Patent ID: 12221910

DETAILED DESCRIPTION OF EMBODIMENTS

A variable valve device of one aspect of the present invention changes valve operations of an intake valve and an exhaust valve in a cylinder head. A pair of cam housings are separated in a predetermined direction in the cylinder head, and a rocker shaft is supported by opposing portions of the pair of cam housings. A plurality of rocker arms are swingably supported by the rocker shaft, a connecting pin is disposed in a pin hole of a rocker arm closer to one side in a predetermined direction, and a return pin is disposed in a pin hole of a rocker arm closer to the other side in the predetermined direction. When the return pin is pushed to the other side via the connecting pin by a pressing member, the connecting pin partially enters from the pin hole of the rocker arm closer to one side into the pin hole of the rocker arm closer to the other side, so that the plurality of rocker arms are connected. When the connecting pin is pushed back to one side via the return pin by a repulsive member, the connecting pin is pulled out from the pin hole of the rocker arm closer to the other side, so that the connection of the plurality of rocker arms is released. In this way, a connected state and a released state of the plurality of rocker arms can be switched with a simple configuration. In addition, an upper housing is supported at both ends by upper surfaces of the pair of cam housings. In the upper housing, the pressing member is disposed in a first accommodation hole on one side with respect to the rocker arm closer to one side, and the repulsive member is disposed in a second accommodation hole on the other side with respect to the rocker arm closer to the other side. Since the first accommodation hole and the second accommodation hole are formed in the upper housing, a parallelism between components is easily achieved, and wear due to partial contact between the components is prevented.

Embodiments

Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings.FIG.1is a left side view of an engine and a vehicle body frame according to the present embodiment.FIG.2is a perspective view of an inside of a cylinder head according to the present embodiment.FIG.3is a perspective view of 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 addition, in the following description, a center side in a left-right direction of the cylinder head is referred to as one side, and an outer side in the left-right direction of the cylinder head is referred to as the other side.

As shown inFIG.1, a straddle-type vehicle is formed by mounting various components such as an engine20and an electrical system on a cradle-type vehicle body frame10. The vehicle body frame10includes a main tube12that extends rearward from an upper portion of a head pipe11and then bends downward, and a down tube13that extends downward from a lower portion of the head pipe11and then bends rearward. A rear end portion of the down tube13is joined to a lower end portion of the main tube12to form an installation space for the engine20inside the vehicle body frame10. A rear side of the engine20is supported by the main tube12, and a front side and a lower side of the engine20are supported by the down tube13.

The engine20is a parallel two-cylinder engine, and includes a crankcase21, a cylinder22provided on the crankcase21, a cylinder head23provided on the cylinder22, and a cylinder head cover24provided on the cylinder head23. A magnet cover25that covers a magnet (not shown) from a lateral side is attached to a left side surface of the crankcase21. A sprocket cover26that covers a drive sprocket (not shown) from a lateral side is attached to the rear of the magnet cover25. A clutch cover (not shown) that covers a clutch (not shown) from a lateral side is attached to a right side surface of the crankcase21.

A radiator15that radiates heat of cooling water of the engine20is disposed in front of the engine20. An oil control valve16that controls a hydraulic pressure to variable valve devices40is disposed on an outer surface of the cylinder head cover24. An oil is supplied to the oil control valve16from a main gallery of the crankcase21through an external pipe17. A valve chamber is formed inside the cylinder head23and the cylinder head cover24. The variable valve device40(seeFIG.3) that changes valve operations of intake valves33(seeFIG.3) and exhaust valves34(seeFIG.3) by the hydraulic pressure is mounted on the valve chamber.

As shown inFIG.2, the engine20is a four-valve two-cylinder engine, and a cam chain31is disposed between two cylinders. The cam chain31is wound around a cam sprocket32, and the variable valve device40is disposed for each of the left and right cylinders with the cam sprocket32interposed therebetween. The variable valve device40is provided with a camshaft41that rotates integrally with the cam sprocket32. In the cylinder head23, cam housings42aand42bare separated in a left-right direction (a predetermined direction) for each cylinder, and the camshaft41is rotatably supported by mating surfaces of the cam housings42aand42band the cylinder head23.

