JP2006300005A - Variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain a variation in a valve lift quantity between cylinders, by reducing influence by a thermal expansion difference between a housing and a control shaft. <P>SOLUTION: The housing 11 is arranged in a cylinder head 3, and the control shaft 14 is supported by a bearing wall 12 of the housing 11 via a support pipe 13. Four variable devices 58 are arranged on the control shaft 14, and its output member 69 is positioned by the bearing wall 12. An actuator 15 is arranged in a central part of the housing 11, and a lever 21 is arranged in its output part. The lever 21 is connected to the control shaft 14 in an intermediate part of the two variable devices 58 positioned in a central part of the housing 11. A slider 70 is driven via a pin 66 by the movement of the control shaft 14, and a phase of the output member 69 to an input member 68 is changed, and the lift quantity of an intake valve is changed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable valve mechanism that opens and closes a valve of an internal combustion engine in a variable amount of lift.

  Conventionally, an internal combustion engine for automobiles has a function to change the lift amount of the intake valve according to the engine speed in order to improve fuel efficiency at low speed and low load and increase output at high speed and high load. A variable valve mechanism is known. For example, Patent Document 1 describes a variable valve mechanism for an automobile gasoline engine. As shown in FIGS. 5 and 6, the engine 1 includes four cylinders 4 between a cylinder block 2 and a cylinder head 3. In each cylinder 4, a piston 6 is accommodated in the combustion chamber 5 of the cylinder block 2, and two intake valves 7 and two exhaust valves 8 are provided in the cylinder head 3.

  The variable valve mechanism 50 includes a housing 51 on the cylinder head 3. An intake camshaft 52 and an exhaust camshaft 53 are supported on the housing 51, and both are driven by a crankshaft 54 via a chain 60. The exhaust camshaft 53 is provided with two exhaust cams 55 for each cylinder 4, and the exhaust cam 55 opens and closes the exhaust valve 8 through a rocker arm 56 with a constant lift amount. The intake camshaft 52 is provided with one intake cam 57 for each cylinder 4, and the intake cam 7 is opened and closed via the variable device 58 and the rocker arm 59 so that the lift amount can be changed.

  As shown in FIGS. 7, 8, and 9, the variable device 58 is provided on the support pipe 62, and the support pipe 62 is supported by the standing wall 61 of the housing 51. A control shaft 64 is slidably inserted inside the support pipe 62, one end of which is connected to an actuator 65 containing a hydraulic piston, and a pin 66 for each variable device 58 projects from an intermediate portion. Then, the actuator 65 is controlled by the electronic control unit of the automobile, the control shaft 64 is driven in the axial direction by the actuator 65, and the variable device 58 is operated by the pin 66.

  The variable device 58 includes an input member 68, an output member 69, and a slider 70. The input member 68 is provided with a roller 71 that engages with the intake cam 57, and the output member 69 is provided with a cam piece 72 that engages with a rocker arm 59 (see FIG. 5). The input member 68 and the output member 69 are swingably supported on the support pipe 62, and sliding in the axial direction is restricted by the left and right standing wall portions 61. The slider 70 is slidably supported by the support pipe 62 inside the input member 68 and the output member 69. Then, the pin 66 passes through the axial long hole 73 of the support pipe 62 and fits into the circumferential long hole 74 of the slider 70, and the slider 70 is driven by the pin 66 in the axial direction of the control shaft 64.

  The input member 68 and the slider 70 are engaged with each other by the input side spline 75, and the slider 70 and the output member 69 are engaged with each other by the output side spline 76. The spline 75 and the spline 76 are twisted in opposite directions in the left-right direction, and the input member 68 and the output member 69 swing in opposite directions as the slider 70 moves in the axial direction. When the slider 70 moves in the direction of arrow F in FIG. 7, the relative phase difference θ1 between the input member 68 and the output member 69 increases as shown in FIG. In this state, as shown in (b), when the input member 68 is swung by the intake cam 57, the output member 69 is swung at the same angle as the input member 68 via the slider 70, and the rocker arm 59 is moved. The intake valve 7 is opened and closed with a large lift amount R1.

