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 camshaft (31) formed with a plurality of cams (32, 33) different in valve lift amount, a plurality of rocker arms (46a, 46b) for abutting on the plurality of cams for moving valves, 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 switching mechanism has a connecting piston (61) and a disconnecting piston (63) which are moved forward and backward with hydraulic pressure, respectively. The plurality of rocker arms are connected to one another with the forward movement of the connecting piston and the plurality of rocker arms are disconnected from one another with the forward movement of the disconnecting piston. An oil control valve moves the connecting piston forward in the predetermined rotational phase of the camshaft and moves the disconnecting piston forward in the predetermined rotational phase of the camshaft.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] One aspect of the variable valve gear of the present invention is a variable valve gear capable of changing a valve lift amount in a cylinder head, and comprises a camshaft on which a plurality of cams with different valve lift amounts are formed, a plurality of rocker arms that abut against the plurality of cams to move the valves, 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, wherein the switching mechanism has a connecting piston and a separation piston that move forward and backward by hydraulic pressure, the plurality of rocker arms are connected by the advancement of the connecting piston, and the plurality of rocker arms are separated by the advancement of the separation piston, and the oil control valve advances the connecting piston at a predetermined rotational phase of the camshaft and advances the separation piston at a predetermined rotational phase of the camshaft, thereby solving the above-mentioned problems. Effect of the Invention

[0007] According to a variable valve gear of one aspect of the present invention, when oil is supplied from the oil control valve to the connecting piston, the connecting piston advances at a predetermined rotational phase of the camshaft that avoids valve lift, so that the connection of the multiple rocker arms is not hindered by the valve lift. Also, when oil is supplied from the oil control valve to the separating piston, the separating piston advances at a predetermined rotational phase of the camshaft that avoids valve lift, so that the separation of the multiple rocker arms is not hindered by the valve lift. [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] 5A to 5C are explanatory diagrams of a coupling operation of the variable valve operating device of the present embodiment. [Figure 9] 5A to 5C are explanatory diagrams of a separation operation of the variable valve operating device of the present embodiment. 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. The switching mechanism is provided with a connecting piston and a separating piston that move forward and backward by hydraulic pressure, and the plurality of rocker arms are connected by the forward movement of the connecting piston, and the plurality of rocker arms are separated by the forward movement of the separating piston. When oil is supplied to the connecting piston from the oil control valve, the connecting piston advances at a predetermined rotation phase of the camshaft that avoids valve lift, so that the connection of the plurality of rocker arms is not hindered by the valve lift. In addition, when oil is supplied to the separating piston from the oil control valve, the separating piston advances at a predetermined rotation phase of the camshaft that avoids valve lift, so that the separation of the plurality of rocker arms is not hindered by the valve lift. 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 connecting piston 61 and a separation piston 63 (see Figure 6) are housed in the upper housing 42. An oil control valve 71 that controls the oil 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 connecting piston 61 that contacts the connecting pin 56 from one side in the left-right direction, and a separation piston 63 that contacts the return pin 58 from the other side in the left-right direction. The connecting piston 61 and the separation piston 63 are formed to be able to advance and retreat by hydraulic pressure.

[0021] In the variable valve gear 30, when oil is supplied from the oil control valve 71 to the connecting piston 61, the oil is discharged from the separation piston 63 to the oil control valve 71. The connecting piston 61 moves forward to approach the rocker arm 46b, and the separation piston 63 moves backward to move away from the rocker arm 46a. The forward movement of the connecting piston 61 and the backward movement of the separation piston 63 push the return pin 58 into the connecting pin 56, and a part of the connecting pin 56 enters from the accommodation hole of the rocker arm 46b into the accommodation hole of the rocker arm 46a, connecting the rocker arms 46a, 46b.

[0022] Furthermore, in the variable valve mechanism 30, when oil is supplied from the oil control valve 71 to the separation piston 63, the oil is discharged from the connecting piston 61 to the oil control valve 71. The separation piston 63 advances toward the rocker arm 46a, and the connecting piston 61 retreats away from the rocker arm 46b. The advancement of the separation piston 63 and the retreat of the connecting piston 61 pushes the connecting pin 56 back against the return pin 58, and part of the connecting pin 56 comes out of the accommodation hole of the rocker arm 46a, separating the rocker arms 46a, 46b.

