Variable valve system

Abstract

To actualize smooth switching between the connected state and the disconnected state of a plurality of rocker arms.SOLUTION: In a variable valve system (30), there are provided a switching mechanism (55) for connecting / disconnecting the plurality of rocker arms with hydraulic pressure, and an oil control valve (71) for controlling the hydraulic pressure on the switching mechanism. The plurality of rocker arms are connected to one another with the forward movement of a hydraulic piston (61) of the switching mechanism, and the plurality of rocker arms are disconnected from one another with the backward movement of the hydraulic piston. First and second oil passages (81, 85) extend from the oil control valve to the hydraulic piston. Part of the first oil passage is formed by an oil groove (83) which passes oil in the predetermined rotational phase of a cam shaft. The second oil passage is closed in the middle of the backward movement of the hydraulic piston, and a bypass passage (86) is formed to bypass the oil groove when the second oil passage is closed.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a variable valve operating device. [Background technology]

[0002] Conventionally, a variable valve mechanism that switches valve operation by connecting multiple rocker arms is known (see, for example, Patent Document 1). In the variable valve mechanism described in Patent Document 1, a pair of cams with different lift amounts are formed on a camshaft, and a pair of rocker arms are provided corresponding to the pair of cams. A switching mechanism is connected to the pair of rocker arms, and hydraulic pressure is applied to the switching mechanism to switch between a connected state and a disconnected state of the pair of rocker arms. The cam that lifts the valves is switched when the pair of rocker arms are connected and disconnected, changing the valve lift amount. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-264199 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned variable valve mechanism, the pair of rocker arms are connected regardless of the rotational phase of the camshaft. Depending on the rotational phase of the camshaft, the valve lift may prevent the pair of rocker arms from connecting. Even if the pair of rocker arms are connected while avoiding the valve lift, there is a risk that the pair of rocker arms may not be able to be separated smoothly.

[0005] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a variable valve mechanism that can smoothly switch between a connected state and a disconnected state of a plurality of rocker arms. [Means for solving the problem]

[0006] 1 is a block diagram showing a variable valve mechanism for a variable valve gear in a cylinder head according to an embodiment of the present invention; a variable valve gear capable of changing a valve lift amount in a cylinder head, the variable valve gear comprising: a camshaft having a plurality of cams with different valve lift amounts formed thereon; a plurality of rocker arms that move a valve by abutting against the plurality of cams; a switching mechanism that hydraulically connects and separates the plurality of rocker arms; and an oil control valve that controls the hydraulic pressure for the switching mechanism; the switching mechanism has a hydraulic piston that moves back and forth by hydraulic pressure, the plurality of rocker arms are connected as the hydraulic piston moves forward and the plurality of rocker arms are separated as the hydraulic piston moves backward; a first oil passage and a second oil passage extend from the oil control valve to the hydraulic piston, a portion of the first oil passage is formed by an oil groove that allows oil to pass at a predetermined rotational phase of the camshaft; the second oil passage is opened while the hydraulic piston is moving forward and closed while the hydraulic piston is moving backward; and a bypass passage is formed to bypass the oil groove when the second oil passage is closed, thereby solving the above-mentioned problems. Effect of the Invention

[0007] According to a variable valve train according to one aspect of the present invention, when oil is supplied to the hydraulic piston from the oil control valve, the hydraulic piston advances due to the hydraulic pressure in the first oil passage at a predetermined rotational phase of the camshaft. When the second oil passage is opened while the hydraulic piston is advancing, and the multiple rocker arms are connected, the connected state is maintained by the hydraulic pressure in the second oil passage. On the other hand, when oil is discharged from the hydraulic piston to the oil control valve, the hydraulic pressure in the first and second oil passages is released, and the hydraulic piston retreats. When the hydraulic piston retreats, the second oil passage is closed, and the oil groove of the first oil passage does not allow oil to pass therethrough except at a predetermined rotational phase of the camshaft. At this time, the multiple rocker arms are smoothly separated by the oil being continuously discharged from the hydraulic piston through a bypass passage that bypasses the oil groove. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a right side view of the engine and the body frame of the embodiment. [Diagram 2] FIG. 2 is a right side view of the upper part of the engine with the cylinder head cover removed according to the embodiment. [Diagram 3] FIG. 2 is a schematic top view of the variable valve device of the present embodiment. [Figure 4] 6 is a diagram showing an example of a switching operation of a cam of a variable valve gear of Comparative Example 1. [Diagram 5] 11 is a diagram showing an example of a switching operation of a cam of a variable valve gear of Comparative Example 2. [Figure 6] 1 is a schematic diagram of a variable valve device according to an embodiment of the present invention; [Figure 7] FIG. 2 is a schematic diagram of an actuation passage and a direct passage in the present embodiment. [Figure 8] FIG. 2 is a perspective view of a hydraulic piston according to the present embodiment. [Figure 9] 5A to 5C are explanatory diagrams of a coupling operation of the variable valve operating device of the present embodiment. [Figure 10] 5A to 5C are explanatory diagrams of a separation operation of the variable valve operating device of the present embodiment. [Figure 11] FIG. 13 is a perspective view of a hydraulic piston according to a first modified example. [Figure 12] FIG. 13 is a bottom view of the upper housing of the modified example 2-4. [Figure 13] 13A and 13B are top and bottom views of a cam housing of modified example 2-4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A variable valve gear according to one aspect of the present invention is provided in a cylinder head and changes a valve lift amount. A plurality of cams with different valve lift amounts are formed on a camshaft, and a plurality of rocker arms that move the valves are in contact with the plurality of cams. The plurality of rocker arms are hydraulically connected and separated by a switching mechanism, and the hydraulic pressure for the switching mechanism is controlled by an oil control valve. A hydraulic piston of the switching mechanism advances and retreats by hydraulic pressure, and the plurality of rocker arms are connected by the advancement of the hydraulic piston, and the plurality of rocker arms are separated by the retreat of the hydraulic piston. A first oil passage and a second oil passage extend from the oil control valve to the hydraulic piston. A part of the first oil passage becomes an oil groove through which oil passes at a predetermined rotation phase of the camshaft, and when the second oil passage is blocked, the oil groove is bypassed by a bypass passage. The second oil passage is opened during the advancement of the hydraulic piston and closed during the retreat of the hydraulic piston. When oil is supplied to the hydraulic piston from the oil control valve, the hydraulic piston advances by the hydraulic pressure of the first oil passage at a predetermined rotation phase of the camshaft. When the second oil passage is opened while the hydraulic piston is moving forward, and the multiple rocker arms are connected, the connected state is maintained by the hydraulic pressure in the second oil passage. On the other hand, when oil is discharged from the hydraulic piston to the oil control valve, the hydraulic pressure in the first and second oil passages is released and the hydraulic piston moves backward. When the hydraulic piston moves backward, the second oil passage is closed, and the oil groove in the first oil passage does not allow oil to pass except at a specified rotation phase of the camshaft. At this time, oil continues to be discharged from the hydraulic piston through a bypass passage that bypasses the oil groove, allowing the multiple rocker arms to be smoothly separated. EXAMPLES

