Honing and Superfinishing of Bores Patents: Leaders & Trends 2026
- Concentrated at the top. The five leading assignees hold 60.4% of all 53 records in scope, and the top ten hold 79.2% — a field where a small group of piston-ring and OEM filers has staked out most of the claim space.
- Filing activity has cooled. Filings peaked in 2019 at 6 records and had fallen back to 1 by the 2022 midpoint, suggesting the core honing-process claims were largely staked out earlier in the window.
- Grinding and engine-cylinder classes dominate. B24B (grinding & polishing) appears on 71.7% of records and F02F (engine cylinders & pistons) on 52.8%, while alloy, coating and powder-metallurgy classes each sit under 14% — a visible gap between process claims and materials claims.
What this landscape covers
Honing and superfinishing of bores covers the processes used to bring a cylinder bore or liner to its final internal surface geometry — cross-hatch angle, plateau roughness, oil-retention pit structure — after boring or rough machining. This scope combines process claims filed under B24B (grinding and polishing) with the cylinder-liner and engine-block hardware claims filed under F02F, plus adjacent alloy, coating and powder-metallurgy filings that describe the liner material itself rather than the finishing step.
The 53 records in scope span 2015 through the partial 2026 filing year, with the most recent year understated because publication typically lags filing by around 18 months. Reading the trend and the assignee ranking together shows a field where a handful of piston-ring and vehicle OEM filers established a dense core of honing-process and cylinder-liner claims earlier in the window, with filing volume declining since the 2019 peak.
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Filing trend and technology composition
Two views of the same 53 records: how filing volume has moved year over year, and which IPC subclasses carry the claims.
Filing trend, 2017–2026
Filings rose to a peak of 6 records in 2019, then fell back — 2022, the midpoint of the window, shows only 1 record. The 2026 figure is partial because the dataset cuts off mid-year and recent filings have not yet published.
IPC subclass distribution
B24B (grinding & polishing) and F02F (engine cylinders & pistons) account for the large majority of records at 71.7% and 52.8% respectively. Alloys (C22C), coatings (C23C), turning/boring (B23B), general metalworking (B23P), powder metallurgy (B22F) and casting (B22D) each sit under 14%, and because a record can carry more than one class these shares do not sum to 100%.
Shares are the percentage of the 53 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Honing and Superfinishing of Bores with Eureka
This page is one run against one query. Ask Eureka your own question about honing and superfinishing of bores and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records and a representative filing
US20220025829A1 — Cylinder liner and manufacturing method for same
A cylinder liner formed of flaky graphite cast iron with a nitrided inner layer and a cross-hatched plateau-honed bore surface, specified by a ten-point average roughness (Rz, JIS B0601:1982) of 4.0 μm or less and an average pit area ratio of 8% or less.Filed by TPR CO., LTD., published 2022-01-27.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | DE4438550A1 | Verfahren zur Herstellung einer in ein Kurbelgehäuse einer Hubkolbenmaschine eingegossenen Zylinderlaufbüchse… | 47 |
| 2 | US5331775A | Honing process with rough honing tool and finish honing tool on same rotating head | 30 |
| 3 | EP0586791A1 | Honing process | 21 |
| 4 | US20050130560A1 | Method of Honing Bores | 18 |
| 5 | US5643054A | Machine part with improved surface texture for rolling contact and/or sliding contact | 17 |
| 6 | US6096143A | Cylinder liner of a hypereutectic aluminum/silicon alloy for use in a crankcase of a reciprocating piston eng… | 15 |
| 7 | CN103433836A | 气缸套内孔珩磨端面定位外抱锁紧装置 | 8 |
| 8 | CN105619271A | 一种切割砂轮内孔加工方法 | 7 |
| 9 | KR102546980B1 | Method for machining inner diameter of clinder liner | 5 |
| 10 | US20170120348A1 | Engine bore milling process | 5 |
Citation counts reflect an older-skews-higher bias inherent to any searched corpus — older honing-process fundamentals accumulate citations that newer, narrower claims have not yet had time to earn.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for filing strategy
Three read-throughs from the trend, the citation table and the class distribution.
A dense core, then a long tail
The leading assignee holds 10 of the 53 records, and the top five together hold 60.4%. Below the top ten the ranking thins into single- and double-filing entrants, which is where freedom-to-operate searches need the most care since these filers' claims are less predictable from the leaders' portfolios alone.
Activity has cooled since 2019
Filing volume peaked at 6 records in 2019 and had fallen to 1 by the 2022 midpoint, with none of the leading assignees showing activity in the latest year. That pattern is consistent with a technology whose core process claims were staked out earlier, not one still being actively contested.
Process claims outweigh materials claims
Grinding-and-polishing process claims and engine-cylinder hardware claims dominate the class distribution, while alloy, coating and powder-metallurgy classes each appear on fewer than 14% of records. That gap points to comparatively open claim space around liner material composition and surface treatment rather than the honing process itself.