In the cylinder head23, four intake valves33(seeFIG.3) are arranged behind the camshaft41, and four exhaust valves34are arranged in front of the camshaft41. The intake valve33is pressed in a valve-closing direction by a valve spring35(seeFIG.3), and the exhaust valve34is pressed in a valve-closing direction by a valve spring36. A low-speed cam43, a high-speed cam44, and an exhaust cam45(all of which are shown inFIG.3) are formed on an outer circumferential surface of the camshaft41. Each of the cams43to45is formed in a plate-like shape with a cam ridge protruding from a part of a base circle. The cam ridge of the high-speed cam44is higher than that of the low-speed cam43so that a valve lift amount of the high-speed cam44is larger than that of the low-speed cam43.

A rocker shaft46on an intake side and a rocker shaft47on an exhaust side are supported by opposing portions of the cam housings42aand42b. The rocker shaft46on the intake side and the rocker shaft47on the exhaust side are located above the camshaft41, and the rocker shaft46on the intake side and the rocker shaft47on the exhaust side extend parallel to the camshaft41. In addition, left and right side walls of the cylinder head23are recessed in a concave shape, and a pair of plug covers18are arranged in recesses of the cylinder head23. The oil control valve16that supplies the oil to the variable valve device40is disposed behind the cylinder head23.

As shown inFIGS.2and3, two types of rocker arms51aand51b(only one of each is shown inFIG.3) are swingably supported by the rocker shaft46on the intake side, and a rocker arm52(only one is shown inFIG.3) is swingably supported by the rocker shaft47on the exhaust side. The rocker arm51aon the intake side and the rocker arm52on the exhaust side are formed in a seesaw shape having a force point and an action point, and the rocker arm51bon the intake side serves as a force point of the rocker arm51a. Both a left end of the rocker arm51aon the intake side and a right end of the rocker arm52on the exhaust side are bifurcated.

A roller53athat is in rolling contact with the low-speed cam43is rotatably supported at one end of the rocker arm51aon the intake side, and a pair of intake valves33are connected to the other end of the rocker arm51awhich is bifurcated. A roller53bthat is in rolling contact with the high-speed cam44is rotatably supported at one end of the rocker arm51bon the intake side, and the intake valve33is not connected to the other end of the rocker arm51b. A roller54that is in rolling contact with the exhaust cam45is rotatably supported at one end of the rocker arm52on the exhaust side, and a pair of exhaust valves34are connected to the other end of the rocker arm52which is bifurcated. The rocker arms51aand51bare formed in a connectable manner.

When the engine rotates at a low speed and a medium speed, the rocker arms51aand51bare not connected. Therefore, the rocker arm51ais swung by the low-speed cam43, and the rocker arm51bis swung by the high-speed cam44. Since the pair of intake valves33are connected to the rocker arm51a, the pair of intake valves33are moved according to rotation of the low-speed cam43. Since the cam ridge of the low-speed cam43is low, valve lift amounts of the pair of intake valves33are low. Since the intake valve33is not connected to the rocker arm51b, the rocker arm51bis idle according to rotation of the high-speed cam44.

When the engine rotates at a high speed, the rocker arms51aand51bare connected. Therefore, the rocker arms51aand51bare swung integrally by the high-speed cam44. Since the pair of intake valves33are connected to the rocker arm51bvia the rocker arm51a, the pair of intake valves33are moved according to the rotation of the high-speed cam44. Since the cam ridge of the high-speed cam44is high, the valve lift amounts of the pair of intake valves33are high. In this way, by switching a connected state of the rocker arms51aand51b, the low-speed cam43and the high-speed cam44for moving the intake valves33are switched.

Each of the variable valve devices40is provided with a switching mechanism that switches between the connected state and a non-connected state of the rocker arms51aand51baccording to the hydraulic pressure. A connecting pin61is disposed in a pin hole of the rocker arm51bcloser to one side (closer to a center) in a left-right direction (a predetermined direction) of the cylinder head23, and a return pin62is disposed in a pin hole of the rocker arm51acloser to the other side (closer to an outer side) in the left-right direction of the cylinder head23. A hydraulic piston (a pressing member)63is disposed on one side with respect to the rocker arm51b, and a spring pin (a repulsive member)64with a spring is disposed on the other side with respect to the rocker arm51a.

