Variable valve timing system

Abstract

To provide a variable valve gear for capable of making components common while suppressing increase in a size of an engine.SOLUTION: In a cylinder head (23), a cam chain (31) is installed at a center in a predetermined direction where a plurality of cylinders (29) is arranged side by side, and a spark plug (19) is installed at both side walls recessed in a predetermined direction. In a variable valve gear (40) for the cylinder head, there are provided in each cylinder a rocker shaft (46) extending in a predetermined direction, a plurality of rocker arms (51a, 51b) supported by the rocker shaft, a connection pin (61) installed in a pin hole of one rocker arm, a return pin (62) installed in a pin hole of the other rocker arm, a thrust member (63) for forcing the connection pin to push the return pin into the other side, and a repulsion member (64) for forcing the return pin to push the connection pin back to one side. The connection pin, the return pin, the thrust member, and the repulsion member are each away from the spark plug in the direction perpendicular to the predetermined direction in plan view.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Conventionally, as a variable valve device, one known device switches valve operations by connecting a plurality of rocker arms (see, for example, Patent Document 1). In the variable valve device described in Patent Document 1, a pair of rocker arms are installed adjacent to each other, and a connecting pin is installed in the pin hole of one of the rocker arms. By pushing a part of the connecting pin into the pin hole of the other rocker arm, the pair of rocker arms are connected and the pair of valves are operated simultaneously. By allowing a part of the connecting pin to come out of the pin hole of the other rocker arm, the connection state of the pair of rocker arms is released and only one side valve is operated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the other rocker arm described in Patent Document 1, a spring pin for pushing back the connecting pin into the pin hole is installed, which causes the rocker arm to be enlarged. In a multi-cylinder engine where a cam chain is installed at the center in the cylinder arrangement direction and spark plugs are installed outside in the cylinder arrangement direction, it is difficult to secure a wide space between the cam chain and the spark plugs. Therefore, when adopting the rocker arm of Patent Document 1, it is necessary to enlarge the engine. Further, if a spring pin is installed inside the rocker arm, the same rocker arm cannot be used for both cylinders sandwiching the cam chain, and commonization of parts cannot be achieved.

[0005] This invention has been made in view of the above, and aims to provide a variable valve timing device that can suppress the increase in engine size and enable the commonality of parts. [Means for solving the problem]

[0006] A variable valve timing device according to one aspect of the present invention is a variable valve timing device capable of changing the valve operation of a cylinder head in which a cam chain is installed in the center of a predetermined direction in which a plurality of cylinders are arranged, and spark plugs are installed in recessed outer walls on both sides in the predetermined direction, and the device comprises a rocker shaft extending along a predetermined direction within the cylinder head, a plurality of rocker arms pivotably supported on the rocker shaft, a connecting pin installed in a pin hole of a rocker arm on one side of the predetermined direction, a return pin installed in a pin hole of a rocker arm on the other side of the predetermined direction, a pressing member that causes the connecting pin to push the return pin toward the other side, and a repulsion member that causes the return pin to push the connecting pin toward the one side, wherein the connecting pin, the return pin, the pressing member, and the repulsion member are detached from the spark plug in a direction perpendicular to the predetermined direction in a plan view. [Effects of the Invention]

[0007] According to one embodiment of the variable valve timing device of the present invention, when the return pin is pushed to the other side via the connecting pin by the pressing member, the connecting pin partially enters the pin hole of the rocker arm on the other side from the pin hole of the rocker arm on the one side, thereby connecting the multiple rocker arms. When the connecting pin is pushed back to the one side via the return pin by the repulsion member, the connecting pin comes out of the pin hole of the rocker arm on the other side, and the connection of the multiple rocker arms is released. By installing the connecting pin, return pin, pressing member, and repulsion member in a space outside the concave recess of the cylinder head, the degree of freedom in component layout is improved and the size of the engine can be kept down. Furthermore, the same rocker arm can be used for multiple cylinders to achieve component commonality. [Brief explanation of the drawing]

[0008] [Figure 1] This is a left side view of the engine and vehicle frame in this embodiment. [Figure 2] This is a perspective view of the inside of the cylinder head in this embodiment. [Figure 3] This is a perspective view of the variable valve timing device of this embodiment. [Figure 4] This is a top view of the inside of the cylinder head in this embodiment. [Figure 5] This is a schematic diagram of the operating passage and shortcut passage in the embodiment. [Figure 6] This is an explanatory diagram of the coupling operation of the variable valve timing device in this embodiment. [Modes for carrying out the invention]

