JP3060586B2 - Valve system for 4-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve system for a four-stroke engine capable of changing a valve lift, a valve opening timing, etc. of an intake / exhaust valve according to an operating condition.
In particular, the present invention relates to a valve train for a four-stroke engine with improved assemblability of a hydraulic actuator for rotating a rocker shaft.

[0003]

2. Description of the Related Art Generally, in a four-cycle engine mounted on a vehicle such as an automobile and a motorcycle, intake and exhaust valves are disposed above a combustion chamber, and these valves are driven by a valve train. That is, the valve train includes a camshaft interlocking with the crankshaft of the engine, and the cam formed on the camshaft moves the intake / exhaust valve up and down at a predetermined timing.

[0004]

By the way, the above-mentioned four-stroke engine is required to obtain a high output within a wide rotation speed range from a low rotation speed range to a middle and high rotation speed range, that is, to have a wide power band. Is desirable.

However, in the conventional valve operating apparatus, since the valve opening / closing timing and the lift amount are fixed, only an output characteristic having a peak value in a specific engine speed range is obtained. A choice must be made between emphasizing output characteristics or emphasis on output characteristics in the middle and high speed ranges.

The present invention has been made in view of the above circumstances, and can improve the engine output within a wide rotation speed range, and can easily assemble a hydraulic actuator that rotates a rocker shaft. It is another object of the present invention to provide a valve train of a four-cycle engine capable of preventing unnecessary minute rotation of a rocker shaft during operation of a hydraulic actuator.

[Configuration of the Invention]

[0008]

According to the present invention, an eccentric large-diameter portion is rotatably supported, a pinion is formed at one end in the axial direction, and a rotation range around the axis is formed at the other end in the axial direction. Rocker shafts each having a rotation restricting groove for restricting the rotation, a first rocker arm directly inserted into the rocker shaft, and inserted into the eccentric large-diameter portion disposed on both sides of the first rocker arm. The second and third rocker arms, and the first and second rocker arms.
And first, second and third cams for operating the third and third rocker arms, respectively, and a piston slidable by hydraulic pressure of hydraulic oil in the cylinder. A hydraulic actuator having a meshable rack formed therein, wherein the second and third cams are formed with the same cam profile, and the cam profile of the first cam is formed differently from the cam profile. The hydraulic actuator is provided with an urging body for urging the piston in the push-back direction, and a stopper abutment is provided at a base end of the piston for abutting against a piston stopper installed in the cylinder. Part is projected in the axial direction to restrict the piston push-back position by the urging body. When assembling the pressure actuator, when the pinion and the rack are engaged with the rocker shaft fixed with the stopper locked in the rotation restricting groove, of the first meshing teeth, the piston pushing of the teeth of the rack is performed. The return-direction-side tooth tip portion is set so as to be in contact with the tooth surface of the pinion in the piston pushing-out direction of the tooth.

[0009]

Therefore, according to the valve train of the four-cycle engine according to the present invention, the rocker shaft is rotated by a predetermined angle to rotate the eccentric large-diameter portion, whereby the cam floor surface of the second and third rocker arms is rotated. Is vertically changed relative to the cam floor surface of the first rocker arm. When the cam floor surfaces of the first and third rocker arms are moved downward with respect to the cam floor surface of the first rocker arm, the contact between the second and third rocker arms and the second and third cams is released, and the first rocker arm is released. And the first cam come into contact, and the valve of the four-stroke engine is driven by the first cam.

Further, when the cam floor surfaces of the second and third rocker arms are changed to a position substantially above or at the same position with respect to the cam floor surface of the first rocker arm, the first rocker arm is moved to the first position.
The contact between the rocker arm and the first cam is released, the second and third rocker arms contact the second and third cams, respectively, and the valve of the four-cycle engine is operated by the second and third cams. . Thus, by selecting the cam by rotating the rocker shaft, the engine output can be improved over a wide rotation speed range.

Further, when assembling the hydraulic actuator, first, the stopper is brought into contact with the rotation restricting groove of the rocker shaft and locked, thereby restricting the rotation of the rocker shaft in one direction. Next, the hydraulic actuator is assembled in a state where the piston is pushed back by the urging body and the stopper contact portion at the piston base end is in contact with the piston stopper in the cylinder. At the time of this assembling, when the rack formed on the piston and the pinion formed on the rocker shaft are engaged with each other, of the teeth that first mesh with each other, the tip of the tooth of the rack in the piston push-back direction is the pinion. Of the rack comes into contact with the tooth surface in the piston pushing direction, so that after the assembly, the tooth tips of the rack are pushed along the tooth surface of the pinion. As a result, the rack slides a small amount in the piston pushing direction, so that the stopper abutting portion at the piston base end is separated from the piston stopper in the cylinder, and only the rotation restricting groove of the rocker shaft continues to abut the stopper, and the rocker shaft Is regulated in one direction.

