JPH07208125A - Variable valve timing mechanism - Google Patents

Abstract

PURPOSE:To show high responsiveness in response to control without being generating back flash noise by providing a recessed part for receiving control oil pressure so as to change abrasion force of a sliding surface according to the magnitude of control oil pressure and deform a seal ring in radial direction, in the seal ring. CONSTITUTION:In a seal ring 17, oil which is pressurized in oil pressure chambers 11, 14 is received in recessed parts 17d, 17e, so that oil pressure which is shown by the arrow is received, the rim 17a of the outside is push-pressed in radial direction outer side, and it is pushed down on the inner surface of a hydraulic cylinder 4a. Simultaneously, the rim 17b of an inner side is push- pressed in radial direction inner side, and it is pushed on the outer circumference of an annular groove 12d. As a result, braking force of axial direction according to the magnitude of control oil pressure acts from the side of the hydraulic cylinder 4a in relation to the piston 12. Vibration of the piston 12 is thus suppressed, and back lash noise is prevented. Also, responsiveness of a variable valve timing is not reduced.

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. Also, since there is inevitably some backlash (playing space) between the helical splines inside and outside the piston and the surface of the opposing helical spline that meshes with them, these causes cause high speed rotation of the engine. At times and the like, collisions and disengagements between mutually meshing helical spline teeth may be repeated, and noise called backlash noise (or rattling noise, tapping noise) may be generated.

As described above, the 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, so that it is difficult to completely maintain the position against a large external force. Therefore, it is conceivable to provide some braking means between the hydraulic cylinder and the piston to apply resistance (braking force) to the movement of the piston, but even if it is good at high speed rotation of the engine with high control oil pressure, the control oil pressure before and after the piston When the control oil pressure is changed during low speed rotation of the engine, the piston does not immediately follow due to the large braking force applied, and the piston tries to move due to the difference in oil pressure. The piston starts to move only when the force exceeds the applied braking force, so that the responsiveness of the variable valve timing mechanism is reduced.

The present invention, by improving the above-mentioned prior art, has a problem of backlash noise generation in a variable valve timing mechanism having a helical spline operated by a piston of a hydraulic cylinder, and a problem thereof. To simultaneously solve another problem of deterioration of responsiveness that accompanies the measure of possible uniform increase of braking force, and to generate noise such as backlash noise 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 which not only has no problem but also always exhibits high responsiveness to control.

[0006]

In order to solve the above-mentioned problems, the present invention is provided between the piston and the hydraulic cylinder only when the control oil pressure is high and the engine is rotating at a high speed above a predetermined value. By increasing the frictional force between the seal ring and the sliding surface of the other side automatically, the braking force acting on the piston is increased, thereby suppressing the backlash noise and rotating at other low speeds. At times such as when the frictional force of the seal ring is automatically reduced, the braking force acting on the piston is reduced, thereby preventing the responsiveness of the variable valve timing mechanism from responding to control. The feature is that it is possible.

As a concrete means thereof, the present invention relates to a cam shaft provided with a cam for opening and closing a valve, a rotary drive member supported on the cam shaft so as to be relatively rotatable, and an integral body with the rotary drive member. Formed on the hydraulic cylinder side, a piston inserted into the hydraulic cylinder and slidable in the axial direction on the camshaft, a seal ring attached to the piston, A helical spline, a helical spline formed on the camshaft side, and an axially movable together with the piston, the helical spline that meshes with the two helical splines simultaneously is provided on both the outer surface and the inner surface, A rotation transmission member inserted between the two helical splines;
The seal ring includes a hydraulic control valve that selectively supplies control hydraulic pressure to two hydraulic chambers defined by the piston in the hydraulic cylinder, and a control device that drives and controls the hydraulic control valve. Receiving the control oil pressure so that it can be deformed in the radial direction by receiving the control oil pressure of at least one of the two oil pressure chambers, and that the frictional force with respect to the sliding surface of the other party changes according to the magnitude of the control oil pressure. A variable valve timing mechanism is provided which comprises at least one recessed portion.