[0010] The saddle-type vehicle of this embodiment will be described below with reference to the accompanying drawings. Fig. 1 is a right side view of the engine and body frame of this embodiment. Fig. 2 is a right side view of the upper part of the engine with the cylinder head cover of this embodiment removed. Fig. 3 is a schematic top view of the variable valve gear of this embodiment. In the following drawings, the arrow Fr indicates the front of the vehicle, the arrow Re indicates the rear of the vehicle, the arrow L indicates the left side of the vehicle, and the arrow R indicates the right side of the vehicle.

[0011] As shown in Fig. 1, a saddle-type vehicle is configured by mounting various parts such as an engine 20 and an electrical system on a cradle-type body frame 10. The body frame 10 has a main tube 12 that extends rearward from an upper portion of a head pipe 11 and then bends downward, and a down tube 13 that extends downward from a lower portion of the head pipe 11 and then bends rearward. The rear end of the down tube 13 is joined to the lower end of the main tube 12, and an installation space for the engine 20 is formed inside the body frame 10. The rear side of the engine 20 is supported by the main tube 12, and the front and lower sides of the engine 20 are supported by the down tube 13.

[0012] The engine 20 is a two-cylinder engine with four valves, and includes a crankcase 21, a cylinder 22 provided on the crankcase 21, a cylinder head 23 provided on the cylinder 22, and a cylinder head cover 24 provided on the cylinder head 23. A clutch cover 25 that covers a clutch (not shown) from the side is attached to the right side of the crankcase 21. A magneto cover (not shown) that covers a magneto (not shown) from the side is attached to the left side of the crankcase 21. An oil pan 26 in which oil is stored is attached to the bottom surface of the crankcase 21.

[0013] As shown in Fig. 2, left and right valve train chambers are formed for each cylinder inside the cylinder head 23 and the cylinder head cover 24. A variable valve train device 30 that can change the valve lift amount of an intake valve 35 and an exhaust valve 37 by hydraulic pressure is mounted in the left and right valve train chambers. The variable valve train device 30 is provided with a camshaft 31 that is common to the intake and exhaust sides. A pair of partitions (not shown) protrude from the bottom surface of the cylinder head 23 for each cylinder, and a pair of cam housings 41 are attached on the pair of partitions. The camshaft 31 is rotatably supported by the mating surfaces of the multiple partitions and the cam housing 41.

[0014] Four intake valves 35 (only one is shown in FIG. 2) are provided on the rear side of the camshaft 31, and four exhaust valves 37 (only one is shown in FIG. 2) are provided on the front side of the camshaft 31. The intake valve 35 is pressed in the valve closing direction by a valve spring 36, and the exhaust valve 37 is pressed in the valve closing direction by a valve spring 38. A low speed cam 32, a high speed cam 33, and an exhaust cam 34 (all see FIG. 3) are formed on the outer circumferential surface of the camshaft 31. Each of the cams 32-34 is a plate with a cam lobe protruding from a part of a base circle, and the cam lobe of the high speed cam 33 is formed higher than that of the low speed cam 32.

[0015] An intake side rocker shaft 45 and an exhaust side rocker shaft 51 are supported on the upper part of the cam housing 41. The intake side rocker shaft 45 and the exhaust side rocker shaft 51 are located higher than the camshaft 31, and the intake side rocker shaft 45 and the exhaust side rocker shaft 51 extend parallel to the camshaft 31. An upper housing 42 is attached to the upper part of the cam housing 41, and a hydraulic piston 61 and a spring pin 63 (see Figure 6) are housed in the upper housing 42. An oil control valve 71 that controls the hydraulic pressure of the variable valve mechanism 30 is provided on the rear side of the upper surface of the cylinder head cover 24.

[0016] As shown in Fig. 3, the intake side rocker shaft 45 is located rearward of the camshaft 31, and the exhaust side rocker shaft 51 is located forward of the camshaft 31. Two types of rocker arms 46a, 46b are supported so as to be able to swing on the intake side rocker shaft 45 (only one of each is shown in Fig. 3), and a rocker arm 52 is supported so as to be able to swing on the exhaust side rocker shaft 51 (only one is shown in Fig. 3). The intake side rocker arm 46a and the exhaust side rocker arm 52 are formed in a seesaw shape having a force point and a point of action, but the intake side rocker arm 46b is formed so as to become the force point of the rocker arm 46a.

[0017] A roller 47a that rolls in contact with the low-speed cam 32 is rotatably supported at one end of the intake side rocker arm 46a, and a pair of intake valves 35 are connected to the other bifurcated end of the rocker arm 46a. A roller 47b that rolls in contact with the high-speed cam 33 is rotatably supported at one end of the intake side rocker arm 46b, and no intake valve 35 is connected to the other end of the rocker arm 46b. A roller 53 that rolls in contact with the exhaust cam 34 is rotatably supported at one end of the exhaust side rocker arm 52, and a pair of exhaust valves 37 are connected to the other bifurcated end of the rocker arm 52. The rocker arms 46a, 46b are formed to be connectable.