As described above, since the rocking position of the rocker shaft can be regulated by locking the stopper in the rotation regulating groove, torsion is generated between the pinion and the stopper in this rocker shaft, and the rocker shaft is actuated when the hydraulic actuator is operated. In this rotation restricting position, unnecessary minute rotation of the rocker shaft can be prevented.

Further, as described above, the hydraulic actuator can be assembled in a state where the rotation of the rocker shaft in one direction is restricted only by locking the stopper in the rotation restricting groove of the rocker shaft. Therefore, the hydraulic actuator can be assembled simply by installing the hydraulic actuator downward from above and engaging the rack of the hydraulic actuator with the pinion of the rocker shaft, thereby facilitating the assembly.

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a perspective view showing an embodiment of the valve train of the four-stroke engine according to the present invention. FIG. 6 is a partial plan view of a cylinder head to which the valve train of FIG. 2 is applied. FIG. 8 is a sectional view taken along line VII-VII of FIG.
It is sectional drawing which follows each I line.

[0016] The valve train is disposed on the intake side and the exhaust side of one cylinder of the engine. Therefore, the valves 1 and 2 shown in FIGS. 2 to 5 are arranged for intake or exhaust.

In this embodiment, a low-speed cam 3 as a first cam, and a middle-high speed cam 4 as a second cam disposed on one side and the other side of the low-speed cam 3 respectively.
And a camshaft 6 (FIGS. 4 and 5) having a middle and high speed cam 5 as a third cam, and cams 3, 4 and 5
, A low-speed rocker arm 7 as a first rocker arm, a medium-high speed rocker arm 8 as a second rocker arm, and a medium-high speed rocker arm 9 as a third rocker arm, and these rocker arms 7, 8, and 9 And a rocker shaft 11 into which the supporting portions 7a, 8a and 9a are fitted and rotatably supported by a rocker shaft bearing portion 18 (FIG. 8) described later.

The tip of the low-speed rocker arm 7 branches in two directions, and both of these branch tips 7b abut the stem heads of the valves 1 and 2, respectively, which open and close the combustion chamber of the engine (not shown). In addition, the low-speed rocker arm 7
Is directly inserted into the rocker shaft 11 and is rotatably provided.

The support portion 8a of the medium-high speed rocker arm 8
It is rotatably fitted to the rocker shaft 11 via an eccentric bush 12 having a larger diameter than the rocker shaft 11. As shown in FIG. 4, the eccentric bush 12 has an axis eccentric from the center of the rocker shaft 11, and is detachably fixed to the rocker shaft 11 by a bush pin 10. Therefore, the eccentric bush 12 functions as an eccentric large diameter portion in the rocker shaft 11.

As shown in FIG. 3, the rocker arm 9 for medium and high speeds is used.
Is rotatably fitted to the rocker shaft 11 through an eccentric bush 13 having the same shape as the eccentric bush 12 and eccentric in the same direction.
The eccentric bush 13 is also detachably fixed to the rocker shaft 11 by the bush pin 10, and functions as an eccentric large diameter portion.

The lower surfaces of the distal ends 8a and 9a of the medium and high speed rocker arms 8 and 9 are in contact with one and the other branch distal ends 7b of the low speed rocker arm 7 via shims 14a, respectively. The contact points between the branch tip 7b of the low-speed rocker arm 7 and the tips 8b and 9b of the middle and high-speed rocker arms 8 and 9 are set substantially on the axis of the valves 1 and 2.

Therefore, as shown in FIG. 4, when the low-speed cam 3 presses down on the cam floor surface 7c of the low-speed rocker arm 7 and lowers its tip 7b (when the low-speed cam 3 is operated). In other words, the distal ends 8b and 9b of the rocker arms 8 and 9 do not come down together with the branch distal end 7b. On the other hand, as shown in FIG.
And 5 depress the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9, respectively (when the medium and high speed cams 8 and 9 are operated), the distal end portions 8b and 9b of these rocker arms 8 and 9 move at low speed. Since each branch tip 7b of the rocker arm 7 is pressed down, the branch tip 7b is forcibly lowered.

