JP6154028B2 - Engine valve gear - Google Patents

Description

  The present invention relates to a valve operating device for an engine capable of changing a valve working angle of an intake valve or an exhaust valve.

  2. Description of the Related Art Conventionally, as a valve operating device for driving an intake valve or an exhaust valve of a four-cycle engine, there is one provided with a rocker arm that changes the rotation of a camshaft to a reciprocating motion and transmits it to an intake valve or an exhaust valve. The rocker arm is swingably supported by a rocker shaft parallel to the cam shaft.

  In this type of valve operating device, as described in Patent Document 1, for example, by moving a pressing member interposed between the cam shaft and the rocker arm in the longitudinal direction of the rocker arm, It is known that the valve lift amount and valve opening / closing timing of the exhaust valve can be continuously changed. The pressing member disclosed in Patent Document 1 is connected to a rocker shaft via a link mechanism.

  This link mechanism is composed of a control arm that is swingably supported by the rocker shaft, and an auxiliary arm that is swingably supported at the swing end of the control arm about an axis parallel to the rocker shaft. ing. The pressing member is provided at the swing end of the auxiliary arm. The control arm swings when driven by an actuator.

  In the valve gear described in Patent Document 1, the pressing member moves in the longitudinal direction of the rocker arm as the control arm swings. The valve opening / closing timing is retarded by the pressing member moving toward the front in the rotational direction of the cam shaft, and the valve opening / closing timing is advanced by moving toward the rear in the rotational direction of the cam shaft. Further, when the pressing member moves toward the rocking end of the rocker arm, the lever ratio of the rocker arm is reduced and the valve lift amount is relatively reduced. When the pressing member moves to the base end side of the rocker arm, that is, the rocker shaft side, the lever ratio of the rocker arm is increased and the valve lift amount is relatively increased.

JP 2001-164911 A

  In the conventional valve operating device disclosed in Patent Document 1, when the pressing member moves and the opening timing of the intake valve or the exhaust valve becomes earlier, for example, the closing timing of the valve becomes earlier. For this reason, in this valve operating apparatus, the valve operating angle does not change even if the pressing member moves. The valve operating angle is a cam shaft rotation angle corresponding to a period during which the intake valve or the exhaust valve is open.

The valve operating angle is desirably large in order to increase the output when the rotational speed of the engine is relatively high. Further, it is desirable that the valve working angle is small so that combustion is stable when the rotational speed of the engine is relatively low.
However, since the conventional valve operating device described in Patent Document 1 does not have a function of changing the valve working angle, there is a problem that the valve working angle cannot be controlled to a size suitable for the operating state. there were.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a valve operating apparatus for an engine capable of controlling the magnitude of a valve working angle.

To achieve this object, a valve operating apparatus for an engine according to the present invention is provided in a camshaft main body rotatably supported by a cylinder head, and arranged in the axial direction of the camshaft main body. Two cams, a rocker shaft provided on the cylinder head in parallel with the camshaft main body, and a rocker shaft configured to be swingable about the rocker shaft and capable of contacting one of the two cams A rocker arm having a pressing portion for pressing the intake valve or the exhaust valve, a control arm configured to be swingable about the rocker shaft, and the rocker shaft at a swing end of the control arm An auxiliary arm supported so as to be swingable about an axis parallel to the axis, and a swing end of the auxiliary arm, the two cams A pressing member positioned between the other cam and the rocker arm, and the pressing member is sandwiched between the other cam and the rocker arm as the control arm swings. The other cam is movable in one or the other of the rotational directions.

  According to the present invention, the rocker arm is positioned at the initial position in a state where the base circle portion of the cam faces the pressure receiving portion and the pressing member. The rocker arm starts swinging when the contact point between the pressure receiving portion or the pressing member and the cam moves from the base circle portion to the nose portion. The intake valve or the exhaust valve is thus opened when the rocker arm starts swinging from the initial position. Further, the intake valve or the exhaust valve is closed when the contact point between the pressure receiving portion or the pressing member and the cam moves from the nose portion of the cam to the base circle portion.

  The pressing member contacts the nose portion of the cam prior to the pressure receiving portion by moving rearward in the rotational direction of the cam with respect to the pressure receiving portion. In this case, the opening timing of the intake valve or the exhaust valve is determined based on the position of the pressing member, and becomes relatively early. In this case, when the cam rotation angle at which the cam pushes the pressure receiving portion of the rocker arm is larger than the amount by which the cam pushes the pressing member, the pressure receiving portion is pushed by the cam and the intake valve or the exhaust valve operates. Change to state. In this case, the timing when the intake valve or the exhaust valve is closed is when the contact point between the pressure receiving portion and the cam moves from the nose portion of the cam to the base circle portion. For this reason, when the pressing member moves rearward in the rotational direction of the cam, the valve operating angle of the intake valve or the exhaust valve expands to the advance side.

