JP2623712B2 - Variable valve timing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable valve timing device.

(Prior art)

2. Description of the Related Art Some modern engines include a variable valve timing device that changes a valve timing and a valve lift amount according to the load state of the engine for the purpose of improving output and reducing fuel consumption.

FIG. 3 shows an example of the variable valve timing device. In this device A, a cam block D, which is formed integrally with a low-speed valve opening / closing cam B having a low-speed cam profile and a high-speed valve opening / closing cam C having a high-speed cam profile, is attached to a camshaft E. The cam block D is movably connected with a sprite, and a shifter fork F is engaged with the cam block D. The shifter fork F moves along the axial direction of the camshaft E based on the rotation speed of the engine, and moves the cam block D. As a result, the low speed cam B or the high speed cam C in the cam block D selectively occupies just above the valve G according to the engine speed to open and close the valve G, and the engine is efficiently operated. Be driven. The symbol H in the figure is a rocker arm in the SOHC type engine.

As shown in FIGS. 4 (a) and 4 (b), the low-speed cam B and the high-speed cam C have the same base circle diameters Br and Cr, while the low-speed cam B and the high-speed cam B have the same size. Also, the lift amount of the high-speed cam C is set large. Therefore, in the variable valve timing device A, when switching the cam for operating the valve G from the cam B to the cam C, when the valve G is lifted by the cam B,
As shown by the broken line in FIG. 3, the lift portion side surface Cl of the cam C comes into contact with the rocker arm H and the cam block D cannot be moved, so that the base circle peripheral surface Bb of the cam B is on the slipper surface of the rocker arm H. In other words, when the cam C does not face the side area of the rocker arm H, the cam block D is instantaneously moved to switch the cam.

By the way, in a multi-cylinder engine, in order to obtain a stable output, the phase of the process for each cylinder, that is, the opening / closing timing of the valve is made different, as is known. For this reason, when the above-described variable valve timing device is applied to a multi-cylinder engine, it is necessary to provide the above-described device for each cylinder, whereby the structure of the engine is complicated and large.

[Object of the invention]

The present invention has been made in view of the above circumstances, and has as its object to provide a variable valve timing device for a multi-cylinder engine having a simple structure.

[Configuration of the invention]

Therefore, in the present invention, a plurality of cam blocks respectively corresponding to valves of each cylinder in a multi-cylinder engine are provided on the camshaft with their valve timings being different from each other, and moving means is provided on any one of the cam blocks. The above object has been achieved by interposing elastic means acting in the axial direction of the camshaft between the cam block linked to the moving means and another cam block.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

1 (a), 1 (b) and 1 (c) show examples in which the variable valve timing device according to the present invention is applied to a DOHC type multi-cylinder engine. The camshaft 1 has a first cylinder
First cam block 10 for operating 100 valves 101
And a second cam block 20 for operating the valve 201 of the second cylinder 200 are spline-connected so as to be movable in the axial direction of the camshaft 1. The first
The cam block 10 has a low-speed valve opening / closing cam 11 and a high-speed valve opening / closing cam 12 integrally arranged side by side. Similarly, the second cam block 20 has a low-speed valve opening / closing cam 21 and a high-speed valve opening / closing cam 22. Are juxtaposed side by side. Further, the first cam block 10 and the second cam block 20 are provided on the camshaft 1 with different valve timings.

Above the camshaft 1, a guide shaft 2 extends in parallel with the camshaft 1, and engages with the first cam block 10 and the second cam block 20, respectively. The first shifter block 3 and the second shifter block 4 are movably fitted.
Further, a rack 5 is formed in the first shifter block 3 along the axial direction of the guide shaft 2, and a pinion 6 meshes with the rack 5. A motor 7 is linked to the pinion 6, and the rack 5, the pinion 6, and the motor 7 constitute a moving unit 8.

On the side of the first cam block 10, a first plate 30 reaching the side area of the second cam block 20 is fixed, while on the second cam block 20, the first plate 30 is fixed.
A second plate 40 overlapping with 30 is fixed. The first plate 30 has elongated holes 31 and 32 extending in the axial direction of the guide shaft 2, while the second plate 40 has pins 41 and 42 fitted in the elongated holes 31 and 32, respectively.
Is fixed. Further, the first plate 30 and the second plate 40 are formed with square holes 33 and 43 having the same shape at positions corresponding to each other. A compression spring 50 as an elastic means matched with the direction is mounted. The compression spring 50 is interposed between the first cam block 10 and the second cam block 20 via the first plate 30, the second plate 40, the first shifter block 3, and the second shifter block 4. It has become dressed.

Now, if the engine is running in the low speed range,
First shifter block 3 and second shifter block 4
Occupies the position shown in FIG. 1 (c),
The cam block 10 and the second cam block 20 are positioned so that the low-speed cams 11, 21 occupy immediately above the valves 101, 201, respectively. Thus, the valve 101 of the first cylinder 100 is opened and closed by the low speed cam 11 of the first cam block 10 via the shim 102 and the lifter 103, and the valve 201 of the second cylinder 200 is operated by the shim 202 and the lifter 2
The opening / closing operation is performed by the low speed cam 21 of the second cam block 20 via 03. FIG. 2 (a) conceptually shows the state described above.