[0009] A variable valve timing device according to one aspect of the present invention is installed in a cylinder head in which a cam chain is mounted in the center of a predetermined direction in which a plurality of cylinders are arranged, and spark plugs are installed in recessed areas on both sides of the outer wall in the predetermined direction. The variable valve timing device modifies the valve operation in this cylinder head. The variable valve timing device is provided with a rocker shaft, a plurality of rocker arms, a connecting pin, a return pin, a pressing member, and a repulsion member for each cylinder. The rocker shaft extends within the cylinder head along a predetermined direction, and a plurality of rocker arms are pivotably supported on the rocker shaft. A connecting pin is installed in the pin hole of a rocker arm on one side of the predetermined direction, and a return pin is installed in the pin hole of a rocker arm on the other side of the predetermined direction. When the return pin is pushed to the other side via the connecting pin by the pressing member, the connecting pin partially enters the pin hole of the rocker arm on the other side from the pin hole of the rocker arm on the one side, connecting the plurality of rocker arms. When the connecting pin is pushed back to the one side via the return pin by the repulsion member, the connecting pin comes out of the pin hole of the rocker arm on the other side, and the connection of the plurality of rocker arms is released. The connecting pin, return pin, pressing member, and repulsion member detach from the spark plug in a direction perpendicular to a predetermined direction in a plan view, thereby improving the freedom of component layout and preventing the engine from becoming larger. Furthermore, the same rocker arm can be used for multiple cylinders, enabling the commonality of parts. [Examples]

[0010] The following description of this embodiment will be given in detail with reference to the attached drawings. Figure 1 is a left side view of the engine and vehicle frame of this embodiment. Figure 2 is a perspective view of the inside of the cylinder head of this embodiment. Figure 3 is a perspective view of the variable valve timing device of this embodiment. In the following figures, arrow FR indicates the front of the vehicle, arrow RE indicates the rear of the vehicle, arrow L indicates the left side of the vehicle, and arrow R indicates the right side of the vehicle. In the following description, the central side of the cylinder head in the left-right direction will be referred to as one side, and the outer side of the cylinder head in the left-right direction will be referred to as the other side.

[0011] As shown in Figure 1, the saddle-type vehicle is constructed by mounting various components such as the engine 20 and electrical system on a cradle-type body frame 10. The body frame 10 has a main tube 12 that extends rearward from the upper part of the head pipe 11 and then bends downward, and a down tube 13 that extends downward from the lower part 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, forming a mounting space for the engine 20 inside the body frame 10. The rear side of the engine 20 is supported by the main tube 12, and the front and bottom sides of the engine 20 are supported by the down tube 13.

[0012] The engine 20 is a parallel twin-cylinder engine and comprises a crankcase 21, a cylinder 22 mounted on the crankcase 21, a cylinder head 23 mounted on the cylinder 22, and a cylinder head cover 24 mounted on the cylinder head 23. A magneto cover 25 is attached to the left side of the crankcase 21 to cover the magneto (not shown) from the side. A sprocket cover 26 is attached behind the magneto cover 25 to cover the drive sprocket (not shown) from the side. A clutch cover (not shown) is attached to the right side of the crankcase 21 to cover the clutch (not shown) from the side.

[0013] A radiator 15 is installed in front of the engine 20 to dissipate heat from the engine's coolant. An oil control valve 16 is installed on the outer surface of the cylinder head cover 24 to control the hydraulic pressure to the variable valve train 40. Oil is supplied to the oil control valve 16 from the main gallery of the crankcase 21 through external piping 17. A valve train chamber is formed inside the cylinder head 23 and the cylinder head cover 24. The valve train chamber is equipped with a variable valve train 40 (see Figure 3) that changes the valve operation of the intake valve 33 (see Figure 3) and exhaust valve 34 (see Figure 3) by hydraulic pressure.

[0014] As shown in Figure 2, the engine 20 is a 4-valve, 2-cylinder engine, with a cam chain 31 installed between a pair of cylinders 29 (see Figure 4). The cam chain 31 is wrapped around a cam sprocket 32, and a variable valve timing device 40 is installed for each cylinder 29 on either side of the cam sprocket 32. The variable valve timing device 40 is equipped with a camshaft 41 that rotates integrally with the cam sprocket 32. Inside the cylinder head 23, cam housings 42a and 42b are installed spaced apart in the left-right direction (a predetermined direction) for each cylinder 29, and the camshaft 41 is rotatably supported by the mating surfaces of these cam housings 42a and 42b and the cylinder head 23.

[0015] Inside the cylinder head 23, four intake valves 33 (see Figure 3) are installed on the rear side of the camshaft 41, and four exhaust valves 34 are installed on the front side of the camshaft 41. The intake valves 33 are pressed in the closing direction by valve springs 35 (see Figure 3), and the exhaust valves 34 are pressed in the closing direction by valve springs 36. A low-speed cam 43, a high-speed cam 44, and an exhaust cam 45 (all see Figure 3) are formed on the outer circumferential surface of the camshaft 41. Each cam 43-45 is formed in a plate shape with a cam lobe protruding from a part of the base circle. The cam lobe of the high-speed cam 44 is higher than that of the low-speed cam 43 so that the valve lift amount of the high-speed cam 44 is greater than that of the low-speed cam 43.