On the other hand, when the pressing member moves forward in the rotational direction of the cam, the pressure receiving portion contacts the nose portion of the cam before the pressing member, and the intake valve or the exhaust valve opens. Further, in this case, when the cam rotation angle is reached such that the cam pushes the pressing member more than the cam pushes the pressure receiving portion, the pushing member is pushed by the cam and the intake valve or the exhaust valve operates. Changes to. In this case, the closing time of the intake valve or the exhaust valve is when the contact point between the pressing member and the cam moves from the nose portion of the cam to the base circle portion. For this reason, when the pressing member moves forward in the rotational direction of the cam, the valve operating angle of the intake valve or the exhaust valve expands to the retard side.
Therefore, according to this invention, the valve operating apparatus of the engine which can control the magnitude | size of a valve working angle by changing the position of a press member can be provided.

FIG. 1 is a cross-sectional view showing a main part of a valve gear for an engine according to a first embodiment of the present invention. FIG. 2 is a side view of the valve gear for the engine according to the first embodiment. In FIG. 2, the fracture position in FIG. 1 is indicated by line II, the fracture position in FIG. 4 is indicated by line IV-IV, and the fracture position in FIG. 5 is indicated by line V-V. FIG. 3 is an exploded perspective view of a rocker arm portion of the valve gear for the engine according to the first embodiment. FIG. 4 is a cross-sectional view of the roller of the pressing member and the rocker arm. FIG. 5 is a cross-sectional view of the connecting shaft of the pressing member and the rocker arm. FIG. 6 is a graph showing the relationship between the cam rotation angle and the valve lift amount of the valve gear for the engine according to the first embodiment. FIG. 6 shows the valve lift when the pressing member is located at the neutral position. FIG. 7 is an enlarged cross-sectional view showing a main part of the valve gear for the engine according to the first embodiment. FIG. 7 shows a state where the pressing member has moved rearward in the rotational direction of the camshaft. FIG. 8 is a graph showing the relationship between the cam rotation angle and the valve lift amount of the valve gear for the engine according to the first embodiment. FIG. 8 shows the valve lift when the pressing member moves rearward in the rotational direction of the camshaft. FIG. 9 is an enlarged cross-sectional view showing a main part of the valve gear for the engine according to the first embodiment. FIG. 9 shows a state in which the pressing member has moved forward in the rotational direction of the camshaft. FIG. 10 is a graph showing the relationship between the cam rotation angle and the valve lift amount of the valve gear for the engine according to the first embodiment. FIG. 10 shows the valve lift when the pressing member moves forward in the rotational direction of the camshaft. FIG. 11 is an enlarged cross-sectional view showing a main part of the valve gear for an engine according to the second embodiment. FIG. 11 shows a state where the pressing member is located at the neutral position. FIG. 12 is a graph showing the relationship between the cam rotation angle and the valve lift of the valve gear for the engine according to the second embodiment. FIG. 12 shows the valve lift when the pressing member is located at the neutral position. FIG. 13 is a graph showing the relationship between the cam rotation angle and the valve lift amount of the valve gear for the engine according to the second embodiment. FIG. 13 shows the valve lift when the pressing member moves forward in the rotational direction of the camshaft. FIG. 14 is an enlarged cross-sectional view showing a main part of the valve gear for an engine according to the second embodiment. FIG. 14 shows a state in which the pressing member has moved rearward in the rotational direction of the camshaft. FIG. 15 is an enlarged cross-sectional view showing a main part of the valve gear for an engine according to the third embodiment. FIG. 15 shows a state where the pressing member is located at the neutral position. FIG. 16 is a graph showing the relationship between the cam rotation angle and the valve lift amount of the valve gear for the engine according to the third embodiment. FIG. 16 shows the valve lift when the pressing member is positioned at the neutral position. FIG. 17 is an enlarged cross-sectional view showing a main part of the valve gear for an engine according to the third embodiment. FIG. 17 shows a state in which the pressing member has moved rearward in the rotational direction of the camshaft. FIG. 18 is a graph showing the relationship between the cam rotation angle and the valve lift of the valve gear for the engine according to the third embodiment. FIG. 18 shows the valve lift when the pressing member moves rearward in the rotational direction of the camshaft. FIG. 19 is an enlarged cross-sectional view of a main part of the valve gear for an engine according to the third embodiment. FIG. 19 shows a state in which the pressing member has moved forward in the rotational direction of the camshaft. FIG. 20 is a graph showing the relationship between the cam rotation angle and the valve lift amount of the valve gear for the engine according to the third embodiment. FIG. 20 shows the valve lift when the pressing member moves forward in the rotational direction of the camshaft.

