JP3969136B2 - Variable valve timing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve timing device that makes the valve timing of intake and exhaust valves of an internal combustion engine variable by changing the rotational phase of a camshaft with respect to a crankshaft.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there are known variable valve timing devices configured to change the rotational phase of a camshaft with respect to a crankshaft by friction braking of an electromagnetic clutch (electromagnetic brake) (Japanese Patent Laid-Open Nos. 2001-164951 and 10-153104). See the official gazette).
[0003]
The variable valve timing device has a split structure in which a phase can be given between the sprocket for transmitting the rotation of the crankshaft to the camshaft and the camshaft alone. The brake is applied to the drum to delay the rotation of the drum, and the rotation delay is converted into the axial displacement of the spline meshing portion, thereby changing the rotational phase of the cam shaft relative to the crankshaft. ing.
[0004]
[Problems to be solved by the invention]
By the way, the electromagnetic clutch of the conventional variable valve timing device does not work in the direction in which the friction material moves away from the drum when the electromagnetic force is lost when the energization is interrupted, so the frictional resistance is reduced even when the energization is interrupted. This takes time, and there is a problem that it takes extra time to return to the initial position from the state where the rotation of the drum is delayed by friction braking.
[0005]
Further, as described above, since the force does not act in the direction in which the friction material moves away from the drum, the friction material may be in contact with the drum before starting the engine. In this case, no current is applied to the electromagnetic clutch. However, there is a problem that dragging of the friction material occurs as the engine is started, and the rotation delay of the drum (change in valve timing) occurs temporarily.
[0006]
Furthermore, since the friction material does not act in a direction away from the drum, there is a problem that the friction material and the drum may slide when the electromagnetic clutch is turned off, and the deterioration of the friction material may be caused. .
The present invention has been made in view of the above problems, and by making the friction material positively released from the drum when the electromagnetic clutch is OFF, the responsiveness when returning from the state where the rotation is delayed is achieved. It is an object of the present invention to provide a variable valve timing device that can improve, avoid dragging of a drum at the time of engine start, and further improve the deterioration life of a friction material.
[0007]
[Means for Solving the Problems]
Therefore, in the first aspect of the present invention, a permanent magnet that generates a magnetic force that attracts the electromagnetic clutch toward the back side is provided at least in a state where the electromagnetic clutch is de-energized, and the permanent magnet forms a spring . According to the above configuration, when the magnetic force of the permanent magnet acts on the electromagnetic clutch that is de-energized, the friction material is separated from the drum, and the permanent magnet forms a spring so that the electromagnetic clutch hits the permanent magnet. Sometimes buffering.
[0010]
According to a second aspect of the present invention, the permanent magnet is a coil spring wound around a pin that prevents the electromagnetic clutch from rotating with respect to the cover member. According to the above configuration, the electromagnetic clutch is configured to be prevented from rotating by the engagement of the pin with respect to the cover member, and the coil spring wound around the pin is formed of the permanent magnet, and the electromagnetic clutch is disposed on the back surface. When a magnetic force attracting toward the side is generated and the electromagnetic clutch moves toward the back side, the coil spring functions as a cushioning material.
[0011]
According to a third aspect of the present invention, the permanent magnet has a polarity that biases the electromagnetic clutch in the fastening direction when the electromagnetic clutch is energized. According to a fourth aspect of the present invention, the electromagnetic clutch is provided with a permanent magnet that generates a magnetic force that attracts the electromagnetic clutch toward the back side when the electromagnetic clutch is energized, and the permanent magnet is in the energized state of the electromagnetic clutch. The electromagnetic clutch has a polarity for biasing in the fastening direction. According to the above configuration, the magnetic force of the permanent magnet works in the direction to release the electromagnetic clutch when the electromagnetic clutch is de-energized, and the direction of the magnetic pole of the permanent magnet is opposite to the polarity of the electro-magnet of the electromagnetic clutch when the electromagnetic clutch is energized. On the contrary, it works in the direction of fastening the electromagnetic clutch. According to a fifth aspect of the present invention, the permanent magnet according to the fourth aspect has a plate shape that is attached to a cover member that covers the back side of the electromagnetic clutch. According to the said structure, the plate-shaped permanent magnet attached to the cover member attracts the electromagnetic clutch by which electricity supply is interrupted | isolated to the cover member side with the magnetic force.
