JPS62271916A - Valve operating device for engine - Google Patents

Abstract

PURPOSE:To make valve timing optimum by providing high speed cams and a low speed one in parallel on a cam shaft, and rocker arm sliding parts opposite to each of the said cams, and changing the said cams according to the operating condition of an engine by means of a device for selecting the actuation of each rocker arm. CONSTITUTION:A low speed cam 13 and high speed cams 14a, 14b are provided on one cam shaft 12, and rocker arms 22, 23a, 23b oscillating round a shaft 1 are provided opposite to each cam. The inside of the shaft 1 for the rocker arms is provided with a sleeve 4 having a protrusion 7 which can engage with the inner engaging grooves 17, 26, 27 of the rocker arms, and a spring 8 makes the protrusion 7 of the sleeve 4 constantly engage in the engaging groove 26 of the rocker arm 23b. Thus, the low speed cams 14a, 14b drive suction and exhaust valves during the low speed running of an engine. A control unit 38 changes a solenoid-operated valve 36 according to a signal issued from a sensor 37 for the number of revolutions during the high speed running of the engine to transmit oil pressure generated by a pump 39 to a cylinder 11, and thereby a sleeve 4 is driven to engine the protrusion 7 with the groove 17.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an engine valve train capable of changing valve opening/closing timing, valve lift amount, etc. in accordance with the operating state of the engine.

(Prior Art) In general, in an engine, it is preferable to switch both the valve opening angle and the valve lift amount so that they are small during low-speed operation and large during high-speed operation.
For example, as disclosed in Japanese Utility Model Application Publication No. 57-182205, a low-speed cam and a high-speed cam with different opening/closing timing and lift amount are arranged side by side on a single camshaft for one valve. In addition, the rocker arm is provided with a fixed first contact part that constantly contacts the low-speed cam and a movable second contact part that can contact the high-speed cam only during high-speed operation. Along with this second
A valve train has been proposed in which a rocker arm is provided with an actuator such as a hydraulic cylinder that moves the abutting part of the cam to the abutting part 1 for a high-speed cam.

However, in the above-mentioned configuration, the switching mechanism is not only complicated and unreliable (but also, since the switching mechanism is provided on the rocker arm at a position far from the rocking center of the rocker arm, it is particularly difficult to operate at high speeds). This has the drawback that the inertial mass during operation increases, and the sliding resistance between the rocker arm and the rocker shaft also increases, which diminishes the effect of providing the angle switching mechanism.

(Object of the Invention) In view of the above circumstances, the present invention provides a switching mechanism that can reduce mechanical loss by reducing the inertial mass and sliding resistance, has a simple structure, and is highly reliable. The purpose of this invention is to provide a valve train with improved performance.

(Structure of the Invention) In the valve train according to the present invention, the first or second rocker shaft is located along the axis of the rocker shaft depending on the operating state of the engine.
A sleeve selectively slid by an actuator at a position is rotatably fitted around the outer periphery of the rocker shaft, and the first rocker arm and the second rocker arm move the sleeve onto the rocker shaft. It is supported so as to be able to swing freely. and the sleeve is the first
When the sleeve is in the second position, the first and second rocker arms are held uncoupled so that they can swing independently, and when the sleeve is in the second position, the first and second rocker arms are A retaining portion configured to hold the two rocker arms in a connected state so that they can swing together is provided on the sleeve and the first and second rocker arms. It is characterized by

(Effects of the Invention) In the present invention, since the rocker arm is switched by sliding the sleeve fitted on the rocker shaft in the axial direction, the switching mechanism is simpler than in conventional valve train of this type. It has the advantage of being simple, easy to manufacture, and improving reliability, as well as reducing inertial resistance and sliding resistance of the rocker arm, and reducing mechanical loss.

(Example) The following is an example in which the present invention is applied to a valve train that simultaneously switches two intake valves of a three-valve engine having three valves in one cylinder to low-speed and high-speed pulp characteristics. will be explained in detail.

In Figures 1 to 6, hollow rotocarshaft l-1
is fixed to a cylinder head (not shown) through the fixing cylinder 2.3, and a first sleeve 4 and a second sleeve divided in the axial direction are attached to the outer periphery of the rocker shaft 1. 5 are fitted adjacent to each other so as to be slidable in the axial direction of the rocker shaft 1 and rotatable independently of each other.

The first sleeve 4 has a flange 6 at one end opposite to the second sleeve 5 side, and the second sleeve 5 has a flange 6 that protrudes radially on its outer peripheral surface and has a predetermined length in the axial direction. It is provided with an extending plate-shaped engagement protrusion 7. The first and second sleeves 4.5 have their ends abutted against each other by a sleeve return coil spring 8 interposed between the flange 6 of the first sleeve 4 and the fixing cylinder 2. Axial direction (right side in Figures 1, 4 and 5)
The end 9 of the second sleeve 5 on the side opposite to the first sleeve 4 is inserted into the gap 10 formed in the inner wall of the fixing cylinder 3, and A chamber 11 is formed surrounded by the inner wall surface of B10, the end surface of the sleeve 5, and the outer peripheral surface of the rocker shaft 1. This chamber 11 is a hydraulic chamber to which hydraulic pressure from an actuator, which will be described later, acts. When no hydraulic pressure acts on this chamber 11, the sleeve 4.5 is in the low speed position shown in FIGS. 1 to 5. , due to the action of hydraulic pressure on the chamber 11, it slides and the sixth
It is adapted to move to the high speed position shown in the figure.

