JP2017031854A - Variable valve timing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a difference between an advance-side response speed and a retardation-side response speed without employing a spring which is unnecessary high in an elastic coefficient.SOLUTION: A variable valve timing device 26 has a first rotation part (housing 32) to which rotation power is transmitted from a crankshaft via a power transmission member (timing chain), and a second rotation part (rotor) which is equalized in a rotating shaft with the first rotation part, and connected to the second rotation part (rotor). The variable valve timing device also comprises: a variable timing mechanism which adjusts a phase difference between the first rotation part and the second rotation part; an energization member 40 which energizes the second rotation part to a rotation direction of a camshaft with respect to the first rotation part; and friction alleviation means 42 which alleviates friction caused by the contact of members which contribute to the energization of the energization member.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a variable valve timing device provided in an engine.

  Conventionally, an engine equipped with a variable valve timing mechanism (VVT: Variable Valve Timing) that varies the rotational phase of the camshaft with respect to the crankshaft of the engine has been put into practical use. The valve timing of at least one of the intake valve and the exhaust valve can be continuously changed.

  In such a variable valve timing mechanism, the response speed when adjusting the phase toward the advance side (hereinafter referred to as the advance side response speed) due to the mechanical loss of the variable valve timing mechanism and the frictional resistance generated between the camshaft and the bearing. Is also known to be delayed from the response speed when the phase is adjusted to the retard side (hereinafter also referred to as the retard side response speed). Therefore, in order to suppress the difference between the advance side response speed and the retard side response speed, an urging member (such as a spiral spring or a spring spring) that applies an urging force to the advance side (rotation direction) may be provided ( For example, Patent Document 1). Here, the response speed is a speed at which the camshaft rotates to a predetermined position on the advance side or the retard side when the variable valve timing device adjusts the rotation phase of the camshaft.

JP 2001-41013 A

  However, even if a biasing member such as a spiral spring is provided as in Patent Document 1, the frictional resistance generated by the contact between the spiral springs acts negatively against the biasing force, and the biasing force of the biasing member is reduced. Therefore, it was necessary to use a spring with a higher elastic modulus than necessary. As a result, the mass and occupied volume of the urging member are increased, and the cost is increased.

  Therefore, an object of the present invention is to provide a variable valve timing device that can suppress the difference between the advance side response speed and the retard side response speed without using an unnecessarily high elastic modulus spring. .

  In order to solve the above-described problems, a variable valve timing device according to the present invention includes a first rotating part to which rotational power is transmitted from a crankshaft through a power transmission member, a first rotating part, and a rotating shaft that are equalized. A variable valve timing mechanism that adjusts a phase difference between the first rotating unit and the second rotating unit, and a second rotating unit relative to the first rotating unit. An urging member for urging in the rotation direction of the urging member, and a friction reducing means for reducing friction caused by contact between portions of the urging member that contribute to urging.

  Further, the urging member may be a spiral spring in which a plate-like member is spirally wound.

  Further, the friction reducing means may be a friction reducing member that is located between the plate-like members of the spiral spring and has a material having a smaller friction coefficient than the surface of the spiral spring at a position facing the surface of the spiral spring.

  The friction reducing means may be one in which the opposing surfaces of the spiral spring are polished.

  Further, the friction reducing means may be located in a range where the spiral springs come into contact with each other by the biasing force of the spiral spring itself when the spiral spring is disposed in a state where the biasing force is stored.

  According to the present invention, it is possible to suppress the difference between the advance side response speed and the retard side response speed without using an unnecessarily high spring.

It is the figure which showed a part of engine provided with the variable valve timing apparatus. It is the II-II sectional view taken on the line in FIG. It is a perspective view which shows the external appearance of a variable valve timing apparatus. It is a figure which shows the change of the advance side response speed and retard angle side response speed by providing a friction reduction means.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a view showing a part of an engine 10 provided with a variable valve timing device. Among these, FIG. 1A shows a perspective view of the engine 10, and FIG. 1B shows a top view of the engine 10. Here, the engine 10 is, for example, a four-cylinder horizontally opposed engine in which two cylinders on one side are arranged with the crankshaft 12 as a boundary.

  As shown in FIGS. 1 (a) and 1 (b), in the engine 10, intake, compression, combustion, and exhaust strokes are performed inside a combustion chamber (not shown), and a piston performs a straight motion. The rectilinear motion of the piston is converted into rotational motion (in the direction of the white arrow in the figure) via a connecting rod connected to the piston, and is transmitted to the crankshaft 12.

  The rotational movement of the crankshaft 12 was wound around a crank sprocket 14 provided on the crankshaft 12 and a cam sprocket 18 provided at the end of the camshaft 16 in the axial direction (hereinafter simply referred to as the axial direction). It is transmitted to the camshaft 16 via the timing chain (power transmission member) 20 (in the direction of the white arrow in the figure).

