CN216841862U - Valve lift system for engine braking - Google Patents
Valve lift system for engine braking Download PDFInfo
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- CN216841862U CN216841862U CN202121362308.2U CN202121362308U CN216841862U CN 216841862 U CN216841862 U CN 216841862U CN 202121362308 U CN202121362308 U CN 202121362308U CN 216841862 U CN216841862 U CN 216841862U
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Abstract
The utility model provides an engine braking valve lift system, wherein the exhaust valve lift is 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 the compression top dead center and is closed near the 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 the 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
Technical Field
The utility model relates to the field of machinary, especially, relate to the valve lift system of engine braking in the engine valve actuation field.
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. However, 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 four-stroke engine brake is currently used in the market, namely, only once compression release brake is carried out at the end of the compression stroke (near the compression top dead center) in one cycle of the engine (four strokes: intake stroke, compression stroke, expansion stroke and exhaust stroke). The two-stroke brake of the engine is to do two times of compression release brake near the compression top dead center and the expansion top dead center respectively in one cycle (four-stroke). So, theoretically, the power of the two-stroke brake should be twice 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 four-stroke engine braking is disclosed in U.S. patent No. US 3,220,392 (1965) by Cummins (Cummins), according to which an engine braking system is made with commercial success. 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.
United states patent US 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 apparatus and method for two-stroke engine braking. 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.
US 8,936,006 (2015) discloses a two-stroke engine braking device and method similar to the 2001 US, 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.
SUMMERY OF THE UTILITY MODEL
The utility model provides an engine four-stroke braking system when improving engine braking power, solves and needs the engine to stop jar among the current engine braking technique (cancel advance, exhaust valve lift that the engine was igniteed completely during the braking), reliability and durability poor, structure and control complicacy, with high costs and can't become product scheduling problem.
The utility model provides an engine braking valve lift system, including the valve lift of admitting air and exhaust valve lift, the exhaust valve lift include braking exhaust valve lift and ignition exhaust valve lift that produce by integrated form exhaust cam, the valve lift of admitting air including the braking valve lift of admitting air and the valve lift of admitting air of igniteing, the valve lift of admitting air shown mainly appears in the expansion stroke of engine, opens after the compression top dead center, close near the expansion bottom dead center.
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 gas recirculation braking boss, and the exhaust gas 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 utility model has positive and obvious effect. The utility model discloses an engine four-stroke braking system and method adopt solid chain formula rocking arm, pass through solid connected mode transmission load, especially remain conventional advance/exhaust rocking arm and advance/exhaust valve lift by its conventional that produces, only on the basis of conventional engine four-stroke braking, increase braking air inlet valve lift (the second time air inlet valve lift) and engine cylinder and admit air, improve the exhaust resistance during the exhaust stroke, increase braking power, have simple structure reliably, the manufacturing assembly is easy, reduce cost and use advantages such as extensive.
Drawings
FIG. 1 is a schematic diagram of intake and exhaust valve lift during normal operation (firing) of an engine.
FIG. 2 is a schematic diagram of intake and exhaust valve lift during integrated four-stroke engine braking.
Fig. 3 is a schematic diagram of intake and exhaust valve lift of the four-stroke engine brake according to the present invention.
Fig. 4 is a schematic diagram of intake and exhaust valve lift for four-stroke braking of another engine according to 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 application) 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 present at the time of engine ignition.
FIG. 2 is a schematic diagram of intake and exhaust valve lift during four-stroke braking of an integrated engine in the prior art. The valve motion of integrated engine four-stroke braking is also well known and its generation method is many, and at present, the most widely used one is to use an integrated rocker arm brake (another is an integrated valve bridge brake), the brake mechanism is integrated in a conventional (ignition) exhaust rocker arm, and the 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 opened before compression top dead center and closed after compression top dead center, for releasing high-pressure gas (air) compressed in the cylinder during the compression stroke of the engine, occurs near the engine compression top dead center; exhaust gas recirculation 204 occurs near engine intake bottom dead center (open before intake bottom dead center, closed after intake bottom dead center) so that the gas in the exhaust pipe refluxes the cylinder near intake valve closure, increasing braking power.
Fig. 3 is a schematic diagram of intake and exhaust valve lift of the four-stroke engine brake according to the present invention. Unlike the prior art integrated engine four-stroke brake shown in fig. 2, the brake 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 increased 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 utility model discloses increase braking air inlet valve lift 302 during the expansion (acting) stroke of engine, introduce the cylinder of engine with fresh air, can produce following three kinds of effects, improve the brake power of 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 illustrating intake and exhaust valve lift for four-stroke braking of another engine according to the present invention. Different from the situation shown in fig. 3, the integrated brake adds a reset function, the heightened exhaust valve lift 22 is reset to the conventional (ignition) exhaust valve lift 20 during engine braking, 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 also 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, reduced reliability and durability and the like, the cylinder deactivation rocker arm product is not available 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 rather as representing a specific exemplification of the invention, from which many other evolutions 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 valve lift system for engine braking is characterized by comprising 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 occurs in the expansion stroke of an engine, is opened after a compression top dead center, and is closed near the expansion bottom dead center.
2. The engine braking 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 braking 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 braking 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 braking 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 intake bottom dead center.
6. The engine braking 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 braking 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 braking 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.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121362308.2U CN216841862U (en) | 2021-06-18 | 2021-06-18 | Valve lift system for engine braking |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121362308.2U CN216841862U (en) | 2021-06-18 | 2021-06-18 | Valve lift system for engine braking |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN216841862U true CN216841862U (en) | 2022-06-28 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202121362308.2U Active CN216841862U (en) | 2021-06-18 | 2021-06-18 | Valve lift system for engine braking |
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| Country | Link |
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| CN (1) | CN216841862U (en) |
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2021
- 2021-06-18 CN CN202121362308.2U patent/CN216841862U/en active Active
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