The hydraulic piston63causes the connecting pin61to push the return pin62to the other side, and the spring pin64causes the return pin62to push back the connecting pin61to one side. By pushing the connecting pin61by the hydraulic piston63, a part of the connecting pin61enters the pin hole of the rocker arm51afrom the pin hole of the rocker arm51b, so that the rocker arms51aand51bare connected. By pushing back the connecting pin61by the spring pin64via the return pin62, the part of the connecting pin61is pulled out from the pin hole of the rocker arm51a, so that the connection of the rocker arms51aand51bis released.

The hydraulic piston63and the spring pin64are separated greatly in a left-right direction. In a case where the hydraulic piston63and the spring pin64are arranged as separate members, it is difficult to achieve a parallelism between the hydraulic piston63and the spring pin64, and there is a possibility that components are worn due to partial contact. Therefore, in the variable valve device40according to the present embodiment, an upper housing70is supported at both ends by upper surfaces of the cam housings42aand42b, and the hydraulic piston63and the spring pin64are arranged on the upper housing70. By arranging the hydraulic piston63and the spring pin64as the same member, the parallelism between the hydraulic piston63and the spring pin64is ensured.

When an oil is continuously injected from the camshaft41to lubricate the rocker arms51a,51b, and52by droplets of the oil, there is a possibility that an operating rotation speed of the variable valve device40cannot be obtained due to a decrease in a hydraulic pressure of the engine20. Further, adhesion of the oil to the cam increases a mechanical loss, and there is a possibility that important components are worn due to insufficient lubrication. Therefore, the upper housing70according to the present embodiment is formed in a ladder shape, and a lubricating oil is supplied from a bridge portion of the upper housing70along the rocker shafts46and47and the camshaft41to required locations of valve components.

Hereinafter, oil passages for lubrication and operation will be described with reference toFIGS.4A to13.FIGS.4A and4Bshow a top view and a bottom view of the upper housing according to the present embodiment.FIG.5is a top view of the inside of the cylinder head according to the present embodiment.FIG.6is a cross-sectional view of the cylinder head inFIG.5taken along a line A-A.FIG.7is a cross-sectional view of the cylinder head inFIG.6taken along a line B-B.FIG.8is a cross-sectional view of the cylinder head inFIG.5taken along a line C-C.FIG.9is a cross-sectional view of the cylinder head inFIG.5taken along a line D-D.FIG.10is a cross-sectional view of the cylinder head inFIG.5taken along a line E-E.FIG.11is a cross-sectional view of the cylinder head inFIG.5taken along a line F-F.FIG.12is a cross-sectional view of the cylinder head inFIG.5taken along a line G-G.FIG.13is a schematic diagram of an operating passage and a short-cut passage according to the embodiment.

As shown inFIGS.4A and4B, the upper housing70is formed in the ladder shape by housing fixing portions71aand71bextending in a front-rear direction and first to third bridge portions72to74extending in a left-right direction. The housing fixing portions71aand71bare fixed to the cam housings42aand42b, respectively (seeFIG.2). The first bridge portion72connects the housing fixing portions71aand71bon the intake side of the cylinder head23. The second bridge portion73connects the housing fixing portions71aand71bbetween the intake side and the exhaust side of the cylinder head23. The third bridge portion74connects the housing fixing portions71aand71bon the exhaust side of the cylinder head23.

Attachment holes75aand75bare formed in each of the housing fixing portions71aand71b. The housing fixing portions71aand71bare respectively fixed to the cam housings42aand42bbetween the first bridge portion72and the second bridge portion73by the attachment holes75a. The housing fixing portions71aand71bare respectively fixed to the cam housings42aand42bat both ends of the third bridge portion74by the attachment holes75b. Bolt tightening locations are secured between the first and second bridge portions72and73, and bolt tightening locations are secured at both ends of the third bridge portion74, so that the upper housing70can be fixed to the cam housings42aand42bwithout increasing a size of the upper housing70.

