JPH02149708A - Valve timing control device of 4-cycle engine - Google Patents

Abstract

PURPOSE:To change the open/close timing of an intake valve with simple constitution by interposing an elastic body which can position a sprocket wheel in its turning direction around its shaft in relation to an intake cam shaft, between the sprocket wheel and the intake cam shaft. CONSTITUTION:Compression coil springs 26 which can position an intake cam shaft 7 and a cam sprocket 11, energize the cam sprocket 11 and a flange part 20 in the opposite direction by an energizing force larger than the drive force of a crankshaft applied on the cam sprocket 11 until an engine r.p.m. reaches a preset r.p.m.. When the engine r.p.m. increases beyond the set value, the drive force applied to the cam sprocket 11 overcomes the energizing force of the compression coil spring 26 and the cam sprocket 11 makes turning movement by an angle alpha corresponding to the gap l between a stopper pin 25 and opening parts 23, 24 relatively to a flange part 20. Accordingly, when the engine r.p.m. increases beyond the set value, a phase difference takes place on an intake cam 9 and an event angle can be made larger.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for changing the opening/closing timing of an intake valve in a four-stroke engine equipped with separate intake camshafts and exhaust camshafts.

[Prior Art] In this type of four-stroke engine, in order to increase the intake efficiency, it is necessary to optimize the opening/closing timing of the intake valve with respect to the engine rotation speed. For this reason, in high-speed, high-output engines, the timing at which the intake valve closes is delayed. In other words, as shown in Figure 7, the event angle (E,
A) is set large, and in engines that place emphasis on performance in the low-to-medium speed range, the event angle is conversely reduced and the timing at which the intake valve closes is brought forward.

However, when the event angle of the intake valve is increased, the torque in the high speed range increases as shown by the broken line in Figure 8, but conversely, the intake efficiency decreases in the low and medium speed range, resulting in a torque shortage. It ends up. Furthermore, when the event angle is made smaller, the torque increases in the low and medium speed range, as shown by the solid line in Figure 8, but there is a problem in that the torque rapidly decreases in the high speed range. Performance in either the high-speed rotation range or the high-speed rotation range was sacrificed.

For this reason, recently, the intake camshaft is rotated by a certain angle relative to the intake side cam pulley connected to the intake camshaft, thereby creating a phase difference in the intake cam. A control device has been developed that delays the timing at which the valve closes and advances the timing at which the intake valve closes in the low-to-medium rotation range.

[Problems to be Solved by the Invention] However, this conventional control device uses hydraulic pressure to move the helical gear that connects the intake camshaft and the camboo in the axial direction, and also controls the hydraulic pressure according to the engine speed and engine load. Since the engine is electronically controlled by a microcomputer, it requires not only special hydraulic equipment and a microcomputer, but also various sensors to detect the operating status of the engine. Therefore, the entire device becomes complicated and fire-prone, which poses a problem in terms of cost.

The present invention was made based on these circumstances, and
An object of the present invention is to provide a valve timing control device for a four-stroke engine capable of changing the opening/closing timing of an intake valve with a simple configuration.

[Means for Solving the Problem] Therefore, in the present invention, an intake camshaft that opens and closes the intake valve and an exhaust camshaft that opens and closes the exhaust valve are provided separately, and a crankshaft is provided between these camshafts and the crankshaft. In a four-cycle engine that has a transmission means for transmitting the rotation of the shaft to the camshaft, the transmission means includes a toothed wheel on the intake camshaft that is rotationally driven by power transmission from the crankshaft. The toothed wheel is provided to be rotatable relative to the intake camshaft at a fixed angle, and between the toothed wheel and the intake camshaft, the toothed wheel is connected when the rotational speed of the crankshaft reaches a preset value. The present invention is characterized in that an elastic body is interposed, which has a biasing force larger than the driving force applied to the intake camshaft and positions the toothed wheel in the periaxial direction with respect to the intake camshaft.

[Function] According to this configuration, the elastic body that positions the intake camshaft and the toothed wheel does not support the toothed wheel until the rotational speed of the crankshaft, that is, the engine rotational speed reaches a preset value. Since the intake camshaft and the toothed wheel have an urging force that exceeds the driving force from the crankshaft, relative rotation between the intake camshaft and the toothed wheel is prevented, and the two rotate together.

When the engine speed increases and the engine speed exceeds the set value, the driving force of the toothed wheel overcomes the biasing force of the elastic body, and the elastic body is gradually compressed, causing the intake camshaft to On the other hand, the toothed wheel rotates relatively. For this reason, a phase difference occurs on the intake camshaft, so if the biasing force of the elastic body is set so that the toothed wheel can rotate at the desired rotation speed, the timing at which the intake valve closes can be adjusted according to the engine rotation speed. It can be changed freely and good suction efficiency can be ensured in the entire rotation range.

Moreover, in this case, the opening and closing timing of the intake valve can be changed by using an elastic body to bias a toothed wheel that can rotate at a fixed angle relative to the intake camshaft, so it is possible to change the opening and closing timing of the intake valve, unlike conventional hydraulic systems. Various sensors for detecting the operating condition 62 of the engine, including a microcomputer, are not required at all, and the structure and control can be simplified and provided at low cost.

