JPH0352989Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a mechanical timer that is attached to a fuel injection pump of an internal combustion engine and that appropriately corrects the fuel injection time depending on the engine speed.

[Prior art]

The noise level of a vehicle equipped with an internal combustion engine is usually higher when the internal combustion engine is accelerating than when the engine is in a steady rotation state.

For this reason, the current noise reduction measures to reduce the noise level of vehicles are taking various measures to reduce the noise during acceleration, and the mechanisms attached to these noise reduction measures are used to reduce the noise level of vehicles. There were problems in that the weight increased and maintainability deteriorated.

By the way, as a fuel injection pump timer,
A system that operates an eccentric cam using the centrifugal force generated by the rotation of the internal combustion engine to change the rotational phase of the rotating body connected to the internal combustion engine and the shaft connected to the fuel injection pump. is well known.

As this type of timer, for example,
As described in Japanese Patent No. 121435, a second disc cam 12 is supported by a pin 13 fixed to a case 1 that is rotated by an internal combustion engine, and a second disc cam 12 is supported by a pin 13 fixed to a case 1 that is rotated by an internal combustion engine. A first disc cam 8 provided is supported, and this first disc cam 8 is accommodated in a circular hole 7 of a cam support plate rotatably fitted into the case 1. Further, a weight 19 is supported by a first pin 9 set on the first disc cam 8.

When the case 1 rotates as the internal combustion engine rotates, the coil spring 19 compresses the space between the two weights 10 due to centrifugal force.
The second pin 13 and the first pin 9 move in the outer radial direction against the elastic force of the second pin 13 and the first pin 9.
This rotation is transmitted to the output shaft 3 fixed to the case 1 and the cam support plate 6, slightly rotating the camshaft 21 of the fuel injection pump, and the rotation of the camshaft 21 causes the fuel injection pump to rotate. is configured to advance as the rotational speed of the internal combustion engine increases, or to retard as the rotational speed of the internal combustion engine decreases.

The timer described in this publication solves the problem of general advance timers that the angle is not advanced at low temperatures, and uses two weights 10,
An actuating body 22 made of a shape memory alloy is interposed between the opposing portions of two coil springs 19 that are disposed opposite each other with a stopper 20 interposed between the coil springs 10 and 10. In the following case, the internal combustion engine is expanded in a low temperature state before being warmed up.

By expanding the actuating body 22 at this low temperature, the two weights 10, 10 are spaced apart, and the camshaft 21 of the fuel injection pump is advanced in the same way as when the case 1 rotates.

In this way, the conventional mechanical timer is configured such that the advance angle is automatically determined based on the rotational speed, and furthermore, the advance angle is advanced by an operating body made of a shape memory alloy especially at low temperatures.

Therefore, since the advance angle of the timer depends on the shape change of the shape memory alloy, the advance angle characteristics are maintained in a steady state at temperatures other than the temperature at which the shape memory alloy changes shape, and the advance angle response is maintained in a steady state. Even if I try to put it in a delayed state, I can't do it.

[Purpose of invention]

The present invention has been devised in view of the above-mentioned conventional situation and to eliminate the drawbacks thereof, and by providing an advance angle response delay mechanism in the advance angle timer, it is possible to reduce the noise level during acceleration of the internal combustion engine. The purpose of this invention is to provide an advance angle timer for an internal combustion engine that can be used in an internal combustion engine.

[Structure of the idea]

The advance angle timer for an internal combustion engine according to the present invention that achieves the above purpose includes a flyweight that is housed inside a timer case and is lifted by centrifugal force according to the engine speed, and when the amount of lift of this flyweight exceeds a predetermined value. The device is characterized by being equipped with an advance angle response delay mechanism that causes the piston in contact with the timer case to discharge the hydraulic oil in the cylinder chamber into the hydraulic oil in the timer case via a small-diameter damping valve. It is.

〔Example〕

Hereinafter, the drawings showing the present invention as an embodiment will be explained.

(Basic structure) As shown in FIG. 1, a cam support plate 21 is rotatably housed in the timer case 20, and a disc cam 23 is rotatably housed in a hole 22 provided in the cam support plate 21. Further, a disc cam 25 is rotatably housed in a hole 24 provided eccentrically in the disc cam 23. A pin 26 is set up on the cam support plate 21, and this pin 26 is inserted into a hole in the disc cam 25.

Further, a pin 27 is installed in the disc cam 23, and the pin 27 supports the center portion of the flyweight 28. Note that the disc cams 23, 25
The pins 26 and 27 are provided symmetrically, and the two flyweights 28 are symmetrically supported within the timer case 20 by the two pins 27. These two flyweights 28 are provided with recesses 30 on the left and right sides, and a shaft 31 is inserted into the recesses 30.
is passed through the shaft 31, and a spring 32 whose one end is supported by the shaft 31 is housed.

The cam support plate 21 is fixed to the output shaft 35,
This output shaft 35 is connected to a camshaft of a fuel injection pump (not shown).

In the mechanical timer configured in this way, when the timer case 20 rotates with the rotation of the internal combustion engine, the flyweights 28 disposed on both sides of the output shaft 35 are lifted in the direction of arrow C by centrifugal force, and the flyweights 28 are lifted in the direction of arrow C by the centrifugal force. Move the pin 27 supporting the weight 28 in the direction of arrow D, and
rotates the disk cam 23 to which is fixed.

