阅读说明：本技术 发动机缸内制动系统及与其配套的液压挺柱 (Engine cylinder inner braking system and hydraulic tappet matched with same ) 是由 王立峰 王秀强 王孟晓 吴龙龙 李克旭 苏明涛 从田增 吴鹏超 衣金水 王昊天 于 2020-06-16 设计创作，主要内容包括：本发明公开了一种压缩释放式发动机缸内制动系统及与其配套的液压挺柱,液压挺柱包括挺柱体、柱塞和在液压腔内的机油压力消除后使柱塞处于回缩状态的弹性装置,柱塞的外周面与挺柱体的内周面滑动密封配合,柱塞开设有与液压腔相通的泄压通道,泄压通道内设置有泄压阀芯和泄压弹簧。缸内制动系统的供油油路连接液控开关阀的控制油口,当供油油路与发动机机油油路连通时,液控开关阀关闭液压挺柱与外界油路的连通,当供油油路与减压油路连通时,液控开关阀连通液压挺柱与外界油路的连通。该缸内制动系统与上述液压挺柱配套使用,使发动机既可以发挥缸内制动的特长又具有液压挺柱所带来的消除由气门间隙引起的噪声和冲击的优势。(The invention discloses a compression release type engine cylinder inner braking system and a hydraulic tappet matched with the compression release type engine cylinder inner braking system. The oil supply oil path of the in-cylinder braking system is connected with the control oil port of the hydraulic control switch valve, when the oil supply oil path is communicated with the engine oil path of the engine, the hydraulic control switch valve closes the communication between the hydraulic tappet and the external oil path, and when the oil supply oil path is communicated with the pressure reduction oil path, the hydraulic control switch valve is communicated with the communication between the hydraulic tappet and the external oil path. The cylinder braking system is matched with the hydraulic tappet for use, so that the engine can exert the characteristic of cylinder braking and has the advantage of eliminating noise and impact caused by valve clearance and brought by the hydraulic tappet.)

1. A hydraulic tappet comprising:

the oil pump comprises a tappet body and a plunger, wherein one end of the tappet body is provided with an oil inlet, the other end of the tappet body is open, the plunger extends into the tappet body from the open end of the tappet body and forms a hydraulic cavity with the tappet body, and a one-way valve capable of communicating an external oil path with the hydraulic cavity under the action of engine oil pressure is arranged on the inner side of the oil inlet;

the outer peripheral surface of the plunger piston is in sliding sealing fit with the inner peripheral surface of the tappet body;

the plunger is provided with a pressure relief channel communicated with the hydraulic cavity, the pressure relief channel is provided with a sealing conical surface, a pressure relief valve core and a pressure relief spring are arranged in the pressure relief channel, the pressure relief valve core is pushed away from the sealing conical surface by the pressure relief spring to form an oil leakage gap when not acted by the valve opening pressure, and the pressure relief valve core overcomes the elasticity of the pressure relief spring and contacts with the sealing conical surface to realize the sealing of the hydraulic cavity when acted by the valve opening pressure; it is characterized in that the preparation method is characterized in that,

a pressure relief valve seat is fixedly arranged on the plunger in the hydraulic cavity and positioned above the pressure relief valve core, and a through hole is formed in the pressure relief valve seat and is communicated with the hydraulic cavity and the pressure relief channel;

the hydraulic tappet is provided with an elastic device which enables the plunger to be in a retraction state after the engine oil pressure in the hydraulic cavity is eliminated.

2. The hydraulic tappet of claim 1, wherein the resilient device includes an extension spring disposed between the relief valve seat and the check valve, the extension spring disposed within the hydraulic chamber.

3. The hydraulic tappet according to claim 2, wherein the check valve comprises a check valve core, a limiting spring and a check valve seat, a sealing conical surface is arranged on the inner side of the oil inlet, the limiting spring is arranged in the check valve seat, the check valve seat is fixedly mounted on a tappet body of the hydraulic cavity, the limiting spring enables the check valve core to abut against the sealing conical surface of the oil inlet, and one end of the extension spring is fixedly connected to the check valve seat while the other end of the extension spring is fixedly connected to the pressure relief valve seat.

