CN213838700U

CN213838700U - Compression release type in-cylinder brake device for engine

Info

Publication number: CN213838700U
Application number: CN202022477617.6U
Authority: CN
Inventors: 吴广仓; 胡炳珍
Original assignee: Zhejiang Qiannengsheng Power Co ltd
Current assignee: Zhejiang Qiannengsheng Power Co ltd
Priority date: 2020-10-30
Filing date: 2020-10-30
Publication date: 2021-07-30
Anticipated expiration: 2030-10-30

Abstract

The utility model discloses a compression release type engine cylinder internal braking device, including drive power input camshaft, receive drive power input camshaft drive can wind the rotatory wobbling braking rocking arm assembly of rocking arm axle, braking rocking arm assembly includes the braking rocking arm and sets up the valve clearance control mechanism in the mounting hole of braking rocking arm, valve clearance control mechanism includes the braking plunger, has the reset spring of elasticity that makes progress and has the drive arrangement along the axial effort downwards to the braking plunger, the braking plunger is just to the exhaust valve. The utility model discloses a drive piston drives connecting rod, lower connecting rod swing in step, because the spherical head of last connecting rod, lower connecting rod does the torsion action respectively in the spherical groove that corresponds, goes up the connecting rod and twists reverse the in-process in the swing, the slider in the middle of extrudeing downwards, makes then middle slider extrusion lower connecting rod, and lower connecting rod extrudees braking plunger downwards to make the braking plunger move down, trigger the valve cap, thereby realize the braking work in the engine jar.

Description

Compression release type in-cylinder brake device for engine

Technical Field

The utility model belongs to the technical field of the engine, concretely relates to arresting gear in compression release type engine cylinder.

Background

Conventionally, a method of using an engine as a braking means is known, and it is only necessary to temporarily convert an engine that outputs power into a compressor that absorbs power after the engine stops supplying fuel. In the case of fuel cut-off, the engine sucks in the gas of the cylinder in the intake stroke, compresses the gas in the compression stroke, opens the exhaust valve at or near the end of the compression stroke of the engine piston, the compressed gas is released, the energy absorbed by the compressed gas in the compression stroke of the engine cannot return to the engine in the subsequent expansion stroke but is dissipated through the exhaust system of the engine, and the final result is that the engine absorbs the energy used by the vehicle to slow down the speed of the vehicle.

One prior example of an engine brake is disclosed in U.S. patent No. 3220392, supplied by Cummins (Cummins), according to which an engine braking system made with commercial success. However, such an engine brake system is mounted on a cylinder head of an engine, and in order to mount such an engine brake, the cylinder head needs to be redesigned, and the height, weight and cost of the engine are additionally increased. These problems are caused by the engine braking system being considered an accessory to the engine, rather than an integral part or assembly of the engine.

The engine brake in the prior art usually adopts a hydraulic brake mechanism, and the main structure is that a plunger piston which reciprocates is arranged in a main piston hole on a brake rocker arm, engine oil enters an oil cavity, the moving plunger piston moves downwards under the pressure of the engine oil, the plunger piston is contacted with an exhaust valve cap, a one-way valve is arranged in an oil path, and the exhaust valve is opened by utilizing the incompressibility of the engine oil.