[0023] 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.

[0024] 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.

[0025] However, as shown in Fig. 5(B), switching from the high speed cam 124 to the low speed cam 123 can be performed at any time. For this reason, the valve lift may be resumed before the connecting pin 126 is disengaged from the accommodation hole of the rocker arm 125a. As shown in Fig. 5(C), if the connecting pin 126 is disengaged from the accommodation hole of the rocker arm 125a during the valve lift, various problems such as the generation of abnormal noise as described above may occur. Therefore, the variable valve gear 30 of this embodiment is configured to perform not only switching from the low speed cam 32 to the high speed cam 33, but also switching from the high speed cam 33 to the low speed cam 32 after the valve lift ends and before the next valve lift starts.

[0026] The variable valve system of this embodiment will be described below with reference to Figures 6 and 7. Figure 6 is a schematic diagram of the variable valve system of this embodiment. Figure 7 is a schematic diagram of the operating passage and direct passage 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] An input port 74, a separation port 75, a connecting port 76, and a drain port 77 are formed in the valve housing 72. The input port 74 is connected to the oil supply passage 64, the separation port 75 is connected to the separation passage 65, the connecting port 76 is connected to the connecting passage 66, and the drain port 77 is connected to the drain passage 67. The separation passage 65 extends toward the separation piston 63 to control the separation piston 63, and the connecting passage 66 extends toward the connecting piston 61 to control the connecting piston 61. 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 separation port 75 or the connecting port 76, and the drain port 77 is connected to the other of the separation port 75 or the connecting port 76. Oil is output from the oil control valve 71 to either the separation passage 65 or the connecting passage 66, and excess oil is discharged from the other of the separation passage 65 or the connecting 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 variable valve mechanism 30 is provided with a single oil control valve 71, which controls the connecting piston 61 and the separation piston 63. By using the oil control valve 71 to operate both the connecting piston 61 and the separation piston 63, the number of parts is reduced and the variable valve mechanism 30 is formed compactly. By changing the communication destination of each port with the oil control valve 71, it is possible to move either the connecting piston 61 or the separation piston 63 forward and move the other backward, thereby smoothly switching between connection and separation of the rocker arms 46a, 46b.

[0031] The connecting passage 66 is divided into a connecting working passage (first connecting oil passage) 81 and a connecting direct passage (second connecting oil passage) 85. Both the connecting working passage 81 and the connecting direct passage 85 extend from the oil control valve 71 to the connecting piston 61 of the switching mechanism 55. A part of the connecting working passage 81 is formed with a connecting oil groove 83 that passes oil at a predetermined rotation phase of the camshaft 31. As described above, the low speed cam 32, the high speed cam 33, and the exhaust cam 34 are formed on the camshaft 31, and the connecting oil groove 83 is partially formed on the outer circumferential surface of the camshaft 31 on one side of the exhaust cam 34.

[0032] The connecting operating passage 81 is divided into an upstream passage 82a and a downstream passage 82b by a connecting oil groove 83 of the camshaft 31. As the camshaft 31 rotates, communication between the upstream passage 82a and the downstream passage 82b of the connecting operating passage 81 is alternately repeated. As a result, oil is intermittently supplied from the oil control valve 71 to the connecting piston 61, and oil is intermittently discharged from the connecting piston 61 to the oil control valve 71. The specified rotational phase of the camshaft 31 is set between the end timing of the valve lift and before the start of the next valve lift.

[0033] In addition, the connecting direct passage 85 extends directly from the oil control valve 71 to the connecting piston 61 without passing through the connecting oil groove 83 of the camshaft 31. Therefore, oil is continuously supplied from the oil control valve 71 to the connecting piston 61 through the connecting direct passage 85, and oil is continuously discharged from the connecting piston 61 to the oil control valve 71 through the connecting direct passage 85. The connecting direct passage 85 is opened and closed by the connecting piston 61. The connecting direct passage 85 is opened when the connecting piston 61 is moving forward, and the connecting direct passage 85 is closed when the connecting piston 61 is moving backward.

