JPH07224615A - Variable valve timing mechanism - Google Patents

Abstract

PURPOSE:To control generation of noises such as back lash noises in a rotation transmission member and a hydraulic control device inserted between two helical splines by relatively controlling the hydraulic pressure to be supplied to two hydraulic chambers correspondingly to fluctuation of cam torque to be applied to a cam shaft. CONSTITUTION:A control unit ECU 19 relatively controls hydraulic pressure to be supplied to hydraulic chambers 11, 14 of a hydraulic cylinder 4a through a hydraulic control valve 18 correspondingly to fluctuation of cam torque to be applied to a cam shaft 2. When an oil amount in the advance-side hydraulic chamber 11 is increased by the operation of the hydraulic control valve 18 and the hydraulic pressure is increased, a piston 12 is moved clockwise in respect to a housing 4 for advancing because a cylindrical part 12a of the piston 12 is meshed with the housing 4 at helical splines 12b, 4b. On the other hand, when the oil is supplied to the hydraulic chamber 14, the piston 12 is moved counterclockwise and a valve timing of the cam shaft 2 is delayed. Generation of collision noises is thus prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing mechanism for changing the opening / closing timing of valves such as intake valves and exhaust valves used in internal combustion engines.

[0002]

2. Description of the Related Art As disclosed in, for example, Japanese Patent Application Laid-Open No. 3-117604, in an internal combustion engine, power such as a timing belt from a crankshaft is mounted on a shaft of a camshaft that drives an intake valve and an exhaust valve to open and close. The timing pulley, which is rotatably driven by the transmission means, is supported so as to be rotatable relative to each other, and the camshaft side member and the timing pulley side member facing each other in an internal-external relationship and forming an annular gap therebetween are opposed to each other. In each of them, a helical spline having an inclination angle (twisting angle) opposite to each other is formed, and a helical spline that is inserted into a gap between the opposing surfaces and meshes with the helical splines is provided on the inner surface and the outer surface, This piston is controlled in the hydraulic cylinder by balancing the control oil pressure before and after the piston. By moving the shaft in the front-rear direction on the axis, the relative phase of the camshaft with respect to the timing pulley is changed steplessly, and the opening / closing timing of the intake valve and exhaust valve used in the internal combustion engine is changed during operation of the engine. There is known a variable valve timing mechanism which can be freely changed.

[0003]

Generally, since the magnitude of the reaction force generated when the cam provided on the camshaft of the internal combustion engine drives the valve varies, the torque value of the camshaft also varies finely. In the variable valve timing mechanism of the above-described type, the fluctuating torque is transmitted from the timing pulley to the camshaft through the meshing surfaces of the four helical splines with the piston in the hydraulic cylinder as a foothold. The magnitude of the reaction force in the axial direction generated in the portion that supports the hydraulic pressure is also subject to small fluctuations.

Further, since some backlash (play gap) is inevitably present between the helical splines formed on the inner and outer surfaces of the piston and the surface of the opposing helical spline that meshes with them. Due to the overlapping of these causes, when the engine is rotating at high speed,
Repeated collisions and separations between the meshing teeth of the helical splines may cause noise called backlash noise (or rattling noise, tapping noise).

Since the above-mentioned piston is stationary at an arbitrary position in the hydraulic cylinder due to the balance of the control oil pressure before and after the piston, it is difficult to completely maintain that position against a large external force. Therefore, it is conceivable to provide some braking means between the hydraulic cylinder and the piston to add resistance (braking force) to the movement of the piston. When the control oil pressure is changed during low-speed engine rotation, the piston does not immediately follow due to the large braking force being applied, so move the piston due to the difference in oil pressure. The piston starts to move only when the applied force exceeds the applied braking force, so that the responsiveness of the variable valve timing mechanism is reduced accordingly.

The present invention, by improving the above-mentioned prior art, has a problem of occurrence of backlash noise in a variable valve timing mechanism having a helical spline operated by a piston of a hydraulic cylinder, and a problem thereof. At the same time, another problem of deterioration of responsiveness that accompanies the measure of possible uniform increase of braking force is solved, and the control responsiveness is not sacrificed under various operating conditions of the internal combustion engine. SUMMARY OF THE INVENTION It is an object of the invention to provide a variable valve timing mechanism that can suppress noise such as rush noise, has a simple structure, and does not increase the cost.