[0018] When the engine is in low or medium speed, the rocker arms 46a, 46b are not connected. Therefore, the rocker arm 46a is swung by the low-speed cam 32, and the rocker arm 46b is swung by the high-speed cam 33. Since the pair of intake valves 35 are connected to the rocker arm 46a, the pair of intake valves 35 are moved in response to the rotation of the low-speed cam 32. Since the cam lobe of the low-speed cam 32 is low, the valve lift amount of the pair of intake valves 35 is low. Note that since the intake valve 35 is not connected to the rocker arm 46b, the rocker arm 46b swings idly in response to the rotation of the high-speed cam 33.

[0019] When the engine is rotating at high speed, the rocker arms 46a, 46b are connected. Therefore, the rocker arms 46a, 46b are swung together by the high-speed cam 33. The pair of intake valves 35 are connected to the rocker arm 46b via the rocker arm 46a, so the pair of intake valves 35 are moved in accordance with the rotation of the high-speed cam 33. Since the cam lobes of the high-speed cam 33 are high, the valve lift amount of the pair of intake valves 35 is high. In this way, the connection state of the rocker arms 46a, 46b is switched to switch between the low-speed cam 32 and the high-speed cam 33 that move the intake valve 35.

[0020] Each variable valve device 30 is provided with a switching mechanism 55 that switches between a connected state and a separated state of the rocker arms 46a, 46b by hydraulic pressure. The switching mechanism 55 is provided with a connecting pin 56 installed in a receiving hole of the rocker arm 46b, and a return pin 58 installed in a receiving hole of the rocker arm 46a. The switching mechanism 55 is also provided with a hydraulic piston 61 that contacts the connecting pin 56 from one side in the left-right direction, and a spring pin 63 that contacts the return pin 58 from the other side in the left-right direction. The hydraulic piston 61 is formed so as to be able to advance and retreat by hydraulic pressure, and the spring pin 63 is formed so as to be able to advance and retreat by expansion and contraction of a spring.

[0021] When oil is supplied to the hydraulic piston 61, the hydraulic piston 61 moves forward against the spring force of the spring pin 63. The forward movement of the hydraulic piston 61 pushes the return pin 58 into the connecting pin 56, and a part of the connecting pin 56 moves from the housing hole of the rocker arm 46b into the housing hole of the rocker arm 46a, connecting the rocker arms 46a, 46b. When oil is discharged from the hydraulic piston 61, the hydraulic piston 61 moves backward by the spring force of the spring pin 63. The rearward movement of the hydraulic piston 61 pushes the connecting pin 56 back against the return pin 58, and a part of the connecting pin 56 comes out of the housing hole of the rocker arm 46a, separating the rocker arms 46a, 46b.

[0022] Incidentally, as shown in FIG. 4(A), in the variable valve train 110 of the comparative example 1, the connecting pin 116 is moved by the hydraulic piston 117 regardless of the valve lift. When switching from the low-speed cam 113 to the high-speed cam 114, if the connecting pin 116 protrudes from the accommodation hole of the rocker arm 115b immediately before the valve lift of the intake valve 111, the penetration of the connecting pin 116 into the accommodation hole of the rocker arm 115a becomes shallow. As shown in FIG. 4(B), if the connecting pin 116 comes out of the accommodation hole of the rocker arm 115a during the valve lift by the high-speed cam 114, the rocker arm 115a collides with the low-speed cam 113, generating an abnormal noise and causing a problem that the durability of the variable valve train 110 is reduced. In addition, there are cases where the mouth of the accommodation hole of the rocker arm 115a is worn out when the connecting pin 116 comes out of the accommodation hole of the rocker arm 115a.

[0023] In this case, as shown in Fig. 5(A), when switching from the low-speed cam 123 to the high-speed cam 124, oil may be supplied from the operating passage 128 to the hydraulic piston 127 for a predetermined period of time after the valve lift ends. This prevents the valve lift from impeding the connecting operation of the pair of rocker arms 125a, 125b. However, the operating passage 128 alone results in intermittent oil supply, making the connected state of the pair of rocker arms 125a, 125b unstable. For this reason, a direct passage 129 is provided that is opened after oil is supplied from the operating passage 128, and oil is supplied from the direct passage 129 to the hydraulic piston 127 to stabilize the connected state.

[0024] As shown in Fig. 5(B), when switching from the high speed cam 124 to the low speed cam 123, oil is discharged from the operating passage 128 and the direct passage 129 and the hydraulic piston 127 retreats, but the direct passage 129 is blocked during the retreat of the hydraulic piston 127. As shown in Fig. 5(C), oil is discharged from the operating passage 128 only for a predetermined period after the end of the valve lift, so the valve lift starts before the movement of the hydraulic piston 127 stagnates and the connecting pin 126 comes off the rocker arm 125a. If the connecting pin 126 comes off the accommodation hole of the rocker arm 125a during the valve lift, various problems such as the generation of abnormal noise as described above will occur.

[0025] Therefore, in the variable valve train 30 of this embodiment, the working passage 81 and the direct passage 85 are connected by a bypass passage 86, so that oil is discharged from the hydraulic piston 61 even outside the specified period after the end of the valve lift when switching from the high speed cam 33 to the low speed cam 32 (see FIG. 6). Even if the direct passage 85 is blocked by the hydraulic piston 61 and only the working passage 81 is connected to the hydraulic piston 61, oil continues to be discharged from the hydraulic piston 61 through the bypass passage 86 regardless of the timing of the end of the valve lift. The pair of rocker arms 46a, 46b are smoothly separated, suppressing the generation of abnormal noise and improving the durability of the variable valve train 30.

[0026] The variable valve gear of this embodiment will be described below with reference to Fig. 6 to Fig. 8. Fig. 6 is a schematic diagram of the variable valve gear of this embodiment. Fig. 7 is a schematic diagram of the operating passage and direct passage of this embodiment. Fig. 8 is a perspective view of the hydraulic piston of this embodiment.