When the slider 70 moves in the direction of arrow R in FIG. 7, the relative phase difference θ2 between the input member 68 and the output member 69 is reduced as shown in FIG. 9A. In this state, as shown in (b), when the input member 68 is swung by the intake cam 57, the output member 69 opens and closes the intake valve 7 with a small lift amount R2 via the rocker arm 59. Therefore, the lift amount of the intake valve 7 can be continuously changed by controlling the movement amount of the slider 70 by the control shaft 64 and changing the phase of the output member 69 with respect to the input member 68. An actuator 77 (see FIG. 6) for adjusting the rotational phase difference of the intake cam 57 with respect to the crankshaft 54 is provided at one end of the intake camshaft 52.
JP 2001-263015 A

  According to the conventional variable valve mechanism 50 configured as described above, since the slider 70 of the variable device 58 provided for each cylinder 4 is controlled by the common control shaft 64, the valve lift amount can be reduced with a compact configuration. Can be controlled. However, according to this configuration, since the position of the slider 70 with respect to the output member 69 is affected by the thermal expansion of the valve operating system parts, it is difficult to always make the outputs of the four variable devices 58 equal. That is, when there is a difference between the thermal expansion amount of the housing 51 that positions the output member 69 and the thermal expansion amount of the control shaft 64 that drives the slider 70, the valve lift amount differs for each variable device 58. was there.

Usually, the housing 51 is made of a light aluminum material having a large linear expansion coefficient, and the control shaft 64 is made of a steel material having high rigidity and a small linear expansion coefficient. When these materials are used, as shown in FIG. 10, the temperature of the cylinder head 3 changes by ΔT ° C. at the # 1 variable device 58 closest to the control reference position of the control shaft 64 (center position of the actuator 65). Then, a relative displacement amount A calculated by the following equation is generated between the slider 70 connected to the control shaft 64 and the output member 69 positioned in the housing 51.
A = (P1 × αsteel−S1 × αaluminium) × ΔT
P1: Distance from the reference position to the pin 66 S1: Distance from the reference position to the standing wall 61 αsteel: Linear expansion coefficient of steel material αaluminium: Linear expansion coefficient of aluminum material

  Here, the relative displacement amounts of the slider 70 and the output member 69 in the four variable devices 58 (# 1 to # 4) have different slopes as the temperature of the cylinder head 3 changes as shown in FIG. Change. For example, when the relative displacement amount of each device 58 is set to 0 at a reference temperature of 80 ° C., a relative displacement amount of D1 is generated with an average of four units near the upper limit of the operating temperature range (eg, 110 ° C.). Further, a difference of D2 occurs between # 1 closest to the reference position and # 4 farthest from the reference position. Therefore, even if the four variable devices 58 are assembled with the same valve lift amount, the operating angles of the four output members 69 differ due to the difference in thermal expansion between the housing 51 and the control shaft 64, and the valve lift amount between the cylinders. There is a problem that the fuel consumption, emission, vibration and the like of the engine 1 are adversely affected.

  An object of the present invention is to provide a variable valve mechanism that solves the above-described problems, reduces the influence due to the difference in thermal expansion between the housing and the control shaft, and can suppress variation in the valve lift amount between the cylinders. .

  In order to solve the above problems, the present invention provides a housing in a cylinder head of an internal combustion engine, supports a camshaft and a control shaft in the housing, and arranges variable devices as many as the cylinders on the control shaft. The apparatus is provided with an input member that engages a cam on the camshaft, an output member that opens and closes a valve of the internal combustion engine, a slider that interlocks the output member with the input member, and a connecting member that connects the slider to the control shaft, In the variable valve mechanism that changes the lift amount of the valve by driving the control shaft by the actuator and changing the phase of the output member with respect to the input member by the slider while the output member is positioned in the housing. Control shaft near the variable device located in the middle of the And wherein the linked.