Chinese patent publication No. CN 210919173U discloses a compression-release type engine cylinder inner brake device, comprising a camshaft, wherein the camshaft is provided with a plurality of exhaust cams, and the camshaft is provided with a camshaft axial passage extending along the axial direction of the camshaft, the exhaust cams are provided with exhaust cam radial holes communicated with the camshaft axial passage along the radial direction of the exhaust cams, the inside of the camshaft is provided with a brake mechanism corresponding to each exhaust cam, the brake mechanism comprises a sliding plunger and a control shaft which are connected, the sliding plunger is slidably mounted in the exhaust cam radial holes, and the control shaft is slidably mounted in the camshaft axial passage; when braking is carried out in the cylinder, the braking mechanism is controlled by the driving mechanism, the control shaft slides along the axial channel of the cam shaft and drives the sliding plunger to slide along the radial hole of the exhaust cam, so that the sliding plunger extends out of the cam surface of the exhaust cam to form a braking bulge, and even if the sliding plunger is subjected to the downward pressing force of the tappet, the sliding plunger cannot sink due to the bearing of the control shaft, the braking is reliable, and the braking effect is good; when the brake is not in the cylinder, the brake mechanism is controlled by the reset mechanism, and the sliding plunger retracts into the radial hole of the exhaust cam. The technical scheme of the patent adopts a hydraulic brake mechanism, and has the following defects: 1. the reaction speed is slow, and the opening and the closing of the reactor are delayed; 2. the hydraulic oil cavity is easy to crack due to the change of plunger stroke under the influence of oil temperature and oil pressure and the overhigh oil pressure when the engine rotates at a high speed, the engine brake is forced to be closed, and the like, thereby affecting the braking performance of the vehicle.

SUMMERY OF THE UTILITY MODEL

Therefore, the primary object of the present invention is to solve the above problems and to provide a compression-release type in-cylinder brake device for an engine.

In order to achieve the above object, the technical solution adopted by the present invention is to provide a compression-release type engine cylinder brake device, comprising a driving force input camshaft, a brake rocker arm assembly driven by the driving force input camshaft and capable of swinging around a rocker arm shaft, the brake rocker arm assembly comprises a brake rocker arm and a valve clearance control mechanism arranged in a mounting hole of the brake rocker arm, the valve clearance control mechanism comprises a brake plunger, a return spring with upward elastic force to the brake plunger and a driving device with downward acting force along the axial direction to the brake plunger, the brake plunger is opposite to the exhaust valve, when the brake plunger is at the bottom dead center and the distance between the brake plunger and the valve cap of the exhaust valve is the minimum, the brake rocker arm assembly swings each time, so that the brake plunger pushes the exhaust valve to open, and the brake in the engine cylinder is in a working state; when the brake plunger is positioned at the top dead center and the distance between the brake plunger and the valve cap of the exhaust valve is the maximum value, the brake plunger cannot touch and extrude the exhaust valve, and the engine is in a normal working state.

The driving device comprises a driving piston arranged in a slide way of the braking rocker arm, a middle slide block, a lower connecting rod, a power device and an upper connecting rod device, wherein the middle slide block is movably arranged in the driving piston and can move along the axial direction of the braking plunger relative to the driving piston, the lower connecting rod is arranged between the middle slide block and the braking plunger, the power device is used for controlling the driving piston to move along the slide way, the upper connecting rod device is used for controlling the moving stroke of the middle slide block, the moving path of the driving piston is crossed with the moving path of the middle slide block, the upper end and the lower end of the lower connecting rod are movably hinged with the bottom surface of the middle slide block and the top surface of the braking plunger respectively, and the driving piston is driven to move left and right in the slide way along the axial direction through the power device, so that the downward acting force of the lower connecting rod on the braking plunger is changed, and then the braking plunger moves along the axial direction.

The upper connecting rod device comprises an upper connecting rod, a valve adjusting screw, a sealing gasket and a nut, the valve adjusting screw is screwed in the mounting hole, the upper end and the lower end of the upper connecting rod are respectively hinged with the bottom surface of the valve adjusting screw and the top surface of the middle sliding block, and the required vertical height of the upper connecting rod when the upper connecting rod is pushed by the driving piston is adjusted by adjusting the distance between the valve adjusting screw and the sliding block, so that the upper connecting rod pushes the middle sliding block to move downwards, and the distance that the lower connecting rod pushes the braking plunger to move downwards is adjusted; the sealing gasket is sleeved on the valve adjusting screw and is attached to the upper end of the mounting hole in a sealing mode, and the nut is in threaded connection with the upper portion of the valve adjusting screw and tightly extrudes the sealing gasket.