4. The hydraulic lifter of claim 1, wherein the resilient device includes an extension spring coupled between the lifter body and the plunger, the extension spring disposed outside of the hydraulic chamber.

5. The hydraulic lifter of claim 1, wherein the resilient means comprises a compression spring having one end abutting against the projecting end of the plunger and the other end abutting against a member displaceable relative to the plunger, the compression spring being disposed outside the hydraulic chamber.

6. The hydraulic tappet of claim 1, wherein an oil inlet of the tappet body is connected with an engine oil path controlled by a switching valve.

7. The hydraulic lifter of claim 6, wherein the on-off valve is a solenoid on-off valve.

8. The hydraulic tappet of claim 6, wherein the switching valve is a pilot operated switching valve.

9. A compression-release in-cylinder engine braking system includes

The oil supply device is connected with an engine oil path of the engine and comprises an electromagnetic directional valve, an oil supply path and a pressure reducing path, the pressure reducing path is connected with a pressure reducing path, an overflow pressure retaining valve is arranged in the pressure reducing path, and the oil supply path is selectively communicated with the engine oil path of the engine and the pressure reducing path through the electromagnetic directional valve; it is characterized in that the preparation method is characterized in that,

the oil supply path is connected with a control oil port of a hydraulic control switch valve, an oil inlet of the hydraulic control switch valve is connected with an engine oil path of the engine, an oil outlet of the hydraulic control switch valve is connected with an oil inlet of a tappet body of the hydraulic tappet according to any one of claims 1 to 5, when the oil supply path is communicated with the engine oil path, the hydraulic control switch valve closes the connection between the hydraulic tappet and an external oil path, and when the oil supply path is communicated with the pressure reduction oil path, the hydraulic control switch valve opens the connection between the hydraulic tappet and the external oil path.

10. The compression-release engine in-cylinder brake system according to claim 9, wherein the hydraulic control switch valve includes a valve body, the valve body is respectively provided with the control oil port, the oil outlet and the oil inlet, a valve element and a return spring are arranged in the valve body and fixed by a valve cover, and the valve element is provided with a communication oil path for communicating the oil inlet and the oil outlet.

Technical Field

The invention relates to the technical field of in-cylinder braking of engines, in particular to a compression release type in-cylinder braking system of an engine, and further relates to a hydraulic tappet in an engine valve mechanism.

Background

In the valve actuating mechanism of the engine, a hydraulic tappet can be arranged on any transmission part between a cam and a valve, is used for transmitting the thrust of a camshaft to a push rod (or a valve rod) and bearing the lateral force applied when the camshaft rotates, and can automatically compensate valve clearance, eliminate relevant parts for adjusting the valve clearance and eliminate noise and impact caused by the valve clearance relative to a mechanical tappet.

In the cylinder braking technology of the engine, the compression release type braking technology is the best technology for the braking performance of the engine at present, and the basic principle is as follows: when the engine is dragged backwards, the piston compresses the gas in the cylinder to generate braking power in the process of ascending the compression stroke piston. Before the compression top dead center, the compression release type brake device drives the exhaust valve to open a certain opening degree, compressed high-temperature and high-pressure charging in the cylinder is discharged, at the moment, the pressure in the cylinder is rapidly reduced, after a certain crank angle, the exhaust valve is closed again, the piston moves downwards, and as the charging in the cylinder is greatly reduced, the working of the charging in the cylinder on the piston is also greatly reduced, and the counter braking power of the compression charging in the cylinder on the piston is reduced or eliminated.

