JP2957311B2 - Valve timing control device - 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 timing control device for changing and controlling the valve timing of an engine according to the engine speed.

[0002]

2. Description of the Related Art Generally, in an engine, the opening / closing timing of an intake / exhaust valve at which a maximum torque is obtained, that is, the valve timing, differs depending on the number of revolutions of the engine. Various variable valve timing mechanisms have been proposed. As one example, for example, JP-A-63-16
As disclosed in JP-A-2910 and JP-A-2-102305, an advancing plate disposed on the inner periphery of a cam sprocket serving as a driving member that receives power from a crankshaft and rotates. A drum screwed to the inner surface of the plate and rotatably supported on a camshaft, and by moving the advancing plate in the axial direction on the drum, between the crankshaft and the camshaft. It is known that a valve timing is made variable by generating a rotational phase difference.

[0003]

In the conventional variable valve timing mechanism, the time required for the advancing plate to move on the drum to change the valve timing, that is, the operation time required for changing the valve timing, is as follows. Usually, it is set short to reduce the torque shock when the engine is under high load. In this case,
The above-mentioned advancing plate will collide with the stopper which regulates the movement at a high speed, and the advancing plate or the stopper may be fatigue-destructed by repeating this collision.

On the other hand, quick switching of the valve timing is required only when the load is large and the generated torque is high, and it is not necessary to rapidly switch the valve timing when the load is small and the generated torque is small.

The present invention has been made in view of the above circumstances, and an object of the present invention is to appropriately change and control the operation time required for changing the valve timing in accordance with the load of the engine so that the valve timing can be changed. Accordingly, it is an object of the present invention to provide a valve timing control device capable of preventing fatigue destruction of components such as an advancing plate while reducing torque shock.

[0006]

According to a first aspect of the present invention, there is provided a valve timing control apparatus for controlling a valve timing of an engine according to a rotational speed of an engine by using a crankshaft and a camshaft. A variable valve timing mechanism that varies by generating a rotational phase difference between the engine and an engine load detecting unit that detects an engine load;
A control means for receiving a signal from the detection means and controlling the operation time required for changing the valve timing in the variable valve timing mechanism to be shorter as the engine load is larger.

According to a second aspect of the present invention, the variable valve timing mechanism is provided between the crankshaft and the camshaft by a magnetic force generated by an electromagnetic coil. And an electromagnetic type that generates a rotational phase difference, and the control means controls the voltage applied to the electromagnetic coil to increase as the engine load increases.

[0008]

According to the above-mentioned structure, according to the first aspect of the present invention,
Under the control of the control means, the operation time required for changing the valve timing in the variable valve timing mechanism becomes shorter as the engine load becomes larger, so that the valve timing is quickly switched only at a high load where the generated torque is large, and the generated torque is small. When the load is low, the valve timing is switched gently.

[0009]

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

FIG. 1 shows an engine valve timing control apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a camshaft, and 2 denotes a cam sprocket as a rotary drive member arranged concentrically with the camshaft 1. The cam sprocket 2
Although not shown, the rotational driving force from the crankshaft is transmitted via a timing belt, and the rotation of the cam sprocket 2 is transmitted to the camshaft 1 to form an unshown camshaft. , The intake valve and the exhaust valve are each opened and closed at a predetermined timing.

A variable valve timing mechanism 3 varies the valve timing by causing a rotational phase difference between the camshaft 1 and the cam sprocket 2 on the crankshaft side. Reference numeral 3 denotes an advancing plate 4 fitted on the inner periphery of the cam sprocket 2, a drum 5 screwed on the inner periphery of the advancing plate 4, and a spring 6 for urging the drum 5 in a constant rotation direction. And a hub 7 fixed to the camshaft 1. On the outer periphery of the advancing plate 4,
As shown in FIGS. 2 to 4, engagement projections 11 are formed, and an engagement groove (not shown) extending in the axial direction is formed on the inner periphery of the cam sprocket 2. By engaging the engaging protrusions 11 with the mating grooves, the advancing plate 4 is provided so as to be rotatable integrally with the cam sprocket 2 and relatively movable in the axial direction. Also,
Female screws 13 are formed on the inner periphery of the advancing plate 4, and male screws 14 are formed on the outer periphery of the drum 5, and these female screws 13 and male screws 14 are screwed together. The relative rotation of the advancing plate 4 and the drum 5 causes the two plates 4 and 5 to relatively move in the axial direction.

