1. Field of the Invention
The present invention relates to a valve gear for an engine that switches between a mode in which an intake valve or exhaust valve normally operates, and a mode in which the operation of the intake valve or exhaust valve stops.
2. Description of the Related Art
Conventionally, a technique for resting some cylinders while an engine is operating has been known as a technique to further improve fuel consumption. Resting some cylinders is often performed by assembling a switch into a valve gear that drives an intake valve or an exhaust valve.
A conventional switch of this kind is described in, e.g., Japanese Patent Laid-Open No. 2008-151115.
The switch described in Japanese Patent Laid-Open No. 2008-151115 has a structure which switches the support modes of a rocker arm that drives an intake valve or an exhaust valve. The support mode of the rocker arm is switched to a normal operation state support mode or a cylinder resting state support mode.
In the normal operation state, the switch converts the rotation of a cam shaft into a reciprocal motion by using the rocker arm, and transmits the reciprocal motion to the intake valve or the exhaust valve. On the other hand, in the cylinder resting state, the position of the swinging center of the rocker arm changes, i.e., the rocker arm swings around one end that is in contact with the intake valve or exhaust valve, against the spring force of a return spring which biases the other end of the rocker arm. That is, only the rocker arm swings with the intake valve or exhaust valve being closed.
The position of the swinging center of the rocker arm is changed by using a plurality of rocker shafts. The switch includes a first rocker shaft that functions as the rocker arm swinging center in the cylinder resting state, and a second rocker shaft that functions as the rocker arm swinging center in the normal operation state. The first and second rocker shafts are connected with each other by a connecting rod, and are integrated into one rocker shaft assembly. The rocker shaft assembly is able to move in the axial direction between the rocker arm and rocker arm support members provided on the two sides of the rocker arm. Also, the rocker shaft assembly is moved to one side or the other side in the axial direction during switching by being driven by an actuator.
The first and second rocker shafts are parallel and spaced apart from each other in a direction perpendicular to the axial direction, and divided into one side and the other side of the connecting rod in the axial direction. The first and second rocker shafts are provided in shaft holes of the rocker arm support members so as to be pivotal and movable in the axial direction. The connecting rod is accommodated in a groove in the rocker arm support member.
In the normal operation state, the rocker arm assembly moves toward the rocker arm support member. In this state, the first rocker shaft is detached from the rocker arm and accommodated together with the connecting rod in the rocker arm support member. The second rocker shaft pivotally fits into both the rocker arm support member and the rocker arm. In the normal operation state, therefore, the rocker arm swings around the second rocker shaft.
In the cylinder resting state, the second rocker shaft and the connecting rod extend out from the rocker arm support member, and the first rocker shaft pivotally fits into both the rocker arm support member and the rocker arm. In the cylinder resting state, therefore, the rocker arm swings around one end of the first rocker shaft that is in contact with the intake valve or exhaust valve.
The valve gear for an engine described in Japanese Patent Laid-Open No. 2008-151115 has a problem that the reliability of the operation of switching the rocker arm support modes is low. This problem occurs due to the following two reasons.
The first reason is that the structure of the rocker shaft that supports the rocker arm to be swingable is complicated. When the normal operation state support mode shifts to the cylinder resting state support mode, the second rocker shaft and the connecting rod must be detached from the rocker arm support member. On the other hand, when the cylinder resting state support mode shifts to the normal operation state support mode, the second rocker shaft and the connecting rod must be accommodated in the rocker arm support member. That is, a plurality of members must enter and leave the rocker arm support member when switching the support modes. Since switching easily fails, the reliability of the operation decreases.
The second reason is that the connecting rod is relatively thin. That is, the connecting rod may collide against the rocker arm support member and break when the support modes are switched. This decreases the reliability of the operation.
To reliably switch the rocker arm support modes, it may be possible to omit the first rocker shaft and the connecting rod of the above-described rocker shaft assembly and use only the second rocker shaft. In this case, the second rocker shaft is pulled out from the rocker arm and accommodated in the rocker arm support member in the cylinder resting state.
If this arrangement is used, however, the swinging center of the rocker arm moves from a correct position in the cylinder resting state so the second rocker shaft cannot fit into the shaft hole of the rocker arm support member when the cylinder resting state support mode shifts to the normal operation state support mode.