Chinese patent application CN111197510A discloses an in-cylinder brake system for an engine, which includes an oil cylinder device, an oil pumping device and an oil supply device applied to a valve train of the engine, wherein all cylinders of the engine share one oil supply device; the oil supply device comprises an electromagnetic directional valve, an oil supply oil path, a pressure reducing oil path and a pressure relief oil path, the engine oil pressure of the engine before pressure reduction is P1, and the engine oil pressure of the engine after pressure reduction is P2; each cylinder of the engine is respectively provided with an oil cylinder device and an oil pumping device, the oil cylinder device is communicated with the oil pumping device through a pressure transmission oil path, the pressure transmission oil path is communicated with an oil supply oil path through a low-pressure relief valve, and the high end of an oil path system is provided with a relief valve; when braking is carried out in the cylinder, the air release valve is closed, the electromagnetic directional valve is electrified, engine oil with the pressure of P1 is provided for the pressure transmission oil path through the oil supply oil path, and the piston of the oil cylinder device and the plunger of the oil pumping device extend out; when the cam abuts against and pushes the oil pumping device, the engine oil pressure in the oil pumping device rises, the oil pumping device pumps high-pressure engine oil with the pressure of P to the oil cylinder device through the pressure transmission oil path, the low-pressure relief valve is closed, and the oil cylinder device pushes the rocker arm to open the valve, so that in-cylinder braking is realized; when the brake is not in the cylinder, the air release valve is opened, the electromagnetic directional valve is powered off, the oil with the pressure of P2 is provided for the pressure transmission oil path through the oil supply oil path, the low-pressure relief valve is in an opening state at the moment of power failure of the electromagnetic directional valve, the oil pressure in the pressure transmission oil path is relieved through the low-pressure relief valve and is reduced to P2, the oil cylinder device and the oil pumping device return respectively, the cam is separated from the oil pumping device, the engine is in a normal operation state, the oil or air in the pressure transmission oil path is continuously discharged through the air release valve, and the problem that the power transmission effect is seriously influenced due to the fact that air enters the pressure transmission oil. Because each cylinder of the engine is respectively provided with the oil cylinder device and the oil pumping device which are connected through the pressure transmission oil path, the pressure transmission oil path is communicated with the oil supply oil path of the oil supply device through the low-pressure relief valve, the brake/non-brake conversion of all cylinders of the whole engine can be realized only by controlling the on/off of the electromagnetic directional valve, the requirement on a control circuit is low, the work is stable and reliable, and the failure rate is low; and the structure is simple, the arrangement is flexible and convenient, the engine cylinder number is not limited, the number of the cylinders is even or odd, the application performance is good, and the application is wider.

When the in-cylinder brake system is applied to a dual-valve actuating mechanism, as shown in fig. 1, a rocker arm drives two valves (two intake valves or two exhaust valves) through a valve bridge at the same time, but when the in-cylinder brake system is applied to an engine cylinder, the in-cylinder brake mechanism drives one valve to open alone, and if a traditional hydraulic tappet, such as the hydraulic tappet disclosed in the chinese patent application No. cn202010460474.x, is configured on the valve mechanism, the following problems may occur:

when the brake is in the cylinder, the brake mechanism drives one of the valves to open, the valve bridge moves downwards, but the rocker arm does not move relatively, at the moment, the hydraulic tappet extends to automatically compensate the gap formed by the descending of the valve bridge, and after the brake is finished in the cylinder, the valve is closed, and at the moment, because the hydraulic tappet is not shortened in time, the valve cannot be completely closed, the valve cannot be sealed in the subsequent working process, compressed gas in the cylinder leaks, and the brake effect in the cylinder is reduced or even fails.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present invention provides a hydraulic tappet suitable for in-cylinder braking, and as a concept, the present invention also provides a compression-release engine in-cylinder braking system, which can be used in combination with the hydraulic tappet, so that the engine can not only exert the characteristics of in-cylinder braking, but also have the advantages of eliminating noise and impact caused by valve lash, which are brought by the hydraulic tappet.

