Variable valve actuation device for engine

Abstract

A variable valve actuation device for an engine includes a rocker arm mechanism, a camshaft, an actuation mechanism and a blocking mechanism. The rocker arm roller can slide on a roller shaft so as to have two operating positions, a first cam and a second cam which are adjacent are provided on the camshaft, the rocker arm mechanism is actuated, based on the different operating positions of the rocker arm roller, by the first cam or the second cam, respectively, to enable the engine to have two valve lifts, a control cam is further provided on one side of the first cam or the second cam, the control cam can actuate the blocking mechanism, and the rocker arm roller is blocked from switching in a switching prohibited portion of the first cam and the second cam, and is allowed to switching in a non-switching prohibited portion.

Claims

1. A variable valve actuation device for an engine, the variable valve actuation device comprising: a camshaft including a first cam, a second cam, and a control cam; a rocker arm mechanism including: an extended roller shaft, and a rocker arm roller rotatably mounted to the roller shaft, the rocker arm roller configured to slide axially along the roller shaft so as to engage the first cam when in a first operating position, and engage the second cam when in a second operating position; an actuation mechanism associated with the rocker arm mechanism, the actuation mechanism including: a pneumatically-controlled actuation cylinder defining a cylinder hole, an actuating piston arranged in the cylinder hole, and a roller shift fork coupled to the actuating piston, the roller shift fork configured to axially flank the rocker arm roller so as to effectuate a switching of the rocker arm roller between the first and second operating positions when the actuation cylinder actuates the actuating piston; and a blocking mechanism coupled to the actuation mechanism, the blocking mechanism including: a blocking rod shaft mounted to the actuation cylinder, and a blocking rod pivotally mounted to the blocking rod shaft so as to engage the control cam, the control cam configured to cause the blocking rod to intermittently engage the roller shift fork such that (i) the switching of the rocker arm roller is prevented when the blocking rod is in contact with the roller shift fork, and (ii) the switching of the rocker arm roller is enabled when the blocking rod is out of contact with the roller shift fork.

2. The variable valve actuation device according to claim 1, wherein: the roller shift fork includes a first blocking end surface and a second blocking end surface, and the blocking rod includes a blocking pin such that the switching of the rocker arm roller is prevented when a cylindrical surface of the blocking pin is in contact with the first blocking end surface or the second blocking end surface.

3. The variable valve actuation device according to claim 2, wherein: the blocking pin includes a spherical end surface configured to engage the roller shift fork when the blocking rod is brought into contact with the roller shift fork during the switching of the rocker arm roller.

4. The variable valve actuation device according to claim 1, wherein: the blocking mechanism further includes a blocking rod spring pressed between the blocking rod and the actuation cylinder so as to maintain the blocking rod in contact with the control cam at all times.

5. The variable valve actuation device according to claim 1, wherein: the switching of the rocker arm roller is enabled when the rocker arm roller is within a switching portion corresponding to an angular range of the camshaft in which a base circle region of the first cam coincides with a base circle region of the second cam, the switching portion includes a switching prohibited portion corresponding to an angular range within the switching portion which is insufficient for the switching of the rocker arm roller to be initiated and completed before the rocker arm roller reaches an end of the switching portion, and the control cam is shaped such that (i) the blocking rod is moved out of contact with the roller shift fork when the rocker arm roller enters the switching portion, and (ii) the blocking rod is brought into contact with the roller shift fork when the rocker arm roller reaches the switching prohibited portion so as to prevent the switching of the rocker arm roller from being initiated within the switching prohibited portion.

6. The variable valve actuation device according to claim 1, wherein: the blocking mechanism further includes a circlip mounted to the blocking rod shaft so as to prevent axial movement of the blocking rod along the blocking rod shaft.

7. The variable valve actuation device according to claim 1, wherein: the actuation mechanism further includes a cylinder spring mounted to the actuation cylinder so as to bias the actuating piston into the cylinder hole, and the actuation cylinder includes an air inlet configured to selectively convey compressed air into the cylinder hole so as to push the actuating piston out of the cylinder hole.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings are used to provide a better understanding of the present application, and are used with the following specific embodiments to describe and explain the present application, but do not constitute a limitation of the present application. In the drawings:

(2) FIG. 1 is a schematic diagram where a camshaft as described in the background of the present application rotates to a point that the rocker arm roller has passed through a larger portion of the segment B;

(3) FIG. 2 is an overall structural schematic diagram of the variable valve actuation device for an engine of the present application;

(4) FIG. 3 is a structural schematic diagram of the camshaft of the variable valve actuation device for the engine of the present application;