[0027] As shown in Fig. 6, in the variable valve gear 30, an oil supply passage 64 extends from the oil pan 26 to an oil control valve 71. Oil is pumped up from the oil pan 26 by an oil pump 91 located midway along the oil supply passage 64, and the oil is supplied to the oil control valve 71 through an oil filter 92. The oil control valve 71 is formed by a valve housing 72 that accommodates a valve spool (not shown), and a solenoid 73 that moves the valve spool forward and backward. The solenoid 73 moves the valve spool forward and backward, thereby switching the oil passage within the oil control valve 71.

[0028] The valve housing 72 is formed with an input port 74, a low speed port 75, a high speed port 76, and a drain port 77. The input port 74 is connected to the oil supply passage 64, the low speed port 75 is connected to a dead end passage 65, the high speed port 76 is connected to a switching passage 66, and the drain port 77 is connected to a drain passage 67. The output destination of the dead end passage 65 is blocked, and the switching passage 66 extends from the oil control valve 71 toward the switching mechanism 55. The drain passage 67 extends from the oil control valve 71 to above the oil pan 26, and oil drops from the outlet of the drain passage 67 into the oil pan 26.

[0029] By moving the valve spool of the oil control valve 71, the input port 74 is connected to either the low speed port 75 or the high speed port 76, and the drain port 77 is connected to the other of the low speed port 75 or the high speed port 76. Oil is output from the oil control valve 71 to either the dead end passage 65 or the switching passage 66, and excess oil is discharged from the other of the dead end passage 65 or the switching passage 66 to the oil control valve 71 (drain passage 67). In this way, the oil pressure to the switching mechanism 55 is controlled by the oil control valve 71.

[0030] The switching passage 66 is divided into an operating passage (first oil passage) 81 and a direct passage (second oil passage) 85, and both the operating passage 81 and the direct passage 85 extend from the oil control valve 71 to the hydraulic piston 61 of the switching mechanism 55. A part of the operating passage 81 is formed with an oil groove 83 that passes oil at a predetermined rotational phase of the camshaft 31. As described above, the camshaft 31 is formed with the low speed cam 32, the high speed cam 33, and the exhaust cam 34 (not shown in FIG. 6), and the oil groove 83 is partially formed on the outer circumferential surface of the camshaft 31 supported by the cam housing 41 (see FIG. 2).

[0031] The working passage 81 is divided into an upstream passage 82a and a downstream passage 82b by an oil groove 83 in the camshaft 31. As the camshaft 31 rotates, communication and disconnection between the upstream passage 82a and the downstream passage 82b of the working passage 81 are repeated alternately. As a result, oil is intermittently supplied from the oil control valve 71 to the hydraulic piston 61, and oil is intermittently discharged from the hydraulic piston 61 to the oil control valve 71. The specified rotational phase of the camshaft 31 is set between the end of the valve lift and the start of the next valve lift.

[0032] In addition, the direct passage 85 extends directly from the oil control valve 71 to the hydraulic piston 61 without passing through the oil groove 83 of the camshaft 31. For this reason, oil is continuously supplied from the oil control valve 71 to the hydraulic piston 61 through the direct passage 85, and oil is continuously discharged from the hydraulic piston 61 to the oil control valve 71 through the direct passage 85. The direct passage 85 is opened and closed by the hydraulic piston 61. The direct passage 85 is opened when the hydraulic piston 61 is moving forward, and the direct passage 85 is closed when the hydraulic piston 61 is moving backward.

[0033] Also, a bypass passage 86 is formed to bypass the oil groove 83 in the middle of the working passage 81 when the direct passage 85 is blocked. The working passage 81 and the direct passage 85 are connected via the bypass passage 86, so that even if the direct passage 85 is blocked by the hydraulic piston 61, oil is continuously discharged from the hydraulic piston 61 to the oil control valve 71, bypassing the oil groove 83. Note that, although details will be described later, the hydraulic piston 61 is moved as a trigger by the oil supply through the working passage 81, and the hydraulic piston 61 is held in a pushed-out state by the oil supply through the direct passage 85.

[0034] As described above, the rocker arms 46a, 46b are adjacent to each other, but the upper parts of the rocker arms 46a, 46b are adjacent to each other with a small gap C therebetween. The upper parts of the rocker arms 46a, 46b are formed with accommodation holes 48a, 48b parallel to the camshaft 31. The diameters of the accommodation hole 48a of the rocker arm 46a and the accommodation hole 48b of the rocker arm 46b are the same, and the accommodation holes 48a, 48b are formed coaxially so as to communicate with each other when not lifted up. A connecting pin 56 is installed in the accommodation hole 48b of the rocker arm 46b, and a return pin 58 is installed in the accommodation hole 48a of the rocker arm 46a. The tip of the return pin 58 is in contact with the tip of the connecting pin 56.

[0035] A sliding chamber 43 is formed in the upper housing 42 on one side of the rocker arm 46b. A hydraulic piston 61 is installed in the sliding chamber 43. The pressing surface of the hydraulic piston 61 contacts the connecting pin 56, and the connecting pin 56 is moved to the other side by the hydraulic piston 61. Furthermore, a sliding chamber 44 is formed in the upper housing 42 on the other side of the rocker arm 46a. A spring pin 63 is installed in the sliding chamber 44. The pressing surface of the spring pin 63 contacts the return pin 58, and the return pin 58 is returned to one side by the spring pin 63. A sensing arm 69 extends from the spring pin 63 to the other side.

[0036] In the switching mechanism 55, the connected state of the rocker arms 46a, 46b is switched by hydraulically moving the connecting pin 56. As described above, when the rocker arms 46a, 46b are in the separated state, the pair of intake valves 35 is operated via the rocker arm 46a by the low-speed cam 32. When the rocker arms 46a, 46b are in the connected state, the pair of intake valves 35 is operated via the rocker arms 46a, 46b by the high-speed cam 33. In this way, in the switching mechanism 55, the connected state of the rocker arms 46a, 46b is switched by the connecting pin 56, thereby switching the cam that operates the pair of intake valves 35.

[0037] The variable valve train 30 is also provided with an ECM (Engine Control Module) 93, an engine angle sensor 94, and a switching sensor 95. The engine speed is detected by the engine angle sensor 94, and when the engine speed exceeds a predetermined speed, the ECM 93 outputs a connection command signal to the solenoid 73, and when the engine speed falls below the predetermined speed, the ECM 93 outputs a release command signal to the solenoid 73. The switching sensor 95 detects switching between the connected and disconnected states of the rocker arms 46a, 46b from the movement of the tip of the sensing arm 69. The command signal of the ECM 93 and the detection signal of the switching sensor 95 are compared to determine a failure of the variable valve train 30, such as a switching malfunction.

