JPH041332Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an improvement of a distribution type fuel injection pump.

[Conventional technology and its problems]

Distribution type fuel injection pumps are widely used as fuel injection pumps for diesel internal combustion engines. In this pump, the plunger is biased toward the cam disk by a plunger spring whose one end is supported by a distributor head and the other end is supported by a spring seat. Both rotational and reciprocating motion is applied to the plunger via the cam and lower roller to pump and distribute fuel.

In such a pump, when the cam disc is rotated at high speed to increase the pump output,
It is known that a misalignment occurs in the contact relationship between the cam surface and the roller, causing a phenomenon in which the cam surface separates from the roller. This phenomenon causes a shock load greater than the design value to be applied to the roller when the roller is seated, causing the roller to may cause damage.

As a countermeasure against this camjumping, there is a method of increasing the plunger pressing force by increasing the setting force of the plunger spring, but this has a negative effect on the timer, such as increasing the drive reaction force in the entire area, so adjusting the setting force is naturally restricted. be.

Another method, as shown in Japanese Patent Application Laid-open No. 58-88456, is to form a ring-shaped damper chamber in the end face of the plunger barrel, and to form a constriction and a large diameter piston part in the plunger itself. Some devices are designed to constitute a hydraulic damper.

However, with this structure, in addition to the normal sliding clearance between the plunger and barrel, strict concentricity on the order of microns is required in order to obtain an appropriate clearance for the damper part, and this processing is difficult, resulting in high manufacturing costs. It is expensive, and is unstable in that the desired damper performance cannot be obtained even with slight dimensional tolerances.

In addition, as another means, as shown in Japanese Patent Application Laid-Open No. 60-47866, instead of a guide pin that guides the plunger spring, a long cylinder is provided protruding from the distribution head side to the vicinity of the spring seat.
The spring seat is provided with a buffer piston inserted into the cylinder, an inlet opening is formed in the middle wall of the cylinder, and the buffer piston is provided with a check valve and a suction passage with a T-shaped cross section in the axial direction.

However, this camjumping prevention mechanism also has a complex structure, a large number of parts, and requires high precision in terms of straightness and surface roughness over a wide range, making it difficult to process and expensive to manufacture. Additionally, there is a problem that it cannot be easily applied to existing pumps. Further, in use, there is a concern that the piston and the cylinder may jam when an eccentric load is applied in the axial direction, and this is not necessarily practical.

[Means for solving problems]

This invention was devised through research to solve the above-mentioned conventional problems, and its purpose is to improve the camjump limit with an extremely simple structure, and to improve the camshaft limit of existing pumps. Another object of the present invention is to provide a distribution type fuel injection pump with a hydro damper that can be easily applied.

To achieve this purpose, the present invention utilizes the guide pin of the plunger spring as it is and forms a hydraulic damper at one end of the guide pin, that is, one end is in the distributor head and the other end is in the radial direction of the plunger. In a distribution type fuel injection pump equipped with a plunger spring that is supported by a spring seat that extends to the cam side and presses the plunger toward the cam side, a short cap that can slide relative to the tip of the guide pin is attached to the spring seat or the distributor head, and the short cap is attached to the spring seat or the distributor head. A damper chamber communicating with the pump chamber is provided between the bottom of the guide pin and the tip end surface of the guide pin.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1, 1a, and 2 show embodiments of the distribution type fuel injection pump according to the present invention.
3 is a cam disk in contact with the roller 2, 3 is a plunger fitted into the cam disk 1 through a notch, 4 is a spring seat fixed to the plunger 3, 5 is a plunger barrel, and 6 is a distributor head.

7 is a guide pin, and in the embodiments shown in FIGS. 1 and 1a, the other end 7 into which the collar 10 is press-fitted is shown.
1 is fitted into a stepped blind hole 61 formed on the inner surface of the distributor head 6, while a short cap 8 is fitted onto one end 70 on the inside side of the pump so as to be able to slide relative thereto, and the short cap 8 is fitted with a spring seat. The plunger spring 13 is fitted into a hole 41 formed in the plunger spring 4 with an appropriate play, and a flange portion 81 for supporting the plunger spring 13 is formed at the tip. Note that a projecting edge 42 is provided on the inner surface of the spring seat 4 to sandwich the outer edge of the flange portion 81, if necessary.

