JP2817119B2 - Distribution type fuel injection pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a distribution type fuel injection pump, and more particularly to an improvement in a cam disk used in the distribution type fuel injection pump.

[Prior Art] Generally, a distribution type fuel injection pump includes a cam disk and a plunger provided integrally with the cam disk, and the cam disk has a cam portion formed on one end surface of a roller holder. The roller is brought into pressure contact with the roller. Therefore, when the cam disc is forcibly rotated, the cam disc reciprocates, whereby the plunger reciprocates. When the plunger moves forward, the fuel in the fuel pressurizing chamber is pressurized, and when the plunger moves backward, the fuel is sucked into the fuel pressurizing chamber from the suction port.

The pressurized fuel is injected from the fuel injection nozzle into the combustion chamber of the engine, and the fuel injection amount is adjusted according to the position of the control sleeve fitted on the outer periphery of the plunger.

By the way, in the distribution type fuel injection pump, it is known that the fuel injection amount changes with a change in the rotation speed of the engine (plunger). This change corresponds to the rotation of the plunger. Therefore, by previously measuring the change characteristic of the injection amount with respect to the rotational speed, it is possible to control the fuel injection amount based on the measured value.

[Problems to be Solved by the Invention] However, in the conventional fuel injection pump, when the rotational speed of the engine reaches a certain high-speed rotational speed, the fuel injection amount does not correspond to the rotational speed, and the fuel injection amount is controlled. It becomes impossible. Therefore, there is a problem that the engine cannot be rotated at a high speed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is possible to make the fuel injection amount correspond to the engine speed up to a higher rotation speed range, and therefore, the distribution type fuel capable of rotating the engine at high speed. It is an object to provide an injection pump.

Means for Solving the Problems In order to solve the above problems, the inventor of the present application has pursued a cause where the injection amount and the rotation speed do not correspond in a high-speed rotation range. It was found that there was an improper match between the open area and the plunger retraction speed.

That is, in the conventional distribution type fuel injection pump, when the plunger starts to move backward, the inlet port of the plunger is opened by the inlet slit of the plunger facing the suction port, and the plunger enters the fuel pressurized chamber through the inlet slit from the inlet port. Fuel is introduced. Here, as shown in FIG. 1, the open area of the suction port gradually increases with the rotation (cam angle) of the plunger, and gradually decreases after reaching the maximum. On the other hand, the return speed of the plunger is maximized when the open area of the suction port is equal to or less than half of the maximum open area.

Here, the amount of fuel to be introduced into the fuel pressurization chamber is
It is proportional to the reciprocating speed of the plunger, and when the reciprocating speed of the plunger is maximized, the filling amount to be introduced into the fuel pressurizing chamber is maximized. Therefore, when the reciprocating speed of the plunger is maximized, it is necessary to maximize the amount of fuel that can be introduced from the suction port into the fuel pressurized chamber.

However, in the conventional fuel injection pump, when the reciprocating speed of the plunger is maximized, the opening area of the suction port is less than half the maximum area. For this reason, if the engine rotates faster than a certain speed,
The amount of fuel introduced from the suction port to the fuel pressurizing chamber is less than the required filling amount. As a result, during high-speed rotation, the fuel injection amount drastically decreased, and the rotation speed and the fuel injection amount did not correspond.

The present invention has been made based on the above findings, and a cam disk that reciprocates by being driven to rotate while a cam portion formed on one end surface is in contact with a roller of a roller holder. A plunger provided on the other end surface of the cam disk and reciprocating integrally with the cam disk, for pressurizing the fuel in the fuel pressurizing chamber by the forward movement of the plunger. In a distribution type fuel injection pump configured to introduce fuel into the pressure chamber, and to increase the opening area of the suction port with the rotation of the plunger and then reduce the opening area, the opening area of the suction port is reduced. A cam portion of the cam disk is formed such that the reciprocating speed of the plunger is maximized when the plunger is substantially maximized.

[Operation] When the plunger moves backward at the maximum speed, the open area of the suction port is almost maximized. Therefore, the amount of fuel that can be introduced into the fuel pressurized chamber from the suction port during the maximum movement of the plunger is as follows. , Compared with the conventional fuel injection pump. Therefore, the correspondence between the fuel injection amount and the rotation speed is maintained up to a higher speed range.