The structure of the upper connecting rod and the structure of the lower connecting rod are consistent and comprise rod bodies, the two ends of each rod body are respectively provided with spherical heads, and the spherical heads are correspondingly matched with spherical grooves in the valve adjusting screw, the middle sliding block and the braking plunger respectively.

And a through hole is formed between the spherical grooves on the top surface and the bottom surface of the middle sliding block.

And the outer wall of the driving piston is correspondingly matched with the positions of the upper connecting rod and the lower connecting rod and is respectively provided with a limiting groove.

The power device comprises an oil passage hole, a spring seat and a clamp spring, the oil passage hole is matched with one end of the driving piston and communicated with the slide way, and the high-pressure oil device injects high-pressure oil into the slide way through the oil passage hole so as to push the driving piston to move in the slide way along the axis of the driving piston; the spring is arranged at the other end of the driving piston and has elasticity in the opposite direction of the oil pressure of high-pressure oil to the driving piston, the spring seat has a supporting effect on the spring, and the spring seat abuts against a clamp spring arranged on the inner wall of the slide way.

The high-pressure oil device comprises a first oil duct and a second oil duct which are arranged in the rocker shaft, the oil duct hole is communicated with the second oil duct through a radial oil duct, and high-pressure oil in the first oil duct is derived from high-pressure engine oil existing in the running process of the engine; an electromagnetic valve is arranged between the first oil duct and the second oil duct, and the first oil duct and the second oil duct are communicated or closed through the electromagnetic valve; the oil passage hole is also communicated with a pressure relief oil passage.

The inner diameter of the first oil passage is larger than the inner diameter of the second oil passage.

The driving force input cam shaft comprises a base circle, a first cam point and a second cam point, the first cam point and the second cam point are arranged on the outer surface of the base circle, a roller is arranged at one end, matched with the driving force input cam shaft, of the braking rocker arm, and a torsion spring is arranged between the braking rocker arm and the rocker arm shaft, so that the roller is always attached to the outer surface of the driving force input cam shaft.

The utility model has the advantages that:

the utility model discloses a compression release type braking device in engine cylinder, to the second oil duct fuel feeding through first oil duct, then make high-pressure oil pass through radial oil duct, the oil duct hole gets into the slide, thereby make drive piston work, drive piston drives the upper connecting rod in step, the lower connecting rod swing, because go up the connecting rod, the spherical head of lower connecting rod does the torsion action respectively in the spherical groove that corresponds, and the upper end of going up the connecting rod has received valve adjusting screw's restriction, it twists reverse the in-process at the swing to go up the connecting rod, slider in the middle of the downward extrusion, make middle slider extrusion lower connecting rod then, lower connecting rod extrudees braking plunger downwards, thereby make braking plunger move down, trigger the valve cap, thereby realize the braking work in the engine cylinder. In the process, the driving piston only needs a small stroke to realize the downward movement of the braking plunger, and the braking plunger has the advantages of high reaction speed, sensitive opening and no time delay.

The utility model discloses a compression release type braking device in engine cylinder, utilize the clearance between the valve cap of solenoid valve control braking rocking arm and exhaust valve, realize the switching and the maintenance of two kinds of states of braking and the normal work of engine in the engine cylinder, can be integrated with the engine, thereby reduce the volume and the weight of engine brake, need not adopt hydraulic control valve, the cost is reduced, braking reaction time has been reduced, the leakage that does not have high oil pressure to arouse, deformation and load fluctuation, valve clearance control mechanism does not receive the oil temperature, the influence of oil pressure, the lift is controllable, the brake power of engine has been improved.