(First embodiment)
Hereinafter, an embodiment of a valve operating apparatus for an engine according to the present invention will be described in detail with reference to FIGS.
A valve operating apparatus 1 for an engine shown in FIG. 1 drives an intake valve 4 by changing the rotation of a camshaft 3 provided in a cylinder head 2 of a multi-cylinder engine into a reciprocating motion. The valve gear 1 according to the present invention is not limited to driving the intake valve 4 as described above, and can be configured to drive the exhaust valve 5.

  The camshaft 3 rotates when rotation of a crankshaft (not shown) is transmitted through a transmission mechanism. The camshaft 3 according to this embodiment rotates clockwise in FIG. The camshaft 3 includes a camshaft body 6 rotatably supported by the cylinder head 2 and two intake valve driving cams 7 and 8 (see FIG. 2) provided on the camshaft body 6. .

  The two cams 7 and 8 are arranged in a state of being separated from each other with a predetermined interval in the axial direction of the camshaft body 6. Hereinafter, of these cams 7 and 8, one cam located on the right side in FIG. 2 is referred to as a first cam 7, and the other cam is referred to as a second cam 8. As shown in FIG. 1, the first cam 7 and the second cam 8 have base circular portions 7a and 8a and nose portions 7b and 8b, respectively, and are provided for each cylinder.

The base circle portions 7a and 8a are used when the intake valve 4 is closed, and the nose portions 7b and 8b are used when the intake valve 4 is opened and closed. The base circular portions 7a and 8b are formed in a shape that is a part of a cylinder located on the same axis as the camshaft body 6. The nose portions 7b and 8b are formed in a shape protruding from the base circular portions 7a and 8a by a predetermined protrusion amount in a cross-sectional mountain shape outward in the radial direction. The apex of the nose portion 7 b of the first cam 7 and the apex of the nose portion 8 b of the second cam 8 coincide with each other in the rotational direction of the camshaft 3.
The nose portion 7b of the first cam 7 according to this embodiment is formed in a shape that has a larger protruding amount than the nose portion 8b of the second cam 8.

  Two intake valves 4 are provided per cylinder. These intake valves 4 are configured by a valve body 4 a that opens and closes the intake port 11 of the cylinder head 2 and a valve stem 4 b that extends from the valve body 4 a into the valve operating chamber 12 of the cylinder head 2. The valve stem 4 b is movably supported by the cylinder head 2 by a valve stem guide 13. A valve spring 14 that urges the intake valve 4 in the closing direction is provided between the tip of the valve stem 4b and the cylinder head 2. A cap-shaped shim 4c is provided at the tip of the valve stem 4b.

  The intake port 11 is formed in a bifurcated shape inside the cylinder head 2. The upstream end of the intake port 11 opens to the side of the cylinder head 2, and the downstream end of the intake port 11 opens to the combustion chamber 15. A spark plug 16 is provided at the center of the combustion chamber 15.

The valve gear 1 can change the valve working angle of the intake valve 4 and includes two arm members (a rocker arm 21 and an auxiliary arm 22) for each cylinder. The valve operating angle is a rotation angle of the camshaft 3 from when the intake valve 4 is opened to when it is closed.
As shown in FIGS. 2 and 3, the rocker arm 21 is formed long in the direction in which the two intake valves 4 are arranged. On one end side in the longitudinal direction of the rocker arm, a pressure receiving portion 23 is formed which can come into contact with one of the two cams. In addition, pressing portions 24 that press the two intake valves 4 are formed at both ends of the rocker arm 21. The pressure receiving portion 23 and the pressing portion 24 are integrally formed by integral molding.

The rocker arm 21 has a boss portion 21a into which a rocker shaft 25 (see FIG. 1), which will be described later, is rotatably fitted. The rocker arm 21 is swingably supported around the rocker shaft 25 around the rocker shaft 25. ing.
The rocker shaft 25 is rotatably supported by the cylinder head 2 so as to extend in parallel with the camshaft 3. The rocker shaft 25 supports the rocker arms 21 of all cylinders so as to be relatively rotatable. An actuator 26 (see FIG. 2) is connected to one end of the rocker shaft 25. As the actuator 26, for example, an actuator that drives the rocker shaft 25 by hydraulic pressure or electric power can be used. As will be described later in detail, the actuator 26 rotates the rocker shaft 25 clockwise or counterclockwise in FIG. 1 by a predetermined angle based on the engine load and the rotational speed.

  As shown in FIG. 1, the rocker arm 21 according to this embodiment extends from the rocker shaft 25 to the outside of the cylinder head 2 {direction perpendicular to the axis of the rocker shaft 25 and the cylinder axis CL (see FIG. 1)}. The rocker shaft 25 is swingably supported. The pressing part 24 is provided at the rocking end of the rocker arm 21. That is, when the rocker arm 21 swings clockwise in FIG. 1, the pressing portion 24 pushes the two intake valves 4 against the spring force of the valve spring 14.