[0038] As shown in Fig. 7, an upstream passage 82a of the working passage 81 extends from the oil control valve 71 to the camshaft 31, and a downstream passage 82b of the working passage 81 extends from the camshaft 31 to the hydraulic piston 61. The downstream end of the upstream passage 82a and the upstream end of the downstream passage 82b are positioned on the same circumference on the outer circumferential surface of the camshaft 31. An oil groove 83 is formed in the circumferential direction on the circumference of the outer circumferential surface of the camshaft 31. A direct passage 85 extends from the oil control valve 71 to the hydraulic piston 61, and is formed to be shorter than the working passage 81.

[0039] When oil is supplied to the hydraulic piston 61, the oil passes only while the upstream passage 82a and the downstream passage 82b are in communication with each other via the oil groove 83. The oil groove 83 is formed so that the upstream passage 82a and the downstream passage 82b are in communication with each other at the end of the valve lift, and the upstream passage 82a and the downstream passage 82b are separated from each other before the start of the valve lift. In other words, the oil groove 83 is formed so that the supply of oil from the oil control valve 71 to the hydraulic piston 61 starts at the end of the valve lift, and the supply of oil to the hydraulic piston 61 ends before the start of the valve lift.

[0040] Since oil begins to be supplied to the hydraulic piston 61 at the end of the valve lift, the connecting operation of the rocker arms 46a, 46b is not hindered by the valve lift. The connecting operation of the rocker arms 46a, 46b is completed before the valve lift starts, so the rocker arms 46a, 46b are not connected in the middle of the valve lift. After oil is supplied to the hydraulic piston 61 from the operating passage 81, oil is supplied to the hydraulic piston 61 from the direct passage 85. There is a risk that the hydraulic piston 61 will move if only the operating passage 81 is supplied with oil intermittently, but the supply of oil from the direct passage 85 holds the hydraulic piston 61 stably.

[0041] When oil is discharged from the hydraulic piston 61, the oil is discharged through the working passage 81 and the direct passage 85. The direct passage 85 is blocked by the hydraulic piston 61 halfway through the discharge of the oil, and the oil is only discharged intermittently from the working passage 81. In this embodiment, the working passage 81 and the direct passage 85 are connected via a bypass passage 86, and the oil is continuously discharged from the hydraulic piston 61 through the working passage 81, the bypass passage 86, and the direct passage 85. Therefore, the hydraulic piston 61 is quickly returned to the initial position, and the valve lift of the high speed cam 33 does not start in a state in which the rocker arms 46a, 46b are not completely separated.

[0042] The downstream end of the working passage 81 and the downstream end of the direct passage 85 are adjacent to each other, and the downstream end of the working passage 81 and the downstream end of the direct passage 85 are communicated with each other via a bypass passage 86. The bypass passage 86 is shortened, and oil flows from the working passage 81 to the direct passage 85 through the bypass passage 86, so that the oil is quickly discharged from the hydraulic piston 61. Note that oil passes through the bypass passage 86 not only when oil is discharged from the hydraulic piston 61 but also when oil is supplied to the hydraulic piston 61, but the cross-sectional area of ​​the bypass passage 86 is formed smaller than the cross-sectional areas of the working passage 81 and the direct passage 85, so that the effect of the bypass passage 86 is suppressed.

[0043] 7 and 8, the bypass passage 86 in this embodiment is formed by a communication groove 62 provided on the outer peripheral surface of the hydraulic piston 61. The rear end of the outer peripheral surface of the hydraulic piston 61 bulges out in an annular shape so as to separate the downstream end of the working passage 81 from the downstream end of the direct passage 85, and the downstream end of the working passage 81 and the downstream end of the direct passage 85 are connected via the communication groove 62 which is a partially recessed portion of the annular bulge. In this case, by preparing hydraulic pistons 61 with different numbers and widths of communication grooves 62, the cross-sectional area of ​​the bypass passage 86 can be changed by replacing the hydraulic piston 61, thereby adjusting the amount of oil passing through.

[0044] The connecting operation and the separating operation of the variable valve gear will be explained with reference to Figures 9 and 10. Figure 9 is an explanatory diagram of the connecting operation of the variable valve gear of this embodiment. Figure 10 is an explanatory diagram of the separating operation of the variable valve gear of this embodiment. For convenience of explanation, the symbols in Figure 6 will be used as appropriate in Figures 9 and 10.

[0045] As shown in Fig. 9(A), a hydraulic piston 61 is installed in a cylindrical sliding chamber 43 of an upper housing 42. The downstream end of an operating passage 81 (downstream passage 82b) opens at the back surface of the sliding chamber 43, and the downstream end of a direct passage 85 opens at the inner peripheral surface of the sliding chamber 43. The direction in which oil is supplied from the operating passage 81 to the hydraulic piston 61 is the forward / backward direction of the hydraulic piston 61, and the direction in which oil is supplied from the direct passage 85 to the hydraulic piston 61 is the radial direction of the hydraulic piston 61. During low-speed operation, the hydraulic piston 61 retracts, and the downstream end of the direct passage 85 is blocked by the outer peripheral surface of the hydraulic piston 61.

[0046] During low-speed operation, oil is not supplied from the oil control valve 71 to the hydraulic piston 61. No pressing force is applied from the hydraulic piston 61 to the connecting pin 56, and the spring force of the spring pin 63 is applied to the return pin 58. The flange of the return pin 58 abuts against the rocker arm 46a, and the return pin 58 is positioned in the initial position. At this time, the tip 57 of the connecting pin 56 contacts the tip 59 of the return pin 58 at separation position P1 in the gap C between the rocker arms 46a, 46b. The tip 57 of the connecting pin 56 is positioned in the gap C between the rocker arms 46a, 46b, and the rocker arms 46a, 46b are separated.

