Variable valve device

Abstract

A variable valve device (40) is configured to change a valve operation in an engine. The variable valve device includes a camshaft (41) on which a plurality of cams (44, 45) are provided adjacent to one another in a rotation axis direction, a plurality of rocker arms (35a, 35b) in contact with the plurality of cams and configured to move a valve, a switching mechanism (50) configured to switch between coupling and separation of the plurality of rocker arms, and an oil pressure detector (96) configured to detect oil pressure in a specific oil passage (79) of the engine. Oil flows into the specific oil passage according to a switching operation of the switching mechanism.

Description

TECHNICAL FIELD

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

[0002] In the related art, there is a variable valve device in which a pair of rocker arms are coupled to each other to switch a valve operation (for example, see Patent Literature 1). In the variable valve device, a coupling pin is installed in a pin hole of one of the rocker arms, and a release pin is installed in a pin hole of the other rocker arm. A part of the coupling pin pushes out the release pin and enters the pin hole of the other rocker arm to couple the pair of rocker arms, and a part of the coupling pin is pushed back by the release pin and comes out of the pin hole of the other rocker arm to separate the pair of rocker arms. A coupling state and a separation state of the pair of rocker arms are detected by a non-contact sensor.CITATION LISTPATENT LITERATURE

[0003] Patent Literature 1: JP2023-005734ASUMMARY OF INVENTIONTECHNICAL PROBLEM

[0004] However, the non-contact sensor used in the variable valve device described in Patent Literature 1 is expensive and requires a new circuit in an electronic control unit (ECU), which causes a problem of an increase in cost.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a variable valve device capable of determining a switching operation of coupling and separation between a plurality of rocker arms with an inexpensive configuration.SOLUTION TO PROBLEM

[0006] In order to solve the above problem, a variable valve device according to an aspect of the present invention is a variable valve device capable of changing a valve operation in an engine, and the variable valve device includes: a camshaft on which a plurality of cams are provided adj acent to one another in a rotation axis direction; a plurality of rocker arms in contact with the plurality of cams and configured to move a valve; a switching mechanism configured to switch between coupling and separation of the plurality of rocker arms; and an oil pressure detector configured to detect oil pressure in a specific oil passage of the engine, in which oil flows into the specific oil passage according to a switching operation of the switching mechanism.ADVANTAGEOUS EFFECTS OF INVENTION

[0007] According to the variable valve device in the aspect of the present invention, the oil pressure in the specific oil passage changes according to the switching operation of the switching mechanism. A coupling state and a separation state of the plurality of rocker arms switched by the switching mechanism are accurately determined by detecting the change in the oil pressure of the specific oil passage by the oil pressure detector. This eliminates the need for an expensive non-contact sensor for detecting the switching operation, and the coupling state and the separation state of the plurality of rocker arms can be determined at low cost by using the oil pressure detector.BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 is a right side view showing an engine and a vehicle body frame according to an embodiment. FIG. 2 is a right side view showing an upper portion of the engine from which a cylinder head cover is removed according to the present embodiment. FIG. 3 is a perspective view showing the upper portion of the engine from which the cylinder head cover is removed according to the present embodiment. FIG. 4 is a schematic top view showing a variable valve device according to the present embodiment. FIG. 5 is a schematic view showing the variable valve device according to the present embodiment. FIG. 6 is a top view showing the inside of a cylinder head according to the present embodiment. FIG. 7 is a cross-sectional view showing the cylinder head taken along a line A-A in FIG. 6. FIG. 8 is a cross-sectional view showing the cylinder head taken along a line B-B in FIG. 7. FIG. 9 is a cross-sectional view showing the cylinder head taken along a line C-C in FIG. 6. FIG. 10 is a cross-sectional view showing the cylinder head taken along a line D-D in FIG. 6. FIG. 11 is a cross-sectional view showing the cylinder head taken along a line E-E in FIG. 6. FIG. 12 is a view showing a coupling state and a separation state of intake rocker arms according to the present embodiment. FIG. 13 is a view showing a coupling state and a separation state of intake rocker arms according to a modification. DESCRIPTION OF EMBODIMENTS

[0009] A variable valve device according to an aspect of the present invention is configured to change a valve operation of an engine. A camshaft is provided with a plurality of cams adjacent to one another in a rotation axis direction, a plurality of rocker arms for moving a valve are in contact with the plurality of cams, and coupling and separation of the plurality of rocker arms are switched by a switching mechanism. Oil flows into a specific oil passage of an engine according to a switching operation of the switching mechanism, and oil pressure in the specific oil passage is detected by an oil pressure detector. Accordingly, the oil pressure of the specific oil passage changes according to the switching operation of the switching mechanism. A coupling state and a separation state of the plurality of rocker arms switched by the switching mechanism are accurately determined by detecting the change in the oil pressure of the specific oil passage by the oil pressure detector. This eliminates the need for an expensive non-contact sensor for detecting the switching operation, and a coupling state and a separation state of the plurality of rocker arms can be determined at low cost by using the oil pressure detector.Embodiment

[0010] Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. FIG. 1 is a right side view showing an engine and a vehicle body frame according to the present embodiment. FIG. 2 is a right side view showing an upper portion of the engine from which a cylinder head cover is removed according to the present embodiment. FIG. 3 is a perspective view showing the upper portion of the engine from which the cylinder head cover is removed according to the present embodiment. FIG. 4 is a schematic top view showing a variable valve device according to the present embodiment. In the following drawings, an arrow FR indicates a vehicle front side, an arrow RE indicates a vehicle rear side, an arrow L indicates a vehicle left side, and an arrow R indicates a vehicle right side. In FIG. 3, an oil control valve is omitted.

