JPH0567784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a unit type fuel injection device used in a diesel engine or the like.

[Conventional technology]

As a conventional fuel injection device of this kind, the one described in, for example, Japanese Patent Application Laid-open No. 194073/1983 is known.

This fuel injection device injects fuel pressurized by a fuel pressurizing section into a combustion chamber of an engine from the fuel injection section, and also uses a solenoid valve section to control when the fuel pressurizing section finishes pressurizing the fuel. The fuel pressurizing section has a fuel pressurizing chamber and a plunger that pressurizes the fuel in the fuel pressurizing chamber during forward movement and sucks and introduces fuel into the fuel pressurizing chamber during backward movement. We are prepared. The electromagnetic valve part communicates with the fuel pressurizing chamber via a valve seat, and is arranged with a fuel reservoir chamber to which fuel is supplied from the fuel supply means, and with one end protruding into the fuel reservoir chamber. A valve body formed with a valve portion that seats on a seat, an armature provided at the other end of this valve body, an armature chamber that accommodates this armature so as to be movable in a moving direction of the valve body, and a valve body. A spring (moving means) that urges the valve body to lift from the valve seat, and an electromagnetic solenoid (moving means) that moves the valve body against the urging force of the spring by magnetically attracting the armature. A stopper portion is provided in the fuel reservoir chamber, and the stopper portion is abutted against one end surface of the valve body to thereby regulate the maximum lift amount of the valve body.

In the fuel injection device configured as described above, the electromagnetic solenoid is demagnetized when the plunger moves backward, and the valve body is lifted from the valve seat by the biasing force of the spring. Therefore, the fuel supplied to the fuel reservoir chamber is introduced into the fuel pressurization chamber.

When the plunger begins to move forward, the electromagnetic solenoid is energized and the valve body seats on the valve seat. Thereby, the fuel reservoir chamber and the fuel pressurizing chamber are cut off. Therefore, the fuel in the fuel pressurizing chamber is pressurized, and the pressurized fuel is injected from the fuel injection section. In the latter half of the plunger's forward movement, the electromagnetic solenoid is demagnetized and the valve body lifts from the valve seat. Then, the fuel in the fuel pressurizing chamber flows back into the fuel reservoir chamber, and the pressure in the fuel pressurizing chamber decreases. This completes fuel injection.

By the way, when the high-pressure fuel in the fuel pressurizing chamber flows into the fuel reservoir chamber when the valve body is lifted, a part of the fuel gets between the valve body and the stopper part, and the valve body is pushed against the biasing force of the spring. Try to move it to the valve seat side. If the valve body were to move toward the valve seat (hereinafter referred to as reverse movement) during its lift movement, the valve opening area would become narrower and the amount of fuel flowing from the fuel pressurization chamber to the fuel reservoir chamber would decrease. As a result, there is a delay in the pressure reduction in the fuel pressurizing chamber, resulting in a problem of worsening fuel injection failure.

Therefore, in the above fuel injection device, a communication hole is formed in the valve body, one end of which opens at one end surface of the valve body that abuts against the stopper portion, and the other end opens at the outer peripheral surface of the other end facing the armature chamber. There is. When such a communication hole is formed, fuel that has flowed into the fuel reservoir chamber from the fuel pressurizing chamber flows into the armature chamber through the communication hole and presses the other end of the valve body in a direction to lift it from the valve seat. This pressing force cancels out the pressing force acting on one end of the valve body in the seating movement direction. Therefore, it is possible to prevent the valve body from moving backwards.

[Problem to be solved by the invention]

However, in the above-mentioned conventional fuel injection device in which the communication hole is formed, the movement of the armature is obstructed by the fuel filling the armature chamber, which in turn impedes the seating movement and lifting movement of the valve body. . Therefore, the response speed of the valve body to the excitation and demagnetization of the electromagnetic solenoid decreases, resulting in a problem that it becomes difficult to obtain a high injection rate.