[0008]

The basic operation of the variable valve timing mechanism is the same as that of the prior art, so its explanation is omitted. The invention is characterized in that the seal ring attached to the piston is deformable in the radial direction by receiving the control hydraulic pressure of at least one of the hydraulic chambers, and further has at least one recessed portion for receiving the control hydraulic pressure. Therefore, if the control hydraulic pressure acts on this recess,
A radial force is generated that presses a part of the seal ring against the surface of the piston and presses another part of the seal ring against the sliding surface of the opposite side facing the piston. The magnitude of this radial force is proportional to the magnitude of the control oil pressure, so when the piston moves axially on the camshaft, the control oil pressure is between the seal ring and the mating sliding surface. An axial frictional force having a magnitude corresponding to the magnitude of is generated.

When the internal combustion engine equipped with the variable valve timing mechanism of the present invention rotates at high speed, the control oil pressure becomes high, and the frictional force generated between the seal ring and the sliding surface of the opposite side also becomes large. Since it serves as power to prevent the axial movement of the piston, the backlash noise generated in the backlash clearance of the helical spline is suppressed. On the other hand, since the control oil pressure supplied to the hydraulic chamber of the hydraulic cylinder decreases when the engine rotates at low speed, the frictional force generated between the seal ring and the mating sliding surface also decreases, and the control oil pressure becomes relatively small. Also, the piston can be easily moved in the axial direction, and there is no fear that the responsiveness of the variable valve timing mechanism is deteriorated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall construction of the variable valve timing mechanism of the first embodiment, which is mostly common to the conventional variable valve timing mechanism except for the main part. As will be described later, the essential parts corresponding to the features of the present invention in the first embodiment are shown enlarged in FIG. Also, the second
Regarding the embodiment and the third embodiment, only the respective main parts corresponding to the features of the present invention are shown in FIGS. 3 and 4. Although the overall configurations of the second and third embodiments are not shown, the configuration of the parts other than the main part may be considered to be the same as that of the first embodiment shown in FIG. Two conventional examples to be compared with the essential parts of these embodiments are shown in FIGS. 5 and 6.

In FIG. 1, reference numeral 1 denotes a part of a cylinder head of an engine, in the vicinity of an end of a cam shaft 2 which is supported in the cylinder head, a cylinder around which a timing pulley 3 is rotatably supported. 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 is also integrated with the timing pulley 3 so that it can rotate on the axis of the camshaft 2. For convenience of assembling, maintenance and inspection, repair, etc., a cap 6 which is 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 pass through the respective central portions, and thereby the first
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 facing. This annular gap 13 is closed by a seal ring, so that the internal space of the housing 4 is divided into two parts, a hydraulic chamber 11 on the left side of the piston 12 on the advance side and a hydraulic chamber 14 on the right side of the retard side. To be done. In the conventional variable valve timing mechanism, the seal ring 15 or 16 as shown in FIGS. 5 and 6 is used to close the annular gap 13. On the other hand, the first embodiment of the present invention is characterized in that the seal ring 17 having an I-shaped cross section as shown in FIG. 2 is used, but the details will be described later.

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 a "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, the first output opening 1 of the hydraulic control valve 18
It communicates with 8a.

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. The second hydraulic passage 2f is further connected to the hole 2 of the camshaft 2.
g, the annular groove 2h, and the second hydraulic passage 1b formed in the cylinder head 1 to communicate with the second output opening 18b of the hydraulic control valve 18.

The hydraulic control valve 18 is generally called a spool valve because it has a spool 18c. 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 or the second output opening portion 18
Open and close b for a short time. At that time, 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, is adjusted to an arbitrary ratio. Distribute and output openings 18a and 18b
Can be discharged to.

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 an intermediate position in 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, the two hydraulic chambers 11, 14 are changed.
By finely adjusting the amount of oil supplied to the piston 12, the stop position of the piston 12 can be freely adjusted in a stepless manner.
Thereby, the opening / closing timing of the intake valve and the exhaust valve of the internal combustion engine can be smoothly changed.

In FIG. 1, reference numeral 23 is a crankshaft, 24 is a timing pulley on the crank side attached to the crankshaft 23, and 25 is a timing belt wound between the timing pulley 24 and the timing pulley 3 described above. Reference numeral 26 denotes a crank angle sensor that detects the rotation angle of the crankshaft 23, and 27 denotes a cam angle sensor that detects the rotation angle of the camshaft 2. The sensors 26 and 27 are specifically magnetic pickups, which generate an electrical pulse signal when a protrusion of a rotating member such as a gear-shaped member provided on the crankshaft 23 or the camshaft 2 passes through. , Detect the rotation angle of each axis.

