CN211343050U - Fully-variable electro-hydraulic valve system with buffering function - Google Patents

Abstract

The utility model discloses a full variable electricity liquid valve system with buffer function, include: the sliding sleeve is fixed relative to an engine, the piston abuts against the valve assembly, and the spiral shaft is axially controlled by a cam surface of the camshaft; the first end of the spiral shaft is provided with a spiral surface, and the second end of the spiral shaft is provided with a control gear; the sliding sleeve is provided with a buffer oil hole communicated with the buffer cavity, and the buffer oil hole is communicated with a low-pressure oil way of the engine through a throttling device. When the valve is about to be seated, the piston firstly collides with the buffer ring, and because of the action of the throttling device, engine oil in the buffer cavity plays a damping role on the movement of the buffer ring, so that the valve is slowly seated, the impact damage to the sealing surfaces of the valve and the valve seat is reduced, and the service life of the valve mechanism is effectively prolonged.

Description

Fully-variable electro-hydraulic valve system with buffering function

Technical Field

The utility model relates to an engine valve mechanism technical field especially relates to a full variable electricity liquid valve system with buffer function.

Background

The Fully Variable Valve System (FVVS) can realize continuous variation of the maximum lift of the Valve, the opening continuous angle of the Valve and the Valve timing, and has important significance for energy conservation and emission reduction of the engine. The FVVS can adopt the mode of early closing of the inlet valve (EIVC) to control the working medium quantity entering the cylinder, thereby canceling the throttle valve, the gasoline engine without the throttle valve can greatly reduce the pumping loss, and the fuel consumption in medium and small loads is reduced by 10-15%. The fully variable valve mechanism is matched with supercharging intercooling, so that the problems of deflagration and high heat load of an engine after supercharging can be solved, low-temperature combustion is realized on the premise of greatly improving the average effective pressure, the heat efficiency of the engine is improved, and the emission of harmful gas is reduced; therefore, the FVVS technology has become one of the important development directions of new internal combustion engine technology.

At present, a more advanced fully variable valve mechanism is a MultiAir (also known as UniAir) system developed by combining Schaeffler and Feiyat, the system adopts a camshaft-driven electro-hydraulic valve mechanism, and the valve motion law is controlled by combining a camshaft and an electromagnetic valve. The working principle of the system is as follows: the hydraulic piston is driven by the cam and is connected with the driving piston through a sliding sleeve cavity, and the sliding sleeve cavity is controlled by a switch type electromagnetic valve. When the electromagnetic valve is in a completely closed state, the hydraulic piston pushes the driving piston through the hydraulic pressure to transmit the hydraulic pressure generated by the rotation of the cam to the air valve; the intake valve is now fully cam controlled and in an open state. When the electromagnetic valve is in a fully open state, the liquid pressure can not transmit the driving force, the hydraulic piston can not push the driving piston, and the intake valve is no longer controlled by the cam and is in a fall-back or closed state. By controlling the opening and closing time of the electromagnetic valve, various different valve motion laws can be realized, and the function of the fully variable valve mechanism is realized. However, the electromagnetic valve has a complex structure and high price, and the popularization and application of the technology are limited.

In order to replace an expensive high-speed solenoid valve, chinese patent CN109339896A discloses a fully variable electro-hydraulic valve device with a buffer function, comprising: a camshaft and a valve assembly; the air valve assembly comprises a spiral shaft, a sliding sleeve, a piston and a return spring, wherein the spiral shaft and the piston are respectively connected with the sliding sleeve in a sliding and sealing mode, the piston abuts against the air valve assembly, a sealed sliding sleeve cavity is formed in the sliding sleeve by a space between the spiral shaft and the piston, and the return spring is clamped between the spiral shaft and the piston; the screw shaft is controlled by the cam surface of the camshaft in the axial direction; the peripheral wall of the spiral shaft, which is connected with the sliding sleeve in a sliding and sealing manner, is a spiral peripheral wall, the end part of the spiral shaft is provided with a control gear meshed with a rack, and the rack is driven by a linear actuating mechanism controlled by an engine electric control unit; the oil inlet hole and the limiting oil hole are formed in the sliding sleeve, the oil inlet hole is close to the spiral shaft, the limiting oil hole is close to the piston, the oil inlet hole and the limiting oil hole are respectively communicated with a low-pressure oil way of the engine, and a one-way valve is arranged on a connecting pipeline between the limiting oil hole and the low-pressure oil way of the engine. The invention adopts the screw shaft and the camshaft to jointly control the valve motion, changes the opening and closing time of the oil inlet hole by rotating the screw shaft, can realize the function of a fully variable valve mechanism, has high response speed and convenient control, replaces a high-speed electromagnetic valve with high price, and is suitable for a multi-cylinder engine.