When the number of revolutions of the engine rises and exceeds the threshold value, the moving means 8 operates to move the first shifter block 3 to the left in FIG. 2, whereby the first cam block 10 moves to the left. At this time, as shown in FIG.
At the time when the base circle peripheral surface of the cam 11 and the base circle peripheral surface of the cam 12 both face downward in the drawing, in other words, the peripheral portion of the cam 12 is not occupied in the top side region of the valve 101. At the time, the first cam block
10 moves instantaneously from the position of FIG. 2 (a) to the position of FIG. 2 (b), and the high-speed cam 12 occupies just above the valve 101. Here, the top side region of the valve 101 refers to a region on the side of the lifter 103 and lower than the slipper surface of the lifter 103. On the other hand, due to the leftward movement of the first plate 30 accompanying the movement of the first shifter block 3, the second plate 40 is also moved via the compression spring 50, whereby the first cam block 20 moves leftward. At this time, FIG.
The high speed cam in the second cam block 20 as shown in FIG.
When the lift portion 22a of the motor 22 faces downward, the lift portion 22a hits the lifter 203, and the second cam block 20 is moved from the position shown in FIG. 2 (a) to the position shown in FIG. 2 (b). Go slightly left until you stop. For this reason, a relative displacement occurs between the first plate 30 linked to the first cam block 10 and the second plate 40 linked to the second cam block 20, and the edge of the square hole 33 The compression spring 50 is compressed and deformed by the portion 33a and the edge 43a of the square hole 43 as shown in FIG. 2 (b). The camshaft 1 rotates from the state shown in FIG. 2 (b) to the state shown in FIG. 2 (c), and both the base circle peripheral surface of the cam 21 and the base circle peripheral surface of the cam 22 in the second cam block 20 are shown in the figure. When facing downward, in other words, at a time when the peripheral portion of the cam 22 is not occupying the top side region of the valve 201, the second cam block 20
Due to the elastic restoring force of the compression spring 50, the compression spring 50 instantaneously moves from the position shown in FIG. 2B to the position shown in FIG. 2C, and the high-speed cam 22 occupies just above the valve 201. Thus, valve 101,
201 is opened and closed by high-speed cams 12 and 22, respectively. Here, the top side region of the valve 201 refers to a region on the side of the lifter 203 and lower than the slipper surface of the lifter 203.

When the engine speed falls from the high speed range and falls below the threshold value, the moving means 8 operates in reverse to move the first shifter block 10 rightward, and the first plate 30, the compression spring 50, and the second plate 40 , The second shifter block 20 also goes to the right. At this time, the low-speed cams 11, 21 in each of the cam blocks 10, 20 are set to have a smaller lift amount than the high-speed cams 12, 22, so that the low-speed cam 11.21
Each cam block 10.20 smoothly moves rightward without being caught by the lifters 103, 203 of 1,201, and the low-speed cams 11, 21 occupy just above the valves 101, 201. Thus each valve 10
1,201 is opened and closed by the low speed cams 11,21.

In this example, an engine having two cylinders is illustrated, but the present invention can of course be effectively applied to an engine having three or more cylinders. Further, the elastic means is not limited to the compression spring. For example, when the moving means 8 is provided in the second shifter block 20 in FIG. 1, it goes without saying that the device functions by using a tension spring as the elastic means.

〔The invention's effect〕

As described in detail above, according to the variable valve timing device according to the present invention, when the elastic means is interposed between the cam block linked to the moving means and the other cam block, and the two cams cannot move simultaneously. Since the relative displacement between the two cams is absorbed by the elastic means, and the other cam block is moved by the return force of the elastic means when the other cam block becomes movable. A plurality of cam blocks corresponding to a plurality of cylinders can be operated by one moving unit. As a result, it has become possible to switch the valve timing in a multi-cylinder engine with a simple structure.

[Brief description of the drawings]

1 (a) is a plan view of a variable valve timing device according to the present invention, FIG. 1 (b) is a sectional view taken along line bb of FIG. 1 (a), and FIG. FIG. 2 is a cross-sectional view taken along the line cc of FIG. 1 (b), and FIG.
FIG. 3 (c) is a conceptual cross-sectional side view sequentially showing an operation mode of the variable valve timing device according to the present invention, and FIG. 3 is a cross-sectional side view of a main part showing a conventional variable valve timing device. a) and (b) are respectively IV in FIG.
FIG. 4 is a sectional view taken along line a-IVa and a sectional view taken along line IVb-IVb. 1 ... Camshaft, 2 ... Guide shaft, 3,4 ...
Shifter block, 8 ... Moving means, 10, 20 ... Cam block, 11, 21 ... Low speed valve opening / closing cam, 12, 22 ... High speed valve opening / closing cam, 30, 40 ... Plate, 50 ... Compression Spring, 100,200 …… Cylinder, 101,201 …… Valve

Claims (1)

(57) [Claims] A cam block, in which a plurality of valve opening / closing cams having different cam profiles are arranged side by side and integrally formed, is fitted to a camshaft so as to be non-rotatable and free to move in the axial direction to operate the valve. By moving the cam block in a direction in which the adjacent cam occupies the region immediately above the valve at a time when the peripheral edge of the cam adjacent to the cam being occupied does not occupy the top side region of the valve. A variable valve timing device for selecting and switching a cam for operating the valve, wherein a plurality of cam blocks respectively corresponding to valves of each cylinder in a multi-cylinder engine are provided with different valve timings. The moving means is provided on the camshaft and is linked to any one of the cam blocks. Between the block and the other of the cam blocks, the variable valve timing apparatus being characterized in that interposed elastic means acting in the axial direction of the camshaft.