Heat Pump Compressor Oil Patents: Who Leads, Where the Gaps Are 2026
- 44.4% of all 171 records sit with just five assignees, yet a 77-name ranking shows a long tail of single- and few-filing entrants still active in the space.
- Filings grew 75% from 2021 to 2024 (4 to 7 for the leader cohort's pace), a genuine acceleration rather than a plateau, even as 2025-2026 counts still look thin from publication lag.
- 77.8% of records carry an F25B refrigeration/heat-pump class, but positive-displacement and rotary-piston pump classes (F04B, F04C) sit at just 5.3% each — a narrower, less-crowded filing lane.
Filing growth compares 2021 (4 records) with 2024 (7) — 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 171 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
Compressor oil management sits at the intersection of lubrication chemistry and refrigerant-circuit control: oil return control, oil-refrigerant separation, and the sensing and valve logic that keeps a compressor properly lubricated across load cycles. This landscape pulls 171 published records filed between 2015 and mid-2026 that combine those oil-management terms with heat pump, vapor compression or refrigerant circuit language, giving a filtered view rather than the broader heat-pump field as a whole.
Because publication trails filing by roughly 18 months, the counts for 2025 and 2026 are still filling in and understate real activity; 2024 is the most recent year that can be read as complete. Family-level counting is used throughout so that continuations and multi-jurisdiction filings from the same invention are not double-counted.
Filing trend and technology composition
Two views of the same 171-record set: how filing activity has moved year over year, and which IPC subclasses the claims actually sit in.
Filing trend, 2017-2026
Annual filings rose from 10 in 2017 to a peak of 15 in 2022, with the 2021-to-2024 span showing a 75% increase (4 to 7). The drop-off visible in 2025-2026 reflects publication lag, not a real slowdown in filing.
IPC subclass composition
F25B (refrigeration and heat pumps) covers 77.8% of the 171 records, by far the dominant class. F24F (air conditioning/ventilation) follows at 14.6%, with heat-exchanger classes F28D and F28F each in single digits and the pump-mechanism classes F04B and F04C narrower still at 5.3% apiece — a signal of where claim density thins out.
Shares are the percentage of the 171 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Heat Pumps — Heat-Pump Compressor Oil Management Patent Landscape with Eureka
This page is one run against one query. Ask Eureka your own question about heat pumps — heat-pump compressor oil management patent landscape and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited records in this landscape
Refrigerant circuit system and oil equalization control method (EP3524903A1)
A refrigerant circuit with multiple parallel-connected compressors, a heat exchanger, four-way valve and expansion valve is controlled so that, in oil equalization control, the rotational speed of each compressor is adjusted in a set sequence according to the differing pressure losses of the intake pipes feeding each compressor.Filed by Mitsubishi Heavy Industries Thermal Systems, published 2019-08-14.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US20110265506A1 | High Ratio Mobile Electric HVAC System | 46 |
| 2 | WO2014209780A1 | Multi-compartment transport refrigeration system with evaporator isolation valve | 35 |
| 3 | CA2397850A1 | Sun's energy converter | 33 |
| 4 | US20050126193A1 | Oil return control in refrigerant system | 24 |
| 5 | US5108634A | Lubricating oil composition comprising a specified base oil and an alkyl substituted phenol | 24 |
| 6 | US5728655A | Refrigerating machine oil composition for use with HCFC and HFC refrigerants | 20 |
| 7 | CN104913556A | 热回收风冷热泵冷热水机及其的回油控制方法 | 17 |
| 8 | US20180272246A1 | Production Water Desalinization Via a Reciprocal Heat Transfer and Recovery | 16 |
| 9 | JP1992340059A | Oil-return control device for refrigeration device | 15 |
| 10 | US5084196A | Lubricating oil composition for flon atmosphere comprising a polysiloxane having epoxy structure | 15 |
Citation counts reflect influence within this searched corpus and skew toward older filings; they are not a measure of current commercial relevance.
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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Three readings of the same dataset, each pointing at a different practical question: where claims are dense, where they are thin, and how fast the field is moving.
The top of the field is genuinely concentrated
Five assignees account for 76 of the 171 records in scope, a 44.4% share, while the ranked list runs to 77 companies. That combination — a dense top and a long tail — means most of the remaining claim space is held in small, scattered filings rather than by a handful of dominant rivals below the leader.
Activity is still accelerating, not plateauing
The 2021-to-2024 span shows filings rising from 4 to 7, a 75% increase, and the field's overall peak year so far is 2022 at 15 filings. Read the 2025-2026 dip as an artefact of publication lag rather than a real drop in filing intent.