The spring 6 is a spiral spring, the outer peripheral end of which is engaged with the drum 5 and the inner peripheral end of which is engaged with the hub 7, whereby the drum 5 is cam sprocket. 2 is urged in the same direction as the rotation direction. The hub 7 has claw portions 7a,... Extending in the axial direction. The claw portions 7a are formed with inclined cam surfaces 15 extending inclining in the axial direction.
A helical groove 16 inclined with respect to the axial direction is formed on the outer periphery of the advancing plate 4. When the inclined cam surface 15 and the helical groove 16 come into contact with and engage with each other, the advancing plate 4 and the hub 7 are moved with the axial movement of the advancing plate 4.
And rotate relative to each other. The inclined cam surface 1
5 have flat portions 15a, 15 substantially parallel to the axial direction.
b is formed.

Further, the variable valve timing mechanism 3
Is provided with a clutch 20 for causing relative rotation between the advancing plate 4 and the hub 7. Although not shown, the clutch 20 is an electromagnetic type having a solenoid coil, and a direct current 24 is connected to the clutch 20. And the DC power supply 24
Then, the clutch 20 is energized to actuate the clutch 20 and apply a braking force to the drum 5, whereby the drum 5 causes a rotation delay with respect to the advancing plate 4 and rotates relative to the advancing plate 4. Become.

With the above configuration, in the variable valve timing mechanism 3, the rotational driving force of the crankshaft is transmitted from the cam sprocket 2 to the camshaft 1 via the advancing plate 4. In this case, the predetermined engine speed N
At the time of the following engine low speed, the clutch 20 is not operated, and the advancing plate 4 is held at one end of the drum 5, and the side wall of the helical groove 16 of the advancing plate 4 (this side wall is (Which is also a side wall) is engaged by a flat portion 15a on one end side of the inclined cam surface 15. In this state, the valve timing is set to the low-speed valve timing. On the other hand, when the engine speed is higher than the predetermined engine speed N, the clutch 20 is actuated, and the drum 5 rotates relative to the advancing plate 4 on the delay side in the rotation direction against the urging force of the spiral spring 6, The advancing plate 4 is axially moved to and held by the other end of the drum 5, and the side wall of the helical groove 16 of the advancing plate 4 is engaged with a flat portion 15 b on the other end of the inclined cam surface 15. ing. As a result, the camshaft 1 and the cam sprocket 2, that is, the crankshaft, rotate relative to each other to generate a rotational phase difference. The valve timing is switched from the low-speed valve timing, and in this state, the high-speed valve timing is set. When the operation of the clutch 20 is stopped due to a decrease in the engine speed, the drum 5 is rotated relative to the advancing plate 4 in the rotational direction by the urging force of the spiral spring 6, and the advancing The plate 4 is moved to and held at one end, and is switched to the low-speed valve timing. When the advancing plate 4 moves on the drum 5 in the axial direction, the advancing plate 4
Is moved in contact with a peripheral portion of the hub 7 as a stopper (particularly, a portion located between adjacent claw portions 7a, 7a) or a stopper member (not shown) attached to an end of the cam sprocket 2. It is being regulated.

The operation of the clutch 20 (that is, energization from the DC power supply 24 to the clutch 20) is controlled by a control unit 31 as control means. The control unit 31 receives a signal from an engine speed detecting means 32 for detecting an engine speed and a signal from an engine load detecting means 33 for detecting an engine load from an opening degree of a throttle valve.

FIG. 5 shows a control flow for operating the clutch 20 by the control unit 31. In this control flow, after the state, the signals from the various detecting means 32 and 33 are read in step S1, and it is determined in step S2 whether the timing belt needs to be switched. In this determination, a characteristic diagram shown in FIG. 6 stored in the control unit 31 in advance is used. This characteristic diagram shows a change characteristic of the generated torque with respect to the engine speed. The following can be seen from this characteristic diagram.

The low-speed valve timing torque curve groups a 1, a 2, and a 3 are regions where the engine speed is low,
High-speed valve timing torque curve groups b1, b2,
b3 becomes higher in the region where the engine speed is high,
The two torque curve groups intersect at a predetermined engine speed N.

In each of the torque curve groups, the generated torque increases as the air intake amount or the engine load of the engine increases, and the amount of change in the generated torque accompanying a change in the engine speed increases.