[0047] When switching from low-speed operation to high-speed operation begins, oil begins to be supplied from the oil control valve 71 to the hydraulic piston 61. At this time, while the upstream passage 82a and downstream passage 82b of the working passage 81 are in communication with each other via the oil groove 83 of the camshaft 31, that is, while the oil is supplied to the hydraulic piston 61 at a predetermined rotation phase of the camshaft 31 that avoids valve lift. As hydraulic pressure acts on the hydraulic piston 61, the hydraulic piston 61 moves forward against the repulsive force of the spring pin 63, and the hydraulic piston 61 pushes in the connecting pin 56.

[0048] 9(B), in the initial stage of switching from low-speed operation to high-speed operation, the forward movement of hydraulic piston 61 pushes return pin 58 out of connecting pin 56, and part of connecting pin 56 begins to enter accommodation hole 48a of rocker arm 46a. At this point, connecting pin 56 is not deeply inserted into accommodation hole 48a of rocker arm 46a, and connection between rocker arms 46a, 46b is incomplete. Since no valve lift occurs in intake valve 35, connecting pin 56 does not come out of rocker arm 46a due to valve lift while rocker arms 46a, 46b are being connected.

[0049] As shown in Fig. 9(C), after switching to high-speed operation, the hydraulic piston 61 is pushed by hydraulic pressure to a position where the hydraulic stroke is maximum. The tip 57 of the connecting pin 56 is positioned at the connecting position P2 of the rocker arm 46a. A part of the connecting pin 56 is deeply inserted into the accommodation hole 48a of the rocker arm 46a, and the rocker arms 46a, 46b are connected via the connecting pin 56. In addition, the forward movement of the hydraulic piston 61 opens the downstream end of the direct passage 85, and the supply of oil from the direct passage 85 holds the hydraulic piston 61 at the maximum stroke position.

[0050] 10(A), when switching from high-speed operation to low-speed operation starts, oil starts to be discharged from the hydraulic piston 61 to the oil control valve 71 (drain passage 67). As the camshaft 31 rotates, the oil in the hydraulic piston 61 is discharged through the operating passage 81, and the oil in the hydraulic piston 61 is discharged through the direct passage 85. When the hydraulic pressure in the hydraulic piston 61 is released, the hydraulic piston 61 is pushed back from the maximum stroke position in the backward direction by the repulsive force of the spring pin 63 via the return pin 58 and the connecting pin 56.

[0051] As shown in Fig. 10(B), at the beginning of switching from high-speed operation to low-speed operation, the downstream end of the direct passage 85 is blocked by the hydraulic piston 61 while the hydraulic piston 61 is moving backward. At this time, the working passage 81 does not allow oil to pass through it except at a predetermined rotation phase of the camshaft 31, but oil is passed from the working passage 81 to the direct passage 85 via the bypass passage 86. Oil continues to be discharged from the hydraulic piston 61 to the oil control valve 71 through the bypass passage 86, bypassing the oil groove 83 (see Fig. 6) of the camshaft 31. For this reason, the hydraulic piston 61 does not stop midway through the backward movement, and the connecting pin 56 does not stay in the accommodation hole 48a of the rocker arm 46a.

[0052] As shown in Fig. 10(C), after switching to low-speed operation, the hydraulic piston 61 is pushed back to the position where the stroke is minimum by the repulsive force of the spring pin 63. As the hydraulic piston 61 retreats, the tip 57 of the connecting pin 56 is positioned at the separation position P1 of the rocker arm 46a. The connecting pin 56 comes completely out of the accommodation hole 48a of the rocker arm 46a, and the rocker arms 46a, 46b are separated. No hydraulic pressure is applied to the hydraulic piston 61, and the spring force of the spring pin 63 holds the hydraulic piston 61 at the position where the stroke is minimum.

[0053] As described above, according to the variable valve gear 30 of this embodiment, when oil is supplied from the oil control valve 71 to the hydraulic piston 61, the hydraulic piston 61 advances due to the hydraulic pressure in the working passage 81 at a predetermined rotation phase of the camshaft 31. When the direct passage 85 is opened during the forward movement of the hydraulic piston 61 and the rocker arms 46a, 46b are connected, the connected state is maintained by the hydraulic pressure in the direct passage 85. On the other hand, when oil is discharged from the hydraulic piston 61 to the oil control valve 71, the hydraulic pressure in the working passage 81 and the direct passage 85 is released and the hydraulic piston 61 retreats. When the hydraulic piston 61 retreats, the direct passage 85 is closed and the oil groove 83 of the working passage 81 does not pass oil except at a predetermined rotation phase of the camshaft 31. At this time, oil continues to be discharged from the hydraulic piston 61 through the bypass passage 86 that bypasses the oil groove 83, so that the rocker arms 46a, 46b are smoothly separated.

[0054] In this embodiment, the bypass passage is formed by the communication groove on the outer peripheral surface of the hydraulic piston, but the bypass passage may be formed so as to bypass the oil groove of the working passage when the direct passage is blocked. For example, as shown in Modification 1 of FIG. 11, the bypass passage may be formed by a through hole 98 provided on the outer peripheral surface of a hydraulic piston 97. The hydraulic piston 97 is formed in a cylindrical shape, and the working passage and the direct passage are communicated through the through hole 98. By preparing hydraulic pistons 97 with different numbers of through holes 98 or different hole diameters, the cross-sectional area of ​​the bypass passage can be changed by replacing the hydraulic piston 97, thereby adjusting the amount of oil passing through.

[0055] 12 and 13, an oil hole 101 communicating with an oil control valve (not shown) is formed in the lower surface of the upper housing 100. An oil groove 102a extends from the oil hole 101 to directly below the camshaft (not shown), and an oil groove 102b extends from a location adjacent to the downstream end of the oil groove 102a to near the sliding chamber of the hydraulic piston (not shown). The downstream end of the oil groove 102a communicates with an oil hole 106a in the cam housing 105, and the upstream end of the oil groove 102b communicates with an oil hole 106b in the cam housing 105. The oil holes 106a and 106b penetrate from the upper surface of the cam housing 105 to the support surface 107 on the lower surface.