Therefore, the inventor of this application conducted intensive research to develop a unit type fuel injection device that does not introduce fuel into the armature chamber. However, if the fuel is not introduced into the armature chamber, as mentioned above, the fuel that enters between the valve body and the stopper section causes the valve body to move backwards, which worsens the problem of fuel injection failure. It will happen.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a unit type fuel injection device that can simultaneously improve the response speed of the valve body and prevent reverse movement.

[Means to achieve the purpose]

In order to achieve the above-mentioned object, the present invention isolates the armature chamber from the fuel circulation system, and has one end of the stopper portion open to the surface against which the valve body abuts.
The other end forms a spill hole that is open to atmospheric pressure, and the size of the opening of this spill hole is such that when the valve body abuts against the stopper part, the opening of the spill hole is shielded by the valve body. The size of the valve body is set smaller than the size of the valve body at the end face that abuts against the stopper portion.

[Effect]

At the beginning of the forward movement (pressurizing movement) of the plunger, the moving means moves the valve body to sit on the valve seat. At this time, the armature chamber is isolated from the fuel circulation system and no fuel is introduced into the armature chamber, so the movement of the armature is not inhibited by the fuel. Therefore, the response speed of the valve body can be improved.

When the valve body is seated on the valve seat, the fuel pressurizing chamber is isolated from the fuel reservoir chamber, and the plunger starts substantially pressurizing the fuel. The pressurized fuel is injected from the fuel injection section.

In the latter half of the forward movement (pressure movement) of the plunger, the moving means lifts the valve body from the valve seat. The response speed during this lift movement is also improved in the same manner as above. When the valve body lifts, fuel in the fuel pressurizing chamber flows back into the fuel reservoir chamber. As a result, the pressure in the fuel pressurizing chamber decreases, and fuel injection ends. At this time, a part of the fuel that has flowed into the fuel reservoir chamber enters between the valve body and the stopper part, but the fuel is released to atmospheric pressure through the spill hole. Therefore, the valve body is hardly pressed in the seating movement direction. Therefore, it is possible to prevent the valve body from moving backward.

When the plunger moves back, the valve body is maintained in abutment against the stopper portion by the moving means.
In this state, the opening of the spill hole in the stopper portion is blocked by the valve body. Therefore, the fuel introduced into the fuel reservoir chamber is sucked and introduced into the fuel pressurizing chamber without flowing out from the spill hole.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the attached FIGS. 1 to 3.

In the figure, reference numeral 1 denotes a device main body, and this device main body 1 includes a main body portion 2 . This main body part 2
is a vertical portion 2a extending in the vertical direction in FIG.
and a side portion 2b that protrudes laterally from an intermediate portion of the vertical portion 2a. The vertical part 2a is provided with a fuel pressurizing part 3 for pressurizing fuel, and injects the fuel pressurized by the fuel pressurizing part 3 into a combustion chamber (none of which is shown) of the engine. A fuel injection section 4 is provided for this purpose.
On the other hand, the side portion 2b is provided with an electromagnetic valve portion 5 for controlling the fuel injection start timing and injection end timing.

First, to explain the fuel pressurizing part 3, the vertical part 2a has a large diameter cylinder hole 31 extending downward from the upper end surface thereof, and a large diameter cylinder hole 31 extending downward from the upper end surface of the vertical part 2a.
A small-diameter cylinder hole 32 extending downward from the bottom surface of the cylinder 1 with its axis aligned with the large-diameter cylinder hole 31 and a fuel pressurizing chamber 33 into which fuel is introduced are successively connected.

A follower member 34 is slidably provided in the large diameter cylinder hole 31 . This follower member 34 is biased upward by a plunger spring 35 provided between its upper portion and the upper end surface of the vertical portion 2a, and is pressed into contact with a cam portion of a camshaft (not shown). . It is designed to move up and down following the rotation of the camshaft. Note that the following member 34
A regulating member 36 that passes through the elongated hole 21 formed in the upper part of the vertical portion 2a is fixed to the vertical portion 2a.When the regulating member 36 hits the side surface located above the elongated hole 21, the following member 34 is The range of upward movement is restricted.