[Embodiment] FIGS. 1 to 5 show an embodiment of the present invention.
This will be described with reference to the drawings.

FIG. 4 shows the overall configuration of a distribution type fuel injection pump according to the present invention. The distribution type fuel injection pump shown in FIG. 4 has the same configuration as that of the conventional type except the cam portion 3a of the cam disk 3. is there. Therefore, a brief description will first be made of an overall configuration similar to the conventional one. A cam disk 3 is disposed in a pump chamber 2 inside a pump housing 1. The cam disk 3 is connected to a drive shaft 4 which is driven to rotate by an engine (not shown) so as to be relatively movable and integrally rotate, and a cam portion 4a formed on one end surface thereof is provided with a roller. Holder 5
The roller 5a is pressed and contacted by a plunger spring 6. The cam portion 3a has a number (four in this embodiment) of cam lobes 31 (see FIG. 5) corresponding to the number of cylinders of the engine. Therefore, when the drive shaft 3 rotates, the cam disk 3 rotates and reciprocates following the rotation.

The base end of the plunger 7 is integrally provided on the other end surface of the cam disk 3. The plunger 7 rotates and reciprocates together with the cam disk 3, and at the time of forward movement (movement to the right in FIG. 4), an inlet slit 7a, which will be described later, separates from the suction port 9 and is sucked by its outer peripheral surface. When the opening of the port 9 is shielded, the fuel pressurizing chamber 8 is closed.
Substantially pressurizing the fuel therein. The pressurized fuel is
7b, horizontal hole 7c, outlet slit 7d, discharge port 10,
The fuel is fed to a fuel injection nozzle (not shown) through a discharge passage 11 and a delivery valve 12, and is injected into a combustion chamber of an engine.

It is needless to say that the same number of discharge ports 10, discharge passages 11, and delivery valves 12 are provided as the number of cylinders of the engine.

The plunger 7 moves further and its cut-off port
When 7e is exposed from the control sleeve 13, the pressurized fuel flows out to the pump chamber 2 through the vertical hole 7b and the cutoff port 7e. Thereby, the substantial fuel pressurization ends, and the fuel injection ends. Therefore, the fuel injection amount increases when the control sleeve 13 is displaced in the forward movement direction of the plunger 7, and decreases when the control sleeve 13 is displaced in the forward movement direction.

The position of the control sleeve 13 is operated by a governor 14 and a control lever 15 via a governor lever assembly 16.

On the other hand, when the plunger 7 moves backward (moves to the left in FIG. 2), the fuel in the pump chamber 2 is sucked into the fuel pressurizing chamber 8 via the suction passage 17 and the suction port 9. That is, the same number of inlet slits 7a as the number of cylinders of the engine are formed on the outer peripheral surface of the distal end portion of the plunger 7 at equal intervals in the circumferential direction. And plunger 7
At the time of the backward movement, any of the inlet slits 7a is opposed to the suction port 9, so that the suction port 9 is opened. As a result, the fuel in the pump chamber 2 is sucked and introduced into the fuel pressurizing chamber 8 through the suction passage 17, the suction port 9, and the inlet slit 7a with the return movement of the plunger.

The open area of the suction port 9 gradually increases and becomes maximum with the rotation of the plunger 7, and then gradually decreases (see FIG. 1).

A timer 18 is provided at the lower end of the pump housing 1 and operates by the pressure in the pump chamber 2. The timer 18 causes the roller holder 5 to rotate in the forward and reverse directions according to the pressure in the pump chamber 2. The fuel injection timing is adjusted accordingly.

Next, the cam portion 3a of the cam disk 3, which is a feature of the present invention, will be described. As shown in FIG.
In this embodiment, four cam ridges 31 are formed on 3a. The cam ridge 31 has a lift portion 34 having an ascending gradient from the front end 32 to the top 33 in the rotation direction of the cam disk 3 (the direction of the arrow in FIG. 5A), and descends from the top 33 to the rear end 35. The cam disk 3 and the plunger 7 move forward when the lift unit 34 rides on the roller 5a with the rotation of the cam disk 3, and the descending unit 36 descends on the roller 5a. When descending, the cam disk 3 and the plunger 7 move back.

Here, the reciprocating speed of the plunger 7 is maximized when the open area of the suction port 9 is maximized, as shown in FIG. In other words, the descending portion 36 is formed so that the reciprocating speed of the plunger 7 is maximized when the open area of the suction port 9 is maximized.