Drawings

FIG. 1 is a schematic view of the compression-release engine in-cylinder brake apparatus of the present invention;

FIG. 2 is a schematic structural view of a brake plunger of a valve clearance control mechanism of a compression-release engine in-cylinder brake apparatus of the present invention at a top dead center position;

FIG. 3 is a schematic structural view of the brake plunger of the in-cylinder brake apparatus of the compression-release engine of the present invention at the bottom dead center position;

fig. 4 is a schematic structural view of the first oil passage and the second oil passage of the high-pressure oil device of the compression-release type engine cylinder internal braking device according to the present invention in a non-through state;

fig. 5 is a schematic structural view showing that the first oil passage and the second oil passage of the high-pressure oil device of the compression-release type in-cylinder brake device of the present invention are in a through state.

Detailed Description

The invention will be described in further detail with reference to the following drawings and detailed description:

referring to fig. 1 to 5, the present invention provides a compression release type engine cylinder brake apparatus, including a driving force input camshaft 1, a braking rocker arm assembly 3 driven by the driving force input camshaft 1 to swing around a rocker shaft 2, wherein the braking rocker arm assembly 3 includes a braking rocker arm 4 and a valve clearance control mechanism 6 disposed in a mounting hole 5 of the braking rocker arm 4, the valve clearance control mechanism 6 includes a braking plunger 7, a return spring 8 having an upward elastic force on the braking plunger 7, and a driving device having an axial downward acting force on the braking plunger 7, the braking plunger 7 faces an exhaust valve 9, when the braking plunger 7 is at a bottom dead center and the braking plunger 7 is at a minimum distance from a valve cap 10 of the exhaust valve 9, each swing of the braking rocker arm assembly 3 is actuated, so that the braking plunger 7 pushes the exhaust valve 9 to open, the brake in the engine cylinder is in a working state; when the brake plunger 7 is at the top dead center and the distance between the brake plunger 7 and the valve cap 10 of the exhaust valve 9 is the maximum value, the brake plunger 7 cannot touch and press the exhaust valve 9, and the engine is in a normal working state.

The driving force input camshaft 1 comprises a base circle 11, and a first cam point 12 and a second cam point 13 which are arranged on the outer surface of the base circle 11, wherein a roller 14 is arranged at one end, matched with the driving force input camshaft 1, of the braking rocker arm 4, a torsion spring is arranged between the braking rocker arm 4 and the rocker arm shaft 2, or one end of the roller 14 of the braking rocker arm 4 is applied with elasticity through a spring, so that the roller 14 is always attached to and leaned against the outer surface of the driving force input camshaft 1. When the part of the base circle 11 of the driving force input camshaft 1 contacts with the roller 14, only the roller 14 rotates around the axis thereof, and the brake rocker arm 4 is stationary; when the first and second cam points 12, 13 on the driving force input camshaft 1 come into driving contact with the roller 14, the first and second cam points 12, 13 press the brake rocker arm 4 to rotationally swing upward about the rocker shaft 2, so that the valve clearance control mechanism 6 at the other end of the brake rocker arm 4 moves toward the valve cap 10. In the process, when the brake in the engine cylinder works, the driving device enables the brake plunger 7 to move downwards and reach the bottom dead center position, so that the brake plunger 7 can extrude the valve cap 10; when the brake in the engine cylinder does not work, the driving device does not work, and the brake plunger 7 is at the top dead center position.

The driving device comprises a driving piston 16 arranged in a slide way 15 of the brake rocker arm 4, an intermediate slide block 17 movably arranged in the driving piston 16 and capable of moving along the axial direction of the brake plunger 7 relative to the driving piston 16, a lower connecting rod 18 arranged between the intermediate slide block 17 and the brake plunger 7, a power device 19 for controlling the driving piston 16 to move along the slide way 15 and an upper connecting rod device 20 for controlling the moving stroke of the intermediate slide block 17, the moving path of the driving piston 16 is crossed with the moving path of the middle slide block 17, the upper end and the lower end of the lower connecting rod 18 are respectively and movably hinged with the bottom surface of the middle slide block 17 and the top surface of the braking plunger 7, by means of the power device 19, the driving piston 16 is driven to move left and right along the axial direction in the slideway 15, thereby changing the downward force of the lower link 18 on the detent plunger 7, which in turn causes the detent plunger 7 to move axially.