Preferred embodiments of the present invention provide a valve gear for an engine which smoothly changes between a normal operation state support mode and a cylinder resting state support mode, thus increasing the reliability of operation of the valve gear.
According to a preferred embodiment of the present invention, a valve gear for an engine includes a cam shaft including one of an intake valve driving cam and an exhaust valve driving cam and that is rotatably supported by a cylinder head, a pair of support walls in the cylinder head such that the pair of support walls are spaced apart and face each other in an axial direction of the cam shaft, and a rocker arm including a first end in contact with a valve stem of one of an intake valve and an exhaust valve and a second end inserted between the pair of support walls and supported on the support wall by a support, wherein the support switches a plurality of support modes and includes shaft holes in the pair of support walls and the second end of the rocker arm, the shaft holes extending parallel or substantially parallel to the cam shaft, a rocker shaft that movably fits into the shaft holes, tracks in the pair of support walls, the tracks each extending from the corresponding shaft hole in a direction opposite to the cam shaft, and a return spring that biases the rocker arm toward the cam, the plurality of support modes include a first support mode in which the rocker arm swings around the rocker shaft as a swinging center to convert a rotation of the cam into a reciprocal motion and transmit the reciprocal motion to one of the intake valve and the exhaust valve, and a second support mode in which the rocker arm swings along the track around a portion in contact with the valve stem of one of the intake valve and the exhaust valve, as a swinging center, to keep the one of the intake valve and the exhaust valve closed, and in the first support mode, the rocker shaft moves to a position where the support wall and the rocker arm are connected via the rocker shaft, and, in the second support mode, the rocker shaft moves to a position where a connection between the support walls and the rocker arm is canceled.
In a preferred embodiment of the present invention, the first support mode is used in the normal operation state, and the second support mode is used in the cylinder resting state. This support mode switching is performed by moving the rocker shaft in the axial direction. Since the valve gear for an engine according to preferred embodiments of the present invention uses a simple support structure, the reliability of switching the rocker arm support modes is higher than that of the conventional valve gear described in Japanese Patent Laid-Open No. 2008-151115.
The track determines the rocker arm moving path when the second support mode is used. That is, when the rocker arm swings to one end of the track, the shaft hole of the rocker arm and that of the support wall are positioned on the same axis. Consequently, the second support mode correctly shifts to the first support mode.
Accordingly, preferred embodiments of the present invention provide a valve gear for an engine which smoothly switches between the first support mode in the normal operation state and the second support mode in the cylinder resting state, thus increasing reliability of the operation of the valve gear.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.
A first preferred embodiment of a valve gear for an engine will be explained in detail below with reference to
In a valve gear 1 for an engine shown in
The intake cam shaft 3 and the exhaust cam shaft 4 rotate when the rotation of a crank shaft (not shown) is transmitted via a transmission. The intake cam shaft 3 includes an intake cam shaft main body 16 rotatably supported by a journal member 15 of the cylinder head 2, and an intake valve driving cam 17 in the intake cam shaft main body 16. The exhaust cam shaft 4 includes an exhaust cam shaft main body 18 rotatably supported by the journal member 15 described above, and an exhaust valve driving cam 19 in the exhaust cam shaft main body 18.
The intake valve driving cam 17 is provided for each intake valve 5, and the exhaust valve driving cam 19 is provided for each exhaust valve 6. The cams 17 and 19 respectively include base circular portions 17a and 19a and apexes 17b and 19b.
Two intake valves 5 and two exhaust valves 6 are provided for one cylinder, for example. The two intake valves 5 are arranged with a predetermined spacing in the axial direction of the intake cam shaft 3. The two exhaust valves 6 are arranged with a predetermined spacing in the axial direction of the exhaust cam shaft 4.
The intake valve 5 includes a valve body 5a that opens/closes an intake port 21 of the cylinder head 2, and a valve stem 5b extending from the valve body 5a into a valve gear chamber 22 of the cylinder head 2. The exhaust valve 6 includes a valve body 6a that opens/closes an exhaust port 23 of the cylinder head 2, and a valve stem 6b extending from the valve body 6a into the valve gear chamber 22 of the cylinder head 2. Valve springs 24 that bias the intake valve 5 and exhaust valve 6 in a closing direction are provided between the distal ends of the valve stems 5b and 6b and the cylinder head 2. Also, cap-shaped shims 25 are provided on the distal ends of the valve stems 5b and 6b.