[0007]

In order to solve the above-mentioned problems, the present invention provides a camshaft having a cam for opening and closing a valve and a rotatably supported on the camshaft. A rotary drive member, a hydraulic cylinder integrated with the rotary drive member, a piston inserted in the hydraulic cylinder and slidable in the axial direction on the camshaft, and on the hydraulic cylinder side. A helical spline formed, a helical spline formed on the camshaft side, and a helical spline that is movable in the axial direction together with the piston and that meshes with the two helical splines simultaneously are provided on both the outer surface and the inner surface. And a rotation transmission member inserted between the two helical splines and the piston in the hydraulic cylinder. A hydraulic control device that selectively supplies control hydraulic pressure to two hydraulic chambers that are partitioned and formed by the control device, and the control device responds to fluctuations in cam torque acting on the camshaft. Provided is a variable valve timing mechanism, which is configured to relatively control a hydraulic pressure supplied to the valve.

[0008]

The basic operation of the variable valve timing mechanism is the same as the conventional one. In the variable valve timing mechanism of the present invention, the controller relatively increases or decreases the hydraulic pressure supplied to the two hydraulic chambers of the hydraulic cylinder by the hydraulic control valve in response to the fluctuation of the cam torque acting on the camshaft. Therefore, in the meshing portion between the helical spline formed on the rotation transmitting member and the helical spline of the other side, at the moment when the teeth of the meshing portion are separated by the amount of backlash due to the fluctuation of the cam torque, A hydraulic force applies an axial force to push one against the other. As a result, the teeth of the meshing portion are not separated from each other, and it is possible to prevent the backlash noise generated when the separated teeth collide with each other.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 conceptually shows a part of an essential part corresponding to the main feature of the present invention in an embodiment, and FIG. 2 includes the essential part shown in FIG. 1 shows an overall configuration of a variable valve timing mechanism as an embodiment of the present invention, which is similar to a conventional variable valve timing mechanism. FIG. 3 is a cross-sectional view for explaining the installation state of a cam angle sensor, which is another main part corresponding to the features of the present invention, FIG. 4 is a schematic view for explaining the problems of the prior art, and FIG. Many diagrams for explaining the operation of the embodiment are shown on a common time axis, and FIG. 6 is a schematic diagram showing the effect of the embodiment by the same method as in FIG.

In FIG. 2, reference numeral 1 denotes a part of a cylinder head of an engine, and a cylinder around the end of a camshaft 2 which is supported inside thereof is a center of a timing pulley 3 so as to be relatively rotatable. The shaped hub portion 3a is loosely fitted. Reference numeral 4 denotes a deep dish-shaped housing which accommodates an actuator portion of the variable valve timing mechanism therein, and a flange portion around the housing is screwed to a disc portion 3b of the timing pulley 3 by several bolts 5. ing. Therefore, the housing 4 can also rotate integrally with the timing pulley 3 along the axis of the camshaft 2. For convenience of assembly, maintenance and inspection, repair, etc., a cap 6 separate from the housing 4 for closing the same is screwed into the central opening of the bottom of the housing 4 which is the left end in FIG. ing.

A gear plate 7 shaped like a gear is integrally attached to the end of the camshaft 2 by a head bolt 8, and the relative position of the gear plate 7 with respect to the camshaft 2 in the rotational direction. Are securely fixed by the positioning pins 9. Further, by fixing the gear plate 7 to the end portion of the camshaft 2, the hub portion 3a of the timing pulley 3 is restrained and the axial movement of the timing pulley 3 with respect to the camshaft 2 is also prevented. However, as described above, the timing pulley 3 is rotatable relative to the cam shaft 2.

The camshaft 2 and the head bolt 8 are provided with hydraulic passages 2a and 8a which communicate with each other so as to penetrate through the respective central portions thereof.
Forming a hydraulic passage. First hydraulic passages 2a and 8
The right end of a is closed by the ball 10, but the left end is open to a space 11 in the housing 4 (this space serves as a “advance-side hydraulic chamber” described later).