The first bridge portion72extends along the rocker shaft46on the intake side (seeFIG.3), and a lubricating passage76k(seeFIG.9) through which the lubricating oil passes is formed in the first bridge portion72. A plurality of supply holes77care formed in a lower surface of the first bridge portion72, and the plurality of supply holes77care located above contact locations between components. A pair of nozzles78protrude from the first bridge portion72to the intake side, and supply holes77dat tips of the pair of nozzles78are located above the pair of intake valves33(seeFIG.10). The first bridge portion72is connected to the housing fixing portions71aand71bvia connecting portions81aand81b.

A hydraulic chamber (a first accommodation hole)82(seeFIGS.14A and14B) is formed in the connecting portion81awhich is a connecting location between the first bridge portion72and the housing fixing portion71a. An accommodation hole (a second accommodation hole)83(seeFIGS.14A and14B) is formed in the connecting portion81bwhich is a connecting location between the first bridge portion72and the housing fixing portion71b. The hydraulic piston63(seeFIG.9) serving as a hydraulic piston is disposed in the hydraulic chamber82, and the spring pin64(seeFIG.9) is disposed in the accommodation hole83. The hydraulic chamber82and the accommodation hole83are formed coaxially, and the parallelism between the hydraulic piston63and the spring pin64is ensured. An operating oil is supplied to the hydraulic chamber82through a hydraulic circuit different from that for the lubricating oil.

The second bridge portion73extends along the camshaft41(seeFIG.3), and a lubricating passage76n(seeFIG.12) is formed in the second bridge portion73. A plurality of supply holes77eare formed in a lower surface of the second bridge portion73, and the plurality of supply holes77eare located above the rocker arms51a,51b, and52. The third bridge portion74extends along the exhaust rocker shaft47on the exhaust side (seeFIG.3). A pair of nozzles79protrude from the third bridge portion74to the exhaust side, and supply holes77f(seeFIG.10) at tips of the pair of nozzles79are located above the pair of exhaust valves34(seeFIG.10).

An oil hole84is formed on the intake side of the housing fixing portion71a, and an operating oil is supplied from the oil control valve16to the oil hole84. An oil groove is formed in a lower surface of the housing fixing portion71a, and an operating passage (an oil passage)85and a short-cut passage (an oil passage)86through which the operating oil passes are formed by fixing the housing fixing portion71ato the cam housing42a. The operating passage85and the short-cut passage86communicate with the hydraulic chamber82(seeFIGS.14A and14B) in which the hydraulic piston63is disposed, and the operating oil is supplied from the oil control valve16to the hydraulic chamber82through the operating passage85and the short-cut passage86.

An oil groove is formed in a center of the housing fixing portion71a, and a lubricating passage76lis formed by fixing the housing fixing portion71ato the cam housing42a. The lubricating oil enters the lubricating passage76lfrom a camshaft41side and is delivered to the second bridge portion73. An oil groove is formed in a lower surface of the housing fixing portion71b, and a lubricating passage76iis formed by fixing the housing fixing portion71bto the cam housing42b. The lubricating oil enters the lubricating passage76ifrom the camshaft41side and is delivered to the first bridge portion72. In this way, hydraulic circuits for the lubricating oil and the operating oil are formed in the upper housing70.

As shown inFIGS.5to7, the cylinder head23is fixed to the crankcase21via the cylinder22by using a plurality of head bolts27. A gap between the head bolt27on the exhaust side and a bolt hole forms a lubricating passage76a, and a lubricating passage76bextends obliquely from the lubricating passage76ato the camshaft41. The lubricating oil is guided from the crankcase21to the periphery of the camshaft41through the lubricating passages76aand76b, and the lubricating oil is guided from the periphery of the camshaft41to a lubricating passage76cin the camshaft41. Although the description is omitted, the lubricating oil in the lubricating passage76cis used to lubricate peripheral components of the camshaft41.

The housing fixing portion71aon one side (a center side in the left-right direction) is fixed to the cylinder head23via the cam housing42aby using a pair of housing bolts28. Gaps between the pair of housing bolts28and bolt holes form lubricating passages76dand76eextending from the periphery of the camshaft41to the rocker shafts46and47, respectively. The lubricating oil is guided to lubricating passages76fand76gin the rocker shafts46and47through the lubricating passages76dand76e, respectively. The lubricating oil is supplied from a supply hole77aof the rocker shaft46to the rocker arms51aand51bon the intake side, and the lubricating oil is supplied from a supply hole77bof the rocker shaft47to the rocker arm52on the exhaust side.