On the other hand, the camshaft 12, which is disposed close to and parallel to the rocker shaft l, has one low-speed cam 13 having a shape suitable for low-speed operation of the engine, and one low-speed cam 13 on both sides of the low-speed cam 13. A pair of high-speed cams 14a and 14b having shapes suitable for high-speed operation are arranged adjacent to each other.

A first rocker arm 15 and a second rocker arm 16 are supported on the rocker shaft 1 through a sleeve 4.5 so as to be able to freely swing independently from each other. The rocker arm 15 is provided with an engaging groove 17 that can engage with the retaining protrusion 7 formed on the sleeve 5, but when the sleeve 4.5 is in the low speed position shown in FIGS. In some cases, the rocker arm 15 is rotatably fitted around the outer periphery of the sleeve 4.5 with the interface A-A of the sleeve 4.5 slightly entering the rocker arm 15, and the retaining groove is inserted into the locking groove. 17 is not engaged with the engagement protrusion 7 of the sleeve 5. The first rocker arm 15 is provided with an adjusting bolt 21 at one end thereof, which is bifurcated, for abutting against the upper end of the intake valve 20 to respectively drive the two intake valves 20, and at the other end thereof. is provided with an abutting portion 22 for the low speed cam 13. The second rocker arm 16 does not have a driving end portion of the intake valve 20, but only has abutting portions 23a and 23b for the high-speed cams 14a and 14b, and is disposed on both sides of the first rocker arm 150. Main body part 24a provided
, 24b, and a connecting part 25 that connects these main parts 24a and 24b together, one main part 24a is
The other main body portion 24b is rotatably fitted onto the outer periphery of the second sleeve 4, and the other main body portion 24b is connected to the retaining protrusion 7 formed on the second sleeve 5.
It is provided with an engagement groove 26 that engages with. The main body portion 24b is fitted onto the outer periphery of the sleeve 5 such that the engaging protrusion 7 and the engaging member 'a26 are always engaged with each other regardless of the operating position of the sleeve 4.5. Therefore, the second sleeve 5 is always rocking together with the second rocker arm 16.

Note that a groove 27 is formed in one main body part 24a as well as in the other main body part 24b, but this groove 27 is provided so that the protruding piece 7 can be inserted during assembly. Since it does not contribute to the coherence with 7, it may be omitted. These first and second rocker arms 15,16 are connected to each other by a positioning coil spring 28 interposed between the flange 6 of the sleeve 4 and one main body portion 24a of the second rocker arm 16. The main body portion 24b of the rocker arm 16 is positioned at a position where it comes into contact with the fixing cylinder 3. In this position, rocker arm 15.
Sixteen contact portions 22 and 23a123b are in direct contact with the low-speed cam 13 and the high-speed cams 14a and 14b, respectively. The biasing force of this positioning coil spring 28 is the same as that of the sleeve return spring 8.
The biasing force is set to be weaker than that of . Further, the upper surface of the first rocker arm 15 has a tip end elastically abutting against the connecting portion 25 of the second rocker arm 16, and a second t17.
A leaf spring 2 for constantly bringing the contact portions 23a and 23b of the car arm 16 into contact with the high-speed cams 14a and 14b, respectively.
9 is attached, thereby preventing the generation of noise due to the second rocker arm 16 being in a free state during low speed operation. A plurality of through holes 30 are formed in the peripheral wall of the hollow rocker shaft l, and the rocker Lubricating oil fed into the shaft 1 is supplied between the outer peripheral surface of the rocker shaft 1 and the inner peripheral surface of the sleeve 4.5 through the through hole 30. Furthermore, as is clear from FIGS. 2 to 4, oil grooves 31 are also formed on the inner peripheral surface of the rocker arm 15.16.
．． 32 is formed, and the lubricating oil inside the rocker shaft 1 is
The oil passages 34 and 35 communicate with the hole 33 formed in the peripheral wall of the rocker shaft 1 and are formed inside the fixing cylinder 3 and the main body portion 24b of the second rocker arm 16. The oil is supplied to the groove 31.32 to lubricate the space between the sleeve 4.5 and the rocker arm 15.16.

Furthermore, a hydraulic switching valve 3 constitutes an actuator for intermittent hydraulic pressure to the chamber 11 as a hydraulic chamber to slide the sleeve 4.5 to a low speed position or a high speed position.
6 is provided, and this hydraulic switching valve 36 is controlled by a control unit 38 consisting of a microcomputer operated by a rotation speed sensor 37 that detects the rotation speed of the engine. 39 is an oil pump.