[0034] In addition, the separation passage 65 is divided into a separation actuation passage (first separation oil passage) 86 and a separation direct passage (second separation oil passage) 89. Both the separation actuation passage 86 and the separation direct passage 89 extend from the oil control valve 71 to the separation piston 63 of the switching mechanism 55. A part of the separation actuation passage 86 is formed as a separation oil groove 88 that passes oil at a predetermined rotation phase of the camshaft 31. Similar to the connecting oil groove 83 on one side of the exhaust cam 34, the separation oil groove 88 is partially formed in the outer circumferential surface of the camshaft 31 on the other side of the low speed cam 32.

[0035] The separated operating passage 86 is divided into an upstream passage 87a and a downstream passage 87b by a separated oil groove 88 of the camshaft 31. As the camshaft 31 rotates, communication and disconnection between the upstream passage 87a and the downstream passage 87b of the separated operating passage 86 are alternately repeated. As a result, oil is intermittently supplied from the oil control valve 71 to the separation piston 63, and oil is intermittently discharged from the separation piston 63 to the oil control valve 71. Note that with the separated oil groove 88, the predetermined rotational phase of the camshaft 31 is also set between the end timing of the valve lift and before the start of the next valve lift.

[0036] Furthermore, the separate direct passage 89 extends directly from the oil control valve 71 to the separation piston 63 without passing through the separation oil groove 88 of the camshaft 31. Therefore, oil is continuously supplied from the oil control valve 71 to the separation piston 63 through the separate direct passage 89, and oil is continuously discharged from the separation piston 63 to the oil control valve 71 through the separate direct passage 89. The separate direct passage 89 is opened and closed by the separation piston 63. The separate direct passage 89 is opened when the separation piston 63 is moving forward, and is closed when the separation piston 63 is moving backward.

[0037] Although details will be described later, the connecting piston 61 is moved as a trigger by the oil supply through the connecting actuating passage 81, and the connecting piston 61 is held in a pushed-out state by the oil supply through the connecting direct passage 85. In addition, the separation piston 63 is moved as a trigger by the oil supply through the separation actuating passage 86, and the separation piston 63 is held in a pushed-out state by the oil supply through the separation direct passage 89.

[0038] 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.

[0039] A sliding chamber 43 is formed in the upper housing 42 on one side of the rocker arm 46b. A connecting piston 61 is installed in the sliding chamber 43. A pressing surface of the connecting piston 61 contacts the connecting pin 56, and the connecting pin 56 is moved to the other side by the connecting piston 61. Furthermore, a sliding chamber 44 is formed in the upper housing 42 on the other side of the rocker arm 46a. A separation piston 63 is installed in the sliding chamber 44. A pressing surface of the separation piston 63 contacts the return pin 58, and the return pin 58 is returned to one side by the separation piston 63. Furthermore, a sensing arm (not shown) is provided on the separation piston 63.

[0040] 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.

[0041] In the switching mechanism 55, the connecting piston 61 and the separation piston 63 are arranged in the same straight line, and the connecting pin 56 and the return pin 58 are arranged in the same straight line at a position eccentric from the center lines of the connecting piston 61 and the separation piston 63. The connecting actuation passage 81 and the separation actuation passage 86 are formed symmetrically with respect to the rocker arms 46a, 46b, and the connecting direct passage 85 and the separation direct passage 89 are formed symmetrically with respect to the rocker arms 46a, 46b. With this configuration, even if the switching mechanism 55 is provided with the connecting piston 61 and the separation piston 63, the variable valve gear 30 can be formed compactly.

[0042] 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 is equal to or higher than 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 state and the separated state of the rocker arms 46a, 46b from the movement of the tip of the sensing arm of the separation piston 63. 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.

[0043] As shown in Fig. 7, an upstream passage 82a of a connecting working passage 81 extends from the oil control valve 71 to the camshaft 31, and a downstream passage 82b of the connecting working passage 81 extends from the camshaft 31 to the connecting 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. A connecting oil groove 83 is formed in the circumferential direction on the circumference of the outer circumferential surface of the camshaft 31. A connecting direct passage 85 extends from the oil control valve 71 to the connecting piston 61, and is formed to be shorter than the connecting working passage 81.

