JP2924489B2 - Valve train of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve mechanism for driving intake and exhaust valves of an internal combustion engine, and more particularly to a valve mechanism for varying a valve lift and a valve timing.

[0002]

2. Description of the Related Art Conventionally, as this kind of technology, for example, a technology disclosed in Japanese Utility Model Laid-Open No. 75610/1985 is known. In this technique, a cylinder head 51 of an engine is provided with a valve 52 for intake and exhaust, as shown in FIG. A rocker arm 54 is supported by the rocker shaft 53 such that the rocker arm 54 can swing up and down about the axis thereof. By the rocking of the rocker arm 54, the valve 5 located at the lower end of the tip of the rocker arm 54
2 is opened and closed.

On both sides of the rocker arm 54, elongated holes 56 are formed which extend linearly in a direction perpendicular to the axial direction of the cam 55. The roller shaft 5 is provided in the elongated hole 56.
The roller 58 is rotatably supported on the roller shaft 57 in a state in which the roller 58 is in contact with the cam 55.
Further, outside the rocker arm 54, a U-shaped frame 59 is provided so as to sandwich the rocker arm 54, and both ends of the roller shaft 57 are supported by the frame 59.

In the above-described valve mechanism, the cam nose 55a comes into contact with the roller 58 as the cam 55 rotates, whereby the roller 58 is pressed downward. Then, the rocker arm 54 is swung about the rocker shaft 53 by the pressing force. By this swing, the valve 52 provided at the tip of the rocker arm 54 is moved downward in the figure against the urging force of the coil spring 60, and the intake / exhaust port (not shown) is opened. Thereafter, as the cam 55 further rotates, the cam base 55b of the cam 55 comes into contact with the roller 58, so that the valve 52 is moved upward by the urging force of the coil spring 60, and the intake / exhaust port is closed. By repeating the above operation, the valve 52 is moved up and down, and the intake and exhaust ports are opened and closed.

In the rocker arm 54, a solenoid 61 for moving the roller 58 in the horizontal direction in FIG.
And a movable iron core 62. Then, by appropriately changing the voltage applied to the solenoid 61,
The movable iron core 62 is moved in the left-right direction in FIG. Along with this, the frame body 59 is moved in the horizontal direction in FIG.
And the roller 58 is moved in the longitudinal direction of the long hole 56. Therefore, the contact position of the cam 55 with respect to the roller 58 is changed. As a result, the timing at which the cam nose 55a hits the roller 58 and the swing amount of the rocker arm 54 are changed, and the opening / closing timing of the valve 52 and the lift amount thereof are changed.

[0006]

However, in the above-mentioned prior art, the long hole 5 for guiding the movement of the roller 58 is used.
6 is simply formed so as to extend linearly in a direction perpendicular to the axial direction of the cam 55, that is, in the horizontal direction in FIG. Therefore, the roller shaft 57 and the roller 5
8 is moved linearly along the elongated hole 56, and the distance between the rotation center C1 of the cam 55 and the rotation center C2 of the roller 58 changes with the movement of the roller 58. Became. That is, when the roller 58 is moved from the left end of the long hole 56 shown by a solid line to the right end of the long hole 56 shown by a two-dot chain line, the rotation center C1 of the cam 55 and the roller 58 are moved.
The distance from the rotation center C2 of the roller 5 increases.
8 between the outer peripheral surface of the cam 8 and the cam 55
May be unnecessarily large. When the tappet clearance S becomes larger than necessary during the rotation of the cam 55, the cam nose 5
5a hits the roller 58, and as a result, a tapping sound may be generated.

In the above technique, a solenoid 61 for moving the roller 58 and the like is provided in the rocker arm 54. For this reason, the inertial weight of the rocker arm 54 increases by the amount of the solenoid 61, and when the rocker arm 54 is caused to swing at high speed with the high-speed rotation of the engine, the followability of the rocker arm 54 is reduced. It was not good.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a valve operating mechanism for an internal combustion engine for driving a valve for intake and exhaust of the internal combustion engine. , It is possible to prevent the occurrence of tapping noise due to tappet clearance between the cam and roller,
Another object of the present invention is to provide a valve operating mechanism of an internal combustion engine that can drive a valve at a high speed by following a high-speed rotation of the internal combustion engine.