[0012]
【The invention's effect】
According to the first aspect of the present invention, since the magnetic force for attracting the electromagnetic clutch toward the back side and pulling it away from the drum works at least when the electromagnetic clutch is de-energized, the valve is de-energized from the state where the rotation of the drum is delayed. Responsiveness when returning the timing is improved, and the engine start can be performed in a state where the friction material and the drum are separated from each other, thereby avoiding the occurrence of a temporary deviation of the valve timing at the start, Furthermore, since the friction material does not come into contact with the drum when the electromagnetic clutch is de-energized, there is an effect that the deterioration life of the friction material can be improved, and the permanent magnet for generating the magnetic force is made into a spring shape. Thus, it also functions as a buffer material for the release operation of the electromagnetic clutch, and has the effect of preventing the occurrence of collision noise.
[0014]
According to the second aspect of the invention, by providing the coil spring formed by permanent magnet portions of the locking pin of the electromagnetic clutch, generates a magnetic force to attract toward the electromagnetic clutch on the rear side, and the attracting operation There is an effect that the clutch release member that performs the buffering function can be easily installed.
[0015]
According to the third and fourth aspects of the invention, the magnetic force of the permanent magnet does not hinder the fastening of the electromagnetic clutch, and it is possible to positively release the electromagnetic clutch in the energization cut-off state. effective. According to the fifth aspect of the present invention, by attaching the permanent magnet that generates magnetic force to the cover member in the shape of a plate, there is an effect that it is possible to suppress the length in the cam shaft direction from being increased by the clutch release member.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a system configuration of a variable valve timing device using an electromagnetic clutch (electromagnetic brake) in an embodiment.
In the present embodiment, the variable valve timing of the intake valve is described. However, the variable valve timing of the exhaust valve may be controlled.
[0017]
In the figure, on the end extension line of the intake side camshaft 2 that is rotatably supported with respect to the cylinder head 1, a cylindrical spline shaft 3 is engaged with the engagement pin 4 to prevent rotation. 5 is connected and fixed.
A primary cam sprocket 6a and a secondary cam sprocket 6b are rotatably supported on the shaft periphery of the spline shaft 3.
[0018]
The sprockets 6a and 6b are supported so as to be rotatable relative to the camshaft 2, and the rotation of the crankshaft of the internal combustion engine is transmitted to the primary cam sprocket 6a via a timing chain (primary). The rotation is transmitted to the cam sprocket of the exhaust camshaft via the timing chain (secondary).
[0019]
The rotation of the sprockets 6a and 6b is transmitted to the spline shaft 3 through a transmission mechanism described below.
A cylindrical drum 7 having a flange 7 a is provided coaxially with the camshaft 2, and a torsion coil spring 8 that biases the drum 7 in a direction that delays the rotational phase is interposed between the drum 7 and the sprocket 6 a. It is disguised.
[0020]
A spring case 9 is fixed to the sprocket 6 a, one end portion (right end portion in the drawing) of the torsion coil spring 8 is fixed to the spring case 9, and the other end portion of the torsion coil spring 8 is fixed to the flange 7 a of the drum 7. The drum 7 is biased in a direction in which the rotational phase is delayed with respect to the sprocket 6a.
Further, the gear 3a formed on the outer peripheral surface of the spline shaft 3 and the gear 10a formed on the inner periphery of the cylindrical intermediate gear 10 are meshed by a helical mechanism using a helical gear.
[0021]
On the other hand, a male screw 10b is formed on the outer peripheral surface of the left end portion of the intermediate gear 10 and a female screw 7c is formed on the inner peripheral surface of the drum 7, each of which is engaged by a screw action.
A gear 10c formed on the outer peripheral surface of the right end portion of the intermediate gear 10 and a gear 9b formed on the inner peripheral surface of the spring case 9 are engaged with each other by a helical mechanism using a helical gear.
[0022]
The drum bearing member 11 is interposed between the outer peripheral surface of the spline shaft 3 and the inner peripheral surface of the drum 7 and supports the relative rotation of both.
The outer peripheral portion of the drum bearing member 11 is engaged with an annular claw member 12 fitted to the drum 7 and a nut 13 screwed to the outer peripheral surface of the end portion of the spline shaft 3 to move in the axial direction. Is regulated.
[0023]
Further, an annular electromagnetic clutch (electromagnetic brake) 14 is disposed opposite to the outside (left side in the figure) of the drum 7.
