JPH0429851B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that automatically adjusts fuel injection timing according to the rotational speed of an engine.

As a typical example of this type of fuel injection timing adjustment device (referred to as an automatic timer), the rotation of a drive flange connected to the engine is transmitted to a pair of timing weights, and when these timing weights are displaced by centrifugal force, this displacement is transmitted to the driven flange of the timing hub via a large eccentric cam and a small eccentric cam, and the timing hub is angularly displaced relative to the drive flange, thereby advancing the drive shaft of the fuel injection pump. There is a known system in which the fuel injection timing is relatively advanced or retarded by rotating the fuel injection timing.

In a device using a timing weight that is displaced in the radial direction by centrifugal force, a pair of support rods are passed between the pair of timing weights, and the movement of the timing weight is guided by these support rods. A spring is attached to the support rod to generate an urging force for returning the timing weight. However, in such a configuration, the centrifugal force of the timing weight is small especially in the low speed rotation region, the tension of the spring that presses the timing weight is also small, and in addition, the engine torque fluctuation is unstable, so the timing The weights tend to wobble, and the postures of both timing weights tend to tilt from their normal positions. When the timing weights are tilted, the tension of the spring changes, making it difficult for the left and right timing weights to operate equally.

For this reason, for example, the timer shown in FIG.
Np-θ characteristic diagram (Np is rotation speed, θ is timer advance angle)
In this case, the required characteristics such as A in the low speed rotation range of Np ₁ or less will have dispersion characteristics such as B, and the engine performance may not be fully demonstrated in terms of output, fuel consumption, and emission measures. There are problems such as poor restartability after stopping the engine.

For this reason, in order to ensure equal operation of both timing weights mentioned above, we
A fuel injection timing adjustment device described in "Publication No. 38626" is known. That is, this thing allows both ends of each of the support rods mentioned above to be slidably connected to the inner surface of the case,
This maintains the correct posture of the support rod and prevents the timing weight from wobbling.

However, the fuel injection timing adjustment device described in the above-mentioned publication has a disadvantage in that the both ends of the support rod are in sliding contact with the inner surface of the case, and this sliding contact tends to cause wear on both ends. For this reason, during long-term operation, as wear progresses, a large gap will occur between the inner surface of the case and both ends of the support rod, and the support rod will move in the axial direction again, causing the timing weight to wobble. Therefore, there was a problem with its durability.

The present invention was made based on the above circumstances, and its purpose is to provide a fuel for internal combustion engines that can ensure equal operation of both timing weights over a long period of time and that does not cause variations in the timer characteristics. An object of the present invention is to provide an injection timing adjustment device.

That is, the present invention is characterized in that a support member is rotatably fitted onto the outer surface of the timing hub, and the central portions of the support rods are fixed to this support member.

An embodiment of the present invention will be described below based on FIGS. 2 and 4.

In the figure, reference numeral 1 denotes a drive flange, which is connected to a crankshaft (not shown) on the engine side via, for example, an Oldham coupling 2, and is rotated by receiving torque from a pawl 1a.

A cylindrical case 3 integrally having a closing wall 4 at the other end is attached to the drive flange 1. This case 3 is fixed to the drive flange 1 with bolts 5, 5, and is integrally connected to the drive flange 1. is rotated to

A timing hub 6 is concentric with the case 3 and is attached to be rotatable relative to the drive flange 1 and the case 3.
A drive shaft 7 forming a camshaft of a fuel injection pump (not shown) is connected to the timing hub 6 by a nut 8 so as to rotate together therewith. Further, a driven flange 9 is integrally formed on the timing hub 6 so as to be located inside the closing wall 4 of the case 3. The driven flange 9 and the driving flange 1 are spaced apart from each other in the axial direction and are opposed to each other.
A space 10 is formed between them.

Circular holes 11a and 11b are formed in the driven flange 9 at positions facing each other in the radial direction,
Disc-shaped large eccentric cams 12a, 12b are rotatably fitted into these circular holes 11a, 11b.
The large eccentric cams 12a, 12b are provided with circular holes 13a, 13b at eccentric positions, respectively, and the small eccentric cams 14a, 14 are formed in these circular holes 13a, 13b.
b is rotatably inserted. Small eccentric cam 14
A, 14b has a second eccentric pin 15 at an eccentric position.
a, 15b are fitted and attached, and these second eccentric pins 15a, 15b are attached to the case 3.
It is press-fitted into the closing wall 4 of. Further, the large eccentric cams 12a, 12b have first eccentric pins 16a, 1.
6b are fitted, and these eccentric pins 16a,
16b is press-fitted and connected to timing weights 17a and 17b.

