Variable valve drive device for an engine

Abstract

The variable valve drive device of the engine comprises a rocker arm mechanism, a camshaft, a driving mechanism and a blocking mechanism. The rocker roller is slidable on the roller shaft to have two working positions. The camshaft is provided with adjacent first and second cams. The rocker arm mechanism is driven by the first or second cam respectively according to the working position of the rocker roller to make the engine have two valve lifts. A control cam is arranged on one side of the first or second cam. The control cam can drive the blocking mechanism to block the switching of the rocker roller in the part where the first and second cams are prohibited from switching and allow the switching in the part where the first and second cams are not prohibited from switching. The invention mechanically ensures that the rocker roller can only start switching in the allowed part, and the energization time of the electromagnetic valve does not need to be controlled by software or other sensors, thereby ensuring the consistency and reliability of the device.

Description

Technical Field

[0001] This invention relates to the field of engine technology, and in particular to a variable valve drive device for an engine. Background Technology

[0002] There are various known variable valve timing technologies for engines. These technologies achieve variable valve lift or valve timing through different structural designs and control methods, so as to enable the engine to obtain better performance or achieve special functions. One known type of variable valve timing technology is to set two cams with different profiles on the engine camshaft and make the valve drive mechanism switch between the two different cams as needed. This allows the engine to obtain two different valve lifts, thereby improving engine performance or achieving a certain special function such as engine braking.

[0003] Chinese patent CN110080849A discloses a camshaft and valve drive device for an engine. According to the application document disclosed in the patent, the device includes a camshaft, a rocker arm mechanism, and a control mechanism. The camshaft of the device has two adjacent cams for the rocker arm. The two cams have different profiles and have a section B that is the same as the base circle. The control mechanism of the device includes an actuator. The actuator pushes the rocker arm roller through a slot to switch from one cam to another to realize variable valve. For this type of variable valve device that switches the working position of the rocker arm roller, the switching process of the rocker arm roller must ensure that both cams are in the base circle portion to ensure that the roller can reliably achieve switching contact with different cams. If the switching occurs when either cam is not in the base circle portion, it will result in failure to switch or a sudden change in valve lift, causing valve system impact damage. The design of this patent successfully avoids the roller switching in the lift portion by setting a flange between the lift portions of the two cams to block the switching of the roller. Only the portion where both cams are in the base circle portion (section B) is left without a flange, and the rocker arm roller can switch in this area.

[0004] However, the variable valve drive device disclosed in CN110080849A also has obvious shortcomings. When the engine is running at high speed, the camshaft rotates at a very high speed, and the time that section B, where both cams are on the same base circle, passes the rocker arm roller is very short. The rocker arm roller can only achieve the maximum switching time if it starts switching when section B has just reached the roller position. If the camshaft rotates to the point where section B has already passed a large part of the rocker arm roller position before the roller starts switching (as shown in the attached figure), the problem is that the camshaft rotates to the point where section B has already passed the rocker arm roller position before the roller starts switching. Figure 1At this point, the base circle portion left for the roller to switch is relatively small. The rocker arm roller will not be able to switch completely to the other cam because the switching time is too short, which will cause the rocker arm roller to ride on the flange and damage the rocker arm mechanism. The specification of patent CN110080849A also mentions that the control mechanism of the device requires the engine ECU to determine the angle position of the cam based on the cam phase sensor. When the camshaft rotates to the point where the rocker arm roller has just entered or is about to enter the common base circle portion B of the two cams, the solenoid valve is energized to control the position of the rocker arm roller when it starts to move, so as to ensure that the rocker arm roller has the maximum switching time.