[0016] The intake-side rocker shaft 46 and the exhaust-side rocker shaft 47 are supported on the opposing portions of the cam housings 42a and 42b. The intake-side rocker shaft 46 and the exhaust-side rocker shaft 47 are positioned above the camshaft 41, and the intake-side rocker shaft 46 and the exhaust-side rocker shaft 47 extend parallel to the camshaft 41. Also, the left and right side walls of the cylinder head 23 are recessed in a concave shape, and a pair of plug covers 18 are installed in the recess 28 of the cylinder head 23. An oil control valve 16 for supplying oil to the variable valve device 40 is installed on the rear side of the cylinder head 23.

[0017] The upper housing 70 is supported on both sides on the upper surfaces of the cam housings 42a and 42b. The upper housing 70 is formed in a ladder shape by housing fixing portions 71a and 71b that extend in the front-rear direction and first to third bridge portions 72 to 74 that extend in the left-right direction. The first bridge portion 72 extends along the intake-side rocker shaft 46, the second bridge portion 73 extends along the camshaft 41, and the third bridge portion 74 extends along the exhaust-side rocker shaft 47 (see FIG. 3). Lubricating oil is supplied from each of the bridge portions 72 to 74 of the upper housing 70 to the necessary parts of the valve operating components.

[0018] As shown in FIGS. 2 and 3, two types of rocker arms 51a and 51b are swingably supported on the intake-side rocker shaft 46 (only one of each is shown in FIG. 3), and a rocker arm 52 is swingably supported on the exhaust-side rocker shaft 47 (only one is shown in FIG. 3). The intake-side rocker arm 51a 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 51b is formed to be the force point of the rocker arm 51a. The left and right ends of the intake-side rocker arm 51a and the exhaust-side rocker arm 52 are bifurcated.

[0019] At one end of the intake-side rocker arm 51a, a roller 53a that rolls on the low-speed cam 43 is rotatably supported, and at the bifurcated other end of the rocker arm 51a, a pair of intake valves 33 are connected. At one end of the intake-side rocker arm 51b, a roller 53b that rolls on the high-speed cam 44 is rotatably supported, and the intake valve 33 is not connected to the other end of the rocker arm 51b. At one end of the exhaust-side rocker arm 52, a roller 54 that rolls on the exhaust cam 45 is rotatably supported, and at the bifurcated other end of the rocker arm 52, a pair of exhaust valves 34 are connected. The rocker arms 51a and 51b are formed to be connectable.

[0020] During low and medium engine speeds, the rocker arms 51a and 51b are not connected. Therefore, the rocker arm 51a is swung by the low-speed cam 43, and the rocker arm 51b is swung by the high-speed cam 44. Since a pair of intake valves 33 are connected to the rocker arm 51a, the pair of intake valves 33 are moved according to the rotation of the low-speed cam 43. Since the cam peak of the low-speed cam 43 is low, the valve lift amount of the pair of intake valves 33 is low. Since the intake valve 33 is not connected to the rocker arm 51b, the rocker arm 51b is idling according to the rotation of the high-speed cam 44.

[0021] During high engine speeds, the rocker arms 51a and 51b are connected. Therefore, the rocker arms 51a and 51b are integrally swung by the high-speed cam 44. Since a pair of intake valves 33 are connected to the rocker arm 51b via the rocker arm 51a, the pair of intake valves 33 are moved according to the rotation of the high-speed cam 44. Since the cam peak of the high-speed cam 44 is high, the valve lift amount of the pair of intake valves 33 is high. Thus, by switching the connection state of the rocker arms 51a and 51b, the low-speed cam 43 and the high-speed cam 44 that move the intake valve 33 are switched.

[0022] Each variable valve timing device 40 is provided with a switching mechanism that switches between the connected and disconnected states of the rocker arms 51a and 51b by hydraulic pressure. A connecting pin 61 is installed in the pin hole of the rocker arm 51b on one side (closer to the center) of the cylinder head 23 in the left-right direction (predetermined direction), and a return pin 62 is installed in the pin hole of the rocker arm 51a on the other side (closer to the outside) of the cylinder head 23 in the left-right direction. A hydraulic piston (pressing member) 63 is installed on one side of the rocker arm 51b, and a spring-loaded spring pin (rebound member) 64 is installed on the other side of the rocker arm 51a.

