JPH051515A - Valve timing changeable mechanism - Google Patents

Abstract

PURPOSE:To provide a valve timing changeable mechanism which achieves reduction of a power consumption at the time of actuation, prevention of abrasion at abrasive parts, and improvement in fuel consumption performance. CONSTITUTION:When a brake torque is applied to an advancing drum 5, an advancing plate 7 is moved axially to change a phase of mutual connection between a sprocket 3 and a hub 4. A key member 54 interlocked with the drum 5 to move is guided by a guide groove 44 provided at the hub 4. The key member 54 moves along the guide groove 44 to be prohibited by a prohibiting part to prohibit it from moving, and held by a holding part to receive it and hold it. A need of applying a brake torque continuously is thus eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for changing the valve timing of an engine, and more particularly to a variable valve timing mechanism for changing the phase between a crankshaft and a camshaft.

[0002]

2. Description of the Related Art As is well known, the valve timing of an engine has an appropriate value that varies depending on the engine speed, load, etc., and if fixed uniquely, high efficiency cannot be expected.
Therefore, as a variable valve timing mechanism, there is one that changes the phase between the crankshaft and the camshaft as seen in, for example, Japanese Patent Application Laid-Open No. 2-102305 (F01L 1/34). Already proposed. That is, as will be described with reference to FIG. 1 as an embodiment of the present invention, the variable valve timing mechanism disclosed in the above publication discloses a sprocket 3 and a cam shaft 2 which are connected to a crank shaft by a toothed belt or a chain. There is an advancing plate 7 which propulsively interconnects both of the hubs 4 connected to each other by meshing with the diagonal slot 72. The advancing plate 7 is arranged on the advancing drum 5 so as to be screwable. Yes, when a brake torque is applied to the advancing drum 5 by the retarder 8, the advancing plate 7 moves axially on the advancing drum 5 to change the angular position (phase) of the interconnection between the sprocket 3 and the hub 4. It is supposed to do.

[0003]

However, in the prior art, in order to continuously maintain the angular displacement between the sprocket 3 and the hub 4, that is, the phase difference of the camshaft 2 with respect to the crankshaft, the advancing drum 5 is braked. Since the torque has to be continuously applied and the frictional force is continuously applied, there is a disadvantage that the friction portion is worn. Further, since the brake torque must be continuously applied, there is power consumption such as electric power and mechanical force, and the applied brake torque becomes a load of rotation. Therefore, the driving force of the crankshaft for driving the camshaft 2 is required. Was incurred.

The present invention has been made in view of the above background, and it is possible to reduce power consumption during operation, prevent abrasion of frictional parts, and reduce driving loss of the crankshaft to improve fuel efficiency. It is an object of the present invention to provide a variable valve timing mechanism capable of improving the above.

[0005]

In order to achieve the above object, the present invention is directed to a support means connected to a cam shaft and rotating around the cam shaft, and a drive means supported by the support means and driven by a crankshaft. A variable valve timing mechanism comprising: a phase conversion means for interconnecting the drive means and the support means and changing the phase of both means in accordance with the brake torque in order to change the phase of the camshaft with respect to the crankshaft, When the phase is changed by the phase conversion means, a holding means for holding the changed phase is provided.

Further, the holding means is extended around the cam shaft to guide the movement of the key member and the key member which moves in association with the supporting means or the phase converting means, and stops the movement of the key member. It is characterized in that it is provided with a guide groove formed with a blocking portion and a holding portion for receiving and holding the key member whose movement is stopped by the blocking portion.

[0007]

The operation of the present invention will be described. When the phase is changed by the phase conversion means, the changed phase is held by the holding means. Therefore, it is not necessary to continuously apply the brake torque to the phase conversion means.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a preferred embodiment of a variable valve timing mechanism according to the present invention, which shows an end portion of a cylinder head of an engine.

A bearing 10 for supporting a journal 20 of the cam shaft 2 is formed on the cylinder head 1.
Although not shown, the cam shaft 2 is provided with a cam that operates an intake valve or an exhaust valve. The cam shaft 2 is adapted to be rotated in synchronization with the crank shaft via a toothed belt or a chain which is in driving relation with the sprocket 3 attached to the end of the cam shaft 2.

The variable valve timing mechanism according to the present invention has a hub 4, which is attached to the end face 21 of the camshaft 2 with bolts 24. Therefore hub 4
Is fixed to the camshaft 2 and rotates with it.

In the hub 4, a disc portion 40 extending in the radial direction is adjacent to the head mounting side of the chain cover 11, and an annular advancing drum 5 is arranged in a cylindrical portion 41 thereof.