[0009]

In order to achieve the above object, the present invention relates to a valve operating mechanism for an internal combustion engine for driving a valve for intake and exhaust of the internal combustion engine. A rocker shaft, which is formed on an eccentric part whose axis is eccentric with respect to the part and is rotatably supported by a rocker housing about the axis of the main body part, and a base circle provided on a camshaft of the internal combustion engine. Equipped cam,
A first rocker arm having a base end swingably supported by the main body, driving a valve at a substantially front end, and a guide portion formed on both sides substantially concentric with a base circle; A second rocker arm whose portion is swingably supported by the eccentric portion, and a first rocker arm supported by the second rocker arm and abutting on a guide portion of the first rocker arm. And a roller shaft rotatably supported by the roller shaft and rotatably supported by the roller shaft and provided in contact with a cam. The mechanism is the gist.

[0010]

According to the above construction, the roller is pressed by the cam by rotating the cam provided on the camshaft of the internal combustion engine. The pressing force is transmitted to the first rocker arm via the roller shaft, and the first rocker arm is swung. With this swing, the valve is opened and closed by the substantially distal end of the first rocker arm.

Here, unlike the first rocker arm, the second rocker arm is supported by an eccentric portion having an axis eccentric to the axis of the rocker shaft.
For this reason, when the rocker shaft is rotated,
The roller shaft is moved while being guided by the guide portion, and the roller shaft, the roller and the second rocker arm are moved relatively to the first rocker arm. As a result, the contact position of the cam with respect to the roller changes, and the timing at which the valve is opened and closed and the lift amount thereof are changed. At this time, since the guide portion is formed substantially concentric with the base circle, the distance between the rotation center of the cam and the rotation center of the roller does not change with the movement of the roller. Therefore, the tappet clearance between the cam and the roller does not increase more than necessary with the rotation of the cam.

Further, since the roller is relatively moved with respect to the first rocker arm by rotating the rocker shaft, means for separately moving the roller is provided for the first or second rocker arm. It is not necessary. Therefore, the inertial weight of the rocker arm is reduced by the amount that no means for separately moving the roller is provided.

[0013]

【Example】

(First Embodiment) A first embodiment embodying a valve train of an internal combustion engine according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a valve operating mechanism of an engine as an internal combustion engine mounted on a vehicle in this embodiment. FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 1
FIG. 7 is a sectional view taken along line BB of FIG. As shown in these drawings, a known valve mechanism 2 is provided in a cylinder head 1 of an engine. The valve mechanism 2 includes an exhaust valve 3 provided to be vertically movable with respect to the cylinder head 1.
A valve retainer 4 provided on an upper portion of the valve 3;
Provided between the valve retainer 4 and the cylinder head 1;
It is composed of a coil spring 6 for urging the valve 3 upward.

The valve mechanism 2 is driven by a valve mechanism based on rotation of a cam 7 provided on a camshaft. Hereinafter, the valve mechanism will be described.

As shown in FIG. 1, a rocker shaft 8 composed of a main body 9 and an eccentric portion 10 is rotatably supported on a rocker housing 8 of the engine. The main body 9 of the rocker shaft 11 has a cylindrical shape, and its axis 9 a is the center of rotation of the rocker shaft 11. Further, the eccentric part 10 has a smaller diameter than the main body part 9 and
It is integrally formed so as to be sandwiched by the main body 9. Further, the axis 10a of the eccentric part 10 is
Is eccentric to

An outer arm 12 as a first rocker arm is swingably supported at the base end 12a of the main body 9. Tip portion 12 of outer arm 12
b is in contact with the valve mechanism 2 described above. Then, as the outer arm 12 swings, the distal end of the outer arm 12 pushes the valve 3.