The rocker shaft 25 supports a control arm 27 in addition to the rocker arm 21. The control arm 27 is inserted into a notch 21b (see FIG. 3) formed in the boss portion 21a of the rocker arm 21, and is configured to be swingable with respect to the rocker arm 21 around the rocker shaft 25. ing.
The control arm 27 according to this embodiment is supported by the rocker shaft 25 with the rocker shaft 25 penetrating therethrough. As shown in FIG. 4, a connecting pin 28 is inserted into a portion of the control arm 27 through which the rocker shaft 25 passes. The connecting pin 28 connects the control arm 27 and the rocker shaft 25 so as to rotate together.

  That is, the control arm 27 according to this embodiment swings around the rocker shaft 25 as the rocker shaft 25 rotates. The control arm 27 according to this embodiment swings to the forward movement position shown in FIG. 7 when the rocker shaft 25 is rotated by a predetermined angle clockwise in FIG. Further, the control arm 27 swings to the retracted position shown in FIG. 9 when the rocker shaft 25 is rotated by a predetermined angle counterclockwise in FIG.

The auxiliary arm 22 is swingably supported on the swing end portion (front end portion) of the control arm 27 via a support shaft 29. The support shaft 29 is provided on the control arm 27 in parallel with the rocker shaft 25. That is, the auxiliary arm 22 is supported on the swing end of the control arm 27 so as to be swingable about an axis parallel to the rocker shaft 25.
The auxiliary arms 22 according to this embodiment are respectively provided on both sides of the control arm 27 as shown in FIGS. At the swinging end portion of the auxiliary arm 22, a pressing member 31 that is sandwiched between the second cam 8 of the camshaft 3 and the rocker arm 21 and transmits a pressing force is provided.

As shown in FIGS. 2 and 3, the pressing member 31 according to this embodiment is rotatable to a connecting shaft 32 spanned between the pair of auxiliary arms 22 and 22 and to the central portion of the connecting shaft 32. And a roller 33 supported by the motor. The roller 33 rotates in contact with the second cam 8.
Both ends of the connecting shaft 32 are fixed to the auxiliary arm 22. Further, as shown in FIG. 2, the connecting shaft 32 is formed in a length that is partially exposed as an exposed portion 32 a between the auxiliary arm 22 and the roller 33.

  The exposed portion 32 a contacts a rail 34 formed on the rocker arm 21. Since the exposed portions 32a are respectively located at positions sandwiching the roller 33, the rocker arm 21 is provided with two rails 34. That is, both ends of the connecting shaft 32 are in contact with the rocker arm 21. In this embodiment, these rails 34 constitute the “part where the pressing member in the rocker arm contacts” according to the invention of claim 2.

  A concave groove 35 is formed between the two rails 34 in the rocker arm 21 as shown in FIGS. As shown in FIG. 4, the concave groove 35 is for preventing the roller 33 from coming into contact with the rocker arm 21, and is connected to the roller 33 in a state where the connecting shaft 32 (exposed portion 32 a) is in contact with the rail 34. It is formed in a shape in which a gap is formed between them. A concave groove 36 for avoiding interference with the auxiliary arm 22 is formed on the side opposite to the concave groove 35 across the rail 34 in the rocker arm 21.

  As shown in FIG. 5, the shape of the portion of the rail 34 that contacts the connecting shaft 32 has a circular arc shape. That is, the cross-sectional shape of the rail 34 is such that the roller 33 is in contact with the base circle portion 8a of the second cam 8 as viewed from the axial direction of the camshaft 3 (the lift amount of the intake valve 4 is 0). The camshaft 3 is formed in an arc shape having a radius R centered on the axis C of the camshaft 3. For this reason, the pressing member 31 is movable along the second cam 8 while being sandwiched between the second cam 8 and the pressing portion 24 in a state where the roller 33 is in contact with the base circle portion 8a. is there.

  That is, the pressing member 31 can move from the position shown in FIG. 1 to the right (in the direction away from the rocker shaft 25 and rearward in the rotational direction of the camshaft 3) or to the left. In the following, the position shown in FIG. 1 is referred to as a neutral position. The neutral position means that a contact point P1 between the pressure receiving portion 23 and the base circle portion 7a of the first cam 7 and a contact point P2 between the pressing member 31 and the base circle portion 8a of the second cam 8 are camshafts. 3 in the rotational direction.

  When the pressing member 31 moves from the neutral position in FIG. 1 to the rear in the rotational direction of the camshaft 3 (see FIG. 7), the rotational phase of the second cam 8 is substantially relative to the first cam 7. move on. That is, the pressing member 31 contacts the nose portion 8 b of the second cam 8 before the pressure receiving portion 23 contacts the nose portion 7 b of the first cam 7. In this case, the opening timing of the intake valve 4 is determined based on the position of the pressing member 31, and the opening timing of the intake valve 4 is compared with the case where the pressure receiving portion 23 is pressed by the first cam 7 and the intake valve 4 is opened. Becomes faster. In this case, the lever ratio of the rocker arm 21 is reduced.