(5) FIG. 4 is a schematic diagram of the segment B and the segment S where two cams on the camshaft of the variable valve actuation device for the engine of the present application both are in base circle parts thereof;

(6) FIG. 5 is a structural schematic diagram where the actuation mechanism and a blocking mechanism of the variable valve actuation device for the engine of the present application are assembled together;

(7) FIG. 6 is a partial sectional view of the actuation mechanism and the blocking mechanism of the variable valve actuation device for the engine of the present application taken along the center of the actuation cylinder;

(8) FIG. 7 is a structural schematic diagram of the blocking mechanism of the variable valve actuation device for the engine of the present application;

(9) FIG. 8 is a structural schematic diagram where the rocker arm roller of the variable valve actuation device for the engine of the present application is blocked;

(10) FIG. 9 is a structural schematic diagram where the rocker arm roller of the variable valve actuation device for the engine of the present application is not blocked;

(11) FIG. 10 is a structural schematic diagram where the rocker arm roller of the variable valve actuation device for the engine of the present application is blocked when it is at the second operating position; and

(12) FIG. 11 is a schematic diagram where the blocking pin is in contact with a roller shift fork during the switching of the rocker arm roller of the variable valve actuation device for the engine of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(13) The specific technical solutions employed in the present embodiments are clearly and completely described below with reference to the drawings. In the description of the present application, unless otherwise specified, plurality means two or more, and the orientation or positional relationship indicated by terms such as on, under, front, back, left, right used herein are only for the convenience of description and explanation of the present application based on the orientation or positional relationship shown in the drawings of the present application. The orientation or positional relationship shown in the figures should not be understood as a particular orientation or positional relationship that the referred device or element must have, and does not constitute a limitation of the present application.

(14) Special note: in the drawings of the present specification, the shapes and relative positions of the first cam, the second cam and the control cam on the camshaft are only schematic diagrams, are only for explaining how the blocking mechanism of the present application can stop the rocker arm roller from moving and allow the rocker arm roller to move, and have certain randomness so that do not represent the shapes and relative positions of the actual cams, so the shapes and positions of the cams should be designed according to specific requirements in practice.

(15) FIG. 2 shows an overall structural schematic diagram of a variable valve actuation device for an engine of the present application, which includes a rocker arm mechanism 1, a camshaft 2, an actuation mechanism 3, and a blocking mechanism 4. The rocker arm mechanism 1 is provided with a rocker arm roller 11, the rocker arm roller 11 is rotatably installed on a roller shaft 12, the rocker arm mechanism 1 is provided with a widened roller mounting space, and the rocker arm roller 11 can slide left and right on the roller shaft 12 to enable the rocker arm roller to have a first operating position and a second operating position. The camshaft 2 is positioned below the rocker arm roller 11, a cam on the camshaft 2 is in contact with the rocker arm roller 11, and the rocker arm mechanism 1 is directly actuated by the camshaft 2 to open or close the valve.

(16) FIG. 3 shows a structural schematic diagram of the camshaft 2 of the variable valve actuation device for the engine of the present application, where a first cam 21 and a second cam 22 which are adjacent are provided on the camshaft 2, a position of the first cam 21 corresponds to the first operating position of the rocker arm roller 11, a position of the second cam 22 corresponds to the second operating position of the rocker arm roller 11 (as shown in FIG. 2), the rocker arm mechanism 1 is actuated, based on the different operating positions of the rocker arm roller 11, by the first cam 21 or the second cam 22, respectively, to enable the engine to have two valve lifts, the first cam 21 and the second cam 22 have a same diameter in base circle parts thereof and have a segment B in a circumferential direction where the two cams both are in base circle parts thereof (see FIG. 4), and a control cam 23 is further provided on one side of the first cam 21 or the second cam 22.

(17) FIG. 5 and FIG. 6 show structural schematic diagrams where the actuation mechanism 3 and the blocking mechanism 4 of the variable valve actuation device for the engine of the present application are assembled together. The actuation mechanism 3 includes a actuation cylinder 31, the actuation cylinder 31 is a small cylinder actuated by compressed air, a actuating piston 32 is installed in a cylinder hole of the actuation cylinder 31, a roller shift fork 34 is installed on a piston rod of the actuating piston 32, the rocker arm roller 11 is held by the roller shift fork 34 (as shown in FIG. 2), a cylinder spring 35 is installed on the actuation cylinder 31, an air inlet 36 of the actuation cylinder 31 is in communication with compressed air of a vehicle, the actuating piston 32 of the actuation cylinder 31 is pushed out by the compressed air of the vehicle and is actuated back by the cylinder spring 35, and the actuation cylinder 31 actuates the rocker arm roller 11 to switch between the first operating position and the second operating position through the roller shift fork 34 installed on the piston rod.