[0056] Additionally, on the underside of the upper housing 100, an oil groove 102c extends from the oil hole 101 to the vicinity of the sliding chamber of the hydraulic piston. By fixing the upper housing 100 to the cam housing 105, the oil groove 102a and the oil hole 106a form an upstream passage of the operating passage, and the oil groove 102b and the oil hole 106b form a downstream passage of the operating passage. Additionally, the oil groove 102c forms a direct passage. The oil holes 106a and 106b open in the support surface 107 of the camshaft, and the oil holes 106a and 106b are repeatedly connected and disconnected by the oil groove (not shown) of the camshaft.

[0057] As a second modification, a bypass passage that connects the working passage and the direct passage may be formed on the lower surface of the upper housing 100. In this case, the downstream end of the oil groove 102b and the downstream end of the oil groove 102c are adjacent to each other, and the downstream ends of the oil grooves 102b and 102c are connected to each other via a narrow groove 103a shown by a broken line. Also, as a third modification, a bypass passage that connects the upstream passage and the downstream passage of the working passage may be formed on the lower surface of the upper housing 100. In this case, the downstream end of the oil groove 102a and the upstream end of the oil groove 102b are adjacent to each other, and the downstream end of the oil groove 102a and the upstream end of the oil groove 102b are connected to each other via a narrow groove 103b shown by a broken line.

[0058] As a fourth modification, a bypass passage that connects the upstream and downstream passages of the working passage may be formed on the upper surface of the cam housing 105. In this case, the oil holes 106a and 106b are adjacent to each other on the upper surface of the cam housing 105, and the oil holes 106a and 106b are connected to each other via a narrow groove 108c shown by a broken line. As a fifth modification, a bypass passage that connects the upstream and downstream passages of the working passage may be formed on the support surface 107 of the cam housing 105. In this case, the oil holes 106a and 106b are adjacent to each other on the support surface 107 of the cam housing 105, and the oil holes 106a and 106b are connected to each other via a narrow groove 108d shown by a broken line.

[0059] In Modification 2-5, by preparing upper housing 100 and cam housing 105 with different groove widths, hole diameters, etc., it is possible to change the cross-sectional areas of the working passage, direct passage, and bypass passage by replacing upper housing 100, thereby adjusting the amount of oil passing through. Note that a bypass passage may be formed in the hydraulic piston by both a communicating groove and a through hole, and a bypass passage may be formed in the upper housing and cam housing by two or more of the narrow grooves listed above. Also, bypass passages may be formed in the hydraulic piston, upper housing, and cam housing.

[0060] Furthermore, in this embodiment, the timing at which the valve lift ends is not limited to the timing at which the valve lift has completely ended, but includes the timing immediately before the end at which the valve lift can be regarded as having ended.

[0061] In this embodiment, the oil control valve starts to supply oil to the switching mechanism when the valve lift ends, but the timing of the oil supply is not limited to the timing of the valve lift end. The oil control valve may start to supply oil to the switching mechanism in a zero section where no valve lift occurs. Even with this configuration, it is possible to prevent the valve lift from interfering with the switching operation of the cam.

[0062] In addition, in this embodiment, a pair of rocker arms are provided on the intake side of the variable valve device, but it is sufficient if multiple rocker arms are provided on the intake side of the variable valve device. For example, three or more rocker arms may be provided on the intake side of the variable valve device.

[0063] Further, in this embodiment, a seesaw type rocker arm is exemplified, but the type of rocker arm is not particularly limited, and a finger follower type rocker arm may also be used.

[0064] Further, in this embodiment, the rocker arms are adjacent to each other, but the rocker arms may be spaced apart.

[0065] The variable valve mechanism of the present embodiment may be used not only in the engine of the saddle-ride vehicle but also in the engine of other vehicles. The saddle-ride vehicle is not limited to a motorcycle but may be any vehicle equipped with an engine. The saddle-ride vehicle is not limited to all vehicles on which the rider sits astride the seat, but also includes scooter-type vehicles on which the rider does not sit astride the seat.

[0066] As described above, the first aspect is a variable valve gear (30) capable of changing a valve lift amount in a cylinder head (23), and includes a camshaft (31) on which a plurality of cams (low speed cam 32, high speed cam 33) having different valve lift amounts are formed, a plurality of rocker arms (46a, 46b) that move a valve (intake valve 35) by contacting the plurality of cams, a switching mechanism (55) that hydraulically connects and disconnects the plurality of rocker arms, and an oil control valve (71) that controls hydraulic pressure for the switching mechanism, wherein the switching mechanism has a hydraulic piston (61) that moves forward and backward by hydraulic pressure, The multiple rocker arms are connected by the forward movement of the piston, and the multiple rocker arms are separated by the retraction of the hydraulic piston. A first oil passage (operating passage 81) and a second oil passage (direct passage 85) extend from the oil control valve to the hydraulic piston. A part of the first oil passage is formed as an oil groove (83) through which oil passes at a predetermined rotation phase of the camshaft. The second oil passage is opened during the forward movement of the hydraulic piston and closed during the retraction of the hydraulic piston. A bypass passage (86) is formed for bypassing the oil groove when the second oil passage is closed. According to this configuration, when oil is supplied from the oil control valve to the hydraulic piston, the hydraulic piston advances due to the hydraulic pressure of the first oil passage at a predetermined rotation phase of the camshaft. When the second oil passage is opened during the forward movement of the hydraulic piston, and the multiple rocker arms are connected, the connected state is maintained by the hydraulic pressure of the second oil passage. On the other hand, when oil is discharged from the hydraulic piston to the oil control valve, the hydraulic pressure of the first and second oil passages is released and the hydraulic piston retracts. The second oil passage is blocked when the hydraulic piston is retracting, and the oil groove of the first oil passage does not allow oil to pass through it except at the specified rotation phase of the camshaft. At this time, oil continues to be discharged from the hydraulic piston through a bypass passage that bypasses the oil groove, allowing the multiple rocker arms to be smoothly separated.

[0067] In the second aspect, in the first aspect, the cross-sectional area of ​​the bypass passage is smaller than the cross-sectional areas of the first oil passage and the second oil passage. With this configuration, the effect of the bypass passage on the supply of oil to the hydraulic piston can be suppressed.