As shown in FIG. 2, the anti-rotation pins 15 protrude from the two positions on the back side of the electromagnetic clutch 14 with the direction parallel to the axis of the cam shaft 2 as the axial direction. The electromagnetic clutch 14 is prevented from rotating by being inserted into a cylindrical hole 16a (see FIG. 3) formed in a concave shape on the inner surface side of the cover member 16 covering the back side of the clutch 14.
[0024]
The electromagnetic clutch 14 is inserted into the hole 16a between the position where the friction material 14a contacts the flange 7a and the position where the back surface 14b contacts the inner surface of the cover member 16. While being maintained, it can be translated along the axial direction of the camshaft 2.
When the electromagnetic clutch 14 is energized, the electromagnetic clutch 14 is attracted to the drum 7 by the generated electromagnetic force, and the flange 7a of the drum 7 is brought into sliding contact with the friction material 14a to be prevented from rotating. Friction braking force works.
[0025]
Further, as a characteristic configuration of the present application, an annular plate-shaped permanent magnet 20 (clutch release member) formed on the inner surface side of the cover member 16 with substantially the same inner and outer diameter as the electromagnetic clutch 14 as shown in FIG. Is mounted to face the back surface of the electromagnetic clutch 14.
The permanent magnet 20 has magnetic poles in the left-right direction in FIG. 1, and the magnetic poles are opposite to the magnetic poles generated in the electromagnet when the electromagnetic clutch 14 is energized.
[0026]
In FIG. 4, two through holes 20 a are for inserting the anti-rotation pin 15. For example, as shown in FIG. 5, the two through holes 20 a are divided into two at the portion of the anti-rotation pin 15. Two arcuate permanent magnets 20a and 20b may be used in combination.
The basic operation of such a variable valve timing device will be described.
[0027]
Energization of the electromagnetic clutch 14 is controlled by a control unit 19 incorporating a microcomputer.
When the electromagnetic clutch 14 is not energized (control current = 0), the drum 7 is held at the position where the rotational phase is most delayed by the biasing force of the torsion coil spring 8, and at this time, the camshaft 2 is also cranked. The rotation phase is held at a position most retarded with respect to the axis.
[0028]
When the rotational phase of the camshaft 2 is advanced with the most retarded angle position as a reference and the valve timing of the intake valve is advanced by a target angle, the electromagnetic clutch 14 is energized and the friction material 14a is moved to the flange of the drum 7. Friction braking is applied by adsorbing to 7a. As a result, the drum 7 is delayed with respect to the rotation of the sprocket 6 synchronized with the crankshaft. As a result, the intermediate gear 10 meshed with the drum 7 by the male screw 10b and the female screw 7c It moves in the axial direction (for example, the right direction in FIG. 1).
[0029]
When the intermediate gear 10 moves in the axial direction by the helical mechanism on the inner and outer peripheral surfaces of the intermediate gear 10, the cam shaft 2 rotates relative to the cam sprocket 6a in the advance direction of the cam phase. In contrast, the rotational phase of the camshaft 1 changes in the advance direction (the valve timing of the intake valve changes toward the advance side).
As the current value to the electromagnetic clutch 14 is increased and the braking force (sliding friction) with respect to the urging force of the torsion coil spring 8 is increased, the rotational phase of the camshaft 2 is changed to the more advanced side. .
[0030]
As described above, the rotational phase of the camshaft 2 is advanced with respect to the sprocket 6 (crankshaft) according to the rotational delay amount of the drum 7 determined according to the braking force of the electromagnetic clutch 14, and the electromagnetic clutch The braking force by 14 is controlled by, for example, duty-controlling the control current supplied to the electromagnetic clutch 14, whereby the rotational phase of the camshaft 2 can be continuously changed.
[0031]
In the energization control of the electromagnetic clutch 14, the permanent magnet 20 acts as follows.
When energization of the electromagnetic clutch 14 is interrupted, a magnetic body (such as an iron core) constituting the electromagnetic clutch 14 is attracted to the permanent magnet 20 side by the magnetic force of the permanent magnet 20, so that the electromagnetic clutch 14 moves to the back side. The friction material 14a of the electromagnetic clutch 14 and the drum 7 are pulled apart.
[0032]
Accordingly, when the engine is stopped, the friction material 14a of the electromagnetic clutch 14 and the drum 7 are held away from each other, and the drum 7 is dragged at the start, and the rotational phase of the camshaft 2 is temporarily advanced. There is no end.