(18) FIG. 7 shows a structural schematic diagram of the blocking mechanism 4 of the variable valve actuation device for the engine of the present application, where the blocking mechanism 4 includes a blocking rod 41 and a blocking rod shaft 42, the blocking rod shaft 42 is installed on the actuation cylinder 31 (see FIG. 5), the blocking rod 41 is a metal plate-shaped part with a shaft hole in the middle and having a shape of T, the blocking rod 41 is rotatably installed on the blocking rod shaft 42 through the middle shaft hole, a lower end of the blocking rod 41 is in contact with control cam 23 of the camshaft 2 (see FIG. 2) and is actuated by the control cam 23 to swing, and the blocking rod 41 is in contact with or out of contact with the roller shift fork 34 by the swing.

(19) As shown in FIG. 5, FIG. 6 and FIG. 7, one end of the middle of the blocking rod 41 is positioned close to the roller shift fork 34, the lower end of the roller shift fork 34 is provided with one protrusion, surfaces at left and right sides of the protrusion are the two blocking end surfaces 341 and 342, a blocking pin 43 is provided on the end of the middle of the blocking rod 41, the blocking mechanism is further provided with a blocking rod spring 44, the blocking rod spring 44 is installed in a mounting hole on the actuation cylinder 31, the blocking rod spring 44 is in contact with the upper end of the blocking rod 41 and generates an acting force on the blocking rod, and the acting force of the blocking rod spring 44 on the blocking rod 41 maintains the lower end of the blocking rod in contact with the control cam 23 at all times.

(20) FIG. 8 shows a structural schematic diagram where the rocker arm roller 11 of the variable valve actuation device for the engine of the present application is blocked. When the end of the middle of the blocking rod 41 is close to the roller shift fork 34, the outer circumferential surface of the blocking pin 43 on the blocking rod is in contact with the blocking end surface 341 on the roller shift fork 34 such that the blocking rod 41 is in contact with the roller shift fork 34. At this time, the blocking rod 41 blocks the movement of the roller shift fork 34. When the end of the middle of the blocking rod 41 is far away from the roller shift fork 34 under the actuation of the control cam 23, as shown in FIG. 9, the blocking pin 43 on the blocking rod is far away from the blocking end surface 341 on the roller shift fork 34 such that the blocking rod 41 is out of contact with the roller shift fork 34. At this time, the roller shift fork 34 can drive the rocker arm roller 11 to move under the action of the actuation cylinder 31.

(21) FIG. 8 and FIG. 9 show schematic diagrams where the blocking rod 41 controls the rocker arm roller 11 to be movable or unmovable when the actuation cylinder keeps the rocker arm roller to be in the first operating position. Similarly, when the actuation cylinder switches the rocker arm roller 11 to the second operating position, as shown in FIG. 10 (for the convenience of viewing, the rocker arm mechanism and the camshaft not shown), the blocking rod 41 also controls the rocker arm roller 11 to be movable or unmovable, by making the blocking pin 43 be in contact with and out of contact with the blocking end surface 342 on the roller shift fork. The region where the rocker arm roller 11 is movable or unmovable is determined by the profile of the control cam 23.

(22) FIG. 4 shows a schematic diagram of a segment B and a segment S where two cams on the camshaft of the variable valve actuation device for the engine of the present application both are in base circle parts thereof. In the segment B where the first cam 21 and the second cam 22 on the camshaft 2 both are in base circle parts thereof, the segment S where the rocker arm roller 11 cannot be completely switched is existed. The segment S has the following features: at the highest rotational speed allowing the rocker arm roller to be switched, the time it takes for the camshaft to make the rocker arm roller pass through the segment S cannot meet the requirement of the switching time of the rocker arm roller, because a certain time is needed for switching the operating positions of the rocker arm roller, that is when the rocker arm roller starts to move in the segment S under the action of the actuation mechanism, the rocker arm roller cannot be completely switched from the first operating position to the second operating position or completely returned from the second operating position to the first operating position at the end point of the segment B. A switching prohibited portion is provided in a circumferential direction of the first cam 21 and the second cam 22, and the switching prohibited portion at least includes the segment S where the rocker arm roller cannot be completely switched, because the rocker arm roller cannot be completely switched to the other operating position when the rocker arm roller starts to move in the segment S. Of course, the other portion (e.g., a portion with lift) of the first cam 21 and the second cam 22 can be provided as the switching prohibited portion when the other portion needs the rocker arm roller to be prohibited from switching, and the range of the switching prohibited portion may be determined by the profile design of the control cam 23.

