JP2012082793A - Variable valve system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary an angle of action and a lift amount of a valve by a simple mechanism, concerning a variable valve system of an internal combustion engine.SOLUTION: The variable valve system 10 of the internal combustion engine includes: a valve 2 disposed in a cylinder of the internal combustion engine; a camshaft 3; an eccentric cam bearing 7 that is rotatably disposed and receives the camshaft 3 at a position offset from a rotation center thereof; a driving device for rotating the eccentric cam bearing 7; a rocker arm 4 that receives a lift of a cam 31 disposed on the camshaft 3 and presses the valve 2 to open the valve; and a supporting mechanism 5 for supporting a fulcrum of the rocker arm 4. The rotation of the eccentric cam bearing 7 moves a position of the rotation center C2 of the camshaft 3, and thereby making the angle of action and the lift amount of the valve 2 variable.

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine.

  Various mechanisms have been proposed as variable valve gears that can change the operating angle and lift amount of an intake valve or an exhaust valve provided in a cylinder of an internal combustion engine (see, for example, Patent Document 1).

JP 2005-127228 A JP 2009-236105 A

  However, the conventionally proposed variable valve operating device with variable working angle and lift amount has a complicated structure and a large number of parts, and thus has a problem of increasing size and cost. For example, the one described in Patent Document 1 has a complicated mechanism in which parts such as a first link and a second link are interposed between a cam and a valve. For this reason, in addition to the above-mentioned problems, the tolerances of a large number of parts interposed between the cam and the valve are piled up to increase the error, resulting in variations in the lift amount, and the lift amounts do not match among the cylinders. There is also.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a variable valve operating apparatus for an internal combustion engine that can change the valve operating angle and the lift amount with a simple mechanism. And

In order to achieve the above object, a first invention is a variable valve operating apparatus for an internal combustion engine,
A valve provided in a cylinder of the internal combustion engine;
A camshaft provided with a cam;
An eccentric cam bearing that is rotatably installed and receives the cam shaft at a position eccentric from the rotation center thereof;
A driving device for rotating the eccentric cam bearing;
A rocker arm that receives the lift of the cam and presses and opens the valve;
A support mechanism for supporting a fulcrum of the rocker arm;
With
The valve operating angle and the lift amount are made variable by rotating the eccentric cam bearing to move the position of the rotation center of the cam shaft.

The second invention is the first invention, wherein
The support mechanism includes a biasing unit that biases a fulcrum of the rocker arm in a direction to approach the camshaft.

The third invention is the first or second invention, wherein
The biasing means is a spring.

According to a fourth invention, in any one of the first to third inventions,
The support mechanism includes an impact mitigating means for mitigating an impact when the valve lift starts.

  According to the first invention, the valve operating angle and the lift amount can be changed by a simple mechanism with a small number of parts interposed between the cam and the valve. Cost, durability and reliability can be improved. In addition, since the number of parts interposed between the cam and the valve is small, variations in the lift amount can be suppressed, and the lift amounts can be accurately matched among a plurality of cylinders.

  According to the second invention, by providing the biasing means for biasing the fulcrum of the rocker arm in the direction approaching the cam shaft, the rocker arm is prevented from separating from the cam, and the rocker arm and the cam are always in contact with each other. Can be maintained in a state. For this reason, noise can be suppressed.

  According to the third aspect of the invention, the above effect can be obtained with a simple structure by using a spring as the biasing means.

  According to the fourth aspect of the present invention, it is possible to more reliably suppress noise by providing the impact mitigating means for mitigating the impact when the valve lift starts.

It is a side view which shows the variable valve apparatus of Embodiment 1 of this invention. It is a side view which shows the variable valve apparatus of Embodiment 1 of this invention. It is a figure which shows the eccentric cam bearing and control shaft with which the variable valve apparatus of Embodiment 1 of this invention is provided. It is a figure which shows the eccentric cam bearing and control shaft with which the variable valve apparatus of Embodiment 1 of this invention is provided. It is a figure which shows the eccentric cam bearing and control shaft with which the variable valve apparatus of Embodiment 1 of this invention is provided. It is a side view which shows the variable valve apparatus of Embodiment 1 of this invention. It is a side view which shows the variable valve apparatus of Embodiment 1 of this invention. It is a side view which shows the variable valve apparatus of Embodiment 1 of this invention. It is a side view which shows the variable valve apparatus of Embodiment 1 of this invention. It is a side view which shows the variable valve apparatus of Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
1 and 2 are side views showing a variable valve operating apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the variable valve operating apparatus 10 of the present embodiment receives a valve 2, a cam shaft 3, a rocker arm 4, a support mechanism 5 that supports a fulcrum of the rocker arm 4, and the cam shaft 3. An eccentric cam bearing 7 and a drive device for rotating the eccentric cam bearing 7 are provided. In FIG. 2 and FIGS. 6 to 10 described later, the eccentric cam bearing 7 and its driving device are not shown.