The advancing drum 5 has a substantially U-shaped cross section, and its axial movement is stopped by a retaining ring 6 which is fitted into an annular step formed at the tip of the hub 4. , Is mounted rotatably between the disc portion 40 of the hub 4. A male screw 50 is formed on the cylindrical outer peripheral surface of the advancing drum 5. This male screw 5
0 is meshed with a corresponding internal thread 70 formed on the inner peripheral surface of the annular advancing plate 7.

The advancing plate 7 is formed with a plurality of slots 71 extending straight in the axial direction on the outer peripheral part thereof. These slots 71 ... Are the disc parts 40 of the hub 4.
The corresponding lugs 43 provided on the inner peripheral surface of the flange 42 that axially protrudes from the peripheral portion are engaged. This rug 4
3 are extended straight in the axial direction, and the slots 71 are engaged with the advancing plate 7.
Cannot rotate with respect to the hub 4, but can move in the axial direction.

The sprocket 3 is mounted via a bearing 34 between the sprocket 3 and the flange 42 so as to be rotatable with respect to the hub 4. However, it cannot move in the axial direction. The sprocket 3 has a plurality of lugs 30 formed on its inner peripheral surface and having side walls obliquely extending in the axial direction. The slanted side walls of the lugs 30 are engaged with the corresponding slanted slots 72 formed in the outer peripheral portion of the advancing plate 7. Therefore, as the advancing plate 7 moves in the axial direction, the slanted slots 72 formed in it and the lugs 30 of the sprocket 3 work in combination to rotate the sprocket 3 with respect to the hub 4. That is, the axial movement of the advancing plate 7 is converted into the relative rotation of the sprocket 3 with respect to the hub 4.

A retarder 8 is formed in the annular recess of the advancing drum 5. That is, the armature 80 of the retarder 8 is formed into an annular body having a substantially L-shaped cross section, and the outer peripheral portion thereof is fitted in the annular stepped portion formed on the advancing drum 5. Armature 80
An annular coil 81 is fixed to the. An electric wire 82 is connected to the coil 81. The electric wire 82 penetrates the end cover 12 and is guided to the driver of the coil 81. The retarder 8 is prevented from rotating with respect to the end cover 12 by an electric wire 82, and the outer peripheral portion of the retaining ring 6 enters a corresponding annular stepped portion formed on the inner peripheral surface of the armature 80 and is stretched. Have been released, which has stopped axial movement.

Advancing drum 5 and sprocket 3
A spiral spring 35 is interposed between and. The spiral spring 35 applies a bias force to the advancing drum 5 in a direction opposite to the brake torque applied by the retarder 8. Also, Advancing Drum 5
The outer peripheral surface is provided with a contact piece 51 projecting in the radial direction at a position on the end cover 12 side. This contact piece 51
When the advancing drum 5 makes one full rotation with respect to the sprocket 3, the abutting part abuts on the corresponding abutting piece 31 formed at one location on the sprocket 3 periphery.

A guide groove 44 extending in the circumferential direction is formed in the cylindrical portion 41 of the hub 4. Guide groove 44
A key member 54 is slidably engaged with the. The key member 54 has its head protruding from the guide groove 44, and this head is engaged with a corresponding linking groove 52 formed on the inner peripheral surface of the advancing drum 5. The link groove 52 is
The inner peripheral surface of the advancing drum 5 is extended in the axial direction.

As shown in FIG. 2, the guide groove 44 extends in the circumferential direction and has both ends adjacent to each other, but is not connected in an annular shape. In the path of the guide groove 44, a substantially triangular island portion 45 is provided on the terminal side when viewed in the braking torque direction of the retarder 8, whereby the path is formed at the tip 4 of the island portion 45.
It is bifurcated on the 6 side and again meets and is closed on the opposite side 47 side of the island portion 45. The opposite side 47 of the island part 45 is
The center is slightly recessed to form a concave shape.
The groove walls facing each other are provided with recesses 48 in opposition to each other,
It is configured in a stepwise manner extending from the recess 48 to the terminal end 49. The key member 54 can move freely with respect to the above-mentioned path, but its head portion has the linkage groove 5 of the advancing drum 5.
Since it is engaged with 2, it moves in association with the rotation of the advancing drum 5.

