JPH0565684B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a valve adjuster that automatically adjusts the clearance between a cam and a rocker arm when a valve is closed in a valve operating mechanism of an internal combustion engine.

[Conventional technology]

In internal combustion engines (hereinafter referred to as engines),
Due to factors such as thermal expansion of various parts during operation and changes over time such as wear, the clearance between the rocker arm and the engine valve or the clearance between the rocker arm and the cam when the valve is closed may change.

If this clearance changes, the degree of opening of the valve, that is, the valve lift, valve opening period, etc., may be disturbed, and the output performance and economic efficiency of the engine may deteriorate.

In order to eliminate such a fear, there is a device that can automatically adjust the above-mentioned clearance by using hydraulic pressure to raise and lower a pivot that pivots the base end of the rocker arm.

[Problem to be solved by the invention]

Since the conventional valve adjuster as described above uses hydraulic pressure, it is necessary to drill a flow path for supplying pressure oil in the cylinder head and connect a pressure oil pipe line to the cylinder head. There are problems such as a complicated structure and insufficient responsiveness.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a valve adjuster for a valve train of an internal combustion engine that has a simple structure and good responsiveness.

[Means to solve the problem]

In order to achieve the above object, the valve adjuster in the valve operating mechanism for an internal combustion engine of the present invention is provided on a camshaft that rotates in synchronization with the crankshaft, on the upper surface of the intermediate portion of a rocker arm whose base end is pivotally supported on the cylinder head. In a valve operating mechanism for an internal combustion engine, a cam is slidably contacted, and the rotation of the cam rotates the rocker arm, and the tip of the rocker arm pushes the shaft end of an engine valve to open the valve. A valve adjuster that adjusts the clearance between the cam and the rocker arm when the rocker arm is rotated, and a pivot that pivotally supports the base end of the rocker arm.
an advancing/retracting device that advances and retreats from the cylinder head toward the cam side; a spring that biases the rocker arm in a direction that constantly presses the rocker arm against the shaft end of the engine valve;
A displacement sensor supported by a cylinder head facing the upper surface of the rocker arm and constantly measuring the distance to the opposing surface of the rocker arm, a minimum value of the distance measured by the displacement sensor, and a preset setting value. The present invention is characterized by comprising a control device that controls the advancing/retracting device so that the difference is small.

[Effect]

When the internal combustion engine is operating, the camshaft rotates in synchronization with the crankshaft, and the rotation of the cam at this time pushes down the upper surface of the middle part of the rocker arm, causing the rocker arm to rotate about the pivot and rotate its tip. At this point, the shaft end of the engine valve is pushed to open the valve.

The displacement sensor constantly measures the distance to the opposite surface of the rocker arm.

In the control device, the minimum value of the measured value measured by the displacement sensor and the set value are compared, and the advancing/retracting device is controlled so that the difference between them becomes small.

In other words, when the minimum measured value is greater than the set value, the advancing/retracting device is controlled so that the pivot that supports the base end of the rocker arm advances toward the cam, and conversely, the set value is larger than the minimum measured value, the advancing/retracting device is controlled so that the pivot moves away from the cam.

As a result, the bottom surface of the cam when the valve is closed,
The clearance between the upper surface of the rocker arm facing it is always maintained constant.

The setting value in the control device is preferably set so that this clearance is close to zero.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

Reference numeral 1 designates an engine valve serving as an intake valve, and an intermediate portion of a vertically oriented shaft portion 1a is guided by a valve guide 2 so as to be movable up and down.

A valve spring 5 is compressed between the cylinder head 4 and the retainer 3, which is secured to the upper end of the shaft portion 1a via a lever (not shown).
This valve spring 5 allows the engine valve 1 to have an umbrella portion 1b at the lower end of its shaft portion 1a.
It is constantly biased upward so as to close the valve opening formed by the valve seat 6.