[0044] When oil is supplied to the connecting piston 61, the oil passes only while the upstream passage 82a and the downstream passage 82b are in communication with each other via the connecting oil groove 83. The connecting 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 timing of the valve lift and the upstream passage 82a and the downstream passage 82b are separated from each other before the valve lift starts. That is, the camshaft 31 is formed with the connecting oil groove 83 so that the oil passes at a predetermined rotation phase that avoids the valve lift to supply the oil to the connecting piston 61 and also to discharge the oil from the connecting piston 61.

[0045] Furthermore, an upstream passage 87a of a separated working passage 86 extends from the oil control valve 71 to the camshaft 31, and a downstream passage 87b of the separated working passage 86 extends from the camshaft 31 to the separation piston 63. The downstream end of the upstream passage 87a and the upstream end of the downstream passage 87b are positioned on the same circumference on the outer circumferential surface of the camshaft 31. A separated oil groove 88 is formed in the circumferential direction on the circumference of the outer circumferential surface of the camshaft 31. A separated direct passage 89 extends from the oil control valve 71 to the separation piston 63, and is formed to be shorter than the separated working passage 86.

[0046] When oil is supplied to the separated piston 63, the oil passes through the separated oil groove 88 only while the upstream passage 87a and the downstream passage 87b are in communication with each other. The separated oil groove 88 is formed so that the upstream passage 87a and the downstream passage 87b are in communication with each other at the end of the valve lift and the upstream passage 87a and the downstream passage 87b are separated from each other before the start of the valve lift. That is, the separated oil groove 88 is formed in the camshaft 31 so that the oil passes through the separated piston 63 at a predetermined rotation phase that avoids the valve lift, and the oil is supplied to the separated piston 63 and the separated oil groove 88 is also formed so that the oil is discharged from the separated piston 63.

[0047] When the rocker arms 46a, 46b are connected, oil begins to be supplied to the connecting piston 61 at the end of the valve lift, and oil begins to be discharged from the separation piston 63. The connecting operation of the rocker arms 46a, 46b is completed before the start of the valve lift, so the rocker arms 46a, 46b are not connected in the middle of the valve lift. After oil is supplied from the connecting operating passage 81 to the connecting piston 61, oil is supplied from the connecting direct passage 85 to the connecting piston 61. There is a risk that the connecting piston 61 will move if only the connecting operating passage 81 is supplied with oil, but the supply of oil from the connecting direct passage 85 holds the connecting piston 61 stably.

[0048] When the rocker arms 46a, 46b are separated, oil begins to be supplied to the separation piston 63 at the end of the valve lift, and oil begins to be discharged from the connecting piston 61. The separation operation of the rocker arms 46a, 46b is completed before the start of the valve lift, so the rocker arms 46a, 46b are not separated in the middle of the valve lift. After oil is supplied to the separation piston 63 from the separation actuation passage 86, oil is supplied to the separation piston 63 from the separation direct passage 89. There is a risk that the separation piston 63 will move if only the separation actuation passage 86 is supplied with oil, but the supply of oil from the separation direct passage 89 holds the separation piston 63 stably.

[0049] The connecting and separating operations of the variable valve gear will be described with reference to Figures 8 and 9. Figure 8 is an explanatory diagram of the connecting operation of the variable valve gear of this embodiment. Figure 9 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 8 and 9.

[0050] As shown in Fig. 8(A), a connecting piston 61 is installed in a cylindrical sliding chamber 43 of an upper housing 42. The downstream end of a connecting operation passage 81 (downstream passage 82b) opens at the back surface of the sliding chamber 43, and the downstream end of a connecting direct passage 85 opens at the inner peripheral surface of the sliding chamber 43. The direction in which oil is supplied from the connecting operation passage 81 to the connecting piston 61 is the forward / retract direction of the connecting piston 61, and the direction in which oil is supplied from the connecting direct passage 85 to the connecting piston 61 is the radial direction of the connecting piston 61. During low-speed operation, the connecting piston 61 retracts, and the downstream end of the connecting direct passage 85 is blocked by the outer peripheral surface of the connecting piston 61.