[0011] As shown in FIG. 1, a straddle-type vehicle includes various components such as an engine 20 and an electrical system that are mounted on a cradle type vehicle body frame 10. The vehicle body frame 10 includes a main tube 12 that extends rearward from an upper portion of a head pipe 11 and then is bent downward, and a down tube 13 that extends downward from a lower portion of the head pipe 11 and then is bent rearward. A rear end portion of the down tube 13 is joined to a lower end portion of the main tube 12 to form an installation space for the engine 20 inside the vehicle body frame 10. The main tube 12 supports a rear side of the engine 20, and the down tube 13 supports a front side and a lower side of the engine 20.

[0012] The engine 20 is a four-valve two-cylinder engine, 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 a side is attached to a right side surface of the crankcase 21. A magnet cover (not shown) that covers a magnet (not shown) from a side is attached to a left side surface of the crankcase 21. An oil pan 26 that stores oil is attached to a lower surface of the crankcase 21.

[0013] As shown in FIGS. 2 and 3, the engine 20 is a four-valve two-cylinder engine, and a cam chain 27 is installed between the two cylinders. The cam chain 27 is wound around a cam sprocket 28, and a variable valve device 40 is installed for each of left and right cylinders across the cam sprocket 28. The variable valve device 40 is provided with a camshaft 41 that rotates integrally with the cam sprocket 28. Cam housings 42a and 42b are provided for each cylinder in the cylinder head 23 in a manner of being separated from each other in a left-right direction (see FIG. 8 for the cam housing 42a), and the camshaft 41 is rotatably supported by mating surfaces of the cam housings 42a and 42b and the cylinder head 23.

[0014] In the cylinder head 23, four intake valves 31 are installed in rear of the camshaft 41, and four exhaust valves 33 are installed in front of the camshaft 41. The intake valve 31 is pressed in a valve closing direction by a valve spring 32, and the exhaust valve 33 is pressed in a valve closing direction by a valve spring 34. A low-speed cam 44, a high-speed cam 45, and an exhaust cam 46 (see FIG. 4) are formed adjacent to one another in the rotation axis direction on an outer circumferential surface of the camshaft 41. Each of the cams 44 to 46 is formed in a plate shape in which a cam ridge protrudes from a part of a base circle. A cam ridge of the high-speed cam 45 is higher than that of the low-speed cam 44 in order to make a valve lift amount of the high-speed cam 45 larger than that of the low-speed cam 44.

[0015] An intake rocker shaft 47 and an exhaust rocker shaft 48 are supported by opposing portions of the cam housings 42a and 42b. The intake rocker shaft 47 and the exhaust rocker shaft 48 are positioned above the camshaft 41, and the intake rocker shaft 47 and the exhaust rocker shaft 48 extend parallel to the camshaft 41. An upper housing 49 is supported at both ends on upper surfaces of the cam housings 42a and 42b, and a hydraulic piston 53 and a spring pin 54 are accommodated in the upper housing 49 (see FIG. 4). An oil control valve 60 (not shown in FIG. 3) is installed in rear of an upper surface of the cylinder head cover 24.

[0016] As shown in FIG. 4, the intake rocker shaft 47 is positioned in the rear of the camshaft 41, and the exhaust rocker shaft 48 is positioned in front of the camshaft 41. Two types of intake rocker arms 35a and 35b (only one is shown in FIG. 4) are supported in a swingable manner by the intake rocker shaft 47, and an exhaust rocker arm 37 (only one is shown in FIG. 4) is supported in a swingable manner by the exhaust rocker shaft 48. The intake rocker arm 35a and the exhaust rocker arm 37 are formed in a seesaw shape having a point of effort and a point of load, and the intake rocker arm 35b is formed to be the point of effort of the intake rocker arm 35a.

[0017] A roller 36a that is in rolling contact with the low-speed cam 44 is supported in a rotatable manner at one end of the intake rocker arm 35a, and a pair of the intake valves 31 are coupled to the other end of the intake rocker arm 35a which is bifurcated. A roller 36b that is in rolling contact with the high-speed cam 45 is supported in a rotatable manner at one end of the intake rocker arm 35b, and the intake valves 31 are not coupled to the other end of the intake rocker arm 35b. A roller 38 that is in rolling contact with the exhaust cam 46 is supported in a rotatable manner at one end of the exhaust rocker arm 37, and a pair of the exhaust valves 33 are coupled to the other end of the exhaust rocker arm 37 which is bifurcated. The intake rocker arms 35a and 35b are formed in a manner capable of being coupled to each other.