In the space 10, timing weights 17a and 17b, which are divided into two in the radial direction, are provided surrounding the timing hub 6. Since the timing weights 17a and 17b are displaced outward based on centrifugal force, they are spread apart. Support rods 18, 18 are passed through between the timing weights 17a, 17b.
It guides the radial movement of b and supports the return springs 19. Return spring 1
9... is a spring receiving seat 20... provided at the end of each support rod 18, 18, and a timing weight 17a,
17b, timing weight 1
7a and 17b are pressed and biased toward each other. In this case, the return springs 19 are composed of a high-speed spring 19a with a large tension and a low-speed spring 19b with a small tension. A sliding spring receiving plate 25 that slides along is interposed. In the low speed rotation range of the engine, the low speed spring 19b is mainly pushed, and in the high speed rotation range, the low speed spring 19b bottoms out, so the high speed spring 19a is pushed.

The first eccentric pins 16a, 16b are press-fitted into timing weights 17a, 17b, and are adapted to transmit the movement of the timing weights 17a, 17b to the large eccentric cams 12a, 12b.

As shown in FIG. 2, a thrust receiving plate 21 is provided between the inner surface of the drive flange 1 and the timing weights 17a, 17b. The thrust receiving plate 21 is fitted into a stepped portion 22 formed on the timing hub 6.
It is rotated integrally with the timing hub 6 and positioned so as not to move toward the timing weights 17a and 17b. And thrust receiving plate 21 and timing weight 17a, 1
A gap 1 of about 0.05 mm is secured between 7b.

Further, another thrust receiving plate 23 is provided between the closing wall 4 of the case 3 and the driven flange 9. This thrust receiving plate 23 is also fitted into a stepped portion 24 formed on the timing hub 6, and a minute gap S is secured between the closing wall 4 and the driven flange 6 to prevent them from coming into contact with each other. .

Such thrust receiving plates 21 and 23 keep the axial dimension L of the space 10 constant.

The timing hug 6 is provided with a support member 30. This support member 30
is a cylindrical portion 30a and a pair of plate portions 30b, 30
This cylindrical portion 30a is rotatably fitted to the outer surface of the timing hub 6. Further, the plate portions 30b, 30b integrally protrude from the outer surface of the cylindrical portion 30a, extend in the radial direction opposite to each other, and are positioned between the timing weights 17a, 17b, respectively. The support rods 18, 18 are connected to the plate portions 30b, 30b of the support member 30. That is, these support rods 1
8 and 18 extend through the plate portions 30b and 30b, respectively, at equal distances from the center of rotation of the timing hub 6, and the central portion thereof is integrally fixed to the plate portions 30b and 30b by welding or brazing. This is what has been done.

The operation of the embodiment based on such a configuration will be explained.

When the rotation of the engine is transmitted to the drive flange 1 via the Oldham coupling 2, the case 3
And the closing wall 4 is rotated together with the drive flange 1. The closing wall 4 has second eccentric pins 15a and 15b.
Since the small eccentric cams 14a, 14b and the large eccentric cams 12a, 12b are rotated around the drive shaft 7 via the driven flange 9, the timing hub 6 is rotated via the driven flange 9. Therefore, the rotation on the engine side is transmitted to the drive shaft 7 to drive the fuel injection pump.

The rotation of the drive flange 1, case 3 and timing hub 6 is controlled by timing weights 17a and 17b.
Rotate.

When the rotational speed of the drive flange side is increased, the rotational speed of the timing weights 17a and 17b is also increased, so that the timing weight 17 resists the return springs 19 due to the centrifugal force.
a and 17b are expanded and displaced. The outward movement of the timing weights 17a, 17b pushes the first eccentric pins 16a, 16b in the direction of arrow D in FIG.
1b in the direction of arrow E. Large eccentric cam 1
The rotation of 2a, 12b in the direction of arrow E causes the small eccentric cams 14a, 14b to integrally move in the direction of arrow E. At this time, since the small eccentric cams 14a, 14b are connected to the closing wall 4 by the first eccentric pins 15a, 15b, the small eccentric cams 14a, 14b are connected to the arrow E
It attempts to rotate in the direction of arrow F while revolving in the direction of arrow F. Therefore, the large eccentric cams 12a, 12b and the small eccentric cams 14a, 14b have a phase difference with each other,
This phase difference is absorbed by advancing the driven flange 9. The driven flange 9 advances the drive shaft 7 via the timing hub 6.

As a result, the injection timing θ of the fuel injection pump can be advanced with respect to the engine speed Np.

Basically, the timer characteristics as described above can be obtained, but for example, the first eccentric pins 15a and 15b shown in FIG. 3 are connected to the large eccentric cam 12.
If the first eccentric pins 16a, 16b are set in advance in the direction of arrow F with respect to the line connecting the center point of pins a, 12b and the center line of timing bubble 6, the first eccentric pins 16a, 16b can be moved in the direction of arrow D. If the second eccentric pin 1
5a and 15b are rotated in the opposite direction to the direction of arrow F. That is, the timing hub 6 is rotated to the retard side. With such a setting, the fuel injection timing can be relatively advanced in advance at the time of starting the engine and at low rotation speeds to increase the fuel combustion efficiency, thereby improving exhaust gas countermeasures.