The upstream end of the intake port 21 opens to one side of the cylinder head 2, and the downstream end thereof opens in a combustion chamber 26. The upstream end of the exhaust port 23 opens to the combustion chamber 26, and the downstream end thereof opens to the other side of the cylinder head 2. A spark plug 27 is provided in a central portion of the combustion chamber 26.
The journal member 15 has a function of supporting the intake cam shaft main body 16 and the exhaust cam shaft main body 18 described above, and a function of supporting the rocker arms 7 to 10 to be described below.
As shown in
With the cam shaft main bodies 16 and 18 being sandwiched between the journal member 15 and cam caps 30, the cam caps 30 are fixed to the journals 28 and 29 by first fixing bolts 31 and second fixing bolts 32, for example (see
As shown in
As shown in
The first support walls 34 on the intake valve side and the first support walls 35 on the exhaust valve side are integrated with the journal member 15. Also, the first support walls 34 and 35 are provided on the two sides of the journal member 15. The two sides are sides in the axial direction of the intake cam shaft 3 or the exhaust cam shaft 4. Accordingly, the support members 36 are provided on the two sides of the journal member 15. The support members 36 are separated from the journal member 15 and mounted on the journal member 15 by mounting bolts 37, for example.
As shown in
The first shaft holes 41 are positioned between valve stem distal ends 5c and 6c of the intake valve 5 and the exhaust valve 6 and the cam shafts 3 and 4 in the cylinder axial direction (the vertical direction in
The first shaft holes 41 according to this preferred embodiment include through holes 43 in the first support walls 34 and 35, and hollow portions of first cylindrical bodies 44 in the openings at the two ends of each through hole 43. The through holes 43 are connected to first hydraulic oil passages 45 (see
The first cylindrical bodies 44 are fitted into and held by the openings of the through holes 43.
As shown in
The width of the first groove 42 is the same as or slightly larger than the outer diameter of the first cylindrical body 44. A groove wall 42b at one end of the first groove 42, at which the first shaft hole 41 is positioned, is defined by a circumferential surface having an arcuate section positioned on the same axis as that of the first shaft hole 41 when viewed in the axial direction of the cam shaft 3 or 4.
The first grooves 42 define and function as tracks 49 that determine the moving paths of the rocker arms 7 to 10 in the second support mode (to be described below). The tracks 49 extend from the first shaft holes 41 in a direction opposite to the cam shafts 3 and 4.
Mounting seats 50 that mount the support members 36 are provided between the first support walls 34 on the intake valve side and the first support walls 35 on the exhaust valve side in the journal member 15. The mounting seats 50 project in the axial direction of the cam shafts 3 and 4 from the wall surfaces of the first support walls 34 and 35.
A through hole 51 extending in the cylinder axial direction (the vertical direction in
The mounting bolts 37 extending through the support member 36 are screwed into the screw holes 52 of the mounting seat 50. The support member 36 is mounted on the mounting seat 50 by the mounting bolts 37. When the support member 36 is mounted on the mounting seat 50, spaces S (see
The knock pins 53 of the mounting seats 50 are used to position the support member 36 with respect to the journal member 15. The knock pins 53 fit into pin holes 55 (see
As shown in
The second support walls 56 and 57 and the first support walls 34 and 35 are separate members, and one is connected to be separable to the other by fastening members including the mounting bolts 37.
Also, through holes 58 into which the mounting bolts 37 are inserted and the above-described pin holes 55 are provided between the second support walls 56 and 57 of the support member 36.
As shown in
As shown in
The non-through holes 63 extend in a direction parallel or substantially parallel to the axial direction of the cam shafts 3 and 4.
Second hydraulic oil passages 65 in the support member 36 and the cylinder head 2 are connected to the ends of the non-through holes 63 in the support member 36.
The second hydraulic oil passages 65 are connected to the hydraulic actuator 46 which applies an oil pressure to the second hydraulic oil passages 65 in the second support mode (to be described below). That is, the second shaft holes 61 define portions of the second hydraulic oil passages 65 to which the hydraulic actuator 46 applies the oil pressure.