  A plurality of cams 22 are fixed to the camshaft 16 so as to be separated from each other, and the camshaft 16 and the cams 22 rotate integrally. The cam 22 is provided in contact with the valve heads of the valves 24 (the intake side valve 24a and the exhaust side valve 24b), and the cam 22 directly presses the valve lifter of the valve 24 so that the valve 24 is pressed. Opening and closing operations are performed. In the present embodiment, as shown in FIG. 1, the intake side camshaft 16 a and the exhaust side camshaft 16 b independently control the opening / closing operation of the valve 24 for one cylinder. An engine 10 having a mechanism called DOHC (Double Over Head Camshaft) is illustrated. In the present embodiment, among the variable valve timing devices provided on the intake camshaft 16a and the exhaust camshaft 16b, in particular, the variable valve timing device 26 provided on the intake camshaft 16a. Will be described. The variable valve timing device 26 is a device that transmits the rotational power transmitted through the cam sprocket 18 to the camshaft 16.

  The variable valve timing device 26 includes a variable valve timing mechanism 30 (see FIG. 2) that continuously changes the rotational phase of the camshaft 16 relative to the crankshaft 12 (hereinafter also simply referred to as phase) in accordance with the operating state of the engine 10. Is provided.

  2 is a cross-sectional view taken along line II-II in FIG. In FIG. 2, white arrows indicate the rotation direction of the variable valve timing device 26 (cam sprocket 18) by the timing chain 20, and black arrows A (Advance) and R (Retard) indicate the camshaft 16. Indicates the direction in which the phase is adjusted, and the solid line arrows indicate the flow paths through which the hydraulic oil flows. Hereinafter, the rotation direction of the variable valve timing device 26 is simply referred to as the rotation direction.

  As shown in FIG. 2, the variable valve timing mechanism 30 includes a housing (first rotating portion) 32, a rotor (second rotating portion) 34, a phase adjustment valve 36, and a lock mechanism. The locking mechanism is a mechanism that fixes (locks) the opening / closing timing of the valve 24 at a predetermined timing when the hydraulic pressure is low, such as when the engine 10 is started, but is not directly related to the present embodiment. The description is omitted.

  The housing 32 is fixed with a cam sprocket 18 having a plurality of external teeth formed on the outer periphery in the radial direction, and the power of the crankshaft 12 (see FIG. 1) is transmitted through the cam sprocket 18. At this time, the housing 32 rotates at half the rotational speed of the crankshaft 12. In addition, in the housing 32, in order to accommodate the rotor 34, there is provided an accommodating space including a circular space and a plurality of fan-shaped spaces S cut out in a fan shape from the circular space toward the radially outer side. .

  The rotor 34 is housed in a housing space provided in the housing 32 with the rotation axis being equalized, and is fixed to the end of the camshaft 16. The rotor 34 is formed with a plurality (three in this embodiment) of vanes 34a that protrude outward in the radial direction and are accommodated in the fan-shaped space S on the radially outer surface. The rotor 34 can rotate relative to the housing 32 within a range in which the vane 34 a can move in the fan-shaped space S. The vane 34a is formed to be narrower in the rotation direction than the fan-shaped space S. The fan-shaped space S is divided into an advance chamber S1 (hydraulic chamber that operates the rotor 34 in the advance direction) and a retard chamber S2 (rotor 34). Into a hydraulic chamber that operates in the retarded direction. Here, the advance direction is the direction indicated by the black arrow A in FIG. 2, and the retard direction is the direction indicated by the black arrow R in FIG.

  The phase adjusting valve 36 is a spool valve configured by inserting a spool 36b into a sleeve 36a in which a plurality of ports H are formed. In each port H of the sleeve 36a, a hydraulic pressure supply line 36c for supplying hydraulic pressure into the sleeve 36a by the oil pump P, an advance hydraulic pressure supply line 36d for supplying hydraulic pressure to the advance chamber S1, and a retard chamber S2 are provided. A retarding hydraulic pressure supply line 36e for supplying hydraulic pressure and a drain line 36f for discharging unnecessary hydraulic fluid from the sleeve 36a are connected to each other. Here, for convenience of explanation, an example is given in which the advance hydraulic pressure supply line 36d supplies hydraulic pressure to one advance chamber S1, and the retard hydraulic supply line 36e supplies hydraulic pressure to one retard chamber S2. Explains.