According to such a setting, in the timer characteristic diagram shown in Fig. 1, the fuel injection timing θ is set to the advanced side when the engine starts and at low engine speeds, and when the engine speed is from Np ₁ to Np ₂ or more. Characteristic A can be realized in which the angle is returned to the retard side once and then advanced when the rotation speed reaches Np ₂ or more.

In this embodiment, the support member 30 is rotatably fitted to the timing hub 6, and the center portions of the support rods 18, 18 are fixed to the support member 30.
8 is the axial direction, that is, the timing weight 17
It does not shift or tilt as it moves in the direction of expansion of the openings a and 17b, and is always maintained in the correct posture. Therefore, in the timing weights 17a and 17b, the support rod 1
8, 18, and can reliably prevent rattling, the tension of the return springs 19b can be maintained evenly. Therefore, the biasing force of the return spring 19b can be correctly transmitted to the timing weights 17a, 17b, and the movement of these timing weights 17a, 17b can be maintained evenly, thereby preventing the so-called locking phenomenon of the timing weights 17a, 17b. Thus, required characteristic A in FIG. 1 can be satisfied. As a result, it is possible to reliably improve the engine output and fuel efficiency based on the above-mentioned required characteristic A, and it is also excellent in terms of exhaust gas countermeasures.

Furthermore, since both ends of the support rods 18, 18 are not in sliding contact with the inner surface of the case 3 to maintain their posture, they are not adversely affected by wear or the like. Therefore, even during long-term operation, the postures of the support rods 18, 18 can be maintained correctly and the above-mentioned required characteristic A can be satisfied for a long time, and the product is also excellent in terms of durability.

Note that the present invention is not limited to the above embodiments. For example, when implementing the present invention, the present invention is not limited to a timer having a timer characteristic of once retarding and then advancing as shown in characteristic A in FIG. 1, but can be applied to timers having various patterns of timer characteristics.
Further, it goes without saying that the specific mounting structure for the eccentric cam etc. is not limited to that of the above embodiment, and can be implemented with various modifications.

〔Effect of the invention〕

As described in detail above, according to the present invention, the support member is rotatably fitted to the timing hub, and the center portion of each support rod is fixed to the support member, so that the support rods are fixed in the axial direction. Movement is definitely prevented. Therefore, the movement of each timing weight is constrained by the support rod and becomes uniform, thereby preventing variations in timer characteristics and satisfying the required characteristics with high precision.

Furthermore, since the attitude maintenance of the support rod is not affected by adverse effects such as wear, the above-mentioned required characteristics can be maintained over a long period of time, resulting in excellent durability.

[Brief explanation of drawings]

Figure 1 shows the Np-θ characteristics of the timer, Figure 2 shows the Np-θ characteristics of the timer.
The figures to FIG. 4 show one embodiment of the present invention;
3 is a cross-sectional view taken along the line - in FIG. 3, FIG. 3 is a cross-sectional view taken along the line - in FIG. 2, and FIG. 4 is a perspective view of the support member. 1... Drive flange, 6... Timing hub,
7... Drive shaft, 9... Followed flange, 12a, 1
2b...Large eccentric cam, 14a, 14b...Small eccentric cam, 16a, 16b...First eccentric pin, 15
a, 15b...second eccentric pin, 17a, 17b
...Timing weight, 18, 18... Support rod, 19... Return spring, 19a... High speed return spring, 19b... Low speed return spring, 21... Thrust receiving plate, 30...
...Support member, 30a...Cylindrical part, 3b, 3b
...Plate section.

Claims (1)

[Claims] 1 The rotation of a drive flange driven by an engine is transmitted to a pair of timing weights, and these timing weights are guided by a pair of support rods spanned between these timing weights by centrifugal force, and are attached to these support rods. The timing weights are expanded in the radial direction against the urging force of the spring, and the expansion displacement of these timing weights is transmitted to the large eccentric cam via the first eccentric pin, and the large eccentric cam is eccentrically rotated. The rotation of the small eccentric cam is transmitted to the supported small eccentric cam, and the rotation of the small eccentric cam is transmitted to the timing hub connected to the drive shaft of the fuel injection pump by a second eccentric pin, and the drive flange and timing hub are rotated according to the rotation speed. In the fuel injection timing adjustment device for relatively angular displacement of the timing hub, a rotatable support member is fitted to the outer surface of the timing hub, and a center portion of each of the support rods is fixed to the support member. Engine fuel injection timing adjustment device.