The timing pulley 3 has a piston 12 which is substantially disc-shaped and has a cylindrical portion integrally formed on its left side surface.
The cylindrical surface of the hydraulic cylinder 4a is loosely fitted on the cylindrical hub portion 3a at the center of the piston so as to be relatively rotatable and axially slidable, and the outer peripheral portion of the piston 12 is formed on the inner surface of the large diameter portion of the housing 4. Is oil-tightly slidingly fitted. A seal ring 17 is inserted in the annular groove of the outer peripheral portion of the piston 12 in order to improve the sealing performance. In this way, the internal space of the housing 4 has two parts, that is, the hydraulic chamber 11 on the advance side which is the left side of the disk part of the piston 12 in FIG. 2 and the hydraulic chamber 14 on the retard side which is the right side of the disk part. Is divided into

Helical splines 12b and 12c are formed on a part of the outer surface and the inner surface of the cylindrical portion 12a of the piston 12 serving as the "rotation transmitting member", and each of them has a large number of teeth inclined with respect to the axial direction. However, the teeth of the helical spline 12b and the teeth of the helical spline 12c are inclined in opposite directions. In the illustrated embodiment, the helical spline 12b has a right-hand thread and the helical spline 12c has a left-hand thread. As described above, the helical splines 12b and 12c have opposite inclinations, and they take positive and negative values in the inclination angle with respect to the axial direction of the camshaft 2, that is, in the twist angle, but either of the helical splines 12b or 12c. Since the same operation is performed even when the tooth trace is in the axial direction, the term "helical spline" is simply used in the present invention, but the inclination angle of either one of the helical splines is 0.
Can take the value of.

The helical spline 12b formed on the outer surface of the cylindrical portion 12a of the piston 12 meshes with the helical spline 4b formed on the inner surface of the small diameter portion of the housing 4, and at the same time, the helical spline formed on the inner surface of the cylindrical portion 12a. 12c meshes with a helical spline 7a formed on the outer peripheral surface of the gear plate 7. Therefore, the helical spline 4b on the inner surface of the housing 4 has a right-hand thread inclination angle according to the inclination of the tooth trace of the helical spline 12b of the piston 12, and the helical spline 7a on the outer surface of the gear plate 7 is the helical spline 12c. It has a left-hand thread inclination angle according to the inclination of the tooth trace.

A hydraulic chamber 11 on the advance side, which is a space on the left side of the piston 12 in the housing 4, has a camshaft 2
And the first hydraulic passages 2a and 8a formed in the central portion of the head bolt 8, the hole 2b of the camshaft 2, the annular groove 2
c and the first hydraulic passage 1a formed in the cylinder head 1 of the engine, the hydraulic pressure control valve 18 communicates with the first output opening 18a.

Further, the piston 1 in the housing 4
The hydraulic chamber 14 on the retarded angle side, which is the space on the right side of 2, has a hole 3c in the hub portion 3a of the timing pulley 3 and an annular groove 2d formed in a part of the outer periphery of the camshaft 2 in accordance therewith.
And a second hydraulic passage 2f axially formed at a position deviated from the center of the camshaft 2 through the hole 2e, and the second hydraulic passage 2f is further connected to the hole 2g of the camshaft 2. The second output opening 18b of the hydraulic control valve 18 communicates with the second hydraulic passage 1b formed in the cylinder head 1 of the engine through the annular groove 2h.

The hydraulic control valve 18 is generally called a spool valve because it has a spool 18c, and the structure of the hydraulic control valve 18 is well known, so a detailed description thereof will be omitted. Driven solenoid 18
d is a plurality of units formed on the spool 18c as a result of receiving a dither control signal supplied from a well-known electronic control unit (ECU) 19, which is a control unit of the engine, and causing the spool 18c to reciprocate in the axial direction. The land portion is the first output opening portion 18a and the second output opening portion 18
Open and close b for a short time. Then, by changing the ratio of the total time during which the ECU 19 opens the output openings 18a and 18b, the oil pressurized and supplied by the oil pump 20, that is, the lubricating oil of the engine,
It can be distributed in an arbitrary ratio and discharged to the output openings 18a and 18b.