However, this device finds application in: the mechanism has the problem of too high seating speed in the process of seating the electro-hydraulic control valve, and impacts and damages the sealing surfaces of the valve and the valve seat, thereby influencing the service life. In addition, in the stopping process of the engine, hydraulic oil in the sliding sleeve cavity can slowly leak, and when the engine is started, the sliding sleeve cavity can have an oil-free phenomenon, so that the system fails to work.

SUMMERY OF THE UTILITY MODEL

The above-mentioned not enough to prior art, the utility model provides a full variable electricity liquid valve system with buffer function to slow down the air valve speed of taking a seat, reduce the impact damage that causes the sealed face of valve and valve seat, improve life.

In order to solve the technical problem, the utility model discloses following technical scheme:

a fully variable electro-hydraulic valve system with a damping function, comprising: a camshaft and a valve assembly; the sliding sleeve is fixed relative to an engine, the screw shaft and the piston are respectively connected with the sliding sleeve in a sliding and sealing mode, an inner cavity between the screw shaft and the piston is called a sliding sleeve cavity, the return spring is clamped between the screw shaft and the piston, the piston abuts against the valve assembly, and the screw shaft is controlled by a cam surface of the camshaft in the axial direction; the screw shaft is provided with a first end and a second end which are oppositely arranged, the first end is provided with a screw surface, the second end is in transmission connection with a gear rack mechanism, the gear rack mechanism comprises a control gear and a rack, the control gear is arranged at the second end of the screw shaft, and the rack is driven by a linear actuating mechanism controlled by an electric control unit of an engine; the sliding sleeve is provided with an oil inlet hole and a limiting oil hole, the oil inlet hole and the limiting oil hole are respectively communicated with a low-pressure oil way of the engine, and a one-way valve is arranged on a connecting pipeline between the oil inlet hole and the low-pressure oil way of the engine; a stepped hole structure is arranged at the end part of the piston of the sliding sleeve, the stepped hole structure comprises a large hole and a small hole, the small hole is matched with the sliding sealing surface of the piston, a buffer ring is arranged in the large hole, the buffer ring is sleeved on the sliding sealing surface of the piston and is in sliding sealing fit with the inner peripheral surface of the large hole, and the buffer ring and the piston form a buffer cavity in the stepped hole; the peripheral surface of the outer end of the piston is provided with a flange which is used for colliding the buffer ring when a valve of the valve assembly is seated, the end part of the piston of the sliding sleeve is provided with a baffle, and when the valve of the valve assembly is closed, a buffer distance is reserved between the buffer ring and the baffle; the sliding sleeve is provided with a buffer oil hole communicated with the buffer cavity, and the buffer oil hole is communicated with a low-pressure oil way of the engine through a throttling device.

The screw shaft is provided with an annular groove, the annular groove is provided with an oil through hole, the oil through hole is communicated with the annular groove and the sliding sleeve cavity, and the oil inlet hole is constantly communicated with the annular groove in the movement process of the screw shaft; the head of the spiral surface of the spiral shaft is provided with a spiral shaft abutting plane, one end of the piston, which is opposite to the spiral shaft, is provided with a piston axial protruding part, and the head of the piston axial protruding part is provided with a piston abutting plane; the sliding sleeve is provided with a first positioning pin, the piston is provided with a guide groove extending along the axial direction, and the first positioning pin extends into the guide groove; the limiting oil hole is arranged at a position which is blocked by the spiral shaft before the spiral surface touches the piston abutting plane; the gear rack mechanism is further provided with a limiting device and a return spring, when the return spring enables the rack to move to the limit position limited by the limiting device, the piston abutting plane abuts against the spiral shaft abutting plane, and the valve lift of the valve assembly is controlled by the cam shaft.

