JP2006299915A - Variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a variation in a valve lift quantity between cylinders, by excluding influence by a thermal expansion difference between a housing and a control shaft. <P>SOLUTION: A support pipe 62 is supported by the housing 11 of a variable valve train 10, and the control shaft 64 is inserted into its inside. Four variable devices 58 are arranged on the support pipe 62, and a slider 70 is connected to the control shaft 64 by a pin 66. The slider 70 is driven by the control shaft 64, and a phase of an output member 69 to an input member 68 is changed, and a lift quantity of an intake valve is changed. A linear expansion coefficient of the support pipe 62 and the control shaft 64 is equalized, and a collar 14 and a pin 15 for positioning the output member 69 are arranged on the support pipe 62, and the collar 14 is slidably installed on a bearing wall 12 of the housing 11. <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. 8 and 9, 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.

  A housing 51 of the variable valve mechanism 50 is installed on the cylinder head 3. An intake camshaft 52, an exhaust camshaft 53, and a support pipe 62 are supported on the housing 51, and the camshafts 52 and 53 are connected to a crankshaft 54 via a chain 60. The exhaust camshaft 53 is provided with two exhaust cams 55 for each cylinder 4. 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. The intake cam 57 opens and closes the intake valve 7 via the variable device 58 and the rocker arm 59 so that the lift amount can be changed.

  As shown in FIGS. 9, 10, and 13, in the variable device 58, the same number of four units as the cylinders 4 are arranged on the control shaft 64 via the support pipe 62. The support pipe 62 is supported by the standing wall portion 61 of the housing 51, and a control shaft 64 is slidably inserted inside the support pipe 62. One end of the control shaft 64 is connected to an actuator 65 having a built-in hydraulic piston, and a pin 66 of the 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 in addition to the pin 66. 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. 8). 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 is inserted into the circumferential long hole 74 of the slider 70 through the axial long hole 73 of the support pipe 62, and the slider 70 is driven in the axial direction of the control shaft 64 by the pin 66.

  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 are swung 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. 10, 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.

Further, when the slider 70 moves in the direction of the arrow R in FIG. 10, the relative phase difference θ2 between the input member 68 and the output member 69 is reduced, 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 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. 9) 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. 13, when the temperature of the cylinder head 3 changes by ΔT ° C. with the # 1 variable device 58 closest to the reference position (center position of the actuator 65), it is connected to the control shaft 64. A relative displacement amount A calculated by the following equation is generated between the slider 70 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, eliminates the influence of a difference in thermal expansion between a housing and a control shaft, and can eliminate variation in valve lift between cylinders.

  In order to solve the above problems, the present invention has a housing installed in a cylinder head of an internal combustion engine, supports a camshaft and a control shaft on the housing, and arranges variable devices on the control shaft in the same number as the cylinder The variable device is provided with an input member that engages with the cam on the camshaft, an output member that opens and closes the valve, a slider that interlocks the output member with the input member, and a connecting member that connects the slider to the control shaft. A variable valve mechanism that moves in the axial direction of the shaft by the control shaft, changes the phase of the output member with respect to the input member by the slider, and changes the lift amount of the valve. Support with substantially the same linear expansion coefficient as the control shaft And a control shaft is slidably inserted inside the support member. The positioning member for positioning the output member to the outer member is provided, characterized in that assembled to be movable in the axial direction of the control shaft positioning member to the housing.

  Here, as the support member, for example, a pipe-shaped member made of a material (for example, a steel material) having substantially the same linear expansion coefficient as that of the control shaft (for example, a steel material) can be used. The positioning member may be formed integrally with the support member, or a member separate from the support member may be used. When a separate member is used, there is an advantage that the variable device can be easily assembled on the support member. Specifically, the positioning member is provided with a cylindrical portion separate from the support member and a locking portion for locking the cylindrical portion to the support member, and the cylindrical portion is inserted into the outer periphery of the support member. It is preferable that the output member is fixed to a fixed position on the support member via the cylindrical portion by the stopper. As the cylindrical portion, for example, a bearing part such as a collar or a bush can be used. As the locking portion, for example, a pin, a snap ring (retaining ring), a set screw, or the like can be used.

