JPH0467024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distribution type fuel injection pump without a discharge valve.

[Conventional technology]

A cross section of a conventional pump of this type is shown in FIG. In the figure, 01 is the pump body, 02 is the drive shaft, and 4
In the case of a cycle engine, the coaxial 02 is 1/1 of the engine rotation speed.
It rotates at a rotation speed of 2. 03 is a fuel cam, which has the same cam lobes as the number of engine cylinders, and a cam roller 04.
is in contact with. The cam roller 04 is fixed to the pump body and rotated around the drive shaft by a timer (not shown). 05 is a plunger, which is rotated and reciprocated within a plunger barrel 06 by a fuel cam 03. One revolution involves the same number of reciprocating movements as the number of cylinders. 07 is a plunger chamber, a space surrounded by the upper surface of plunger 05 and plunger barrel 06, 09 is a suction port, and plunger barrel 0
6, 010 is a discharge port, which is provided in the plunger barrel 06, 011 is a suction slit, which is provided in the plunger 05, 012 is a distribution slit, which is provided in the plunger 05,
013 is a passage in the plunger, 014 is an oil drain port, which is provided in the plunger 05, and 015 is a control sleeve, which is slidably mounted on the outside of the plunger 05 and maintains high pressure oil tightness. A governor link (not shown) moves the plunger axially. 016 is a fuel oil passage provided in the pump body 01, 017 is a damping valve, 018 is a damping valve holder, 019 is a pump chamber, and 020 is a solenoid valve for a fuel cut.

The actions described below occur after the priming is completed, and the priming itself, which is the issue of the present invention, will be described later. Due to the rotation of the drive shaft 02, the fuel cam 03 and the plunger 05
Suppose that it rotates and first comes to a position where the suction slit 011 and the suction port 09 communicate with each other. In this case, fuel passes through the suction passage 08 and enters the plunger chamber 07 through the suction port 09 and suction slit 011. Further, the drive shaft 02 rotates, and the communication between the suction port 09 and the suction slit 011 is cut off, and the inflow of fuel stops. At this time, the distribution slit 012 and the discharge port 0
10, and the oil drain port 014 is closed by a control sleeve 15. Furthermore, the rotation of the fuel cam 03 causes the plunger 05 to lift, and the fuel is compressed and sent under pressure to the damping valve holder 018 through the fuel oil passage 016. When the plunger 05 further lifts, the oil drain port 014 opens and the pressure of the fuel begins to drop. When the plunger 05 lifts further and the opening area of the oil drain port becomes sufficiently large, fuel discharge ends. Note that the positional relationship of the discharge action described above is when the prestroke is 0 mm, but
The same is basically true when prestroke is set.

[Problem that the invention seeks to solve]

The above-mentioned injection pump without a discharge valve has the advantage that the injection pressure is improved because the additional volume is reduced by removing the discharge valve and creating a simple passage, but it has the following disadvantages.

The porting diagram in Figure 5 (a diagram showing the opening timing, opening period, and opening area of each port) shows that the discharge port and oil drain port, and the discharge port and suction port overlap, and there is no discharge valve. , because it does not function as a check valve, the fuel pumped into the fuel oil passage and fuel injection pipe (not shown) by the lift of the plunger is transferred from the discharge port through the oil drain port during the overlap period. Pump chamber b It escapes from the discharge port to the pump chamber through the suction port, making priming impossible. As a result, it becomes impossible to start the engine, but in reality, troublesome work such as removing the fuel injection pipe is required, which is very disadvantageous in terms of handling of the engine.

[Means for solving problems]

The object of the present invention is to eliminate the above-mentioned drawbacks and provide a distribution type fuel injection pump without a discharge valve that can automatically achieve priming. In addition to eliminating overlapping in the opening period of the suction port and the discharge port, the shape of the fuel cam is such that the cam lift S is S = 0 and its differential coefficient near the end of the suction port closing and the beginning of the discharge port opening. dS/dθ (θ is cam angle) is dS/dθ=0
After a predetermined period of time, the cam lift S becomes S=
A control sleeve moving device is provided that provides a predetermined period during which the differential coefficient dS/dθ=0 during full lift, and moves the control sleeve to a position that closes the oil drain port only during priming.

[Effect]

In this case, (1) eliminate the overlapping period between the suction port and the discharge port; in this case, in order to prevent the plunger chamber from being compressed when the lift rises, it is necessary to (provide a sufficient period in which the cam lift S is S=0 and its differential coefficient dS/dθ is dS/dθ=0)
To prevent cavities from forming in the high pressure system and plunger chamber when the lift is lowered, the
Cam lift S near the beginning of opening of the suction port
is S = full lift, and its differential coefficient dS/dθ is dS/dθ
= 0 to prevent the oil from coming off the suction port, and (2) to move the control sleeve to completely close the oil drain port only during priming. Can prevent it from coming off.

〔Example〕

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

Fig. 1 is a sectional view showing a fuel injection pump according to an embodiment of the present invention, Fig. 2 is a porting diagram showing the opening period of each port, and Fig. 3 shows a mechanism for fully closing the oil drain port during priming. It is an explanatory diagram.

The basic structure of the fuel injection pump is the same as that of the above embodiment.