On both sides of the outer arm 12, a pair of elongated holes 13 as guide portions are formed. The pair of elongated holes 13 are formed on concentric circles of a base circle B of the cam 7 provided on the camshaft. The cam 7
Is well known, and includes a cam base 7a having a shape conforming to the base circle B, and a cam nose 7b whose distance from the rotation center to the outer periphery is longer than the cam base 7a. In this embodiment, it is assumed that the camshaft and the cam 7 are rotated integrally counterclockwise in FIGS.

On the other hand, the eccentric portion 10 of the rocker shaft 11
, An inner arm 14 as a second rocker arm is swingably supported at a base end portion 14a thereof so as to be sandwiched by the outer arm 12. A pair of shaft holes 1 are provided on both sides of the substantially end portion 14b of the inner arm 14.
The roller shaft 16 is supported in the coaxial hole 15. Further, the roller shaft 16 extends into the elongated hole 13 of the outer arm 12, and movement in the elongated hole 13 is allowed. Further, a roller 17 is rotatably supported by a roller shaft 16 via a needle 18. As shown in FIGS. 2 and 3, the roller 17 is in contact with the lower surface of the cam 7.

That is, when the cam 7 is rotated, the cam nose 7 b of the cam 7 comes into contact with the roller 17. Then, the roller 17 is pressed by the contact of the cam nose 7 b, and this pressing force is transmitted to the outer arm 12 via the roller 17 and the roller shaft 16. Therefore, the outer arm 12 is swung downward as indicated by a two-dot chain line arrow.
By this downward swing, the valve 3 located substantially below the distal end portion 12b of the outer arm 12 is pressed downward against the urging force of the coil spring 6, and the exhaust port is opened.
When the cam base 7a contacts the roller 17, the outer arm 12 is swung upward by the urging force of the coil spring 6. This upward swing causes the valve 3
Is returned upward, and the exhaust port is closed. As described above, the valve 3 is moved up and down with the rotation of the cam 7, and the opening and closing of the exhaust port are repeatedly performed.

As shown in FIG. 1, the rocker shaft 11
A driven gear 21 is fixed on the main body 9 of the first embodiment. The driven gear 21 is meshed with a drive gear 24 fixed on a motor shaft 23 of a step motor 22. When the step motor 22 is driven, the drive gear 24 is rotated. With this rotation, the driven gear 2
1 is rotated, and the rocker shaft 11 is rotated.

In this embodiment, the stepping motor 2
An electronic control unit (ECU) 25 for controlling the drive of the ECU 2 is provided. Various signals corresponding to the coolant temperature, the engine speed, the negative pressure of the intake pipe, the throttle opening, and the like are input to the ECU 25 from various sensors for detecting the operating state of the engine. ECU2
The stepping motor 22 is electrically connected to the output side of the step No. 5. Then, based on these various signals, the ECU 25 adjusts the lift amount and the opening / closing timing of the valve 3 in accordance with the operating state at that time.
2 to output a control signal for driving. That is, for example, when the current engine state is a low load state, the ECU 2
5 controls the stepping motor 22 to rotate forward, and in the case of a high load state, to rotate the stepping motor 22 reversely. Accordingly, the rocker shaft 11 is rotated clockwise or counterclockwise.

Next, the operation of the valve train of the engine configured as described above will be described. When the step motor 22 is driven to rotate forward under the control of the ECU 25, FIG.
As shown in (1), the roller shaft 16 is moved to the front end side (left side in the figure) in the elongated hole 13. Accordingly, the roller 17 is also located on the left side of the outer arm 12.

On the other hand, when the step motor 22 is driven to rotate in the reverse direction, the rocker shaft 11 is rotated in the direction opposite to the above case. At this time, since the axis 10a of the eccentric portion 10 is eccentric with respect to the axis 9a of the main body 9, when the rocker shaft 11 is rotated, for example, 180 ° from the state of FIG. As shown, the inner arm 14 supported by the eccentric part 10 moves rightward with respect to the outer arm 12. Here, the roller shaft 16 is guided in the elongated hole 13 and relatively moves to the base end side (the right side in the figure). Further, since the roller 17 is supported by the roller shaft 16 to be moved, the roller 17 also moves to the right. Therefore, the contact position of the cam 7 with the roller 17 is different from the above case.