When applying an oil pressure to the second hydraulic oil passages 65, the hydraulic actuator 46 changes the internal state of the above-described first hydraulic oil passages 45 to a state in which the hydraulic oil freely flows. On the other hand, when applying an oil pressure to the first hydraulic oil passages 45, the hydraulic actuator 46 changes the internal state of the second hydraulic oil passages 65 to a state in which the hydraulic oil freely flows.
The second cylindrical body 64 is fitted into and held by the opening of the non-through hole 63. The inner diameter of the second cylindrical body 64 (the hole diameter of the second shaft hole 61 which opens in the second support wall 56 or 57) is the same as the inner diameter of the above-described first cylindrical body 44 (the hole diameter of the first shaft hole 41 which opens in the first support wall 34 or 35).
A piston 66 is movably fitted into the second cylindrical body 64. The piston 66 receives the oil pressure applied to the second hydraulic oil passage 65. The piston 66 preferably has a closed-end cylindrical shape. The piston 66 is fitted into the second cylindrical body 64 such that the bottom portion is positioned on the opening side of the second shaft hole 61. A stopper 66a is provided on the opening-side end of the piston 66.
The stopper 66a determines a stop position when the piston 66 advances by the oil pressure in the second hydraulic oil passage 65. The stopper 66a according to this preferred embodiment preferably has a flange shape projecting outward in the radial direction of the piston 66. When an outer bottom surface 66b of the piston 66 is positioned on the same plane as that of one end (opening end) of the second cylindrical body 64, the stopper 66a abuts against the other end surface of the second cylindrical body 64. The position of the piston 66 when the stopper 66a regulates the advance of the piston 66 by the oil pressure will simply be called “a retreat position” hereinafter.
As shown in
That is, the second grooves 62 extend from the second shaft holes 61 in a direction opposite to the cam shafts 3 and 4. When viewed in the axial direction of the cam shafts 3 and 4, the shape of the second groove 62 according to this preferred embodiment is preferably an arc around the valve stem distal end 5c or 6c of the intake valve 5 or the exhaust valve 6. A bottom surface 62a of the second groove 62 and an end surface 64a of the second cylindrical 64 are positioned on the same plane. Also, extended portions 67 that avoid interference with the pins 48 of the rocker arms 7 to 10 (to be described below) are provided in the second grooves 62.
The width of the second groove 62 is the same as or slightly larger than the outer diameter of the second cylindrical body 64. This groove width is the same as that of the first groove 42.
A groove wall 62b at one end of the second groove 62 where the second shaft hole 61 is positioned is defined by a circumferential surface having an arcuate section positioned on the same axis as that of the second shaft hole 61 when viewed in the axial direction of the cam shaft.
The second grooves 62 define and function as the tracks 49 that determine the moving paths of the rocker arms 7 to 10 in cooperation with the first grooves 42 in the second support mode (to be described below).
The intake valve rocker arms 7 and 8 in contact with the intake valve driving cam 17 and the exhaust valve rocker arms 9 and 10 in contact with the exhaust valve driving cam 19 have the same structure. As shown in
As shown in
As shown in
The outer diameter of the cylindrical body 73 has a dimension that fits into the first grooves 42 of the first support walls 34 and 35 and the second grooves 62 of the second support walls 56 and 57.
Also, as shown in
The pin 48 of the rocker arms 7 to 10 is preferably a circular column, and, as shown in
The roller 74 is rotatably supported by the rocker arm main body 72 via a bearing 78. The axis of the roller 74 is parallel or substantially parallel to axes of the cam shafts 3 and 4.
As shown in
As shown in
As shown in
As shown in
The first rocker shaft half 83 and the second rocker shaft half 84 extend in the axial direction of the cam shafts 3 and 4 (the vertical direction in
The first rocker shaft half 83 shown in
The second rocker shaft half 84 shown in
As shown in
Furthermore, the second rocker shaft half 84 is movably fitted into the first cylindrical body 44 so as to receive the oil pressure applied to the first hydraulic oil passage 45. That is, the second rocker shaft half 84 defines a piston which moves in the first cylindrical body 44. As shown in
The stopper 84a preferably has a flange shape projecting outward in the radial direction of the second rocker shaft half 84. Also, the stopper 84a abuts against the other end surface 44b of the first cylindrical body 44 in a state in which one end (the front end when advancing) of the second rocker shaft half 84 is fitted into the third shaft hole 85 of the rocker arm 7. The position of the second rocker shaft half 84 when the stopper 84a regulates the advance of the second rocker shaft half 84 will simply be called “an advance position” hereinafter.