The first end of the screw shaft is provided with a screw shaft axial protrusion part, the head of the screw shaft axial protrusion part is provided with another screw shaft abutting plane, and the root of the screw surface is intersected with the root of the screw shaft axial protrusion part; the number of the piston axial protruding parts is two, the heads of the two piston axial protruding parts are respectively provided with a piston abutting plane, and the piston abutting planes correspond to the screw shaft abutting planes one by one.

The two pistons are abutted against the same plane, and the two screw shafts are abutted against the same plane.

The two piston abutting planes are symmetrically arranged relative to the center of the piston, and the two screw shaft abutting planes are symmetrically arranged relative to the center of the screw shaft.

And a thrust bearing is arranged at the second end of the spiral shaft, and a wear-resistant gasket is arranged between the thrust bearing and the cam surface of the cam shaft.

Wherein the control gear is connected with the screw shaft in a torque transmission manner.

Wherein the rack is simultaneously meshed with the control gears of the plurality of screw shafts.

The linear actuating mechanism is a linear motor or an actuating electromagnet or an air cylinder or a hydraulic cylinder.

The sliding sleeve is provided with a second positioning pin, and the second positioning pin extends into the annular groove.

The utility model adopts the above technical scheme after, its technological effect is:

1) the utility model discloses a screw axis and camshaft joint control valve motion change the switching of spacing oilhole through rotating the screw axis constantly, can realize the function of full variable valve mechanism, and during the return stroke, hydraulic oil gets into the sliding sleeve chamber from the inlet port, makes the screw axis reset fast together with reset spring, and the sharp actuating mechanism drive screw axis by the automatically controlled unit control of engine rotates, and response speed is fast, and control is convenient, has replaced the high-speed solenoid valve of high price, is fit for multi-cylinder engine and uses.

2) When the valve is about to be seated, the piston firstly collides with the buffer ring, and because of the action of the throttling device, engine oil in the buffer cavity plays a damping role in the movement of the buffer ring, and the buffer ring moves slowly, so that the valve is slowly seated, the impact damage to the sealing surface of the valve and the valve seat is reduced, and the service life of the valve mechanism is effectively prolonged. When the valve descends again, the buffer ring moves downwards under the action of the pressure of the oil, and the buffer ring has enough time to move to the position of the baffle plate before the valve is seated again due to the short buffer distance; the valve buffering effect can be adjusted by adjusting the throttling effect and the buffering distance of the throttling device.

3) After the ECU of the engine is shut down and the power is off, the rack moves to the limit position of the limiting device under the action of the return spring, at the moment, the piston abutting plane abuts against the spiral shaft abutting plane, engine oil does not work, the cam and the valve are in a rigid connection state, and the valve lift of the valve assembly is completely controlled by the cam shaft, so that the influence of the engine oil loss on the normal operation of the system is avoided.

Drawings

FIG. 1 is a cross-sectional view of an embodiment of the fully variable electro-hydraulic valve system with a cushioning function of the present invention;

FIG. 2 is a sectional view of a portion of the embodiment of FIG. 1, taken along a plane formed by the center of the limiting oil hole and the center of the sliding sleeve, when the valve is in a fully closed state;

FIG. 3 is a cross-sectional view taken at A-A of FIG. 2;

FIG. 4 is a schematic perspective view of the screw shaft of FIG. 1;

FIG. 5 is a schematic perspective view of the piston of FIG. 1;

FIG. 6 is a schematic perspective view of the screw shaft of FIG. 1 in a position abutting against the abutting surface of the piston;

FIG. 7 is a schematic view of a rack and pinion mechanism driving the screw spindle in the embodiment shown in FIG. 1;