[0018] When an engine rotates at a low-speed and a medium speed, the intake rocker arms 35a and 35b are not coupled. Therefore, the intake rocker arm 35a is swung by the low-speed cam 44, and the intake rocker arm 35b is swung by the high-speed cam 45. Since the pair of intake valves 31 are coupled to the intake rocker arm 35a, the pair of intake valves 31 are moved in response to rotation of the low-speed cam 44. Since the cam ridge of the low-speed cam 44 is small, valve lift amounts of the pair of intake valves 31 are small. Since the intake valves 31 are not coupled to the intake rocker arm 35b, the intake rocker arm 35b is idle in response to rotation of the high-speed cam 45.

[0019] When the engine rotates at a high-speed, the intake rocker arms 35a and 35b are coupled to each other. Therefore, the intake rocker arms 35a and 35b are swung integrally by the high-speed cam 45. Since the pair of intake valves 31 are coupled to the intake rocker arm 35b via the intake rocker arm 35a, the pair of intake valves 31 are moved in response to rotation of the high-speed cam 45. Since the cam ridge of the high-speed cam 45 is large, valve lift amounts of the pair of intake valves 31 are large. In this manner, the low-speed cam 44 and the high-speed cam 45 that move the intake valves 31 are switched by switching a coupling state of the intake rocker arms 35a and 35b.

[0020] Each variable valve device 40 is provided with a switching mechanism 50 that switches between coupling and separation of the intake rocker arms 35a and 35b. The switching mechanism 50 is provided with a coupling pin 51 installed in a pin hole of the intake rocker arm 35b and a return pin 52 installed in a pin hole of the intake rocker arm 35a. The switching mechanism 50 is provided with the hydraulic piston (coupling member) 53 that is in contact with the coupling pin 51 from one side in a left-right direction, and the spring pin (separation member) 54 that is in contact with the return pin 52 from the other side in the left-right direction. The hydraulic piston 53 can be moved forward and backward by oil pressure, and the spring pin 54 can be moved forward and backward by expansion and contraction of a spring.

[0021] When oil is supplied to the hydraulic piston 53, the hydraulic piston 53 is moved forward against a spring force of the spring pin 54. As the hydraulic piston 53 is moved forward, the return pin 52 is pushed by the coupling pin 51, and a part of the coupling pin 51 enters the pin hole of the intake rocker arm 35a from the pin hole of the intake rocker arm 35b to couple the intake rocker arms 35a and 35b. When the oil is discharged from the hydraulic piston 53, the spring pin 54 is moved forward by a spring force. As the spring pin 54 is moved forward, the coupling pin 51 is pushed back by the return pin 52, and a part of the coupling pin 51 is pulled out of the pin hole of the intake rocker arm 35a to separate the intake rocker arms 35a and 35b.

[0022] In a general variable valve device, a non-contact sensor is used to recognize a switching operation of a switching mechanism. For example, a sensing arm is provided on a spring pin, a non-contact sensor is installed near a tip end of the sensing arm, and the switching operation of the switching mechanism is recognized based on a movement of the tip end of the sensing arm. In this case, an expensive non-contact sensor is required, and a dedicated driver circuit needs to be provided in an ECU. Therefore, in the present embodiment, the engine is provided with a measurement oil passage 79 through which the oil flows according to the switching operation of the switching mechanism 50, and an oil pressure detector 96 detects oil pressure in the measurement oil passage 79 to recognize the switching operation (see FIG. 5).

[0023] The variable valve device will be described with reference to FIG. 5. FIG. 5 is a schematic diagram showing the variable valve device according to the present embodiment.

[0024] As shown in FIG. 5, in the variable valve device 40, an oil supply passage 55 extends from the oil pan 26 toward the oil control valve 60. Oil is pumped up from the oil pan 26 by an oil pump 56 provided in an intermediate portion of the oil supply passage 55, and the oil is supplied to the oil control valve 60 through an oil filter 57. The oil control valve 60 is formed by a valve housing 61 in which a valve spool (not shown) is accommodated, and a solenoid 62 that moves the valve spool forward and backward. When the valve spool is moved forward and backward by the solenoid 62, an oil passage in the oil control valve 60 is switched.

[0025] An input port 63, a low-speed port 64, a high-speed port 65, and a drain port 66 are formed in the valve housing 61. The oil supply passage 55 communicates with the input port 63, a dead end passage 67 communicates with the low-speed port 64, a switching passage 69 communicates with the high-speed port 65, and a drain passage 68 communicates with the drain port 66. A discharge destination of the dead end passage 67 is closed, and the switching passage 69 extends from the oil control valve 60 toward the switching mechanism 50. The drain passage 68 extends from the oil control valve 60 to a position above the oil pan 26, and oil is dropped from an outlet of the drain passage 68 to the oil pan 26.

[0026] By moving a valve spool of the oil control valve 60, the input port 63 communicates with one of the low-speed port 64 and the high-speed port 65, and the drain port 66 communicates with the other one of the low-speed port 64 and the high-speed port 65. Oil is output from the oil control valve 60 to one of the dead end passage 67 and the switching passage 69, and remaining oil is discharged from the other one of the dead end passage 67 and the switching passage 69 to the oil control valve 60 (the drain passage 68). In this manner, oil pressure applied to the switching mechanism 50 is controlled by the oil control valve 60.

