JPH053690Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an overhead valve type valve train for an engine.

(Prior Art) As is well known in the art, an overhead valve type valve train for an engine is driven by a valve cam that is driven in conjunction with a crankshaft, and a synchronized valve cam. The push rod includes a tappet and a push rod that is driven by the tappet and opens and closes the intake valve and/or exhaust valve of the engine via a rocker arm, and controls the opening/closing timing and lift of the intake valve and/or exhaust valve. Pattern (In this specification, lift pattern refers to the shape of a lift curve in a valve lift diagram in which time or crank angle is plotted on the horizontal axis and valve lift is plotted on the vertical axis.) is determined by the shape of the valve operating cam, substantially independent of the engine load and engine speed.

(Problem to be solved by the invention) Engines for vehicles, especially automobiles, operate over a wide range of speeds, from idle speed to maximum speed, and under frequently changing speeds and load conditions. It is driven by. In general, the amount of air intake required to obtain excellent engine performance, ie, output, fuel efficiency, etc., in other words, the opening/closing timing of the air intake valve and the lift pattern, are different between when the engine is rotating at low speed and when it is rotating at high speed. Therefore, in order to obtain desired engine performance at low and high speeds, it is desirable to change the opening/closing timing and lift pattern of the intake valve depending on the engine operating condition.
Similarly, by changing the opening/closing timing and lift pattern of the exhaust valve, the exhaust resistance changes, which also has a considerable effect on engine performance. The present invention is designed to:
To provide a valve train capable of improving engine performance by changing the opening/closing timing and lift pattern of an intake valve and/or exhaust valve, and to ensure quiet operation of the valve train. The purpose is to

(Means for solving the problem) The present invention was devised to achieve the above object, and is driven by a valve cam that is driven in conjunction with the engine crankshaft, and a synchronized valve cam. a push rod which is driven by the tappet to open and close at least one of the intake valve and exhaust valve of the engine; one end of each is interposed between the tappet and the valve operating cam, and the other end is interposed between the tappet and the valve operating cam; first and second swing arms pivotally supported on substantially parallel first and second axes, by moving at least one of the swing arms in a direction substantially perpendicular to the axes; The device is characterized by comprising means for changing the contact position between the one end portion and the valve drive cam, and a spring member that elastically presses the first and second swing arms against the tappet or the valve drive cam. The gist of this paper is a valve train for an engine.

(Function) According to the above-described configuration of the present invention, the relative positions of the first axis and the second axis that pivotally support the first and second swing arms, respectively, with respect to the valve operating cam can be changed depending on the operating state of the engine. Accordingly, the position of the contact point between each arm and the valve drive cam can be changed, and the opening/closing timing and lift pattern of the intake valve and/or exhaust valve can be changed. Further, since a spring member is provided that elastically presses the first and second swing arms against the tappet or the valve cam, one of the swing arms moves freely during the valve lift period, and the tappet Also, impacting contact with the valve train cam and generation of knocking noise that causes engine noise is prevented.

(Embodiment) An embodiment of the present invention will be specifically explained below with reference to the accompanying drawings. First, in the basic configuration of the present invention shown in FIGS. A valve operating cam driven in conjunction with the shaft (either an intake cam or an exhaust cam that opens and closes the intake valve and exhaust valve, respectively), 12 is a tappet, and 14 is a push rod, the push rod is not shown. Its upper end is operatively abutted against one end of the rocker arm, and the other end of the rocker arm is operatively abutted against the top of the valve stem of the intake or exhaust valve. One end of the first swing arm 16 and one end of the second swing arm 18 are interposed between the valve operating cam 10 and the lower surface 12' of the tappet 12, and the other end of the first swing arm 16 is , the other end of the second swing arm 18 is pivotally connected to a first eccentric shaft portion 22 on the drive shaft 20, and the other end of the second swing arm 18 is pivotally connected to a second eccentric shaft portion 24 on the drive shaft 20. (It goes without saying that the drive shaft 20 is shown for only one cylinder, but it can be common to a plurality of cylinders, similar to the valve drive cam.)
The axis O ₁ (first axis) of the first eccentric shaft portion 22 is eccentric by e ₁ with respect to the axis X of the drive shaft 20, and the axis O ₂ (second axis) of the second eccentric shaft portion 24 is eccentric. , is eccentric by e ₂ on the opposite side with respect to the axis X of the drive shaft 20. (Note that the eccentricities e ₁ and e ₂ may be equal.) Furthermore, the upper surface 16' of the one end of the first swing arm 16 is formed into a cylindrical surface,
It cooperates with the lower surface 12' of the tappet, which is a cylindrical surface concentric with the valve cam 10, and the swing arm 16.
The lower surface of the valve cam 10 is bounded by a rotatably mounted roller 26 which cooperates with a cam-acting surface 10' provided on the outer periphery of the valve cam 10. Similarly, the upper surface 18' of said one end of the second swing arm 18 is formed as a cylindrical surface and cooperates with the above-mentioned lower tappet surface 12', and the lower surface is bounded by a roller 28, which roller 28 cooperates with the cam action surface 10' of the valve drive cam 10. On the other hand, the drive shaft 20 is rotated around the axis X by a suitable actuator, and in the illustrated embodiment, the actuator includes an air cylinder 32 containing a piston connected to a rack rod 30, and an air cylinder 32 that incorporates a piston connected to a rack rod 30. Although the pinion 34 meshes with the rod 30 and is fixed to the drive shaft 20, any actuator such as a rotary solenoid or a step motor may be used.