On the other hand, a plunger 3 is provided in the small diameter cylinder hole 32.
7 is slidably provided. This plunger 37 is for pressurizing the fuel in the fuel pressurizing chamber 33 during downward movement (forward movement) and sucking and introducing fuel into the fuel pressurizing chamber 33 during upward movement (backward movement). The upper end portion is attached to the lower end portion of the follower member 34 so as not to be movable in the vertical direction, so that the follower member 34 moves up and down integrally with the follower member 34 . In addition, a central portion of the small diameter cylinder hole 32 is provided to prevent the fuel in the fuel pressurizing chamber 33 from leaking to the outside of the device through the space between the inner circumferential surface of the small diameter cylinder hole 32 and the outer circumferential surface of the plunger 37. Leak stopper groove 32a for
is formed.

Next, the fuel injection part 4 will be described. A holding cylinder 41 is screwed into the lower end of the vertical part 2a with its axis aligned with the axis of the small diameter cylinder hole 32. A spring holder 42, a spacer 43, and an injection nozzle 44 are inserted into the holding cylinder 41 in this order from the vertical portion 2a side downward. These spring holder 42, spacer 43, and injection nozzle 44 are fixed to the vertical portion 2a together with the holding cylinder 41 by tightening the holding cylinder 41.

In the above configuration, when the fuel in the fuel pressurizing part 33 is pressurized by the plunger 37, the pressurized fuel is transferred to the passage 2 formed in the vertical part 2a.
2, as well as into the injection nozzle 44 through a passage 45 formed over the spring holder 42, the spacer 43 and the injection nozzle 44. Then, the needle valve 44a of the injection nozzle 44 is lifted against the biasing force of the nozzle spring 46 provided in the spring holder 42, and injection is made from the injection hole (not shown) formed at the tip of the injection nozzle 44. be done.

Next, to explain the solenoid valve part 5, the side part 2
b is formed with a through hole 51 that penetrates from its upper end surface to its lower end surface. The through hole 51 includes a small diameter hole 51a, a medium diameter hole 51b, and a large diameter hole 51c located sequentially from the upper end side to the lower end side.
An annular groove 51e is formed in the center of the small diameter hole 51a, and a medium diameter hole 51b is formed in the lower end.
Tapered hole-shaped valve seat 51 whose diameter gradually increases toward the side
d is formed.

A valve body 52 is slidably provided in the small diameter hole 51a. A valve head 52a is formed at the lower end of the valve body 52 and projects into the medium diameter hole 51b. A valve seat 5 is provided at the upper end of this valve head 52a.
A valve portion 52b is formed to be seated at 1d. An annular recess 52c is formed in the intermediate portion of the valve body 52 that continues above the valve portion 52b. A fuel supply return chamber 53 is formed by the annular recess 52c and the inner peripheral surface of the small diameter hole 51a. This fuel supply return chamber 53 is connected to a passage 2 formed in the main body 2.
3, the fuel pressurizing chamber 33 is communicated with the fuel pressurizing chamber 33.

Note that the fuel supply return chamber 53 is the fuel pressurizing chamber 33
Since the annular recess 52c is in communication with the annular recess 52c, the internal pressure is high, but the pressing forces against the upper and lower sides of the annular recess 52c cancel each other out.
Therefore, the valve body 52 is not moved in the axial direction by the pressure within the fuel supply return chamber 53.

Further, the upper end portion of the valve body 52 projects upward from the small diameter hole portion 51a, and a male threaded portion (not shown) is formed therein. A nut 54 is screwed into this male threaded portion, and an armature 55 is fixed to the upper end portion of the valve body 52 by this nut 54. A solenoid case 56 is provided on the upper end surface of the side portion 2b so as to surround the armature 55. This solenoid case 5
6 and the upper end surface of the side portion 2b form an armature chamber 56a. This armature chamber 5
An armature 55 is housed in 6a so as to be movable in the vertical direction. Further, on the lower end surface of the solenoid case 56 facing the armature 55, there is an electromagnetic solenoid (moving means) that magnetically attracts the armature 55 when energized and thereby seats the valve body 52.
57 are provided. On the other hand, electromagnetic solenoid 5
7, the valve body 52 is moved to the valve seat 51d.
In order to open the valve by lifting it from the nut 54
A valve spring (moving means) 58 that biases the valve body 52 downward is provided between the solenoid case 56 and the solenoid case 56 .