[0005] However, in practical applications, a connecting pipeline is required from the solenoid valve to the actuator. When the solenoid valve is energized, the actuator does not act immediately. The actuator needs to wait until the pressure in the pipeline exceeds the spring force before driving the rocker arm roller to begin switching. This requires a certain amount of time, i.e., the actuator response time. Therefore, to control the rocker arm roller to start switching as soon as it enters segment B, the energization time of the solenoid valve needs to be set with a certain lead time. Similarly, when the solenoid valve is de-energized, the action of the rocker arm roller returning due to the spring force also has a certain response time. The actuator needs to wait until the pressure in the pipeline drops below the spring force before driving the rocker arm roller to begin returning. The actuator's response time will change with the length of the connecting pipeline, the flow cross-section, and the internal volume. The solenoid valve itself has a certain response time. Inconsistencies in component performance can also cause variations in the solenoid valve's response time. When the camshaft rotates at high speed, the time it takes for segment B to pass the rocker arm roller is very short (sometimes only a few milliseconds). Even slight changes in actuator and solenoid valve response times can affect the position at which the rocker arm roller begins switching. Furthermore, variations in working pressure and temperature, as well as the consistency of actuator components, can also cause changes in response time. Therefore, in mass production, these changes in response time can significantly hinder product consistency control. It's difficult to avoid some products where large variations in response time or extreme operating environments can cause the rocker arm roller to fail to start switching at the designed position, leading to rocker arm mechanism failure. Secondly, when the camshaft phase sensor malfunctions, it may transmit incorrect phase signals to the ECU. This can cause the ECU to energize the solenoid valve at the wrong time, resulting in switching failure. In addition, since the engine ECU determines the timing of energizing the solenoid valve based on the cam phase signal, the camshaft angle produced by the same response time is different at different speeds. This requires the ECU to energize the solenoid valve according to different cam phase signals at different engine speeds, which requires the ECU software to add corresponding control logic, making the ECU software system more complex. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a variable valve drive device for an engine.

[0007] The variable valve drive device of the engine includes a rocker arm mechanism, a camshaft, a drive mechanism, and a blocking mechanism. The rocker arm mechanism has a rocker arm roller, which is rotatably mounted on a roller shaft. The rocker arm mechanism has a widened roller mounting space, and the rocker arm roller can slide left and right on the roller shaft, thereby giving the rocker arm roller two working positions.

[0008] The camshaft is provided with an adjacent first cam and a second cam. The position of the first cam corresponds to the first working position of the rocker arm roller, and the position of the second cam corresponds to the second working position of the rocker arm roller. The rocker arm mechanism is driven by the first cam or the second cam depending on the working position of the rocker arm roller. The first cam and the second cam have the same base circle diameter and have a section B, which is also a base circle, in the circumferential direction. A control cam is also provided on one side of the first cam or the second cam.

[0009] The driving mechanism includes a driving cylinder, which is a small air cylinder driven by compressed air. A driving piston is installed in the cylinder bore of the driving cylinder. A roller slot is installed on the piston rod of the driving piston. The roller slot is engaged with the rocker arm roller. The driving cylinder drives the rocker arm roller to switch between a first working position and a second working position through the roller slot installed on the piston rod.

[0010] The blocking mechanism includes a blocking rod and a blocking rod shaft. The blocking rod shaft is mounted on the drive cylinder, and the blocking rod is rotatably mounted on the blocking rod shaft. One end of the blocking rod contacts the control cam of the camshaft and is driven by the control cam to swing. The blocking rod achieves contact or discontinuation with the roller slot through swinging. When the blocking rod is in contact with the roller slot, the blocking rod prevents the roller slot from moving. When the blocking rod discontinues contact with the roller slot, the roller slot can drive the rocker arm roller to move under the action of the drive cylinder.

[0011] Furthermore, one end of the blocking rod is located near the roller slot, and the roller slot has a protrusion with two blocking end faces. A blocking pin is provided on the blocking rod. When the blocking rod approaches the roller slot, the outer surface of the blocking pin on the blocking rod contacts one of the blocking end faces on the roller slot, so that the blocking rod and the roller slot are in contact. When the blocking rod moves away from the roller slot under the drive of the control cam, the blocking pin on the blocking rod moves away from the blocking end face of the roller slot, so that the blocking rod and the roller slot are disengaged.

[0012] Furthermore, the blocking mechanism is provided with a blocking rod spring, which is mounted on the drive cylinder. The blocking rod spring contacts the blocking rod and exerts a force on the blocking rod. The force exerted by the blocking rod spring on the blocking rod ensures that one end of the blocking rod always remains in contact with the control cam.