[Embodiment] A first embodiment of the present invention will be described below based on FIGS. 1 to 4.

FIG. 3 shows, for example, a four-cycle parallel four-cylinder engine for a motorcycle, where the symbol ■ is a cylinder block, 2 is a cylinder head, and 3 is a head cover. The cylinder head 2 is provided with two intake valves 5 and two exhaust valves (not shown) corresponding to each cylinder 4. In the valve operating chamber 6 between the cylinder head 2 and the head cover 3, an intake camshaft 7 for opening and closing the intake valve 5 and an exhaust camshaft 8 for opening and closing the exhaust valve are provided, respectively. Arc-shaped intake cams 9 are formed on the outer periphery of the intake camshaft 7 in correspondence with the intake valves 5, and these intake cams 9 are connected to valve lifters ■0.
The valve stem 5a of the intake valve 5 is in contact with the valve stem 5a of the intake valve 5 via.

Cam sprockets 11 and 12 as toothed wheels are attached to the outer peripheries of the intake camshaft 7 and the exhaust camshaft 8, respectively. A timing chain 15 is mounted between these cam sprockets 11, 12 and a crank sprocket 14 provided on the crankshaft 13, and in the case of this embodiment, these cam sprockets 11, 12, crank sprocket 14 and timing chain 15
constitutes a transmission means for transmitting the rotation of the crankshaft 13 to the camshaft 7.8.

The cam sprocket 11.12 is provided in the middle of each camshaft 7.8, that is, between the second cylinder 4 and the third cylinder 4, but the cam sprocket 11.12 is provided at one end of each camshaft 7.8. It's okay.

By the way, the cam sprocket 11 on the intake camshaft 7 is
It is attached so that it can rotate relative to the intake camshaft 7 by a certain angle depending on the engine speed. The structure of this installation will be explained with reference to FIGS. 1 and 2. The cam sprocket 11 is installed coaxially with the outer periphery of the intake camshaft 7 and rotatable around the axis. One side surface of the intake camshaft 7 is overlapped with a disk-shaped flange portion 20 protruding from the outer periphery of the intake camshaft 7 . Further, a support plate 21 is coaxially attached to the outer periphery of the intake camshaft 7 and is in contact with the other side surface of the cam sprocket 11 . The support plate 21 is biased toward the flange portion 20 by a disc spring 22, and the cam sprocket 11 is slidably inserted and held between the support plate 21 and the flange portion 20.

Openings 23 and 24 are provided in the sliding surfaces of the cam sprocket 11 and the flange portion 20, respectively. These openings 23 and 24 are located at four locations along the circumferential direction of the cam sprocket 11, have a rectangular shape along the rotational direction of the cam sprocket 11, and overlap and communicate with each other. A compression coil spring 26 as an elastic body is accommodated in each of the communicating openings 23,24. Both ends of the compression coil spring 26 are in contact with both ends of the opening 23, 24 along the rotational direction, and bias the cam sprocket 11 and the flange 20 in opposite directions. In this case, the biasing force of the compression coil spring 26 is greater than the driving force applied from the crankshaft to the cam sprocket 11 via the timing chain 15 when the rotational speed of the crankshaft I3 reaches a preset value. It is set.

Further, the opening 24 on the flange portion 20 side is provided with a stopper pin 25 that protrudes along the rotational direction from the opening edge on the rear side in the rotational direction. The stopper pin 25 is inserted into the opening 24 on the cam sprocket II side, and its entire length is formed shorter than the length of the opening 23.24. The base end of the stopper pin 25 receives the biasing force of the compression coil spring 2B and comes into contact with the opening edges of both openings 23 and 24 on the rear side in the rotational direction, and this contact causes the cam sprocket 11 to connect with the intake air. It is positioned with respect to the camshaft 7.

In addition, the protruding tip of the stopper pin 25 and the opening 23.2
A gap Ω is provided between the cam sprocket 11 and the opening edge on the front side in the rotational direction of the cam sprocket 4 to allow relative rotation in the axial direction between the cam sprocket 11 and the intake camshaft 7. The sprocket 11 is rotated in synchronization with the intake camshaft 7 until the number of revolutions of the crankshaft 13 reaches the above set value.

In addition, in FIG. 4, the reference numeral 27 indicates a chain guide, and the reference numeral 28 indicates a chain tensioner.

Next, the operation of the above configuration will be explained.

The compression coil spring 26, which positions the intake camshaft 7 and the cam sprocket 11, prevents the crankshaft from being applied to the cam sprocket 11 until the rotational speed of the crankshaft 13, that is, the engine rotational speed reaches a preset rotational speed. 1
Cam sprocket ■1 with a biasing force greater than the driving force of 3
Since the flange portion 20 and the flange portion 20 are biased in opposite directions, the stopper pin 25 and the opening portions 23 and 24 are maintained in a state of contact. Therefore, even if a driving force is applied to the cam sprocket 11 as the crankshaft 13 rotates, the cam sprocket it will not rotate relative to the intake camshaft 7, and the cam sprocket 11 and the intake camshaft 7 will not rotate. and are rotated together in synchronization.