The upper connecting rod device 20 comprises an upper connecting rod 21, a valve adjusting screw 22, a sealing gasket 23 and a nut 24, the valve adjusting screw 22 is screwed in the mounting hole 5, the upper end and the lower end of the upper connecting rod 21 are respectively hinged with the bottom surface of the valve adjusting screw 22 and the top surface of the middle sliding block 17, and the height required by the vertical shape of the upper connecting rod 21 when being pushed by the driving piston 16 is adjusted by adjusting the distance between the valve adjusting screw 22 and the middle sliding block 17, so that the upper connecting rod 21 pushes the middle sliding block 17 to move downwards, and the distance for the lower connecting rod 18 to push the brake plunger 7 to move downwards is adjusted; the sealing gasket 23 is sleeved on the valve adjusting screw 22 and is attached to the upper end of the mounting hole 5 in a sealing mode, and the nut 24 is screwed on the upper portion of the valve adjusting screw 22 and tightly extrudes the sealing gasket 23.

The upper connecting rod 21 and the lower connecting rod 18 are consistent in structure and respectively comprise a rod body 25, two ends of the rod body 25 are respectively provided with a spherical head 26, and the spherical heads 26 are respectively correspondingly matched with the valve adjusting screw 22, the middle sliding block 17 and a spherical groove 27 on the brake plunger 7.

The outer wall of the driving piston 16 is provided with a limiting groove 28 corresponding to the upper connecting rod 21 and the lower connecting rod 18.

A through hole 29 is formed between the spherical grooves 27 on the top and bottom surfaces of the intermediate slider 17.

The power device 19 comprises an oil passage hole 30, a spring 31, a spring seat 32 and a clamp spring 33, the oil passage hole 30 is matched with one end of the driving piston 16, the oil passage hole 30 is communicated with the slideway 15, and the high-pressure oil device 34 injects high-pressure oil into the slideway 15 through the oil passage hole 30 so as to push the driving piston 16 to move in the slideway 15 along the axis of the driving piston 16; the spring 31 is located at the other end of the driving piston 16 and has an elastic force in the direction opposite to the oil pressure of the high-pressure oil to the driving piston 16, the spring seat 32 has a supporting function to the spring 31, and the spring seat 32 abuts against a snap spring 33 mounted on the inner wall of the slideway 15.

The installation of the driving device, the upper link device 20 and the power device 19 is as follows: the installation hole 5 is arranged in the brake rocker arm 4, the slideway 15 and the installation hole 5 are arranged in a crossed way and are preferably vertically communicated, and through the slideway 15, a driving piston 16 can be firstly put in, then, the lower connecting rod 18 is installed through the slider hole 35 of the driving piston 16, in which the intermediate slider 17 is installed, then the middle slide block 17 and the upper connecting rod device 20 are installed, finally, the spring 31 and the spring seat 32 are sequentially installed in the slideway 15, the snap spring 33 is clamped in the snap spring groove 36 on the inner wall of the slideway 15, so that the spring 31 has a rightward elastic force to the driving piston 16, and the driving piston 16 is always at the right dead center position, the oil passage hole 30 is at the right side of the slide passage 15, the high pressure oil has a leftward driving force to the driving piston 16, when the driving force is larger than the superimposed elastic force of the spring 31 and the return spring 8 at the lower end of the brake plunger 7, the piston 16 is driven to move leftward.