  On the other hand, when the pressing member 31 moves forward in the rotational direction of the camshaft 3 (see FIG. 9), the rotational phase of the second cam 8 is substantially delayed with respect to the first cam 7. That is, after the pressure receiving portion 23 comes into contact with the nose portion 7 b of the first cam 7, the pressing member 31 comes into contact with the nose portion 8 b of the second cam 8. In this case, the closing timing of the intake valve 4 is determined based on the position of the pressing member 31. Compared to the case where the intake valve 4 is closed while the pressure receiving portion 23 is pressed by the first cam 7, the intake valve 4 is closed. The closing time is delayed. In this case, the lever ratio of the rocker arm 21 is increased.

  In the valve operating apparatus configured as described above, when the engine operating state is a predetermined low load and low speed operating state, the actuator 26 drives the rocker shaft 25 so that the pressing member 31 is shown in FIG. Positioned in the neutral position. The low load and low speed operation states here are at least one of a state where the engine load is lower than a predetermined load threshold and a state where the engine rotational speed is lower than a predetermined speed threshold. That means.

  When the pressing member 31 is located at the neutral position, the valve lift amount of the intake valve 4 changes as shown in FIG. The solid line shown in FIG. 6 shows the valve lift curve of the first cam 7. That is, this solid line indicates a change in the valve lift amount when only the first cam 7 pushes the rocker arm 21 on the assumption that the second cam 8 is not provided. A broken line shown in FIG. 6 indicates a valve lift curve of the second cam 8. That is, this broken line indicates a change in the valve lift amount when the second cam 8 pushes the pressing member 31 on the assumption that the first cam 7 is not provided.

  In a state where the pressing member 31 is located at the neutral position, as shown by a solid line in FIG. 6, the first cam 7 presses the pressure receiving portion 23 of the rocker arm 21, and the pressing portion 24 presses the intake valve 4. In the state, the intake valve 4 opens and closes. The intake valve 4 opens when the cam rotation angle is A ° shown in FIG. 6, and closes when the cam rotation angle is B °. The valve operating angle in this case is an angle obtained by subtracting the cam rotation angle A ° from the cam rotation angle B °, and is an angle indicated by α1 in FIG. In this case, the pressing force is not transmitted from the second cam 8 to the rocker arm 21 via the pressing member 31.

  When the engine load exceeds the aforementioned load threshold or when the engine speed exceeds the aforementioned speed threshold, the actuator 26 drives the rocker shaft 25 and the control arm 27 swings toward the forward or backward position. Move. The swinging direction of the control arm 27 at this time can be determined based on the basic configuration such as the ignition timing of the engine and the opening / closing timing of the exhaust valve, the operating state at that time, and the like.

  When the control arm 27 is positioned at the forward movement position as shown in FIG. 7, the pressing member 31 moves backward from the neutral position in the rotational direction of the second cam 8. In this case, the valve lift amount of the intake valve 4 changes as shown by a thick line in FIG. In this case, the pressing member 31 is pushed by the nose portion 8 b of the second cam 8 before the pressure receiving portion 23 is pushed by the nose portion 7 b of the first cam 7. For this reason, the intake valve 4 opens when the cam rotation angle C ° is smaller than the cam rotation angle A ° when the rocker arm 21 is opened by the first cam 7 being pushed. That is, the intake valve 4 opens by being advanced by an angle obtained by subtracting the cam rotation angle C ° from the cam rotation angle A °.

  Immediately after the intake valve 4 is opened, the second cam 8 pushes the rocker arm 21. The valve lift amount of the intake valve 4 at this time increases as shown by the valve lift curve of the second cam 8. However, when the cam rotation angle reaches D °, the first cam 7 changes to a state of pushing the rocker arm 21. For this reason, after the cam rotation angle exceeds D °, the valve lift amount of the intake valve 4 changes as shown by the valve lift curve of the first cam 7. In this case, the intake valve 4 is closed when the cam rotation angle is B °. In this case, the valve operating angle α2 expands toward the advance side by an angle obtained by subtracting the cam rotation angle C ° from the cam rotation angle A °, as compared with the valve operation angle α1 described above.

  When the control arm 27 is positioned at the retracted position as shown in FIG. 9, the pressing member 31 moves forward from the neutral position in the rotational direction of the second cam 8. In this case, the valve lift amount of the intake valve 4 changes as shown by a thick line in FIG. In this case, the pressure receiving portion 23 of the rocker arm 21 is pushed by the nose portion of the first cam 7 before the pressing member 31 is pushed by the nose portion 8 b of the second cam 8. Therefore, the intake valve 4 opens when the rocker arm 21 is pushed by the first cam 7 and the cam rotation angle is A °.