  Here, an electric motor, an electromagnetic solenoid, a fluid pressure cylinder, or the like can be used as the actuator. The installation location of the actuator is not particularly limited, and may be the end of the housing or the center of the housing. However, in order to suppress the thermal expansion of the power transmission system of the actuator, it is preferable to install the actuator in the center in the longitudinal direction of the housing to shorten the power transmission path. Specifically, in a four-cylinder or six-cylinder engine, it is possible to employ a configuration in which an actuator is installed at a substantially central portion of the housing and an output portion of the actuator is connected to a central portion in the axial direction of the control shaft. In addition, as a power transmission means, a cam, a gear transmission mechanism, a winding transmission mechanism, a link mechanism, etc. can be used, for example.

  According to the variable valve mechanism of the present invention, since the output portion of the actuator is connected to the control shaft near the variable device located in the central portion of the housing, the position serving as the control reference for the control shaft is the center in the axial direction of the shaft. Set close. For this reason, the amount of thermal expansion of the housing and the control shaft from the reference position is reduced as compared with the conventional case, and the influence of both thermal expansion differences is mitigated. Therefore, it is possible to reduce the difference in the relative displacement amount between the output member positioned in the housing and the slider connected to the control shaft, and to suppress the variation in the valve lift amount between the cylinders.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the variable valve mechanism of this embodiment is mounted on a four-cylinder gasoline engine 1 (see FIG. 8) for automobiles as in the conventional case. The cylinder head 3 of the engine 1 is provided with a variable valve mechanism housing 11. The housing 11 is manufactured in a box shape from an aluminum alloy material, and the intake camshaft 52, the exhaust camshaft 53, and the support pipe 13 are supported in parallel on the bearing wall 12 of the housing 11. A steel control shaft 14 is slidably inserted inside the support pipe 13, and the same number (four) of variable devices 58 as the cylinders 4 are arranged on the shaft 14.

  The variable device 58 includes an input member 68 that engages with the intake cam 57 on the intake camshaft 52, a pair of output members 69 that open and close the intake valve 7, a slider 70 that interlocks the output member 69 with the input member 68, And a pin 66 as a connecting member for connecting the slider 70 to the control shaft 14. The variable valve mechanism 10 drives the control shaft 14 by the actuator 15 while the output member 69 is positioned by the bearing wall 12 of the housing 11, and changes the phase of the output member 69 relative to the input member 68 by the slider 70. The lift amount of the intake valve 7 is changed.

  The variable valve mechanism of this embodiment is different from the conventional variable valve mechanism 50 in the configuration of the actuator 15 and its power transmission means. In the variable valve mechanism of this embodiment, the actuator 15 is installed in the center portion in the longitudinal direction of the housing 11, and the output portion is connected to the control shaft 14 at an intermediate portion between the two variable devices 58 located in the center portion of the housing 11. Has been. This characteristic configuration will be described in detail below with reference to two examples.

  As shown in FIGS. 1 to 3, the variable valve mechanism 10 according to the first embodiment includes eight bearing walls 12 in a housing 11. A shaft retainer 16 is assembled on each bearing wall 12 so as to be disassembled with a bolt 17. A bearing hole 18 that supports the support pipe 13, the intake camshaft 52, and the exhaust camshaft 53 is formed between the bearing wall 12 and the shaft retainer 16. The support pipe 13 is divided into two at the longitudinal center portion of the housing 11, and opposite ends are fixed to the two bearing walls 12 by bolts 19. A single control shaft 14 is inserted inside the support pipe 13 so as to be slidable in the axial direction.

  The actuator 15 is installed on a shaft presser 16 located at the center of the housing 11, and a lever 21 is provided at the output of the actuator 15. The lever 21 is connected to the control shaft 14 by a pin 22 at an intermediate portion between the two variable devices 58 located at the center of the housing 11, and the control shaft 14 is driven to reciprocate in the axial direction by the swing of the lever 21. The A horseshoe-shaped shim 27 for adjusting a gap is interposed between the bearing wall 12 and the output member 69 so as to be replaceable.

