JP2015113783A - Valve timing variable mechanism of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a rotor to be relatively moved with respect to a housing across an intermediate position to prevent a first pin from contacting an outer peripheral face of an end on an outer peripheral side of a spring to slide with the outer peripheral face in a circumferential direction when an object to be engaged at the end part of the outer peripheral side of the spring is switched between the first pin and a second pin.SOLUTION: An end part 28a at an internal peripheral side of a spiral spring 28 in a valve timing variable mechanism is engaged with a notch 31 of a front bush 27 which is fixed to a rotor. Then, the relative movement of the rotor with respect to a housing 4 of the mechanism across an intermediate lock position of the rotor allows an object to be engaged of the end part 28b at an external peripheral side of the spring 28 to be switched between a first pin 29 fixed to the rotor and a second pin 30 fixed to the housing 4. The first pin 29 is provided at a piston in which a center line CL1 of the first pin is offset to a direction separated from an external peripheral face of the end part 28b of the external peripheral side of the spring 28 with respect to a center line CL2 of the second pin 30.

Description

  The present invention relates to a variable valve timing mechanism for an internal combustion engine.

  A variable valve timing mechanism for an internal combustion engine includes a housing that receives rotation transmission from a crankshaft, and a rotor that rotates integrally with a camshaft. The rotor is provided in the housing so as to be capable of relative rotation (relative movement in the rotation direction) with respect to the housing. In this variable valve timing mechanism, by changing the relative rotation phase of the camshaft with respect to the crankshaft through relative rotation between the housing and the rotor, the opening / closing timing (valve timing) of the engine valve that opens and closes as the camshaft rotates is changed. Variable.

  Further, as a variable valve timing mechanism, there is known a mechanism in which the rotor is fixed to the housing or released from the housing by a lock mechanism at an intermediate position of the relative movement range of the rotor with respect to the housing. In such a valve timing variable mechanism, the rotor can be relatively moved to the intermediate position when the internal combustion engine is started to stop under the state where the rotor is relatively moved to the retard side relative to the intermediate position. A spring is provided that applies an elastic force toward the intermediate position to the rotor relatively moved to the retard side from the intermediate position.

  This spring is formed, for example, in a spiral shape around the camshaft. And the edge part of the inner peripheral side in a spring is engaged with a rotor. On the other hand, the outer peripheral end of the spring can be engaged with a first pin fixed to the rotor or a second pin fixed to the housing, as shown in Patent Document 1, for example. The first pin and the second pin of Patent Document 1 are provided so that their center lines are located on concentric circles centering on the axis of the camshaft.

  When the rotor is positioned on the advance side with respect to the intermediate position of the relative movement range with respect to the housing, the outer peripheral end of the spring engages with the first pin fixed to the rotor. At this time, the rotor is not biased toward the intermediate position through the elastic force of the spring. On the other hand, when the rotor is moved relative to the housing relative to the retard side relative to the intermediate position in the relative movement range, the outer peripheral end of the spring engages with the second pin fixed to the housing. At this time, the elastic force of the spring acts on the rotor, so that the rotor is biased toward the intermediate position.

JP 2010-180862 A

  By the way, in the said valve timing variable mechanism, the diameter of a 1st pin becomes larger than the diameter of a 2nd pin from the relationship of the required intensity | strength of a 1st pin and a 2nd pin, and the restrictions of the installation space of each of these pins. There is a case. In this case, the rotor moves relative to the housing relative to the intermediate position, so that the outer peripheral end of the spring is near the outer peripheral end before and after the outer peripheral end of the spring is switched between the first pin and the second pin. The first pin comes into contact with the outer peripheral surface of the outer peripheral surface and slides in the circumferential direction of the outer peripheral surface.

  FIG. 9 shows the difference in diameter between the first pin 51 and the second pin 52. The center lines CL1 and CL2 of the first pin 51 and the second pin 52 are positioned on a concentric circle C centered on the camshaft axis Lc. Since the diameter of the first pin 51 is larger than the diameter of the second pin 52, the amount of protrusion of the first pin 51 from the concentric circle C toward the camshaft axis Lc is from the concentric circle C of the second pin to the camshaft. It becomes larger than the amount of protrusion toward the axis Lc.