[0013] Furthermore, within segment B, where the first and second cams on the camshaft are both base circles, there is a region S that the rocker arm roller cannot pass through. When the rocker arm roller begins to move within segment S under the action of the drive mechanism, the rocker arm roller cannot completely switch from the first working position to the second working position or completely return from the second working position to the first working position at the end of segment B. A switching prohibition portion is provided in the circumferential direction of the first and second cams, and the switching prohibition portion includes at least the region S that the rocker arm roller cannot pass through.

[0014] The control cam has the following relationship with the first and second cams: when the rocker arm roller is in the prohibited switching part between the first cam and the second cam, the control cam drives the blocking rod and makes the blocking rod contact the roller slot; when the rocker arm roller is in the non-prohibited switching part between the first cam and the second cam, the control cam drives the blocking rod and makes the blocking rod disengage from the roller slot.

[0015] Furthermore, a retaining ring is installed on the blocking rod shaft, which fixes the position of the blocking rod so that it cannot move axially.

[0016] Furthermore, a cylinder spring is installed on the drive cylinder of the drive mechanism, the air inlet of the drive cylinder is connected to the compressed air of the vehicle, the drive piston of the drive cylinder is pushed out by the compressed air of the vehicle, and is driven back by the cylinder spring.

[0017] Furthermore, during the switching process of the rocker arm roller, the end face of the blocking pin on the blocking rod that contacts the roller groove is spherical.

[0018] The beneficial effects of this invention are as follows: Compared with the prior art, the variable valve drive device for the engine provided by this invention provides a control cam and a blocking mechanism for each drive cylinder. In areas where rocker arm rollers are not allowed to start switching, the control cam drives the blocking mechanism to block the switching of rocker arm rollers. In areas where rocker arm rollers are allowed to start switching, the control cam drives the blocking mechanism to no longer block the switching of the rollers, allowing the rocker arm rollers to switch freely. This structurally ensures that the cam angle position when the rocker arm rollers start switching can only be within the allowed area. The starting position of the rocker arm rollers is no longer affected by the response time, and there is no need for the ECU to control the on / off timing of the solenoid valve based on the cam phase signal and engine speed. This invention completely controls the position of the rocker arm rollers when they start to move from a mechanical structure perspective, making the position control when the rocker arm rollers start to switch very simple and ensuring product consistency and reliability. Attached Figure Description

[0019] The accompanying drawings are provided to give a better understanding of the invention and are used together with the following detailed description to describe and explain the invention, but do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a schematic diagram of the camshaft rotating to segment B, which has already passed a large portion of the rocker arm roller position, as described in the background art of this invention.

[0021] Figure 2 This is a schematic diagram of the overall structure of the variable valve drive device of the engine of the present invention;

[0022] Figure 3 This is a schematic diagram of the camshaft structure of the variable valve drive device of the engine of the present invention;

[0023] Figure 4 This is a schematic diagram of section B and section S of the camshaft of the variable valve drive device of the engine of the present invention, where the two cams are both base circles.

[0024] Figure 5 This is a schematic diagram of the structure of the variable valve drive device of the engine of the present invention when the drive mechanism and the blocking mechanism are assembled together;

[0025] Figure 6 This is a partial cross-sectional view along the center of the drive cylinder of the variable valve drive device of the engine of the present invention;

[0026] Figure 7 This is a schematic diagram of the blocking mechanism of the variable valve drive device of the engine of the present invention;

[0027] Figure 8 This is a schematic diagram of the structure of the rocker arm roller of the variable valve drive device of the engine of the present invention when it is blocked;

[0028] Figure 9 This is a schematic diagram of the rocker arm roller of the variable valve drive device of the engine of the present invention when it is not blocked;

[0029] Figure 10 This is a schematic diagram of the structure of the variable valve drive device of the engine of the present invention when the rocker arm roller is blocked in the second working position;

[0030] Figure 11 This is a schematic diagram showing the rocker arm roller of the variable valve drive device of the engine of the present invention in contact with the blocking pin and the roller groove during the switching process.