An arcuate pressing surface 7a formed on the lower surface of the distal end of a rocker arm 7 facing perpendicularly to the shaft portion 1a is pressed into contact with the upper end of the shaft portion 1a.

The rocker arm 7 has a spherical recess 7b provided on the lower surface of its base end connected to the upper end of a screw 9 which is screwed into a vertically facing screw hole 8 bored in the cylinder head 4 via an annular groove 10a. It is pivotally connected by fitting into a spherical head-shaped pivot 10 that is connected to the shaft.

Reference numeral 11 denotes a spring whose side surface is bent into a horizontal U-shape, and its base end is rotatably fitted into the annular groove 10a, and its tip end is engaged with the upper surface of the middle part of the rocker arm 7. The rocker arm 7 is urged in a direction in which the rocker arm 7 is always pressed against the shaft end of the engine valve 1.

A small-diameter pinion 12 is connected to the lower end of the screw rod 9, and this pinion 12 has a rack 14 fitted into a horizontal receiving hole 13 formed in the cylinder head 4 so as to be slidable in the left and right direction. They mesh together.

As clearly shown in FIG. 3, the left end of the crack 14 is provided with a protruding piece 14a facing rearward, and a left-right screw hole 1 provided in this protruding piece 14a.
A screw rod 16 facing in the left-right direction and fixed to the rotating shaft of a motor 15 attached to the left end of the cylinder head 4 is screwed into the cylinder head 7 .

The right end of the screw rod 16 is rotatably supported on a step 13a formed in the middle of the receiving hole 13.

Screw rod 9, pinion 12, rack 14, screw rod 1
6, a motor 15, and the like form an advancing/retracting device 18 that moves the pivot 10 in the vertical direction.

That is, when the motor 15 rotates the screw rod 16 in the direction in which the rack 14 moves to the left, the screw rod 9
is raised and pivot 10 is raised.

Further, when the screw rod 16 is rotated in the opposite direction, the screw rod 9 is lowered and the pivot 10 is lowered.

A contact surface 7c having an upwardly arched side surface is formed on the upper surface near the tip of the rocker arm 7.

A cam 21 provided on a camshaft 20 that is pivotally supported on a bearing 19 erected on the cylinder head 4 and rotates in synchronization with a crankshaft (not shown) of the internal combustion engine comes into contact with this contact surface 7c. It's becoming like that.

A protruding piece 7d is connected to one side of the abutment surface 7c, and a displacement sensor 22 is arranged above the protruding piece 7d, facing away from the upper surface of the protruding piece 7d by a slight distance D. In this manner, it is fixed to the lower surface of a support cylinder portion 19a that extends from one bearing 19 toward the cam 21 side.

The displacement sensor 22 is, for example, a known non-contact displacement meter such as a capacitance type or an electromagnetic induction type, and constantly measures the distance D to the upper surface of the protruding piece 7d.

Reference numeral 23 in FIG. 1 compares the minimum value (D ₁ ) of the distance D measured by the displacement sensor 22 with a preset setting value (D ₀ ), and calculates the difference (D _{1 )} .
-D ₀ ) is a control device that controls the advancing/retracting device 18 so that the distance (D 0 ) becomes small.

The control device 23 includes a minimum value detection circuit 24, a comparison circuit 25, a setting circuit 26, and a motor control circuit 2.
It consists of 7.

The minimum value detection circuit 24 is for detecting the minimum value of the output signal from the displacement sensor 22. For example, the minimum value detection circuit 24 inverts the maximum and minimum signal values of the output signal from the displacement sensor 22 using an inverting circuit (not shown). , the maximum value after inversion may be detected by a known sample-and-hold circuit (not shown).

The setting circuit 26 is for setting a set value (D ₀ ), and this set value (D ₀ ) is the clearance between the contact surface 7c of the rocker arm 7 and the bottom surface 21a of the cam 21 when the valve is closed. It is preferable to set an appropriate value so that C is close to 0.