(23) 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 switching prohibited portion of the first cam 21 and the second cam 22, the control cam 23 actuates the blocking rod 41 and brings the blocking rod 41 into contact with the roller shift fork 34, and when the rocker arm roller 11 is in a non-switching prohibited portion of the first cam 21 and the second cam 22, the control cam 23 actuates the blocking rod 41 and brings the blocking rod 41 out of contact with the roller shift fork 34.

(24) As can be known from the above, when the blocking rod blocks the roller shift fork from moving, the blocking rod will be subjected to an acting force from the roller shift fork, therefore, the circlip 45 is further installed on the blocking rod shaft, and the circlip 45 fixes the position of the blocking rod so that the blocking rod cannot move axially, as shown in FIG. 7.

(25) The variable valve actuation device for the engine of the present application has the following operating process: during engine operation (for example, when the rocker arm roller 11 is at the first operating position), when it is needed to switch the rocker arm roller to the second operating position, the driver energizes the solenoid valve through a switch or under the control of the ECU for the engine to allow compressed air to enter the actuation cylinder 31; when the compressed air pressure overcomes the cylinder spring force, the actuation cylinder 31 pushes the rocker arm roller 11 through the roller shift fork 34 to start to switch; at this time, when the rocker arm roller 11 is in the switching prohibited portion of the first cam 21 and the second cam 22, the blocking rod 41 stops the rocker arm roller 11 from moving according to the design of the control cam 23 and the action of the blocking rod spring 44, as shown in FIG. 8, such that the rocker arm roller 11 cannot switch; and as the camshaft 2 rotates, the control cam 23 actuates the blocking rod 41 to be out of contact with the roller shift fork 34 when the camshaft rotates to the region where the rocker arm roller is in the non-switching prohibited portion, such that the rocker arm roller 11 is now free to switch to the second operating position, as shown in FIG. 9. Similarly, when it is needed to return the rocker arm roller 11 to the first operating position, the blocking rod also stops the rocker arm roller 11 from moving in the switching prohibited portion of the first cam 21 and the second cam 22, and the rocker arm roller can be free to return to the first operating position under the action of the cylinder spring force, only when the camshaft rotates to the region where the rocker arm roller is in the non-switching prohibited portion.

(26) Generally, the non-switching prohibited portion of the first cam 21 and the second cam 22 may be provided as a portion within segment B, where the two cams both are in base circle parts thereof, but not the segment S. Since the blocking mechanism needs to block the rocker arm roller from moving in the segment S, during the switching of the rocker arm roller, as shown in FIG. 11, and when the camshaft rotates to a point that the rocker arm roller enters the segment S, the end of the middle of the blocking rod approaches the roller shift fork 34 under the action of the blocking rod spring 44. At this time, the rocker arm roller is not completely switched to the other operating position, so that the end surface of the blocking pin 43 on the blocking rod 41 will be in contact with the protrusion of the roller shift fork 34. The blocking pin of the blocking rod 41 does not enter the blocking end surface in the other side of the roller shift fork to block the roller shift fork from moving until the rocker arm roller 11 is completely switched to the other operating position, as shown in FIG. 10. Because the spring force of the blocking rod spring is small, the contact between the blocking pin and the roller shift fork does not affect the switching of the roller in the switching process. The friction force between the blocking pin and the roller shift fork can be further reduced by designing the end surface of the blocking pin which is in contact with the roller shift fork as a spherical surface.

(27) According to the above description, with the control cam and the blocking mechanism, the variable valve actuation device for the engine of the present application ensures that the rocker arm roller can only start to switch within an allowable range, and that the rocker arm roller can be blocked from switching in any region where it may causes switching failure. The present application guarantees the reliability of the rocker arm roller switching from a mechanical structure perspective, eliminates a need for software or other sensors to control the energization time of the solenoid valve, avoids the impact of the response time of the actuation mechanism and the solenoid valve or errors in the cam position signal on the timing of beginning of the rocker arm roller switching, and ensures the consistency and reliability of the operation of the mechanism.

(28) It should be noted that, the above embodiments are only preferred embodiments adopted to illustrate the design and principle of the present application, and should not be understood as limitations of the present application. It will be apparent to those skilled in the art that the technical solutions described in the above embodiments may be further modified, or some technical features may be replaced, combined, etc. without departing from the concept of the present application. As examples, the structural form and the blocking way of the blocking rod may be different for different engine structures, and the blocking rod may also be designed as a tappet structure which is directly actuated by the control cam to reciprocate to control the movement of the rocker arm roller, which should be regarded as the protection scope of the present application.