Foundational claims sit with older filings
The most-cited records in this set date to the 1990s and early 2000s and cover core honing-process and cylinder-liner-casting methods. New entrants should expect these older filings to define the prior art baseline for cross-hatch angle and rough/finish honing tool claims, even where the citing record itself is decades newer.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to honing and superfinishing of bores, with the prior art for and against each one.
Who holds the claim space
Piston-ring specialists and vehicle OEMs make up most of the leading filers, with two identified co-assignee pairs suggesting joint filing between related corporate entities.
A single filer well ahead of the field
The top-ranked assignee holds 10 of the 53 records in scope, nearly double the fifth-place filer's count of 2. That gap between first and fifth place is the clearest signal of concentration in this dataset.
Related entities file together
Two co-assignee pairs appear in the data, the strongest linking two affiliated piston-ring entities across 9 shared records. A second, weaker pair links two affiliated vehicle OEMs across 2 records — a reminder to check corporate family trees before assuming two names represent independent art.
China and the US lead receiving offices
China and the United States are the two largest receiving offices at 15 and 13 filings respectively, ahead of Europe, Japan, India and the United Kingdom. That spread indicates the technology is being protected across multiple major manufacturing and automotive markets rather than concentrated in one jurisdiction.
| Assignee | Recent year | YoY |
|---|---|---|
| TPR Co., Ltd. | 0 | — |
| TPR Industry Co., Ltd. | 0 | — |
| Mercedes-Benz Group AG | 0 | — |
| Toyota Motor Corporation | 0 | — |
| Mahle International GmbH | 0 | — |
| Zhengzhou Abrasives Grinding Research Institute Co., Ltd. | 0 | — |
| Kia Corporation | 0 | — |
| Felsomat GmbH & Co. KG | 0 | — |
Where to take this
The dataset points to a mature, concentrated core of honing-process claims and a thinner layer of materials and surface-treatment claims around it.
Map the top assignee's portfolio in detail
With one filer holding 10 of 53 records, a full portfolio pull for that assignee will show which specific claim elements — cross-hatch angle ranges, plateau roughness thresholds, tool configurations — are already locked up before drafting new claims nearby.
Explore assignee portfolios in EurekaCheck the co-assignee pairs before treating names as independent
Two identified co-assignee pairs mean at least some of the ranked assignees are corporately related. Confirming these relationships changes how concentrated the field actually looks.
Run a corporate family check in EurekaProbe the materials and coating gap directly
Alloy, coating and powder-metallurgy classes each sit under 14% of records against a process-heavy core. A targeted search on liner material composition and surface treatment claims may surface less-crowded filing space.
Search adjacent IPC classes in EurekaCommon questions about this landscape
The dataset ranks 30 companies by number of records, and it is concentrated at the top: the leading assignee holds 10 of the 53 records in scope, and the top five combined hold 60.4% of all records. Piston-ring specialists and vehicle OEMs make up most of the leading filers, with two identified co-assignee pairs linking affiliated corporate entities. Below the top ten, which together hold 79.2% of records, the ranking thins quickly into single- and double-filing entrants.
Not currently. Filings peaked at 6 records in 2019 and had fallen to 1 by the 2022 midpoint, with the leading assignees showing no recorded activity in the most recent year. Because publication typically lags filing by around 18 months, the last one to two years in any trend chart will understate true filing activity, but the multi-year decline from the 2019 peak predates that lag effect and looks like a genuine slowdown.
US20220025829A1, filed by TPR CO., LTD. and published in 2022, claims a cylinder liner made of flaky graphite cast iron with a nitrided inner layer and a cross-hatched, plateau-honed bore surface, specified by a ten-point average roughness (Rz per JIS B0601:1982) of 4.0 micrometres or less and an average pit area ratio of 8% or less. It is a hardware and surface-specification claim on the finished liner rather than a claim on the honing process itself. Anyone designing a liner with a nitrided layer and similar roughness and pit-ratio parameters should review this record's specific numeric thresholds before finalising a design.
The class distribution shows a heavy concentration in grinding-and-polishing process claims (71.7% of 53 records) and engine-cylinder hardware claims (52.8%), while alloy, coating, turning/boring, general metalworking, powder-metallurgy and casting classes each appear on fewer than 14% of records. That gap suggests comparatively open claim space around liner material composition, powder-metallurgy substrates and surface coating treatments, rather than in the honing process itself where the core methods are already densely claimed.
China and the United States are the largest receiving offices in this dataset, with 15 and 13 filings respectively, ahead of Europe (EPO) at 6, Japan at 5, India at 4 and the United Kingdom at 3. This spread indicates filers are protecting bore honing and cylinder-liner technology across the major manufacturing and automotive markets rather than concentrating filings in a single jurisdiction, which is consistent with an internationally distributed supply chain for engine components.
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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.