  The phase adjustment valve 36 is provided with a solenoid E and a spring member 36g. When the solenoid E is on, the spool 36b is moved in a predetermined direction (left direction in the figure) by electromagnetic force. When the solenoid E is off, the biasing force of the spring member 36g is used. Thus, the spool 36b is moved in the direction opposite to the predetermined direction (right direction in the figure). The solenoid E is on / off controlled by an unillustrated ECU (Engine Control Unit) or the like. By this on / off control, the spool 36b moves between a position where the hydraulic pressure supply line 36c and the advance hydraulic pressure supply line 36d communicate with each other and a position where the hydraulic pressure supply line 36c and the retard hydraulic pressure supply line 36e communicate with each other. Be made.

  Here, when the spool 36b is moved to a position where the hydraulic pressure supply line 36c and the advance hydraulic pressure supply line 36d communicate with each other, the hydraulic pressure supplied from the oil pump P into the sleeve 36a passes through the advanced hydraulic pressure supply line 36d. To the advance chamber S1. At this time, the oil in the retarding chamber S2 is discharged from the retarding chamber S2, and the rotor 34 rotates relative to the housing 32 in the direction indicated by the black arrow A (advanced side) in the drawing. . When the spool 36b is moved to a position where the hydraulic pressure supply line 36c and the retarding hydraulic pressure supply line 36e communicate with each other, the hydraulic pressure supplied from the oil pump P to the sleeve 36a passes through the retarding hydraulic pressure supply line 36e. It is supplied to the retarding chamber S2. At this time, the oil in the advance chamber S1 is discharged from the advance chamber S1, and the rotor 34 rotates relative to the housing 32 in the direction of the black arrow R (the retard side) in the figure. .

  Thus, the phase adjustment valve 36 can supply the hydraulic pressure supplied from the oil pump P to each hydraulic chamber by selecting the hydraulic pressure supply line that communicates according to the operating state of the engine 10.

  Here, it is desirable that the opening / closing timing of the intake side valve 24a is changed according to the operating state of the engine 10. That is, by continuously changing the opening / closing timing of the intake side valve 24a, the period of valve overlap (a state in which both the intake side valve 24a and the exhaust side valve 24b are opened) can be adjusted. In addition, the charging efficiency of the air-fuel mixture in the combustion chamber can be increased according to the operating state of the engine 10.

  The variable valve timing mechanism 30 continuously changes the opening / closing timing of the valve 24 by adjusting the phase difference between the crankshaft 12 (housing 32) and the camshaft 16 (rotor 34). Here, when the variable valve timing mechanism 30 adjusts the rotor 34 to the advance side or the retard side with respect to the housing 32, the speed at which the rotor 34 rotates (moves) to a predetermined position on the advance side or the retard side. There is a difference between the advance side response speed and the retard side response speed. Specifically, the advance side response speed is delayed compared to the retard side response speed due to the mechanical loss of the variable valve timing mechanism 30 itself and the frictional resistance generated between the camshaft 16 and the bearing. Therefore, in order to suppress the difference between the advance side response speed and the retard side response speed, the variable valve timing device 26 is provided with an urging member 40 that constantly applies an urging force to the advance side.

  FIG. 3 is a perspective view showing the appearance of the variable valve timing device 26. 3A illustrates the configuration of the variable valve timing device 26, and FIG. 3B illustrates a state in which a part of the variable valve timing device 26 is disassembled. 3 indicate the direction of rotation of the variable valve timing device 26 by the timing chain 20 (not shown).

  As shown in FIGS. 3A and 3B, the urging member 40 is, for example, a spiral spring in which a plate-like member is spirally wound, and the axial direction of the casing 32b provided in the housing 32 Is disposed on the outer surface 32c. In the biasing member 40, the one end 40a is locked to a part of the rotor 34 (see FIG. 2) in the vicinity of the center of the outer surface 32c while the biasing force is stored, and the other end 40b is the casing 32b. The projection 32d is formed in the vicinity of the edge of the outer surface 32c. In the urging member 40, one end 40a applies an urging force in the rotational direction (solid arrow in the drawing) to the rotor 34, and the other end 40b urges the housing 32 in the reverse direction (broken arrow in the drawing). give.

  Due to the urging force of the urging member 40, the advance side response speed of the variable valve timing device 26 is improved, and the retard side response speed is lowered. However, if the urging member 40 is simply provided, the urging force of the urging member 40 is reduced by friction caused by contact between the portions of the urging member 40, and the originally desired urging force is applied to the rotor 34. I can't let you. Therefore, in the present embodiment, the variable valve timing device 26 is provided with friction reducing means 42.