As described above, only one of the output openings 18a or 18b of the hydraulic control valve 18 communicates with the oil pump 20 for a short time, and the hydraulic chamber 11 on the advance side or the retarded side is delayed via the hydraulic passage. Oil is supplied to one of the hydraulic chambers 14 on the corner side, and by repeating this, an arbitrary amount of pressurized oil is supplied to the hydraulic chambers 11 or 14. At the same time as the oil is supplied to one hydraulic chamber, the same amount of oil is supplied from the other hydraulic chamber to the hydraulic control valve 18.
Through the drain passage 21 to the oil pan 22 of the engine. Therefore, the piston 12 is at an intermediate position where the axial forces generated by the control hydraulic pressures of the two hydraulic chambers 11 and 14 become equal, or at the movable range. It will move axially to the end. In the case of the structure shown in the figure, the control hydraulic pressures of the two hydraulic chambers 11 and 14 are the same value in the state where the axial force in the left-right direction is balanced and the piston 12 is stopped at the intermediate position.

When the piston 12 stops at any intermediate position within the movable range, the stop position is determined by the amount of oil remaining in the two hydraulic chambers 11 and 14, respectively. Therefore, by changing the content of the dither control signal generated by the ECU 19, each hydraulic chamber 11, 1
4 can be adjusted by finely adjusting the amount of oil supplied to piston 4.
It becomes possible to freely adjust the stop position of steplessly. Thereby, the opening / closing timing of the intake valve and the exhaust valve of the internal combustion engine can be smoothly changed.

In FIG. 2, 23 is a crankshaft,
Reference numeral 24 is a crank side timing pulley attached to the crankshaft 23, and 25 is a timing pulley 2
4 is a timing belt wound around the timing pulley 3; 26 is a crank angle sensor for detecting the rotation angle of the crankshaft 23; 27 is the camshaft 2;
2 shows a cam angle sensor for detecting the rotation angle of the. The sensors 26 and 27 are specifically magnetic pickups, and each time a protrusion of a rotating member such as a gear attached to the crankshaft 23 or the camshaft 2 generates an electric pulse signal. Therefore, the number is calculated by the ECU 19
By counting at, the rotation angle of each axis can be detected.

Of the configurations of the embodiments described above, most of the configuration except the internal configuration of the ECU 19 and the configuration of the installation position of the cam angle sensor 27, which will be described in detail later, is almost the same as that of the conventional variable valve timing mechanism. It is the same.
In such a variable valve timing mechanism, the rotation of half the rotational speed is transmitted from the crankshaft 23 to the driven side timing pulley 3 by the driving side timing pulley 24 and the timing belt 25, and the rotation is transmitted to the housing. From the helical spline 4b of 4 through the helical splines 12b and 12c of the piston 12,
The rotation is transmitted to the gear plate 7 having the helical spline 7a, and its rotation is transmitted to the cam shaft 2 from the positioning pin 9 to drive the cam 28 as shown in FIG. Thereby valves 29 such as intake and exhaust valves
Opens and closes the intake or exhaust port 30.

In FIG. 3, 31 is a valve lifter and 32 is a valve lifter.
Is a valve guide, 33 is a valve spring for urging the valve 29 in the closing direction of the intake or exhaust port 30, 3
Reference numeral 4 indicates a retainer. The camshaft 2 is provided with a protrusion 35 made of a magnetic material. Protrusion 3 made of magnetic material
When 5 passes just before the cam angle sensor 27, which is a magnetic pickup, the value of the electric signal output by the cam angle sensor 27 changes from positive to negative. The position of the shaft 2 in the rotation direction (cam phase) can be detected.

The relative phase relationship between the timing pulley 3 and the cam shaft 2 can be freely changed by the action of the two pairs of helical splines meshing with each other by moving the piston 12 in the axial direction. As described above, the axial position of the piston 12 controls the amount of oil supplied to the hydraulic chamber 11 on the advance side and the hydraulic chamber 14 on the retard side by the hydraulic control valve 18 operated by a command from the ECU 19. It depends on what you do. The ECU 19 receives the signals generated by the cam angle sensor 27, the crank angle sensor 26, and the like to calculate the cam phase and the rotation speed, and compares them with map data of the optimum cam phase for the operating conditions of the internal combustion engine. A dither control signal is generated to reduce the difference between the actual cam phase and the map data value, and the current supplied to the solenoid 18d of the hydraulic control valve 18 is interrupted.