In order to solve the first technical problem, the invention adopts the technical scheme that:

a hydraulic tappet comprising: the oil pump comprises a tappet body and a plunger, wherein one end of the tappet body is provided with an oil inlet, the other end of the tappet body is open, the plunger extends into the tappet body from the open end of the tappet body and forms a hydraulic cavity with the tappet body, and a one-way valve capable of communicating an external oil path with the hydraulic cavity under the action of engine oil pressure is arranged on the inner side of the oil inlet; the outer peripheral surface of the plunger piston is in sliding sealing fit with the inner peripheral surface of the tappet body; the plunger is provided with a pressure relief channel communicated with the hydraulic cavity, the pressure relief channel is provided with a sealing conical surface, a pressure relief valve core and a pressure relief spring are arranged in the pressure relief channel, the pressure relief valve core is pushed away from the sealing conical surface by the pressure relief spring to form an oil leakage gap when not acted by the valve opening pressure, and the pressure relief valve core overcomes the elasticity of the pressure relief spring and contacts with the sealing conical surface to realize the sealing of the hydraulic cavity when acted by the valve opening pressure; a pressure relief valve seat is fixedly arranged on the plunger in the hydraulic cavity and positioned above the pressure relief valve core, and a through hole is formed in the pressure relief valve seat and is communicated with the hydraulic cavity and the pressure relief channel; the hydraulic tappet is provided with an elastic device which enables the plunger to be in a retraction state after the engine oil pressure in the hydraulic cavity is eliminated.

The elastic device comprises an extension spring arranged between the pressure relief valve seat and the one-way valve, and the extension spring is arranged in the hydraulic cavity.

The check valve comprises a check valve core, a limiting spring and a check valve seat, a sealing conical surface is arranged on the inner side of the oil inlet, the limiting spring is arranged in the check valve seat, the check valve seat is fixedly arranged on a tappet body of the hydraulic cavity, the limiting spring enables the check valve core to abut against the sealing conical surface of the oil inlet, and one end of an extension spring is fixedly connected to the other end of the check valve seat and fixedly connected to the pressure relief valve seat.

The elastic device comprises an extension spring connected between the tappet body and the plunger, and the extension spring is arranged outside the hydraulic cavity.

The elastic device comprises a compression spring, one end of the compression spring abuts against the extending end of the plunger, the other end of the compression spring abuts against a component capable of generating relative displacement with the plunger, and the compression spring is arranged outside the hydraulic cavity.

In order to solve the second technical problem, the invention adopts the technical scheme that:

a compression release type engine in-cylinder brake system comprises an oil supply device connected with an engine oil way of an engine, wherein the oil supply device comprises an electromagnetic directional valve, an oil supply way and a pressure reduction way; the oil supply path is connected with a control oil port of a hydraulic control switch valve, an oil inlet of the hydraulic control switch valve is connected with the engine oil path, an oil outlet of the hydraulic control switch valve is connected with an oil inlet of a tappet body of the hydraulic tappet, when the oil supply path is communicated with the engine oil path, the hydraulic control switch valve closes the connection between the hydraulic tappet and an external oil path, and when the oil supply path is communicated with the pressure reduction oil path, the hydraulic control switch valve opens the connection between the hydraulic tappet and the external oil path.

The hydraulic control switch valve comprises a valve body, the valve body is provided with the control oil port, the oil outlet and the oil inlet respectively, a valve core and a return spring are arranged in the valve body and are fixed by a valve cover in a sealing mode, and the valve core is provided with a communicating oil way for communicating the oil inlet and the oil outlet.

After the technical scheme is adopted, the invention achieves the technical effects that:

the invention relates to an in-cylinder brake system of an engine, which is a system for realizing braking by controlling engine oil.