After the intake valve 4 is opened, the first cam 7 pushes the rocker arm 21 until the cam rotation angle reaches E °. The valve lift amount of the intake valve 4 at this time changes as shown in the valve lift curve of the first cam 7.
When the cam rotation angle exceeds E °, the second cam 8 changes to a state where the rocker arm 21 is pushed. For this reason, after the cam rotation angle exceeds E °, the valve lift amount of the intake valve 4 changes as indicated by the valve lift curve of the second cam 8. The valve lift amount L1 of the second cam 8 at the cam rotation angle E ° is larger than the valve lift amount at the cam rotation angle D ° shown in FIG. 8 because the lever ratio of the rocker arm 21 is large. Many. However, the valve lift amount L1 is smaller than the maximum valve lift amount L2 of the first cam 7.

That is, the nose portion 8b of the second cam 8 according to this embodiment has a maximum valve lift amount when the pressing member 31 is moved to a position where the lever ratio of the rocker arm 21 is maximized, as shown in FIG. Is smaller than the maximum valve lift amount L2 of the first cam 7.
After the cam rotation angle E ° is exceeded, when the valve lift amount of the intake valve 4 decreases as shown by the valve lift curve of the second cam 8, the intake valve 4 has a cam rotation angle of F ° larger than B °. Close when. In this case, the valve operating angle α3 expands to the retard side by an angle obtained by subtracting the cam rotation angle B ° from the cam rotation angle F °, as compared with the valve operation angle α1 described above.

For this reason, in the valve gear 1 according to this embodiment, the valve operating angle is expanded to the advance side as the pressing member 31 moves rearward in the rotational direction of the camshaft 3. (FIG. 8) Further, when the pressing member 31 moves forward in the rotational direction of the camshaft 3, the valve operating angle is expanded toward the retarded side. (Fig. 10)
Therefore, according to this embodiment, it is possible to provide an engine valve gear that can control the magnitude of the valve operating angle by changing the position of the pressing member 31.

The rail 34 of the rocker arm 21 according to this embodiment is formed in a circular arc shape with the axis C of the camshaft 3 as the center when the lift amount of the intake valve 4 is zero.
For this reason, the pressing member 31 moves smoothly while maintaining a state in which the pressing member 31 is in contact with the base circle portion 8 a of the second cam 8. Therefore, since the control arm 27 can be quickly swung while the intake valve 4 is closed, the valve operating device for the engine that can change the valve operating angle even when the engine speed is high. Can be provided.

The auxiliary arms 22 according to this embodiment are provided at positions that sandwich the control arm 27 from both sides in the axial direction. The pressing member 31 includes a connecting shaft 32 that is spanned between the two auxiliary arms 22, and a roller 33 that is rotatably supported at the center of the connecting shaft 32. Both ends of the connecting shaft 32 are in contact with the rocker arm 21, and the roller 33 is in contact with the second cam 8 and rotates.
For this reason, according to this embodiment, the pressing member 31 moves more smoothly while maintaining a state in which the pressing member 31 is in contact with the base circle portion 8a of the second cam 8. Therefore, according to this embodiment, it is possible to provide an engine valve operating device that can control the magnitude of the valve operating angle with high responsiveness during engine operation.

The first and second cams 7 and 8 according to this embodiment have base circle portions 7a and 8a each having a valve lift amount of 0, and predetermined protrusions radially outward from the base circle portions 7a and 8a. It has nose parts 7b and 8b protruding by the amount. The nose portion 8b of the second cam 8 has a shape in which the maximum valve lift amount is smaller than the maximum valve lift amount of the first cam 7 when the pressing member 31 is moved to a position where the lever ratio of the rocker arm 21 is maximized. Is formed.
For this reason, regardless of the position of the pressing member 31, the first cam 7 presses the pressure receiving portion 23 of the rocker arm 21, thereby maximizing the valve lift amount of the intake valve 4. Therefore, according to this embodiment, it is possible to provide an engine valve operating apparatus that can control the magnitude of the valve operating angle while keeping the maximum valve lift amount constant.

(Second Embodiment)
In the embodiment described above, an example in which the camshaft rotates clockwise in FIG. However, the rotational direction of the camshaft can be counterclockwise in FIG. The embodiment in this case will be described in detail with reference to FIGS. In these drawings, the same or equivalent members as those described with reference to FIGS. 1 to 10 are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

  The rotation direction of the camshaft 3 shown in FIG. 11 is counterclockwise in the figure. When the pressing member 31 is positioned at the neutral position as shown in FIG. 11, the intake valve 4 is opened and closed by the first cam 7 regardless of the rotation direction of the camshaft 3. That is, in this case, as shown in FIG. 12, the intake valve 4 is opened when the cam rotation angle is a °, and the intake valve 4 is closed when the cam rotation angle is b °. The valve operating angle in this case is β1, which is the difference between the cam rotation angle b ° and the cam rotation angle a °.