The structure of one embodiment of the engine valve train according to the present invention has been described above, and its operation will now be described.

When the engine is in a low speed operating state, this fact is transmitted from the rotational speed sensor 37 to the control unit 38, and in accordance with the command, the hydraulic pressure switching valve 36 is kept in the closed position, and no hydraulic pressure is applied to the chamber 11. Therefore sleeve 4
．． 5 is in the low speed position shown in FIGS. 1 to 5 due to the urging force of the sleeve return coil spring 8, and the engaging protrusion 7 of the sleeve 5 is engaged in the retaining member 417 of the first rocker arm 15. Since it is not inserted, the first rocker arm 15 is in a state where it can swing independently regardless of the second rocker arm 16. Therefore, the first rocker arm 15 is swung by the low-speed cam 13, and the intake valve 20 is driven with the opening/closing timing and lift amount set by the low-speed cam.

Next, when the engine changes from a low speed operating state to a high speed operating state, this is transmitted from the rotation speed sensor 37 to the control unit 38, and in response to the command, the hydraulic switching valve 36 opens, and oil is supplied from the oil pump 39 into the chamber 11. The hydraulic pressure acts on the sleeve 4.5. As a result, the sleeve 4.5 moves in the axial direction against the biasing force of the sleeve return coil spring 8, resulting in the state shown in FIG. Due to this movement of the sleeve 4.5, the position of the interface A-A of the sleeve 4.5 moves to approximately the center position of the first rocker arm 15, and the retaining protrusion 7 of the sleeve 5 moves to the position of the interface A-A of the first rocker arm 15. Retaining groove 17
the first and second rocker arms 15.1
6 are mechanically connected and integrated via the engaging protrusion 7. In this case, since the cam surfaces of the high-speed cams 14a and 14b are formed so that both the opening angle and the lift amount of the intake valve 20 are larger than the cam surface of the low-speed cam 13, the first The contact portion 22 of the rocker arm 15 no longer contacts the low-speed cam 13, and this integrated port
The car arm 15, 16 is swung by the high-speed cams 14a, 14b that contact the contact portions 23a, 23b of the rocker arm 16, and therefore the intake valve 20 is set by the high-speed cams 14a, 14b. The opening/closing timing and lift amount are determined accordingly. When the engine changes from this high-speed operating state to a low-speed operating state again, the control unit 38 closes the hydraulic switching valve 36, so that no hydraulic pressure acts in the chamber 11, and the sleeve 4.5 is moved to the position shown in FIG. returned to
The retaining protrusion 7 and the first rocker arm 15 are disengaged, and the rocker arm 15 is swung by the low-speed cam 13.

Note that in the above embodiment, the second rocker arm 1
6 is a contact portion 23a for high-speed cams 14a and 14b;
23b, respectively, and a pair of main body parts 24a, 24b connected to each other at a connecting part 25. The reason for this is that during high-speed operation, the point of application of force to the lower car arm 15, 16 is biased, causing mechanical torsion. This is to prevent this from occurring, and functionally one main body portion 24a
Also, the high speed cam 14a can be omitted.

Further, in the above embodiment, by providing the sleeve 4.5 divided into two, the first sleeve 4 can freely rotate with respect to both the rocker shaft l and the rocker arm 15.16. Because of this, the circumferential speed between them can be lowered, and the sliding resistance can therefore be further reduced.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the valve train according to the present invention when the engine is in a low speed operating state, FIG. 2 is a sectional view taken along line 1] in FIG. 1, and FIG. [A cross-sectional view taken along the line, Figure 4 is a cross-sectional view taken along line IV-IV in Figure 1, Figure 5 is a cross-sectional view taken along line V-V in Figure 2, Figure 6 shows the engine in high-speed operation. FIG. 6 is a cross-sectional view corresponding to FIG. 5 showing the valve train according to the present invention when the valve train is in the state of FIG. 1.-Rocker shaft 4-First sleeve 5--
Second sleeve 7 - Engagement protrusion 8 - Sleeve return coil spring 11 - Chamber
12... Camshaft 13 - Low speed cam 14 aSl 4 b - High speed cam 15 - First rocker arm 16... Second rocker arm 17.26... Engagement groove 28... For positioning Coil spring 36 - Hydraulic switching valve 38 - Control unit 39 - Oil pump

Claims (1)

[Claims] Rotatably fitted around the outer periphery of the rocker shaft, and
a sleeve that is selectively slid by an actuator to a first or second position along the axis of the rocker shaft depending on the operating state of the engine; and a sleeve that is swingably supported on the rocker shaft via the sleeve. a first rocker arm; and a second rocker arm that is swingably supported on the rocker shaft via the sleeve, and when the sleeve is in the first position, the first rocker arm and the second rocker arms are held uncoupled so that they can swing independently, and when the sleeve is in the second position, the first and second rocker arms are held together so that they can swing independently; A valve train for an engine, characterized in that an engaging portion configured to hold the sleeve and the first and second rocker arms in a rockingly connected state is provided on the sleeve and the first and second rocker arms.