When the engine works in a non-cylinder braking mode, the electromagnetic directional valve of the oil supply device is powered off, the oil supply oil path is connected with the low-pressure oil path through the electromagnetic directional valve, at the moment, the hydraulic control switch valve is communicated with the hydraulic tappet and an external oil path, if the cam does not work, the hydraulic plunger is not acted by the opening pressure of the valve, the pressure relief valve core is jacked away from the sealing conical surface of the pressure relief channel by the pressure relief spring, engine oil enters the hydraulic cavity through the oil inlet and the one-way valve and slowly leaks through the gap between the pressure relief valve core and the sealing conical surface, at the moment, under the action of the oil pressure of the engine oil, the tappet body and the plunger of the hydraulic tappet are respectively (directly or indirectly) close to the; if the cam works, the engine oil pressure of the hydraulic cavity rises, the pressure relief valve core overcomes the elastic force of the pressure relief spring, the hydraulic cavity becomes a closed cavity, no matter how the engine speed changes, the relative position of the tappet body and the plunger cannot change, and the performance of the engine is ensured. Because the oil leakage gap can be formed between the pressure relief valve core and the sealing conical surface, when the cam does not work, engine oil of an engine can enter the hydraulic cavity through the oil inlet and the one-way valve and slowly leaks through the oil leakage gap, so that the working length of the hydraulic tappet can be extended and shortened, and the thermal expansion gap of a valve mechanism part can be automatically compensated. When the cam works, the oil leakage gap is closed, the working length of the hydraulic tappet is hardly changed (only slightly shortened in the initial stage of the cam work, and the shortening amount is controllable), and therefore the valve opening stroke is more accurate.

When the engine works in an in-cylinder braking mode, the electromagnetic directional valve is electrified, the oil supply oil path is communicated with an engine oil path (high-pressure oil path) of the engine through the electromagnetic directional valve, the hydraulic control switch valve closes the connection between the hydraulic tappet and an external oil path under the action of high-pressure oil, and the hydraulic tappet does not extend under the action of the elastic device, so that the valve clearance is not automatically compensated, and the braking effect is not influenced. The engine cylinder braking system is matched with the hydraulic tappet for use, so that the engine can not only exert the characteristic of cylinder braking, but also has the advantage of eliminating noise and impact caused by valve clearance and brought by the hydraulic tappet.

The hydraulic tappet can also be matched with in-cylinder brake systems with other structural forms for use, and at the moment, the on/off mode of engine oil can be realized by adopting an electromagnetic switch valve or other modes. When the hydraulic tappet is in a non-cylinder braking state, engine oil of the engine is communicated with the hydraulic cavity, the pressure of the engine oil overcomes the elasticity of the elastic device, and the hydraulic tappet extends and has the same working principle as that of the traditional hydraulic tappet. When the engine is in a braking state in the cylinder, the engine oil circuit is disconnected, and the hydraulic tappet is shortened under the elastic action of the elastic device, so that the valve clearance is not automatically compensated. In the braking state in the cylinder, as long as the connection between the engine oil path of the engine and the oil inlet of the hydraulic tappet is controlled to be disconnected, the hydraulic tappet can not extend any more (the shortening amount can be ensured by mechanical limitation and cannot be too short), so that the braking effect is ensured.

Drawings

FIG. 1 is a schematic diagram of a known dual valve train;

FIG. 2 is a cross-sectional view of a first configuration of a hydraulic tappet of the present invention;

FIG. 3 is a cross-sectional view of a second configuration of a hydraulic tappet of the present invention;

FIG. 4 is a cross-sectional view of a third configuration of the hydraulic tappet of the present invention;

FIG. 5 is a schematic structural diagram of an embodiment of a compression-release engine in-cylinder braking system used in conjunction with a hydraulic tappet of the present invention;

in the figure:

10-cam, 20-push rod, 30-rocker arm, 40-hydraulic tappet, 50-valve spring, 60-valve, 61-valve bridge, 70-orifice, 80-electromagnetic reversing valve, 90-one-way valve, 100-overflow pressure retaining valve, 120-oil pan and F-cylinder internal braking force application direction;

l0-engine oil circuit, La-oil supply circuit, Lb-pressure reducing circuit, Lc-pressure reducing circuit;