[0051] The separation piston 63 is installed in the cylindrical sliding chamber 44 of the upper housing 42. The downstream end of a separation actuation passage 86 (downstream passage 87b) opens at the back surface of the sliding chamber 44, and the downstream end of a separation direct passage 89 opens at the inner peripheral surface of the sliding chamber 44. The direction in which oil is supplied from the separation actuation passage 86 to the separation piston 63 is the direction in which the separation piston 63 moves forward and backward, and the direction in which oil is supplied from the separation direct passage 89 to the separation piston 63 is the radial direction of the separation piston 63. During low-speed operation, the separation piston 63 moves forward, and the downstream end of the separation direct passage 89 is opened by the outer peripheral surface of the separation piston 63.

[0052] During low-speed operation, the separation piston 63 advances and the connecting piston 61 retreats. The advancement of the separation piston 63 and the retreat of the connecting piston 61 push the connecting pin 56 into the return pin 58. The flange of the return pin 58 abuts against the rocker arm 46a, and the return pin 58 is positioned at the initial position. At this time, the tip 57 of the connecting pin 56 contacts the tip 59 of the return pin 58 at the 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.

[0053] When switching from low-speed operation to high-speed operation begins, oil begins to be supplied from the oil control valve 71 to the connecting piston 61, and oil begins to be discharged from the separation piston 63 to the oil control valve 71. At this time, while the upstream passage 82a and the downstream passage 82b are in communication with each other via the connecting oil groove 83 of the camshaft 31, that is, while the camshaft 31 is in a predetermined rotation phase that avoids valve lift, oil is supplied to the connecting piston 61. The connecting piston 61 moves forward as hydraulic pressure acts on the connecting piston 61, and the separation piston 63 moves backward as hydraulic pressure is released from the separation piston 63, and the connecting pin 56 is pushed in by the connecting piston 61.

[0054] 8(B), in the initial stage of switching from low-speed operation to high-speed operation, the forward movement of the connecting piston 61 pushes the return pin 58 out of the connecting pin 56, and part of the connecting pin 56 begins to enter the accommodation hole 48a of the rocker arm 46a. At this point, the connecting pin 56 is not deeply inserted into the accommodation hole 48a of the rocker arm 46a, and the connection between the rocker arms 46a, 46b is incomplete. Since no valve lift occurs in the intake valve 35, the connecting pin 56 does not come out of the rocker arm 46a due to the valve lift while the rocker arms 46a, 46b are being connected.

[0055] As shown in Fig. 8(C), after switching to high-speed operation, the connecting piston 61 is pushed by hydraulic pressure to a position where the 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 connecting piston 61 opens the downstream end of the connecting direct passage 85, and the supply of oil through the connecting direct passage 85 holds the connecting piston 61 in the forward position, maintaining the connected state of the rocker arms 46a, 46b.

[0056] 9(A), when switching from high-speed operation to low-speed operation starts, oil starts to be supplied from the oil control valve 71 to the separation piston 63, and oil starts to be discharged from the connecting piston 61 to the oil control valve 71. At this time, while the upstream passage 87a and the downstream passage 87b are in communication with each other via the separation oil groove 88 of the camshaft 31, that is, while the camshaft 31 is in a predetermined rotation phase that avoids valve lift, oil is supplied to the separation piston 63. The separation piston 63 moves forward as hydraulic pressure acts on the separation piston 63, and the connecting piston 61 moves backward as hydraulic pressure is released from the connecting piston 61, and the connecting pin 56 is pushed back by the separation piston 63 via the return pin 58.

[0057] 9(B), in the initial stage of switching from high-speed to low-speed operation, the forward movement of separation piston 63 pushes connecting pin 56 back against return pin 58, and a part of connecting pin 56 starts to come out of 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 separation of 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 during separation of rocker arms 46a, 46b.

[0058] As shown in Fig. 9(C), after switching to low-speed operation, the connecting piston 61 is pushed back by the separation piston 63 to a position where the stroke is minimum. As the connecting piston 61 moves backward, 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. In addition, the forward movement of the separation piston 63 opens the downstream end of the separation direct passage 89, and the separation piston 63, receiving hydraulic pressure from the separation direct passage 89, holds the connecting piston 61 in the backward position, thereby maintaining the separated state of the rocker arms 46a, 46b.