Further, during the engine operation, the friction material 14a of the electromagnetic clutch 14 and the drum 7 are held in a state where the energization is cut off, so that the progress of deterioration of the friction material 14a can be suppressed, and further, the energization is cut off. On the other hand, the drum 7 returns to the side urged by the torsion coil spring 8 with good response.
[0033]
Further, when the electromagnetic clutch 14 is energized, the magnetic poles of the electromagnet of the electromagnetic clutch 14 and the magnetic poles of the permanent magnet 20 are reversed, and a repulsive force is generated between the electromagnetic clutch 14 and the permanent magnet 20. Since the electromagnetic clutch 14 is urged toward the drum 7 (in the fastening direction) contrary to the time of disconnection, when the electromagnetic clutch 14 is energized and attracted to the drum 7, the magnetic force of the permanent magnet 20 is increased. Without obstructing, an increase in the size of the electromagnetic clutch 14 and an increase in power consumption can be avoided.
[0034]
In the above embodiment, the plate-shaped permanent magnet 20 generates a magnetic force that attracts the electromagnetic clutch 14 toward the back side. However, by using a spring formed by the permanent magnet, the electromagnetic clutch 14 is moved to the back side. It is possible to generate a magnetic force attracting toward the surface and to perform a buffering action.
FIG. 6 shows a second embodiment using a spring (clutch release member) formed by a permanent magnet.
[0035]
FIG. 6 is an enlarged view of a portion of the detent pin 15, and the coil spring 22 wound around the detent pin 15 is formed of a permanent magnet and one end of the cover member 16. It is fixed to the inner surface, and the other end is a free end.
According to the above configuration, the electromagnetic clutch 14 is attracted to the coil spring 22 side by the magnetic force of the coil spring 22 while the energization of the electromagnetic clutch 14 is interrupted by the magnetic force of the coil spring 22, and the electromagnetic clutch 14 is removed from the drum 7. When the back side of the electromagnetic clutch 14 comes into contact with the tip of the coil spring 22, the coil spring 22 contracts and exhibits a buffering action. Can be avoided.
[0036]
In the above description, the spring shape is a coil, but other shape springs such as a leaf spring, a U-shaped spring, and a conical coil spring may be formed of a permanent magnet .
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a variable valve timing device according to an embodiment.
FIG. 2 is a partially enlarged view showing an electromagnetic clutch detent mechanism in the embodiment.
FIG. 3 is a plan view showing a cover member of the variable valve timing device according to the embodiment.
FIG. 4 is a view showing a plate-like permanent magnet as a clutch release member in the embodiment.
FIG. 5 is a view showing another shape of the plate-like permanent magnet.
FIG. 6 is a partially enlarged sectional view showing a second embodiment using a coil spring formed of a permanent magnet as a clutch release member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cylinder head 2 ... Cam shaft 3 ... Spline shaft 6a, 6b ... Cam sprocket 7 ... Drum 8 ... Torsion coil spring 9 ... Spring case 10 ... Intermediate gear 14 ... Electromagnetic clutch 16 ... Cover member 19 ... Control unit 20 ... Permanent magnet 22 ... Coil spring

Claims (5)

In a variable valve timing device that changes a rotational phase of a camshaft relative to a crankshaft by friction braking of an electromagnetic clutch,
A variable valve timing apparatus , wherein a permanent magnet is provided that generates a magnetic force that attracts the electromagnetic clutch toward the back side at least when the electromagnetic clutch is de-energized, and the permanent magnet forms a spring . The permanent magnet is, the variable valve timing apparatus according to claim 1, wherein the relative said cover member is a coil spring wound around the pin to the detent of the electromagnetic clutch. The permanent magnet is in the energized state of the electromagnetic clutch, the variable valve timing apparatus according to claim 1 or 2, wherein the having polarity for urging the electromagnetic clutch to the fastening direction. In a variable valve timing device that changes a rotational phase of a camshaft relative to a crankshaft by friction braking of an electromagnetic clutch,
With energization cut-off state of the electromagnetic clutch, provided with a permanent magnet for generating a magnetic force to attract toward the electromagnetic clutch on the rear side, the permanent magnet is in the energized state of the electromagnetic clutch, the electromagnetic clutch engagement direction A variable valve timing device having a positive polarity . 5. The variable valve timing device according to claim 4 , wherein the permanent magnet has a plate shape attached to a cover member that covers a back side of the electromagnetic clutch.

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