  10 to 12 show the positional relationship between the first pin 51, the second pin 52, and the outer end of the spring 53 when the rotor 55 moves relative to the housing 54 across the intermediate position. Yes. Specifically, in FIGS. 10A and 10B, FIGS. 11A and 11B, and FIGS. 12A and 12B, the rotor 55 is retarded relative to the housing 54 from the intermediate position. The positional relationship is shown in a state where the rotor 55 is positioned near the intermediate position, and in a state where the rotor 55 is positioned closer to the advance side than the intermediate position.

  As can be seen from these figures, before and after the engagement object of the outer peripheral end of the spring 53 is switched between the first pin 51 and the second pin 52, the first pin 51, the second pin 52, and When the end portion on the outer peripheral side of the spring 53 has the positional relationship shown in FIG. 10, the first pin 51 contacts the outer peripheral surface near the end portion on the outer peripheral side of the spring 53 and slides in the circumferential direction of the outer peripheral surface.

  FIG. 13 shows a manner of generating torque that acts in the rotational direction of the rotor 55 through the elastic force of the spring 53. When the rotor 55 is positioned on the more advanced side than the intermediate position with respect to the housing 54, the torque due to the elastic force of the spring 53 is not generated. On the other hand, when the rotor 55 is positioned on the retard side with respect to the housing 54, the torque is generated by the elastic force of the spring 53.

  Here, assuming that the area indicated by hatching in the figure is the generation area of the torque according to the design intention, the first pin 51 is placed on the outer peripheral surface near the end on the outer peripheral side of the spring 53 as shown in FIG. By contacting and sliding in the circumferential direction of the outer peripheral surface, the torque generation region expands to a region surrounded by a two-dot chain line in FIG. This is because the first pin 51 comes into contact with the outer peripheral surface in the vicinity of the end portion on the outer peripheral side of the spring 53, so that the torque generation mode varies.

  When the torque generation area expands to the area surrounded by the two-dot chain line in FIG. 13, when the torque increases beyond the upper limit value or decreases beyond the lower limit value, the internal combustion engine There is a risk that cranking will be adversely affected and the operation response speed of the variable valve timing mechanism may be reduced.

  The object of the present invention is to make the first pin of the spring move when the engagement object of the outer peripheral end of the spring is switched between the first pin and the second pin by the relative movement of the rotor across the intermediate position with respect to the housing. An object of the present invention is to provide a variable valve timing mechanism for an internal combustion engine that can suppress contact with the outer peripheral surface of the outer peripheral end portion and sliding in the circumferential direction of the outer peripheral surface.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
A variable valve timing mechanism for an internal combustion engine that solves the above-described problem is a housing that receives rotation transmission from a crankshaft, and is provided in the housing and can move relative to the housing in the rotational direction while rotating integrally with the camshaft And a rotor. Further, the variable valve timing mechanism includes a spring formed in a spiral shape with the camshaft as the center and an end on the inner peripheral side engaged with the rotor, and an end on the outer peripheral side of the spring fixed to the rotor. A first pin that engages; and a second pin that is fixed to the housing and engageable with an end portion on an outer peripheral side of the spring. Then, as the relative movement of the rotor relative to the housing moves relative to the retard side relative to the intermediate position, the engagement target of the outer peripheral end of the spring is switched from the first pin to the second pin. The elastic force of the spring acts on the rotor in the direction of relative movement toward the advance side with respect to the housing.