  According to the variable valve mechanism 10 having the above configuration, the lever 21 of the actuator 15 is connected to the control shaft 14 at the center of the housing 11, so that the position serving as the control reference for the control shaft 14 is set at the center in the axial direction. The Therefore, as shown in FIG. 2, in the four variable devices 58, the distance from the reference position to the pin 66 (P1 = P2 <P3 = P4) and the distance from the reference position to the bearing wall 12 (S1 = S2 < S3 = S4) is shorter than the conventional one (see FIG. 10). Therefore, the influence due to the difference in thermal expansion between the housing 11 and the control shaft 14 is reduced, and particularly in the variable device 58 at both ends, it is reduced to about half of the conventional one. As a result, the difference in relative displacement between the output member 69 positioned in the housing 11 and the slider 70 connected to the control shaft 14 is halved, and variation in the valve lift between the cylinders is suppressed. 1 fuel consumption, emission, vibration and the like can be improved.

  As shown in FIG. 4, the variable valve mechanism 30 of the second embodiment includes five bearing walls 12 in the housing 11, and an actuator 31 is installed on the shaft retainer 16 located in the center of the housing 11. The output shaft 32 of the actuator 31 is connected to the central portion in the axial direction of the control shaft 14 via a worm 33 and a worm wheel 34. As the output shaft 32 rotates, the control shaft 14 rotates forward and backward around the axis.

  The control shaft 14 is provided with a male screw 35 at a position corresponding to the four variable devices 58. A cylindrical holder 36 is interposed between the control shaft 14 and the support pipe 13, a female screw 37 is formed on the inner peripheral surface of the holder 36, and the variable device 58 is formed on the outer peripheral surface of the holder 36. The pin 66 is erected. The pin 66 is reciprocally driven on the control shaft 14 in the axial direction by forward and reverse rotation of the control shaft 14.

  Accordingly, also with this variable valve mechanism 30, since the output shaft 32 of the actuator 15 is connected to the control shaft 14 at the center of the housing 11 as in the first embodiment, the distance from the reference position to the pin 66 (P1 = P2 <P3 = P4) and the distance from the reference position to the bearing wall 12 (S1 = S2 <S3 = S4) can be shortened, and the influence of the difference in thermal expansion between the housing 11 and the control shaft 14 can be reduced. In particular, since the power transmission means is configured so that the control shaft 14 does not move in the axial direction, there is an advantage that the overall length of the housing 11 can be shortened and the influence due to the difference in thermal expansion can be reduced as compared with the first embodiment.

It is a top view of the variable valve mechanism which shows Example 1 of this invention. It is the II-II sectional view taken on the line of FIG. It is the III-III sectional view taken on the line of FIG. It is a top view of the variable valve mechanism which shows Example 2 of this invention. It is sectional drawing of the gasoline engine for motor vehicles. It is a top view of the conventional variable valve mechanism. It is a perspective view which shows the assembly | attachment structure of a variable apparatus. It is operation | movement explanatory drawing when enlarging valve lift amount. It is operation | movement explanatory drawing when reducing valve lift amount. It is sectional drawing of the conventional variable valve mechanism. It is a graph which shows the temperature characteristic of the conventional variable valve mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasoline engine 3 Cylinder head 4 Cylinder 7 Intake valve 10 Variable valve mechanism (Example 1)
DESCRIPTION OF SYMBOLS 11 Housing 12 Bearing wall 14 Control shaft 15 Actuator 21 Lever 30 Variable valve mechanism (Example 2)
31 Actuator 32 Output Shaft 52 Intake Cam Shaft 57 Intake Cam 58 Variable Device 66 Pin 68 Input Member 69 Output Member 70 Slider

Claims (1)

An input member that installs a housing on a cylinder head of an internal combustion engine, supports a camshaft and a control shaft on the housing, arranges variable devices as many as the cylinders on the control shaft, and engages the cams on the camshaft with the variable devices And an output member that opens and closes a valve of the internal combustion engine, a slider that interlocks the output member with the input member, and a connecting member that connects the slider to the control shaft, and is controlled by the actuator while the output member is positioned on the housing. In the variable valve mechanism that drives the shaft and changes the lift amount of the valve by changing the phase of the output member relative to the input member by the slider,
A variable valve mechanism characterized in that an output portion of the actuator is connected to a control shaft near a variable device located in a central portion of the housing.

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