Of the configuration of the first embodiment described above,
Most of the I-shaped section except the seal ring 17 is substantially the same as that of the conventional variable valve timing mechanism. In such a variable valve timing mechanism,
Timing pulley 2 from the crankshaft 23 to the drive side
The rotation of half the number of rotations is transmitted to the timing pulley 3 on the driven side by means of 4 and the timing belt 25, and the rotation is transmitted from the helical spline 4b of the housing 4 to the helical splines 12b and 12c of the piston 12 by the helical spline 12b and 12c. It is transmitted to the gear plate 7 having the spline 7a and further transmitted from the positioning pin 9 to the cam shaft 2 to rotationally drive a cam (not shown) to open and close valves such as an intake valve and an exhaust valve.

The relative phase relationship between the timing pulley 3 and the camshaft 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 is determined by the hydraulic control valve 18 operated by the command of the ECU 19 when the hydraulic chamber 1 on the advance side is set.
It is determined by controlling the amount of oil supplied to each of the hydraulic pressure chambers 1 and 1 on the retard side. 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. Generates a dither control signal that reduces the difference between the actual cam phase and the map data value,
The electric current to the solenoid 18d of the hydraulic control valve 18 is turned on and off.

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. The basic operation of the first embodiment is the same as that of the conventional variable valve timing mechanism.

As described above, when the seal ring is used to close the annular gap 13 between the piston 12 and the hydraulic cylinder 4a, it is formed on the outer circumference of the piston 12 in the first conventional example shown in FIG. A seal ring 15 made of fluororesin and having a rectangular cross section is fitted in the formed annular groove 12d. In this case, the outer diameter of the seal ring 15 is made equal to the inner diameter of the hydraulic cylinder 4a, and the seal ring 1
The inner diameter of 5 is made substantially equal to the outer diameter of the annular groove 12d.

The seal ring 15 is characterized by its material, which has a small friction coefficient against the surface of the hydraulic cylinder 4a and abundant wear resistance, so that the piston 12 can smoothly slide in the hydraulic cylinder 4a in the axial direction. it can. However, when the rotation of the timing pulley 3 is transmitted to the camshaft 2 as described above, when the reaction force in the axial direction of the helical splines 12b and 12c of the piston 12 of varying magnitude acts, the friction coefficient is small. Almost no braking force is generated by the seal ring 15 made of fluororesin, so the helical spline 12b is used during high-speed rotation.
And 12c and the backlash gap (playing clearance) between the helical spline 4b of the housing 4 and the helical spline 7a of the gear plate 7 which mesh with them.
At, the piston 12 may vibrate in the axial direction and a backlash noise may be generated.

In the second conventional example shown in FIG. 6, a rubber O-ring 28 is first attached to the bottom of the annular groove 12d on the outer circumference of the piston 12, and the O-ring 28 is superposed on the outer side of the O-ring 28 and is made of a fluororesin having a rectangular cross section. The seal ring 16 is fitted to close the annular gap 13. The outer diameter of the seal ring 16 is made equal to the inner diameter of the hydraulic cylinder 4a. Further, the outer diameter of the O-ring 28 when not mounted is made larger than the inner diameter of the seal ring 16, and the inner diameter of the O-ring 28 is the annular groove 1.
It is smaller than the outer diameter of 2d.

In this way, the O-ring 28 compressed by the seal ring 16 generates a radial force that pushes the seal ring 16 outward, so that the outer periphery of the seal ring 16 is hydraulic cylinder 4a. Pressed against the inner surface of the. As a result, the frictional force between the sliding surfaces of the hydraulic cylinder 4a and the seal ring 16 increases, which serves as a braking force for the vibration of the piston 12, so that the backlash noise is suppressed.

However, the braking force in the case of the second conventional example is always large irrespective of the rotational speed of the engine, that is, the rotational speed of the camshaft 2, so that the backlash noise is not generated even at the low speed rotation of the engine. Unnecessarily large braking force acts on the piston 12 and hinders its axial movement. Since the hydraulic pressures acting on the two hydraulic chambers 11 and 14 are both small at the time of low speed rotation, the difference between them is also small, and the force generated by the pressure difference is naturally small.
Therefore, it takes a relatively long time until this force overcomes the large braking force, and the axial movement of the piston 12 is delayed during that time. In the second conventional example, the response of the variable valve timing mechanism is increased. There is a problem that the sex is lowered.