  Each of the first pin and the second pin has a center line extending in the same direction as the camshaft, and the diameter of the first pin is larger than the diameter of the second pin. Here, if the first pin and the second pin are provided so that the center line of the first pin and the second pin is located on a concentric circle centering on the axis of the camshaft, The amount of protrusion from the concentric circle toward the axis of the camshaft is larger than the amount of protrusion of the second pin from the concentric circle toward the axis of the camshaft. For this reason, when the rotor moves relative to the housing relative to the intermediate position, before and after the engagement of the outer peripheral end of the spring is switched between the first pin and the second pin, the vicinity of the outer peripheral end of the spring The first pin comes into contact with the outer peripheral surface of the outer peripheral surface and slides in the circumferential direction of the outer peripheral surface.

  In order to cope with this, the first pin is provided at a position where its center line is offset in a direction away from the outer peripheral surface of the end portion on the outer peripheral side of the spring with respect to the center line of the second pin. As a result, the portion of the first pin that is closest to the axis of the camshaft is separated from the outer peripheral surface of the outer peripheral end of the spring. Therefore, when the rotor is moved relative to the housing across the intermediate position, the engagement target of the outer peripheral end of the spring is switched between the first pin and the second pin before and after the outer peripheral end of the spring. It is suppressed that the first pin comes into contact with the outer peripheral surface and slides in the circumferential direction of the outer peripheral surface.

1 is a schematic diagram showing a variable valve timing mechanism of an internal combustion engine and a hydraulic circuit that hydraulically operates the mechanism. Sectional drawing which looked at the valve timing variable mechanism of FIG. 1 from the arrow AA direction. The front view which shows the front bush and spring which are provided in a valve timing variable mechanism. Schematic which shows arrangement | positioning of a 1st pin and a 2nd pin. (A) And (b) is the positional relationship of the edge part of the outer peripheral side of a 1st pin, a 2nd pin, and a spring in the state where the rotor is located in the retarded angle side with respect to the housing. Schematic showing. (A) And (b) is the schematic which shows the positional relationship of the edge part of the outer peripheral side of a 1st pin, a 2nd pin, and a spring when the rotor is located in the intermediate | middle lock position vicinity with respect to the housing. (A) And (b) shows the positional relationship of the end part of the outer peripheral side of the 1st pin, the 2nd pin, and the spring when the rotor is located at an advanced angle side with respect to the housing. Schematic showing. The figure which shows the generation | occurrence | production area | region of the torque which acts on a rotor with the elastic force of a spring. Schematic which shows the detail of a 1st pin and a 2nd pin. (A) And (b) is the positional relationship of the edge part of the outer peripheral side of a 1st pin, a 2nd pin, and a spring in the state where the rotor is located in the retarded angle side with respect to the housing. Schematic showing. (A) And (b) is the schematic which shows the positional relationship of the edge part of the outer peripheral side of a 1st pin, a 2nd pin, and a spring when the rotor is located in the intermediate | middle lock position vicinity with respect to the housing. (A) And (b) shows the positional relationship of the end part of the outer peripheral side of the 1st pin, the 2nd pin, and the spring when the rotor is located at an advanced angle side with respect to the housing. Schematic showing. The figure which shows the generation | occurrence | production area | region of the torque which acts on a rotor with the elastic force of a spring.

Hereinafter, an embodiment of a variable valve timing mechanism for an internal combustion engine will be described with reference to FIGS.
As shown in FIG. 1, the variable valve timing mechanism 1 for an internal combustion engine includes a rotor 3 fixed by bolts to a camshaft 2 (for example, an intake camshaft) of the engine, and the rotor on the same axis as the camshaft 2. 3 and a housing 4 that is provided so as to surround the crankshaft of the internal combustion engine. A plurality of protrusions 5 projecting toward the axis of the camshaft 2 are formed on the inner peripheral surface of the housing 4 at predetermined intervals in the circumferential direction. A plurality of vanes 6 projecting in a direction away from the axis of the camshaft 2 are formed on the outer peripheral surface of the rotor 3 so as to be positioned between the protrusions 5. As a result, a portion located between the protrusions 5 in the housing 4 is partitioned into an advance side hydraulic chamber 7 and a retard side hydraulic chamber 8 by the vane 6.

