JPH02544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection pump used in a diesel engine or the like, and particularly to a surplus fuel discharge device thereof.

FIG. 1 is a sectional view of the fuel injection pump proposed in Japanese Patent Application No. 130684/1984. A rotor 1 is rotated by a drive shaft (not shown) that rotates synchronously with the engine, and a pair of plungers 2 are accommodated in a hole passing through the left end of the rotor 1 laterally. There is. A roller shoe 8 and a roller 9 are installed outside the plunger 2, and the plunger 2, roller shoe 8, and roller 9 rotate together with the rotor 1.

The cam ring 3 on the outer periphery of the roller 9 is mounted inside the outermost housing 10. Also, rotor 1
is rotating inside a sleeve 42 attached to a sleeve holder 41 fixed to the housing 10.

The inside of the rotor 1 is a first pressurizing chamber 4 and a second pressurizing chamber 6.
A free piston 5 is interposed between them, and the right end of the second pressurizing chamber 6 is sealed with a stopper 7. Further, the second pressurizing chamber 6 communicates with a discharge passage 23 formed in the radial direction of the rotor 1, and the second radial passage 12 communicates with the second fixed passage 1 of the sleeve 42.
It is provided corresponding to 4.

On the other hand, a first radiation passage 11 communicating with the first pressurizing chamber 4 is provided corresponding to the first fixed passage 13 of the sleeve 42, and an overflow port 2 is provided in the lower part of the first pressurizing chamber 4.
9 is provided and is connected to the discharge passage 32 through overflow passages 30, 31.

The openings of the first fixed passage 13 and the second fixed passage 14 formed in the sleeve 42 are connected to the first solenoid valve 15 and the second fixed passage 14.
The first solenoid valve 15 and the second solenoid valve 16 are respectively opposed to the tips of the valve body 17 of the solenoid valve 16, and are composed of a coil 19 housed in a case 18, a fixed magnetic pole 20, and a spring 21. A fuel supply port 43 is formed in the center of the sleeve holder 41, and the fuel introduced through the port fills the accommodation chambers of the valve bodies 17 of the electromagnetic valves 15 and 16 and the rotor 1.

Note that 22 is a terminal of the coil 19, 24 is an output path, and 25 is a connection port. Also, 2
7 is a detector having an annular permanent magnet fixed to the end of the sleeve holder 41, and a pulser 26 attached to the rotor 1 is inserted inside the detector.
The pulsar 26 is a magnetic body with protrusions around its periphery, and when the pulsar 26 rotates together with the rotor 1, the magnetic path is interrupted and a rotation signal is output from the detection terminal 28. Thereby, the rotational position and speed of the rotor 1 can be detected.

The operation of the fuel injection pump configured in this way will be explained with reference to FIGS. 2 to 7. The left side of these figures corresponds to the - sectional view of FIG. 1, and shows the state of the fuel pump. Furthermore, the right-hand diagram shows the relationship of the fuel flow path between the rotating rotor 1 and the sleeve 42 that accommodates the rotor 1, and the position of the free piston 5.

FIG. 2 shows the state when the supply of injected fuel is started, and the plungers 2a and 2b are moving outward. In FIG. 2a, the inner surface of the cam ring 3 has moved from the reduced diameter part to the large diameter part, and as the first pressurizing chamber 4 is depressurized, the free piston 5 moves in the direction of the arrow and moves to the second pressurizing chamber 6. Depressurize. Therefore, the injected fuel is sucked in through the second radiation passage 12 and the second fixed passage 14.
Note that at this time, since the valve body 17b is open, pressurized fuel flows into the second pressurizing chamber 6. That is, in this case, the fuel for injection is being sucked.

FIG. 3 shows a state in which the intake of the injected fuel has been completed and the supply of the injection timing adjustment fuel has started, at which point the free piston 5 has temporarily stopped and the valve body 17a has opened. As shown in FIG. 3A, since the roller 9 rotates on the large inner diameter part of the cam ring 3, the plunger 2 further reduces the pressure in the first pressurizing chamber 4 and sends the pressure through the first fixed passage 13 and the first radial passage 11. Inhale injection timing adjustment fuel. In addition, the valve body 17a, 1
The valve 7b can also be opened at the same time to introduce fuel.

