CN115492662A - Valve lift system for engine braking - Google Patents

Valve lift system for engine braking Download PDF

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Publication number
CN115492662A
CN115492662A CN202110680268.4A CN202110680268A CN115492662A CN 115492662 A CN115492662 A CN 115492662A CN 202110680268 A CN202110680268 A CN 202110680268A CN 115492662 A CN115492662 A CN 115492662A
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CN
China
Prior art keywords
valve lift
exhaust
braking
engine
air inlet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202110680268.4A
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Chinese (zh)
Inventor
杨洲
朱汝杰
奚正
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shanghai Youshun Automobile Technology Co ltd
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Shanghai Youshun Automobile Technology Co ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shanghai Youshun Automobile Technology Co ltd filed Critical Shanghai Youshun Automobile Technology Co ltd
Priority to CN202110680268.4A priority Critical patent/CN115492662A/en
Priority to PCT/CN2022/082378 priority patent/WO2022218114A1/en
Publication of CN115492662A publication Critical patent/CN115492662A/en
Pending legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/06—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for braking
    • F01L13/065—Compression release engine retarders of the "Jacobs Manufacturing" type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0203—Variable control of intake and exhaust valves
    • F02D13/0207—Variable control of intake and exhaust valves changing valve lift or valve lift and timing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/04—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation using engine as brake
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D2013/0296—Changing the valve lift only

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Valve Device For Special Equipments (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)

Abstract

The invention provides a valve lift system for engine braking, wherein an exhaust valve lift comes from an integrated exhaust cam and consists of a braking exhaust valve lift and an enlarged exhaust valve lift; the intake valve lift comprises a braking intake valve lift which mainly occurs in the expansion stroke of the engine, is opened after a compression top dead center and is closed near an expansion bottom dead center. In the traditional integrated four-stroke braking, the lift of a braking air inlet valve (secondary air inlet) is increased, the ascending resistance and the exhaust flow of a cylinder piston in an exhaust stroke are increased, the exhaust back pressure and the rotating speed of a turbocharger are improved, the air inlet amount and the air inlet pressure are increased, and the braking power of an engine is improved.