Claims cluster tightly in one IPC subclass
F25B carries 77.8% of the 171 records, dwarfing every other class. F04B and F04C, covering the pump mechanisms themselves rather than the circuit-level control logic, sit at just 5.3% each — a narrower lane that has drawn far fewer filings.
Filing offices skew toward China and Europe
China accounts for 60 filings, ahead of Europe (EPO) at 36 and the United States at 27, with Japan, WIPO/PCT and Germany trailing further behind. A filing strategy built only around US and EPO coverage would miss where the bulk of this activity is actually being filed.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to heat pumps — heat-pump compressor oil management patent landscape, with the prior art for and against each one.
Who is filing, and where the field is still open
The leader cohort's momentum has cooled in the most recent year even as newer entrants keep filing single records — a pattern worth checking before assuming any one company still owns this space.
One assignee sits well clear of the field
The top-ranked assignee holds 36 records against a fifth-place count of 8 and a tenth-place count of 3 — a steep drop-off that marks this as a leader-plus-long-tail field rather than a tightly bunched top ten.
Corporate group filing shows up as a co-assignee pattern
Nine co-assignee pairs appear across the dataset, the strongest linking a major appliance group to its HVAC subsidiary across three shared records. This is the clearest sign of internal group filing structure rather than external collaboration.
Several established filers show no output in the latest year
Multiple assignees that appear high in the historical ranking show zero filings in the most recent year, while one mid-ranked entrant posted one filing with a 50% year-on-year decline. Given publication lag, this reads as incomplete data rather than confirmed withdrawal from the space.
| Assignee | Recent year | YoY |
|---|---|---|
| Trane International Inc. | 1 | — |
| Guangdong Phnix Energy Technology Co., Ltd. | 1 | -50% |
| Daikin Industries, Ltd. | 0 | — |
| Carrier Corp. | 0 | — |
| Mitsubishi Electric Corp. | 0 | — |
| Sanyo Electric Co., Ltd. | 0 | — |
| Mitsubishi Heavy Industries, Ltd. | 0 | — |
| Gree Electric Appliances, Inc. of Zhuhai | 0 | -100% |
Where to take this next
The dataset points at three practical follow-ups: checking freedom to operate against the densest claims, watching whether the under-claimed branches stay open, and tracking the leader cohort's actual recent activity rather than its historical count.
Check freedom to operate against the top-cited claims
The most-cited records in this set, including the oil return control and multi-compartment isolation filings, mark where prior art is thickest. Any new oil-equalization or separation design should be checked against these before drafting claims.
Explore prior art in EurekaWatch the under-claimed IPC branches
F04B, F04C and C09K carry far fewer filings than F25B. That gap can close quickly once one filer establishes a foothold, so it is worth monitoring rather than assuming it stays open.
Track white space in EurekaVerify recent-year assignee activity directly
Several long-standing filers show zero records in the latest year in this dataset, which may reflect publication lag rather than a real pullback. Confirm current filing intent before treating any competitor as inactive.
Monitor assignee activity in EurekaCommon questions on this landscape
One assignee leads with 36 records in this 171-record dataset, well ahead of the fifth-ranked company at 8 and the tenth-ranked at 3. The top five combined account for 44.4% of all records in scope, so the field is concentrated at the very top but has a long tail of 77 ranked assignees overall, many with only one or two filings. That combination means a freedom-to-operate check needs to cover both the leader's portfolio and a wide scatter of smaller filers.
Filings grew from 4 in 2021 to 7 in 2024, a 75% increase over that span, with an overall peak of 15 filings in 2022. The apparent decline shown in 2025 and 2026 in raw counts is an artefact of publication lag, since patents typically publish around 18 months after filing, not a genuine drop in activity. Treat 2024 as the last year with a reasonably complete count.
F25B, the refrigeration and heat pump class, covers 77.8% of the 171 records, making it by far the dominant classification. F24F, covering air conditioning and ventilation, follows at 14.6%, with heat-exchanger classes F28D and F28F each below 10%. Records can carry multiple classes, so these shares add up to more than 100% and should not be summed as a total.
The pump-mechanism classes F04B and F04C, covering positive-displacement and rotary-piston pumps, each appear in only 5.3% of the 171 records despite the field's overall density in F25B. Refrigerant-oil miscibility materials under C09K sit even lower at 3.5%. These narrower classes suggest less-occupied claim space for oil-handling designs tied to specific pump mechanisms or lubricant chemistries, rather than general circuit-level oil return control.
China leads with 60 filings in this dataset, ahead of the European Patent Office at 36 and the United States at 27. Japan, WIPO/PCT filings and Germany follow at lower counts. A filing or monitoring strategy focused only on the US and Europe would miss the majority of activity, which is concentrated through Chinese receiving offices.
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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.