More specifically, the stepping motor 2
When 2 rotates forward, the valve 3 moves as shown by the solid line in FIG. When the step motor 22 is rotated in the reverse direction, the valve 3 moves as shown by a two-dot chain line in FIG. That is, when the step motor 22 is rotated in the reverse direction, the roller 17
The cam nose 7b moves the roller 17
Contact timing is delayed. Therefore, the timing at which the valve 3 is driven to open and close is delayed. Further, when the step motor 22 is rotated in the reverse direction, the lift amount (maximum movement amount) L2 of the valve 3 is larger than the lift amount L1 when the step motor 22 is rotated in the forward direction. When the rotation speed of the cam 7 is constant, the time T during which the valve 3 is opened regardless of the position of the roller 17 and the roller shaft 16 is set.
a and Tb are constant.

Here, the elongated hole 13 in this embodiment is
The cam 7 is formed concentrically with the base circle B. Therefore, when the roller 17 is moved as described above and the contact position of the cam 7 with the roller 17 is changed, the distance between the rotation center of the cam 7 and the rotation center of the roller 17 does not change. . Therefore, the tappet clearance between the cam 7 and the roller 17 does not become larger than necessary. As a result, it is possible to prevent occurrence of a tapping sound between the cam nose 7b and the roller 17 due to an increase in tappet clearance.

In this embodiment, since the roller 17 is moved relative to the outer arm 12 by rotating the rocker shaft 11, means for separately moving the roller 17 such as a solenoid mechanism is provided. It does not have to be provided for the outer arm 12. For this reason, the inertia weight of the outer arm 12 can be reduced by the amount that the means for separately moving the roller 17 is not provided. Therefore, when the outer arm 12 is to be swung at high speed with the high-speed rotation of the engine, the outer arm 12
Followability can be improved.

Further, in this embodiment, when the engine has multiple cylinders, it is not necessary to provide a means for moving the roller 17 for each cylinder, and one rocker shaft 11 may be provided.
Thus, the opening and closing operation of the valve 3 of each cylinder can be adjusted. Therefore, the overall configuration can be simplified by that much.

(Second Embodiment) Next, a second embodiment of the present invention, which embodies a valve mechanism of an internal combustion engine, will be described with reference to FIGS. In this embodiment, the same members as those of the first embodiment described above are denoted by the same reference numerals, description thereof will be omitted, and different points will be mainly described.

As shown in FIG. 6, in this embodiment, the main body 32 of the rocker shaft 31 is opposite to the first embodiment.
In contrast, the eccentric portion 33 has a large diameter. Further, the rocker shaft 31 is rotatably supported on a rocker housing (not shown) around an axis 32 a of the main body 32. Further, the axis 33a of the eccentric part 33 is
It is eccentric with respect to the axis 32 a of the main body 32.

An inner arm 34 as a first rocker arm is swingably supported by the main body 32 at a base end 34a thereof. On both sides of the inner arm 34, a pair of long holes 35 are formed as guide portions located on concentric circles of the base circle B.

On the other hand, the eccentric portion 33 of the rocker shaft 31
The outer arm 36 as a second rocker arm is held at the base end 3 so as to sandwich the inner arm 34.
It is swingably supported at 6a. Outer arm 36
The shaft holes 37 on both sides of the substantially end portion 36b of the
Is supported. The roller shaft 16 has a roller 17.
Are rotatably supported. The roller shaft 16 extends into a long hole 35 of the inner arm 34 and is guided in the long hole 35. Further, a thrust washer 38 is interposed between the roller 17 and the inner arm 34. The thrust washer 38 allows the roller 17 to move smoothly in the left-right direction in FIG.

Next, the operation of the valve train configured as described above will be described. First, when the step motor 22 is rotated forward, the roller shaft 16 is located at the front end side (left side in the figure) in the elongated hole 35. Accordingly, the roller 17 is also located on the left side of the inner arm 34. When the step motor 22 is rotated in the reverse direction, as shown in FIGS.
The outer arm 36 supported by the eccentric portion 33 is moved relative to the inner arm 34 to the right in FIG. Therefore, the roller shaft 16 is moved to the base end side (the right side in the figure) in the elongated hole 35, and the roller 17 is also moved to the right side of the inner arm 34. Therefore, the contact position of the cam 7 with respect to the roller 17 changes as compared with the above case. That is,
When the step motor 22 is rotated in the reverse direction, the timing at which the valve 3 is opened and closed is delayed compared to when the step motor 22 is rotated in the normal direction, and the lift amount (maximum movement amount) of the valve 3 is increased.