[0031] Special Note: The shapes and relative positions of the first cam, second cam, and control cam on the camshaft in the accompanying drawings of this specification are merely schematic diagrams, intended only to illustrate how the blocking mechanism in this invention prevents the rocker arm roller from moving and allows it to move. They are somewhat arbitrary and do not represent the actual shape and relative position of the cams. In practice, the shape and position of the cams should be designed according to specific requirements. Detailed Implementation

[0032] The specific technical solutions adopted in the embodiments of the present invention will be described in detail and completely below with reference to the accompanying drawings. In the description of the present invention, unless otherwise stated, "multiple" means two or more. The terms "upper", "lower", "front", "rear", "left", "right", etc., used to indicate the orientation or positional relationship are only for the convenience of describing and explaining the orientation or positional relationship of the present invention based on the accompanying drawings. They should not be construed as the specific orientation or positional relationship that the device or element referred to must have, and do not constitute a limitation on the present invention.

[0033] Appendix Figure 2 A schematic diagram of the overall structure of the variable valve drive device of the engine of the present invention is shown. The variable valve drive device of the engine of the present invention includes a rocker arm mechanism 1, a camshaft 2, a drive mechanism 3, and a blocking mechanism 4. The rocker arm mechanism 1 has a rocker arm roller 11, which is rotatably mounted on a roller shaft 12. The rocker arm mechanism 1 has a widened roller mounting space, and the rocker arm roller 11 can slide left and right on the roller shaft 12, thereby having first and second working positions. The camshaft 2 is located below the rocker arm roller 11, and the cam on the camshaft 2 contacts the rocker arm roller 11. The rocker arm mechanism 1 is directly driven by the camshaft 2 to open or close the valve.

[0034] Appendix Figure 3This diagram shows the structure of the camshaft 2 of the variable valve drive device of the engine of the present invention. The camshaft 2 has adjacent first cams 21 and second cams 22. The position of the first cam 21 corresponds to the first working position of the rocker arm roller 11, and the position of the second cam 22 corresponds to the second working position of the rocker arm roller 11 (as shown in the attached diagram). Figure 2 As shown in the figure, the rocker arm mechanism 1 is driven by either the first cam 21 or the second cam 22 depending on the working position of the rocker arm roller 11, thereby enabling the engine to have two valve lifts. The first cam 21 and the second cam 22 have the same base circle diameter and have a section B, which is also a base circle in the circumferential direction (see attached figure). Figure 4 A control cam 23 is also provided on one side of the first cam 21 or the second cam 22.

[0035] Appendix Figure 5 and appendix Figure 6 The diagram shows a schematic of the structure of the variable valve drive device of the engine of the present invention when the drive mechanism 3 and the blocking mechanism 4 are assembled together. The drive mechanism 3 includes a drive cylinder 31, which is a small cylinder driven by compressed air. A drive piston 32 is installed in the cylinder bore of the drive cylinder 31. A roller slot 34 is installed on the piston rod of the drive piston 32, and the roller slot 34 is engaged with the rocker arm roller 11 (as shown in the attached diagram). Figure 2 As shown), a cylinder spring 35 is installed on the drive cylinder 31. The air inlet 36 of the drive cylinder 31 is connected to the compressed air of the vehicle. The drive piston 32 of the drive cylinder 31 is pushed out by the compressed air of the vehicle and pushed back by the cylinder spring 35. The drive cylinder 31 drives the rocker arm roller 11 to switch between the first working position and the second working position through the roller slot 34 installed on the piston rod.

[0036] Appendix Figure 7 This diagram shows the structure of the blocking mechanism 4 of the variable valve drive device of the engine of the present invention. The blocking mechanism 4 includes a blocking rod 41 and a blocking rod shaft 42. The blocking rod shaft 42 is mounted on the drive cylinder 31 (see attached diagram). Figure 5 The blocking rod 41 is a T-shaped metal plate with a central shaft hole. The blocking rod 41 is rotatably mounted on the blocking rod shaft 42 through the central shaft hole. The lower end of the blocking rod 41 contacts the control cam 23 of the camshaft 2 (see attached diagram). Figure 2 The control cam 23 drives the blocking rod 41 to swing, and the blocking rod 41 makes contact with or disengage from the roller slot 34 by swinging.