Disk cams 23 and 25 are doubly fitted into the pin 26 set on the cam support plate 21.
3 is fitted into the hole 22 provided in the cam support plate 21, a relative positional change occurs between the pin 26 and the pin 27 as the flyweight 28 lifts due to the centrifugal force. By changing the positions of the pins 26 and 27, the cam support plate 21, which is rotatably supported inside the timer case 20, is slightly rotated.

Since the cam support plate 21 and the output shaft 35 are fixed, the output shaft 35 slightly rotates with respect to the timer case 20 as the fly weight 28 lifts, and the fuel injection pump connected to the output shaft 35 rotates slightly with respect to the timer case 20. It is configured to advance the angle by rotating the camshaft.

Incidentally, since the above configuration is the same as that of a conventional mechanical timer, side views and the like have been omitted from the description.

(Characteristic Structure) Next, the characteristic structure of the present invention will be explained.

The flyweight 28 described above includes a cylinder chamber 36 that is open on the outer diameter side, and a cylinder chamber 36 that is open on the outer diameter side.
It is slidably inserted into the top of the timer case 2.
The piston 37 contacts the inner wall 20a of the cylinder chamber 3, and the cylinder chamber 3 is provided on the inner diameter side of the flyweight 28.
An advance response delay mechanism 40 is provided which includes a damping valve 38 formed in a small diameter oil passage that communicates the bottom of the timing valve 6 with the inside of the timer case 20. A damping valve 38 opened at the bottom of the cylinder chamber 36 allows the hydraulic oil in the cylinder chamber 38 to communicate with the hydraulic oil filled in the timer case 20. The length L of the piston 37 is approximately equal to the length S of the piston 37, and the piston 37 is connected to the cylinder chamber 3.
When the cylinder chamber 36 is completely immersed in the cylinder chamber 36, all of the hydraulic oil in the cylinder chamber 36 is discharged.

(Operation) In the advance angle timer configured in this way,
The piston 37 remains in the position shown in the figure until the internal combustion engine reaches a predetermined rotation speed. When the internal combustion engine reaches a predetermined rotation speed, both flyweights 28 and 28 begin to be lifted in the direction of arrow C, as shown by the dotted line. Since the top of the piston 27 comes into contact with the inner wall 20a of the timer case 20, the flyweight 28
cannot be lifted unless the hydraulic oil in the cylinder 36 is discharged from the small-diameter damping valve 38, and the hydraulic oil in the cylinder 36 passes through the small-diameter damping valve 38 and reaches the timer case 20.
The response of the advance angle operation will be delayed by the time required for the fuel to be discharged.

As the hydraulic oil in the cylinder 36 is discharged, the flyweight 28 is lifted in the direction of arrow C while the top of the piston 37 remains in contact with the inner wall 20a.
The output shaft 35 is advanced through the pin 27, the disc cam 25, and the cam support plate 21 that support the cam.

In other words, as shown in FIG. 2, the lead angle timer in the normal state operates with the lead angle characteristics shown by the solid line, but the lead angle timer with the lead angle response delay mechanism 40 operates with the lead angle characteristics shown by the dotted line. Therefore, it is possible to obtain the advance angle delay P at the same rotation speed in comparison of the two.

Therefore, the noise level of the internal combustion engine is prevented from increasing as the ignition timing advances by the advance angle delay P by the advance angle response delay mechanism 40,
Noise can be reduced.

[Effect of idea]

In short, the advance timer for an internal combustion engine according to the present invention includes a flyweight that is housed inside a timer case and is lifted by centrifugal force according to the engine speed, and when the amount of lift of this flyweight exceeds a predetermined value. This delay in advance response is caused by the provision of an advance angle response delay mechanism in which a piston in contact with the timer case discharges the hydraulic oil in the cylinder chamber into the hydraulic oil in the timer case via a small-diameter damping valve. The mechanism can slow down the response characteristics of the advance angle operation by the flyweight, which is lifted by centrifugal force according to the engine speed, and the ignition timing is advanced by the advance angle delay caused by this advance angle response delay mechanism. It is possible to reduce the noise of the internal combustion engine, which tends to increase as the engine speed increases.

Therefore, it is possible to simply provide an advance angle response delay mechanism to the advance angle timer without increasing the weight of the vehicle or deteriorating maintainability due to a mechanism added for noise reduction measures as in the past. With this structure, noise can be reduced.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention,
FIG. 1 is a partially cutaway front view of the advance angle timer, and FIG. 2 is a graph of advance angle characteristics showing a comparison between a timer with an advance response delay mechanism and a normal timer. 20...Timer case, 28...Fly weight, 36...Cylinder, 37...Piston, 3
8...damping valve, 40...advanced angle response delay mechanism.

Claims (1)

[Scope of utility model registration request] A flyweight that is housed inside the timer case and is lifted by centrifugal force according to the engine speed,
When the lift amount of this flyweight exceeds a predetermined value, the piston that comes into contact with the timer case causes the hydraulic oil in the cylinder chamber to be discharged into the hydraulic oil in the timer case via a small-diameter damping valve.There is a delay in the advance angle response. An advance angle timer for an internal combustion engine, characterized by comprising a mechanism.