In this embodiment, similarly to the first embodiment, the elongated hole 35 is formed on a concentric circle of the base circle B. Therefore, even if the contact position of the cam 7 with respect to the roller 17 is changed, an effect equivalent to that of the first embodiment described above can be obtained in which occurrence of a tapping sound can be prevented.

Further, the weight can be reduced by the amount that the means for separately moving the roller 17 is not required, and the followability of the inner arm 34 accompanying the high-speed rotation of the engine can be improved.

Further, since the means for moving the roller 17 for each cylinder need not be provided, the overall structure can be simplified. (Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. Note that, in this embodiment, the first and second
The same members as those in the configuration of the embodiment are denoted by the same reference numerals, description thereof will be omitted, and different points will be mainly described.

As shown in FIG. 8, in this embodiment, the main body 32 of the rocker shaft 31 is similar to the second embodiment.
In contrast, the eccentric portion 33 has a large diameter. Further, the rocker shaft 31 is rotatably supported on a rocker housing (not shown) around an axis 32 a of the main body 32. Further, the axis 33a of the eccentric part 33 is
It is eccentric with respect to the axis 32 a of the main body 32.

An inner arm 39 as a first rocker arm is swingably supported by the main body 32 at a base end 39a thereof. The inner arm 39 is formed with a pair of guide grooves 40 as a guide portion by partially hollowing the upper portions on both sides thereof. The upper surface of the guide groove 40 is located on a concentric circle of the base circle B.

On the other hand, the eccentric portion 33 of the rocker shaft 31
The outer arm 41 as a second rocker arm is sandwiched between the base end 4 and the inner arm 34 so as to sandwich the inner arm 34.
It is swingably supported at 1a. Outer arm 41
The shaft holes 37 on both sides of the substantially end portion 41b of the
Is supported. The roller shaft 42 has a large diameter portion 42a.
And is rotatably supported on the guide groove 40. That is, the roller shaft 42 is guided by the guide groove 40 while being rotated.

In this embodiment, the operation is almost the same as that of the second embodiment. In the second embodiment, the roller shaft 16 is guided while sliding in the elongated hole 35.
This embodiment is greatly different in that the large diameter portion 42a of the roller shaft 42 is guided while being rotated by the guide groove 40. That is, the roller shaft 42 is guided by the guide groove 40 with the rotation of the rocker shaft 31. At this time, since the roller shaft 42 moves while rotating, the roller shaft 42 moves between the guide groove 40 and the roller shaft 42. There is not much friction between them. Therefore, the occurrence of wear due to the repeated movement of the roller shaft 42 can be prevented, and the durability of the valve train can be improved.

It should be noted that the present invention is not limited to the above-described embodiment, and may be implemented as follows, with a part of the configuration being appropriately changed without departing from the spirit of the invention. (1) In each of the above embodiments, the rocker shafts 11, 31
The driven gear 21 and the step motor 22 are driven to rotate the motor shaft 23 and the driving gear 24 to rotate the driven gear 21 and the rocker shafts 11 and 31. It may be configured.

For example, as shown in FIG. 10, a pinion 43 is fixed on the rocker shafts 11 and 31, and the pinion 43 is rotated by a rack 45 which is moved forward and backward by a solenoid 44 to rotate the rocker shafts 11 and 31. You may make it move.

As shown in FIG. 11, an arm 46 is fixed on the rocker shafts 11, 31, and the arm 4
6 is rotated via a link 48 by a movable iron core 47 advanced and retracted by a solenoid 44, and the rocker shafts 11 and 3 are rotated.
1 may be rotated.