FIG. 4 shows a state in which the injection timing adjustment fuel has been supplied, the plunger 2 and the free piston 5 are stopped, and the valve bodies 17a and 17b are both closed.

FIG. 5 shows a state in which fuel injection is started; at this time, the roller 9 is guided to the reduced inner diameter portion of the cam ring 3, and the plunger 2 begins to approach. Therefore, the free piston 5 moves in the right direction of the arrow to transfer the fuel in the second pressurizing chamber 6 to the discharge passage 23 and the outlet passage 2.
4 to the connection port 25 in FIG. Since the pipe attached to the connection port 25 communicates with the cylinder, a predetermined amount of fuel is supplied to the cylinder.

FIG. 6 shows a state in which the fuel injection is finished and the discharge of surplus fuel is started. When the free piston 5 moves to the extreme right side, the overflow port 29 is exposed, so the pressurized surplus fuel is discharged into the overflow passage 30. flows out through. Note that this fuel is supplied to the sleeve holder 4 in Fig. 1.
It flows out to the low pressure part through the overflow passage 31 of No. 1. That is, FIG. 1 shows the state at this time.

FIG. 7 shows a state in which the discharge of excess fuel has been completed, and the free piston 5 is temporarily stopped, but is now transitioning to the state shown in FIG. 2 and is about to suck in the injected fuel.

What is understood from the above explanation is that rotor 1 is
A series of fuel intake and injection operations are performed during the 90° rotation. Note that since the engine in this case has four cylinders, fuel is injected into all cylinders during one revolution of the rotor 1. Further, the fuel sucked into the first pressurizing chamber 4 is fuel for adjusting the so-called injection timing, and what is actually injected is the fuel sucked into the second pressurizing chamber 6.

A conventional fuel injection pump that operates in this way is
After the fuel in the second pressurizing chamber 6 is injected, excess fuel is discharged, but since the opening area of the overflow port 29 does not increase rapidly at this time, it takes time to forcibly overstroke the free piston 5. It takes. Therefore, an excess amount of the next injection fuel to be introduced into the second pressurizing chamber 6 is drawn in, making the movement of the free piston 5 unstable.

In addition, since the amount of introduced fuel changes depending on the overflow speed of surplus fuel, it has the disadvantage that injection stability is affected by the rotation speed of the rotor 1 and the amount of fuel that determines the injection timing. was.

An object of the present invention is to provide a surplus fuel discharge device for a fuel injection pump that can eliminate the drawbacks of the prior art and obtain a stable fuel injection amount, and is characterized by being movable into a high-pressure fuel chamber. The first pressurizing chamber, which is partitioned by a free piston installed in In the surplus fuel discharging device for a fuel injection pump, the free piston is provided with a valve mechanism that opens when the free piston moves at the end of the period, and rapidly flows out fuel for injection timing control. has a flat valve having a rod-shaped portion on the second pressurizing chamber side,
The valve seat of the flat valve has an opening provided on the first pressurizing chamber side and a discharge port communicating with the overflow passage on the second pressurizing chamber 6 side, and the rod-shaped portion is airtightly fitted. It is formed by a step with a movably held valve body holding part, and at the end of the fuel injection timing, the tip of the rod-shaped part is caused to protrude and reach a stopper provided in the second pressurizing chamber. Upon contact, the valve body is separated from the valve seat, and fuel for injection timing control in the first pressurizing chamber flows out from the overflow passage.

FIG. 8 is a sectional view of a main part of a fuel injection pump according to an embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. In this case, a movable valve body 51 is housed within the free piston 50,
Since the valve body 51 and the free piston 50 are airtightly fitted, fuel does not move from the first pressurizing chamber 4 to the second pressurizing chamber 6. Also, free piston 5
The flange of the valve body 51 housed in the valve body 51 is pressed by a spring 53 secured to a ring 54 and comes into close contact with the valve seat, thereby blocking the flow of fuel.

However, when the free piston 50 moves to the right and reaches the stage where the injection ends and the surplus fuel is discharged, the valve body 51
The tip of the valve body 51 comes into contact with the tip of the stopper 7, and the collar of the valve body 51 separates from the valve seat, causing the overflow passage 30 to flow from the discharge port 52.
Surplus fuel flows to. Since the overflow port 29 and the overflow passage 30 in this case are holes with a larger diameter than those in FIG. 1, excess fuel can be rapidly flowed out through these holes.

