JP2753208B2 - Engine valve gear - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for an engine capable of changing a lift amount and a valve opening period of an exhaust valve. [0002] When operating characteristics of intake and exhaust valves of an engine are set, at low speeds, combustion stability and fuel consumption are reduced by suppressing exhaust blow-back and intake blow-through during a valve overlap period. It is desirable to make the valve lift amount and the valve opening period relatively small for improvement, and it is desirable to increase the valve lift amount and the valve opening period for high output at high speeds. In order to satisfy such a demand, two types of cams having different shapes are provided, a valve is selectively linked to one of these cams, and the linkage is switched according to the operation state. A valve gear is conventionally known, and as this kind of valve gear, for example, Japanese Utility Model Laid-Open No.
No. 182205, U.S. Pat. No. 4,205,634, and U.S. Pat. No. 4,151,817, respectively. The device disclosed in Japanese Utility Model Laid-Open Publication No. 57-182205 has two low-speed and high-speed cams and one rocker arm for one valve. A high-speed cam contact member slidable on the other end while a side portion is formed in a forked shape and one end of which is used as a contact portion with the low-speed cam, and a stopper for preventing the slide. The stopper is operated by an actuator such as a hydraulic cylinder via an interlocking mechanism. By controlling the actuator in accordance with the operating state, the high-speed cam contact member moves freely at low speed, the operation of the high-speed cam is not transmitted to the valve, and the valve is operated by the low-speed cam. The sliding of the cam contact member is prevented, and the operation of the high-speed cam is transmitted to the valve. In the apparatus disclosed in US Pat. No. 4,205,634, three low-speed and high-speed cams are symmetrically arranged for one valve, and one valve is controlled by cams on both sides. It is possible to switch between a driving state and a driving state by a center cam. For example, in the example shown in FIG. 13, one rocker arm having a contact portion with a valve is provided, and the rocker arm and the cam are provided. A finger that can move forward and backward is provided between the two parts, and the two states are switched by operating the finger by a driving unit. In the apparatus disclosed in US Pat. No. 4,151,817, three low-speed and high-speed cams are symmetrically arranged for one valve, and a link having a cam follower surface for the cams on both sides. And a rocker arm having a cam follower with respect to the center cam, and the cam follower is movable or fixed with respect to the link by a latch mechanism. It can be switched to a driving state. [0007] With the recent increase in engine output, it is conceivable to provide two intake valves or exhaust valves per cylinder. It is desirable that the valve lift characteristics of the valve can be changed according to the operating state. However, simply applying the above-described conventional technology to such an engine simply requires two or three cams and a drive state switching mechanism for each of two valves per cylinder. And need
There is a problem that the structure becomes very complicated. In view of such circumstances, the present invention can switch the valve lift characteristics of two intake valves or exhaust valves per cylinder between low speed and high speed.
It is an object of the present invention to provide an engine valve train that can switch the valve lift characteristics of the two valves with a simpler structure. In order to achieve the above object, the present invention provides two types of cams, a low speed type and a high speed type, for at least one of an intake valve and an exhaust valve for each cylinder. And a swing member having a predetermined portion as a swing fulcrum is arranged between the cam and the valve, and the valve is selectively linked to one and the other of the two types of cams. In a valve operating device for an engine provided with a switching mechanism for switching the linkage in accordance with an operation state, two valves are provided for each cylinder, and the two types of cams are disposed on a common camshaft. And the center cam are high-speed cams, the center cam is a low-speed cam whose cam profile is smaller than the high-speed cam.