As shown inFIG.8, the housing fixing portion71bon the other side (an outer side in the left-right direction) is fixed to the cylinder head23via the cam housing42bby using a pair of housing bolts28. A gap between the housing bolt28on the intake side and a bolt hole forms a lubricating passage76hextending from the other end of the lubricating passage76fof the rocker shaft46to the housing fixing portion71b. A lubricating passage76jextends obliquely from the lubricating passage76ion a mating surface between the housing fixing portion71band the cam housing42bto the first bridge portion72. The lubricating oil is guided from one end to the other end of the lubricating passage76f, and the lubricating oil is guided to the lubricating passage76kin the first bridge portion72through the lubricating passages76hto76j.

As shown inFIGS.9and10, the lubricating oil is supplied from the plurality of supply holes77cof the first bridge portion72to contact locations of the hydraulic piston63, the connecting pin61, the return pin62, and the spring pin64. Contact locations between pin components are lubricated to prevent wear. The pair of nozzles78protrude from the first bridge portion72to the intake side, and the supply holes77dof the pair of nozzles78face an inner wall surface of the cylinder head cover24. The lubricating oil is blown against the inner wall surface of the cylinder head cover24from the supply holes77dof the pair of nozzles78, and the lubricating oil is supplied to stem ends of the pair of intake valves33along the inner wall surface of the cylinder head cover24.

As shown inFIGS.11and12, a lubricating passage76mextends obliquely from the lubricating passage76lon a mating surface between the housing fixing portion71aand the cam housing42ato the second bridge portion73. The oil is guided from the periphery of the camshaft41to the housing fixing portion71athrough the lubricating passage76e, and the lubricating oil is guided to the lubricating passage76nin the second bridge portion73through the lubricating passages76land76m. The lubricating oil is supplied from the plurality of supply holes77eof the second bridge portion73to the rollers53a,53b, and54of the rocker arms51a,51b, and52. The rocker arms51a,51b, and52are smoothly moved, and the pin components can be appropriately brought into contact with each other.

As shown inFIG.8, the housing fixing portion71bis fixed to the cylinder head23via the cam housing42bby using the pair of housing bolts28. A gap between the housing bolt28on the exhaust side and a bolt hole forms a lubricating passage76oextending from the other end of the lubricating passage76gof the rocker shaft46to the housing fixing portion71b. The lubricating oil is guided from one end to the other end of the lubricating passage76g, and the lubricating oil is guided to a lubricating passage76rin the pair of nozzles79of the third bridge portion74through the lubricating passage76o.

As shown inFIG.10, the pair of nozzles79protrude from the third bridge portion74to the exhaust side, and the supply holes77fof the pair of nozzles79face a rib29of the cylinder head cover24. The rib29of the cylinder head cover24is located above the pair of exhaust valves34. The lubricating oil is blown against the rib29of the cylinder head cover24from the supply holes77fof the pair of nozzles79, and the lubricating oil is supplied to stem ends of the pair of exhaust valves34along the rib29of the cylinder head cover24. In this way, hydraulic circuits for lubricating the valve components of the variable valve device40are formed in the upper housing70.

As shown inFIG.13, in the housing fixing portion71a(seeFIGS.4A and4B), an upstream passage87aof the operating passage85extends from the oil control valve16toward the camshaft41, and a downstream passage87bof the operating passage85extends from the camshaft41toward the hydraulic piston63. A downstream end of the upstream passage87aand an upstream end of the downstream passage87bare positioned on the same circumference on the outer circumferential surface of the camshaft41. An oil groove89is formed in a circumferential direction on a circumference of the outer circumferential surface of the camshaft41. The oil groove89functions as an operating passage for supplying the operating oil to the hydraulic piston63together with the upstream passage87aand the downstream passage87b.

The oil is supplied from the oil control valve16to the hydraulic piston63only while the upstream passage87aand the downstream passage87bcommunicate with each other via the oil groove89. At this time, the oil groove89is formed such that the upstream passage87aand the downstream passage87bcommunicate with each other at an end timing of valve lift, and the upstream passage87aand the downstream passage87bare separated before the start of the valve lift. That is, the oil groove89is formed such that the oil starts to be supplied from the oil control valve16to the hydraulic piston63at the end timing of the valve lift, and the supply of the oil to the hydraulic piston63ends before the start of the valve lift.

