JPH0734999A - Unit injector - Google Patents

Abstract

PURPOSE:To provide stable injection characteristics by a method wherein operation of a solenoid valve part is effected only one time during a forced feed, a temporary period in which the injection of fuel in a compression chamber is suspended is provided during a period in which a fuel feed passage is throttled and pilot injection and main injection are performed. CONSTITUTION:A barrel part 3 is formed on the base part of the injection pump body 2 of an injection pump part 1 and a plunger 4 is slidably inserted thereinto. A holder part 10 is assembled to the tip of an injection pump body 2 and a nozzle part 13 is assembled thereto through a spacer 12. Further, the valve housing 22 of a solenoid valve part 21 is integrally extended to the side of the injection pump body 2. Meanwhile, a leak port 42 communicated with a fuel feed passage 23 is formed in the side of the barrel part 3 and a fuel escape passage 43 through which a compression chamber 9 and the leak port 42 are communicated with the plunger 4 is formed. A drive pulse by means of which the fuel feed passage 23 is closed is fed to a solenoid valve part 21 approximately in a period in which aforesaid communication is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unit for controlling a fuel injection to an engine by providing a solenoid valve in the middle of a fuel supply passage leading to a compression chamber of an injection pump body and controlling opening / closing of the fuel supply passage by the solenoid valve. Regarding injectors.

[0002]

2. Description of the Related Art In this type of unit injector, in order to obtain a main injection and a pilot injection prior to this main injection, a solenoid valve is used in the pressure feeding process.
A method of driving it once is being considered. In addition, Japanese Patent Laid-Open No. 1-
Japanese Patent No. 151751 discloses that, for example, a piezo element that opens and closes an injection nozzle is provided separately from a solenoid valve, a barrel port on which a plunger slides is provided with a leak port that communicates with a fuel supply passage, and this leak occurs in a predetermined cam angle range. A configuration is shown for forming a fuel relief passage in the plunger that communicates with the port.

[0003]

However, according to the type in which the solenoid valve is driven twice, the behavior between the pilot injection and the main injection becomes unstable due to the response delay of the solenoid valve and the like. For this reason, although an attempt is made to obtain good injection by pilot injection, there is a disadvantage that the injection amount fluctuates.

From this point of view, it seems that the fuel injection can be started and stopped quickly if the injection nozzle is opened and closed by an epizo element or the like to obtain the pilot injection, but the plunger has no detent. , The phase between the plunger and the injection pump body is not stable. For example, in FIG.
When the phase between the leak port 52 formed in the injection pump body 2 and the fuel escape passage 43 formed in the plunger 5 changes as in (a) and (b), the passage length from the compression chamber to the leak port is changed. And the passage resistance fluctuate, so the pilot injection amount increases and decreases. In this case, assuming that the optimum injection characteristic is obtained in the state of FIG.
If the phase shifts to (b), the fuel spill deteriorates due to an increase in passage length and passage resistance, and in the worst case, pilot injection and main injection are connected, as shown by the broken line in FIG. 3, and stable. There is a risk that the jetting characteristics that have been obtained may not be obtained.

In view of the above, it is an object of the present invention to provide a unit injector which eliminates the above-mentioned inconvenience and can obtain stable injection characteristics from pilot injection to main injection.

[0006]

SUMMARY OF THE INVENTION Therefore, the gist of the invention according to claim 1 is that a plunger is slidably inserted in a barrel portion formed in an injection pump body, and the barrel portion and the plunger are used. An injection pump unit having a compression chamber provided in the enclosed space, and having at least a high-pressure passage for guiding fuel in the compression chamber to a nozzle unit described later and a fuel supply passage for supplying the fuel introduced from the fuel inlet to the compression chamber. And a valve body provided in the middle of the fuel supply passage of the injection pump body for adjusting the communication state between the compression chamber side and the fuel inlet side of the fuel supply passage, and the movement of the valve body is supplied to the solenoid. A solenoid valve part that is controlled by a control signal from the outside, and a nozzle part that supplies fuel from the high-pressure passage to the engine, and is formed on a side surface of the barrel part. And a leak port that communicates with the supply passage,
The fuel release passage is formed in the plunger and connects the compression chamber and the leak port in a predetermined cam angle range, and the fuel is provided before and after a period in which the leak port and the fuel release passage are in communication. A drive pulse for closing the supply passage is supplied to the solenoid valve portion.