[0027] The switching passage 69 is divided into an actuation passage 71 and a direct passage 74, and both the actuation passage 71 and the direct passage 74 extend from the oil control valve 60 to the hydraulic piston 53 of the switching mechanism 50. A part of the actuation passage 71 is formed by an oil groove 73 through which oil is allowed to pass at a predetermined rotation phase of the camshaft 41. As described above, the low-speed cam 44, the high-speed cam 45, and the exhaust cam 46 (not shown in FIG. 5) are formed on the camshaft 41, and the oil groove 73 is formed in a part of an outer circumferential surface of the camshaft 41.

[0028] The actuation passage 71 is divided into an upstream passage 72a and a downstream passage 72b with the oil groove 73 of the camshaft 41 interposed therebetween. By rotating the camshaft 41, communication and separation between the upstream passage 72a and the downstream passage 72b of the actuation passage 71 are alternately repeated. The direct passage 74 directly extends from the oil control valve 60 to the hydraulic piston 53 without passing through the oil groove 73 of the camshaft 41. After the hydraulic piston 53 is moved in response to oil supply through the actuation passage 71, the hydraulic piston 53 is maintained in a state in which the hydraulic piston 53 is pushed by oil supply through the direct passage 74.

[0029] The coupling pin 51 is installed in a pin hole in an upper portion of the intake rocker arm 35b, and the return pin 52 is installed in a pin hole in an upper portion of the intake rocker arm 35a. A tip end of the return pin 52 is in contact with a tip end of the coupling pin 51. The upper housing 49 is formed with a hydraulic chamber 87 and a storage chamber 88, the hydraulic piston 53 is installed in the hydraulic chamber 87, and the spring pin 54 is installed in the storage chamber 88. A pressing surface of the hydraulic piston 53 is in contact with the coupling pin 51, and a pressing surface of the spring pin 54 is in contact with the return pin 52. The spring pin 54 has a cylindrical shape, and an oil groove 77 for lubrication is formed on an outer circumferential surface of the spring pin 54.

[0030] The switching mechanism 50 switches a coupling state of the intake rocker arms 35a and 35b by moving the coupling pin 51 by oil pressure. As described above, in a separation state of the intake rocker arms 35a and 35b, the pair of intake valves 31 are operated by the low-speed cam 44 via the intake rocker arms 35a. In the coupling state of the intake rocker arms 35a and 35b, the pair of intake valves 31 are operated by the high-speed cam 45 via the intake rocker arms 35a and 35b. In this manner, the switching mechanism 50 switches cams that move the pair of intake valves 31 by switching the coupling state of the intake rocker arms 35a and 35b by the coupling pin 51.

[0031] On a downstream side of the oil filter 57, oil is also supplied from the oil supply passage 55 to a lubrication circuit 78. Lubrication oil is also supplied from a part of the lubrication circuit 78 to the oil groove 77 of the spring pin 54. The measurement oil passage (specific oil passage) 79 extends from the storage chamber 88 of the spring pin 54, and the oil groove 77 communicates with the measurement oil passage 79 when the spring pin 54 is retracted. Oil pressure in the measurement oil passage 79 is detected by the oil pressure detector 96. As described above, the oil flows into the measurement oil passage 79 according to the switching operation of the switching mechanism 50, and a change in the oil pressure of the measurement oil passage 79 is detected by the oil pressure detector 96.

[0032] The engine 20 is provided with an engine control unit (ECU) 75 and an engine angle sensor 76. The engine angle sensor 76 detects an engine rotation speed, when the engine rotation speed is a predetermined rotation speed or more, the ECU 75 outputs a coupling command signal to the solenoid 62, and when the engine rotation speed is less than the predetermined rotation speed, the ECU 75 outputs a release command signal to the solenoid 62. The oil pressure detector 96 detects a change in the oil pressure of the measurement oil passage 79, and the ECU 75 determines the coupling state and the separation state of the intake rocker arms 35a and 35b. In the ECU 75, a command signal is compared with a determination result to determine a failure of the variable valve device 40 such as a switching operation failure.

[0033] Hereinafter, a lubrication passage for lubricating the switching mechanism in a lubrication circuit of the engine will be described with reference to FIGS. 6 to 11. FIG. 6 is a top view showing the inside of the cylinder head according to the present embodiment. FIG. 7 is a cross-sectional view showing the cylinder head taken along a line A-A in FIG. 6. FIG. 8 is a cross-sectional view showing the cylinder head taken along a line B-B in FIG. 7. FIG. 9 is a cross-sectional view showing the cylinder head taken along a line C-C in FIG. 6. FIG. 10 is a cross-sectional view showing the cylinder head taken along a line D-D in FIG. 6. FIG. 11 is a cross-sectional view showing the cylinder head taken along a line E-E in FIG. 6.

[0034] As shown in FIG. 6, the upper housing 49 is formed in a ladder shape by housing fixing portions 81a and 81b extending in the front-rear direction and first to third bridge portions 82 to 84 extending in the left-right direction. The housing fixing portions 81a and 81b are fixed to the cam housings 42a and 42b (see FIG. 8). The first bridge portion 82 couples the housing fixing portions 81a and 81b on an intake side of the cylinder head 23. The second bridge portion 83 couples the housing fixing portions 81a and 81b between the intake side and an exhaust side of the cylinder head 23. The third bridge portion 84 couples the housing fixing portions 81a and 81b on the exhaust side of the cylinder head 23.