FIG. 8 is a crank angle/valve lift graph of the embodiment shown in FIG. 1; in the figure, 101-camshaft, 102-screw shaft, 102A-control gear, 102B-screw shaft abutting plane, 102C-screw shaft axial projection, 102D-annular groove, 102E-screw surface, 102F-oil through hole, 103-sliding sleeve, 104-return spring, 105-piston, 105A-piston axial projection, 105B-piston abutting plane, 105C-guide groove, 105D-flange, 106-valve component, 107-oil inlet hole, 108-one-way valve, 109-oil bottom shell, 110-pressure retaining valve, 111-wear-resistant gasket, 112-thrust bearing, 113-rack, 114-pressure reducing valve, 115-return spring, 116-limiting device, 117-linear actuator, 118-limiting oil hole, 119-a first positioning pin, 120-a second positioning pin, 121-a buffer ring, 122-a baffle, 123-a buffer oil hole, 124-a throttling device, a G-spiral surface theoretical limit position, a P-piston abutting plane edge point, a Q-sliding sleeve cavity, an R-buffer cavity and an S-buffer distance.

Detailed Description

The present invention will be further explained with reference to the drawings and examples.

As shown in FIG. 1, in the fully variable electro-hydraulic valve system with the buffering function, a sliding sleeve 103 is fixed relative to an engine, a screw shaft 102 and a piston 105 are respectively connected with the sliding sleeve 103 in a sliding and sealing mode, the screw shaft 102 is controlled by a cam surface of a camshaft 101 in the axial direction, and the piston 105 abuts against a valve assembly 106.

In the sliding sleeve 103, a space between the screw shaft 102 and the piston 105 is a sliding sleeve cavity Q, and the return spring 104 is sandwiched between the screw shaft 102 and the piston 105. The sliding sleeve 103 is provided with an oil inlet 107 and a limiting oil hole 118 (shown by dotted lines in FIG. 1); the oil inlet 107 is connected with a one-way valve 108, is communicated with an engine oil circuit through a pressure reducing valve 114 and is communicated with an oil pan 109 through a pressure retaining valve 110; the stopper oil hole 118 communicates with the engine oil passage through the pressure reducing valve 114, and communicates with the oil pan 109 through the pressure retaining valve 110.

A stepped hole structure is arranged at the end part of the piston of the sliding sleeve 103, the stepped hole structure comprises a large hole and a small hole, the small hole is matched with the sliding sealing surface of the piston 105, a buffer ring 122 is arranged in the large hole, the buffer ring 122 is sleeved on the sliding sealing surface of the piston 105 and is in sliding sealing fit with the inner peripheral surface of the large hole, and a buffer cavity R is formed in the stepped hole by the buffer ring 122 and the piston 105; the outer end peripheral surface of the piston 105 is provided with a flange 105D for hitting the cushion ring 121 when the valve of the valve assembly 106 is seated, a stopper plate 122 is attached to the piston end of the slide sleeve 103, and a cushion distance S is provided between the cushion ring 121 and the stopper plate 122 when the valve of the valve assembly 106 is closed.

The sliding sleeve 103 is further provided with a buffer oil hole 123 communicated with the buffer cavity R, the buffer oil hole 123 is connected with a throttling device 124, is communicated with an engine oil circuit through a pressure reducing valve 114 and is communicated with the oil pan 109 through a pressure retaining valve 110; the engine oil line and the associated pressure reducing valve 114, pressure retaining valve 110, oil pan 109, etc. constitute a low-pressure oil line of the engine, and the throttle device may be a throttle valve or an orifice, etc.

The structure has a buffering function. When the valve is about to be seated, the piston 105 firstly collides with the buffer ring 121, and due to the action of the throttling device 124, the engine oil in the buffer cavity R plays a role in damping the motion of the buffer ring 121, and the buffer ring 121 slowly moves to make the valve be seated slowly, so that the impact damage to the sealing surfaces of the valve and a valve seat is reduced, and the service life of the valve mechanism is effectively prolonged. When the valve descends again, the buffer ring 121 moves downwards under the action of the oil pressure, and the buffer ring 121 has enough time to move to the position of the baffle 122 before the valve is seated again because the buffer distance S is short; the valve cushioning effect can be adjusted by adjusting the throttling effect and the cushioning distance of the throttling device 124.