Further, the gist of the invention according to claim 2 is that a plunger is slidably inserted into a barrel portion formed in an injection pump body, and a compression chamber is provided in a space surrounded by the barrel portion and the plunger. An injection pump portion having at least a high-pressure passage for guiding the fuel in the compression chamber to a nozzle portion described later, and a fuel supply passage for supplying the fuel introduced from the fuel inlet to the compression chamber, and the injection pump main body. A control signal from the outside is provided in the middle of the fuel supply passage and has a valve body for adjusting the communication state between the compression chamber side and the fuel inlet side of the fuel supply passage, and the movement of the valve body is supplied to the solenoid. Solenoid valve part controlled by
A leak port that is formed on a side surface of the barrel portion and communicates with the fuel supply passage and a plunger that is formed of a nozzle portion that supplies fuel from the high-pressure passage to the engine, and is formed in the plunger in a predetermined cam angle range. A fuel injection passage for connecting the compression chamber and the leak port is provided, and the injection pump main body is provided with a phase fixing mechanism for fixing the phases of the plunger and the injection pump main body.

[0008]

Therefore, according to the first aspect of the invention, the fuel introduced from the fuel inlet is guided to the compression chamber through the solenoid valve portion, but from the nozzle portion while the fuel supply passage is not restricted by the solenoid valve portion. Fuel is not injected. Then, when the fuel supply passage is throttled at a time before the leak port and the fuel escape passage communicate with each other,
Since the fuel in the compression chamber is pressurized, pilot injection is started. When the plunger lifts and the fuel escape passage communicates with the leak port, the fuel in the compression chamber spills into the fuel supply passage, ending pilot injection, and then
When the plunger is further lifted and the fuel escape passage is removed from the leak port, the fuel in the compression chamber is pressurized again and main injection is started. Then, this main injection ends when the fuel supply passage is opened.

As described above, the pilot injection is performed by operating the solenoid valve portion only once before and after the period in which the leak port and the fuel escape passage communicate with each other, and mechanically spilling the fuel in the compression chamber during that period. An injection interruption region between the main injection and the main injection is formed.

According to the second aspect of the invention, since the phase of the plunger and the injection pump main body is fixed, there is no risk of the plunger rotating as it reciprocates, and the fuel flowing from the compression chamber to the fuel supply passage is prevented. The spill characteristics can be made constant at all times, and therefore the above-mentioned problems can be achieved.

[0011]

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

In FIG. 1, the unit injector is
An injection pump unit 1 for injecting and supplying fuel into each cylinder of an internal combustion engine is provided. In the injection pump unit 1, a barrel unit 3 is formed at a base of an injection pump body 2, and a plunger 4 is slid on the barrel unit 3. It is inserted freely. Injection pump body 2
A spring receiver is formed on the injection pump body 2
A spring 6 is interposed between a spring receiver of the above and a tappet 5 connected to the plunger 4, and the spring 6 constantly urges the plunger 4 in a direction away from the injection pump main body 2 (direction indicated by an arrow A in the figure). is doing.
The tappet 5 is assembled in the injection pump main body 2 by inserting a locking pin 8 protruding from a side surface into a guide groove 7 formed in the injection pump main body 2 along the axial direction of the plunger 4. It can reciprocate while maintaining a predetermined phase with the main body 2. A cam formed on a drive shaft (not shown) is in contact with the tappet 5, and the drive shaft is connected to an engine to rotate, and cooperates with the spring 6 to reciprocate the plunger 4 in the barrel portion 3. It is designed to move. By the reciprocating movement of the plunger 4, the fuel in the compression chamber 9 formed surrounded by the plunger 4 and the injection pump body 2 is compressed, and the fuel is sucked into the compression chamber 9.