[0059] 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 connecting piston 61, the connecting piston 61 moves forward at a predetermined rotational phase of the camshaft 31 that avoids valve lift, so that the connection of the rocker arms 46a, 46b is not hindered by the valve lift. Also, when oil is supplied from the oil control valve 71 to the separation piston 63, the separation piston 63 moves forward at a predetermined rotational phase of the camshaft 31 that avoids valve lift, so that the separation of the rocker arms 46a, 46b is not hindered by the valve lift.

[0060] In this embodiment, the variable valve mechanism is provided with a single oil control valve, but the variable valve mechanism may be provided with an oil control valve for the connecting piston and an oil control valve for the separated piston separately.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] Further, in this embodiment, the rocker arms are adjacent to each other, but the rocker arms may be spaced apart.

[0066] 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.

[0067] As described above, the first embodiment is a variable valve gear (30) capable of changing a valve lift amount in a cylinder head (23), comprising a camshaft (31) on which a plurality of cams (low speed cam 32, high speed cam 33) with 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 the hydraulic pressure for the switching mechanism, the switching mechanism has a connecting piston (61) and a separation piston (63) that move back and forth by hydraulic pressure, the plurality of rocker arms are connected by the advancement of the connecting piston, the plurality of rocker arms are separated by the advancement of the separation piston, and the oil control valve advances the connecting piston at a predetermined rotation phase of the camshaft and advances the separation piston at a predetermined rotation phase of the camshaft. According to this configuration, when oil is supplied to the connecting piston from the oil control valve, the connecting piston advances at a predetermined rotation phase of the camshaft that avoids the valve lift, so that the connection of the plurality of rocker arms is not hindered by the valve lift. In addition, when oil is supplied to the separation piston from the oil control valve, the separation piston moves forward at a specified rotational phase of the camshaft that avoids valve lift, so that separation of the multiple rocker arms is not hindered by valve lift.

[0068] In the second embodiment, in the first embodiment, a plurality of rocker arms are connected by the forward movement of the connecting piston and the backward movement of the separation piston, and a plurality of rocker arms are separated by the forward movement of the separation piston and the backward movement of the connecting piston, a first connecting oil passage (connecting operating passage 81) and a second connecting oil passage (connecting direct passage 85) extend from the oil control valve to the connecting piston, a first separated oil passage (separated operating passage 86) and a second separated oil passage (separated direct passage 89) extend from the oil control valve to the separated piston, a portion of the first connecting oil passage is formed by a connecting oil groove (83) that passes oil at a predetermined rotation phase of the camshaft, and a portion of the first separated oil passage is formed by a camshaft. The connecting piston is formed by a separation oil groove (88) that passes oil at a predetermined rotation phase of the camshaft, the second connecting oil passage is opened during the forward movement of the connecting piston and closed during the backward movement of the connecting piston, the second separate oil passage is opened during the forward movement of the connecting piston and closed during the backward movement of the connecting piston, the oil control valve supplies oil to the connecting piston and discharges oil from the connecting piston, the connecting piston advances and the separated piston retreats at a predetermined rotation phase of the camshaft, the oil control valve supplies oil to the separating piston and discharges oil from the connecting piston, the separating piston advances and the connecting piston retreats at a predetermined rotation phase of the camshaft. According to this configuration, when oil is supplied from the oil control valve to the connecting piston, oil is supplied to the connecting piston through the connecting oil groove at a predetermined rotation phase of the camshaft that avoids valve lift. The multiple rocker arms are connected by the forward movement of the connecting piston and the backward movement of the separating piston. Also, the second connecting oil passage is opened during the forward movement of the connecting piston, and the connecting piston is held in the forward position by the hydraulic pressure of the second connecting oil passage, so that the connected state of the multiple rocker arms is maintained. In addition, when oil is supplied to the separation piston from the oil control valve, the oil is supplied to the separation piston through the separation oil groove at a predetermined rotation phase of the camshaft that avoids valve lift. The advancement of the separation piston and the retreat of the connecting piston separate the multiple rocker arms.In addition, the second separation oil passage is opened during the forward movement of the separation piston, and the separation piston receives oil pressure from the second separation oil passage to hold the connecting piston in the retracted position, thereby maintaining the separated state of the multiple rocker arms.