Since the oil starts to be supplied to the hydraulic piston63at the end timing of the valve lift, a connecting operation of the rocker arms51aand51bis not hindered by the valve lift. In addition, since the connecting operation of the rocker arms51aand51bends before the valve lift starts, the rocker arms51aand51bare not connected during the valve lift. Accordingly, as the camshaft41rotates, the oil is intermittently supplied from the oil control valve16to the hydraulic piston63through the operating passage85, and the rocker arms51aand51bcan be smoothly connected via the connecting pin61.

The short-cut passage86extends directly from the oil control valve16to the hydraulic piston63. The short-cut passage86is formed shorter than the operating passage85. A stepwise oil supply structure with respect to the hydraulic piston63is formed such that the oil is supplied from the short-cut passage86to the hydraulic piston63after the oil is supplied from the operating passage85to the hydraulic piston63. Although the intermittent supply of the oil from the operating passage85alone may cause the hydraulic piston63to move, the hydraulic piston63is stably maintained by directly supplying the oil from the short-cut passage86.

A connecting operation of the variable valve device will be described with reference toFIGS.14A and14B.FIGS.14A and14Bshow explanatory views of the connecting operation of the variable valve device according to the present embodiment. InFIGS.14A and14B, for convenience of description, reference signs inFIG.13are used as appropriate.

As shown inFIG.14A, in the upper housing70, the hydraulic chamber82is formed in the connecting portion81aon one side with respect to the rocker arm51b, and the accommodation hole83is formed in the connecting portion81bon the other side with respect to the rocker arm51a. The hydraulic piston63is disposed in the hydraulic chamber82, and the spring pin64is disposed in the accommodation hole83. The hydraulic piston63is in contact with the connecting pin61in the rocker arm51b, and the spring pin64is in contact with the return pin62in the rocker arm51a. Center lines of the hydraulic piston63and the spring pin64coincide with each other, and wear due to partial contact between components is prevented.

When the engine rotates at a low speed, the oil is not supplied from the oil control valve16to the hydraulic chamber82. No pressing force is applied from the hydraulic piston63to the connecting pin61, and a spring force of the spring pin64is applied to the return pin62. The return pin62abuts against the rocker arm51a, and the return pin62is positioned at an initial position. At this time, the other end65of the connecting pin61is in contact with one end66of the return pin62at a non-connecting position P1in a gap between the rocker arms51aand51b. The other end65of the connecting pin61is located outside the rocker arm51b, and the rocker arms51aand51bare separated from each other.

As shown inFIG.14B, when an engine speed is increased to a predetermined speed or more, the oil starts to be supplied from the oil control valve16to the hydraulic chamber82. As the camshaft41rotates, the upstream passage87aand the downstream passage87bof the operating passage85intermittently communicate with each other through the oil groove89, and the oil is intermittently supplied from the operating passage85to the hydraulic piston63. At this time, the oil starts to be supplied at the end timing of the valve lift of the intake valve33so as not to hinder the connecting operation of the rocker arms51aand51b. Therefore, the hydraulic piston63is smoothly pushed out in an advancing direction with the oil from the operating passage85.

The connecting pin61is pushed in by the hydraulic piston63, and the spring pin64is moved to the other side via the return pin62by the connecting pin61. The other end65of the connecting pin61is moved to the other side from the non-connecting position P1to a connecting position P2in the rocker arm51a. When a part of the connecting pin61enters a pin hole55aof the rocker arm51a, the rocker arms51aand51bare connected via the connecting pin61. A downstream end of the short-cut passage86is opened by the movement of the hydraulic piston63, and a position of the hydraulic piston63is maintained by continuous oil supply from the short-cut passage86.