At the tip of the injection pump body 2, the holder portion 1
No. 0 is assembled by screwing a holder nut 11 that engages with the holder portion 10 around the tip of the injection pump body 2, and a nozzle portion 13 is assembled to the holder portion 10 via a spacer 12. The spacer 12 and the nozzle portion 13 are attached to the retaining nut 14 that locks them.
Is fixed by screwing around the tip of the holder 10. A spring accommodating chamber 15 is formed in the holder portion 10, and the needle spring of the nozzle portion (not shown) is moved by the nozzle spring 16 accommodated in the spring accommodating chamber 15 in the tip direction of the nozzle portion (the direction of the arrow indicated by B in the figure). ). The nozzle portion 13 has a well-known structure, and when high-pressure fuel is supplied through a high-pressure passage 17 described below, the needle valve is opened against the nozzle spring 16 and the injection portion formed at the tip of the nozzle portion is opened. Fuel is injected from the hole into the engine.

The high-pressure passage 17 is formed in the injection pump body 2 and has a passage 18 whose one end opens into the compression chamber 9.
8, a passage 19 formed in the holder portion 10, a passage 20 formed in the spacer 12, and formed in the holder portion 10, and a passage (not shown) formed in the nozzle portion 13 and connected to the passage 20. Has been done.

A valve housing 22 provided with a solenoid valve portion 21 to be described later is integrally extended to the side of the injection pump body 2, and the injection pump body 2 and the valve housing 22 are provided.
Is provided with a fuel supply passage 23 for supplying fuel to the compression chamber 9. This fuel supply passage 23 is connected to a first supply passage 23a to which fuel is supplied from a fuel inlet 24 formed on the side of the injection pump main body 2, and the first supply passage 23a so that the plunger 4 is constantly slid. An annular recess 23b formed in the moving barrel portion 3, and a second supply passage 2 connected to the annular recess 23b and communicating with a valve head housing chamber 25 of the solenoid valve portion 21 described later.
3c, a third fuel supply passage 23d, one end of which is connected to the annular groove 27 formed on the peripheral surface of the valve body 26 and the other end of which is connected to the compression chamber 9.

The supply of fuel to the compression chamber 9 is regulated by the solenoid valve portion 21.
1, a valve body 26 is slidably inserted into a sliding hole 28 formed in the valve housing 22. The valve housing 30 is provided with a valve seat 30 that abuts a valve head portion 29 formed at the tip of the valve body 26, and the header 3 covers the valve head portion 29.
1 is screwed to the valve housing 22. A valve head housing chamber 25 surrounded by the header 31 and the valve housing 22 is formed at the joint between the header 31 and the valve housing 22, and is fixed to the header 31 in the valve head housing chamber 25. Stopper 3 facing the valve head 29
Two are provided.

Further, the valve body 26 has a holder 33, which is screwed on the side opposite to the header 31 of the valve housing 22, inserted therethrough, and an armature 34 is fixed to the tip thereof.
The holder 33 is assembled with a solenoid nut 36 by a holder nut 37 via a spacer 35, and the armature 34 includes the holder 33 and the spacer 3.
It is stored in the armature chamber 38 formed between the
It faces the solenoid 39 accommodated in the solenoid accommodating portion 36 through the mounting hole of the spacer 35. The holder 33 stores and holds a spring 40 for urging the valve head 29 in a direction in which the valve head 29 is always separated from the valve seat 30, and the valve head 29 is normally separated from the valve seat 30. When the armature 34 is attracted to the solenoid 39 by energizing the solenoid 39, the valve head 29 is driven in a direction in which the valve head 29 abuts the valve seat 30.

However, when the solenoid 39 is energized, the valve head 29 is seated on the valve seat 30 and the fuel supply passage 23
Is shut off, and the fuel already supplied to the compression chamber 9 is compressed during the pressure feeding stroke of the plunger 4 and supplied to the nozzle portion 13 via the high pressure passage 17. When the fuel is pumped, the solenoid 39 is de-energized, the valve head 29 moves away from the valve seat 30, a part of the high pressure fuel is returned to the valve head housing chamber 25, and the fuel pressure in the compression chamber 9 decreases. It ends by doing.

By the way, as shown in FIGS. 2A to 2C, a leak port 42 communicating with the first supply passage 23a is formed on the side surface of the barrel portion closer to the compression chamber than the annular recess 23b. Also, the plunger 4 has a compression chamber 9
A fuel escape passage 43 that communicates with is formed. The fuel escape passage 43 has an annular groove 44 formed in an annular shape on the peripheral surface of the plunger 4, a vertical hole 45 formed in the axial direction of the plunger from the tip of the plunger facing the compression chamber 9, and the vertical hole 45. 4 formed in the radial direction of the annular groove 4
4 and a lateral hole 46 communicating with 4. Then, the leak port 42 and the annular groove 4 of the fuel escape passage 43
The positional relationship with 4 is as follows.