By the way, the driving force applied to the cam sprocket 11 increases as the rotational speed of the crankshaft 13 increases, so when the engine rotational speed exceeds the above-mentioned set number, the driving force applied to the cam sprocket 11 increases as the rotational speed of the crankshaft 13 increases. You will overcome the forces. Therefore, the compression coil spring 26 is gradually compressed, and the cam sprocket 11 is moved by an angle α corresponding to the gap g between the stopper pin 25 and the opening 23.24 with respect to the flange portion 20, as shown in FIG. rotates relative to each other. Therefore, when a phase difference occurs in the intake cam 9 and the engine speed exceeds the set value, the event angle of the intake cam 9 can be increased by the angle α.

Therefore, by appropriately setting the biasing force of the compression coil spring 2G, the event angle of the intake valve 5, that is, the timing at which the intake valve 5 closes, can be freely changed according to the engine speed, and a good result can be achieved in the entire rotation range. Inhalation efficiency can be ensured.

In the above configuration, the cam sprocket 11, which is rotatable relative to the flange portion 20 of the intake camshaft 7 at a fixed angle, is simply positioned by the compression coil spring 25, and the intake valve 5 is adjusted in accordance with the engine speed. Since the opening/closing timing of the engine can be changed, there is no need for various conventional hydraulic systems, microcomputers to control these hydraulic systems, and various sensors for detecting the operating status of the engine. Therefore, the structure and control can be greatly simplified, which has the advantage that it can be provided at a lower cost.

In the first embodiment described above, the stopper pin and the compression coil spring are incorporated into the same opening, but the present invention is not limited to this, and FIGS. 5 and 6 show a second embodiment of the present invention. Give an example.

That is, a through hole 31 is opened in the cam sprocket 11 and is located between the openings 23.
has an oval shape along the rotational direction of the cam sprocket 11. A disk-shaped stopper piece 32 is accommodated within this through hole 31. The stopper piece 32 is supported on a pivot pin 33 installed between the flange portion 20 and the support plate 21, and this stopper piece 32 receives the biasing force of the compression coil spring 2G to move backward in the rotational direction of the through hole 31. It is in contact with the opening edge on the side. Therefore, a gap g is formed between the stopper piece 32 and the opening edge of the through hole 31 on the forward side in the rotation direction to allow relative rotation between the cam sprocket 11 and the flange portion 20. .

Also in the second embodiment with such a configuration, when the engine speed reaches a certain set value, the compression coil spring 26 is compressed, and the cam sprocket 11 and the flange portion 20 rotate relative to each other by the gap g. The intake cam 9 can be moved to create a phase difference in the intake cam 9.

Further, in each of the above embodiments, the rotation of the crankshaft is transmitted to the camshaft via a timing chain, but instead of this timing chain, a toothed belt or mutually meshing gears may be used. The toothed wheel is not limited to a sprocket, but may also be a toothed pulley or a gear.

[Effects of the Invention] According to the present invention detailed above, the opening/closing timing of the intake valve can be changed by using an elastic body to bias a toothed wheel that can rotate at a fixed angle relative to the intake camshaft. This eliminates the need for various conventional hydraulic devices, microcomputers, and various sensors for detecting the operating status of the engine. Therefore, the structure and control can be simplified, and it can be provided at a lower cost.

[Brief explanation of the drawing]

1 to 4 show a first embodiment of the present invention.
The figure shows a cross-sectional view of the cam sprocket installation, Figure 2 is a cross-sectional view along line 5 and 6 show the second embodiment of the present invention, FIG. 5 is a sectional view showing the installation of the cam sprocket, and FIG. 6 is a sectional view showing the installation of the cam sprocket, and FIG. 7 and 8 show the prior art, FIG. 7 is a characteristic diagram showing the opening/closing timing of intake valves and exhaust valves, and FIG. 8 is a characteristic diagram showing changes in torque with respect to engine speed. It is. 5...Intake valve, 7...Intake camshaft, 8...Exhaust camshaft, 11...Toothed wheel (cam sprocket)
, 14.15... Transmission means (crank brocket, timing chain), 26... Elastic body (compression coil spring).

Claims (1)

[Claims] Transmission means that is provided with separate intake camshafts for opening and closing the intake valves and exhaust camshafts for opening and closing the exhaust valves, and is provided between these camshafts and the crankshaft for transmitting the rotation of the crankshaft to the camshaft. In a four-cycle engine with a 4-cycle engine, the transmission means includes a toothed wheel on the intake camshaft that is rotationally driven by power transmission from the crankshaft, and the toothed wheel is moved relative to the intake camshaft at a certain angle. In addition, between these toothed wheels and the intake camshaft,
Having a biasing force greater than the driving force applied to the toothed wheel when the rotation speed of the crankshaft reaches a preset value,
A valve timing control device for a four-cycle engine, characterized in that an elastic body is interposed to position the toothed wheel in the axial direction with respect to the intake camshaft.