The shim 14a is a shim having a T-shaped vertical cross section.
b is fitted from above. The valve stem heads of the valves 1 and 2 are covered with a covered cylindrical shim 14b, and the lower surface of the branch tip 7b of the low-speed rocker arm 7 abuts the shim 14b. These shims 14a and 1
4b is used for tappet clearance adjustment of valves 1 and 2.

Among the cams 3, 4 and 5, the middle and high speed cams 4 and 5 have the same cam profile, and the low speed cam 3 has the same cam profile as the middle and high speed cams 4 and 5. Have different cam profiles. That is, the cam profile of the low-speed cam 3 is set such that a valve lift amount and an opening / closing valve timing that are appropriate when the engine is operated in a low rotation speed range. The cam profiles for the middle and high speed cams 4 and 5 are set so that a suitable valve lift amount and opening / closing valve timing are obtained when the engine is operated in a middle / high speed range.

The valve lift amount is determined by the valves 1 and 2
, And corresponds to the cam lift amount. FIG.
4 shows the cam profile of the low-speed cam 3 by a solid line A (cam lift 1a).
Is indicated by a broken line B (cam lift amount 1b). As is clear from FIG. 14, the cam profiles for the middle and high speed cams 4 and 5 are set so that a larger valv lift amount than the low speed cam 3 can be obtained.

The two-dot chain line C in FIG. 14 indicates that the rocker shaft 11 is rotated to position the thick tops 12a and 13a of the eccentric bushes 12 and 13 obliquely forward as shown in FIG. 2 shows the cam profiles of the middle and high speed cams 4 and 5 (when the cam 3 is operated).

By the way, the rotation of the rocker shaft 11 is
As shown in FIG. 2, the operation is performed by a hydraulic actuator 15 that operates using engine oil as hydraulic oil. As shown in FIGS. 6 and 8, the hydraulic actuator 15 is installed in a cam chain chamber 17 located at the center of the cylinder head 16 in the vehicle left-right direction.

A total of four rocker shafts 11 are arranged, one each in the front and rear and right and left directions of the cylinder head 16 in the vehicle, and each of the rocker shafts 11 is arranged to extend in the vehicle left and right direction. Each rocker shaft 11 is rotatably supported by a rocker shaft bearing 18 formed on a cylinder head 16. One rocker shaft 11 is provided with two rocker arms 7 for low speed and rocker arms 8 and 9 for medium and high speed.
They are installed in pairs. Each set of the low-speed rocker arm 7 and the medium- and high-speed rocker arms 8 and 9 has a rocker shaft 1.
The position is regulated together with the rocker shaft 11 by the positioning spring 19 interposed in 1.

Reference numeral 20 in FIG. 6 denotes a lower half bearing hole formed in the upper portion of the rocker shaft bearing portion 18 to support the camshaft 6. Reference numeral 21 denotes a valve guide, and reference numeral 22 denotes a stud bolt insertion hole. further,
Reference numeral 45 in FIG. 8 denotes a bearing housing for the camshaft 6.

As shown in FIGS. 7, 9 and 10, the hydraulic actuator 15 includes an actuator body 24 in which two cylinders 23 are juxtaposed, and a piston 25 accommodated two in each cylinder 23. And a lid 26 that covers the upper part of the actuator body 24. The lid 26 is fixed to the actuator body 24 using a lid mounting bolt 44.

The piston 25 is provided so as to be slidable in the cylinder 23, and a rack 27 is integrally formed at the tip.
The rack 27 is engaged with a pinion 28 formed at a tip end portion which is one end portion in the axial direction of the rocker shaft 11. Also, as shown in FIGS. 6, 7 and 9, two cylinders 23
And a low-speed oil passage 29 communicating with both ends of the two cylinders 23 is formed. A low-speed hydraulic port 31 communicating with the low-speed oil passage 29 and a middle-high speed hydraulic port 32 communicating with the middle-high speed oil passage 30 are formed on the lid 26.

On the other hand, as shown in FIG. 7, an oil passage switching solenoid valve 33 is installed on a head cover 33A that covers the cylinder head 16. The oil passage switching solenoid valve 33 selectively supplies hydraulic pressure to the low-speed hydraulic port 31 or the middle-high speed hydraulic port 32 via the low-speed hydraulic hose 34 and the middle-high speed hydraulic hose 35.