Description

Valve lift system for engine braking
Technical Field
The invention relates to the field of machinery, in particular to the field of engine valve driving, and particularly relates to a valve lift system related to engine braking.
Background
Conventional valve actuation for vehicle engines is well known in the art and has been in use for over a hundred years. Conventional valve actuation utilizes conventional valve actuators (including conventional rocker arms) to control the motion of engine valves for conventional spark-ignition operation of the engine. But due to additional demands on engine fuel efficiency, exhaust emissions and engine braking, more and more engines employ variable valve actuation, including valve lift systems employing engine braking. Engine brakes have been widely used on commercial vehicle engines. The engine four-stroke brake is adopted in the market at present, namely, the compression release brake is only applied once at the end (near the compression top dead center) of the compression stroke in one cycle (four strokes: an air inlet stroke, a compression stroke, an expansion stroke and an exhaust stroke) of the engine. The two-stroke braking of the engine is to perform two times of compression release braking near a compression top dead center and expansion top dead center respectively in one cycle (four-stroke). So, theoretically, the power of the two-stroke brake should be twice as much as that of the four-stroke brake. However, the two-stroke braking requires the cylinder of the engine to be stopped, namely, the valve lift of the ignition of the engine is cancelled during the braking, so that the technical difficulty is high, the mechanism is complex, the cost is high, and no product exists so far.
One prior example of engine four-stroke braking is disclosed in U.S. patent No. 3,220,392 (1965) by Cummins (Cummins), the engine braking system made according to which was commercially successful. However, such engine braking systems are engine-mounted accessories. To install the engine brake, a gasket is added between the cylinder and the valve cover, thus additionally increasing the height, weight, and cost of the engine.
U.S. patent No. 5,609,133 (1997) discloses an integrated four-stroke brake with the brake mechanism integrated in the conventional (firing) exhaust rocker arm and the brake cam integrated with the conventional (firing) exhaust cam. The integrated exhaust cam comprises a brake boss and an enlarged conventional exhaust boss, the enlarged conventional exhaust boss is divided into an upper part and a lower part, the upper part is the conventional exhaust boss, and the lower part is as high as the brake boss. When the engine is ignited, the brake mechanism (motion loss mechanism) in the integrated exhaust rocker arm enables the motion of the brake boss to be lost, and only the motion of the conventional exhaust boss on the upper part is transmitted to two exhaust valves of the engine to generate the lift of the conventional (ignition) exhaust valve; when the engine brakes, the brake mechanism in the integrated exhaust rocker arm generates hydraulic connection, and transmits the motion of the brake boss to the two exhaust valves to generate the lift of the brake exhaust valve. This patent also discloses how to reset the increased conventional exhaust valve lift during braking. When braking, the two exhaust valves are opened, so that the braking load is large and the braking power is limited.
US 6,293,248 (2001) discloses an engine two-stroke braking arrangement and method. Four rocker arms are adopted: the cylinder deactivation exhaust rocker arm, the brake exhaust rocker arm, the cylinder deactivation air inlet rocker arm and the brake air inlet rocker arm drive the valve of the engine, the structure and the control are complex, and the cylinder deactivation exhaust rocker arm, the brake exhaust rocker arm, the cylinder deactivation air inlet rocker arm and the brake air inlet rocker arm cannot become products so far.
U.S. patent No. 8,936,006 (2015) discloses an engine two-stroke brake apparatus and method similar to that of the 2001 patent, again using four rocker arms: cylinder deactivation exhaust rocker arm, brake exhaust rocker arm, cylinder deactivation intake rocker arm and brake intake rocker arm. The cylinder deactivation mechanism is a motion loss mechanism integrated in a valve bridge of an engine, a braking exhaust rocker arm and a braking intake rocker arm are both hydraulically driven to open a valve (double valves are opened when the engine is ignited), the lift of the braking valve is influenced by the inclination of the valve bridge, and the reliability and the durability are difficult problems.
Disclosure of Invention
The invention provides an engine four-stroke braking system, which solves the problems that the cylinder of an engine needs to be stopped (the lift of an air inlet valve and an air exhaust valve of the ignition of the engine is completely cancelled during braking), the reliability and the durability are poor, the structure and the control are complex, the cost is high, the engine four-stroke braking system cannot become a product and the like in the conventional engine braking technology while the engine braking power is improved.
The invention provides an engine braking valve lift system which comprises an air inlet valve lift and an air outlet valve lift, wherein the air outlet valve lift comprises a braking air outlet valve lift and an ignition air outlet valve lift which are generated by an integrated air outlet cam, the air inlet valve lift comprises a braking air inlet valve lift and an ignition air inlet valve lift, and the braking air inlet valve lift mainly appears in the expansion stroke of an engine and is opened after an upper dead point is compressed and is closed near a lower dead point.
Furthermore, the integrated exhaust cam comprises a compression release brake boss and a heightened ignition exhaust boss, and the compression release brake boss generates a brake exhaust valve lift near a compression top dead center.
Furthermore, the heightened ignition exhaust boss consists of an upper part and a lower part, the upper part is a conventional ignition exhaust boss of the engine, and the lower part is as high as a compression release brake boss.
Furthermore, the braking exhaust valve lift comprises a reset exhaust valve lift, the reset exhaust valve lift comprises a front part and a rear part, the front part is from a heightened ignition exhaust boss, and the rear part is a conventional ignition exhaust valve lift obtained after resetting.
Furthermore, the integrated exhaust cam further comprises an exhaust recirculation braking boss, and the exhaust recirculation braking boss generates a braking exhaust valve lift near an intake bottom dead center.
Further, the intake valve lift is from a dedicated braking intake cam, and the dedicated braking intake cam generates the braking intake valve lift in the expansion stroke.
Furthermore, the intake valve lift is from an integrated intake cam, the integrated intake cam comprises a braking intake boss and a heightened ignition intake boss, the braking intake boss generates a braking intake valve lift in an expansion stroke, and the braking intake valve lift is smaller than a conventional ignition intake valve lift.
Furthermore, the heightened ignition air inlet boss consists of an upper part and a lower part, the upper part is a conventional air inlet boss of the engine, and the lower part is as high as the braking air inlet boss.
Compared with the prior art, the invention has positive and obvious effect. The engine four-stroke braking system and the method of the invention adopt the fixed chain type rocker arm, transfer load through a solid connection mode, particularly reserve the conventional air inlet/outlet rocker arm and the conventional air inlet/outlet valve lift generated by the conventional air inlet/outlet rocker arm, increase the braking air inlet valve lift (the second air inlet valve lift) and the air inlet of the engine cylinder only on the basis of the conventional engine four-stroke braking, improve the exhaust resistance during the exhaust stroke, increase the braking power, and have the advantages of simple and reliable structure, easy manufacture and assembly, cost reduction, wide application and the like.
Drawings
FIG. 1 is a schematic diagram of intake and exhaust valve lift during normal operation (ignition) of an engine.