[0069] In the third aspect, in the second aspect, the connecting oil groove and the separating oil groove are formed so that the 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, the 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 and separating operation of the multiple rocker arms are not hindered by the valve lift.

[0070] In a fourth aspect, in the second or third aspect, the connecting piston and the separated piston are arranged in the same straight line, and the first connecting oil passage and the second connecting oil passage are formed symmetrically with the first separated oil passage and the second separated oil passage across the multiple rocker arms. With this configuration, even if the connecting piston and the separated piston are provided in the switching mechanism, the variable valve gear can be formed compactly.

[0071] A fifth aspect is any one of the first to fourth aspects, in which the oil control valve is provided with a connection port (76) for controlling the connection piston, a separation port (77) for controlling the separation piston, an input port (74) connected to an oil supply passage, and a drain port (75) connected to a drain passage, and the input port is connected to either the connection port or the separation port, and the drain port is connected to the other of the connection port or the separation port. With this configuration, the connection piston and the separation piston are controlled by a single oil control valve, so that the variable valve gear can be formed compactly. By changing the communication destination of each port with the oil control valve, it is possible to smoothly switch between connection and separation of the multiple rocker arms.

[0072] 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.

[0073] 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]

[0074] 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: Connected piston 63: Separate piston 71: Oil control valve 74: Input port 75: Separate port 76: Connection port 77: Drain port 81: connecting working passage (first connecting oil passage) 83: Connecting oil groove 85: Direct connecting passage (second connecting oil passage) 86: Separation operating passage (first separation oil passage) 88: Separation oil groove 89: Separate direct passage (second separate oil passage)

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 connecting piston and a separating piston that move forward and backward by hydraulic pressure, The plurality of rocker arms are connected together by the forward movement of the connecting piston, The advancement of the separation piston separates the rocker arms, a variable valve mechanism, wherein the oil control valve advances the connecting piston at a predetermined rotational phase of the camshaft and advances the separated piston at a predetermined rotational phase of the camshaft.

2. The plurality of rocker arms are connected by the forward movement of the connecting piston and the backward movement of the separation piston, and the plurality of rocker arms are separated by the forward movement of the separation piston and the backward movement of the connecting piston, a first connecting oil passage and a second connecting oil passage extend from the oil control valve to the connecting piston, and a first separated oil passage and a second separated oil passage extend from the oil control valve to the separated piston, a portion of the first connecting oil passage is formed by a connecting oil groove through which oil passes at a predetermined rotational phase of the camshaft, and a portion of the first separated oil passage is formed by a separated oil groove through which oil passes at a predetermined rotational phase of the camshaft, the second connecting oil passage is opened during the advancement of the connecting piston and closed during the retreatment of the connecting piston, and the second separated oil passage is opened during the advancement of the separation piston and closed during the retreatment of the separation piston, the oil control valve supplies oil to the connecting piston and discharges oil from the separating piston, thereby advancing the connecting piston and retracting the separating piston at a predetermined rotation phase of the camshaft; 2. The variable valve device according to claim 1, wherein the oil control valve supplies oil to the separated piston and discharges oil from the connected piston, thereby advancing the separated piston and retracting the connected piston at a predetermined rotational phase of the camshaft.

3. 3. The variable valve device according to claim 2, wherein the connecting oil groove and the separating oil groove are 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 where no valve lift occurs.

4. 4. The variable valve mechanism according to claim 2, wherein the connecting piston and the separated piston are arranged in the same straight line, and the first connecting oil passage and the second connecting oil passage are formed symmetrically with the first separated oil passage and the second separated oil passage across the plurality of rocker arms.

5. the oil control valve is provided with a connection port for controlling the connection piston, a separation port for controlling the separation piston, an input port connected to an oil supply passage, and a drain port connected to a drain passage, 3. The variable valve device according to claim 1, wherein the input port is connected to one of the connection port and the separation port, and the drain port is connected to the other of the connection port and the separation port.

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