[0035] The hydraulic chamber 87 (see FIG. 5) is formed in a coupling portion between the first bridge portion 82 and the housing fixing portion 81a. The storage chamber 88 (see FIG. 5) is formed in a coupling portion between the first bridge portion 82 and the housing fixing portion 81b. The hydraulic piston 53 (see FIG. 5) is installed in the hydraulic chamber 87, and the spring pin 54 (see FIG. 5) is installed in the storage chamber 88. The hydraulic chamber 87 and the storage chamber 88 are formed coaxially, and parallelism between the hydraulic piston 53 and the spring pin 54 is ensured. Hydraulic oil is supplied to the hydraulic chamber 87 through a hydraulic circuit different from that of the lubrication oil.

[0036] As shown in FIGS. 6 to 8, the cylinder head 23 is fixed to the crankcase 21 via the cylinder 22 by a plurality of head bolts 89. A gap between the head bolt 89 on an exhaust side and a bolt hole serves as an oil passage 93a, and an oil passage 93b extends obliquely from the oil passage 93a to the camshaft 41. Oil is guided from the crankcase 21 to a lubrication groove 93c around the camshaft 41 through the oil passages 93a and 93b. A lubrication passage 80a for the switching mechanism 50 and a lubrication passage 80b for the rocker arms 35a, 35b, and 37 are divided at the lubrication groove 93c around the camshaft 41. Description of the lubrication passage 80b for the rocker arms 35a, 35b, and 37 is omitted.

[0037] In the lubrication passage 80a for the switching mechanism 50, the housing fixing portion 81a at the center in the left-right direction is fixed to the cylinder head 23 via the cam housing 42a by a pair of housing bolts 95a. A gap between the housing bolt 95a on the intake side and a bolt hole serves an oil passage 93d extending from the lubrication groove 93c around the camshaft 41 to the intake rocker shaft 47. Oil is guided from the oil passage 93d to an oil passage 93e in the intake rocker shaft 47, and the oil flows from one end to the other end of the oil passage 93e. Oil is supplied from a plurality of supply holes 94a of the oil passage 93e in the intake rocker shaft 47 to shaft holes of the intake rocker arms 35a and 35b.

[0038] As shown in FIGS. 6 and 9, the housing fixing portion 81b on an outer side in the left-right direction is fixed to the cylinder head 23 via the cam housing 42b by a pair of housing bolts 95b. A gap between the housing bolt 95b on the intake side and a bolt hole serves as an oil passage 93f extending from an end portion of the oil passage 93e in the intake rocker shaft 47 to the housing fixing portion 81b. An oil passage 93h extends obliquely from an oil passage 93g on a mating surface between the housing fixing portion 81b and the cam housing 42b to the first bridge portion 82. The oil groove 77 of the spring pin 54 is coupled to an intermediate portion of the oil passage 93h, and an outer circumferential surface of the spring pin 54 is lubricated.

[0039] As shown in FIGS. 6 and 10, an oil passage 93i is formed in the first bridge portion 82, oil is guided from the oil passage 93h to the oil passage 93i, and the oil flows from the other end to one end of the oil passage 93i. The oil passage 93i is provided with five ejection holes 94b that are open to the atmosphere. The ejection holes 94b are positioned above contact portions of the hydraulic piston 53, the coupling pin 51, the return pin 52, and the spring pin 54, which are movable portions of the switching mechanism 50. Oil is ejected from the ejection holes 94b to the contact portions of the components, and the hydraulic piston 53, the coupling pin 51, the return pin 52, and the spring pin 54 are lubricated with the oil.

[0040] As shown in FIGS. 6 and 11, the measurement oil passage 79 extends from the spring pin 54 accommodated in the upper housing 49 to the cylinder head 23. A central oil passage of the oil pressure detector 96 is coupled to a lower end of the measurement oil passage 79, and oil pressure in the measurement oil passage 79 is detected by the oil pressure detector 96. A part of the oil supplied for lubricating the switching mechanism 50 flows into the measurement oil passage 79. Accordingly, the coupling state and the separation state of the intake rocker arms 35a and 35b are determined using the oil used for lubricating the movable portions of the switching mechanism 50. Further, insufficient oil pressure of the lubrication circuit 78 of the variable valve device 40 is detected based on the magnitude of the oil pressure of the oil pressure detector 96.

[0041] The coupling state and the separation state of the intake rocker arms will be described with reference to FIG. 12. FIG. 12 is a view showing the coupling state and the separation state of the intake rocker arms according to the present embodiment. (A) of FIG. 12 shows the separation state of the intake rocker arms, and (B) of FIG. 12 shows the coupling state of the intake rocker arms.

[0042] As shown in (A) of FIG. 12, during a low-speed operation, the hydraulic piston 53 is moved backward and the spring pin 54 is moved forward. The coupling pin 51 is pushed by the return pin 52 due to the backward movement of the hydraulic piston 53 and the forward movement of the spring pin 54. A flange of the return pin 52 abuts against the rocker arm 35a, and the return pin 52 is positioned at an initial position. At this time, a tip end 58 of the coupling pin 51 is in contact with a tip end 59 of the return pin 52 at a separation position P 1 in a gap C between the rocker arms 35a and 35b. The tip end 58 of the coupling pin 51 is positioned in the gap C between the rocker arms 35a and 35b, and the rocker arms 35a and 35b are separated from each other.