The comparison circuit 25 is for comparing the minimum value (D ₁ ) of the distance D measured by the displacement sensor 22 with a fixed value (D ₀ ) selected by the selection circuit 26.

The motor control circuit 27 detects that when the minimum value (D _{1 ) is larger than the set value (D 0 ) as a result of comparing both values (D 1 )} (D ₀ ) in the comparison circuit 25 (D ₁ >D ₀ ) _.
operates the motor 15 so that the pivot 10 goes up, and when the minimum value (D ₁ ) is smaller than the set value (D ₀ ) (D ₁ <D ₀ ), the motor operates so that the pivot 10 goes down. 15.

Note that if the minimum value (D ₁ ) and the set value (D ₀ ) are substantially the same, the motor 15 is preferably stopped.

By having a configuration like this embodiment, thermal expansion of each component during operation of the internal combustion engine,
Even if the clearance C is about to change due to wear of various parts, the pivot 10 will automatically move up and down.
Clearance C is always maintained constant.

In the above embodiment, the advancing/retracting device 18 includes two screw feed mechanisms (screw hole 8 and screw rod 9, and screw hole 17 and screw rod 16), a pinion/rack mechanism (pinion 12 and rack 14), and a motor 15. However, the advancing/retracting device 18 is controlled by the control device 2.
Any configuration may be used as long as the pivot 10 can be automatically advanced or retracted according to No. 3.

The displacement sensor 22 may be mounted on the cylinder head 4, for example offset to the side of the camshaft 20.

〔Effect of the invention〕

According to the present invention, there are advantages such as electrical control without using hydraulic pressure, simple structure, and good responsiveness.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a main part of a valve mechanism of an internal combustion engine equipped with an embodiment of the present invention, and FIG.
3 is an enlarged cross-sectional plan view taken along line BB in FIG. 1. FIG. 1... Engine valve, 1a... Shaft part, 1b...
... Umbrella section, 2 ... Valve guide, 3 ... Retainer,
4... Cylinder head, 5... Valve spring, 6... Valve seat, 7... Rocker arm, 7a... Pressing surface, 7b... Recess, 7c... Contact surface, 7d... Protruding piece, 8... Screw hole, 9... Screw rod, 10... Pivot, 10a... Annular groove, 11
... Spring, 12 ... Pinion, 13 ... Hole, 1
3a...Step part, 14...Rack, 14a...Protrusion piece, 15...Motor, 16...Screw rod, 17...Screw hole, 18...Advancement/retraction device, 19...Bearing, 19a
...Support tube section, 20...Camshaft, 21...
Cam, 21a...Bottom surface, 22...Displacement sensor, 23...Control device, 24...Minimum value detection circuit, 25...Comparison circuit, 26...Setting circuit, 27
...Motor control circuit, C...Clearance, D...
…distance.

Claims (1)

[Scope of Claims] 1. A cam provided on a camshaft that rotates in synchronization with the crankshaft is in sliding contact with the upper surface of the middle part of the rocker arm whose base end is pivotally supported on the cylinder head, and the rocker arm is rotated by the rotation of the cam. A valve adjuster that adjusts the clearance between the cam and the rocker arm when the valve is closed, in an internal combustion engine valve mechanism that rotates and pushes the shaft end of the engine valve with its tip to open the valve. an advancing/retracting device for advancing and retracting a pivot supporting a base end of the rocker arm toward the cam side from the cylinder head; and a spring for biasing the rocker arm in a direction in which it is constantly pressed against the shaft end of the engine valve. , a displacement sensor supported by the cylinder head facing the upper surface of the rocker arm and constantly measuring the distance to the opposing surface of the rocker arm; a minimum value of the distance measured by the displacement sensor; and a preset setting value. A valve adjuster in a valve operating mechanism of an internal combustion engine, comprising: a control device that controls the advancing/retracting device so that the difference is small.