The high-pressure oil device 34 comprises a first oil channel 37 and a second oil channel 38 which are arranged in the rocker arm shaft 2, the oil channel hole 30 is communicated with the second oil channel 38 through a radial oil channel 39, and high-pressure oil in the first oil channel 37 comes from high-pressure engine oil existing in the engine operation process; an electromagnetic valve 40 is arranged between the first oil channel 37 and the second oil channel 38, the electromagnetic valve 40 is fixed on a rocker shaft seat 49, and the first oil channel 37 and the second oil channel 38 are communicated or closed through the electromagnetic valve 40; the oil passage hole 30 further penetrates the pressure relief oil passage 41.

The first oil passage 37 has a larger inner diameter than the second oil passage 38.

The utility model discloses in, still be equipped with exhaust cam point 42 on the drive power input camshaft 1, as the right side part shown in fig. 1, exhaust rocking arm 43 articulates on rocking arm axle 2, and the one end of exhaust rocking arm 43 is equipped with gyro wheel 44, and gyro wheel 44 supports and leans on the surface at drive power input camshaft 1, and the other end of exhaust rocking arm 43 is connected on valve bridge 45, the body of rod 25 of exhaust valve 9 is connected to valve bridge 45, and exhaust valve 9 is in engine cylinder lid 46, be equipped with valve spring 47 between valve bridge 45 and the cylinder lid 46. In the above-described embodiments, the rocker shaft 2 related to the exhaust rocker arm 43 and the driving force input camshaft 1 are the rocker shaft 2 related to the brake rocker arm 4 and the driving force input camshaft 1, and for the sake of clarity of the drawing, the exhaust rocker arm 43 and the brake rocker arm 4 are shown separately on both sides of the cylinder head 46 in fig. 1. When the engine normally works, the exhaust valve 9 and the valve spring 47 arranged between the cylinder cover 46 and the valve bridge 507 are linked together with the valve bridge 45, when the roller of the exhaust rocker arm 43 contacts with the exhaust cam point 42 section of the driving force input camshaft 1, the other end of the exhaust rocker arm moves downwards, the valve bridge 45 is pressed, the spring force of the valve spring 47 is overcome, the exhaust valve is opened, exhaust gas generated by engine combustion is released, and when the roller of the exhaust rocker arm 43 contacts with the base circle 11 section of the driving force input camshaft 1, the exhaust valve 9 is restored to the sealing state with the cylinder cover 46.

The following description is made on the working principle of the compression-release type engine in-cylinder brake device of the present invention:

the utility model discloses a compression release type braking device in engine cylinder, when needing the engine to switch to the braking operating condition in the engine cylinder from normal operating condition, send actuating signal and open the power for solenoid valve 40 through engine ECU controller to solenoid valve 40, solenoid valve 40 is its just, when the electric current of negative terminal is opened, case 48 of solenoid valve 40 is under the effect of magnetic force, upwards slide, thereby make first oil duct 37 link up with second oil duct 38, make high-pressure engine oil pass through second oil duct 38, radial oil duct 39 and oil duct hole 30 flow direction valve clearance control mechanism 6, promptly: in high-pressure machine oil got into the right side of slide 15, high-pressure machine oil overcome the elasticity of drive piston 16 left end spring 31 and the superimposed elastic force of braking plunger 7 lower extreme reset spring 8, will drive piston 16 and promote to left to berth on spring holder 32, last connecting rod 21, middle slider 17, lower connecting rod 18 and braking plunger 7 this moment are collineation vertical state, promptly: in the process, as the distance between the top surface of the brake plunger 7 and the bottom surface of the middle slider 17 is smaller than the length of the lower connecting rod 18, and the distance between the bottom surface of the valve adjusting screw 22 and the top surface of the middle slider 17 is smaller than or equal to the length of the upper connecting rod 21, the lower connecting rod 18 downwards extrudes the brake plunger 7 under the driving action of the drive piston 16, so that the brake plunger 7 downwards moves, the upper connecting rod 21 extrudes or does not extrude the middle slider 17 to downwards move, when the size of the downwards moving displacement of the brake plunger 7 depends on the distance between the top surface of the brake plunger 7 and the bottom surface of the middle slider 17, the distance can be adjusted by only loosening the nut 24 and rotating the valve adjusting screw 22, and after the adjustment is finished, the nut 24 is fastened. In the above process, the upper link 21 and the lower link 18 are switched from the inclined state to the vertical state, the brake plunger 7 is extended to the operating position, the gap between the brake plunger 7 and the valve cap 10 of the exhaust valve 9 is eliminated or reduced, the driving force input camshaft 1 is connected with a transmission mechanism of the engine and rotates together with the engine, the driving force input camshaft 1 is connected with the first cam point 12 and the second cam point 13 to enable the brake rocker arm 4 to swing up and down around the rocker shaft 2, the brake plunger 7 on the brake rocker arm 4 applies pressure to the valve cap 10 of the exhaust valve 9, the pressure applied to the valve cap 10 is transmitted to the exhaust valve 9, and the exhaust valve 9 overcomes the elastic force of the valve spring 47, opens the exhaust valve 9 and releases compressed air. When the in-cylinder brake of the engine is not needed, the engine ECU controller cuts off the power supply of the electromagnetic valve 40, the electromagnetic valve 40 does not generate magnetic force, the valve core 48 moves downwards under the action of the spring force of the electromagnetic valve 40, the valve core 48 cuts off an oil path between the first oil path 37 and the second oil path 38, the oil path hole 30 is penetrated with a pressure relief oil path 41, the pressure relief oil path 41 is a gap between the brake rocker arm 4 and the rocker shaft 2, so that the high-pressure engine oil is relieved, the driving piston 16 moves rightwards under the action of the spring force of the spring 31, and the brake plunger 7 moves upwards under the action of the return spring 8, so that the brake plunger 7 retracts to a non-operation position, namely an off position of the in-cylinder brake of the engine, and is separated from the normal work of the engine.

The compression release type engine cylinder brake device provided by the embodiment of the present invention is described in detail above, and the principle and the implementation of the present invention are explained by applying specific examples herein, and the description of the above embodiments is only used to help understanding the technical solution disclosed by the present invention; meanwhile, for the general technical personnel in the field, according to the idea of the present invention, there are changes in the specific implementation and application scope, to sum up, the content of the present specification should not be understood as the limitation of the present invention.

Claims

1. A compression-release in-cylinder brake device for an engine, characterized in that: the brake rocker arm assembly comprises a drive force input cam shaft and a brake rocker arm assembly which is driven by the drive force input cam shaft and can swing around a rocker arm shaft in a rotating mode, the brake rocker arm assembly comprises a brake rocker arm and a valve clearance control mechanism arranged in a mounting hole of the brake rocker arm, the valve clearance control mechanism comprises a brake plunger, a return spring having upward elasticity for the brake plunger and a driving device having axial downward acting force for the brake plunger, the brake plunger is over against an exhaust valve, when the brake plunger is located at a bottom dead center and the distance between the brake plunger and a valve cap of the exhaust valve is the minimum value, each swing of the brake rocker arm assembly enables the brake plunger to push the exhaust valve to open, and the brake in an engine cylinder is in a working state; when the brake plunger is positioned at the top dead center and the distance between the brake plunger and the valve cap of the exhaust valve is the maximum value, the brake plunger cannot touch and extrude the exhaust valve, and the engine is in a normal working state.

2. The compression-release type engine in-cylinder brake device according to claim 1, characterized in that: the driving device comprises a driving piston arranged in a slide way of the braking rocker arm, a middle slide block, a lower connecting rod, a power device and an upper connecting rod device, wherein the middle slide block is movably arranged in the driving piston and can move along the axial direction of the braking plunger relative to the driving piston, the lower connecting rod is arranged between the middle slide block and the braking plunger, the power device is used for controlling the driving piston to move along the slide way, the upper connecting rod device is used for controlling the moving stroke of the middle slide block, the moving path of the driving piston is crossed with the moving path of the middle slide block, the upper end and the lower end of the lower connecting rod are movably hinged with the bottom surface of the middle slide block and the top surface of the braking plunger respectively, and the driving piston is driven to move left and right in the slide way along the axial direction through the power device, so that the downward acting force of the lower connecting rod on the braking plunger is changed, and then the braking plunger moves along the axial direction.