When the plunger 4 is located at the bottom dead center, the leak port 42 is connected to the annular groove 44 of the plunger 4.
The leak port 42 is located closer to the front end, and the leak port 42 is closed by the side surface of the plunger 4, and is not in communication with the annular groove 44 (FIG. 2A). Leak port 42 from this bottom dead center
Stroke (cam angle) until is communicated with annular groove 44
Is preset to a predetermined amount by a shim interposed between the tappet 5 and the cam. Therefore, when the plunger 4 moves downward (in the direction of the arrow in FIG. 2) in the drawing, the distance between the annular groove 44 and the leak port 42 decreases, and when the plunger 4 moves a predetermined stroke, the annular groove 44 becomes the leak port 42. Communication is established (Fig. 2 (b)). Then, when the plunger 4 moves further downward and the annular groove 44 is disengaged from the leak port 42, the annular groove 44 and the leak port 42
The communication with and is cut off (Fig. 2 (c)). Assuming that the time point when the leak port 42 and the annular groove 44 communicate with each other is topen and the time point when the communication between the leak port 42 and the annular groove 44 is cut off is tcut, the diameter of the leak port 42 from the plunger position at the toopen ( D) and the time point when lifted by the width (L) of the annular groove 44 becomes tcut (see FIG. 3). Then, after tcut, the plunger 4 is further lifted, and the annular groove 44 moves away from the leak port 42 until reaching the top dead center.

Such a leak port 42 and an annular groove 44
With respect to the movement of the plunger 4 having a relationship with, the energization of the solenoid 39 is controlled by the control unit 48 shown in FIG. The control unit 48 includes an A / D converter, a multiplexer, a microcomputer, a drive circuit, and the like (not shown). The control unit 48 detects an accelerator opening degree detection unit that detects the accelerator pedal depression amount (accelerator opening degree) and an engine rotation state. Each signal of a rotation detection unit for detection, a reference pulse generation unit for generating a pulse each time the drive shaft reaches the reference angular position, etc. is input, and these signals are arithmetically processed to output the drive pulse shown in FIG.

This drive pulse allows for the delay of the response of the solenoid 39, and the annular groove 44 is provided at the beginning of the pressure feeding process.
Before the leak port 42 communicates with the leak port 42 (t ₁ ).
Supplied from The driving pulse is the plunger 4
Lifts and the annular groove 44 passes through the leak port 42,
It is designed to be released when a predetermined time has passed (t ₃ ).

The time t ₁ at which the drive pulse is applied is appropriately adjusted to obtain the optimum pilot injection amount.
In the embodiment shown in FIG. 3, the timing (t ₂ ) at which the valve element is seated on the toilet seat is set to be before topen, but while the annular groove 44 is in communication with the leak port 42, or After that, the seating timing (t ₂ ) may be shifted. Even in these cases, there is a possibility that the pilot injection can be realized with the preflow generated in the process of narrowing the fuel supply passage 23.

In the above arrangement, it is assumed that the plunger 4 is now at the bottom dead center position. From this point, the plunger 4 begins to lift, but when the drive pulse is supplied to the solenoid 39 at t ₁ , the armature 34 is attracted to the solenoid 39 by the electromagnetic force, and the valve head 29 faces the valve seat 30. The valve head 29 is seated on the valve seat 30 when the movement starts and t ₂ after a while from t ₁ . The seating state continues until t _3, since t ₃ thereafter electromagnetic force disappears, the valve head 29 at a rate determined by the spring force of the spring 40
Moves away from the valve seat 30.

Prior to topen, the fuel supply passage 23 is throttled by the solenoid valve portion 21, so the fuel in the compression chamber 9 is compressed by the plunger 4 and injected.
Pilot injection is started. When the leak port 42 and the annular groove 44 communicate with each other after topen, part of the fuel in the compression chamber is returned to the fuel supply passage 23 and the pressure in the compression chamber drops, so pilot injection ends. And tcu
After the time t, the communication between the leak port 42 and the annular groove 44 is cut off, so that the fuel leak action is lost thereafter, the same main injection as in the conventional case is obtained, and this state is maintained until t ₃ .