As shown in fig. 1, 4 and 7, the screw shaft 102 has a first end and a second end which are oppositely arranged, the first end is provided with a screw surface 102E, the head of the screw surface 102E is provided with a screw shaft abutting plane 102B, the second end is in transmission connection with a gear-rack mechanism, the gear-rack mechanism comprises a control gear 102A and a rack 113, the control gear 102A is arranged at the second end of the screw shaft 102, and the rack 103 is driven by a linear actuator 117 controlled by an Electronic Control Unit (ECU) of an engine. The control gear 102A is connected to the screw shaft 102 in two ways, one is a fixed connection, and the other is a control gear 102A which is axially slidable relative to the screw shaft 102 but not rotatable relative thereto, such as a spline connection, which must be capable of transmitting torque regardless of the connection. The linear actuator 117 is a mature technology, and may be a linear motor, an actuating electromagnet, an air cylinder, a hydraulic cylinder, or the like, and the connection relationship between the linear actuator and the rack 113 is well known to those skilled in the art, and will not be described herein.

As shown in fig. 1 and 4, the screw shaft 102 is provided with an annular groove 102D, the annular groove 102D is opened with an oil passage hole 102F, the oil passage hole 102F communicates with the annular groove 102D and the sleeve cavity Q, and the oil inlet hole 107 is constantly in communication with the annular groove 102D during the movement of the screw shaft 102.

As shown in fig. 4, in order to make the force more uniform when abutting, a screw shaft axial protrusion 102C is further provided at the first end of the screw shaft 102, the head of the screw shaft axial protrusion 102C is provided with another screw shaft abutting plane 102B, and the root of the screw surface 102E meets the root of the screw shaft axial protrusion 102C. The two screw axes abut against the plane 102B in the same plane and are symmetrically arranged relative to the center of the screw axis 102.

As shown in fig. 1 and 5, the sliding sleeve 103 is provided with a first positioning pin 119, the piston 105 is provided with a guide groove 105C extending in the axial direction, the first positioning pin 119 extends into the guide groove 105C, and the rotational degree of freedom of the piston 105 relative to the sliding sleeve 103 is restricted by the first positioning pin 119, that is, the piston 105 can only move in the axial direction of the guide groove 105C, but cannot rotate.

One end of the piston 105 opposite to the screw shaft 102 is provided with a piston axial direction protrusion 105A, and a head of the piston axial direction protrusion 105A is provided with a piston abutting plane 105B. In the same principle, in order to make the stress more balanced during the abutting, the number of the piston axial convex parts 105A is two, the heads of the two piston axial convex parts 105A are respectively provided with a piston abutting plane 105B, and the piston abutting planes 105B are in one-to-one correspondence with the screw shaft abutting planes 102B. The two piston abutment planes 105B are coplanar and symmetrically arranged with respect to the center of the piston 105.

The utility model discloses a screw axis and camshaft joint control valve motion's theory of operation is:

the engine oil in the engine oil path (low-pressure oil path) of the engine can flow to the sliding sleeve cavity Q through the oil inlet 107 and the limiting oil hole 118. Under the action of the camshaft 101, the screw shaft 102 moves downwards, when the screw shaft 102 blocks the limiting oil hole 118 (at this time, due to the action of the one-way valve 108, the engine oil cannot flow out from the oil inlet hole 107), the sliding sleeve cavity Q becomes a closed cavity, the pressure of the hydraulic oil is increased, the piston 105 is pushed to move downwards, and the piston 105 pushes the valve to move downwards.

The linear actuator 117 controlled by the electronic control unit of the engine drives the rack 113 to move, so as to push the screw shaft 102 to rotate, and after the abutting plane 102B of the screw shaft is separated from the abutting plane 105B of the piston, because the screw shaft 102 is provided with the screw surface 102E, the relative position of the screw shaft 102 for plugging the limiting oil hole 118 can be changed by rotating the screw shaft 102, so that the stroke of the piston 105 is controlled, and further the lift of the valve is controlled. Fig. 8 shows the relationship between the valve lift and the crank angle (corresponding to the cam angle), and the outermost curve shows the valve opening curve under the condition of being controlled only by the cam surface when the screw axis abutting plane 102B abuts against the piston abutting plane 105B, at which the valve lift is maximized. The curves at the inner side are different valve opening curves obtained by adjusting the time when the screw shaft 102 blocks the limiting oil hole 118 by rotating the screw shaft 102.