  In the above description, “the control shaft and the support member have substantially the same linear expansion coefficient” means that the relative displacement between the slider and the output member is such that the cylinder has an adverse effect on the fuel consumption, emission, vibration, etc. of the engine. It means that it is suppressed below the linear expansion coefficient difference to such an extent that no interdifference occurs. Specifically, the difference in linear expansion coefficient is preferably 30% or less, and more preferably 10% or less. Such a preferable state can be obtained, for example, by manufacturing both the control shaft and the support member with a steel material. Here, both steel materials are not limited to steel materials having exactly the same alloy composition, and both of them may have different alloy compositions as long as they are iron-based steel materials (the difference in thermal expansion between them is Can be ignored).

  According to the variable valve mechanism of the present invention, since the output member of the variable device is positioned on the support member by the positioning member, the output member is displaced with the thermal expansion of the support member. However, since the support member and the control shaft have substantially the same linear expansion coefficient, the displacement amount of the output member due to the elongation of the support member is equal to the displacement amount of the slider due to the elongation of the control shaft. Further, since the positioning member is movably assembled to the housing, the thermal expansion difference between the housing and the support member is absorbed by the positioning member, and the positions of the output member and the slider are not affected. For this reason, the relative positions of the output member and the slider can be made equal in all the variable devices, and the variation in the valve lift amount between the cylinders can be eliminated.

  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 10 of this embodiment is installed in a four-cylinder gasoline engine 1 (see FIG. 8) for automobiles, as in the prior art. The cylinder head 3 of the engine 1 is provided with a housing 11 for a variable valve mechanism 10. The housing 11 is made of an aluminum material in a box shape, and the intake camshaft 52, the exhaust camshaft 53, and the support pipe 62 are supported in parallel on the five bearing walls 12 of the housing 11. A steel control shaft 64 is inserted inside the support pipe 62, and a hydraulic actuator 13 that drives the shaft 64 is installed on the end wall portion 11 a of the housing 11.

  On the control shaft 64, the same number (four) of variable devices 58 as the cylinders 4 are arranged via support pipes 62. 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 for connecting the slider 70 to the control shaft 64. The variable valve mechanism 10 moves the slider 70 in the axial direction by the control shaft 64 with the output member 69 positioned in the axial direction of the control shaft 64, and the slider 70 moves the phase of the output member 69 relative to the input member 68. And the lift amount of the intake valve 7 is changed.

  The variable valve mechanism 10 of this embodiment is different from the conventional variable valve mechanism 50 in the configuration for positioning the output member 69. The support pipe 62 of the variable valve mechanism 10 is made of steel and has a linear expansion coefficient substantially equal to that of the control shaft 64. A control shaft 64 is slidably inserted inside the support pipe 62, and the support pipe 62 functions as a support member for the control shaft 64. A positioning member that positions the output member 69 so as not to move in the axial direction of the control shaft 64 is provided outside the support pipe 62.

  The positioning member includes a cylindrical collar 14 inserted on the outer periphery of the support pipe 62, and a pin 15 as a locking portion that fixes the output member 69 to a fixed position on the support pipe 62 via the collar 14. Yes. The collar 14 is held by each bearing wall 12 of the housing 11 and is assembled so as to be slidable in the axial direction of the control shaft 64. Hereinafter, the positioning member and the assembly structure thereof will be described in detail with reference to two examples.

  As shown in FIGS. 2 to 5, in the variable valve mechanism 10 of the first embodiment, the five collars 14 are inserted into the outer periphery of the support pipe 62 so as to sandwich the four variable devices 58 from the left and right. . The same number of pins 15 as the collar 14 are fixed to the hole 62a of the support pipe 62 by means such as press-fitting or screwing so as to contact the left end surface of the collar 14. A horseshoe shim 16 for adjusting a gap is interposed between the collar 14 and the output member 69 in a replaceable manner. The collar 14, the shim 16, and the variable device 58 are disposed between the two adjacent pins 15 without any gap, and the pair of output members 69 of the variable device 58 are connected to the pin 15 via the collar 14 and the shim 16. It is fixed at a fixed position on the support pipe 62.