As described above, according to the present invention, the solenoid valve portion 21 is operated only once during the pressure feeding process, and the leak port 42 and the fuel escape passage 43 are communicated with each other during the operation period. The pilot injection and the main injection can be obtained after stabilizing the movement of 26.

The plunger 4 and the tappet 5 are connected to each other by engaging the tip end of the tappet 5 with the base end of the plunger 4. That is, the tip of the tappet 5 is formed with a U-shaped recess 51 that opens laterally and that opens to the tip through the somewhat narrowed opening narrowing 50, and the proximal end of the plunger 4 is formed. A small-diameter portion 52 having a diameter substantially equal to the width of the narrow opening portion 50 is provided, and a connecting protrusion 53 having a larger diameter is provided subsequent to the small-diameter portion 52, and the connecting protrusion 53 is formed into a U-shaped recess 51. It is configured to be slid from the side to be engaged.

The phase fixing mechanism 55 for fixing the phase between the plunger 4 and the injection pump main body 2, in other words, the phase between the lateral hole 46 and the spill port 42, is, for example, as shown in FIG. 5, the adjusting screw 56 is radially attached to the side wall of the guide rod 5, and the connecting protrusion 53 is tightened from the radial direction so that the plunger 4 is not rotated by the adjusting screw 56. As shown in FIG. It is also possible to provide the connecting protrusion 53 of No. 4 with a flat portion 57 that comes into contact with the facing wall surface of the U-shaped recess 51 so that the plunger 4 does not rotate. Further, a large number of flat portions 57 may be provided with the peripheral edge of the connecting protrusion 53 being polygonal, and the phase of the plunger 4 and the injection pump main body 2 may be adjusted and fixed to a phase in which an optimum spill state is obtained.

If such a phase lock mechanism 55 is provided,
Each time the fuel escape passage 43 communicates with the leak port 42, the lateral groove 46 and the leak port 44 do not shift in phase, so that the passage length from the compression chamber 9 to the leak port 42 and the passage resistance can always be the same. Therefore, it is possible to make the fuel leak state uniform during the operation period and to eliminate the fluctuation of the injection characteristic.

Further, according to the present invention, the leak port 4
Even if there are variations in the positions of the annular groove 44 and the annular groove 44, if the cam angle at which the annular groove 44 opens to the leak port 42 is adjusted by a shim or the like, and the drive pulse application start time is adjusted by the solenoid valve portion 21, The injection performance can be set to the optimum state for each unit injector. That is, in the conventional row type pump, VE pump, etc., if the prestroke is changed by adjusting the shim thickness, the injection characteristics will change, so it is necessary to form each member, passage, etc. within a predetermined tolerance range. However, according to the present invention, even if the displacement of the leak port or the like is adjusted by the shim, the injection start can be controlled by the solenoid valve, so the injection start and the injection amount are uniformly determined with respect to the cam angle. can do. Therefore, according to the unit injector of the present application, there is no problem even if the shim thickness is greatly changed in order to obtain a desired injection characteristic, and there is no problem even if there are variations in the formation position of the leak port or the like as the shim thickness needs to be increased. Absent.

[0031]

As described above, according to the first aspect of the present invention, the operation of the solenoid valve portion is performed only once during the pressure feeding process, and the fuel in the compression chamber is mechanically operated during the period when the fuel supply passage is throttled. The pilot injection and the main injection are formed by temporarily spilling the fuel to interrupt the injection, so that the solenoid valve does not need to be operated to interrupt the injection and is stable in each cycle. It is possible to obtain the injection characteristic.

Further, since the pilot injection amount can be changed by the start timing of energization of the solenoid valve portion and the main injection amount can be changed by the end timing of energization of the solenoid valve portion, the engine operating condition and the deviation between cylinders can be changed. It is possible to provide the optimum injection according to.
Further, if the energization start timing is set after the communication timing between the leak port and the fuel escape passage, pilot injection can be eliminated.