[0023] The hydraulic piston 63 pushes the return pin 62 toward the other side onto the connecting pin 61, and the spring pin 64 pushes the return pin 62 toward the connecting pin 61 toward one side. When the connecting pin 61 is pushed in by the hydraulic piston 63, a part of the connecting pin 61 enters the pin hole of rocker arm 51a through the pin hole of rocker arm 51b, connecting rocker arms 51a and 51b. When the connecting pin 61 is pushed back by the spring pin 64 via the return pin 62, a part of the connecting pin 61 comes out of the pin hole of rocker arm 51a, releasing the connection between rocker arms 51a and 51b.

[0024] Incidentally, in the cylinder head 23, the cam chain 31 is installed in the center in the left-right direction where the left and right cylinders 29 (see Figure 4) are lined up, and the spark plugs 19 (see Figure 4) are installed in recessed areas on both outer walls in the left-right direction. In such a cylinder head 23, the space between the cam chain 31 and the spark plugs 19 is narrowed, and the left and right cams of the camshaft 41 are moved towards the center side (cam chain 31 side) of the left and right cylinders 29. For this reason, the rocker arms for the left cylinder 29 and the rocker arms for the right cylinder 29 are usually formed in a left-right inverted shape, so a mold must be prepared for each part, which increases costs.

[0025] In particular, one configuration in which a pair of rocker arms for each cylinder are connected via a connecting pin, and a spring pin is installed in the bottomed pin hole of one of the rocker arms, is conceivable. However, with such a rocker arm, the pin holes for the left and right cylinders open in opposite directions, making it impossible to use the same rocker arm for both cylinders. Therefore, in the variable valve timing device 40 of this embodiment, the shape and component layout of the rocker arms 51a and 51b are devised to achieve the commonality of rocker arms 51a and 51b without increasing the size of the engine 20.

[0026] The component layout and oil passages of the variable valve timing device will be described below with reference to Figures 4 and 5. Figure 4 is a top view of the inside of the cylinder head in this embodiment. Figure 5 is a schematic diagram of the operating passage and shortcut passage in this embodiment.

[0027] As shown in Figure 4, within the cylinder head 23, the intake rocker shaft 46 and the exhaust rocker shaft 47 extend in the left-right direction (a predetermined direction). The intake rocker shaft 46 supports rocker arms 51a and 51b, and the exhaust rocker shaft 47 supports rocker arm 52. The rocker arm 51a, which is closer to the outside in the left-right direction, is the intake low-speed rocker arm, and the rocker arm 51b, which is closer to the center in the left-right direction, is the intake high-speed rocker arm. The rocker arms 51a and 51b are formed symmetrically with respect to the centerlines C1 and C2 that extend in the longitudinal direction.

[0028] More specifically, the centerline C1 of the rocker arm 51a passes through the cylinder center O, and the rocker arm 51a is formed symmetrically with respect to this centerline C1. The point of action side of the rocker arm 51a is bifurcated, with a pair of branched sections 57 extending to the left and right. The length of the pair of branched sections 57 is the same, and a pair of intake valves 33 are connected to the ends of the pair of branched sections 57. The pair of intake valves 33 are positioned symmetrically with respect to the centerline C1 passing through the cylinder center O. This layout allows the pair of branched sections 57 to be formed short, and the rocker arm 51a is compactly installed on the cylinder 29.

[0029] A roller 53a is supported on the force application side of the rocker arm 51a, and a return pin 62 is supported near the pivot point of the rocker arm 51a. The support portion (support point) 38a of the roller 53a and the support portion (support point) 39a of the return pin 62 are formed to be approximately the same width, thereby reducing the width dimension of the rocker arm 51a. The shapes of the support portion 58a of the roller 53a and the support portion 59a of the return pin 62 are also formed symmetrically with respect to the center line C1. Because the entire rocker arm 51a has a symmetrical shape with respect to the center line C1, the same rocker arm 51a can be used for both the left and right cylinders 29, thus enabling parts commonality.

[0030] Furthermore, the center line C2 of the rocker arm 51b passes to the left-right side of the cylinder center O, and the rocker arm 51b is formed symmetrically with respect to this center line C2. There is no arm portion on the side of the rocker arm 51b that is at the point of action, and a pair of intake valves 33 are not connected to the rocker arm 51b. The rocker arm 51b is located closer to the cam chain 31 than the rocker arm 51a, and the rocker arm 51b does not interfere with the concave recess 28 of the cylinder head 23. By utilizing the space on the cam chain 31 side where there is no recess 28, the rocker arm 51b is installed, which helps to keep the engine 20 from becoming too large.

[0031] The rocker arm 51b is adjacent to the rocker arm 51a, and the stem end of the intake valve 33 is located on the center line C2 of the rocker arm 51b. In this case, since there is no arm portion on the side of the rocker arm 51b that is at the point of action, the rocker arm 51b does not interfere with the branch portion 57 that extends from the side of the rocker arm 51a to the cam chain 31. The rocker arm 51b is positioned in front of this branch portion 57 of the rocker arm 51a, and the rocker arms 51a and 51b are compactly installed in the cylinder head 23, which helps to keep the engine 20 from becoming too large.