40B-hydraulic tappet, 41B-plunger, 411B-oil drainage hole, 42B-tappet body, 421B-oil inlet, 43B-hydraulic cavity, 44B-one-way valve, 441B-one-way valve seat, 442B-one-way valve core, 443B-limit spring, 45B 1-extension spring, 45B 2-extension spring, 45B 3-compression spring, 46B-sealing conical surface, 47B-pressure relief valve core, 48B-pressure relief spring, 49B-pressure relief valve seat and 491B-through hole;

110-a hydraulic control switch valve, 1101-a valve body, 1102-a control oil port, 1103-an oil outlet, 1104-an oil inlet, 1105-a valve core, 1106-a communication oil way, 1107-a return spring and 1108-a valve cover.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

As shown in fig. 5, a compression-release in-cylinder brake system for an engine is a system that uses control oil to perform braking. The oil supply device comprises an electromagnetic directional valve 80, an oil supply line La and a pressure reducing oil line Lb, wherein the oil supply device is connected with the engine oil line L0 and comprises the electromagnetic directional valve 80, the oil supply line La and the pressure reducing oil line Lb, the pressure reducing oil line Lb is connected with a pressure reducing oil line Lc, and the oil supply line La is selectively communicated with the engine oil line L0 and the pressure reducing oil line Lb through the electromagnetic directional valve 80. The electromagnetic directional valve 80 is preferably a two-position three-way electromagnetic directional valve, and a check valve 90 is further arranged in front of the electromagnetic directional valve 80, and the check valve 90 can further protect the engine oil passage L0 from being impacted by the returned high-pressure engine oil. An overflow pressure retaining valve 100 is arranged in the pressure relief oil passage Lc. For convenience of description, the oil pressure of the engine oil passage L0 before decompression is defined as P1, P1 as high pressure, the oil pressure of the engine after decompression is defined as P2, P2 as low pressure, and the set pressure of the overflow pressure-retaining valve 100 is P2 or slightly higher than P2. The detailed structure and working principle of the in-cylinder brake system of the engine are referred to the chinese patent application CN111197510A, which is not described herein.

As shown in fig. 5, the oil supply path La is connected to the control oil port 1102 of the pilot-controlled switch valve 110, the oil inlet 1104 of the pilot-controlled switch valve 110 is connected to the engine oil path P0, the oil outlet 1103 of the pilot-controlled switch valve is connected to the hydraulic tappet 40B, when the oil supply path La is communicated with the engine oil path L0, the pilot-controlled switch valve 110 closes the external oil inlet channel of the hydraulic tappet 40B under the action of the high-pressure oil P1, and when the oil supply path La is communicated with the pressure reducing path Lb, the pilot-controlled switch valve 110 opens the external oil inlet channel of the hydraulic tappet 40B.

As shown in fig. 5, the hydraulic control switch valve 110 has a specific structure that a control oil port 1102, an oil outlet 1103 and an oil inlet 1104 are respectively formed in a valve body 1101, a valve spool 1105 and a return spring 1107 are arranged in the valve body 1101 and fixed by a valve cover 1108, and the valve spool 1105 is provided with a communication oil passage 1106. Fig. 3 shows a state when the hydraulic tappet 40B is communicated with an external oil inlet channel, at this time, the system is in a non-cylinder braking state, the electromagnetic directional valve 80 is de-energized, the oil supply path La is communicated with the pressure reduction path Lb, the pressure of the control oil port 1102 is low pressure P2, the return spring 1107 pushes the valve core 1105 leftwards, and the communication oil path 1106 is in a position of being simultaneously communicated with the oil inlet 1104 and the oil outlet 1103. When the system is in an in-cylinder braking state, the electromagnetic directional valve 80 is electrified, the oil supply path La is communicated with the engine oil path L0, the pressure of the control oil port 1102 is high pressure P1, the high pressure P1 overcomes the elastic force of the return spring 1107 to push the valve core 1105 towards the right, the oil inlet 1104 cannot be communicated with the oil outlet 1103 through the communication oil path 1106, and therefore the connection between the engine oil path L0 and the hydraulic tappet oil path is cut off.