In the return stroke, the hydraulic oil enters the sleeve chamber Q from the oil inlet 107 through the check valve 108, and rapidly returns the screw shaft 102 together with the return spring 104.

When the ECU of the engine is stopped and the power is off, under the action of the return spring 115, the rack 113 moves to the limit position limited by the limiting device 116, at this time, the position relation between the piston 105 and the screw shaft 102 is in the state shown in fig. 6, namely, the piston abutting plane 105B abuts against the screw shaft abutting plane 102B, the engine oil in the sliding sleeve cavity Q does not work, the cam and the valve are in a rigid connection state, the valve lift is completely controlled by the camshaft 1, and therefore the influence of the engine oil loss on the normal operation of the system is avoided.

The utility model discloses in, spacing oilhole 118 and piston top lean on plane 105B's relative position, decided that the screw axis top lean on plane 102B after breaking away from piston top lean on plane 105B, can whether touch the piston top at helicoid 102E and lean on just blocking up spacing oilhole 118 before plane 105B, and effective rapidly. As shown in fig. 2 and 3, the theoretical limit position G of the helicoid (indicated by the two-dot chain line) passes through the piston abutting plane edge point P, and in actual operation, the downward position of the helicoid 102E must not exceed the theoretical limit position G of the helicoid, otherwise it will collide with the piston abutting plane 105B, and therefore, the limit oil hole 118 should be located axially above the theoretical limit position G of the helicoid. In the circumferential direction, the distance from the limit oil hole 118 to the edge point P of the piston abutting plane is also as small as possible, so that after the screw shaft abutting plane 102B is separated from the piston abutting plane 105B, the screw shaft 102 can play a role of blocking the limit oil hole 118 along with the axial movement of the screw shaft 102 by rotating by an angle as small as possible. Fig. 3 shows an example of a better use effect of the limiting oil hole 118 located above the piston abutting end surface 105B and close to the edge point P of the piston abutting plane when the valve is in the closed state, and of course, the optimal position of the limiting oil hole 118 needs to be obtained according to analysis of motion mechanics, which is not described herein.

The utility model discloses in, figure 7 shows the example of a rack 113 simultaneously with 6 control gear 102A meshing, every control gear 102A corresponds a valve assembly, is applied to six jar engines promptly, the utility model discloses a design can be extended to 4 jar machines or 8 jar machines etc. the quantity of cylinder is unrestricted.

The utility model discloses in, be provided with thrust bearing 112 on control gear 102A's the terminal surface, be provided with wear pad 111 between thrust bearing 112 and the cam surface of camshaft 101, with reducing wear, and can lean on the distance between plane 105B and the screw axis top by plane 102B through the thickness adjustment piston top of wear pad 111, when the non-cam surface top of camshaft 101 leans on the screw axis 102 (or lean on through wear pad 111 and thrust bearing 112 top), distance between them is zero or is close to zero.

The utility model discloses in, sliding sleeve 103 is provided with second locating pin 120, in second locating pin 120 stretched into ring channel 102D, can restrict the axial displacement of screw axis 102 through second locating pin 120.

The present invention is not limited to the above embodiments, and all improvements based on the concept, principle, structure and method of the present invention will fall within the protection scope of the present invention.

Claims (10)

1. A fully variable electro-hydraulic valve system with a damping function, comprising:

a camshaft and a valve assembly;

the sliding sleeve is fixed relative to an engine, the screw shaft and the piston are respectively connected with the sliding sleeve in a sliding and sealing mode, an inner cavity between the screw shaft and the piston is called a sliding sleeve cavity, the return spring is clamped between the screw shaft and the piston, the piston abuts against the valve assembly, and the screw shaft is controlled by a cam surface of the camshaft in the axial direction;

the screw shaft is provided with a first end and a second end which are oppositely arranged, the first end is provided with a screw surface, the second end is in transmission connection with a gear rack mechanism, the gear rack mechanism comprises a control gear and a rack, the control gear is arranged at the second end of the screw shaft, and the rack is driven by a linear actuating mechanism controlled by an electric control unit of an engine;