In the above configuration, the valve lift diagram of the intake valve or the exhaust valve when only a single swing arm, for example, the first swing arm 16 is operated, is as shown by the solid line A in FIG. 4. That is, the valve train cam 10 is the first
The cam action surface 1 rotates in the direction shown by arrow C in the figure.
0' comes into contact with the roller 26, the first swing arm 16 rotates clockwise around the first axis _O1 , and the upper surface 16', which is a cylindrical surface of the swing arm, rotates clockwise around the first axis O1.
slides against the cylindrical lower surface 12' of the tappet 12 and pushes it up, and then via the push rod 14 and the locker arm (not shown),
The intake valve or exhaust valve lifts. next,
1 and 3 show the amount of offset in the lateral direction between the first axis O1, which is the center of rotation of the first swing arm 16, and the second axis _{O2 ,} which is the center of rotation of the second swing arm 18. is the maximum value (e ₁ + e ₂ ), and the roller 26 of the first swing arm and the second
The roller 28 of the swing arm contacts the base circle of the valve operating cam 10, and thus the cam action surface 10', at the two contact lines P ₁ and P ₂ that are approximately the most distant from each other. (Geometrically, the axis O ₁ of each swing arm,
Since the plane passing through O ₂ and the contact lines P ₁ and P ₂ is inclined with respect to the horizontal plane in _FIG .
When the amount of lateral offset between O ₂ is maximum,
Although the distance between P ₁ and P ₂ is not necessarily the maximum,
The error is small and approximately as described above. )
When the first and second swing arms 16 and 18 are in this position, the rotation of the valve operating cam 10 in the direction of arrow C causes the roller 28 of the second swing arm 18 to first come into contact with the cam action surface 10'. Tappet 1
2. The air supply valve or exhaust valve is lifted via the push rod 14. The valve lift diagram due to the second swing arm 18 is as shown by the dotted line B in FIG.
is in contact with the cam action surface 10', so the valve lift diagram ends up being curve B in the first half and curve A in the second half.
becomes effective, and the curve B and the curve A are superposed in total. As a result, the total area of the valve lift curve is increased compared to when only a single swing arm is used (or when the tappet 12 is directly driven by the valve operating cam 10 as before), and the valve opening timing is advanced. becomes. It is obvious that an increase in the total area of the valve lift curve means an increase in the amount of air supply in the case of an intake valve, and a decrease in exhaust resistance in the case of an exhaust valve. Next, the air cylinder 32 is operated and the pinion 3 is moved by the rack rod 30.
4, the drive shaft 20 is rotated 90 degrees clockwise or counterclockwise, the axis O ₁ of the first swing arm 16 and the axis O ₂ of the second swing arm 18 are aligned with the drive shaft 20. is included in the vertical plane passing through the axis X of . At this time, the first and second swing arms 16 and 18 extending in the horizontal direction and the valve operating cam 10
The distance between the contact lines P ₁ and P ₂ becomes approximately minimum, the valve lift curves A and B in Fig. 4 approach in the horizontal axis direction, and the area surrounded by both curves becomes smaller. . At this time, by appropriately selecting the eccentricities e ₁ and e ₂ and the lengths of the swing arms 16 and 18, the contact lines P ₁ and P ₂ can be made to coincide;
In this case, the valve lift diagram will be curve A or B alone. Therefore, depending on the characteristics of the engine, the first
By appropriately selecting the lengths of the second swing arms 16 and 18, the eccentricities e ₁ and e ₂ of the first and second axes, and the shape of the working surface 10' of the valve cam 10, By selecting a well-known three-position air cylinder 32 for the air cylinder 32, it is possible to obtain the desired excellent performance when the engine rotates at low speeds and at high speeds. For example, it is possible to measure performance improvements such as output and fuel efficiency at low, medium and high speeds.