[0043] At this time, at the position where the spring pin 54 is moved forward, the measurement oil passage 79 is separated from the oil groove 77 on the outer circumferential surface of the spring pin 54. Therefore, oil is supplied from the oil passage 93h to the oil groove 77 of the spring pin 54, but oil from the oil passage 93h is not supplied to the measurement oil passage 79. The measurement oil passage 79 is open to the atmosphere through an inlet of the measurement oil passage 79 by being separated from the spring pin 54. The oil pressure drops greatly due to the measurement oil passage 79 being open to the atmosphere, and when the intake rocker arms 35a and 35b are separated from each other, low oil pressure is detected by the oil pressure detector 96.

[0044] As shown in (B) of FIG. 12, during a high-speed operation, the hydraulic piston 53 is moved forward and the spring pin 54 is moved backward. The return pin 52 is pushed by the coupling pin 51 due to the forward movement of the hydraulic piston 53 and the backward movement of the spring pin 54. A flange of the coupling pin 51 abuts against the rocker arm 35b, and the tip end 58 of the coupling pin 51 protrudes from the rocker arm 35b. At this time, the tip end 58 of the coupling pin 51 is in contact with the tip end 59 of the return pin 52 at a coupling position P2 of the rocker arm 35a. A part of the coupling pin 51 deeply enters a pin hole of the rocker arm 35a, and the rocker arms 35a and 35b are coupled to each other via the coupling pin 51.

[0045] At this time, at a position where the spring pin 54 is moved backward, the oil groove 77 on the outer circumferential surface of the spring pin 54 communicates with the measurement oil passage 79. Therefore, oil is supplied from the oil passage 93h to the measurement oil passage 79 through the oil groove 77 of the spring pin 54. The inlet of the measurement oil passage 79 is covered with the spring pin 54 to block the measurement oil passage 79 from the atmosphere. The oil pressure increases due to the measurement oil passage 79 being blocked from the atmosphere, and when the intake rocker arms 35a and 35b are coupled to each other, high oil pressure is detected by the oil pressure detector 96. In this manner, a change in the oil pressure is clearly detected by opening and blocking the measurement oil passage 79 to and from the atmosphere.

[0046] As described above, the forward movement of the spring pin 54 causes the measurement oil passage 79 and the oil groove 77 to be separated from each other so that the oil does not flow into the measurement oil passage 79, and the backward movement of the spring pin 54 causes the measurement oil passage 79 and the oil groove 77 to communicate with each other so that the oil flows into the measurement oil passage 79. The change in the oil pressure of the measurement oil passage 79 is interlocked with the forward and backward movement of the spring pin 54, and the coupling state and the separation state of the intake rocker arms 35a and 35b are accurately determined by the ECU 75 according to a detection result of the oil pressure detector 96. Further, by using the oil groove 77 for lubrication of the spring pin 54, the oil is allowed to flow into the measurement oil passage 79 without providing an extra oil passage in the engine 20.

[0047] As described above, according to the variable valve device 40 in the present embodiment, the oil pressure of the measurement oil passage 79 changes according to the switching operation of the switching mechanism 50. The coupling state and the separation state of the rocker arms 35a and 35b switched by the switching mechanism 50 are accurately determined by detecting the change in the oil pressure of the measurement oil passage 79 by the oil pressure detector 96. This eliminates the need for an expensive non-contact sensor for detecting the switching operation, and the coupling state and the separation state of the rocker arms 35a and 35b can be determined at low cost by using the oil pressure detector 96.

[0048] Although a configuration in which a part of the oil supplied for lubricating the switching mechanism flows into the measurement oil passage has been described in the embodiment described above, a part of oil supplied for actuating the switching mechanism may flow into the measurement oil passage. Hereinafter, a variable valve device according to a modification will be described with reference to FIG. 13. FIG. 13 is a view showing a coupling state and a separation state of intake rocker arms according to the modification. (A) of FIG. 13 shows the separation state of the intake rocker arms, and (B) of FIG. 13 shows the coupling state of the intake rocker arms. In the variable valve device according to the modification, the same components as those of the variable valve device according to the present embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0049] As shown in (A) of FIG. 13, the switching passage 69 extends from the oil control valve 60 toward the hydraulic piston 53, and the switching passage 69 branches from an intermediate portion to form an oil passage 97 extending toward the oil groove 77 of the spring pin 54. The measurement oil passage 79 is formed adjacent to the oil passage 97, and the oil passage 97 and the measurement oil passage 79 are formed in a manner capable of communicating with and separating from each other via the oil groove 77 by moving forward and backward the spring pin 54. The oil pressure detector 96 is coupled to the measurement oil passage 79, and the oil pressure in the measurement oil passage 79 is detected by the oil pressure detector 96.