  When oil is supplied to the advance side hydraulic chamber 7 and discharged from the retard side hydraulic chamber 8, the rotor 3 moves relative to the housing 4 in the clockwise direction in FIG. The relative rotation phase with respect to the shaft changes to the advance side, and thereby the valve timing of the engine valve (in this example, the intake valve) of the internal combustion engine changes to the advance side. When oil is supplied to the retarded hydraulic chamber 8 and discharged from the advanced hydraulic chamber 7, the rotor 3 moves relative to the housing 4 in the counterclockwise direction in the figure, and the camshaft 2 crankshaft. The relative rotational phase of the internal combustion engine changes to the retard side, whereby the valve timing of the engine valve of the internal combustion engine changes to the retard side.

  Oil supply / discharge of the advance-side hydraulic chamber 7 and the retard-side hydraulic chamber 8 of the variable valve timing mechanism 1 is controlled by driving an oil control valve 10 provided in a hydraulic circuit connecting the mechanism 1 and the oil pump 9. Is done. The oil control valve 10 is connected to an oil pump 9 via a supply passage 11 and connected to an oil pan 12 for storing oil pumped up by the oil pump 9 via a discharge passage 13. Yes. The oil control valve 10 is connected to the advance side hydraulic chamber 7 of the variable valve timing mechanism 1 via the advance side oil passage 14 and is retarded to the retard side hydraulic chamber 8 of the mechanism 1. The side oil passage 15 is connected.

  The variable valve timing mechanism 1 includes a lock mechanism 16 that performs a prohibiting operation for prohibiting relative movement of the rotor 3 with respect to the housing 4 and performs a permitting operation for permitting the relative movement. The prohibition of the relative movement of the rotor 3 with respect to the housing 4 by the lock mechanism 16 is a position (intermediate position) other than the end of the relative movement range in the rotation direction of the rotor 3 with respect to the housing 4 and the valve timing of the intake valve. Is performed at an intermediate lock position which is a position suitable for starting the engine.

Next, how the variable valve timing mechanism 1 is attached to the camshaft 2 will be described in detail.
As shown in FIG. 2, in the variable valve timing mechanism 1, the rotor 3 is fixed to the end of the camshaft 2 by bolts 23 and can rotate integrally with the camshaft 2, and the housing surrounds the rotor 3. 4 is supported by the camshaft 2 so as to be rotatable around the camshaft 2. The housing 4 includes a front plate 24 and a rear plate 25 that sandwich the rotor 3 from both sides in the thickness direction (the left-right direction in the figure), a side ring 26 that is located on the outer periphery of the rotor 3 and surrounds the entire outer periphery of the rotor 3. The front plate 24, the rear plate 25, and the side ring 26 are connected so as to be integrally rotatable.

  A front bush 27 is sandwiched between the head 23a of the bolt 23 and the rotor 3. By tightening the bolt 23, the front bush 27 is fixed to the rotor 3 and can rotate integrally with the rotor 3. It has become. Around the front bush 27, a spiral spring 28 centered on the camshaft 2 is provided. When the rotor 3 relative to the housing 4 moves relative to the retard angle side with respect to the intermediate lock position, the spring 28 applies an elastic force toward the intermediate lock position to the rotor 3, thereby causing the rotor 3 to move. It is for urging toward the intermediate lock position.

  As shown in FIG. 3, an inner peripheral end 28 a of the spring 28 is engaged with a notch 31 formed in the front bush 27. Since the front bush 27 is fixed to the rotor 3, the end 28 a of the spring 28 at this time is engaged with the rotor 3 via the front bush 27. Further, the outer end 28b of the spring 28 can be engaged with a first pin 29 fixed to the front bush 27 or a second pin 30 fixed to the housing 4 (precisely the front plate 24). ing. As for the 1st pin 29 and the 2nd pin 30, each centerline CL1, CL2 is extended in the same direction as the camshaft 2. FIG. Further, the diameter of the first pin 29 is larger than the diameter of the second pin 30.