Now, returning to FIG. 1 again, when the valve operating cam 10 rotates from this state, the roller 28 of the second swing arm 18 comes into contact with the cam action surface 10' and rises to the tappet 12, but during this time the first The swing arm 16 is freely moving. Subsequently, the first swing arm 16 operates from around the highest position in the valve lift diagram of FIG. 4 until the valve is closed, and the second swing arm 18 is idle. For example, as shown in FIG. 2, there is play E between the upper surface 18' of one end of the second swing arm 18 and the lower surface 12' of the tappet 12 near the highest position of the valve lift. Therefore,
At this time, the second swing arm 18 can swing freely within the range of free play E, and rotates following engine vibrations, vehicle body vibrations, and rotation of the valve drive cam 10 that occur during driving. Due to various causes such as inertia during operation, the roller 28 impacts the outer peripheral surface of the cam 10, and its upper surface 18' impacts against the lower surface 12' of the tappet (particularly the latter), producing unpleasant noise. and accelerates wear and tear on the collision surface. This means that
The same applies not only to the second swing arm 18 but also to the first swing arm 16 which is idle during the valve lift increasing stroke. Therefore, as a feature of the present invention, as shown in FIG.
A torsion spring 36 is attached to the swing arms 16 and 18, and one end 36a of the torsion spring 36 is latched to the lower surface of the swing arm, and the other end 36b is latched to a step provided on a surrounding engine structural member, such as a crankcase 38, and the torsion spring 36 is twisted. A torsional preload is applied to the spring 36, and the swing arm 16,1 is moved as shown by arrow F in the figure.
8 is always clockwise, that is, the lower surface 1 of the tapepet 12
2'. With this configuration, the first and second swing arms 1
6 and 18 during their free movement during the lift period, this prevents them from shockingly abutting against the lower surface 12' of the tappet 12 or the outer circumferential surface of the valve operating cam 10 and generating unpleasant noise, and also prevents the cam action from occurring. surface 10', lower surface 12' of the tappet, upper surface 16' of the swing arm and 1
8', as well as the rollers 26, 28, etc., can be prevented from being worn out. It is obvious that a coil spring, a leaf spring, etc. can be used instead of the torsion spring 36, and the swing arms 16 and 18 can be biased in the opposite direction to the above to apply elasticity to the outer peripheral surface of the valve drive cam 10. It is clear that substantially the same effect can be achieved even if the two are pressed together.

Furthermore, in the embodiment described above, the axis O ₁ of the first swing arm 16 and the second swing arm 18
The axis O ₂ of the drive shaft 20 is eccentric to the axis X of the drive shaft 20, but the point is that the axes of both swing arms 16 and 18 only need to be eccentric relative to each other, The axis of one of the swing arms may be a fixed axis, and the axis of the other swing arm may be an axis that is parallel and eccentric to the fixed axis. Further, in the embodiment described above, the lower surface 12' of the tappet 12 is formed into a cylindrical surface concentric with the valve operating cam 10, but it may of course be formed into a simple flat surface.

(Effects of the invention) As described above, the present invention has a valve cam driven in conjunction with the engine crankshaft, a tappet driven by the synchronized valve cam, and an engine driven by the tappet. a push rod that opens and closes at least one of the intake valve and the exhaust valve, one end of which is interposed between the tappet and the valve operating cam, and the other end of which is located on substantially parallel first and second axes; first and second swing arms respectively pivoted to;
means for changing the contact position between the one end and the valve operating cam by moving at least one of the swing arms in a direction substantially perpendicular to the axis; It is characterized by comprising a spring member that elastically presses against the tappet or valve drive cam, and changes the opening/closing timing and lift pattern of the intake valve and/or exhaust valve according to the operating state of the engine. This improves engine performance and prevents noise and damage to the collision surface caused by the loose one of the two swing arms colliding with the tappet or valve drive cam during the valve lift period. This is useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a side view of a valve train in which the present invention is to be implemented, FIG. 2 is a side view showing the state of the valve train in FIG. 1 during a valve lift period, and FIG. 3 is a line drawn along the line 4 is a valve lift diagram of the device shown in FIGS. 1 to 3, and FIG. 5 is a side view showing an embodiment of the present invention. 10... Valve train cam, 10'... Cam action surface, 1
2... Tappet, 14... Pushrod, 16
...First swing arm, 18...Second swing arm, 20...Drive shaft, 22...First eccentric shaft section, 24...Second eccentric shaft section, 26 and 28...Roller, 32...Air Cylinder, 36...Torsion spring, 38...Crankcase.

Claims (1)

[Scope of utility model registration request] A valve cam that is driven in conjunction with the engine crankshaft, a tapepet that is driven by the synchronized valve cam, and a push rod that is driven by the tappet and opens and closes at least one of the engine's intake valves and exhaust valves. , first and second swing arms whose respective one ends are interposed between the tappet and the valve drive cam, and whose other ends are pivotally supported on substantially parallel first and second axes, respectively; , means for changing the abutting position of the one end portion and the valve operating cam by moving at least one of the swing arms in a direction substantially perpendicular to the axis; A valve train for an engine, comprising a spring member that elastically presses against the tappet or valve train cam.