  When the control arm 27 shown in FIG. 11 is positioned at the forward movement position and the pressing member 31 moves in a direction away from the rocker shaft 25 and is positioned forward in the rotational direction of the camshaft 3, as shown in FIG. When the cam rotation angle is a °, the intake valve 4 is opened by the first cam 7 pushing the rocker arm 21. Thereafter, until the cam rotation angle reaches c °, the valve lift amount of the intake valve 4 as shown in the valve lift curve of the first cam 7 in order to keep the first cam 7 pushing the rocker arm 21. Changes.

  After the cam rotation angle reaches c °, the second cam 8 changes to a state in which the rocker arm 21 is pushed, so that the valve lift amount of the intake valve 4 is as shown in the valve lift curve of the second cam 8. Decrease. In this case, the intake valve 4 is closed when the cam rotation angle is d °. In this case, the valve operating angle β2 is wider on the retard side by an angle corresponding to the difference between the cam rotational angle d ° and the cam rotational angle b ° than the valve operating angle β1 described above.

  When the control arm 27 shown in FIG. 11 is positioned in the retracted position and the pressing member 31 moves in the direction approaching the rocker shaft 25 and is located rearward in the rotational direction of the camshaft 3, as shown in FIG. When the cam rotation angle is e °, the second cam 8 pushes the rocker arm 21 through the pressing member 31 to open the intake valve 4. Thereafter, until the cam rotation angle reaches f °, the valve lift amount of the intake valve 4 as shown in the valve lift curve of the second cam 8 in order to keep the second cam 8 pushing the rocker arm 21. Changes.

After the cam rotation angle reaches f °, the first cam 7 changes to a state in which the rocker arm 21 is pushed, so that the intake valve 4 operates as indicated by the valve lift curve of the second cam. In this case, the intake valve 4 is closed when the cam rotation angle is b °. In this case, the valve operating angle β3 is wider on the advance side than the valve operating angle β1 described above by an angle corresponding to the difference between the cam rotation angle a ° and the cam rotation angle e °.
Therefore, it is possible to provide a valve operating apparatus for an engine that can control the magnitude of the valve operating angle without depending on the rotation direction of the camshaft 3.

(Third embodiment)
In the above-described embodiment, the example in which the first cam and the second cam having different maximum valve lift amounts are used is shown. However, the first cam and the second cam are shown in FIGS. Thus, the same shape can be used. 15 to 20, the same or equivalent members as those described with reference to FIGS. 1 to 14 are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

The first cam 7 and the second cam 8 of the camshaft 3 shown in FIGS. 15, 17 and 19 are formed in the same shape. The rotation direction of the camshaft 3 is clockwise in these drawings.
In the valve operating apparatus 1 according to this embodiment, when the pressing member 31 is located at the neutral position shown in FIG. 15, the contact point P1 between the pressure receiving portion 23 and the base circular portion 7a of the first cam 7; The contact point P <b> 2 between the pressing member 31 and the base circle portion 8 a of the second cam 8 always coincides with the rotation direction of the camshaft 3. In this case, the intake valve 4 opens and closes as shown in the valve lift curve shown in FIG. That is, the intake valve 4 opens when the cam rotation angle is A ° and closes when the cam rotation angle is B °. In this case, the valve operating angle is α1.

  When the control arm 27 swings to the forward movement position as shown in FIG. 17 and the pressing member 31 moves rearward in the rotational direction of the camshaft 3, the intake valve 4 is moved to the rocker by the second cam 8 via the pressing member 31. Open by pressing the arm 21. As shown in FIG. 18, the intake valve 4 opens when the cam rotation angle is C °. In this case, the lever ratio of the rocker arm 21 is smaller than when the pressing member 31 is positioned at the neutral position. For this reason, the valve lift amount of the second cam 8 is relatively reduced, and the first cam 7 starts to push the rocker arm 21 when the cam rotation angle is D °.

After the cam rotation angle exceeds D °, the intake valve 4 operates as indicated by the valve lift curve of the first cam 7. The valve lift amount of the intake valve 4 becomes maximum when the first cam 7 pushes the rocker arm 21. In this case, the intake valve 4 is closed when the cam rotation angle is B °. In this case, the valve operating angle α2 expands to the advance side by the difference between the cam rotation angle A ° and the cam rotation angle C ° as compared with the case where the pressing member 31 is positioned at the neutral position.
In the state shown in FIG. 17, the contact point P <b> 2 between the second cam 8 and the pressing member 31 is the first cam 7 and the rocker arm 21 (pressure receiving portion 23) when viewed from the axial direction of the camshaft body 6. The position of the rocker arm 21 is shifted from the contact point P1 in a direction in which the lever ratio becomes smaller. In this state, the magnitude of the valve operating angle is set in a state where the maximum valve lift amount is constant (same as the maximum valve lift amount in FIG. 16) even though the shapes of the two cams 7 and 8 are the same. Can be controlled.