FIG. 2 is a schematic diagram of intake and exhaust valve lift during integrated engine four-stroke braking.
FIG. 3 is a schematic diagram of intake and exhaust valve lift for four-stroke engine braking in accordance with the present invention.
FIG. 4 is a schematic illustration of intake and exhaust valve lift for a four-stroke engine brake according to another embodiment of the present invention.
Detailed Description
FIG. 1 is a schematic diagram of intake and exhaust valve lift during engine ignition in the prior art. Valve motion for conventional ignition of an engine is common knowledge. The exhaust cam of the engine drives a conventional (firing) exhaust rocker arm, which opens the exhaust valve on the exhaust stroke of the engine, discharging the combusted exhaust gases. The valve lift 20 of the exhaust valve (thin solid line in fig. 1) is opened before the expansion (power) bottom dead center of the engine and closed after the exhaust top dead center of the engine (closing point 23). An intake cam of the engine drives a conventional (ignition) intake rocker arm, and an intake valve is opened in an intake stroke of the engine to suck fresh air. The valve lift 30 (thick solid line in fig. 1) of the intake valve is opened before the exhaust top dead center of the engine and closed after the intake bottom dead center of the engine. It is particularly worth noting that the function of the engine is mainly that the ignition produces positive power. Whether engine two-stroke braking or engine four-stroke braking, it is necessary to ensure that the intake and exhaust valve lifts 20 and 30 shown in fig. 1 are provided when the engine is ignited.
Fig. 2 is a schematic diagram of intake and exhaust valve lifts during four-stroke braking of an integrated engine in the prior art. The valve motion of the integrated engine four-stroke brake is also well known, and the generation method is many, and at present, the most widely used one is to adopt an integrated rocker arm brake (another is an integrated valve bridge brake), a brake mechanism is integrated in a conventional (ignition) exhaust rocker arm, and a brake cam is integrated with a conventional (ignition) exhaust cam. The integrated exhaust cam comprises a brake boss and an enlarged conventional exhaust boss, the enlarged conventional exhaust boss is divided into an upper part and a lower part, the upper part is the conventional exhaust boss, and the lower part is as high as the brake boss. When the engine is ignited, a brake mechanism (a motion loss mechanism) in the integrated exhaust rocker arm enables the motion of a brake boss (the lift of the lower part of a dot-dash line 212 in fig. 2) to be lost, and only the motion of the conventional exhaust boss of the upper part is transmitted to two exhaust valves of the engine to generate the lift 20 of the conventional (ignition) exhaust valve (a thin dotted line in fig. 2 is equal to the lift of the upper part of the dot-dash line 212); during engine braking, the brake mechanism in the integrated exhaust rocker arm generates an additional link, the motion of the brake boss is transmitted to the two exhaust valves, and a brake exhaust valve lift (comprising a compression release lift 201 and an exhaust gas recirculation lift 204) and an increased exhaust valve lift 22 are generated. The heightened exhaust valve lift 22 is not only increased in height from the normal (firing) exhaust valve lift 20, but also has its closing point 231 retarded from the closing point 23 of the normal (firing) exhaust valve lift 20. A compression release lift 201, which is to be used to release high-pressure gas (air) compressed in the cylinder during the compression stroke of the engine, occurs near the compression top dead center of the engine (opening before the compression top dead center and closing after the compression top dead center); exhaust gas recirculation 204 occurs near intake bottom dead center of the engine (open before intake bottom dead center, closed after intake bottom dead center) so that the gas in the exhaust pipe is back charged into the cylinder near the intake valve closing, increasing braking power.
FIG. 3 is a schematic diagram of intake and exhaust valve lift for four-stroke engine braking in accordance with the present invention. Unlike the prior art integrated engine four-stroke braking shown in fig. 2, the braking intake valve lift 302 (dashed bold line in fig. 3), also called the second intake valve lift (the intake valve lift 30 generated during the intake stroke is the first intake valve lift), is added during the expansion (power) stroke of the engine, and is opened after compression top dead center and closed near expansion bottom dead center. The braking intake valve lift (second intake valve lift) 302 occurs mainly in the expansion (power) stroke with respect to the ignition intake valve lift 30, which occurs mainly in the intake stroke, and is smaller (lower) than the first intake valve lift 30 at the time of ignition.
The invention increases the lift 302 of the brake air inlet valve during the expansion (power expansion) stroke of the engine, introduces fresh air into the cylinder of the engine, and can generate the following three effects and improve the brake power of the engine:
(1) Resistance increase of cylinder piston in exhaust stroke of engine (increasing pump pressure work)
(2) The exhaust volume of the engine is increased, the exhaust back pressure and the rotating speed of the turbocharger are improved
(3) The intake air amount and the intake pressure are increased.
The three effects form a virtuous cycle, which is beneficial to increasing the braking power.
FIG. 4 is a schematic diagram of intake and exhaust valve lift for describing another engine four-stroke braking of the present invention. Different from the situation shown in fig. 3, the integrated brake adds a reset function, when the engine is braked, the heightened exhaust valve lift 22 is reset to the conventional (ignition) exhaust valve lift 20, the heightened exhaust valve lift 22 is arranged before the reset point 202, the conventional (ignition) exhaust valve lift is arranged after the reset point 202, the closing point of the valve lift is advanced from 231 to 23, and the lift of the valve at the exhaust top dead center is reduced, so that the possibility that the valve collides with a cylinder piston is eliminated, the brake power is increased, and the brake exhaust temperature is reduced.
Note that engine two-stroke braking requires the intake and exhaust valve lifts 20 and 30 to be cancelled at ignition, that is, braking requires the conversion of a conventional rocker arm into a deactivating rocker arm that cancels valve motion. As the cylinder deactivation rocker arm has the problems of high technical difficulty, complex mechanism, increased cost, reliability, reduced durability and the like, the cylinder deactivation rocker arm has no product in the field of commercial vehicle engines.
The embodiment of the application does not use the cylinder deactivation exhaust rocker arm or the cylinder deactivation intake rocker arm (the traditional conventional rocker arm is reserved), and only adds the braking intake valve lift 302 on the basis of the integrated engine four-stroke braking in the prior art.
The above description should not be taken as limiting the scope of the invention, but as being a representative of the invention in which many other variations are possible. For example, the engine braking system shown here may be not only a rocker arm brake, but also a valve bridge brake; the engine not only can be used for an overhead cam engine, but also can be used for a push rod/push pipe type engine; not only can open a single valve, but also can open double valves. The brake mechanism may be driven by other driving means such as hydraulic pressure, in addition to the fixed chain type. In addition, similar to the exhaust valve lift, the intake valve lift can also come from an integrated intake cam, the integrated intake cam comprises a braking intake boss and a heightened ignition intake boss, the heightened ignition intake boss consists of an upper part and a lower part, the upper part is a conventional intake boss of the engine, and the lower part is as high as the braking intake boss; the braking air inlet boss generates a braking air inlet valve lift in an expansion stroke, and the braking air inlet valve lift is smaller than a conventional ignition air inlet valve lift. In summary, the intake and exhaust valve lift profiles may be varied.