Fig. 2 shows a first specific structure of the hydraulic lifter 40B. An oil inlet 421B is formed in one end of the tappet body 42B, the other end of the tappet body is open, the plunger 41B extends from the open end of the tappet body 42B and forms a hydraulic cavity 43B with the tappet body 42B, the oil inlet 421B is communicated with an engine oil path (not shown) arranged on the rocker arm 30, a check valve 44B is arranged on the inner side of the oil inlet 421B, and the engine oil path and the hydraulic cavity 43B can be communicated through the check valve 44B under the action of engine oil pressure. The one-way valve 44B has a specific structure including a one-way valve spool 442B, a limit spring 443B and a one-way valve seat 441B, wherein a sealing conical surface is disposed on an inner side of the oil inlet 421B, the limit spring 443B is disposed in the one-way valve seat 441B, the one-way valve seat 441B is provided with an oil through hole and is fixedly mounted on a tappet body 42B of the hydraulic cavity, and the limit spring 443B abuts against the one-way valve spool 442B against the sealing conical surface of the oil inlet 421. Check valve spool 442B is preferably a valve ball, such as a steel ball.

A pressure relief valve seat 49B is fixedly arranged on the plunger 41B in the hydraulic cavity 43B, the pressure relief valve seat 49B is positioned above the pressure relief valve core 47B, a through hole is formed in the pressure relief valve seat 49B, the through hole is communicated with the hydraulic cavity 43B and a pressure relief channel 411B, and an extension spring 45B1 which enables the plunger 41B to be in a retraction state after the engine oil pressure in the hydraulic cavity 43B is eliminated is arranged between the pressure relief valve seat 49B and the check valve 44B. In the in-cylinder braking state, the plunger 41B is not extended by the tensile force of the tension spring 45B1 when the engine oil pressure is cut off, and the closing of the valve is not affected after the in-cylinder braking is finished, so that the braking effect is not affected. In this embodiment, one end of the tension spring 45B is fixedly connected to the one-way valve seat 441B, and the other end thereof is fixedly connected to the relief valve seat 49B.

The outer peripheral surface of the plunger 41B is slidably fitted to the inner peripheral surface of the tappet body 42B, and the fitting clearance ensures smooth sliding and sealing of the plunger, so that oil does not leak therefrom. The plunger 41B is opened with a relief passage 411B communicating with the hydraulic pressure chamber 43B, and the relief passage 411B communicates with the oil pan 70. The pressure relief channel 411B is provided with a sealing conical surface 46B, a pressure relief valve core 47B and a pressure relief spring 48B are arranged in the pressure relief channel 411B, and preferably, the pressure relief valve core 47B comprises a valve ball, such as a steel ball. The elasticity of the pressure relief spring 48B should ensure that the pressure relief valve element 47B can still be disengaged from the sealing conical surface 46B to form an oil leakage gap when the engine oil of the engine reaches a maximum value, and the pressure relief valve element 47B can rapidly seal the sealing conical surface 46B when the cam working hydraulic chamber 43B forms a high pressure. The relief spring 48B is provided in a relief passage 411B communicating with the small end of the sealing tapered surface 46B, and abuts between the relief valve element 47B and a step surface of the relief passage. When the valve opening pressure is not acted, the pressure relief valve core 47B is ejected away from the sealing conical surface 46B by the pressure relief spring 48B; when acted upon by the valve opening pressure, the relief valve spool 47B overcomes the elastic force of the relief spring 48B and contacts the sealing tapered surface 46B to seal the hydraulic chamber 43B.