That is, the hydraulic switching solenoid valve 33
In the figure, a spool valve 37 is provided in a valve body 36, and the spool valve 37 is slid by exciting and demagnetizing an electromagnet 38. Valve body 36
Is formed with an oil supply port 39 into which engine oil pressurized by an oil pump (not shown) flows as hydraulic oil. In addition, a relief port 40 is formed in the valve body 36 and the low-speed lubrication port 4
The 1 and medium / high speed oil supply ports 42 are also formed. The low-speed oil supply port 41 and the low-speed hydraulic port 31 of the hydraulic actuator 15 are connected by a low-speed hydraulic hose 34. Further, the medium / high speed oil supply port 42 and the middle / high speed hydraulic port 32 of the hydraulic actuator 15 are connected by a medium / high speed hydraulic hose 35.

Excitation and demagnetization of the electromagnet 38 are controlled based on the engine speed. That is, when the engine speed increases, the engine speed is, for example, about 9500 rpm.
p. m. The electromagnet 38 is excited in the following low rotation speed range,
500r. p. m. This electromagnet 3
8 is demagnetized.

When the electromagnet 38 is excited, the spool valve 37 moves in the direction of arrow Q in FIG. 7 to connect the oil supply port 39 with the low-speed oil supply port 41 and communicate the medium-high speed oil supply port 42 with the relief port 40. I do. For this reason, the hydraulic oil is introduced into the low-speed oil passage 29 from the oil supply port 39 via the low-speed oil supply port 41, the low-speed hydraulic hose 34 and the low-speed hydraulic port 31, and the piston 25 is pushed back in the direction of arrow M shown in FIG. As a result, the pinion 28 rotates in the direction of the arrow O. This causes the rocker shaft 11 to rotate,
As shown in FIG. 4, the thick tops 12a and 13a of the eccentric bushes 12 and 13 move diagonally forward, and the low-speed cam 3 operates the low-speed rocker arm 7.

When the electromagnet 38 is demagnetized, the spool valve 37 is moved to the position shown in FIG. 7 by the urging force of the solenoid return spring 43. As a result, the oil supply port 39 and the medium / high speed oil supply port 42 communicate with each other. In addition, the low-speed refueling port 41 and the relief port 40 communicate with each other. For this reason, the hydraulic oil is introduced from the oil supply port 39 to the medium / high speed oil passage 30 via the medium / high speed oil supply port 42, the medium / high speed hydraulic hose 35, and the medium / high speed hydraulic port 32, and the piston 25 is moved in the direction indicated by an arrow in FIG. The pinion 28 is pushed out in the N direction, and rotates in the arrow P direction. As a result, the rocker shaft 11 rotates, and as shown in FIG. 5, the thick tops 12a and 13a of the eccentric bushes 12 and 13 move obliquely rearward, and the middle and high speed cams 4 and 5 move the middle and high speed rocker arms. Activate 8 and 9.

At the base end of the rocker shaft 11, which is the other end in the axial direction, a rotation restricting groove 46 is formed as shown in FIG. 8 and FIG. A stopper screw 47 as a rotation restricting stopper is screwed into the cylinder head 16. The rotation restricting groove 46 is formed along the circumferential direction around the axis of the rocker shaft 11 and over the rotation angle range of the rocker shaft 11.

The stopper screws 47 are provided so as to be able to abut both ends 48A (low-speed end) and 48 ° (middle-high speed end) of the rotation restricting groove 46. When the rocker shaft 11 rotates in the O direction shown in FIG. 9, the stopper screw 47 abuts on the low-speed end portion 48A as shown in FIG. 1, and the rotational position of the rocker shaft 11 in the O direction is regulated. . When the rocker shaft 11 rotates in the direction P shown in FIG.
, The rotation position of the rocker shaft 11 in the P direction is regulated. In any of these cases, the rocker shaft 11 has
A torsion acts between the stopper screw 47 and the pinion 28 so that the rocker shaft 11 does not rotate slightly when the rotation of the rocker shaft 11 is restricted.

FIG. 7 shows the hydraulic actuator 15.
As shown in FIG. 9, piston guides 49 are fitted to both axial ends of each cylinder 23. A piston spring 50 as an urging member is interposed between the piston guide 49 and the large diameter portion of the piston 25. By the piston spring 50, an urging force is always applied to the piston 25 in the push-back direction of the piston 25 (in the direction indicated by the arrow M in FIG. 9), particularly when the hydraulic actuator 15 is assembled.