One end of a compression coil spring 86 abuts against the bottom of the recess 84b of the second rocker shaft half 84. The compression coil spring 86 biases the second rocker shaft half 84 positioned in one end of the through hole 43 and the second rocker shaft half 84 positioned in the other end of the through hole 43 in directions away from each other. Therefore, if the oil pressure applied to the first hydraulic oil passage 45 including the through hole 43 is interrupted for some reason, the spring force of the compression coil spring 86 moves the second rocker shaft half 84 to the advance position.
As shown in
The first support mode is used when the hydraulic actuator 46 applies the oil pressure to the first hydraulic oil passage 45 in the support 11.
When the oil pressure is applied to the first hydraulic oil passage 45 and the hydraulic oil in the second hydraulic oil passage 65 freely flows, the rocker shaft 81 moves to the position shown in
In the first support mode, as shown in
In the first support mode, therefore, the rotations of the intake valve driving cam 17 and the exhaust valve driving cam 18 are converted into reciprocal motions by all the rocker arms 7 to 10 and transmitted to the intake valve 5 or the exhaust valve 6 to set the normal operation state.
On the other hand, the mode shifts to the second support mode shown in
In the second support mode, as shown in
In this state, the presser 71 rolls on the distal end surface of the shim 25 as the rocker arm 7 swings, because the contact portion 71a of the presser 71, which is in contact with the intake valve 5 or the exhaust valve 6, has an arcuate section.
After the apex 17b of the cam 17 passes the roller 74, the rocker arm 7 is pressed by the pressing mechanism 82, moves along the track 49, and returns to the initial position. In this state, the rocker arm 7 swings between the position of maximum lift shown in
When the rocker arm 7 swings along the track 49, as shown in
In the second support mode, therefore, no driving force is transmitted from all the rocker arms 7 to 10 to the intake valve 5 or the exhaust valve 6, so the intake valve 5 or the exhaust valve 6 is kept closed, thus setting the cylinder resting state.
When returning to the normal operation state from the cylinder resting state, the oil pressure need only be applied to the first hydraulic oil passage 45. This is because the moving path of the rocker arm 7 is regulated by the track 49. In the second support mode, the rocker arm 7 is positioned in the above-described initial position because the base circular portion 17a of the cam 17 comes into contact with the roller 74.
This initial position is a position where one end of the track 49 regulates the movement of the cylindrical body 73. When the rocker arm 7 is thus positioned in the initial position, the third shaft hole 85 of the rocker arm 7 and the first and second shaft holes 41 and 61 are positioned on the same axis. That is, when the rocker arm 7 is positioned in the initial position by applying the oil pressure to the first hydraulic oil passage 45, the second rocker shaft half 84 readily moves to the advance position by the oil pressure.
Consequently, the second support mode correctly shifts to the first support mode.
In the valve gear 1 for an engine according to this preferred embodiment, the normal operation state and the cylinder resting state are switched by moving the rocker shaft 81 in the axial direction. That is, the valve gear 1 for an engine according to this preferred embodiment uses a simple structure as the support structures 11 to 14 of the rocker arms 7 to 10. In the valve gear 1 for an engine, therefore, the reliability of the switching operation of switching the rocker arm support modes is higher than that of the conventional valve gear described in Japanese Patent Laid-Open No. 2008-151115.
The track 49 according to this preferred embodiment is defined by the first and second grooves 42 and 62 in the side surfaces of the first and second support walls 34, 35, 56, and 57, which face the rocker arms 7 to 10. The projecting portions 73a of the cylindrical bodies 73, which are shaped to be fitted into the first and second grooves 42 and 62, are provided on the side surfaces of the rocker arms 7 to 10 which face the first and second support walls 34, 35, 56, and 57, so as to project from these side surfaces.
In this preferred embodiment, the track 49 uses portions of the first and second support walls 34, 35, 56, and 57 without using any dedicated member. Accordingly, when implementing the second support mode in which the rocker arms 7 to 10 are supported to be swingable along the track 49, it is unnecessary to increase the number of elements so the manufacturing cost is decreased.