Next, in the embodiment shown in FIG. 2, the relationship between the short cap 8 and the collar 10 with respect to the guide pin 7 shown in FIG. One end 70 of the guide pin 7 is inserted into the short cap 8 so as to be relatively slidable, and the other end 71 of the guide pin with the collar 10 press-fitted therein is positioned on the spring seat side.

In either embodiment, the short cap 8 is
When the plunger 3 is at the bottom dead center position, the inner bottom surface 8
The guide pin 7 has a length sufficient to form a damper chamber 14 of an appropriate volume between the guide pin end face 72 and the guide pin end face 72, and an oil guide notch groove 73 of a required length is formed in the guide pin 7 in the axial direction from the end face 72. has been done.

The length of the oil guide notch 73 is matched to produce a high-speed damper effect, and the length is such that the groove end of the oil guide notch 73 slightly peeks out from the mouth end of the short cap 8 when the cam rises to the highest level. It's summery.

Although the above mechanism is shown only on one side of the plunger, it goes without saying that another set may be provided at a symmetrical position to the one shown.

[Effect of the embodiment]

Next, the operation of the present invention will be explained using the embodiment shown in FIG. 1 and FIG. The spring seat 4 also moves in the direction of contracting the plunger spring 13 (to the right with respect to the plane of the paper). At this time, the flange portion 81 of the short cap 8 is connected to the plunger spring 1.
3 and the spring seat 4, the short cap 8 moves together with the spring seat 4.

In a normal plunger spring mechanism,
This simply increases the length of the guide pin 7 protruding from the hole in the spring seat 4, but in the present invention, one end 70 of the guide pin 7 is inserted into the short cap 8 so as to be relatively slidable. With the movement of the short cap 8 corresponding to the lift of step 3, the one end 70 of the guide pin 7 increases the degree of penetration into the short cap 8.
This restricts the discharge of oil from the damper chamber 14 through the oil guide notch 73, and the oil in the damper chamber 14 flows out from the oil guide notch 73 to the pump chamber 16 while being compressed. Therefore, although the structure is simple, the plunger 3 exhibits a resistance effect against impactive lifting and lowering, and the camjumping limit is improved.

When the cam is lowered, oil in the pump chamber 16 flows through the oil guide notch 73, so that the guide pin 7 moves backward through the short cap 8 smoothly.

In addition, since the present invention uses the guide pin 7 as it is, the guiding action of the plunger spring 13 is maintained well from beginning to end.

[Effect of idea]

According to the present invention described above, a hydraulic damper is formed at one end of the guide pin of the plunger spring that presses the plunger in the distribution type fuel injection pump, so that the plunger spring has a good guiding function. At the same time, a stable damper function can be obtained and the camjumping limit can be improved, and furthermore,
The structure is extremely simple because it uses the guide pin of the plunger spring, and the number of parts is small.It is also easy to process as it only requires consideration of the clearance between the guide pin and the short cap, without requiring high-precision concentricity. It can be applied to other pumps with only a small amount of additional work or parts replacement, and excellent effects can be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a main part showing one embodiment of a distribution type fuel injection pump according to the present invention, Fig. 1a is a partially enlarged view thereof, and Fig. 2 is a partial cross-sectional view showing another embodiment of the present invention. It is a diagram. 1...cam disc, 3...plunger, 4...
...Spring seat, 6...Distributor head, 7...
... Guide pin, 8 ... Short cap, 13 ... Plunger spring, 14 ... Damper chamber, 72 ...
Guide pin tip surface, 73...Oil guide notch groove, 8
0... Inner bottom surface of the short cap.

Claims (1)

[Scope of utility model registration request] In a distribution type fuel injection pump equipped with a plunger spring that is supported at one end by a distributor head and at the other end by a spring seat extending in the radial direction of the plunger and which presses the plunger toward the cam side, a guide pin is attached to the spring seat or the distributor head. Attach a short cap that can slide relative to one end of the
A distribution type fuel injection pump characterized in that a damper chamber communicating with the pump chamber is provided between the bottom of the short cap and the end face of the guide pin.