[0032] A roller 53b is supported on the force application side of the rocker arm 51b, and a connecting pin 61 is supported near the pivot point of the rocker arm 51b. The support portion (support point) 38b of the roller 53b and the support portion (support point) 39b of the connecting pin 61 are formed to be approximately the same width, thereby reducing the width dimension of the rocker arm 51b. The shapes of the support portion 58b of the roller 53b and the support portion 59b of the connecting pin 61 are also formed symmetrically with respect to the center line C2. Because the entire rocker arm 51b has a symmetrical shape with respect to the center line C2, the same rocker arm 51b can be used for both the left and right cylinders 29, thus enabling parts commonality.

[0033] The connecting pin 61, return pin 62, hydraulic piston 63, and spring pin 64 are detached from the spark plug 19 in the front-rear direction (perpendicular to the predetermined direction in a plan view). Even if the spring pin 64 is positioned outside the rocker arm 51a in the left-right direction, the spring pin 64 does not interfere with the concave recess 28 in which the spark plug 19 is installed. Even if the recess 28 in the cylinder head 23 does not provide ample space between the cam chain 31 and the spark plug 19, the spring pin 64 and other components can be installed using the space detached from the recess 28. Therefore, the freedom of component layout is improved, and the size of the engine 20 can be kept down.

[0034] At the rear of the cylinder head 23, a pair of hydraulic pistons 63 are installed symmetrically on either side of the cam chain 31. An oil control valve 16 (see Figure 2) is installed on the rear wall of the cylinder head 23 to supply hydraulic fluid to the pair of hydraulic pistons 63. The oil control valve 16 is positioned equidistant from the pair of hydraulic pistons 63 and directly behind the cam chain 31. Between the cam chain 31 and the pair of hydraulic pistons 63, an oil passage for hydraulic fluid is formed, flowing from the oil control valve 16 to the pair of hydraulic pistons 63.

[0035] Between the cam chain 31 and the hydraulic piston 63, the housing fixing portion 71a (see Figure 2) of the cam housing 42a and the upper housing 70 is located. An oil groove is formed on the lower surface of the housing fixing portion 71a, and when the housing fixing portion 71a is fixed to the cam housing 42a, an operating passage 85 (see Figure 5) and a shortcut passage 86 (see Figure 5) are formed as oil passages. In this way, even with a layout in which a pair of hydraulic pistons 63 are installed with the cam chain 31 in between, hydraulic fluid can be supplied evenly to the pair of hydraulic pistons 63 through the operating passage 85 and the shortcut passage 86. By forming oil passages in a narrow space, the size of the engine 20 can be kept down.

[0036] As shown in Figure 5, in the housing fixed portion 71a (see Figure 4), the upstream passage 87a of the operating passage 85 extends from the oil control valve 16 toward the camshaft 41, and the downstream passage 87b of the operating passage 85 extends from the camshaft 41 toward the hydraulic piston 63. The downstream end of the upstream passage 87a and the upstream end of the downstream passage 87b are located on the same circumference on the outer surface of the camshaft 41. An oil groove 89 is formed in the circumferential direction on the outer surface of the camshaft 41. The oil groove 89 functions as an operating passage that supplies hydraulic fluid to the hydraulic piston 63 together with the upstream passage 87a and the downstream passage 87b.

[0037] Oil is supplied from the oil control valve 16 to the hydraulic piston 63 only while the upstream passage 87a and the downstream passage 87b are in communication via the oil groove 89. At this time, the oil groove 89 is formed such that the upstream passage 87a and the downstream passage 87b are in communication at the end of the valve lift, and separate before the start of the valve lift. In other words, the oil groove 89 is formed such that oil is supplied from the oil control valve 16 to the hydraulic piston 63 at the end of the valve lift, and the supply of oil to the hydraulic piston 63 is completed before the start of the valve lift.

[0038] Since oil is supplied to the hydraulic piston 63 at the end of the valve lift, the coupling operation of the rocker arms 51a and 51b is not hindered by the valve lift. Also, since the coupling operation of the rocker arms 51a and 51b is completed before the valve lift starts, the rocker arms 51a and 51b are not coupled in the middle of the valve lift. Therefore, as the camshaft 41 rotates, oil is intermittently supplied from the oil control valve 16 to the hydraulic piston 63 through the operating passage 85, and the rocker arms 51a and 51b can be smoothly coupled via the coupling pin 61.