  When the control arm 27 swings to the retracted position as shown in FIG. 19 and the pressing member 31 moves forward in the rotation direction of the camshaft 3, the intake valve 4 causes the first cam 7 to push the rocker arm 21. open. As shown in FIG. 20, the intake valve 4 opens when the cam rotation angle is A °. In this case, the lever ratio of the rocker arm 21 becomes larger than when the pressing member 31 is positioned at the neutral position. For this reason, the valve lift amount of the second cam 8 is relatively increased, and the second cam 8 starts to push the pressing member 31 when the cam rotation angle is E °.

  After the cam rotation angle exceeds E °, the intake valve 4 operates as indicated by the valve lift curve of the second cam 8. In this case, the valve lift amount of the intake valve 4 becomes maximum when the second cam 8 pushes the rocker arm 21. In this case, the intake valve 4 is closed when the cam rotation angle is F °. In this case, the valve operating angle α3 is widened to the retard side by the difference between the cam rotation angle F ° and the cam rotation angle B ° as compared with the case where the pressing member 31 is positioned at the neutral position. For this reason, even when the pressing member 31 moves in the direction in which the lever ratio of the rocker arm 21 increases, the magnitude of the valve operating angle can be controlled.

  DESCRIPTION OF SYMBOLS 1 ... Valve operating apparatus, 2 ... Cylinder head, 3 ... Cam shaft, 4 ... Intake valve, 5 ... Exhaust valve, 6 ... Cam shaft main body, 7 ... 1st cam, 7a, 8a ... Base circular part, 7b, 8b DESCRIPTION OF SYMBOLS ... Nose part, 8 ... 2nd cam, 21 ... Rocker arm, 22 ... Auxiliary arm, 23 ... Pressure receiving part, 24 ... Pressing part, 25 ... Rocker shaft, 27 ... Control arm, 31 ... Pressing member, 32 ... Connecting shaft 33 ... rollers, 34 ... rails.

Claims (6)

A camshaft body rotatably supported by the cylinder head;
Two cams provided on the camshaft body and arranged in the axial direction of the camshaft body;
A rocker shaft provided on the cylinder head in parallel with the camshaft body ;
A rocker arm that is configured to be swingable about the rocker shaft, has a pressure receiving portion that can contact one of the two cams, and has a pressing portion that presses an intake valve or an exhaust valve;
A control arm configured to be swingable around the rocker shaft;
An auxiliary arm supported at the swing end of the control arm so as to be swingable about an axis parallel to the rocker shaft;
A pressing member provided at a swinging end of the auxiliary arm, and positioned between the other cam of the two cams and the rocker arm;
The pressing member is movable in one or the other of the rotation directions of the other cam in accordance with the swinging of the control arm while being sandwiched between the other cam and the rocker arm. Engine valve gear. The valve gear for an engine according to claim 1,
The portion of the rocker arm that is in contact with the pressing member is formed in an arcuate cross section centered on the axis of the camshaft body when the lift amount of the intake valve or exhaust valve is zero. The valve operating device of the engine. The valve operating apparatus for an engine according to claim 1 or 2,
The auxiliary arms are provided at positions sandwiching the control arm from both sides in the axial direction,
The pressing member includes a connecting shaft that is spanned between the two auxiliary arms, and a roller that is rotatably supported at a central portion of the connecting shaft,
Both ends of the connecting shaft are in contact with the rocker arm,
A valve operating apparatus for an engine, wherein the roller rotates in contact with the other cam. The valve operating apparatus for an engine according to any one of claims 1 to 3,
Each of the two cams has a base circle portion where the valve lift amount becomes 0, and a nose portion protruding from the base circle portion by a predetermined protrusion amount outward in the radial direction,
The nose portion of the other cam is formed in a shape in which the maximum valve lift amount is smaller than the maximum valve lift amount of the one cam when the pressing member is moved to a position where the lever ratio of the rocker arm is maximized. A valve operating device for an engine. The valve operating apparatus for an engine according to any one of claims 1 to 3,
The two cams are formed in the same shape,
A position where the contact point between the other cam and the pressing member is biased in a direction in which the lever ratio of the rocker arm is smaller than the contact point between the rocker arm and the one cam as viewed from the axial direction of the camshaft body. The valve operating device of the engine, characterized by being moved by. The valve operating apparatus for an engine according to any one of claims 1 to 5,
And an actuator for rotating the rocker shaft,
The valve operating device for an engine, wherein the control arm is connected to the rocker shaft and swings when the actuator is driven by the actuator.

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