the sliding sleeve is provided with an oil inlet hole and a limiting oil hole, the oil inlet hole and the limiting oil hole are respectively communicated with a low-pressure oil way of the engine, and a one-way valve is arranged on a connecting pipeline between the oil inlet hole and the low-pressure oil way of the engine; it is characterized in that the preparation method is characterized in that,

a stepped hole structure is arranged at the end part of the piston of the sliding sleeve, the stepped hole structure comprises a large hole and a small hole, the small hole is matched with the sliding sealing surface of the piston, a buffer ring is arranged in the large hole, the buffer ring is sleeved on the sliding sealing surface of the piston and is in sliding sealing fit with the inner peripheral surface of the large hole, and the buffer ring and the piston form a buffer cavity in the stepped hole; the peripheral surface of the outer end of the piston is provided with a flange which is used for colliding the buffer ring when a valve of the valve assembly is seated, the end part of the piston of the sliding sleeve is provided with a baffle, and when the valve of the valve assembly is closed, a buffer distance is reserved between the buffer ring and the baffle;

the sliding sleeve is provided with a buffer oil hole communicated with the buffer cavity, and the buffer oil hole is communicated with a low-pressure oil way of the engine through a throttling device.

2. The fully variable electro-hydraulic valve system with a damping function according to claim 1,

the screw shaft is provided with an annular groove, the annular groove is provided with an oil through hole, the oil through hole is communicated with the annular groove and the sliding sleeve cavity, and the oil inlet hole is constantly communicated with the annular groove in the movement process of the screw shaft;

the head of the spiral surface of the spiral shaft is provided with a spiral shaft abutting plane, one end of the piston, which is opposite to the spiral shaft, is provided with a piston axial protruding part, and the head of the piston axial protruding part is provided with a piston abutting plane;

the sliding sleeve is provided with a first positioning pin, the piston is provided with a guide groove extending along the axial direction, and the first positioning pin extends into the guide groove;

the limiting oil hole is arranged at a position which is blocked by the spiral shaft before the spiral surface touches the piston abutting plane;

the gear rack mechanism is further provided with a limiting device and a return spring, when the return spring enables the rack to move to the limit position limited by the limiting device, the piston abutting plane abuts against the spiral shaft abutting plane, and the valve lift of the valve assembly is controlled by the cam shaft.

3. The fully variable electro-hydraulic valve system with the buffering function according to claim 2, wherein a screw shaft axial protrusion is arranged at a first end of the screw shaft, the head of the screw shaft axial protrusion is provided with another screw shaft abutting plane, and the root of the screw planes meet the root of the screw shaft axial protrusion; the number of the piston axial protruding parts is two, the heads of the two piston axial protruding parts are respectively provided with a piston abutting plane, and the piston abutting planes correspond to the screw shaft abutting planes one by one.

4. The fully variable electro-hydraulic valve system with a damping function according to claim 3, wherein the two pistons abut against the same plane, and the two screw shafts abut against the same plane.

5. The fully variable electro-hydraulic valve system with a shock absorbing function according to claim 3, wherein two of the piston abutment planes are symmetrically disposed with respect to a center of the piston, and two of the screw axis abutment planes are symmetrically disposed with respect to a center of the screw axis.

6. The fully variable electro-hydraulic valve system with a damping function according to claim 1, wherein a thrust bearing is provided at the second end of the screw shaft, and a wear-resistant pad is provided between the thrust bearing and the cam surface of the camshaft.

7. The fully variable electro-hydraulic valve system with a damping function according to claim 1, wherein the control gear is connected with the screw shaft in a torque transmitting manner.

8. The fully variable electro-hydraulic valve system with a damping function according to claim 1, wherein the rack gear is simultaneously engaged with the control gears of a plurality of the screw shafts.

9. The fully variable electro-hydraulic valve system with a damping function according to claim 1, wherein the linear actuator is a linear motor or an actuator electromagnet or a cylinder or a hydraulic cylinder.

10. The fully variable electro-hydraulic valve system with a damping function according to claim 2, wherein the sliding sleeve is provided with a second positioning pin, and the second positioning pin extends into the annular groove.

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