When the amount of oil in the hydraulic chamber 11 on the advance side increases and the control hydraulic pressure rises due to the action of the hydraulic control valve 18, the piston 12 is pushed to the right in FIG.
Since the cylindrical portion 12a of the piston 12 and the housing 4 are engaged with each other by the right-handed helical splines 12b and 4b, the piston 12 is rotated clockwise with respect to the housing 4 as viewed from the left side of FIG. Also,
Piston 12 and gear plate 7 are helical splines 1
Since they are meshed with each other by 2c and 7a, the gear plate 7 is rotated clockwise with respect to the piston 12 together with the cam shaft 2 by the rightward movement of the piston 12 as described above. In this way, the camshaft 2
The timing of the valve driven by the piston 12
Will be advanced by the amount moved in the axial direction.

On the contrary, when the spool 18c of the hydraulic control valve 18 is moved by the control signal of the ECU 19 and the oil is supplied to the hydraulic chamber 14 on the retard side, the piston 12 is moved leftward and the camshaft is moved. The timing of the valve driven by 2 will be retarded. In this way, the timing pulley 3, and thus the crankshaft 2
The phase of the camshaft 2 with respect to 3 is adjusted steplessly. Also in the illustrated embodiment, the basic operation as described above is the same as that of the conventional variable valve timing mechanism.

In the case of an internal combustion engine, the cam nose of the cam 28 reciprocates the valve 29 against the urging force of the valve spring 33 to open and close the intake or exhaust port 30, so that the sixth cylinder shown in FIG. The cam nose 28
In the state where the cam nose compresses the valve spring 33 to increase the opening degree of the valve 29 as in -6, a reverse torque due to the valve spring 33 acts on the camshaft 2. For convenience, this is called positive torque. On the contrary, when the cam nose is closing the valve 29 like the cam nose 28-3 of the third cylinder shown in FIG. 3, the torque by the valve spring 33 acts in the same direction as the rotation direction of the camshaft 2. . This is called negative torque. in this way,
Since the cam noses of a large number of cams 28 provided on the camshaft 2 are pushed by the valve spring 33, the torque acting on the camshaft 2 periodically fluctuates such that positive torque and negative torque are repeatedly reversed. It will be.

The camshaft 2 illustrated in FIG. 3 is used for an in-line 6-cylinder engine, and the cam nose 2 of the 3rd cylinder is used.
It has cam noses 28-6 of 8-3 and 6th cylinder, and they rotate in the direction of the arrow. In the case of FIG. 3, there is a time when the valve 29 of the third cylinder and the sixth cylinder have the same valve lift (opening degree) and simultaneously contact the top surface 31a of the corresponding valve lifter 31. . That is, the cam nose 28-3, which is about to separate from the top surface 31a of the valve lifter 31, makes contact with the valve 29 of the third cylinder whose valve lift is decreasing and the top surface 31a of another valve lifter 31 while pushing it down. There is a timing as shown in FIG. 3 in which the valve lift of the sixth cylinder 29, whose valve lift is increasing due to a certain cam nose 28-6, becomes the same value as the valve lift.

In the state shown in FIG. 3, the magnitude of the positive torque acting on the camshaft 2 by the cam nose 28-6 of the sixth cylinder and the negative torque acting on the camshaft 2 by the cam nose 28-3 of the third cylinder. Since the magnitudes have the same absolute value and their signs are opposite, they cancel each other out. Therefore, the torque of the valve spring 33 acting on the camshaft 2 is a negative torque immediately before the state of FIG. 3 is reached, and the torque of the camshaft 2 immediately after the state of FIG. 3 is a positive torque.

Therefore, by determining the relative positions of the cam angle sensor 27 and the projection 35 as described above, the third cylinder and the sixth cylinder in which the cam 28 is in contact with the top surface 31a of the valve lifter 31 at that time. When the total torque of the two valve springs 33 of the valve 29 of FIG.
It is set so that the output signal of the cam angle sensor 27 is inverted from a positive value to a negative value across just before 7. In this way, it is possible to detect the timing at which the torque due to the valve spring 33 acting on the camshaft 2 is reversed.