The intersection of the two torque curve groups (that is, the predetermined engine speed N) changes so as to increase as the air intake amount of the engine or the engine load decreases (curve L).

The determination in step S2 is, specifically,
Either the low-speed valve timing or the high-speed valve timing is selected according to the current engine speed, and it is determined whether or not switching with the currently set timing belt is required.

If the determination is NO, the process returns to step S1, and if the determination is YES, the operation time required for switching the valve timing is set in step S3 according to the engine load. Further, an applied voltage for that purpose is calculated. In the setting of the operation time, a characteristic diagram shown in FIG. 7 stored in the control unit 31 in advance is used. In this characteristic diagram, the operating time is set to decrease linearly as the engine load increases. In the calculation of the applied voltage, the characteristic diagram shown in FIG. 8 stored in advance in the control unit 31 is used, and the applied voltage corresponding to the previously set operation time is obtained. In this characteristic diagram, the applied voltage increases as the operation time becomes shorter. Therefore,
As shown in FIG. 9, the relationship between the engine load and the applied voltage is such that the applied voltage increases linearly as the engine load increases.

Subsequently, in step S4, a control signal is output to the DC power supply 24 so as to add the applied voltage calculated in step 3 to switch the timing belt, and thereafter, the process returns.

Therefore, in the above control flow, based on the characteristic diagram shown in FIG. 7, the larger the engine load, the shorter the operation time required for changing the valve timing in the variable valve timing mechanism 3, so that the generated torque When the load is large, the valve timing is quickly switched, and the torque shock can be reduced. When the load is small and the load is small, the valve timing can be switched gently.
When it moves upward in the axial direction and its movement is regulated by contact with the peripheral portion of the hub 7 or the stopper member, the contact is made gently, and the advancing plate 4 and the stopper (that is, the peripheral portion of the hub 7 or the stopper It is possible to prevent fatigue destruction of the member), and to enhance the reliability of operation.

[0024]

As described above, according to the valve timing control apparatus of the present invention, the valve timing can be quickly switched only at the time of high engine load with a large generated torque.
Valve timing can be switched gently at low engine load with low generated torque, so torque shock at valve timing switching can be reduced, and fatigue damage of components such as the advancing plate can be prevented, and operation reliability can be improved. It is possible to improve the performance.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an overall configuration of a valve timing control device according to an embodiment of the present invention.

FIG. 2 is a side view showing engagement between an advancing plate and a hub.

FIG. 3 is a side view showing a screw engagement between an advancing plate and a drum.

FIG. 4 is a view as viewed from the direction of the arrow A in FIG. 3;

FIG. 5 is a flowchart showing a control flow for operating a clutch by a control unit.

FIG. 6 is a characteristic diagram showing a relationship between an engine speed and a generated torque.

FIG. 7 is a characteristic diagram showing a relationship between an engine load and an operation time.

FIG. 8 is a characteristic diagram showing a relationship between an applied voltage and an operation time.

FIG. 9 is a characteristic diagram showing a relationship between an engine load and an applied voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Camshaft 3 Variable valve timing mechanism 31 Control unit (control means) 33 Engine load detecting means

Continuation of front page (72) Inventor Toshihiro Okamoto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Corporation (56) References JP-A-63-162910 (JP, A) JP-A-4-136403 ( JP, A) JP-A-4-228844 (JP, A) JP-A-4-234541 (JP, A) JP-A-4-276104 (JP, A) JP-A-4-284138 (JP, A) Hei 1-176725 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 13/02 F01L 1/34 F01L 13/00

Claims (2)

(57) [Claims] 1. A variable valve timing mechanism for varying the valve timing of an engine according to the rotational speed of the engine by generating a rotational phase difference between a crankshaft and a camshaft, and an engine for detecting an engine load. Load detecting means, and a control means for receiving a signal from the detecting means and controlling the operating time required for changing the valve timing in the variable valve timing mechanism as the engine load increases, to control the operation time. Valve timing control device. 2. The variable valve timing mechanism is of an electromagnetic type in which a rotational phase difference is generated between a crankshaft and a camshaft by a magnetic force generated by an electromagnetic coil, and the control means has a large engine load. 2. The valve timing control device according to claim 1, wherein the control is performed to increase the applied voltage to the electromagnetic coil.