The first and second shaft holes 41 and 61 according to this preferred embodiment open in the bottom portions of the first and second grooves 42 and 62. The third shaft holes 85 of the rocker arms 7 to 10 are positioned on the same axes as the axes of the cylindrical bodies 73 (projections), and extend through the rocker arms 7 to 10. The diameter of the first and second shaft holes 41 and 61 is the same as that of the third shaft holes 85.
In this preferred embodiment, the cylindrical body 73 moves along the first and second grooves 42 and 62, and is positioned in a position where the cylindrical body 73 faces the first and second shaft holes 41 and 61. Therefore, the rocker shaft 81 fits into the first and second shaft holes 41 and 61 and the third shaft hole 85. This makes it possible to accurately and rapidly align the third shaft hole 85 with the first and second shaft holes 41 and 61 by using the fit between the cylindrical body 73 and the first and second grooves 42 and 62.
Accordingly, this preferred embodiment provides a valve gear that smoothly performs the operation of shifting the second support mode to the first support mode.
The first and second grooves 42 and 62 according to this preferred embodiment preferably have an arc shape around the valve stem distal end 5c or 6c of the intake valve 5 or the exhaust valve 6 when viewed in the axial direction of the cam shafts 3 and 4. In addition, the first and second grooves 42 and 62 preferably have a shape matching the swinging direction of the rocker arms 7 to 10 in the second support mode. In this preferred embodiment, therefore, the rocker arms 7 to 10 smoothly swing in the second support mode, and this reduces an output loss caused when the rocker arms 7 to 10 swing as the cam shafts 3 and 4 rotate in the cylinder resting state.
Furthermore, abrasion of the sliding portions of the cylindrical bodies 73 of the rocker arms 7 to 10 and the first and second grooves 42 and 62 is reduced, so it is possible to maintain the initial performance for a long time period.
In the valve gear 1 for an engine according to this preferred embodiment, the first support mode is used by applying an oil pressure to the first hydraulic oil passages 45, and the second support mode is used by applying the oil pressure to the second hydraulic oil passages 65.
Accordingly, the rocker shafts 81 are forcedly moved by the oil pressure when switching between the first and second support modes. Therefore, this preferred embodiment provides a valve gear which increases the reliability of the operation of switching between the first and second support modes.
The rocker arms 7 to 10 according to this preferred embodiment include the pins 48 (stoppers) which face the second rocker shaft halves 84 and pistons 66 in a state in which the second support mode is used and the rocker arms 7 to 10 swing.
In this preferred embodiment, therefore, the second rocker shaft halves 84 and pistons 66 do not interfere with the swinging motions of the rocker arms 7 to 10 in the second support mode. Accordingly, the rocker arms 7 to 10 always correctly swing in the cylinder resting state, so a valve gear for an engine which further increases the operation reliability is provided.
The first support walls 34 and 35 and the second support walls 56 and 57 according to this preferred embodiment are preferably separate members, and one is detachably connected to the other by using the mounting bolts 37 (fastening members).
In this preferred embodiment, therefore, the first and second grooves 42 and 62 may be made by machining the first support walls 34 and 35 and the second support walls 56 and 57. Accordingly, it is possible to provide a valve gear for an engine which is easily manufactured although the valve gear includes the track 49 defined by the grooves in order to regulate the swinging motions of the rocker arms 7 to 10.
The first support walls 34 and 35 according to this preferred embodiment are integrated with the cam shaft journal member 15 of the cylinder head 2.
Accordingly, this preferred embodiment need not include any mounting portions to mount the first support walls 34 and 35 on the cam shaft journal member 15, and hence reduces the size and cost thereof.
The contact portion 71a of the rocker arms 7 to 10 according to this preferred embodiment, which comes into contact with the valve stem of the intake valve 5 or the exhaust valve 6 is provided on one end of the rocker arms 7 to 10 so as to have an arcuate section when viewed in the axial direction of the cam shafts 3 and 4. The shape of the projecting end of the contact portion 71a is a shape obtained by connecting the first arc 76 and the second arc 77. The radius R1 of the first arc 76 positioned in the other end of the rocker arms 7 to 10 is smaller than the radius R2 of the second arc 77 positioned in one end of the rocker arms 7 to 10.