As shown in FIGS. 11 and 12, an annular circlip 51 as a piston stopper is fitted to the cylinder 23 of the hydraulic actuator 15 at its axial center position. Further, a stopper abutting portion 52 capable of abutting the circlip is integrally provided at the large-diameter base end of the piston 25 so as to protrude in the axial direction. When the hydraulic actuator 15 is assembled to the cylinder head 16 at the time of assembling the hydraulic actuator 15 to the cylinder head 16 as shown in FIG.
Of the first teeth 53 (rack-side teeth) and 54 (pinion-side teeth), the pinion push-back direction side tooth tip 53 Α of the rack-side teeth 53 is in the piston pushing direction of the pinion-side teeth 54 (arrow Ν direction). The pinion side teeth 54 are set so as to be in contact with the piston pushing direction side tooth surface 54 'of the pinion side teeth 54 on the piston pushing direction side of the side tooth end tip 54A.

That is, first, the actuator 15 is
And it is installed in the cylinder head 16 via a mounting plate 55 shown in FIG. The mounting plate 55 has a rectangular shape and is fixed to the cylinder head 16 at its corners by plate mounting bolts 56. Positioning pins 57 are implanted in the mounting plate 55. When the hydraulic actuator 15 is assembled, the positioning pins 57 are inserted into positioning pin holes 58 of the actuator body 24 and positioned.
Thereafter, a mounting bolt (not shown) is inserted into a mounting bolt hole 59 of the actuator body 24 shown in FIGS. 6 and 12, and a tip of the mounting bolt is screwed to the mounting plate 55.

As described above, the hydraulic actuator 15
At this time, the piston 25 of the hydraulic actuator 15 is moved by an arrow M by a piston spring 50.
In the direction (FIGS. 1 and 9), the stopper contact portion 52 of the large-diameter base end of the piston 25 contacts the circlip 51 as shown in FIG. On the other hand, when assembling the hydraulic actuator 15, the rocker shaft 11 is rotated in the direction of the arrow O (FIG. 9), and the low-speed end 48A of the rotation restricting groove 46 is moved to the stopper screw 47 as shown in FIG.
Is set to abut.

The hydraulic actuator is assembled in such a state. However, since the stopper abutment portion 52 is in contact with the circlip 51, the teeth 53 and 54 that first mesh with the rack 27 and the pinion 28 become the rack side teeth 53. At which the tooth tip 53A can contact the tooth surface 54B of the pinion-side tooth 54, ie, the piston push-back direction tooth tip 53A.
27 between the piston and the piston pushing direction side tooth tip 54A
The position at which the axial dimension δ is a positive value equal to or greater than zero (the push-back direction of the piston 25 is positive). Therefore,
When the hydraulic actuator 15 is assembled, the tooth tips 53A of the rack-side teeth 53 that first mesh with each other are pushed in along the piston pushing direction side tooth surface 54 # of the pinion-side teeth 54 that first mesh with each other, so that the rack 27 moves in the piston pushing direction ( (In the direction of arrow N), the stopper contact portion 52 of the piston 25 is separated from the circlip 51. In this state, the low-speed end 48A of the rotation restricting groove 46 of the rocker shaft 11 abuts against the stopper screw 47,
These stopper screw 47 and low speed end 48A
Only the function of the rocker shaft 11 is restricted.

A guide flange 60 is formed integrally with the piston guide 49 shown in FIGS. 7, 9 and 10, for example, by die casting. This guide tsuba 60
Is slidably provided on the upper peripheral surface of the small diameter portion of the piston 25 in the drawing. Generally, when the rack 27 engages with the pinion 28, a driving reaction force F (FIG. 7) acts on the rack 27 from the pinion 28. Rack 27 axially vertical component F _V of the driving reaction force F acts upward in FIG. Therefore, by the guide collar 60, it will be to support the vertical component F _V of the driving reaction force F, thereby the piston 2
5 in the cylinder 23 is smoothened.

For example, let L ₁ and L ₂ (L ₁ <L ₂ ) be the distances between the end surface of the stopper contact portion 52 and the surface of the piston guide 49 or the tip of the guide flange 60 when the piston 25 is pushed out. , vertical load acting between the large diameter base end and the cylinder 25 of the piston 25 is reduced to L 1 _/ L _2, also halved axial surface pressure of the piston 25. Further, the backlash in the meshing portion of the rack 27 and the pinion 28 is also reduced to _L 1 / _{L 2.}

Next, the function and effect will be described.

