
Who is filing, and where the activity has gone quiet
Automakers and heavy-vehicle manufacturers dominate the ranked assignee list, but recent-year momentum has cooled across nearly all of them at once.
Leader
222
records
A single assignee holds the largest share
The leading assignee's 222 records is nearly triple the fifth-place count of 41, a gap that marks this as a field with one dominant filer rather than a tightly clustered group at the top.
Counted in patent families / records.
Mid-field
27
records at 10th place
The gap narrows quickly after the leaders
By tenth place the count drops to 27, and the top 10 combined reach 47.4% of all 1,229 records. The remaining 90 ranked assignees split the rest, mostly automakers and component suppliers with single-digit filing counts.
Top 10 combined = 582 of 1,229 records.
Momentum
0
filings in the latest year for several leaders
Recent-year activity has gone quiet across the leader board
Several of the most active historical filers, including truck and passenger-vehicle manufacturers, show zero filings in the latest tracked year. Read this alongside the 18-month publication lag rather than as a sign these programmes have stopped.
Latest-year counts understate true filing activity due to publication lag.
Recent-year filing momentum by assignee
| Assignee | Recent year | YoY |
|---|---|---|
| Ford Global Technologies, LLC | 0 | — |
| GM Global Technology Operations LLC | 0 | — |
| Mazda Motor Corporation | 0 | — |
| Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation) | 0 | — |
| Volvo Truck Corporation | 0 | -100% |
| Nissan Motor Co., Ltd. | 0 | — |
| Hyundai Motor Company | 0 | — |
| Kia Corporation | 0 | — |
Source: Patsnap Eureka. Assignee-level momentum. Derived from a Patsnap search on NOx Control Strategies for Hydrogen Combustion covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
What's Next
Where to take this analysis
The trends and rankings above describe the field as a whole. The next step is usually narrower: checking a specific claim against this prior art, or scoping a filing position in a branch that is not yet crowded.
Run a freedom-to-operate check against the most-cited records
The highest-cited patents in this dataset, several dating to the 1980s and 1990s on turbine and EGR control, still anchor claim language used today. Any new EGR or lean-burn filing should be checked against them directly.
Open Eureka to search the full record setMap the under-claimed branches to a draft claim
Cold-start EGR stabilisation and water-injection metering show materially lighter filing density than the F02M/F02D core. That gap is a starting point for scoping a first claim, not a guarantee it stays open.
Explore white space in EurekaSource: Patsnap Eureka. Forward-looking reading of the same dataset. Derived from a Patsnap search on NOx Control Strategies for Hydrogen Combustion covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
FAQ
Common questions on hydrogen combustion NOx patents
One assignee leads the ranked list with 222 records, well ahead of the fifth-place holder at 41. The top 5 assignees combined account for 34.5% of all 1,229 records in scope, which means the field has one dominant filer rather than several evenly matched leaders. Beyond the top 10, which together hold 47.4% of records, filing activity spreads across a long tail of automakers and component suppliers with single-digit counts. Checking any freedom-to-operate question should start with the leader's portfolio, not the full ranked list.
No — filings peaked in 2018 at 92 and had fallen to 11 by 2024, a -61% drop from the 2021 figure of 28 over that three-year span. This is a real, complete-year decline rather than an artefact of recent data still filling in. Years after 2024 are not yet reliable for trend reading because publication typically lags filing by around 18 months, so the most recent one or two years will always look artificially low.
The evidence points strongly toward prevention. F02M (fuel supply) and F02D (engine control) classes cover 68.6% and 53.0% of the 1,229 records respectively, while F01N (exhaust treatment and aftertreatment) covers only 26.2%. That split suggests most patent activity targets excess air ratio, EGR and fuel metering strategies that stop NOx from forming in-cylinder, rather than downstream catalytic or filtration cleanup, though aftertreatment claims are still a meaningful minority.
EGR recirculates a portion of exhaust back into the intake to lower peak combustion temperature and reduce NOx formation, and it is a core mechanism referenced across this dataset, including in the most-cited prior art such as the turbine EGR patents from the 1980s. New EGR filings still need to clear a dense prior art base — several of the highest-cited records in this space, cited in the hundreds, cover EGR control fundamentals. Novel claim space tends to sit in how EGR is combined with cold-start behaviour or transient excess-air-ratio management, not in the base recirculation mechanism itself.
Cold-start EGR ratio stabilisation, water injection metering, and separation-based NOx capture under B01D all show noticeably lower filing density than the F02M and F02D core classes, with B01D covering only 3.0% of the 1,229 records. That does not mean these areas are legally open, but it does mean fewer competing claims to work around. Any drafting effort should still run a citation check against the field's most-cited prior art before assuming a branch is genuinely unclaimed.
Answers are grounded in the same dataset. Derived from a Patsnap search on NOx Control Strategies for Hydrogen Combustion covering 2015–2026, data cut-off 2026-07-31. Counts reflect published records only and shift as new filings publish.Run this in Eureka MCP
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company's registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.