Further, as in the conventional case, when the solenoid valve portion is actuated twice during the pressure feeding process, a solenoid valve portion having a high responsiveness is provided in order to stabilize the behavior of the portion where the pilot injection and the main injection are interrupted. I needed it,
In the present invention, since the valve body does not move in the process of shifting from the pilot injection to the main injection, the responsiveness of the solenoid valve portion itself does not pose a problem, and an inexpensive and small solenoid valve portion can be used. .

As another effect, even if the formation position of the leak port differs for each unit injector, if the cam angle at which the leak port and the fuel escape passage communicate with each other is adjusted by a shim or the like, injection start or injection The amount can be set to a desired time and amount only by adjusting the application timing to the solenoid valve portion. For this reason, there is also an advantage that strict management is not required to form the leak port, the fuel escape passage, and the like.

According to the second aspect of the present invention, since the phase of the plunger and the injection pump body can be fixed and the fuel spill characteristic from the compression chamber to the fuel supply passage can be kept constant, the plunger rotates. As a result, there is no time-dependent shift in the injection characteristics, and stable injection characteristics can be obtained for each cycle.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration diagram of a unit injector according to the present invention.

2 (a) to 2 (c) are enlarged cross-sectional views of a main part in FIG. 1, showing a process of lifting a plunger.

FIG. 3 is a diagram showing characteristics of a plunger lift, a plunger speed, a drive pulse, a valve lift, and an injection rate of the unit injector shown in FIG.

FIG. 4 is a diagram showing an example of a cross section taken along the line CC in FIG.

5 is a diagram showing another example of a cross section taken along the line CC of FIG.

6 (a) and 6 (b) are explanatory views showing phase changes between a leak port formed in the injection pump body and a fuel escape passage formed in the plunger.

[Explanation of symbols]

 1 Injection Pump Section 2 Injection Pump Main Body 3 Barrel Section 4 Plunger 9 Compression Chamber 13 Nozzle Section 17 High Pressure Passage 21 Solenoid Valve Section 23 Fuel Supply Passage 26 Valve Body 39 Solenoid 42 Leak Port 43 Fuel Relief Passage 55 Phase Fixing Means

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naotake Oi 3-13-26, Yasumi-cho, Higashimatsuyama, Saitama Prefecture Zexel Higashimatsuyama Factory

Claims (2)

[Claims] 1. A plunger is slidably inserted into a barrel portion formed in an injection pump body, a compression chamber is provided in a space surrounded by the barrel portion and the plunger, and a fuel in the compression chamber is provided with a nozzle portion described later. An injection pump portion having at least a high-pressure passage for leading to the compression chamber and a fuel supply passage for supplying the fuel introduced from the fuel inlet to the compression chamber; and a fuel supply passage provided in the fuel supply passage of the injection pump body. Has a valve body that adjusts the communication state between the compression chamber side and the fuel inlet side of the solenoid valve section that controls the movement of this valve body by a control signal from the outside supplied to the solenoid, and from the high pressure passage. A nozzle for supplying fuel to an engine, a leak port formed on a side surface of the barrel and communicating with the fuel supply passage, and a plunger formed on the plunger. A drive pulse that includes a fuel escape passage that connects the compression chamber and the leak port in a constant cam angle range, and that closes the fuel supply passage before and after a period in which the leak port and the fuel escape passage communicate with each other. Is supplied to the solenoid valve section. 2. A plunger is slidably inserted into a barrel portion formed in an injection pump body, a compression chamber is provided in a space surrounded by the barrel portion and the plunger, and a fuel in the compression chamber is described later with a nozzle portion. An injection pump portion having at least a high-pressure passage for leading to the compression chamber and a fuel supply passage for supplying the fuel introduced from the fuel inlet to the compression chamber; and a fuel supply passage provided in the fuel supply passage of the injection pump body. Has a valve body that adjusts the communication state between the compression chamber side and the fuel inlet side of the solenoid valve section that controls the movement of this valve body by a control signal from the outside supplied to the solenoid, and from the high pressure passage. A nozzle for supplying fuel to the engine, a leak port formed on a side surface of the barrel and communicating with the fuel supply passage; and a leak port formed on the plunger. A fuel release passage that connects the compression chamber and the leak port in a constant cam angle range, and a phase fixing mechanism that fixes the phase of the plunger and the injection pump body to the injection pump body. A unit injector to be used.