Note that the timing for energizing the electromagnetic solenoid 57 and the timing for stopping it are controlled by a control unit (not shown) such as a microcomputer based on operating conditions such as engine rotation speed and load.

Further, a lid 59 is inserted and fixed into the large diameter hole 51c. The lid body 59 and the valve body 52 define a fuel reservoir chamber 60 within the medium diameter hole 51b. This fuel reservoir chamber 60 is communicated with the fuel supply return chamber 53 via the valve seat 51d, and is also connected to the fuel pump 8 via the passage 24 and the joint 7, and is connected to the fuel pump 8 from the fuel tank 9.
Low-pressure fuel of around Kg/cm ² is now supplied.

Further, a stopper member (stopper portion) 61 is screwed and fixed to the center of the upper surface of the lid 59 via a spacer 62. This stopper part 61 is
This is for regulating the maximum lift amount of the valve body 52, and the valve body 52 is designed to abut against the center of the upper surface.

Here, as is clear from FIG. 1, the armature chamber 56a is cut off from the fuel circulation system such as the fuel pressurizing chamber 33, the fuel supply return chamber 53, and the fuel reservoir chamber 60. No fuel is introduced into the tank. Therefore, the valve body 5
2, no pressing force in the direction of lift movement by the fuel acts. Therefore, it is necessary to prevent the valve body 52 from moving backwards, and for this purpose, a spill hole 63 is formed in the stopper member 61 in this fuel injection device. One end of the spill hole 63 opens at the center of the upper surface of the stopper member 61 against which the valve element 52 abuts, and the diameter of this opening is smaller than the diameter of the lower end surface of the valve element 52. Therefore, when the valve body 52 hits the stopper member 61, the opening of the spill hole 63 is blocked by the valve body 52, thereby blocking the fuel reservoir chamber 60 and the spill hole 63. It's becoming like that. Further, the other end of the spill hole 63 passes through the stopper member 61 and the lid 59, opens at the lower surface of the lid 59, and is connected to the fuel tank 9.

Note that the reference mark 25 in the figure is a leak passage. This leak passage 25 is formed to return fuel leaked from the fuel pressurizing chamber 33, fuel reservoir chamber 53, and fuel injection nozzle 44 to the fuel tank 9, and one end is connected to the inner circumferential surface of the spring holder 42. The other end opens to the side surface of the side portion 2b via the leak stopper groove 32a and the annular groove 32a. The other end opening is connected to the fuel tank 9.

In the fuel injection device having the above configuration, when the control unit determines that it is time to inject fuel when the plunger 37 moves forward, the electromagnetic solenoid 57 is energized and the valve body 52 is moved to its seat. At this time, since fuel is not introduced into the armature chamber 56a, the movement of the armature 55 is not inhibited by the fuel. Therefore,
The response speed of the valve body 52 can be improved.

When the valve body 52 is seated on the valve seat 51d, the plunger 37 starts pressurizing the fuel. The pressurized fuel is pumped through passages 22 and 45 to fuel injection nozzle 44 . Then, the needle valve 44a is lifted, and fuel is injected from the injection hole of the fuel injection nozzle 44.

In the latter half of the pressurizing movement of the plunger 37, when the control unit determines that it is time to end fuel injection, the electromagnetic solenoid 57 is de-energized. Then, the valve body 52 is lifted from the valve seat 51d by the urging force of the valve spring 58.
The response speed of the valve body 52 during this lift is also improved in the same way as described above. When the valve body 52 lifts, the fuel reservoir chamber 60 communicates with the fuel pressurizing chamber 33 via the fuel supply return chamber 53, and the fuel in the fuel pressurizing chamber 33 flows into the fuel reservoir chamber 60. As a result, the pressure within the fuel pressurizing chamber 33 decreases, and fuel injection ends.