[0050] During a low-speed operation, oil is discharged from the switching passage 69 and the oil passage 97 through the oil control valve 60. The hydraulic piston 53 is moved backward, the spring pin 54 is moved forward, and the rocker arms 35a and 35b are separated from each other. At a position where the spring pin 54 is moved forward, the measurement oil passage 79 is separated from the oil groove 77 on the outer circumferential surface of the spring pin 54. The measurement oil passage 79 is open to the atmosphere through an inlet of the measurement oil passage 79 by being separated from the spring pin 54. The oil pressure drops greatly due to the measurement oil passage 79 being open to the atmosphere, and when the intake rocker arms 35a and 35b are separated from each other, low oil pressure is detected by the oil pressure detector 96.

[0051] As shown in (B) of FIG. 13, during a high-speed operation, oil is supplied from the oil control valve 60 to the switching passage 69 and the oil passage 97. The hydraulic piston 53 is moved forward, the spring pin 54 is moved backward, and the rocker arms 35a and 35b are coupled to each other. At a position where the spring pin 54 is moved backward, the oil groove 77 on the outer circumferential surface of the spring pin 54 communicates with the measurement oil passage 79. The inlet of the measurement oil passage 79 is covered with the spring pin 54 to block the measurement oil passage 79 from the atmosphere. The oil pressure increases due to the measurement oil passage 79 being blocked from the atmosphere, and when the intake rocker arms 35a and 35b are coupled to each other, high oil pressure is detected by the oil pressure detector 96.

[0052] As described above, in the switching mechanism 50 of the variable valve device 40 according to the modification, the intake rocker arms 35a and 35b are switched between the coupling state and the separation state according to the oil pressure, and a part of the oil supplied for actuating the switching mechanism 50 flows into the measurement oil passage 79. Since the switching operation of the switching mechanism 50 and the change in the oil pressure in the measurement oil passage 79 are interlocked, the coupling state and the separation state of the plurality of rocker arms 35a and 35b are accurately determined according to a detection result of the oil pressure detector 96.

[0053] In the present embodiment, when the spring pin is moved backward, the measurement oil passage and the oil groove communicate with each other and the oil flows into the measurement oil passage. Alternatively, the measurement oil passage and the oil groove may communicate with each other and the oil may flow into the measurement oil passage when the spring pin is moved forward.

[0054] Further, in the present embodiment, the hydraulic piston is exemplified as the coupling member, and the spring pin is exemplified as the separation member. Alternatively, the coupling member and the separation member may be freely configured as long as when one of the coupling member and the separation member is moved forward, the other one is moved backward.

[0055] Further, in the present embodiment, the switching mechanism switches the coupling state and the separation state of the intake rocker arms according to the oil pressure. Alternatively, the switching mechanism may be freely configured as long as the switching mechanism can switch the coupling state and the separation state of the intake rocker arms. The switching mechanism may switch coupling and separation of the intake rocker arms according to electricity or the like.

[0056] Further, in the present embodiment, the variable valve device includes a pair of intake rocker arms. Alternatively, the variable valve device may include three or more intake rocker arms.

[0057] Further, in the present embodiment, a seesaw type rocker arm is described as an example. Alternatively, the type of the rocker arm is not particularly limited, and a finger follower type rocker arm may be used.

[0058] Further, in the present embodiment, a plurality of rocker arms are adjacent to one another. Alternatively, the plurality of rocker arms may be separated from one another.

[0059] Further, the oil pressure detector may be implemented by, for example, an oil pressure switch and an oil pressure sensor as long as the oil pressure in the measurement oil passage can be detected.

[0060] The variable valve device according to the present embodiment is not limited to being used in an engine of the straddle-type vehicle described above, and may be used in an engine of another type of vehicle. The straddle-type vehicle is not limited to a motorcycle, and may be any vehicle on which an engine is mounted. The straddle-type vehicle is not limited to a general vehicle in which a driver rides on a seat in a posture of straddling the seat, and includes a scooter-type vehicle in which a driver rides on a seat without straddling the seat.

[0061] As described above, according to a first aspect, a variable valve device (40) capable of changing a valve operation in an engine (20) is provided, and the variable valve device includes: a camshaft (41) on which a plurality of cams (44, 45) are provided adjacent to one another in a rotation axis direction; a plurality of rocker arms (the intake rocker arms 35a, 35b) in contact with the plurality of cams and configured to move a valve (the intake valve 31); a switching mechanism (50) configured to switch between coupling and separation of the plurality of rocker arms; and an oil pressure detector (96) configured to detect oil pressure in a specific oil passage (the measurement oil passage 79) of the engine, in which oil flows into the specific oil passage according to a switching operation of the switching mechanism. According to this configuration, the oil pressure of the specific oil passage changes according to the switching operation of the switching mechanism. A coupling state and a separation state of the plurality of rocker arms switched by the switching mechanism are accurately determined by detecting the change in the oil pressure of the specific oil passage by the oil pressure detector. This eliminates the need for an expensive non-contact sensor for detecting the switching operation, and the coupling state and the separation state of the plurality of rocker arms can be determined at low cost by using the oil pressure detector.