The center cam is disposed in the middle of the valve, and the swing member is brought into contact with the cams on both sides and the first swing member having a portion supported by the swing shaft, and the center cam. The first and second swing members are divided into a second swing member having a portion in contact with and supported by the swing shaft and a portion in contact with each of the two valves, and the switching mechanism separates the first and second swing members from each other. By switching between a linked state and a non-linked state with respect to the corresponding cam, a state in which the center valve drives the two valves via the second swinging member, and a state in which the cams on both sides are the first and second valves. It is configured to switch to a state in which the two valves are driven via a second swing member. According to the above construction, the state in which the two valves are simultaneously driven by the central low-speed cam via the swinging member and the state in which the two valves are simultaneously driven by the high-speed cams on both sides. This makes it possible to change the valve lift characteristics of the two valves while simplifying the structure as compared with a case where two types of cams, swing members, and the like are individually provided for each valve. Further, the swing member disposed between the two valves and the three cams is divided into first and second swing members, and the first swing member abuts the cams on both sides to swing. While having a portion supported by the shaft, the second swinging member has a portion abutting on the center cam and supported by the swinging shaft and a portion abutting on each of the two valves, Driving of the two valves is effectively performed with a compact structure. Further, since the first and second swing members are configured as described above, and the center cam is arranged between the two valves in the cam axis direction, the inclination of the second swing member is reduced. Is prevented, and the stability of the valve drive is increased. An embodiment of the present invention will be described with reference to the drawings.
1 to 4 show an embodiment of the device of the present invention. In this embodiment, the number of intake valves is two per cylinder, and the device of the present invention is applied to the intake valves. In these figures, 1 is a cylinder, 2a and 2b are two intake valves provided in the cylinder 1, and the exhaust valve and its drive system are not shown. The above two intake valves 2
a and 2b, three cams 3a, 3b and 4 are arranged on a common camshaft 5, and
A rocker arm (swing member) 6 having a predetermined portion as a swing fulcrum is disposed between the intake valves 2a and 3b and the intake valves 2a and 2b. The above-mentioned three cams are arranged such that one of two types of cams, a low-speed type and a high-speed type, is disposed on both sides, and the other is disposed at the center.
b, the center is the low-speed cam 4. The low-speed cam 4 is disposed at a position corresponding to a substantially center of the rocker arm 6 in the width direction so as to be located between the two valves in the cam axis direction. The high-speed cams 3a and 3b are low-speed cams. 4 are symmetrically arranged on both sides. The above high-speed cam 3
a, 3b and the low-speed cam 4 are formed in different shapes (including similar shapes having different sizes) so as to satisfy the valve lift characteristics required at high speed and at low speed, respectively. The cams 3a and 3b are low-speed cams 4.
The cam nose is increased so as to increase at least one of the valve lift amount and the valve opening period. In this embodiment, the profile of the low-speed cam 4 is such that the high-speed cams 3a, 3b
These cams 3a, 3b, 4 are formed so as to fit all inside the profile. The rocker arm 6 has a first arm (a first swing member) having a portion that comes into contact with the cams 3a and 3b on both sides and a portion that is supported by a rocker shaft (swing shaft) 9. 7, a portion which abuts on the center cam 4 and is supported by the rocker shaft 9, and the two intake valves 2
and a second arm (second swinging member) 8 having a portion that comes into contact with each of a and 2b. The rocker arm 6 is provided with a switching mechanism that switches the linkage between the cam and the valve. By the switching mechanism, the first and second arms 7 and 8 are switched between a linked state and a non-linked state with respect to the corresponding cams, respectively. The state where the valves 2a and 2b are driven and the state where both intake valves 2a and 2b are driven by the cams 3a and 3b on both sides via the first and second arms 7 and 8 can be switched. More specifically, the rocker arm 6 includes a pair of left and right arm portions 7 that abut on both high-speed cams 3a and 3b.
a, 7b and an upper connecting portion 7c integrated with each other.
Arm 7 and contact portion 8 to both intake valves 2a, 2b
a, 8b and a second arm 8 integrally provided with a contact portion 8c for contacting the low-speed cam 4.
8 is supported so as to be able to move relative to the rocker shaft 9 and one arm thereof, for example, the first arm
A selector (switching mechanism) 10 including a plunger 11 and a lever member 12 is incorporated in the arm 7. The selector 10 is provided with two arms 7, 8
It is possible to switch between a connection state in which relative movement of the arm is prevented and a non-connection state in which relative movement of both arms 7, 8 is allowed,
Specifically, it has the following structure. That is, a guide hole 13 that opens toward the upper part of the second arm 8 is formed in the upper part of the first arm 7, and the plunger 11 is movably accommodated in the guide hole 13. Second by the spring 14 inside
It is urged to abut the arm 8, and a small diameter engaging portion 15 is formed in the middle of the plunger 11.