As shown inFIG.14A, when the engine speed falls below the predetermined speed, the oil is returned from the hydraulic piston63to the oil control valve16. The pushing of the connecting pin61by the hydraulic piston63is released, the return pin62is pushed back by a repulsive force of the spring pin64, and the connecting pin61is pushed back to the one side by the return pin62. The other end65of the connecting pin61is moved to the one side from the connecting position P2to the non-connecting position P1. When the part of the connecting pin61is pulled out from the pin hole55aof the rocker arm51a, the connection of the rocker arms51aand51bis released.

As described above, according to the variable valve device40of the present embodiment, when the return pin62is pushed to the other side via the connecting pin61by the hydraulic piston63, the connecting pin61partially enters the pin hole of the rocker arm51afrom the pin hole of the rocker arm51b, so that the rocker arms51aand51bare connected. When the connecting pin61is pushed back to the one side via the return pin62by the spring pin64, the connecting pin61is pulled out from the pin hole of the rocker arm51a, so that the connection of the rocker arms51aand51bis released. In this way, the connected state and a released state of the rocker arms51aand51bcan be switched with a simple configuration. In addition, since the hydraulic chamber82and the accommodation hole83are formed in the upper housing70, a parallelism between the components is easily achieved, and the wear due to the partial contact between the components is prevented.

In the present embodiment, the pair of rocker arms are provided on the intake side of the variable valve device, but a plurality of rocker arms may be provided on the intake side of the variable valve device. For example, three or more rocker arms may be provided on the intake side of the variable valve device.

In the present embodiment, the hydraulic piston is shown as an example of the pressing member, but the pressing member may be a member that causes the connecting pin to push the return pin to the other side.

In the present embodiment, the spring pin is shown as an example of the repulsive member, but the repulsive member may be a member that causes the return pin to push back the connecting pin to the one side.

In the present embodiment, the upper housing includes the first to third bridge portions, but the upper housing may be formed in a manner of being supported at both ends by the upper surfaces of the pair of cam housings.

In the present embodiment, the hydraulic chamber (the first accommodation hole) is formed in the connecting portion on the one side of the upper housing, but the hydraulic chamber may be formed on one side with respect to a rocker arm closer to one side in the upper housing. Similarly, the accommodation hole (the second accommodation hole) is formed in the connecting portion on the other side of the upper housing, but the accommodation hole may be formed on the other side with respect to a rocker arm closer to the other side in the upper housing.

In the present embodiment, a flange pin is used for the connecting pin and the return pin, but a straight pin may be used for the connecting pin and the return pin.

In the present embodiment, the seesaw-type rocker arm is shown as an example, but a type of the rocker arm is not particularly limited, and the rocker arm may be of a finger follower type.

In the present embodiment, the plurality of rocker arms are adjacent to each other, but the plurality of rocker arms may be separated from each other.

In the present embodiment, the operating passage and the short-cut passage are formed in the upper housing, but an oil passage capable of supplying the operating oil to the hydraulic piston may be formed in the cylinder head.

An exhaust device according to the present embodiment is not limited to the engine of the straddle-type vehicle described above, and may be adopted for an engine of another 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 general vehicles on which a driver rides in a posture of straddling a seat, and includes a scooter-type vehicle on which the driver rides without straddling the seat.

As described above, a first aspect relates to a variable valve device (40) capable of changing valve operations of an intake valve (33) and an exhaust valve (34) in a cylinder head (23), the variable valve device including: a pair of cam housings (42a,42b) separated in a predetermined direction in the cylinder head; a rocker shaft (46) supported by opposing portions of the pair of cam housings; a plurality of rocker arms (51a,51b) swingably supported by the rocker shaft; a connecting pin (61) disposed in a pin hole of a rocker arm closer to one side in a predetermined direction; a return pin (62) disposed in a pin hole of a rocker arm closer to the other side in the predetermined direction; a pressing member (the hydraulic piston63) configured to cause the connecting pin to push the return pin to the other side; a repulsive member (the spring pin64) configured to cause the return pin to push back the connecting pin to one side; and an upper housing (70) supported at both ends by upper surfaces of the pair of cam housings, in which the upper housing is formed with a first accommodation hole (the hydraulic chamber82) in which the pressing member is disposed on one side with respect to the rocker arm closer to one side, and a second accommodation hole (the accommodation hole83) in which the repulsive member is disposed on the other side with respect to the rocker arm closer to the other side. According to 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 from the pin hole of the rocker arm closer to one side into the pin hole of the rocker arm closer to the other side, so that the plurality of rocker arms are connected. When the connecting pin is pushed back to the one side via the return pin by the repulsive member, the connecting pin is pulled out from the pin hole of the rocker arm closer to the other side, so that the connection of the plurality of rocker arms is released. In this way, a connected state and a released state of the plurality of rocker arms can be switched with a simple configuration. In addition, since the first accommodation hole and the second accommodation hole are formed in the upper housing, a parallelism between components is easily achieved, and wear due to partial contact between the components is prevented.