For example, if the diameter of the seat portion that the flange of the valve body 51 is in contact with is 4 mm, the gap between the valve body 51 and the seat portion is
If it is 0.1 mm, the cross-sectional area of the flow path through which fuel flows will be 1.26 mm ² . Moreover, the fuel that has passed through this flow path is discharged through the outlet 52, which has a cross-sectional area larger than this.
And it can be easily and quickly discharged from the overflow port 29 and the overflow passage 30.

On the other hand, in the conventional free piston 5, the diameter of the overflow port 29 is 3 mm, and the free piston 5
Even if an overflow section were created by moving 0.6 mm, the area would only be 0.998 mm ² .

That is, in the case of this embodiment, excess fuel can be discharged by a slight movement of the free piston 50. Note that since the end of the injection is performed at a fixed position of the free piston 50, it is easy to select the discharge port 52 to face the overflow port 29.

The surplus fuel discharging device of this embodiment has a valve body with a flange inside, and is configured so that the valve body contacts the stopper when the free piston moves to its maximum, even when the flange is slightly away from the seat part. A relatively large amount of surplus fuel can be discharged in a short time. Therefore, the accuracy of the amount of fuel injected from the second pressurizing chamber is also improved. Furthermore, since the area where the free piston 50 receives pressure to the right is increased before and after the discharge passage 23 is opened, the vibration phenomenon when excess fuel is discharged is suppressed, and the pressure inside the high-pressure pipe up to the injection valve is rapidly reduced. Because it stabilizes, it helps prevent secondary injection, etc.
Effects such as being able to improve the stability of fuel injection can be obtained.

The surplus fuel discharge device for a fuel injection pump according to the present invention enables rapid discharge processing of surplus fuel, and has the effect of being able to obtain a stable fuel injection amount.

[Brief explanation of drawings]

Figure 1 is a sectional view of a conventional fuel injection pump, Figure 2 is a sectional view of a conventional fuel injection pump.
7 to 7 are explanatory diagrams of the operation of the fuel injection pump shown in FIG. 1, and FIG. 8 is a sectional view of a main part of the fuel injection pump which is an embodiment of the present invention. 1... Rotor, 2... Plunger, 3... Cam ring, 4... First pressurizing chamber, 5, 50... Free piston, 6... Second pressurizing chamber, 7... Stopper,
8...Roller show, 9...Roller, 10...Housing, 11...First radiation passage, 12...Second
Radiation passage, 13...first fixed passage, 14...second
Fixed passage, 15, 16... Solenoid valve, 17... Valve body, 23... Discharge passage, 24... Outlet passage, 25
... Connection port, 26 ... Pulsa, 27 ... Detector,
29... Overflow port, 30, 31... Overflow passage, 32
...Discharge passage, 41...Sleeve holder, 42...
... Sleeve, 43 ... Fuel supply port, 51 ... Valve body, 52 ... Discharge port, 53 ... Spring, 54 ... Ring.

Claims (1)

[Claims] 1. Fuel related to injection timing is supplied to the first pressurizing chamber partitioned by a free piston movably installed in the high-pressure fuel chamber, and fuel related to the injection amount is supplied to the second pressurizing chamber. Surplus fuel of a fuel injection pump, the free piston is provided with a valve mechanism that opens when the free piston moves at the end of a fuel injection period and causes fuel for injection timing control to rapidly flow out. In the discharge device, the free piston has a flat valve having a rod-shaped portion on the second pressurizing chamber side, and a valve seat of the flat valve is arranged between an opening provided on the first pressurizing chamber side and the first pressurizing chamber side. 2. The rod-shaped part has a discharge port communicating with the overflow passage on the pressurizing chamber side, and is formed by a step with a valve body holding part in which the rod-shaped part is airtightly fitted and movably held, and the fuel injection timing is At the end of the process, the tip of the rod-shaped part is projected and comes into contact with a stopper provided in the second pressurizing chamber, so that the valve body is separated from the valve seat, and the injection timing control for the first pressurizing chamber is performed. A surplus fuel discharge device for a fuel pump, characterized in that the fuel is caused to flow out from the overflow passage.