Of the internal configuration of the ECU 19 in the illustrated embodiment, the control circuit portion for the actuator for operating the variable valve timing mechanism is one of the features of the present invention, as shown in FIG. Correspondingly, in addition to the dither control circuit 36 provided conventionally, an AND gate 37, a comparator 38, etc. are added. In FIG. 1, 39 is a power source for generating a reference voltage and supplying a current to the solenoid 18d of the hydraulic control valve 18, 40 is a variable resistor for adjusting the height of the reference voltage, and 41 is an AND gate 37. It shows a transistor that conducts when the output voltage goes high.

In the ECU 19 having the above-mentioned structure,
The output signal of the cam angle sensor 27 that detects the passage of the projection 35 provided on the cam shaft 2 is first input to the comparator 38. When the output voltage of the cam angle sensor 27 reaches a predetermined positive high level value, the comparator 38 outputs a high level voltage. Only when both the output of the comparator 38 and the output of the dither control circuit 36 (dither control signal) become high level, the AND gate 37 opens and the transistor 41 becomes conductive, and the solenoid 18d of the hydraulic control valve 18 is intermittently connected. An electric current is applied, whereby the spool 18c reciprocates to open and close the first output opening 18a and the second output opening 18b, and the oil pump 20
The oil pressurized by the two hydraulic chambers 11 and 14
The piston 12 is moved in the axial direction to change the valve timing for opening and closing the valve 29.

FIG. 4 schematically shows the positions of the four helical splines when the camshaft 2 receives a negative torque and when it receives a positive torque. In FIG. 4, the upper side is defined as the front side and the lower side is defined as the rear side (the same applies to FIG. 6 described later). (A) and (b) show the state where the negative torque by the valve spring 33 acts on the camshaft 2, (a) shows the relationship between the helical spline 4b of the housing 4 and the helical spline 12b of the piston 12, (B) shows the relationship between the helical spline 12 c of the piston 12 and the helical spline 7 a of the gear plate 7. When a negative torque acts on the camshaft 2 in this way, the rotational direction of the housing 4, and hence the timing pulley 3, and the torque direction of the gear plate 7 are the same, so that the piston 1
Since the helical splines 4b of the housing 4 and the helical splines 7a of the gear plate 7 are weakly restrained with respect to the two helical splines 12b and 12c, there is necessarily backlash between the teeth of the helical splines. As shown in (a) and (b), there is a moment when the teeth of the helical splines 12b and 12c become floating between the teeth of the helical splines 4b and 7a. In such a state, the teeth of the helical spline are not in contact with each other.

After that, when the camshaft 2 rotates from the state shown in FIG. 3 and the torque by the valve spring 33 acting on the camshaft 2 reverses from negative torque to positive torque, the direction is that of the camshaft 2. Since it is opposite to the rotation direction, in the conventional variable valve timing mechanism, as shown in FIGS. 4 (c) and 4 (d), the tooth surfaces of the helical splines 12b and 12c are respectively opposite helical splines 4b. , 7c collide with the tooth surfaces of the helical splines, because the total torque acting on the camshaft 2 by the bias of the valve spring 33, that is, the cam torque, is reversed from negative torque to positive torque. There was a possibility that a backlash sound, which was a tapping sound, was generated.

In the illustrated embodiment, when the cam torque is negative, that is, when the total torque acting on the camshaft 2 is changed to a negative value by the valve spring 33, the output signal of the cam angle sensor 27 is positive. Since it changes to a value, the output of the comparator 38 becomes high level, and the output of the AND gate 37 becomes the same as the signal of the dither control circuit 36. Therefore, the solenoid 18d of the hydraulic control valve 18 is supplied with a dither control signal from the dither control circuit 36 as in the conventional variable valve timing mechanism, and the piston 12 is hydraulically pushed to the right side in FIG. 2, that is, to the advance side. . This is as shown in (a) and (b) of FIG.
This means that the helical splines 12b and 12c of the piston 12 are pushed downward in the figure. As a result, the helical splines 12b and 12c come into contact with the other helical spline as shown in (c) and (d) of FIG.
The floating state as shown in FIGS. 4A and 4B is resolved.