[0039] Furthermore, a shortcut passage 86 extends directly from the oil control valve 16 to the hydraulic piston 63. The shortcut passage 86 is shorter than the operating passage 85. A stepwise oil supply structure to the hydraulic piston 63 is formed so that oil is supplied to the hydraulic piston 63 from the shortcut passage 86 after oil is supplied to the hydraulic piston 63 from the operating passage 85. If only intermittent oil is supplied from the operating passage 85, there is a risk that the hydraulic piston 63 will move, but the direct supply of oil from the shortcut passage 86 keeps the hydraulic piston 63 stably held.

[0040] The coupling operation of the variable valve timing device will be explained with reference to Figure 6. Figure 6 is an explanatory diagram of the coupling operation of the variable valve timing device in this embodiment. Also, for the sake of explanation, the reference numerals from Figure 5 will be used as appropriate in Figure 6.

[0041] As shown in Figure 6(A), the upper housing 70 has a hydraulic chamber 82 formed in the connection portion 81a on one side of the rocker arm 51b, and a housing hole 83 formed in the connection portion 81b on the other side of the rocker arm 51a. A hydraulic piston 63 is installed in the hydraulic chamber 82, and a spring pin 64 is installed in the housing hole 83. The hydraulic piston 63 contacts the connecting pin 61 in the rocker arm 51b, and the spring pin 64 contacts the return pin 62 in the rocker arm 51a. The centerlines of the hydraulic piston 63 and the spring pin 64 are aligned, which suppresses wear due to uneven contact between the parts.

[0042] At low engine speeds, no oil is supplied from the oil control valve 16 to the hydraulic chamber 82. No pressing force is applied from the hydraulic piston 63 to the connecting pin 61, and the spring force of the spring pin 64 is acting on the return pin 62. The return pin 62 abuts against the rocker arm 51a, and the return pin 62 is positioned in its initial position. At this time, the other end 65 of the connecting pin 61 is in contact with one end 66 of the return pin 62 at the non-connected position P1 in the gap between the rocker arms 51a and 51b. The other end 65 of the connecting pin 61 is located outside the rocker arm 51b, and the rocker arms 51a and 51b are separated.

[0043] As shown in Figure 6(B), when the engine speed increases above a predetermined speed, oil is supplied from the oil control valve 16 to the hydraulic chamber 82. As the camshaft 41 rotates, the upstream passage 87a and the downstream passage 87b of the operating passage 85 are intermittently connected through the oil groove 89, and oil is intermittently supplied from the operating passage 85 to the hydraulic piston 63. At this time, the oil is supplied at the timing when the valve lift of the intake valve 33 ends, so as not to hinder the coupling operation of the rocker arms 51a and 51b. As a result, the hydraulic piston 63 is smoothly pushed out in the advance direction by the oil from the operating passage 85.

[0044] The hydraulic piston 63 pushes in the connecting pin 61, and the connecting pin 61 moves the spring pin 64 to the other side via the return pin 62. The other end 65 of the connecting pin 61 is moved to the other side from the unconnected position P1 to the connected position P2 in the rocker arm 51a. A part of the connecting pin 61 fits into the pin hole 55a of the rocker arm 51a, thereby connecting the rocker arms 51a and 51b via the connecting pin 61. The movement of the hydraulic piston 63 opens the downstream end of the shortcut passage 86, and the position of the hydraulic piston 63 is maintained by the continuous oil supply from the shortcut passage 86.

[0045] As shown in Figure 6(A), when the engine speed drops below a predetermined speed, oil is returned from the hydraulic piston 63 to the oil control valve 16. The hydraulic piston 63 releases the push of the connecting pin 61, and the spring pin 64's repulsive force pushes the return pin 62 back, pushing the connecting pin 61 to one side. The other end 65 of the connecting pin 61 moves to one side from the connected position P2 to the unconnected position P1. Then, a part of the connecting pin 61 comes out of the pin hole 55a of the rocker arm 51a, releasing the connection between the rocker arms 51a and 51b.

[0046] As described above, with the variable valve timing device 40 of this embodiment, when the hydraulic piston 63 pushes the return pin 62 to the other side via the connecting pin 61, the connecting pin 61 partially enters the pin hole of the rocker arm 51a through the pin hole of the rocker arm 51b, connecting the rocker arms 51a and 51b. When the spring pin 64 pushes the connecting pin 61 back to the other side via the return pin 62, the connecting pin 61 comes out of the pin hole of the rocker arm 51a, releasing the connection between the rocker arms 51a and 51b. By installing the connecting pin 61, return pin 62, hydraulic piston 63, and spring pin 64 in the space outside the concave recess 28 of the cylinder head 23, the degree of freedom in component layout is improved, and the size of the engine 20 can be kept down. Furthermore, the same rocker arms 51a and 51b can be used for both the left and right cylinders 29, enabling the commonality of parts.