The lever member 12 is supported on the upper part of the first arm 7 so as to be movable in the axial direction of the rocker shaft 9 at right angles to the plunger 11, and the lever member 12 has a slightly larger diameter than the plunger 11. Plunger insertion hole 1
6 and an engagement hole 17 having a size corresponding to the engagement portion 15 and connected to the plunger insertion hole 16 are formed.
In this manner, when the lever member 12 moves to the lock position where the locking hole 17 of the lever member 12 engages with the engaging portion 15 of the plunger 11, the sliding of the plunger 11 is prevented. , 8 are prevented from moving relative to each other in the direction in which they approach each other (in this case, the connected state),
On the other hand, when the locking member 17 is disengaged from the engaging portion 15 and the lever member 12 moves to the unlocked position where the plunger 11 is inserted into the plunger insertion hole 16, the sliding of the plunger 11 is allowed. The relative movement of the arms 7 and 8 is allowed (in this case, a disconnected state). The end of the lever member 12 is the first arm 7
And is connected via an arm 12a to an annular hydraulic actuator 20 rotatably supported around the rocker shaft 9, and the actuator 20 is connected to a hydraulic chamber 21 by an oil pump (not shown). When the oil is supplied from the oil passage 22 through the oil passage 22, the lever member 12 is moved toward the lock position,
When the oil is relieved from 1, the return spring 23 moves the lever member 12 toward the unlocked position. And the rotation speed signal 2
The supply and discharge of the oil to and from the hydraulic chamber 21 are controlled by a control circuit 25 that receives the control signal 4 and the like via a control valve 26 in the oil passage 22.
For example, the lever member 12 is operated to the locked position at a high speed higher than a predetermined rotation speed, and the lever member 12 is operated to the unlocked position at a low speed lower than the predetermined rotation speed. The actuator that operates the lever member 12 is not limited to the hydraulic type described above, and a solenoid or the like may be used.
The control of the actuator according to the operating state may be performed according to the engine speed and the load. Reference numeral 27 denotes an adjuster provided at one end of the second arm 8 so as to face the intake valve 2, and reference numeral 28 denotes an adjuster provided at an upper portion of the second arm 8 so as to face the plunger 11. The clearance is adjusted. Reference numeral 29 denotes a cylinder head. According to this valve train, when the engine is running at a high speed, the lever member 12 is operated to the locked position to prevent the plunger 11 from sliding.
When the second arm 8 is pushed by the cam nose of the high-speed cams 3a and 3b and swings, the second arm 8 separates from the low-speed cam 4 and
High-speed cams 3a and 3b for swinging together with arm 7
The intake valves 2a and 2b are operated in accordance with the rotation of. On the other hand, at low speed, the lever member 12 is in the unlocked position and the plunger 11 is allowed to slide, so that the swing of the first arm 7 accompanying the rotation of the high-speed cams 3a, 3b is absorbed by the plunger 11. As a result, the intake valves 2a and 2b are actuated by the swing of the second arm 8 in accordance with the rotation of the low-speed cam 4 without being transmitted to the second arm 8. In this way, the valve lift characteristics are changed to suit the operating conditions. The two intake valves 2
While a and 2b can be changed to a high-speed valve lift characteristic and a low-speed valve lift characteristic, three cams are provided for the two valves, and the second arm 8 is operated when the central cam 4 operates the valve. Since both intake valves 2a and 2b are simultaneously operated via the second arm 8 and a mechanism for switching the linked state between the second arm 8 and the cams 3a and 3b on both sides, each intake valve 2a , 2b are provided with two types of cams and a switching mechanism individually.
The valve gear has a simple and compact structure. Also, as in this embodiment, each of the cams 3a,
If the rockers 3b and 4 and the rocker arm 6 are arranged symmetrically, the force from the low-speed cam 4 acts on the center of the rocker arm 6 in the approximate width direction at a low speed, and the two high-speed cams 3 at a high speed.