The contact portion 71a of the rocker arms 7 to 10 according to this preferred embodiment preferably has an arcuate section, and hence rolls on the shim 25 (a valve stem) as the rocker arms 7 to 10 swing in the second support mode. Of the plurality of arcs defining the projecting end of the contact portion 71a, the first arc 76 having a small radius comes into contact with the shim 25 when the swinging angle of the rocker arms 7 to 10 increases. When the swinging angle of the rocker arms 7 to 10 increases, the cylindrical bodies 73 of the rocker arms 7 to 10 swing in the direction away from the cam shafts 3 and 4.
That is, the presser 71 of the rocker arms 7 to 10 rolls along the distal end surface of the shim 25 without falling off from the distal end surface, until the swinging angle of the rocker arms 7 to 10 becomes the maximum.
Accordingly, this preferred embodiment provides a valve gear for an engine capable of switching between the normal operation state and cylinder resting state by using the cam shafts 3 and 4 having a large valve lift amount.
The support may have a structure as shown in
Only a portion of a valve gear 101 for an engine according to the second preferred embodiment differs from the valve gear 1 for an engine explained with reference to
As shown in
In addition, the first and second grooves 106 and 107 according to this preferred embodiment do not have the extended portions 47 and 67 as in the first preferred embodiment.
As shown in
The first rocker shaft half 111 and the second rocker shaft half 112 are movably fitted, with their openings facing each other, into first and second shaft holes 41 and 61 and the third shaft hole 85. The first rocker shaft half 111 shown in
Also, a compression coil spring 113 is accommodated in the first rocker shaft half 111 and the second rocker shaft half 112. The compression coil spring 113 biases the rocker shaft halves 111 and 112 in directions away from each other. In this preferred embodiment, the compression coil spring 113 corresponds to “a spring member.”
A closed-end cylindrical piston 114 is movably fitted into the first shaft hole 41 (a first cylindrical body 44) according to this preferred embodiment. The piston 114 is used to receive the oil pressure applied to a first hydraulic oil passage 45. The piston 114 is movably fitted into the first cylindrical body 44 such that the bottom portion is in contact with the first rocker shaft half 111. A flange-shaped stopper 114a projecting outside in the radial direction is provided on the opening-side end of the piston 114.
The stopper 114a regulates the movement of the piston 114a by abutting against an end surface 44b of the first cylindrical body 44. As shown in
A hydraulic actuator 46 according to this preferred embodiment sets a state in which hydraulic oil freely flows through both the first hydraulic oil passage 45 and a second hydraulic oil passage 65 in the first support mode. Also, the hydraulic actuator 46 applies the oil pressure to both the first hydraulic oil passage 45 and the second hydraulic oil passage 65 in the second support mode.
In the valve gear 101 for an engine disclosed in this preferred embodiment, when the first support mode is used and the oil pressure is reduced in the first hydraulic oil passage 45 and second hydraulic oil passage 65, the spring force of the compression coil spring 113 pushes the first rocker shaft half 111 and the second rocker shaft half 112. Then, as shown in
On the other hand, when the second support mode is used, the oil pressure is applied to the first hydraulic oil passage 45 and the second hydraulic oil passage 65. In this case, the piston 114 in the first shaft hole 41 pushes the first rocker shaft half 111 toward the rocker arms 102 to 105, and the piston 66 in the second shaft hole 61 pushes the second rocker shaft half 112 toward the rocker arms 102 to 105. As shown in
In this preferred embodiment, therefore, the first support mode and the second support mode are switched by only switching the state in which the oil pressure is applied to both the first hydraulic oil passage 45 and the second hydraulic oil passage 65, and the state in which oil pressure is reduced in the two hydraulic oil passages 45 and 65. In this preferred embodiment, the hydraulic circuit is simplified compared to a case in which the application and the stopping of the oil pressure are individually switched in the two hydraulic oil passages 45 and 65. Accordingly, this preferred embodiment provides a valve gear for an engine that reduces the manufacturing cost of the hydraulic actuator 46 and the hydraulic circuit.
In the first preferred embodiment and the second preferred embodiment described above, the first groove 42 and second groove 62 preferably have an arcuate shape. However, the present invention is not limited to this. As shown in
Even in this preferred embodiment, the same effects as those of the above-described preferred embodiments are obtained.
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
Number | Date | Country | Kind |
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2013-252909 | Dec 2013 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2014/081695 | 12/1/2014 | WO | 00 |