[0037] As attached Figure 5 Appendix Figure 6 and appendix Figure 7As shown, the middle end of the blocking rod 41 is located near the roller slot 34. A protrusion is provided at the lower end of the roller slot 34. The left and right sides of the protrusion are two blocking end faces 341 and 342. A blocking pin 43 is provided on the middle end of the blocking rod 41. The blocking mechanism is also provided with a blocking rod spring 44. The blocking rod spring 44 is installed in the mounting hole on the drive cylinder 31. The blocking rod spring 44 contacts the upper end of the blocking rod 41 and exerts a force on the blocking rod. The force exerted by the blocking rod spring 44 on the blocking rod 41 keeps the lower end of the blocking rod in contact with the control cam 23.

[0038] Appendix Figure 8 The diagram shows a schematic of the rocker arm roller 11 of the variable valve drive device of the engine of the present invention when it is blocked. When one middle end of the blocking rod 41 approaches the roller groove 34, the outer surface of the blocking pin 43 on the blocking rod contacts the blocking end face 341 on the roller groove 34, so that the blocking rod 41 and the roller groove 34 are in contact. At this time, the blocking rod 41 prevents the roller groove 34 from moving. Under the drive of the control cam 23, when one middle end of the blocking rod 41 moves away from the roller groove 34, as shown in the attached diagram... Figure 9 As shown, the blocking pin 43 on the blocking rod is away from the blocking end face 341 on the roller slot 34, so that the blocking rod 41 is disengaged from the roller slot 34. At this time, the roller slot 34 can drive the rocker arm roller 11 to move under the action of the drive cylinder 31.

[0039] Appendix Figure 8 With appendix Figure 9 The diagram shows the control of the rocker arm roller 11 by the stop rod 41 when the drive cylinder moves the rocker arm roller to the first working position, allowing the rocker arm roller 11 to move and remain stationary. Similarly, when the drive cylinder moves the rocker arm roller 11 to the second working position, as shown... Figure 10 As shown (the rocker arm mechanism and camshaft are not shown for easier observation), the blocking rod 41 controls the movable and immovable rocker arm roller 11 by the contact and disengagement of the blocking pin 43 with the blocking end face 342 on the roller slot. The movable and immovable areas of the rocker arm roller 11 are determined by the contour of the control cam 23.

[0040] Appendix Figure 4The diagram shows a schematic of sections B and S on the camshaft of the variable valve drive device of the engine of the present invention, where the two cams, first cam 21 and second cam 22, share the same base circle. Within section B, there is a region S through which the rocker arm roller 11 cannot pass. This region S has the following characteristics: because the switching of the rocker arm roller's working position requires a certain amount of time, at the maximum permissible switching speed, the time it takes for the camshaft to traverse section S is insufficient to meet the rocker arm roller's switching time requirement. That is, when the rocker arm roller begins to move within section S under the action of the drive mechanism, it cannot completely switch from the first working position to the second working position or completely return from the second working position to the first working position by the end of section B. A switching-prohibition section is provided in the circumferential direction of the first cam 21 and second cam 22. Since the rocker arm roller cannot completely switch to another working position when it begins to move within section S, the switching-prohibition section at least includes the region S through which the rocker arm roller cannot pass. Of course, when other parts of the first cam 21 and the second cam 22 (such as parts with lift) need to prevent the rocker arm roller from switching, they can all be set as parts that prevent switching. The range of the parts that prevent switching can be determined by controlling the contour design of the cam 23.

[0041] The control cam 23 has the following relationship with the first cam 21 and the second cam 22: when the rocker arm roller 11 is in the prohibited switching part between the first cam 21 and the second cam 22, the control cam 23 drives the blocking rod 41 and makes the blocking rod 41 contact the roller slot 34; when the rocker arm roller 11 is in the non-prohibited switching part between the first cam 21 and the second cam 22, the control cam 23 drives the blocking rod 41 and makes the blocking rod 41 disengage from the roller slot 34.