  As shown in FIG.3 (b), the friction reduction means 42 is standingly arranged toward the axial direction from the base part 42b, the base part 42b integrally formed with the flat body part 42a, the main body part 42a, And a plurality (four in this embodiment) of contact prevention walls 42c having a predetermined curvature along the biasing member 40 wound in a state where the biasing force is stored. The main body portion 42 a and the base portion 42 b are provided between the outer surface 32 c and the biasing member 40. The contact prevention wall 42 c is provided between the members in the urging member 40. Specifically, the contact prevention wall 42c is located within a range where the urging members 40 abut against each other by the urging force when the urging force of the urging member 40 itself is stored. It arrange | positions in the state which pinched the plate-shaped site | part, and produces | generates the predetermined | prescribed space | gap with respect to the urging | biasing member 40 in radial direction. Here, the friction reducing means 42 is a member having a material whose friction coefficient is smaller than that of the surface of the urging member 40, and portions (here, plate-like members) that contribute to urging in the urging member 40. Reduces friction caused by contact.

  FIG. 4 is a diagram showing changes in the advance side response speed and the retard side response speed due to the provision of the friction reducing means 42. In FIG. 4, the vertical axis indicates the response speed (deg / sec), and the horizontal axis indicates the engine speed (rpm). Further, the square plot shows the advance side response speed, and the round plot shows the retard side response speed. In each plot, a white plot indicates a case where the friction reducing means 42 is installed, and a black plot indicates a case where the friction reducing means 42 is not installed.

  As indicated by arrows in FIG. 4, the friction reducing means 42 suppresses the friction that reduces the urging force in the rotational direction applied by the urging member 40, so that the advance side response speed is the friction reducing means 42. Is higher than when not installed. On the other hand, since the biasing force in the rotational direction applied by the biasing member 40 is increased by the friction reducing means 42, the retard side response speed is lower than when the friction reducing means 42 is not installed. As can be understood with reference to FIG. 4, in the case of only the urging member 40 (the friction reducing means 42 is not installed) (black plot in the figure), the advance side response speed and the retard side response speed are The difference became large, and it was necessary to suppress the difference between the advance side response speed and the retard side response speed by using a spring having a higher elastic modulus. However, even when the same biasing member 40 is used by installing the friction reducing means 42, the difference between the advance side response speed and the retard side response speed is suppressed as shown by the white plot in the figure. be able to. In other words, the friction reducing means 42 can cause the urging force originally desired by the urging member 40 to act on the rotor 34.

  As described above, the variable valve timing device 26 of the present embodiment prevents the urging force of the urging member 40 from being reduced by providing the friction reducing means 42, and employs a spring having an unnecessarily high elastic coefficient. Even if not, the difference between the advance side response speed and the retard side response speed can be suppressed.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and various modifications within the scope described in the claims. Needless to say, the modified examples also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the friction reducing means 42 is a member having a material having a smaller friction coefficient than the surface of the biasing member 40. However, the present invention is not limited to this, and a material having a friction coefficient smaller than that of the surface of the urging member 40 is present at least at a position facing the surface of the urging member 40 of the contact prevention wall 42c erected on the friction reducing means 42. If you do.

  In the above-described embodiment, the friction reducing member 42 is described as an example of the friction reducing unit 42. However, the invention is not limited thereto, and the opposing surfaces of the spiral spring that is the urging member 40 may be polished.

  In the above-described embodiment, the variable valve timing mechanism 30 is driven by an oil pressure. However, the present invention is not limited to this. For example, the variable valve timing mechanism 30 may be driven by an electromagnetic force such as a solenoid.

  In the embodiment described above, the power transmission member is the timing chain 20, but the present invention is not limited to this, and various members that transmit power, such as a timing belt, can be applied.

  The present invention can be used for a variable valve timing device provided in an engine.

12 Crankshaft 16 Camshaft 20 Timing chain (power transmission member)
26 Variable valve timing device 30 Variable valve timing mechanism 32 Housing (first rotating part)
34 Rotor (second rotating part)
40 Biasing member 42 Friction reducing means

Claims (5)

A first rotating part to which rotational power is transmitted from the crankshaft through a power transmission member; a second rotating part having the same rotating axis as the first rotating part and connected to the camshaft; A variable valve timing mechanism that adjusts a phase difference between the first rotating unit and the second rotating unit;
An urging member for urging the second rotating portion in the rotation direction of the camshaft with respect to the first rotating portion;
Friction reducing means for reducing friction due to contact between parts contributing to urging in the urging member;
A variable valve timing device comprising:   The variable valve timing device according to claim 1, wherein the biasing member is a spiral spring in which a plate-like member is spirally wound.   The friction reducing means is a friction reducing member located between plate members of the spiral spring and having a material having a smaller coefficient of friction than the surface of the spiral spring at a position facing the surface of the spiral spring. The variable valve timing device according to claim 2.   The variable valve timing device according to claim 2, wherein the friction reducing means is formed by polishing opposing surfaces of the spiral spring.   The friction reducing means is located in a range where the spiral springs are in contact with each other by the biasing force of the spiral spring itself when the spiral spring is disposed in a state where the biasing force is stored. The variable valve timing device according to any one of claims 2 to 4.

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