Claims (8)

1. The engine braking valve lift system comprises an intake valve lift and an exhaust valve lift, wherein the exhaust valve lift comprises a braking exhaust valve lift and an ignition exhaust valve lift which are generated by an integrated exhaust cam, the intake valve lift comprises a braking intake valve lift and an ignition intake valve lift, and the braking intake valve lift mainly appears in the expansion stroke of an engine, is opened after a compression top dead center and is closed near an expansion bottom dead center.
2. The engine brake valve lift system of claim 1, wherein: the integrated exhaust cam comprises a compression release brake boss and a heightened ignition exhaust boss, and the compression release brake boss generates a brake exhaust valve lift near a compression top dead center.
3. The engine brake valve lift system of claim 2, wherein: the heightened ignition exhaust boss consists of an upper part and a lower part, the upper part is a conventional ignition exhaust boss of the engine, and the lower part is as high as a compression release brake boss.
4. The engine brake valve lift system of claim 2, wherein: the braking exhaust valve lift comprises a reset exhaust valve lift, the reset exhaust valve lift comprises a front part and a rear part, the front part is from a heightened ignition exhaust boss, and the rear part is a conventional ignition exhaust valve lift obtained after resetting.
5. The engine brake valve lift system of claim 2, wherein: the integrated exhaust cam further comprises an exhaust recirculation braking boss, and the exhaust recirculation braking boss generates a braking exhaust valve lift near an air inlet bottom dead center.
6. The engine brake valve lift system of claim 1, wherein: the intake valve lift is from a dedicated braking intake cam that generates a braking intake valve lift in the expansion stroke.
7. The engine brake valve lift system of claim 1, wherein: the air inlet valve lift range is from an integrated air inlet cam, the integrated air inlet cam comprises a braking air inlet boss and a heightened ignition air inlet boss, the braking air inlet boss generates a braking air inlet valve lift range in an expansion stroke, and the braking air inlet valve lift range is smaller than a conventional ignition air inlet valve lift range.
8. The engine brake valve lift system of claim 7, wherein: the heightened ignition air inlet boss consists of an upper part and a lower part, wherein the upper part is a conventional air inlet boss of the engine, and the lower part has the same height as the braking air inlet boss.
CN202110680268.4A 2021-04-14 2021-06-18 Valve lift system for engine braking Pending CN115492662A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN202110680268.4A CN115492662A (en) 2021-06-18 2021-06-18 Valve lift system for engine braking
PCT/CN2022/082378 WO2022218114A1 (en) 2021-04-14 2022-03-23 Engine four-stroke braking system, method, and engine braking valve lift system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110680268.4A CN115492662A (en) 2021-06-18 2021-06-18 Valve lift system for engine braking

Publications (1)

Publication Number Publication Date
CN115492662A true CN115492662A (en) 2022-12-20

Family

ID=84464525

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110680268.4A Pending CN115492662A (en) 2021-04-14 2021-06-18 Valve lift system for engine braking

Country Status (1)

Country Link
CN (1) CN115492662A (en)

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