When the engine is in the low rotation speed range, the piston 25 of the hydraulic actuator 15 is excited by the hydraulic pressure and the elastic restoring force of the piston spring 50, as shown in FIG. When the rocker shaft 11 is turned back in the direction of arrow O, the thick tops 12a and 13a of the eccentric bushes 12 and 13 are positioned diagonally forward as shown in FIG. Accordingly, the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9 move downward relative to the cam floor surface 7c of the low speed rocker arm 7.
Therefore, the peripheral surfaces of the middle and high speed cams 4 and 5 and the cam floor surfaces 8c and 9c of the middle and high speed rocker arms 8 and 9 are formed.
Is formed between them, and as a result, the middle and high speed cams 4 and 5 idle.

At this time, the low-speed rocker arm 7
Is driven by the urging force of the valve spring 61 (FIG. 4).
Since the cam floor surface 7c is constantly pushed upward with the axis of the rocker shaft 11 as a center, the cam floor surface 7c contacts the peripheral surface of the low-speed cam 3. Therefore, when the camshaft 6 rotates, the valves 1 and 2 move up and down based on the lift characteristic A of the low speed cam 3 shown in FIG. That is,
The valves 1 and 2 open and close the combustion chamber while ensuring a valve lift suitable for a low engine speed range.

On the other hand, when the engine is in the middle / high rotation range, the flow path switching solenoid valve 33 shown in FIG. 7 is demagnetized. Is an arrow Ν
When the rocker shaft 11 is pushed out in the direction and the rocker shaft 11 rotates in the direction of the arrow P, the thick tops 12a and 13a of the eccentric bushes 12 and 13 respectively are positioned obliquely rearward as shown in FIG. As a result, the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9 move relatively upward or to the same position with respect to the cam floor surface 7c of the low speed rocker arm 7, and the cam floor surfaces 8c and 9 are moved.
c comes into contact with the peripheral surfaces of the middle and high speed cams 4 and 5, respectively.

As shown in FIG. 15, the cam lifts of the medium and high speed cams 4 and 5 are larger than those of the low speed cams 3, so that the cam shaft 6 rotates under the condition shown in FIG. In this case, the low speed cam 3 idles, while the medium and high speed cams 4 and 5 drive the valves 1 and 2 via the medium and high speed rocker arms 8 and 9 based on the lift characteristic の in FIG. As a result, valve 1
And 2 open and close the combustion chamber while ensuring a valve lift suitable for the middle and high engine speed ranges of the engine.

According to the above embodiment, the cam profile suitable for the low speed range of the engine is formed on the low speed cam 3, and the cams 4 and 5 suitable for the middle and high speed range of the engine are formed on the middle and high speed cams 4 and 5. A profile is formed, and medium and high speed rocker arms 8 and 9 are rotatably fitted into eccentric bushes 12 and 13 of the rocker shaft 11, respectively.
The low-speed rocker arm 7 is directly inserted into the rocker shaft 11, and the rotation of the rocker shaft 11 causes the low-speed cam 3 to rotate.
The contact between the low-speed rocker arm 7 and the middle and high speed cams 4 and 5 and the middle and high speed rocker arms 8 and 9 can be selected. 4 and 5 can be selectively driven. Therefore, the output of the four-stroke engine can be improved in a wide rotation speed range from the low rotation speed range to the middle and high rotation speed ranges of the engine.

Further, since the low-speed cam 3 and the medium-high speed cams 4 and 5 are selected by rotating the eccentric bushes 12 and 13, a large stress is generated in each part when the cams 3, 4 and 5 are selected. There is no. Therefore, the cams 3, 4, and 5 can be smoothly selected.

Further, the hydraulic actuator 15 is assembled to the cylinder head 16 in a state where the piston 25 is pushed back by the piston spring 50 and the stopper contact portion 52 of the piston 25 contacts the circlip 51 of the cylinder 23. At this time, the stopper contact portion 5
The protrusion amount h of the pinion side teeth 54 of the rack side teeth 53 that first mesh with the piston push-back direction side teeth tips 53 、
The value of the dimension δ is set to a positive value equal to or greater than zero so as to come into contact with the tooth surface 54B in the piston pushing direction on the piston pushing direction. Therefore, after the hydraulic actuator 15 is assembled, the tooth tips 53A of the rack-side teeth 53 become the tooth surfaces 54 # of the pinion-side teeth 54.
, The rack 27 slides slightly in the piston pushing direction (arrow N direction), and the stopper contact portion 52 of the piston 25 and the circlip 51 separate from each other.