In contrast to these conventional examples, in the first embodiment of the present invention, the seal ring 17 having an I-shaped cross section as shown in FIG. 2 is used by fitting it into the annular groove 12d of the piston 12. ing. The seal ring 17 is an annular outer rim 1.
7a and an inner rim 17b which is also annular in shape
It has a shape connected by 7c. Thereby, the seal ring 17 forms recesses 17d and 17e on the sides of the two hydraulic chambers 11 and 14 for receiving the control hydraulic pressure, respectively. The outer diameter of the seal ring 17 is approximately the same as the inner diameter of the hydraulic cylinder 4a, and the inner diameter of the seal ring 17 is the piston 1
The outer diameter is the same as the outer diameter of the second annular groove 12d. The material of the seal ring 17 is appropriately selected from materials having high wear resistance such as fluororesin.

The seal ring 17 of I-section in the first embodiment receives the pressurized oil in the two hydraulic chambers 11 and 14 into the recesses 17d and 17e, as shown by the arrow in FIG. Hydraulic rim, outer rim 1
7a is pressed outward in the radial direction and pressed against the inner surface of the hydraulic cylinder 4a. At the same time, the inner rim 17b
Is pushed inward in the radial direction and the annular groove 1 of the piston 12 is
It is pressed against the outer surface of 2d. As a result, the braking force in the axial direction according to the magnitude of the control hydraulic pressure acts on the piston 12 from the hydraulic cylinder 4a side. Since the magnitude of the braking force is proportional to the magnitude of the control oil pressure, a large braking force is generated at the time of high-speed rotation of the engine where the control oil pressure is high, the vibration of the piston 12 is suppressed, and the backlash noise is not generated. To prevent. In this way, even if the braking force acting on the piston 12 at the time of high speed rotation of the engine becomes large, the responsiveness of the variable valve timing mechanism does not deteriorate because the control hydraulic pressure for moving the piston 12 is large.

As described above, since the magnitude of the braking force acting on the piston 12 changes according to the magnitude of the pressure of oil (control oil pressure) in the hydraulic chambers 11 and 14, there is a risk of backlash noise. When the engine is running at low speed, the control oil pressure is reduced and the braking force is automatically reduced. Therefore, the resistance that hinders the movement of the piston 12 at the time of low speed rotation is reduced, so that the timing adjustment is smoothly performed even if the control hydraulic pressure for moving the piston 12 is small, and the responsiveness of the variable valve timing mechanism may deteriorate. There is no.

In the first embodiment, the engine oil (lubricating oil) of the engine is used as the hydraulic oil of the hydraulic control system in the variable valve timing mechanism, so that the oil pump 20 is the same as that for supplying lubricating oil. However, 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 be an independent hydraulic system using another hydraulic oil and the oil pump 20. Needless to say.

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 first embodiment shown in FIGS. 1 and 2, I
Although the seal ring 17 having a shaped cross section is mounted in the annular groove 12d on the outer periphery of the piston 12, the seal ring 17 is not limited to this position and may be mounted on the inner peripheral portion of the piston 12, for example. The structure of the main part is shown in FIG.
It is abbreviated to. In the second embodiment, the outer peripheral portion of the piston 12 is brought into direct sliding contact with the inner surface of the hydraulic cylinder 4a, and between the inner peripheral portion of the annular piston 12 and the outer surface of the hub portion 3a of the timing pulley 3. Annular gap 2
9 is formed, and a seal ring 17 having an I-shaped cross section similar to that of the first embodiment is mounted in the annular groove 12e formed in the inner peripheral portion of the piston 12 so as to close the gap 29. It is characterized in that it is in sliding contact with the hub portion 3a of the timing pulley 3.

The second embodiment is different from the first embodiment only in the installation position of the seal ring 17 having the I-shaped cross section, and the other structure is the same as that of the first embodiment shown in FIG. The description of the configuration of the second embodiment that is the same as that of the first embodiment will be omitted. Further, the operation and effect of the second embodiment are also substantially the same as those of the first embodiment, and the rim 17b inside the seal ring 17 having an I-shaped cross section is formed according to the magnitude of the control hydraulic pressure of the hydraulic chambers 11 and 14. Since the magnitude of the sliding frictional force with the hub portion 3a of the timing pulley 3 changes, the magnitude of the braking force with respect to the piston 12 also changes continuously steplessly, and the same preferable effect as in the case of the first embodiment is obtained. can get.

