JPS6118012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fuel injection timing adjustment device for an internal combustion engine;
Specifically, a roller is pivotally supported on the free end of a centrifugal weight arranged in a housing on the drive side of the adjustment device, and a timer hub with a cam surface is provided on the driven side, and the roller is attached to the cam surface by a spring. The present invention relates to a fuel injection timing adjustment device that is energized by contact.

Such a fuel injection timing adjustment device (Special Publication Publication No. 45-3326
(Refer to the publication), the centrifugal force caused by the rotation of the engine rotates the centrifugal weight until this centrifugal force balances the spring force, and at this time, the tip roller of the centrifugal weight is urged against the cam surface by the action of the spring. The timer hub forming the cam surface also rotates accordingly, resulting in a phase difference between the driving side and the driven side. The injection timing is then controlled according to this phase difference.

In conventional devices of this type, the rollers provided on the centrifugal weight are attached to pins extending from the centrifugal weight via roller bushes. For this reason, the pin and roller bushing are in line contact, resulting in a large amount of friction. Therefore, the hysteresis caused by the difference in the direction of force acting between the roller and the curved road when the rotational speed increases and decreases is amplified, and the difference between increasing and decreasing rotational speed at the same rotational speed is amplified. In other words, the difference in fuel injection timing becomes so large that it cannot be ignored. Therefore, there is a problem in that it is difficult to accurately control the injection timing, and the amount of harmful components in the exhaust gas increases.

Therefore, in view of the drawbacks of the prior art, it is an object of the present invention to provide a structure capable of reducing as much as possible the friction occurring in the shaft support of the centrifugal weight roller and minimizing hysteresis.

Explaining the following with reference to the drawings, in FIGS. 1, 2, and 3, 12 is a timer hub fixed to the camshaft 10 of the fuel injection pump (not shown);
Arm portion 1 extending in diametrically opposing positions as shown in FIG.
A curved path 12a, which is a cam surface that contacts a roller 14, which will be described later, is formed on the arm portion 12'. On the other hand, the housing 16 is connected to the engine, and together with the rotating cover 180 constitutes a casing of the device. A pair of arcuate centrifugal weights 20 are supported at one end by a shaft 22 in the housing 16, and the rollers 14 are provided on the centrifugal weights at a distance from the shaft. A spring 18 is provided between the block 26 on this shaft 22 and the arm portion 12', and the roller 1
4 is urged into contact with the cam surface 12a.

According to the invention, the roller 14 is supported by the following mechanism. That is, the pin 30 has a straight portion at one end that is press-fitted into the centrifugal weight 20, and the other end 30-1 is formed into a spherical shape. A pair of annular protrusions 30-2 are formed on the spherical end 30-1. A hollow sleeve 32 is surrounded around the spherical end 30-1 and closed at one end 32-1, and the sleeve 32 has a plurality of (for example, three) holes 32-2 formed at equal intervals in the angular direction in the cylindrical portion. is forming. A small ball 36 is arranged within this hole 32-2 and contacts the spherical portion 30-1 between the annular projections 30-2. A snap spring 40 fitted to the inner surface of the sleeve 32 and the protrusion 3
A spring 42 is disposed between one side of the hollow sleeve 32-1 to urge the hollow sleeve end 32-1 into contact with the spherical part 30-1, and has a dimension l that determines the proper position of the small ball 36 and the hole 32-2. maintain. And this hollow sleeve 3
2 and the roller 14 is fitted thereto.

To explain the operation below, when the rotation of the engine is transmitted to the housing 16, the centrifugal force causes the centrifugal weight 20
rotates to open and expand around the shaft 22, and as a result, the roller 14 is displaced radially outward. By the action of the spring 18, the cam surface 12a of the timer hub 12 is urged to rotate so as to maintain contact with the roller 14. Therefore, the timer hub 1 on the driven side is
2 performs a relative rotational movement, and a phase difference occurs during this relative rotational movement.
As a result, the angular position θ (that is, the injection timing) at which the plunger of the injection pump (not shown) is driven by the camshaft 10 connected to the timer hub 12 is adjusted in accordance with the centrifugal force, that is, the engine rotation speed Np.
This is shown in FIG. In this case, since there is a difference in the direction of action between the roller 14 and the cam surface 12a depending on whether the rotational speed Np increases or decreases,
Hysteresis as shown in the figure appears in the phase angle change characteristics. However, in the present invention, the one end spherical part 30-1 of the pin 30 and the small ball 3 are separated from the conventional sliding contact.
Since the roller 14 is supported by rolling contact due to point contact with the roller 6, it is possible to keep the frictional force to an extremely low level. Therefore, the hysteresis becomes small as shown by the solid line C, and the deviation from the target value A becomes the minimum. In addition, the hysteresis characteristic in the sliding contact of the conventional technology is shown by the broken line B, but the rotation speed
It will be appreciated that at Np ₁ there is a hysteresis of Δ ₁ , which is greater than the Δ ₂ of the present invention.

Rolling contact as in the present invention is preferable in terms of durability because it reduces frictional temperature rise and wear of the contact surface. Further, even if the perpendicularity of the surface of the pin 30 with respect to the centrifugal weight is out of order due to manufacturing tolerances or assembly errors, the point contact between the ball portion 30-1 and the small ball 36 is substantially maintained, so the cam Occurrence of uneven contact due to contact between the surface 12a and the roller 14 is reliably prevented.

In the illustrated embodiment, three small balls 36 are used, but the durability can be increased by increasing the number to five or seven. In this case, compared to sliding friction, when the same material and heat treatment are used, rolling friction has a friction coefficient of 1/30, which is incomparably smaller, so the increase in frictional force due to temperature rise due to friction is not worth considering.

[Brief explanation of the drawing]

FIG. 1 is an axial sectional view taken along the line - in FIG. 2 of the apparatus of the present invention, FIG. 2 is a sectional view taken along the line - in FIG. 1, and FIG. 3 is a sectional view taken along the line - in FIG. FIG. 4 is an exploded perspective view of the components of the roller support mechanism according to the present invention, and FIG. 5 is a characteristic diagram of the rotation speed and phase angle for explaining the operation. 10...Camshaft, 12...Timer hub,
12a...Cam surface, 14...Roller, 16...Housing, 18...Spring, 20...Centrifugal weight, 30
... Pin, 30-1 ... Ball portion, 32 ... Hollow sleeve, 32-2 ... Hole, 36 ... Small ball.

Claims (1)

[Claims] 1. A fuel injection timing adjustment device for an internal combustion engine, which
A roller is pivotally supported on the free end of a centrifugal weight disposed on either the driving side or the driven side of the adjusting device, and a timer hub with a cam surface is provided on the other side, and the roller is attached to the cam surface by a spring. In a contact-biased device, the pin that pivotally supports the roller is fitted with a centrifugal weight at one end and forms a ball at the other end, a hollow sleeve is positioned around the ball, and the hollow sleeve is connected to the pin. forming a hole for accommodating a small ball that makes point contact with the ball of the
A fuel injection timing adjustment device for an internal combustion engine, characterized in that the roller is fitted around a hollow sleeve, and the outer surface of the roller is in contact with a cam surface.