In the figure, codes 1 to 20 are 01 to 2 of the conventional example.
Indicates the same as 0.

However, the profile of the fuel cam 3 is formed as follows. There is no overlap period between the suction port 9 and the discharge port 10. That is, near the end of the suction port closing and the beginning of the discharge port opening, the cam lift S is S=0, and its differential coefficient dS/dθ is dS/
A sufficient period of dθ=0 is provided. Near the end of closing of the discharge port and the beginning of opening of the suction port, there is a sufficient period in which the cam lift S is full lift and its differential coefficient dS/dθ is 0.

Reference numeral 21 is a solenoid valve for moving the control sleeve, which presses the collector lever 22 of the governor only during priming, so that the control sleeve 15 completely closes the oil drain port 14 (the oil drain port does not open even when the plunger is at its maximum lift). move. After priming is completed (for example, the lift of the needle valve of the fuel injection valve is detected and the completion of priming is determined based on this), the collector lever 2 immediately returns to its original position.
Avoid contact with 2. That is, the control sleeve is returned to its normal position. 23 is a start lever, 24 is a start spring, and 25 is a governor sleeve.

The operation in the case of the above configuration will be described.

The present invention aims to enable priming of a fuel injection pump, and since the operation after priming is similar to that of the conventional system, priming will be described here.

The rotation of the drive shaft 2 rotates the fuel cam 3 and the plunger 5, and when the suction slit 11 and the suction port 9 are brought into communication with each other, the fuel flows into the suction passage 8.
, and enters the plunger chamber 7 through the suction port 9 and suction slit 11. Furthermore, the drive shaft 2 rotates, and the communication between the suction port 9 and the suction slit 11 is cut off, and the inflow of fuel stops. At this time, the distribution slit 12 and the discharge port 10 come into communication, and the oil drain port 14 are in a closed position with the control sleeve 15. moreover,
The plunger 5 is lifted by the rotation of the fuel cam 3, and the fuel is compressed and sent under pressure to the damping valve holder 18 through the fuel oil passage 16. Furthermore, if the plunger 5 lifts, the oil drain port 1
4 is opened, whereas during the current priming, the collector lever 22 is pressed by the operation of the control sleeve moving solenoid valve 21, and the control sleeve 15 is moved to the oil drain port 14.
Close. Moreover, since the plunger remains closed even at maximum lift, it is possible to prevent the pumped fuel from leaking into the oil supply system through the oil drain port. In addition, as the plunger lifts, in the conventional model, the suction port 9 opens while the discharge port 10 is open, but in the present case, there is no overlap between the suction port and the discharge port, so the pressure is not fed. This prevents the fuel from leaking into the oil supply system through the intake port 9. After that, the plunger descends, and even when the lift is 0, in the conventional case there is an overlap between the suction port and the discharge port, but in the present case there is no overlap, so leakage to the oil supply system can be prevented.

To summarize the above, (1) to eliminate the overlapping period between the suction port and the discharge port, and (2) to move the control sleeve so that the oil drain port is completely closed by operating the solenoid valve only during priming. , the fuel pumped into the fuel oil passage 16 and the fuel injection pipe (not shown) by the plunger 5 is prevented from leaking into the fuel supply system. As a result, after repeating the fuel pumping action described above for several cycles, the fuel passage leading to the oil reservoir (not shown) of the fuel valve is filled with compressed fuel, and the opening pressure of the fuel valve is increased. Once the pressure reaches this level, injection will begin.

By changing the profile of the cam, compression of the plunger chamber when the lift is raised and generation of cavities in the high pressure system and the plunger chamber when the lift is lowered can be prevented.

〔Effect of the invention〕

The above case has the following effects.

Priming is accomplished automatically in a distributor fuel injection pump that does not have a discharge valve.

The cam profile shown in the present invention is even more effective when equipped with a timer.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a fuel injection pump according to an embodiment of the present invention, Fig. 2 is a porting diagram showing the opening period of each port, and Fig. 3 shows a mechanism for fully closing the oil drain port during priming. Explanatory drawing, Fig. 4 is a sectional view showing a conventional distribution type fuel injection pump, Fig. 5 is a sectional view showing a conventional distribution type fuel injection pump.
The figure is a porting diagram of a conventional distribution type fuel injection pump. 3... Fuel cam, 5... Plunger, 7... Plunger chamber, 9... Suction port, 10... Discharge port, 14... Oil drain port, 15... Control sleeve.

Claims (1)

[Claims] 1. In a distribution type fuel injection pump that does not have a discharge valve, in addition to eliminating overlapping in the opening period of the suction port and discharge port, the shape of the fuel cam is such that the shape of the fuel cam is similar to that near the end of closing of the suction port and the beginning of opening of the discharge port. , a predetermined period is set in which the cam lift S is S=0 and its differential coefficient dS/dθ (θ is the cam angle) is dS/dθ=0, and the cam lift S becomes S near the end of closing the discharge port and the beginning of opening of the suction port. = A predetermined period in which the differential coefficient dS/dθ is 0 at full lift is provided, and a control sleeve moving device is provided that moves the control sleeve to a position where the oil drain port is closed only during priming. fuel injection pump.