  The valve 2 is provided as an intake valve or an exhaust valve in a cylinder of the internal combustion engine. The valve 2 is urged in the valve closing direction (upward in the figure) by a valve spring (not shown). A cam 31 is provided on the cam shaft 3. Normally, the camshaft 3 is driven by a crankshaft of an internal combustion engine and rotates at a speed that is half that of the crankshaft.

  One end of the rocker arm 4 is supported by a support portion 51 of the support mechanism 5. The rocker arm 4 can swing around an end on the support mechanism 5 side as a fulcrum. The other end of the rocker arm 4 is configured such that the valve 2 can be opened by pressing the valve stem 21 of the valve 2. The rocker arm 4 has a roller 41 that is rotatably installed at the center of the arm body. The roller 41 is in contact with the cam 31. As shown in FIG. 1, when the base circle portion of the cam 31 is in contact with the roller 41, the valve 2 comes into contact with the valve seat 6 by the urging force of the valve spring, and the valve is closed. When the cam 31 rotates from the state shown in FIG. 1, the cam crest of the cam 31 presses the roller 41 and presses the valve stem 21 via the rocker arm 4, so that the valve 2 is lifted and the valve seat 6 is opened and the valve is opened. FIG. 2 shows a state in which the nose of the cam 31 contacts the roller 41 and the valve 2 is fully opened.

  The support mechanism 5 includes a holder 52 fixed to a cylinder head (not shown) of the internal combustion engine, a plunger 53 inserted into a hole formed in the holder 52, and a flange 54 provided at the tip of the plunger 53. The support portion 51 provided on the opposite side of the plunger 53 at the center of the flange 54 and the coil spring 55 disposed on the outer peripheral side of the holder 52 are provided. The plunger 53 can advance and retreat between a state in which the plunger 53 protrudes from the holder 52 and a state in which the plunger 53 is retracted in the holder 52. The support portion 51 and the flange 54 are displaced together with the plunger 53. That is, the support mechanism 5 has a configuration that can be expanded and contracted, and FIGS. 1 and 2 show a state in which the support mechanism 5 is fully contracted. When the support mechanism 5 extends, the support portion 51 approaches the cam shaft 3, and when the support mechanism 5 contracts, the support portion 51 moves away from the cam shaft 3. One end of the coil spring 55 is in contact with the cylinder head, and the other end is in contact with the flange 54. The support mechanism 5 is urged by the coil spring 55 in the extending direction. That is, the support portion 51 serving as a fulcrum of the rocker arm 4 is urged in a direction approaching the cam shaft 3.

  The variable valve operating apparatus 10 of the present embodiment can continuously change the operating angle and the lift amount of the valve 2. 1 and 2 show a state in which the operating angle and lift amount of the valve 2 are maximized (hereinafter referred to as “maximum operating angle state”). In the maximum operating angle state, the support mechanism 5 is maintained in the contracted state.

  3 to 5 are views showing the eccentric cam bearing 7 and the control shaft 8 provided in the variable valve operating apparatus 10 of the present embodiment. As described above, the variable valve operating apparatus 10 of the present embodiment includes the eccentric cam bearing 7 and the drive device that rotates the eccentric cam bearing 7. The eccentric cam bearing 7 of the present embodiment has a substantially cylindrical shape as a schematic shape and is rotatably installed. The eccentric cam bearing 7 is provided with a gear 71. In the present embodiment, the drive device that rotates the eccentric cam bearing 7 includes a control shaft 8 that is rotatably provided and an actuator (not shown) such as an electric motor that rotates the control shaft 8. ing. The control shaft 8 is provided with a gear 81 that meshes with the gear 71 of the eccentric cam bearing 7. When the control shaft 8 is driven to rotate, the rotation is transmitted through the gear 81 and the gear 71, whereby the eccentric cam bearing 7 rotates. The rotation center lines of the eccentric cam bearing 7 and the control shaft 8 are parallel to the rotation center line of the cam shaft 3.