By combining the working principle, the technical effects obtained by the invention are as follows:

when the engine works in a non-cylinder braking mode, the electromagnetic directional valve 80 of the oil supply device is powered off, the oil supply line La is communicated with the low-pressure oil line Lb through the electromagnetic directional valve 80, at the moment, the hydraulic control switch valve 110 is connected with the hydraulic tappet 40B and an external oil line, if the cam 10 does not work, the hydraulic tappet 40B is not acted by the valve opening pressure, the pressure relief valve core 47B is jacked away from the sealing conical surface 46B of the pressure relief channel by the pressure relief spring 48B, engine oil enters the hydraulic cavity 43B through the oil inlet 421B and the one-way valve 44B and slowly leaks through a gap between the pressure relief valve core 47B and the sealing conical surface 46B, at the moment, the tappet 42B and the plunger 41B of the hydraulic tappet 40B are respectively (directly or indirectly) close to the cam 10 and the valve 60 under the action of the oil pressure of the engine, and; if the cam works, the engine oil pressure of the hydraulic cavity rises, the pressure relief valve core 47B overcomes the elastic force of the pressure relief spring 48B, the hydraulic cavity 43B becomes a closed cavity, no matter how the engine speed changes, the relative position of the tappet body 42B and the plunger 41B cannot change, and the performance of the engine is ensured. Because an oil leakage gap can be formed between the pressure relief valve core 47B and the sealing conical surface 46B, when the cam does not work, engine oil of an engine can enter the hydraulic cavity 43B through the oil inlet and the check valve and slowly leaks through the oil leakage gap, the working length of the hydraulic tappet can be extended or shortened, and the thermal expansion gap of a valve mechanism part can be automatically compensated. When the cam operates, the leakage oil clearance is closed, and the operating length of the hydraulic tappet 40A is hardly changed (only slightly shortened in the initial stage of the cam operation, and the shortening amount is controllable), so that the valve opening stroke is more "accurate".

When the engine works in the in-cylinder braking mode, the electromagnetic directional valve 80 is electrified, the oil supply oil path La is communicated with an engine oil path L0 (high-pressure oil path) through the electromagnetic directional valve 80, the hydraulic control switch valve 110 closes the connection between the hydraulic tappet 40B and an external oil path under the action of high-pressure oil P1, and the hydraulic tappet 40B does not extend under the action of the extension spring 45B1, so that the valve clearance is not automatically compensated any more, and the braking effect is not influenced. Therefore, the in-cylinder brake system of the engine is matched with the hydraulic tappet for use, so that the engine can not only exert the characteristic of in-cylinder braking, but also has the advantage of eliminating noise and impact caused by the valve clearance and brought by the hydraulic tappet.

In the present invention, the extension spring 45B1 may be installed at another position, and as shown in fig. 3, the extension spring 45B2 is connected between the tappet body 42B and the plunger 41B and is disposed outside the hydraulic chamber 43B. Even a compression spring may be used, and as shown in fig. 4, the compression spring 45B3 has one end abutting against the protruding end of the plunger 41B and the other end abutting against a member that is displaceable relative to the plunger 41B (in this embodiment, the other end of the compression spring 45B3 abuts against the valve bridge 60), and is disposed outside the hydraulic chamber 43B. Whether a tension spring or a compression spring, it is essentially an elastic device as long as it is satisfied that the plunger 41B is in a retracted state after the oil pressure in the hydraulic chamber 43B is removed.

In the invention, the hydraulic tappet 40B can also be used in combination with an in-cylinder brake system of other structure types, and at this time, the oil inlet of the tappet body 42B is connected with an engine oil path controlled by a switch valve, and the switch valve can be a hydraulic control switch valve or an electromagnetic switch valve.

In the present invention, the position of the hydraulic tappet 40B is not limited to the rocker arm, and it may be provided in any transmission member from the cam to the valve of the engine valve train.

The present invention is not limited to the embodiments described above, and all modifications that can be made based on the concept, principle, structure and method of the present invention will fall within the scope of the present invention.