(2) In each of the above embodiments, the valve mechanism according to the present invention is applied to the exhaust valve 3.
It may be applied to a valve for intake. (3) The rotation direction of the cam 7 in each of the above embodiments is the same as the swing direction of the outer arm 12 and the inner arms 34 and 39, that is, the counterclockwise direction in FIGS. The directions may be reversed.

(4) Each of the main bodies 9, 32 and each of the eccentric parts 10, 32 of the rocker shafts 11, 31 in each of the above embodiments.
The relationship between the large diameter and the small diameter of 33 may be reversed. That is,
The diameter of the main body 9 may be smaller than that of the eccentric
May be made larger in diameter than the eccentric part 33.

[0046]

As described above in detail, according to the present invention, in the valve operating mechanism of the internal combustion engine for driving the intake / exhaust valve of the internal combustion engine, the first rocker arm has the axial center of the rocker. The second rocker arm is supported by the eccentric part while being supported by the main body that is the center of rotation of the shaft, and the first rocker arm is formed with an elongated hole substantially concentric with the base circle and the roller shaft is inserted. Because the roller is moved on a substantially concentric circle of the base circle, the rocking shaft is rotated, so that when the contact position of the cam with respect to the roller changes, the tapping sound when the cam rotates. This has an excellent effect that generation of pits can be prevented.

Further, the weight can be reduced by the amount that the means for separately moving the roller is not required, so that there is an excellent effect that the valve can be driven by following the high speed rotation of the internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a valve operating mechanism of an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1 in the first embodiment.

FIG. 3 is a sectional view taken along line BB of FIG. 1 in the first embodiment.

FIG. 4 is a partial sectional view showing a state when the rocker shaft is rotated from the state of FIG. 1 in the first embodiment.

FIG. 5 is a timing chart showing the relationship between the amount of movement of the valve that fluctuates with the rotation of the rocker shaft and the movement timing in the first embodiment.

FIG. 6 is a schematic configuration diagram showing a valve operating mechanism of an internal combustion engine according to a second embodiment of the present invention.

FIG. 7 is a sectional view taken along line CC of FIG. 6 in a second embodiment.

FIG. 8 is a schematic configuration diagram showing a valve operating mechanism of an internal combustion engine according to a third embodiment of the present invention.

FIG. 9 is a sectional view taken along line DD of FIG. 8 in a third embodiment.

FIG. 10 is a schematic diagram showing a rocker shaft rotating mechanism in another embodiment embodying the present invention.

FIG. 11 is a schematic view showing a rocker shaft rotation mechanism different from FIG. 10 in another embodiment.

FIG. 12 is a schematic configuration diagram showing a valve operating mechanism of an engine in a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 3 ... Valve, 7 ... Cam, 8 ... Rocker housing, 9, 32 ... Body part, 9a, 10a, 3
2a, 33a: shaft center, 10, 33: eccentric part, 11, 31
... rocker shaft, 12 ... outer arm as first rocker arm, 12a, 14a, 34a, 36a ...
Base end, 12b, 14b, 34b, 36b...
3, 35: long hole as a guide portion, 14: inner arm as a second rocker arm, 16, 42: roller shaft, 17: roller, 34, 39 ... inner arm as a first rocker arm, 36, 41: outer arm as a second rocker arm, B: base circle.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01L 13/00

Claims (1)

(57) [Claims] 1. A valve operating mechanism for an internal combustion engine for driving an intake / exhaust valve of the internal combustion engine, comprising: a main body and an eccentric portion whose axis is eccentric relative to the main body. A rocker shaft rotatably supported by a rocker housing about an axis of the unit, a cam provided on a camshaft of the internal combustion engine and having a base circle, and a base end swinging on the main body. A first rocker arm, which is supported so as to be able to drive the valve at a substantially distal end thereof, and has guide portions formed on substantially both sides of the base circle substantially concentrically, and a base end portion swinging to the eccentric portion. A second rocker arm movably supported, and a second rocker arm supported by the second rocker arm, abutting on the guide portion of the first rocker arm, and Te A shaft which is movably supported rollers, wherein is rotatably supported by the roller shaft, a valve operating mechanism for an internal combustion engine, characterized in that a roller provided contactable to said cam.