[0068] In the third aspect, in the first or second aspect, the downstream end of the first oil passage and the downstream end of the second oil passage are adjacent to each other, and the downstream end of the first oil passage and the downstream end of the second oil passage are connected via a bypass passage. With this configuration, the bypass passage can be shortened. Oil flows from the first oil passage to the second oil passage through the bypass passage, and the oil can be quickly discharged from the hydraulic piston.

[0069] In the fourth aspect, in the third aspect, the bypass passage is formed by a communication groove (62) provided on the outer circumferential surface of the hydraulic piston. According to this configuration, by preparing hydraulic pistons with different numbers of communication grooves or different groove widths, the cross-sectional area of ​​the bypass passage can be changed by replacing the hydraulic piston, thereby adjusting the amount of oil passing through.

[0070] In the fifth aspect, in the third or fourth aspect, the bypass passage is formed by a through hole (98) provided in the outer peripheral surface of the hydraulic piston (97). According to this configuration, by preparing hydraulic pistons with different numbers or diameters of through holes, the cross-sectional area of ​​the bypass passage can be changed by replacing the hydraulic piston, thereby adjusting the amount of oil passing through.

[0071] A sixth aspect is any one of the first to fifth aspects, and includes a cam housing (105) that rotatably supports a camshaft, and an upper housing (100) attached to an upper surface of the cam housing, and a first oil passage, a second oil passage, and a bypass passage connecting the first oil passage and the second oil passage are formed in the upper housing. According to this configuration, by preparing upper housings with different passage widths, the cross-sectional areas of the first and second oil passages and the bypass passage can be changed by replacing the upper housing, thereby adjusting the amount of oil passing through.

[0072] A seventh aspect is any one of the first to fifth aspects, and includes a cam housing that rotatably supports the camshaft, and an upper housing attached to an upper surface of the cam housing, the cam housing and / or the upper housing are formed with a first oil passage, a second oil passage, and a bypass passage, and the upstream side and downstream side of the first oil passage are connected via the bypass passage across an oil groove in the camshaft. With this configuration, oil flows from the downstream side to the upstream side of the first oil passage through the bypass passage, and the oil can be quickly discharged from the hydraulic piston.

[0073] An eighth aspect is any one of the first to seventh aspects, in which an oil groove is formed so that oil starts to be supplied from the oil control valve to the switching mechanism at the end timing of the valve lift or in the zero section where no valve lift occurs. With this configuration, oil starts to be supplied from the oil control valve to the switching mechanism at the end timing of the valve lift or in the zero section, so that the connecting operation of the multiple rocker arms is not hindered by the valve lift.

[0074] Although the present embodiment has been described, other embodiments may be made by combining the above-described embodiments and modifications in whole or in part.

[0075] In addition, the technology of the present invention is not limited to the above examples, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to the progress of technology or a different technology derived therefrom, the invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea. [Explanation of symbols]

[0076] 23: Cylinder head 30: Variable valve gear 31: Camshaft 32: Low speed cam (multiple cams) 33: High speed cam (multiple cams) 35: Intake valve (valve) 46a, 46b: Rocker arm 55: Switching mechanism 61: Hydraulic piston 62: Hydraulic piston communication groove 71: Oil control valve 81: Working passage (first oil passage) 83: Camshaft oil groove 85: Direct passage (second oil passage) 86: Bypass passage 97: Hydraulic piston 98: Hydraulic piston through hole 100: Upper housing 105: Cam housing

Claims

1. A variable valve mechanism capable of changing a valve lift amount in a cylinder head, A camshaft on which a plurality of cams with different valve lift amounts are formed; A plurality of rocker arms that move the valves by contacting the plurality of cams; A switching mechanism that hydraulically connects and disconnects the plurality of rocker arms; an oil control valve for controlling hydraulic pressure for the switching mechanism, The switching mechanism has a hydraulic piston that moves forward and backward by hydraulic pressure, and the plurality of rocker arms are connected by the forward movement of the hydraulic piston, and the plurality of rocker arms are separated by the backward movement of the hydraulic piston, a first oil passage and a second oil passage extend from the oil control valve to the hydraulic piston; a portion of the first oil passage is formed by an oil groove through which oil passes at a predetermined rotation phase of the camshaft, the second oil passage is opened during the forward movement of the hydraulic piston and closed during the backward movement of the hydraulic piston, a bypass passage for bypassing the oil groove when the second oil passage is blocked;

2. 2. The variable valve mechanism according to claim 1, wherein a cross-sectional area of ​​the bypass passage is smaller than a cross-sectional area of ​​the first oil passage and a cross-sectional area of ​​the second oil passage.

3. a downstream end of the first oil passage and a downstream end of the second oil passage are adjacent to each other, 3. The variable valve mechanism according to claim 1, wherein a downstream end of the first oil passage and a downstream end of the second oil passage are connected to each other via the bypass passage.

4. 4. The variable valve mechanism according to claim 3, wherein the bypass passage is formed by a communication groove provided on an outer circumferential surface of the hydraulic piston.

5. 4. The variable valve mechanism according to claim 3, wherein the bypass passage is formed by a through hole provided in an outer peripheral surface of the hydraulic piston.

6. a cam housing that rotatably supports the camshaft; an upper housing attached to an upper surface of the cam housing; 3. The variable valve mechanism according to claim 1, wherein the upper housing is formed with the first oil passage, the second oil passage, and the bypass passage connecting the first oil passage and the second oil passage.

7. a cam housing that rotatably supports the camshaft; an upper housing attached to an upper surface of the cam housing; the first oil passage, the second oil passage, and the bypass passage are formed in the cam housing and / or the upper housing, 3. The variable valve mechanism according to claim 1, wherein the upstream side and downstream side of the first oil passage are connected to each other via the bypass passage, with the oil groove of the camshaft in between.

8. 3. The variable valve device according to claim 1, wherein the oil groove is formed so that oil starts to be supplied from the oil control valve to the switching mechanism at the end timing of a valve lift or at a zero section in which no valve lift occurs.

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