On the other hand, when the cam torque is positive, that is, when the total torque acting on the camshaft 2 by the valve spring 33 has a positive value, the output signal of the cam angle sensor 27 has a negative value. Therefore, the output signal of the comparator 38 becomes low level, and as a result, the output of the AND gate 37 also becomes low level, and the hydraulic control valve 1
The solenoid 18d of No. 8 is not energized. Therefore,
The piston 12 is pushed by the hydraulic pressure to the retard side, that is, the front side on the left side in FIG.

The direction in which this hydraulic pressure acts is shown in FIG.
4B, when the cam torque is negative, the floating state of the helical splines 12b and 12c of the piston 12 shown in FIGS. 4A and 4B is suppressed, and the cam torque is positive. In this case, since it is a direction to escape from the teeth of the helical splines 4b and 7a of the housing 4 and the gear plate 7 which collide toward the teeth of the helical splines 12b and 12c of the piston 12, the collision of the teeth of each helical spline occurs. It will be weakened and the backlash noise will be reduced.

In order to summarize the operation of the variable valve timing mechanism of the illustrated embodiment as described above, FIG. 5 shows changes in the state of each part. That is, a change in the output signal of the crank angle sensor 26 that monitors the crank angle of the engine is shown in (a), a change in the output signal of the cam angle sensor 27 is shown in (b), and a change in the output signal of the comparator 38 is shown in (a). In (c), the dither control signal which is the output signal of the dither control circuit 36 is shown in (d),
The output signal of the AND gate 37, that is, the transistor 41 is set to (e), the change in hydraulic pressure in the hydraulic chamber 11 on the advance side is set to (f), and the change in cam torque applied to the camshaft 2 by the valve spring 33 is set to (g). ), Respectively, in a state corresponding to each time.

In the illustrated embodiment, the case where the variable valve timing mechanism is applied to the 6-cylinder internal combustion engine has been described.
It goes without saying that the present invention can be applied to engines having other numbers of cylinders. When the present invention is applied to an engine having a smaller number of cylinders than six cylinders, the hydraulic control valve 18 and the like are not required to have a high-speed response, so that the control becomes easier and the cheaper parts are used. Will be possible.

Further, in the illustrated embodiment, the timing of taking the output signal of the comparator 38 is fixed in synchronization with the rotation of the camshaft 2 in order to make the operating principle easy to understand. Due to the influence of friction or the like, the timing at which the cam torque reverses is shifted forward or backward depending on the rotation speed, or the response delay occurs in the hydraulic control valve 18, so that the output signal of the comparator 38 corresponds to the output signal of the cam angle sensor 27. The signal synchronized with the rotation of the camshaft 2 may be shifted. Specifically, for example, the map data of the optimum timing and the duty ratio of the signal for the output of the comparator 38 with respect to the rotation speed is stored in the memory of the ECU 19, and the camshaft 2 is changed according to the change of the rotation speed.
Generate a signal in synchronization with the rotation of.

In the illustrated embodiment, for simplification and easy description, the solenoid 18d of the hydraulic control valve 18 is deenergized when the cam torque has a positive value, but the energization is stopped. Alternatively, the amount of current (electric power) supplied to the solenoid 18d may be changed by switching the duty ratio of dither control.

Further, in the illustrated embodiment, the engine oil (lubricating oil) of the engine is used as the operating oil of the hydraulic control system in the variable valve timing mechanism, so that the oil pump 20 for lubricating oil supply is also used. However, it goes without saying that in the present invention, the hydraulic control system of the variable valve timing mechanism may be separated from the lubricating oil supply system of the engine to form an independent hydraulic system using another hydraulic oil and the oil pump 20. Yes.

The camshaft 2 is driven from the crankshaft 23 via the timing pulley 24 on the crank side, the timing belt 25, and the timing pulley 3. The timing belt 25 is a timing chain. Since it may be present, in that case, the sprocket is used as the one corresponding to the timing pulleys 3 and 24. Further, the timing pulley 3 may be a timing gear. Therefore, the timing pulley 3 should generally be called a "rotational drive member" for the variable valve timing mechanism.

In the above embodiment, the hydraulic pressure synchronized with the change in the torque acting on the camshaft 2 is obtained by the action of the hydraulic control valve. However, in addition to the hydraulic passage for the hydraulic control valve, the rotation of the camshaft is accompanied. By providing a hydraulic passage that opens and closes, the hydraulic pressure synchronized with the torque change may be obtained.