[0042] As described above, when the blocking rod prevents the roller slot from moving, the blocking rod will be subjected to a force from the roller slot. Therefore, a retaining spring 45 is also installed on the blocking rod shaft. The retaining spring 45 fixes the position of the blocking rod so that it cannot move axially, as shown in the attached figure. Figure 7 As shown.

[0043] The operation of the variable valve drive device of the engine of the present invention is as follows: During engine operation (e.g., when the rocker arm roller 11 is in the first working position), when it is necessary to switch the rocker arm roller to the second working position, the driver energizes the solenoid valve via a switch or by control of the engine ECU, allowing compressed air to enter the drive cylinder 31. When the driving pressure overcomes the cylinder spring force, the drive cylinder 31 pushes the rocker arm roller 11 through the roller slot 34 to begin switching. At this time, when the rocker arm roller 11 is in the prohibited switching part between the first cam 21 and the second cam 22, according to the design of the control cam 23 and the action of the stop rod spring 44, the stop rod 41 prevents the rocker arm roller 11 from moving, as shown in the attached figure. Figure 8 As shown, at this time, the rocker arm roller 11 cannot switch. As the camshaft 2 rotates, when the camshaft rotates to the point where the rocker arm roller is in the non-disabled switching position, the control cam 23 drives the stop rod 41 to disengage from the roller slot 34. At this time, the rocker arm roller 11 can freely switch to the second working position, as shown in the attached figure. Figure 9 As shown. Similarly, when the rocker arm roller 11 needs to return to the first working position, the blocking rod also prevents the rocker arm roller 11 from moving in the prohibited switching part of the first cam 21 and the second cam 22. Only when the camshaft rotates to the rocker arm roller in the non-prohibited switching part can the rocker arm roller freely return to the first working position under the action of the cylinder spring force.

[0044] Typically, the non-prohibited switching portion of the first cam 21 and the second cam 22 can be set as the portion within segment B of the base circle of both cams, excluding segment S. Since the blocking mechanism needs to prevent the rocker arm roller from moving during segment S, the rocker arm roller, during the switching process, such as... Figure 11 As shown, when the camshaft rotates to the point where the rocker arm roller enters segment S, the middle end of the blocking rod approaches the roller slot 34 under the action of the blocking rod spring 44. Since the rocker arm roller has not yet fully switched to the other working position, the end face of the blocking pin 43 on the blocking rod 41 will contact the protruding part of the roller slot 34. Only when the rocker arm roller 11 has fully switched to the other working position will the blocking pin of the blocking rod 41 enter the other blocking end face of the roller slot to prevent the roller slot from moving. Figure 10 As shown. Because the spring force of the stop bar spring is small, the contact between the stop pin and the roller slot during the switching process will not affect the switching of the roller. By designing the end face of the stop pin that contacts the roller slot as a spherical surface, the friction between the stop pin and the roller slot can be further reduced.

[0045] As can be seen from the above description, the variable valve drive device of the engine of the present invention ensures that the rocker arm roller can only start switching within the allowable range by controlling the action of the cam and the blocking mechanism. In any area that may cause switching failure, the rocker arm roller is blocked and cannot switch. The present invention guarantees the reliability of rocker arm roller switching from a mechanical structure perspective. It does not require software or other sensors to control the energization time of the solenoid valve, and avoids the influence of the response time of the drive mechanism and solenoid valve or the cam phase signal error on the start switching time of the rocker arm roller, thus ensuring the consistency and reliability of the device operation.

[0046] It should be noted that the above embodiments are merely preferred embodiments used to illustrate the design scheme and principle of the present invention, and should not be construed as limiting the present invention. For those skilled in the art, further modifications can be made to the technical solutions described in the above embodiments, or some technical features can be replaced or combined, etc., without departing from the concept of the present invention. For example, for different engine structures, the structural form and blocking method of the blocking rod can be different. The blocking rod can also be designed as a tappet structure that is directly driven by the control cam to perform reciprocating motion to control the movement of the rocker arm roller. All of these should be considered within the scope of protection of the present invention.