  Here, when the rotor 3 and the front bush 27 move relative to the housing 4 toward the retard side (in the direction of the arrow Y1) with respect to the intermediate lock position, the end portion 28b of the spring 28 is engaged with the second pin 30 of the front plate 24. On the other hand, with the engagement, the first pin 29 of the front bush 27 is separated from the end portion 28b in the direction of the arrow Y1. As a result, an elastic force in the advance direction toward the intermediate lock position by the spring 28 acts on the front bush 27 (rotor 3). Further, when the rotor 3 and the front bush 27 move relative to the housing 4 toward the advance side (in the direction of the arrow Y2) with respect to the intermediate lock position, the end portion 28b of the spring 28 engages with the first pin 29 of the front bush 27. On the other hand, the end portion 28b is separated from the second pin 30 of the front plate 24 in the arrow Y2 direction in accordance with the engagement. At this time, the elastic force toward the intermediate lock position by the spring 28 does not act on the front bush 27 (rotor 3).

  As can be seen from the above, when the rotor 3 moves relative to the housing 4 across the intermediate lock position, the engagement target of the end portion on the outer peripheral side of the spring 53 is switched between the first pin 51 and the second pin 52. The end 28 b of the spring 28 engages with the second pin 30 only when the rotor 3 and the front bush 27 move relative to the housing 4 toward the retard side (in the direction of the arrow Y 1) relative to the intermediate lock position. Since the second pin 30 is formed on the front plate 24, the end portion 28 b is engaged with the front plate 24 (housing 4) via the second pin 30 at this time, and the spring 28 is attached to the front bush 27. The elastic force in the advance angle direction toward the intermediate lock position by acts.

  As shown in FIG. 4, the first pin 29 has a center line CL <b> 1 away from the outer peripheral surface of the outer end 28 b of the spring 28 with respect to the center line CL <b> 2 of the second pin 30, i.e., the axis of the camshaft 2. It is provided at a position offset in a direction away from Lc. More specifically, the portion of the first pin 29 closest to the axis Lc of the camshaft 2 and the portion of the second pin 30 closest to the axis Lc of the camshaft 2 are on a concentric circle C1 centered on the axis Lc. The first pin 29 is offset in the above-described direction so as to be positioned.

Next, the operation of the variable valve timing mechanism 1 of the present embodiment will be described.
5 to 7 show the outer peripheral end portions of the first pin 29, the second pin 30, and the spring 28 when the rotor 3 (front plate 24) moves relative to the housing 4 across the intermediate lock position. The positional relationship of 28b is shown. Specifically, in FIGS. 5A and 5B, FIGS. 6A and 6B, and FIGS. 7A and 7B, the rotor 3 is later than the intermediate lock position with respect to the housing 4, respectively. The positional relationship is shown in a state in which the rotor 3 is positioned near the intermediate lock position, and in a state in which the rotor 3 is positioned closer to the advance side than the intermediate lock position.

  As can be seen from these figures, before and after the engagement of the outer peripheral end of the spring 53 is switched between the first pin 29 and the second pin 30, the first pin 29 is connected to the outer peripheral end 28b of the spring 28. There is no contact with the nearby outer peripheral surface and it does not slide in the circumferential direction of the outer peripheral surface. This is because the portion of the first pin 29 closest to the axis Lc of the camshaft 2 and the portion of the second pin 30 closest to the axis Lc of the camshaft 2 are located on a concentric circle C1 centered on the axis Lc. It is because it is doing. That is, the direction in which the center line CL1 of the first pin 29 is away from the outer peripheral surface of the outer end 28b of the spring 28 with respect to the center line CL2 of the second pin 30, that is, the direction away from the axis Lc of the camshaft 2. This is because the first pin 29 is provided so as to be offset.