In the distribution type fuel injection pump having the above configuration, the open area of the suction pump 9 is maximized when the plunger 7 moves back at the maximum speed. The amount of introduction that can be introduced can be increased. Therefore, the correspondence between the fuel injection amount and the rotation speed can be maintained up to the high-speed rotation range as compared with the conventional fuel injection pump. Therefore, if the distribution type fuel injection pump of the present invention is used, the engine can be rotated at a higher speed.

Next, the results of an experiment performed to confirm the above-described effects of the present invention will be described. In the experiment, the distribution speed characteristics of the distribution type fuel injection pump according to the present invention (hereinafter referred to as the invention) and the conventional distribution type fuel injection pump are shown in FIG. Except for this, the configuration was the same.

2 and 3 show the relationship between the pump speed (= engine speed / 2) and the fuel injection amount at each effective lift of the plunger. FIG. 2 shows the relationship in the invention. FIG. 3 shows the relationship in a conventional product. As is apparent from FIG. 3, in the conventional product, when the speed exceeds approximately 2250 rpm, the correspondence between the rotational speed and the fuel injection amount is uncertain. On the other hand, in the invention, 2500
The correspondence was maintained up to rpm, and the correspondence could be maintained up to the high-speed rotation range as compared with the conventional product.

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the gist thereof.

For example, in the above embodiment, the return speed is maximized immediately after the open area of the suction port 9 is maximized, but the return speed may be maximized immediately before the open area starts to decrease, Alternatively, if it is slight, the reversing speed may be maximized at a time outside the range where the open area of the suction port is maximized. However, it is desirable to maximize the return speed immediately before or immediately after the open area is maximized. This is because the width of the cam ridge 31 (the cam angle required for the cam disk 3 to rotate from the front end 32 to the rear end 35) can be reduced by doing so.

Further, in the above embodiment, the return speed is increased at a constant rate until it reaches the maximum, but the increase rate is reduced at the beginning of the return, and gradually increases as the maximum return speed is approached. You may make it increase.

[Effects of the Invention] As described above, according to the distribution type fuel injection pump of the present invention, the cam portion is configured to maximize the reciprocating speed of the plunger when the open area of the suction port is substantially maximized. Is formed, the correspondence between the rotational speed and the fuel injection amount can be maintained up to a higher rotation speed range, whereby the effect that the engine can be rotated at a higher speed can be obtained.

[Brief description of the drawings]

FIG. 1 shows the relationship between the lift speed of the plunger and the open area of the suction port with respect to the cam angle, and FIG. 2 shows the correspondence between the pump speed and the fuel injection amount in the distribution type fuel injection pump according to the present invention. FIG. 3 is a view similar to FIG. 2 of a conventional distribution type fuel injection pump, FIG. 4 is a sectional view showing an embodiment of the present invention, and FIG. Fig. 5A is a front view thereof, and Fig. 5B is a side view thereof. Reference numeral 3: cam disk, 3a: cam portion, 5: roller holder, 5a: roller, 7: plunger, 7a: inlet slit, 8: fuel pressurizing chamber, 9: suction port, 31
…… Cam Mountain, 36 …… Descent.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisashi Nakamura 3-13-26 Yayumicho, Higashimatsuyama-shi, Saitama Prefecture Inside of Xexel Higashimatsuyama Plant (56) References JP-A-62-288364 (JP, A) JP-A-62-288364 Sho-62-55455 (JP, A) Actually open Sho-63-196473 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 41/12 360 F02M 41/12 350 F02M 41/14 350 F02M 59/10

Claims (1)

(57) [Claims] A cam disk formed on one end surface of the cam disk, the cam disk being rotatably reciprocated by being driven to rotate in a state of contact with a roller of a roller holder; and a cam disk provided on the other end surface of the cam disk. And a plunger that rotates and reciprocates integrally, and pressurizes the fuel in the fuel pressurization chamber by the forward movement of the plunger.
A dispensing-type fuel injection pump configured to introduce fuel from a suction port into a fuel pressurization chamber, and to increase an opening area of the suction port with the rotation of the plunger, and then reduce the maximum area; A dispensing type fuel injection pump, wherein the cam portion of the cam disk is formed such that the reciprocating speed of the plunger is maximized when the open area of the port is substantially maximized.