[0047] In this embodiment, a pair of rocker arms are provided on the intake side of the variable valve train, but it is acceptable for the variable valve train to have multiple rocker arms on the intake side. For example, the variable valve train may have three or more rocker arms on the intake side.

[0048] Furthermore, although a hydraulic piston is used as an example of a pressing member in this embodiment, any member that pushes the connecting pin inward toward the other side will suffice as the pressing member.

[0049] Furthermore, although a spring pin is used as an example of a repulsion member in this embodiment, any member that causes the return pin to push the connecting pin back in one direction can be used as the repulsion member.

[0050] Furthermore, although the engine has a pair of cylinders in this embodiment, the engine may have three or more cylinders.

[0051] Furthermore, although flange pins are used for the connecting pin and return pin in this embodiment, straight pins may also be used for the connecting pin and return pin.

[0052] Furthermore, although a seesaw-type rocker arm was used as an example in this embodiment, the type of rocker arm is not particularly limited, and a finger-follower type rocker arm may also be used.

[0053] Furthermore, although multiple rocker arms are adjacent to each other in this embodiment, multiple rocker arms may be spaced apart.

[0054] In this embodiment, while the upper housing has an operating passage and a shortcut passage, the cylinder head only needs to have an oil passage that can supply hydraulic fluid to the hydraulic piston.

[0055] Furthermore, the exhaust system of this embodiment is not limited to the engine of the saddle-type vehicle described above, but may be used in the engines of other vehicles. Also, the saddle-type vehicle is not limited to motorcycles, but can be any vehicle equipped with an engine. Moreover, the term "saddle-type vehicle" is not limited to all vehicles in which the driver sits straddling a seat, but also includes scooter-type vehicles in which the driver does not sit straddling a seat.

[0056] As described above, the first embodiment is a variable valve train (40) capable of changing the valve operation of a cylinder head (23) in which a cam chain (31) is installed in the center of a predetermined direction in which a plurality of cylinders (29) are lined up, and spark plugs (19) are installed in recessed outer walls on both sides in the predetermined direction. The variable valve train (40) comprises a rocker shaft (46) extending along a predetermined direction within the cylinder head, a plurality of rocker arms (51a, 51b) pivotably supported on the rocker shaft, a connecting pin (61) installed in a pin hole of a rocker arm on one side of the predetermined direction, a return pin (62) installed in a pin hole of a rocker arm on the other side of the predetermined direction, a pressing member (hydraulic piston 63) that causes the connecting pin to push the return pin toward the other side, and a repulsion member (spring pin 64) that causes the return pin to push the connecting pin toward the one side, with the connecting pin, return pin, pressing member, and repulsion member being detached from the spark plug in a direction perpendicular to the predetermined direction in a plan view. In this configuration, when the return pin is pushed to the other side via the connecting pin by the pressing member, the connecting pin partially enters the pin hole of the rocker arm on the other side from the pin hole of the rocker arm on the one side, connecting multiple rocker arms. When the connecting pin is pushed back to the one side via the return pin by the repulsion member, the connecting pin comes out of the pin hole of the rocker arm on the other side, and the connection between the multiple rocker arms is released. By installing the connecting pin, return pin, pressing member, and repulsion member in the space outside the concave recess of the cylinder head, the degree of freedom in component layout is improved and the size of the engine can be kept down. Furthermore, the same rocker arm can be used for multiple cylinders, enabling the commonality of parts.

[0057] In the second embodiment, as in the first embodiment, one rocker arm (51b) is a high-speed rocker arm, and the other rocker arm is a low-speed rocker arm (51a). The point of action side of the low-speed rocker arm is bifurcated to connect a pair of intake valves (33), and the center line (C1) extending in the longitudinal direction of the low-speed rocker arm passes through the cylinder center (O), with the pair of branching portions (57) of the low-speed rocker arm formed symmetrically with respect to this center line. With this configuration, the pair of intake valves are positioned symmetrically with respect to the center line of the high-speed rocker arm that passes through the cylinder center. Therefore, the pair of branching portions are formed to be short, and the rocker arm is compactly installed on the cylinder.

[0058] In the third embodiment, the high-speed rocker arm is located closer to the cam chain than the low-speed rocker arm, as in the second embodiment. With this configuration, the engine size can be kept down by installing the high-speed rocker arm on the cam chain side where there is no recess.

[0059] In the fourth embodiment, the stem end of the intake valve is located on the center line (C2) extending longitudinally from the high-speed rocker arm, as in the second or third embodiment. This configuration allows for a compact installation of the low-speed and high-speed rocker arms, thereby suppressing the increase in engine size.