However, as shown in FIG. 13, as shown in FIG. 13, the tip 53 A of the tooth in the piston push-back direction of the rack side tooth 53 that first meshes with the pinion side tooth 54 that first meshes.
When the piston extrusion direction Gawaha dimension [delta] ₁ of the distal end portion 54A to a negative value of zero or less, the tooth tip ends of the rack-side teeth 53 and the pinion side teeth 54 collide, that Kamiawaseru these teeth Can not. In order to engage these teeth 53 and 54, there is a method of manually pulling out the rack 27 in the piston pushing direction (the direction of arrow Ν). In this case, the assemblability of the hydraulic actuator 15 is reduced.

Further, as shown in FIG.
If the size [delta] ₂ of a piston extrusion direction Gawaha tip 54A of the third piston push-back direction Gawaha tip 53A and the pinion side teeth 54 is a large negative value of the absolute value than the dimension [delta] _1, rack-side Although the tooth tips of the teeth 53 and the pinion-side teeth 54 do not collide with each other, the tip 53 ′ of the rack-side teeth 53 in the piston pushing-out direction comes into contact with the piston push-back direction-side tooth surface 54C of the piston side teeth 54, so that the pinion 28 Is slightly rotated in the direction of arrow P. Therefore, the low-speed end 48A of the rotation restricting groove 46 and the stopper screw 47
The stopper function in the direction of arrow ス ト ッ パ during the operation of the hydraulic actuator 15 is performed by the stopper contact portion 52 of the piston 25 and the circlip 51. Therefore, the torsion does not act on the rocker shaft 11 in the axial direction, and the rocker shaft 11 slightly rotates at the stop position of the rocker shaft 11 in the direction of the arrow O, which may adversely affect the operation of the low-speed cam 3. There is.

On the other hand, in this embodiment, as shown in FIG. 1, when the hydraulic actuator 15 is assembled, the stopper abutting portion 52 of the piston 25 separates from the circlip 51, so that the rocker shaft 11 During rotation in the direction of the arrow O, the rocker shaft 11 stops because the stopper screw 47 abuts against the low-speed end 48A of the rotation restricting groove 46. Therefore, torsion acts on the rocker shaft 11 between the stopper screw 47 and the pinion 28 in the axial direction, and when the rocker shaft 11 is stopped, the rocker shaft 11 can be prevented from minute rotation. As a result, the operation of the low-speed cam 3 when the rocker shaft 11 is stopped can be improved.

When the hydraulic actuator 15 is assembled, as described above, the stopper screw 47 is attached to the low-speed end 48 # of the rotation restricting groove 46 of the rocker shaft 11.
The hydraulic actuator 15 for assembling the hydraulic actuator 15 to restrict rotation of the rocker shaft 11 in the direction of the arrow O by contacting the It can be realized simply by meshing from below. For this reason, unlike the case of FIG. 13, there is no need to manually pull out the rack 27 in the piston pushing direction, so that the hydraulic actuator 15 can be easily assembled.

The piston guide 49 has a guide flange 6.
0 is formed, so to support the rack shaft direction vertical component F _V of the driving reaction force F which the guide flange 60 acts on the rack,
The sliding of the piston 25 can be made smooth.

In the above-described embodiment, the case where the cam profiles of the middle and high speed cams 4 and 5 are indicated by the broken line の in FIG. 15 has been described. The broken line Β 'of FIG.
The lift of the valves 1 and 2 at the time of medium / high speed rotation of the engine may be changed.

[0060]

As described above, according to the valve train of a four-stroke engine according to the present invention, an eccentric large diameter portion is formed on a rocker shaft rotatably supported,
Since the second and third rocker arms are inserted into the eccentric large-diameter portion and the first rocker arm is disposed between the second and third rocker arms and directly inserted into the rocker shaft, the rotation of the rocker shaft is performed. By selecting the cam described above, the engine output can be improved over a wide rotation speed range.