  A shaft retainer 17 is assembled to the bearing wall 12 of the housing 11 so as to be disassembled by a bolt 18. A bearing hole 19 (see FIG. 4) is formed between the bearing wall 12 and the shaft retainer 17, and the collar 14 is assembled in the bearing hole 19 so as to be slidable in the axial direction of the control shaft 64. A bearing hole (not shown) through which the intake camshaft 52 and the exhaust camshaft 53 are passed is also formed between the bearing wall 12 and the shaft retainer 17. Four pins 15 except for the left end are accommodated in the open portion 16 a of the horseshoe shim 16.

  In the variable valve mechanism 10 of the first embodiment, as shown in FIG. 5A, the four variable devices 58 are equal in relative distance between the slider 70 and the output member 69 at a reference temperature (for example, 80 ° C.). (L1 = L2 = L3 = L4). When the engine 1 generates heat, the housing 11, the support pipe 62, and the control shaft 64 are thermally expanded as shown in FIG. 5B. At this time, since the variable device 58 is fixed on the support pipe 62 by the pin 15 via the collar 14 and the shim 16, the output member 69 is displaced with the extension of the support pipe 62 (maximum displacement amount Do). Further, since the slider 70 is connected to the control shaft 64 by the pin 66, the slider 70 is also displaced by the extension of the control shaft 64 (maximum displacement amount Ds).

  However, since the support pipe 62 and the control shaft 64 are made of steel and have substantially the same linear expansion coefficient, the displacement amount of the output member 69 due to the elongation of the support pipe 62 and the displacement amount of the slider 70 due to the elongation of the control shaft 64. Are equal (Do = Ds). In addition, since the collar 14 is slidably assembled to the bearing wall 12 of the housing 11, the difference in thermal expansion (Eh−Ep) between the housing 11 and the support pipe 62 is absorbed by the collar 14, and the output member 69 and the slider 70. Will no longer affect the position of For this reason, the relative distance between the output member 69 and the slider 70 is kept the same in all the variable devices 58 (L1 = L2 = L3 = L4), and the variation in the valve lift amount between the cylinders can be eliminated. Can improve fuel consumption, emission, vibration, etc.

  As shown in FIGS. 6 and 7, the positioning member of Example 2 includes a collar 14 as a cylindrical portion and a snap ring 21 as a locking portion. The collar 14 is inserted into the outer periphery of the support pipe 62 as in the first embodiment. The same number of five snap rings 21 as the collar 14 are engaged with the groove 62 b of the support pipe 62 in a state where the snap ring 21 is joined to the left end surface of the collar 14. The collar 14, the shim 16, and the variable device 58 are disposed between the two adjacent snap rings 21 without any gap, and the output member 69 of the variable device 58 is interposed between the collar 14 and the shim 16 by the snap ring 21. It is fixed at a fixed position on the support pipe 62. In addition to the C-shaped ring shown in FIG. 7, various detachable retaining rings such as an E-shaped ring and a U-shaped ring can be used for the snap ring 21. Other configurations and operational effects are the same as those of 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 perspective view of a variable device and a positioning member. It is operation | movement explanatory drawing of a variable valve mechanism. It is a fragmentary sectional view of the variable valve mechanism which shows Example 2 of this invention. It is the VII-VII sectional view taken on the line of FIG. 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 variable apparatus of the conventional variable valve mechanism. It is operation | movement explanatory drawing when a variable apparatus expands valve lift amount. It is operation | movement explanatory drawing when a variable apparatus reduces the 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)
11 Housing 13 Actuator 14 Color 15 Pin 20 Variable Valve Mechanism (Embodiment 2)
21 Snap Ring 52 Intake Cam Shaft 57 Intake Cam 58 Variable Device 64 Control Shaft 66 Pin 68 Input Member 69 Output Member 70 Slider

Claims (1)

An input member for installing a housing on a cylinder head of an internal combustion engine, providing a camshaft and a control shaft on the housing, arranging the same number of variable devices as the cylinder on the control shaft, and engaging the variable device with a cam on the camshaft. And an output member for opening and closing the valve, a slider for interlocking the output member with the input member, and a connecting member for connecting the slider to the control shaft. The slider is moved in the axial direction of the shaft by the control shaft, In the variable valve mechanism that changes the lift amount of the valve by changing the phase of the output member with respect to the input member,
A support member having substantially the same linear expansion coefficient as that of the control shaft is provided. The control shaft is slidably inserted inside the support member, and a positioning member for positioning the output member is provided outside the support member. A variable valve mechanism that is assembled to be movable in the axial direction of the control shaft.

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