  The eccentric cam bearing 7 is formed with a hole 72 that functions as a bearing for receiving the cam shaft 3. The eccentric cam bearings 7 are provided at a plurality of locations along the cam shaft 3 and support the cam shaft 3 at a plurality of locations. The gear 81 of the control shaft 8 is formed at a plurality of locations corresponding to the plurality of eccentric cam bearings 7 and meshes with the gear 71 of each eccentric cam bearing 7. For this reason, by rotating the control shaft 8, the plurality of eccentric cam bearings 7 can be rotated synchronously.

  The center C2 of the hole 72 (that is, the rotation center of the cam shaft 3) C2 is disposed at a position eccentric from the rotation center C1 of the eccentric cam bearing 7. For this reason, when the eccentric cam bearing 7 is rotated, the rotation center C2 of the cam shaft 3 moves. Although not shown in FIGS. 3 to 5, the roller 41 of the rocker arm 4 is positioned below the cam 31 in the drawings. In the variable valve operating apparatus 10, as the rotation center C <b> 2 of the cam shaft 3 is moved to the roller 41 side, the operating angle and the lift amount of the valve 2 are increased, and the rotation center C <b> 2 of the cam shaft 3 is moved to the opposite side of the roller 41. The more the operation angle and the lift amount of the valve 2 are reduced.

  The state shown in FIG. 3 is a state where the rotation center C2 of the camshaft 3 is moved to the roller 41 side to the maximum, and corresponds to the maximum operating angle state. The state shown in FIG. 5 is a state in which the rotation center C2 of the camshaft 3 is moved to the opposite side to the roller 41 to the maximum, and the operating angle and lift amount of the valve 2 are minimized (hereinafter referred to as “minimum operating angle state”). "). When the variable valve operating apparatus 10 of the present embodiment is in the minimum operating angle state, the operating angle and lift amount of the valve 2 can be set to zero, that is, the valve can be stopped. The state shown in FIG. 4 is an intermediate state between the state shown in FIG. 3 and the state shown in FIG. 5, and the operating angle and lift amount of the valve 2 are intermediate between the maximum and the minimum (hereinafter referred to as “medium operation”). This is referred to as a “corner state”.

  6 and 7 are side views showing the variable valve gear 10 in the medium operating angle state. The state shown in FIG. 6 is a valve-closed state in which the base circle portion of the cam 31 is in contact with the roller 41. In the state shown in FIG. 6, the rotation center C <b> 2 of the cam shaft 3 moves in a direction away from the roller 41 compared to the valve closed state in the large operating angle state shown in FIG. 1. However, the support mechanism 5 is extended by the biasing force of the coil spring 55 and pushes up the fulcrum of the rocker arm 4 so that the contact state between the roller 41 and the base circle portion of the cam 31 is maintained.

  When the cam 31 rotates from the state shown in FIG. 6 and the roller 41 is pressed, the pressing force is transmitted to the support mechanism 5 and the support mechanism 5 contracts. At this time, the valve 2 is not lifted from the valve seat 6 until the support mechanism 5 is fully retracted, that is, until the flange 54 comes into contact with the end face of the holder 52, and the valve closed state is maintained. Then, when the support mechanism 5 is in a fully contracted state, the valve 2 starts to be lifted, and is separated from the valve seat 6 to be opened. FIG. 7 shows a state where the nose of the cam 31 contacts the roller 41 and the valve 2 is fully opened. In this way, the lift amount in the medium operating angle state shown in FIG. 7 is smaller than the lift amount in the maximum operating angle state shown in FIG.

  8 and 9 are side views showing the variable valve gear 10 in the minimum operating angle state. The state shown in FIG. 8 is a valve-closed state in which the base circle portion of the cam 31 is in contact with the roller 41. In the state shown in FIG. 8, the rotation center C <b> 2 of the camshaft 3 moves further away from the roller 41 than in the valve closing state in the intermediate working angle state shown in FIG. 6. However, when the support mechanism 5 is further extended by the urging force of the coil spring 55 and pushes up the fulcrum of the rocker arm 4, the contact state between the roller 41 and the base circle portion of the cam 31 is maintained. When the cam 31 rotates from the state shown in FIG. 8 and the roller 41 is pressed, the pressing force is transmitted to the support mechanism 5 and the support mechanism 5 contracts.

  FIG. 9 shows a state where the nose of the cam 31 is in contact with the roller 41. In the minimum operating angle state, as shown in FIG. 9, when the nose of the cam 31 is in contact with the roller 41, the support mechanism 5 is in a fully contracted state (or a state immediately before the contraction), so that the valve 2 Does not lift from the valve seat 6, and the valve-closed state is maintained. In this way, in the minimum operating angle state shown in FIG. 9, a valve stop state is realized in which the operating angle and lift amount of the valve 2 are zero.