[0060] The fifth embodiment is one of the first to fourth embodiments, in which multiple rocker arms are formed symmetrically with respect to a center line extending in the longitudinal direction of the multiple rocker arms, a roller (53b) is supported on the force application side of one rocker arm, and the support location of the roller (support portion 58b) and the support location of the connecting pin (support portion 59b) are approximately the same width, and a roller (53a) is supported on the force application side of the other rocker arm, and the support location of the roller (support portion 58a) and the support location of the return pin (support portion 58b) are approximately the same width. With this configuration, the width dimension of the multiple rocker arms can be reduced. The same rocker arm can be used for multiple cylinders, enabling the commonality of parts.

[0061] The sixth embodiment is one of the first to fifth embodiments, in which the plurality of cylinders are a pair of cylinders, the pressing members are a pair of hydraulically operated hydraulic pistons, the pair of hydraulic pistons are installed symmetrically on either side of the cam chain, an oil control valve is installed equidistant from the pair of hydraulic pistons to supply hydraulic fluid to the pair of hydraulic pistons, and an oil passage (operating passage 85, shortcut passage 86) is formed between the cam chain and the pair of hydraulic pistons, leading from the oil control valve to the pair of hydraulic pistons. With this configuration, even in a layout where the pair of hydraulic pistons are installed on either side of the cam chain, hydraulic fluid can be supplied evenly to the pair of hydraulic pistons. By forming oil passages in a narrow space, the size of the engine can be kept down.

[0062] Although this embodiment has been described, other embodiments may include combinations of the above embodiment and its modifications, either entirely or partially.

[0063] Furthermore, the technology of the present invention is not limited to the embodiments described above, and may be modified, substituted, or transformed in various ways without departing from the spirit of the technical idea. Moreover, if the technical idea can be realized in a different way by advances in the technology or by other derived technologies, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea. [Explanation of Symbols]

[0064] 16: Oil control valve 19: Spark plug 23: Cylinder head 28: Indentation 29 cylinders 31: Cam chain 40: Variable valve timing device 46: Rocker shaft 51a, 51b: Rocker arm 53a, 53b: Laura 57: Branching point 58a, 58b: Roller support 59a, 59b: Pin support 61: Connecting pin 62: Return pin 63: Hydraulic piston 64: Spring pin 85: Operating passage (oil passage) 86: Shortcut passage (oil passage) C1, C2: Centerlines of the rocker arms O: Cylinder center

Claims

1. A variable valve timing device that can change the valve operation of a cylinder head in which a cam chain is installed in the center of a predetermined direction in which multiple cylinders are arranged, and spark plugs are installed in recessed areas on both sides of the outer wall in the predetermined direction, A rocker shaft extending in a predetermined direction within the cylinder head, Multiple rocker arms are pivotably supported on the rocker shaft, A connecting pin is installed in the pin hole of the rocker arm on one side in a predetermined direction, A return pin is installed in the pin hole of the rocker arm on the other side in a predetermined direction, A pressing member that causes the connecting pin to be pushed in the return pin toward the other side, Each cylinder is provided with a return pin and a repulsion member that pushes the connecting pin back toward one side. A variable valve timing device characterized in that the connecting pin, the return pin, the pressing member, and the repulsion member are separated from the spark plug in a direction perpendicular to a predetermined direction when viewed from above.

2. The rocker arm on one side is a high-speed rocker arm, and the rocker arm on the other side is a low-speed rocker arm. The point of action of the aforementioned low-speed rocker arm is branched into two, and a pair of intake valves are connected to it. The variable valve timing device according to claim 1, characterized in that the center line extending in the longitudinal direction of the low-speed rocker arm passes through the cylinder center, and a pair of branching portions of the low-speed rocker arm are formed symmetrically with respect to the said center line.

3. The variable valve timing device according to claim 2, characterized in that the high-speed rocker arm is located closer to the cam chain than the low-speed rocker arm.

4. The variable valve timing device according to claim 2 or 3, characterized in that the stem end of the intake valve is located on the center line extending in the longitudinal direction of the high-speed rocker arm.

5. The plurality of rocker arms are formed symmetrically with respect to a center line extending in the longitudinal direction of the plurality of rocker arms, A roller is supported on the point of force application side of the aforementioned rocker arm, and the support location of the roller and the support location of the connecting pin are approximately the same width. A roller is supported on the point of force application side of the rocker arm on the other side, and the support location of the roller and the support location of the return pin are substantially the same width, as described in claim 1 or 2.

6. The aforementioned multiple cylinders are a pair of cylinders, The aforementioned pressing member is a pair of hydraulic pistons that operate by hydraulic pressure. The pair of hydraulic pistons are installed symmetrically on either side of the cam chain, An oil control valve is installed at a position equidistant from the pair of hydraulic pistons to supply hydraulic fluid to the pair of hydraulic pistons. The variable valve timing device according to claim 1 or 2, characterized in that an oil passage is formed between the cam chain and the pair of hydraulic pistons, from the oil control valve to the pair of hydraulic pistons.

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