Next, as a third embodiment of the present invention, FIG. 4 shows only a main part of an embodiment in which the seal ring 17 having an I-shaped cross section is not used. Seal ring 3 used in the third embodiment
Reference numeral 0 denotes a C-shaped cross section, which has a shape in which an outer rim 30a and an inner rim 30b are connected by an intermediate portion 30c which is somewhat thin to have flexibility. As a result, the seal ring 30 having a C-shaped cross section is provided in the hydraulic chamber 11 on the advance side.
The depression 30d for receiving the control hydraulic pressure is formed. The material of the seal ring 30 may also be fluororesin. In the third embodiment, the seal ring 30 having a C-shaped cross section is the first.
Like the second embodiment, the piston 12 is mounted in the annular groove 12d on the outer periphery to close the annular gap 13. However, as in the second embodiment, the piston 12 is mounted in the annular groove 12e on the inner periphery. Alternatively, the annular gap 29 may be closed.

Since the seal ring 30 having the C-shaped cross section corresponds to half the cross-sectional shape of the seal ring 17 having the I-shaped cross section, in the case of FIG. 4, the control hydraulic pressure in the hydraulic chamber 11 on the advance side is depressed 30 d.
When received in, the same operational effects as those of the first and second embodiments are achieved. Needless to say, if the mounting direction of the seal ring 30 having a C-shaped cross section is set to be opposite to that shown in FIG. 4, the control oil pressure in the hydraulic chamber 14 on the retard angle side is received and the same operational effect is obtained. Piston 12 always has two hydraulic chambers 1
Since the control hydraulic pressures 1 and 14 move so as to have the same value, if the braking force of the piston 12 changes according to the magnitude of one of the control hydraulic pressures, the object of the present invention can be sufficiently achieved. be able to.

[0041]

According to the present invention, in a variable valve timing mechanism having a helical spline operated by a piston of a hydraulic cylinder, it is possible to simultaneously solve the problem of backlash noise and the problem of deterioration of responsiveness. You can

[Brief description of drawings]

FIG. 1 is a sectional view of an entire variable valve timing mechanism showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of the first embodiment.

FIG. 3 is a cross-sectional view showing the main parts of the second embodiment.

FIG. 4 is a cross-sectional view showing the main parts of the third embodiment.

FIG. 5 is a cross-sectional view showing a conventional example.

FIG. 6 is a cross-sectional view showing another conventional example.

[Explanation of symbols]

 1 ... 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 ... Cylindrical part (rotation transmitting member) 12b, 12c ... Helical splines 12d, 12e ... Annular groove 13 ... Annular gap 14 ... Retardation side hydraulic chamber 15, 16 ... Conventional seal ring 17 ... Seal ring of I-shaped cross section 17a ... Outer rim 17b ... Inner rim 17d, 17e ... Recess 18 ... Hydraulic control valve 18c ... Spool 18d ... Solenoid 19 ... ECU (control unit) 20 ... Oil pump 22 ... Oil pan 23 ... Crank shaft 24 ... Crank side Timing pulley 25 ... Timing belt 26 ... Crank angle sensor 27 ... cam angle sensor 28 ... O-ring 29 ... of the annular gap 30 ... cross-section C-shaped seal ring 30a ... outer rim 30b ... inner rim 30d ... recess

Claims (5)

[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 cam shaft; a seal ring attached to the piston; a helical spline formed on the hydraulic cylinder side; A helical spline formed on the shaft side, and 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. A hydraulic control valve that selectively supplies a control hydraulic pressure to the hydraulic chambers, and a control device that drives and controls the hydraulic control valve, wherein the seal ring receives the control hydraulic pressure of at least one of the two hydraulic chambers. Is deformable in the radial direction, and at least one recessed portion for receiving the control oil pressure is provided so that the frictional force with respect to the sliding surface of the other party changes according to the magnitude of the control oil pressure. Variable valve timing mechanism. 2. The variable valve timing mechanism of claim 1, wherein the seal ring has an I-shaped cross section. 3. The variable valve timing mechanism of claim 1, wherein the seal ring has a C-shaped cross section. 4. The variable valve timing mechanism according to claim 1, wherein the seal ring is mounted on the outer peripheral surface of the piston. 5. The variable valve timing mechanism according to claim 1, wherein the seal ring is mounted on an inner peripheral surface of the piston.