  As shown in FIGS. 6 to 9, in the present embodiment, the coil spring 55 as the urging means for urging the fulcrum of the rocker arm 4 in the direction of the cam shaft 3 is provided in the support mechanism 5. Thus, the roller 41 and the cam 31 can be kept in contact with each other. In the present invention, the urging means for urging the fulcrum of the rocker arm 4 in the direction of the camshaft 3 is not limited to a spring such as the coil spring 55. For example, hydraulic pressure is supplied into the holder 52. The plunger 53 may be pushed up.

  According to the variable valve apparatus 10 of the present embodiment as described above, by rotating the control shaft 8 to rotate the eccentric cam bearing 7, between the maximum operating angle state and the minimum operating angle state, The operating angle and lift amount of the valve 2 can be continuously changed. Moreover, in the variable valve operating apparatus 10, the number of parts interposed between the cam 31 and the valve 2 is small. Further, the mechanism for moving the rotation center C2 of the cam shaft 3 by the eccentric cam bearing 7 is also a simple mechanism having a small number of parts. Since the operating angle and lift amount of the valve 2 can be changed by such a simple mechanism, it is possible to reduce the size, weight, cost, durability, and reliability. In addition, since the number of parts interposed between the cam 31 and the valve 2 is small, variations in the lift amount can be suppressed, and the lift amounts can be accurately matched among a plurality of cylinders.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 10. The description will focus on the differences from the first embodiment described above, and the same matters will be simplified or described. Omitted. FIG. 10 is a side view showing the variable valve operating apparatus according to the second embodiment of the present invention. As will be described below, the present embodiment is the same as the first embodiment described above except that the support mechanism 5 is provided with an impact mitigation means for mitigating an impact when the lift of the valve 2 starts. It is.

  In the present embodiment, oil is supplied to the internal space 56 of the holder 52 of the support mechanism 5. The internal space 56 communicates with the oil sump 58 via the orifice 57. When the cam 31 rotates and the roller 41 is pressed from the valve open state in the intermediate operating angle state shown in FIG. 10, the pressing force is transmitted to the support mechanism 5 and the support mechanism 5 contracts. At this time, as the plunger 53 enters the holder 52, the oil in the internal space 56 passes through the orifice 57 and is discharged to the oil reservoir 58. Then, the lift of the valve 2 starts when the support mechanism 5 is shrunk and the flange 54 comes into contact with the end face of the holder 52. According to this embodiment, when the support mechanism 5 contracts and the flange 54 collides with the end surface of the holder 52, the speed of the plunger 53 is attenuated by the resistance when oil passes through the orifice 57. Therefore, the impact when the flange 54 collides with the end face of the holder 52 (that is, the impact when the valve 2 starts to lift) is reduced. For this reason, noise can be more reliably suppressed.

  The impact mitigating means in the present invention is not limited to the above configuration. For example, a second spring that comes into contact with the flange 54 is provided immediately before the support mechanism 5 is contracted, and an impact when the support mechanism 5 contracts (that is, an impact when the lift of the valve 2 starts) is applied to the second spring. The same effect can be obtained also by the impact mitigating means configured to absorb by.

2 Valve 3 Cam shaft 31 Cam 4 Rocker arm 41 Roller 5 Support mechanism 51 Support portion 52 Holder 53 Plunger 54 Flange 55 Coil spring 56 Internal space 57 Orifice 58 Oil reservoir 6 Valve seat 7 Eccentric cam bearing 8 Control shaft 10 Variable valve system

Claims (4)

A valve provided in a cylinder of the internal combustion engine;
A camshaft provided with a cam;
An eccentric cam bearing that is rotatably installed and receives the cam shaft at a position eccentric from the rotation center thereof;
A driving device for rotating the eccentric cam bearing;
A rocker arm that receives the lift of the cam and presses and opens the valve;
A support mechanism for supporting a fulcrum of the rocker arm;
With
A variable valve operating apparatus for an internal combustion engine, wherein the operating angle and lift amount of the valve are made variable by rotating the eccentric cam bearing to move the position of the rotation center of the cam shaft.   2. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the support mechanism includes a biasing unit that biases a fulcrum of the rocker arm in a direction approaching the camshaft.   The variable valve operating apparatus for an internal combustion engine according to claim 1 or 2, wherein the biasing means is a spring.   The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the support mechanism includes an impact mitigating means for mitigating an impact when the lift of the valve starts.

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