[0062] According to a second aspect, in the first aspect, the switching mechanism includes a coupling member (the hydraulic piston 53) and a separation member (the spring pin 54) that are formed in a manner in which when one of the coupling member and the separation member is moved forward, the other one is moved backward, the plurality of rocker arms are coupled by forward movement of the coupling member, the plurality of rocker arms are separated by forward movement of the separation member, and the oil flows into the specific oil passage by moving forward and backward the separation member. According to this configuration, a change in the oil pressure of the specific oil passage is interlocked with the forward movement and the backward movement of the separation member, and the coupling state and the separation state of the plurality of rocker arms are accurately determined according to a detection result of the oil pressure detector.

[0063] According to a third aspect, in the second aspect, the separation member has a cylindrical shape, an oil groove (77) for lubrication is formed on an outer circumferential surface of the separation member, and the specific oil passage and the oil groove communicate with each other when the separation member is moved forward and backward. According to this configuration, by using the oil groove for lubrication of the separation member, the oil flows into the specific oil passage without providing an extra oil passage in the engine.

[0064] According to a fourth aspect, in any one of the first to third aspects, the specific oil passage is open to the atmosphere in a state where the oil does not flow into the specific oil passage. According to this configuration, since the specific oil passage is open to the atmosphere, the oil pressure of the specific oil passage greatly drops, and a change in the oil pressure is clearly detected.

[0065] According to a fifth aspect, in any one of the first to fourth aspects, the specific oil passage is blocked from the atmosphere in a state where the oil flows into the specific oil passage. According to this configuration, since the specific oil passage is blocked from the atmosphere, the change in the oil pressure of the specific oil passage is clearly detected.

[0066] According to a sixth aspect, in any one of the first to fifth aspects, a movable portion of the switching mechanism is lubricated with the oil, and a part of the oil supplied for lubricating the switching mechanism flows into the specific oil passage. According to this configuration, the coupling state and the separation state of the rocker arms are determined using the oil used for lubricating the movable portion of the switching mechanism. Further, insufficient oil pressure of a lubrication circuit of the variable valve device is detected based on the magnitude of the oil pressure of the oil pressure detector.

[0067] According to a seventh aspect, in any one of the first to fifth aspects, the switching mechanism switches between coupling and separation of the plurality of rocker arms according to the oil pressure, and a part of oil supplied for actuating the switching mechanism flows into the specific oil passage. According to this configuration, since the switching operation of the switching mechanism and a change in the oil pressure of the specific oil passage are interlocked, the coupling state and the separation state of the plurality of rocker arms are accurately determined according to a detection result of the oil pressure detector.

[0068] Although the present embodiment has been described, a part or all of the embodiment and modifications described above may be combined as another embodiment.

[0069] The technique according to the present invention is not limited to the embodiment described above, and may be changed, replaced, or modified in various manners without departing from the gist of the technical concept. Further, the present invention may be implemented by other methods as long as the technical concept can be implemented by the methods through advance of the technique or other derivative techniques. Therefore, the claims cover all embodiments that may fall within the scope of the technical concept.REFERENCE SIGNS LIST

[0070] 20: engine 31: intake valve (valve) 35a, 35b: intake rocker arm (rocker arm) 40: variable valve device 41: camshaft 44: low-speed cam (cam) 45: high-speed cam (cam) 50: switching mechanism 53: hydraulic piston (coupling member) 54: spring pin (separation member) 77: oil groove of spring pin 79: measurement oil passage

Claims

1. A variable valve device (40) configured to change a valve operation in an engine (20), the variable valve device (40) comprising: a camshaft (41) on which a plurality of cams (44, 45) are provided adjacent to one another in a rotation axis direction; a plurality of rocker arms (35a, 35b) in contact with the plurality of cams (44, 45) and configured to move a valve (31); a switching mechanism (50) configured to switch between coupling and separation of the plurality of rocker arms (35a, 35b); and an oil pressure detector (96) configured to detect oil pressure in a specific oil passage (79) of the engine (20), wherein oil flows into the specific oil passage (79) according to a switching operation of the switching mechanism (50).

2. The variable valve device according to claim 1, wherein the switching mechanism includes a coupling member and a separation member that are formed in a manner in which when one of the coupling member and the separation member is moved forward, the other one is moved backward, the plurality of rocker arms are coupled by forward movement of the coupling member, the plurality of rocker arms are separated by forward movement of the separation member, and the oil flows into the specific oil passage by moving forward and backward the separation member.

3. The variable valve device according to claim 2, wherein the separation member has a cylindrical shape, an oil groove for lubrication is formed on an outer circumferential surface of the separation member, and the specific oil passage and the oil groove communicate with each other when the separation member is moved forward and backward.

4. The variable valve device according to claim 1 or 2, wherein the specific oil passage is open to the atmosphere in a state where the oil does not flow into the specific oil passage.

5. The variable valve device according to claim 1 or 2, wherein the specific oil passage is blocked from the atmosphere in a state where the oil flows into the specific oil passage.

6. The variable valve device according to claim 1 or 2, wherein a movable portion of the switching mechanism is lubricated with the oil, and a part of the oil supplied for lubricating the switching mechanism flows into the specific oil passage.

7. The variable valve device according to claim 1 or 2, wherein the switching mechanism switches between coupling and separation of the plurality of rocker arms according to the oil pressure, and a part of oil supplied for actuating the switching mechanism flows into the specific oil passage.

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