3. The compression-release type engine in-cylinder brake device according to claim 2, characterized in that: the upper connecting rod device comprises an upper connecting rod, a valve adjusting screw, a sealing gasket and a nut, the valve adjusting screw is screwed in the mounting hole, the upper end and the lower end of the upper connecting rod are respectively hinged with the bottom surface of the valve adjusting screw and the top surface of the middle sliding block, and the required vertical height of the upper connecting rod when the upper connecting rod is pushed by the driving piston is adjusted by adjusting the distance between the valve adjusting screw and the sliding block, so that the upper connecting rod pushes the middle sliding block to move downwards, and the distance that the lower connecting rod pushes the braking plunger to move downwards is adjusted; the sealing gasket is sleeved on the valve adjusting screw and is attached to the upper end of the mounting hole in a sealing mode, and the nut is in threaded connection with the upper portion of the valve adjusting screw and tightly extrudes the sealing gasket.

4. The compression-release type engine in-cylinder brake device according to claim 3, characterized in that: the structure of the upper connecting rod and the structure of the lower connecting rod are consistent and comprise rod bodies, the two ends of each rod body are respectively provided with spherical heads, and the spherical heads are correspondingly matched with spherical grooves in the valve adjusting screw, the middle sliding block and the braking plunger respectively.

5. The compression-release type engine in-cylinder brake device according to claim 2, 3 or 4, characterized in that: and a through hole is formed between the spherical grooves on the top surface and the bottom surface of the middle sliding block.

6. The compression-release type engine in-cylinder brake device according to claim 3 or 4, characterized in that: and the outer wall of the driving piston is correspondingly matched with the positions of the upper connecting rod and the lower connecting rod and is respectively provided with a limiting groove.

7. The compression-release type engine in-cylinder brake device according to claim 2, characterized in that: the power device comprises an oil passage hole, a spring seat and a clamp spring, the oil passage hole is matched with one end of the driving piston and communicated with the slide way, and the high-pressure oil device injects high-pressure oil into the slide way through the oil passage hole so as to push the driving piston to move in the slide way along the axis of the driving piston; the spring is arranged at the other end of the driving piston and has elasticity in the opposite direction of the oil pressure of high-pressure oil to the driving piston, the spring seat has a supporting effect on the spring, and the spring seat abuts against a clamp spring arranged on the inner wall of the slide way.

8. The compression-release type engine in-cylinder brake apparatus as defined in claim 7, wherein: the high-pressure oil device comprises a first oil duct and a second oil duct which are arranged in the rocker shaft, the oil duct hole is communicated with the second oil duct through a radial oil duct, and high-pressure oil in the first oil duct is derived from high-pressure engine oil existing in the running process of the engine; an electromagnetic valve is arranged between the first oil duct and the second oil duct, and the first oil duct and the second oil duct are communicated or closed through the electromagnetic valve; the oil passage hole is also communicated with a pressure relief oil passage.

9. The compression-release type engine in-cylinder brake apparatus as defined in claim 8, wherein: the inner diameter of the first oil passage is larger than the inner diameter of the second oil passage.

10. The compression-release type engine in-cylinder brake device according to claim 1, characterized in that: the driving force input cam shaft comprises a base circle, a first cam point and a second cam point, the first cam point and the second cam point are arranged on the outer surface of the base circle, a roller is arranged at one end, matched with the driving force input cam shaft, of the braking rocker arm, and a torsion spring is arranged between the braking rocker arm and the rocker arm shaft, so that the roller is always attached to the outer surface of the driving force input cam shaft.