Here, from the fuel pressurizing chamber 33 to the fuel reservoir chamber 61
When fuel flows into the valve body, a portion of the fuel enters between the valve body 52 and the stopper member 61. However, the fuel flows out into the fuel tank 9 through the spill hole 63. Therefore, the valve body 52 is hardly pressed in the seating movement direction by the fuel. Therefore, the valve body 52 can be prevented from moving backward, and the valve body 52 is quickly lifted until it hits the stopper member 61. Therefore, it is possible to improve fuel injection failure.

When the plunger 37 moves back, the electromagnetic solenoid 57 is de-energized, and the valve body 52 remains in contact with the stopper member 61.
In this state, the spill hole 63 is blocked by the valve body 52. Therefore, the fuel supplied from the pump 8 into the fuel reservoir chamber 60 is drawn into the fuel pressurizing chamber 33 without flowing out from the spill hole 63 to the tank 9.

Thereafter, repeat the above steps.

It should be noted that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the gist thereof.

For example, in the above embodiment, the valve body 52,
Although the electromagnetic solenoids 57 and the like are respectively assembled to the main body 2, a solenoid valve in which they are assembled to a casing separately from the main body 2 may be prepared in advance and then assembled to the main body 2. .

In addition, as shown by the two-dot chain line in Fig. 2,
A leak hole 26 may be formed in the side portion 2b, extending downward from the armature chamber 56a and opening at the lower end surface of the side portion 2b. Such a leak hole 26
By forming this, fuel leaked from the fuel supply return chamber 53 and the fuel reservoir chamber 60 into the armature chamber 56a through between the valve body 52 and the small diameter hole 51a can be returned to the outside. It is possible to reliably prevent the armature chamber 56a from being filled with fuel.

〔Effect of the invention〕

As explained above, according to the unit type fuel injection device of the present invention, the armature chamber is isolated from the fuel circulation system, one end of the stopper portion is opened to the surface against which the valve body abuts, and the other end is opened to the atmospheric pressure. The stopper part forms an open spill hole, and the size of the opening of the spill hole is set so that when the valve body abuts against the stopper part, the opening of the spill hole is blocked by the valve body. Since the dimensions of the valve body are set smaller than the dimensions of the valve body at the end face that abuts on the valve body, the response speed of the valve body can be improved, and
It is possible to prevent the reverse movement of the valve body and improve the cut-off of fuel injection, and furthermore, the synergistic effect of these effects can provide effects such as being able to realize high injection for a short period of time.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of the present invention, with Figure 1 being an enlarged front sectional view showing the main parts, Figure 2 being a front sectional view, and Figure 3 being a side sectional view. . 3...Fuel pressurization section, 4...Fuel injection section, 5...Solenoid valve section, 33...Fuel pressurization chamber, 37...Plunger, 44
...fuel injection nozzle, 51d...valve seat, 52...valve body,
55... Armature, 57... Electromagnetic solenoid (moving means), 58... Valve spring (moving means), 60...
Fuel reservoir chamber, 61...stopper member (stopper part), 63...spill hole.

Claims (1)

[Claims] 1. A fuel pressurizing section that has a fuel pressurizing chamber into which fuel is introduced and a plunger that pressurizes the fuel in this fuel pressurizing chamber, and a fuel injection section that injects the fuel pressurized by the fuel pressurizing section. , a fuel reservoir chamber that communicates with the fuel pressurizing chamber via a valve seat and into which fuel is supplied; a valve portion that is disposed with one end protruding from the fuel reservoir chamber and is seated on the valve seat; an armature provided at the other end of the valve body, an armature chamber for movably housing the armature, and a solenoid valve portion having a moving means for seating and lifting the valve body with respect to the valve seat. In the unit type fuel injection device, the unit type fuel injection device is provided with a stopper portion that restricts the lift amount of the valve body by abutting one end surface of the valve body protruding inside the fuel reservoir chamber, the armature chamber A spill hole is formed in the stopper portion that is shut off from the fuel circulation system, one end of which opens to the surface where the valve body abuts, and the other end of which is open to atmospheric pressure, and the dimensions of the opening of this spill hole are defined. is set to be smaller than the dimension of the valve element at the end face that abuts the stopper part so that the valve element is shielded by the valve element when the valve element abuts the stopper part. Injection device.