  FIG. 8 shows a manner of generating torque that acts in the rotational direction of the rotor 3 through the elastic force of the spring 28. When the rotor 3 is positioned on the advance side of the intermediate lock position with respect to the housing 4, the torque due to the elastic force of the spring 53 is not generated. On the other hand, when the rotor 55 is positioned on the retard side with respect to the housing 54 with respect to the intermediate lock position, the torque due to the elastic force of the spring 53 is generated. In addition, the area | region shown with the oblique line in the figure has shown the generation | occurrence | production area | region of the said torque, and as shown in the area | region enclosed with the dashed-two dotted line in FIG. This is because the first pin 29 is placed on the outer peripheral surface in the vicinity of the end portion 28 b on the outer peripheral side of the spring 28 before and after the engagement target of the outer peripheral end portion of the spring 53 is switched between the first pin 29 and the second pin 30. This is because there is no contact, and there is no variation in the torque generation mode caused by the contact.

According to the embodiment described in detail above, the following effects can be obtained.
(1) When the rotor 55 moves relative to the housing 54 across the intermediate lock position, the engagement object of the outer end 28b of the spring 28 is switched between the first pin 29 and the second pin 30. It can suppress that the 1st pin 29 contacts with the outer peripheral surface of the edge part 28b of the outer peripheral side of the spring 28, and slides in the circumferential direction of the outer peripheral surface.

  (2) If the first pin 29 comes into contact with the outer peripheral surface of the end portion 28b and slides in the circumferential direction, it acts in the rotational direction of the rotor 3 by the hatched area in FIG. There is a possibility that the generation area of the torque to be expanded will increase, and the torque will increase beyond the upper limit value or decrease beyond the lower limit value. When the torque increases beyond the upper limit value or decreases beyond the lower limit value, the cranking of the internal combustion engine is adversely affected, or the operation response speed of the variable valve timing mechanism 1 decreases. There are problems, but the occurrence of these problems can be avoided.

In addition, the said embodiment can also be changed as follows, for example.
The portion of the first pin 29 closest to the axis Lc of the camshaft 2 and the portion of the second pin 30 closest to the axis Lc of the camshaft 2 are necessarily located on the concentric circle C1 centered on the axis Lc. There is no need to be.

  The engine valve whose valve timing is variable by the valve timing variable mechanism may be an exhaust valve.

  DESCRIPTION OF SYMBOLS 1 ... Valve timing variable mechanism, 2 ... Cam shaft, 3 ... Rotor, 4 ... Housing, 5 ... Projection, 6 ... Vane, 7 ... Advance side hydraulic chamber, 8 ... Delay side hydraulic chamber, 9 ... Oil pump, DESCRIPTION OF SYMBOLS 10 ... Oil control valve, 11 ... Supply passage, 12 ... Oil pan, 13 ... Discharge passage, 14 ... Advance angle side oil passage, 15 ... Delay angle side oil passage, 16 ... Lock mechanism, 23 ... Bolt, 24 ... Front plate , 25 ... rear plate, 26 ... side ring, 27 ... front bush, 23a ... head, 28 ... spring, 28a ... end, 31 ... notch, 28b ... end, 29 ... first pin, 30 ... first 2 pins.

Claims (1)

A housing that receives rotation transmission from the crankshaft, a rotor that is provided in the housing and can rotate relative to the housing while rotating integrally with the camshaft, and a spiral shape around the camshaft A spring whose inner peripheral end is engaged with the rotor, a first pin fixed to the rotor and engaged with an outer peripheral end of the spring, and a spring fixed to the housing And a second pin that can be engaged with the outer peripheral end of the spring, and the outer peripheral end of the spring in accordance with the relative movement of the rotor relative to the housing toward the retard side relative to the intermediate position of the relative movement range of the rotor. When the object to be engaged is switched from the first pin to the second pin, the rotor is oriented in the direction of relative movement toward the advance side with respect to the housing. Te, In the variable valve timing mechanism for an internal combustion engine which applies an elastic force of the spring in the rotor,
Each of the first pin and the second pin has a center line extending in the same direction as the camshaft, and the diameter of the first pin is larger than the diameter of the second pin.
The first pin is provided at a position where its center line is offset in a direction away from the outer peripheral surface of the outer peripheral end of the spring with respect to the center line of the second pin. Valve timing variable mechanism.