The hydraulic actuator is provided with an urging member for urging the piston in the push-back direction.
At the base end of the piston, a stopper abutting portion that abuts on a piston stopper installed in the cylinder protrudes to restrict the piston push-back position by the urging body, and the amount of protrusion of the stopper abutting portion When assembling the hydraulic actuator, among the teeth that first mesh with the pinion and the rack, the tip of the tooth of the rack in the piston push-back direction is located on the tooth surface of the pinion in the piston pushing direction. Since it is set to be in contact, the assemblability of the hydraulic actuator that rotates the rocker shaft can be easily implemented, and unnecessary minute rotation of the rocker shaft during operation of the hydraulic actuator can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing a relationship between a rack and pinion teeth, a stopper screw and a rotation restricting groove when the hydraulic actuator shown in FIG. 2 is assembled.

FIG. 2 is a perspective view showing an embodiment of the valve train of the four-stroke engine according to the present invention.

FIG. 3 is a plan view of the valve train of FIG. 2;

FIG. 4 is an operation state diagram showing a low-speed cam operation state of the valve train of FIG. 2;

FIG. 5 is an operation state diagram showing a medium-high speed cam operation state of the valve gear of FIG. 2;

FIG. 6 is a partial plan view of a cylinder head to which the valve train shown in FIG. 2 is applied, omitting an intake / exhaust valve and a valve spring;

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 6;
Sectional drawing which shows the hydraulic actuator which act | operated to operate the cam for middle and high speeds.

FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 6;

FIG. 9 is a cross-sectional view showing a hydraulic actuator that has been operated to operate the low speed cam in the hydraulic actuator of FIG. 1;

FIG. 10 is a right side view of the hydraulic actuator of FIG. 9;

FIG. 11 is an enlarged cross-sectional view showing an XΙ portion of FIG. 9;

FIG. 12 is a sectional view taken along the line II-XII of FIG. 10;

FIG. 13 is a partially cutaway side view showing the relationship between the teeth of the rack and the pinion, the stopper screw, and the rotation restricting groove corresponding to FIG. 1;

14 is a partially cutaway side view showing another relationship between the teeth of the rack and the pinion, the stopper screw, and the rotation restricting groove corresponding to FIG.

FIG. 15 is a graph showing a cam profile of the cam of FIG. 2;

FIG. 16 is a graph showing a first modification of the cam profile shown in FIG.

FIG. 17 is a graph showing a second modification of the cam profile shown in FIG.

[Explanation of symbols]

1, 2 Valp 3 Low-speed cam 4, 5 Medium-high speed cam 7 Low-speed rocker arm 8, 9 Medium-high speed rocker arm 11 Rocker shaft 12, 13 Eccentric bush 15 Hydraulic actuator 23 Cylinder 25 Piston 27 Rack 28 Pinion 46 Rotation restricting groove 47 Stopper screw 50 Piston spring 51 Circlip 52 Stopper abutment part 53 Rack side teeth first meshing 54 Pinion side teeth first meshing 53A Piston push-back direction side tip end part of rack side teeth 54A Piston pushing direction side of pinion side teeth Tooth tip カ ム Cam profile of low speed cam B Cam profile of medium / high speed cam h Projection amount of stopper contact part

Claims (1)

(57) [Claims] An eccentric large-diameter portion is formed so as to be rotatably supported, a pinion is formed at one end in the axial direction, and a rotation restricting groove is formed at the other end in the axial direction to restrict a rotation range around the axis. A rocker shaft formed respectively, a first rocker arm directly inserted into the rocker shaft,
Second and third rocker arms disposed on both sides of the first rocker arm and fitted into the eccentric large-diameter portion, and first and second rocker arms respectively operating the first, second, and third rocker arms. And a third cam, and a hydraulic actuator in which a piston slidable by hydraulic pressure of hydraulic oil is arranged in a cylinder, and a rack formed at a tip end of the piston so as to mesh with a pinion of the rocker shaft is provided. Wherein the second and third cams are formed in the same cam profile, the cam profile of the first cam is formed differently from the cam profile, and the hydraulic actuator pushes the piston in a push-back direction. A biasing body for biasing is installed, and a base end of the piston contacts a piston stopper installed in the cylinder. The stopper abutting portion protrudes in the axial direction to restrict the piston push-back position by the urging member. The amount of axial protrusion of the stopper abutting portion is limited by the rotation regulating groove when the hydraulic actuator is assembled. When the pinion and the rack are meshed with the rocker shaft fixed with the stopper locked, the teeth of the rack that are first meshed with the piston push-back direction side tooth tips are the teeth of the pinion. A valve train for a four-stroke engine, wherein the teeth are set so as to be in contact with the tooth surface in the piston pushing direction of the teeth.