Since the resultant force from a and 3b acts on the center of the rocker arm 6 substantially in the width direction, the force from the cam is not biased to one side of the rocker arm 6 in any case, and
Can be prevented. Further, according to this embodiment, the central low-speed cam 4 is connected to the high-speed cams 3a, 3 on both sides.
Since the cam profile is smaller than b, the two high-speed cams 3a and 3b can be simultaneously machined along the axial direction without being disturbed by the low-speed cam 4 during cam machining, thereby facilitating machining. become. Further, if the widths of the two high-speed cams 3a and 3b are matched, the width of the two high-speed cams 3a and 3b becomes larger than the width of the low-speed cam 4;
Increase in the surface pressure at the contact portion with the contact member can be suppressed. Therefore, the two high-speed cams 3a and 3b can be reliably brought into contact with the rocker arm 6 equally, so that the one-side contact can be prevented. In the above embodiment, a case where the present invention is applied to an intake valve of an engine having two intake valves 2a and 2b in one cylinder has been described. However, the device of the present invention employs two exhaust valves in one cylinder. May be applied to an exhaust valve of an engine equipped with an intake valve and an intake valve and an exhaust valve.
In the case of an engine provided individually, the present invention may be applied to each of the intake valve and the exhaust valve. As described above, according to the present invention, two types of cams, a low-speed type and a high-speed type, are arranged on a common cam shaft for two intake valves or exhaust valves per cylinder. In addition to the three cams, the swinging member is divided into a first swinging member that abuts the cams on both sides and a second swinging member that abuts on the center cam. 1st, 2nd
The rocking members are switched between a linked state and a non-linked state with respect to the corresponding cams, so that the valve lift characteristics of the two valves can be changed with a simple structure. In particular, the cams on both sides are high-speed cams,
The center cam is a low-speed cam, and the center cam is disposed between two valves in the cam shaft direction, and the first swing member abuts the cams on both sides and is supported by the swing shaft. The second swing member has a portion that abuts the center cam and is supported by the swing shaft and a portion that abuts each of the two valves. Since it is configured to switch between a state in which the two valves are driven via the moving member and a state in which the two valves are driven via the first and second swing members by the cams on both sides, it is compact and simple. With this structure, the tilting of the swing member can be prevented, and the two valves can be driven stably. In addition, there is an advantage that machining is facilitated by using high-speed cams on both sides and low-speed cams in the center.

[Brief description of the drawings] FIG. 1 is a plan view showing an embodiment of the device of the present invention. FIG. 2 is a sectional view taken along line II-II of FIG. FIG. 3 is a sectional view taken along line III-III of FIG. 1; FIG. 4 is a vertical sectional front view at a rocker shaft position. [Explanation of symbols] 2a, 2b Intake valve 3a, 3b High-speed cam 3 Low-speed cam 6 Rocker arm 7 First arm 8 Second arm 10. Selector (switching mechanism)

Claims (1)

(57) [Claims] A swing member having a low-speed type and a high-speed type cam provided for at least one of an intake valve and an exhaust valve for each cylinder, and a predetermined portion serving as a swing fulcrum between the cam and the valve. And a switching mechanism for selectively linking the valve to one and the other of the two types of cams and switching the link depending on the operating state. 1
In addition to two valves per cylinder, the two types of cams are composed of three cams, a cam on both sides and a central cam disposed on a common camshaft. The cams on both sides are high-speed cams, The center cam is lower than the high-speed cam with a lower cam profile.
Speed cam , with the upper halfway between the two valves in the camshaft direction
The serial central cam arranged, and the swinging member, both rhino
Having a portion that abuts against the cam of the arm and is supported by the swing shaft .
Abuts the swinging member and the center shaft and is supported by the swinging shaft.
And a portion that contacts each of the two valves.
Divided into a second oscillating members that, thereby the switching mechanism
And the first and second swing members with respect to the corresponding cams, respectively.
By switching between the linked state and the non-linked state, the center cam drives the two valves via the second swing member, and the cams on both sides allow the first and second swings. Element
A valve train for an engine, which is configured to switch to a state in which the two valves are driven via the control valve.