The structure will be described below. In addition to the hydraulic passage of the above embodiment, the camshaft 2 has a hole 2i shown in FIG.
Is provided. Further, the engine head 1 has a hydraulic passage 1c communicating with the oil pump 20 and a drain passage 21.
Is provided with an oil passage 1d. When the torque acting on the camshaft 2 is positive, the hole 2i is closed by the oil passage 1
When the torque is negative, the hole 2i is connected to the hydraulic passage 1
communicate with c.

The operation will be described below. When the torque acting on the camshaft 2 is positive, the oil in the advance-side hydraulic chamber 11 escapes through the oil passage 2a, the hole 2i, and the oil passage 1d, so that the piston 4 moves to the retard side. When the torque acting on the camshaft 2 is negative, the advance side hydraulic chamber 11 communicates with the pump 20 via the oil passage 2a, the hole 2i, and the hydraulic passage 1c, so that the piston 4 moves to the advance side. As described above, also in this case, the same effect as in the above embodiment can be obtained.

[0047]

According to the present invention, in a variable valve timing mechanism having a helical spline operated by a piston of a hydraulic cylinder, the problem of backlash noise is relatively reduced without causing deterioration of responsiveness. It can be solved by simple and low cost means.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a part of an essential part of an embodiment of the present invention.

FIG. 2 is a side view including a partial cross-section showing the entire configuration of a variable valve timing mechanism as an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing another part of the main part of the embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining problems of the conventional technique.

FIG. 5 is a group of diagrams showing a common time axis for explaining the operation of the embodiment of the present invention.

FIG. 6 is a schematic view showing the effect of the embodiment of the present invention.

FIG. 7 is a schematic view showing another embodiment.

[Explanation of symbols]

 2 ... Camshaft 3 ... Timing pulley (rotational drive member) 3a ... Hub part 4 ... Housing 4a ... Hydraulic cylinder 4b ... Helical spline 7 ... Gear plate 7a ... Helical spline 11 ... Advance hydraulic chamber 12 ... Piston 12a ... Cylinder Part (rotation transmitting member) 12b, 12c ... Helical spline 14 ... Hydraulic chamber on retard side 18 ... Hydraulic control valve 18c ... Spool 18d ... Solenoid 19 ... ECU (control device) 20 ... Oil pump 22 ... Oil pan 23 ... Crankshaft 24 ... Crank side timing pulley 25 ... Timing belt 26 ... Crank angle sensor 27 ... Cam angle sensor 28 ... Cam 29 ... Valve (intake valve or exhaust valve of engine) 31 ... Valve lifter 31a ... Top surface 33 ... Valve spring 35 ... Projection 36 ... Dither control circuit 37 ... AND gate 38 ... Comparator

Claims (4)

[Claims] 1. A camshaft having a cam for opening and closing a valve, a rotary drive member rotatably supported on the camshaft, and a hydraulic cylinder integrated with the rotary drive member. A piston that is inserted into the hydraulic cylinder and can slide axially on the camshaft; a helical spline formed on the hydraulic cylinder side; and a helical spline formed on the camshaft side; Is movable in the axial direction together with the piston,
A helical spline that meshes with two helical splines at the same time is provided on both the outer surface and the inner surface, and a rotation transmission member inserted between the two helical splines and two pistons defined by the piston in the hydraulic cylinder. The control device selectively supplies control hydraulic pressure to the hydraulic chambers, and the control device relatively controls the hydraulic pressures to be supplied to the two hydraulic chambers in response to fluctuations in cam torque acting on the camshaft. A variable valve timing mechanism characterized in that it is configured to be controlled to. 2. The variable valve according to claim 1, wherein the hydraulic control device causes the hydraulic pressure to act in the same direction as an axial component of a force received by the rotation transmitting member due to meshing of helical splines. Timing mechanism. 3. The hydraulic control device comprises a hydraulic control valve and a drive control circuit for the hydraulic control valve, and controls the hydraulic pressure by a signal output from a cam angle sensor installed on the camshaft. The variable valve timing mechanism described in Item 1. 4. The variable valve timing mechanism according to claim 1, wherein the action of the hydraulic pressure is obtained by opening and closing an oil passage provided in the cam shaft by rotation of a cam shaft.