During operation of the engine, the advancing drum 5 rotates integrally with the sprocket 3, the hub 4 and the cam shaft 2. At this time, the advancing drum 5 is biased in the bias direction by the biasing force of the spiral spring 35, and the contact piece 51 of the advancing drum 5 is stopped by the contact piece 31 of the sprocket 3 and is thus drawn. As shown in FIG. 3 (A), the key member 54 takes an angular position (phase) at the starting end of the guide groove 44.

When the coil 81 of the retarder 8 is excited, the generated electromagnetic force exerts a braking action on the advancing drum 5, and the rotation of the advancing drum 5 is slightly slowed by the brake torque, so that the spiral spring 3 is rotated.
Since the bias force of 5 is blocked, the hub 4 rotates relatively fast, and the advancing plate 7 rotates with both screws 5.
It will move along the 0, 70 mesh. The axial movement of the advancing plate 7 causes the sprocket 3 to move to the hub 4
Cause a rotation against. On the other hand, at this time, the brake torque delays the rotation of the advancing drum 5, so that the key member 54 relatively moves toward the terminal end 49 side of the guide groove 44, and as shown in FIG. The tip of the island 45 is guided to the left by the path 46, and the recess 48 is formed.
Be hit by. This is because the tip end 46 of the island portion 45 extends beyond the center of the groove. And the coil 81
If the excitation is turned off, the braking torque disappears, so that the advancing drum 5 tries to return in the bias force direction of the spiral spring 35. Therefore, the key member 54 is formed in the recess 48.
From the opposite side 47 due to the flared end of the opposite side 47, resulting in the displaced angular position (phase) of the sprocket 3 relative to the hub 4.
Is maintained.

That is, although the phase of the interconnection between the sprocket 3 and the hub 4 is changed by applying the brake torque to the advancing drum 5 by the retarder 8, the brake torque is continuously applied in order to continue this change state. It is not necessary, and since the key member 54 is abutted against the opposite side 47 even after the brake torque is cut, the angle change between the sprocket 3 and the hub 4, that is, the predetermined phase of the camshaft 2 with respect to the crankshaft is continued. Can be kept. The release of the phase difference during the holding is performed by applying the brake torque again. That is, when the retarder 8 is actuated again, the key member 54 on the opposite side 47 of the island portion 45 is pulled out to the terminal end 49 this time. Next, when the excitation of the coil 81 is turned off, as shown in FIG.
The key member 54 is guided by the path in which the island portion 45 is viewed to the left and advances toward the starting end of the guide groove 44, and the phase of the sprocket 3 with respect to the hub 4 is returned to the original state. This is because the recess 48 and the terminal end 49 which continue stepwise are displaced from the opposite side 47.

As described above, since the phase change state can be continuously maintained without continuously applying the brake torque, it is possible to prevent abrasion of the friction portion between the retarder 8 and the advancing drum 5. The application of the brake torque by the retarder 8 may be temporarily performed when the phase is changed and when the phase is released, so that the power consumption during operation can be significantly reduced. Further, since the brake torque is not continuously applied, the drive loss of the crankshaft can be reduced, and the fuel efficiency can be improved / improved.

[0023]

As described in detail in the above embodiments, according to the valve timing variable mechanism of the present invention, when the phase is changed by the phase conversion means, the changed phase is held by the holding means. Therefore, it is not necessary to continuously apply the brake torque to the phase conversion means. Therefore, it is possible to reduce power consumption during operation and prevent abrasion of the frictional portion. Moreover, since the brake torque is not applied continuously, the drive loss of the crankshaft can be reduced,
Fuel consumption performance can be improved and improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of a hub for explaining a guide groove.

FIG. 3 is a development view of a guide groove portion sequentially showing an operating state of a key member.

[Explanation of symbols]

2 cam shaft 3 sprockets 4 hubs 5 Advancing Drum 7 Advancing board 8 retarders 54 key members 44 Guide groove

Claims (2)

[Claims] 1. A support means connected to a cam shaft to rotate around the cam shaft, a drive means supported by the support means and driven by a crankshaft, and the drive means and the support means are interconnected. In addition, in a valve timing variable mechanism having a phase conversion means for changing the phase of both means in accordance with the brake torque to change the phase of the camshaft with respect to the crankshaft, the phase after the change when the phase is changed by the phase conversion means A valve timing variable mechanism comprising a holding means for holding a valve. 2. The holding means is extended around a cam shaft to guide the movement of the key member and the key member that moves in association with the supporting means or the phase converting means, and the movement of the key member is stopped. 2. The variable valve timing mechanism according to claim 1, further comprising a guide groove formed with a blocking portion for holding and a holding portion for receiving and holding the key member whose movement is stopped by the blocking portion.