In a second aspect according to the first aspect, the upper housing includes a pair of housing fixing portions (71a,71b) fixed to the pair of cam housings, and a first bridge portion (72) that is located on an intake side of the cylinder head and connects the pair of housing fixing portions, and the first accommodation hole is formed in a connecting location (the connecting portion81a) between one housing fixing portion and the first bridge portion, and the second accommodation hole is formed in a connecting location (the connecting portion81b) between the other housing fixing portion and the first bridge portion. According to this configuration, a rigidity around the first accommodation hole and the second accommodation hole is increased, and a parallelism between the first accommodation hole and the second accommodation hole is easily achieved.

In a third aspect according to the second aspect, the first bridge portion is formed with a plurality of supply holes (77c) configured to allow a lubricating oil to be supplied to contact locations of the connecting pin, the return pin, the pressing member, and the repulsive member. According to this configuration, the contact locations of the connecting pin, the return pin, the pressing member, and the repulsive member can be lubricated to prevent the wear.

In a fourth aspect according to the second aspect or the third aspect, the first bridge portion is formed with a supply hole (77d) configured to allow a lubricating oil to be supplied to a stem end of the intake valve. According to this configuration, the stem end of the intake valve can be lubricated.

In a fifth aspect according to any one of the second aspect to the fourth aspect, the upper housing includes a second bridge portion (73) that is located between the intake side and an exhaust side of the cylinder head and connects the pair of housing fixing portions, and the pair of housing fixing portions are fixed to the pair of cam housings between the first bridge portion and the second bridge portion. According to this configuration, a rigidity of the upper housing can be increased by the second bridge portion. In addition, it is possible to secure bolt tightening locations between the first and second bridge portions and fix the upper housing to the cam housings without increasing a size of the upper housing.

In a sixth aspect according to the fifth aspect, the second bridge portion is formed with a plurality of supply holes (77e) configured to allow a lubricating oil to be supplied to the plurality of rocker arms. According to this configuration, the rocker arms can be lubricated. Since the rocker arms are smoothly moved, pin components can be appropriately brought into contact with each other.

In a seventh aspect according to any one of the second aspect to the sixth aspect, the upper housing includes a third bridge portion (74) that is located on an exhaust side of the cylinder head and connects the pair of housing fixing portions, and the pair of housing fixing portions are fixed to the pair of cam housings at both ends of the third bridge portion. According to this configuration, the rigidity of the upper housing can be increased by the third bridge portion. In addition, it is possible to secure bolt tightening locations at both ends of the third bridge portion and fix the upper housing to the cam housings without increasing the size of the upper housing.

In an eighth aspect according to the seventh aspect, the third bridge portion is formed with a supply hole (77f) configured to allow a lubricating oil to be supplied to a stem end of the exhaust valve. According to this configuration, the stem end of the exhaust valve can be lubricated.

In a ninth aspect according to any one of the second aspect to the eighth aspect, the pressing member is a hydraulic piston configured to be operated with a hydraulic pressure, and a mating surface of the pair of cam housings and the pair of housing fixing portions is formed with an oil passage (the operating passage85, the short-cut passage86) configured to allow an operating oil to be supplied to the hydraulic piston. According to this configuration, the oil passage can be formed in a compact manner using the mating surface of the pair of cam housings and the pair of housing fixing portions.

Although the present embodiment has been described, the above-described embodiment and modification may be combined entirely or partially as another embodiment.

The technique of the present invention is not limited to the above-described embodiment, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. The present invention may be implemented using other methods as long as the technical idea can be implemented by the methods through advance of the technique or other derivative techniques. Accordingly, the claims cover all embodiments that may be included within the scope of the technical idea.