Claims

1. A variable valve drive device for an engine, comprising a rocker arm mechanism, a camshaft, a drive mechanism, and a blocking mechanism, characterized in that: The rocker arm mechanism includes a rocker arm roller, which is rotatably mounted on a roller shaft. The rocker arm mechanism has a widened roller mounting space, and the rocker arm roller can slide left and right on the roller shaft, thus allowing the rocker arm roller to have first and second working positions. The camshaft has adjacent first and second cams. The position of the first cam corresponds to the first working position of the rocker arm roller, and the position of the second cam corresponds to the second working position of the rocker arm roller. The rocker arm mechanism is driven by either the first cam or the second cam depending on the working position of the rocker arm roller. The first cam and the second cam have the same base circle diameter and a segment B, which is also a base circle, in the circumferential direction. A control cam is also provided on one side of the first cam or the second cam. The driving mechanism includes a driving cylinder, which is a small air cylinder driven by compressed air. A driving piston is installed in the cylinder bore of the driving cylinder. A roller slot is installed on the piston rod of the driving piston. The roller slot engages with the rocker arm roller. The driving cylinder drives the rocker arm roller to switch between a first working position and a second working position through the roller slot installed on the piston rod. The blocking mechanism includes a blocking rod and a blocking rod shaft. The blocking rod shaft is mounted on the drive cylinder, and the blocking rod is rotatably mounted on the blocking rod shaft. One end of the blocking rod contacts the control cam of the camshaft and is driven by the control cam to swing. The blocking rod achieves contact or discontinuation with the roller slot through swinging. When the blocking rod is in contact with the roller slot, the blocking rod prevents the roller slot from moving. When the blocking rod discontinues contact with the roller slot, the roller slot can drive the rocker arm roller to move under the action of the drive cylinder.

2. The variable valve drive device for an engine according to claim 1, characterized in that: One end of the blocking rod is located near the roller slot. The roller slot has a protrusion with two blocking end faces, left and right. A blocking pin is provided on the blocking rod. When the blocking rod approaches the roller slot, the outer surface of the blocking pin on the blocking rod contacts one of the blocking end faces on the roller slot, so that the blocking rod and the roller slot are in contact. When the blocking rod moves away from the roller slot under the drive of the control cam, the blocking pin on the blocking rod moves away from the blocking end face of the roller slot, so that the blocking rod and the roller slot are disengaged.

3. The variable valve drive device for an engine according to claim 1, characterized in that: The blocking mechanism is equipped with a blocking rod spring, which is mounted on the drive cylinder. The blocking rod spring contacts the blocking rod and exerts a force on the blocking rod. The force exerted by the blocking rod spring on the blocking rod ensures that one end of the blocking rod always remains in contact with the control cam.

4. The variable valve drive device for an engine according to claim 1, characterized in that: in Within segment B, where the first and second cams on the camshaft share the same base circle, there is a section S in which the rocker arm roller cannot pass. When the rocker arm roller begins to move within section S under the action of the drive mechanism, it cannot completely switch from the first working position to the second working position or completely return from the second working position to the first working position at the end of segment B. A switching-prevention section is provided circumferentially on the first and second cams, and this switching-prevention section at least includes the section S in which the rocker arm roller cannot pass. The control cam has the following relationship with the first and second cams: when the rocker arm roller is in the prohibited switching part between the first cam and the second cam, the control cam drives the blocking rod and makes the blocking rod contact the roller slot; when the rocker arm roller is in the non-prohibited switching part between the first cam and the second cam, the control cam drives the blocking rod and makes the blocking rod disengage from the roller slot.

5. The variable valve drive device for an engine according to claim 1, characterized in that: A retaining ring is installed on the shaft of the blocking rod, which fixes the position of the blocking rod so that it cannot move axially.

6. The variable valve drive device for an engine according to claim 1, characterized in that: A cylinder spring is installed on the drive cylinder of the drive mechanism. The air inlet of the drive cylinder is connected to the compressed air of the vehicle. The drive piston of the drive cylinder is pushed out by the compressed air of the vehicle and pushed back by the cylinder spring.

7. The variable valve drive device for an engine according to claim 2, characterized in that: During the switching process of the rocker arm roller, the end face of the blocking pin on the blocking rod that contacts the roller groove is spherical.

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