JPH0192535A - Fuel injection amount control device for fuel injection pump - Google Patents

Abstract

PURPOSE:To contrive at enhancing the durability of a valve element for opening and closing a passage between high and low pressure passages so as to allow high pressure fuel discharged from a fuel injection pump to overflow from the high pressure passage into the low pressure passage, by making the pressure receiving area of the valve element for the high pressure fuel smaller. CONSTITUTION:A fuel injection amount control device disposed in a casing 91 opens and closes a passage between high and low pressure passages 74, 60. A piezo-actuator 95 adapted to abut against a piston 94 is disposed in a storage chamber 93 formed in the casing 91. A stopper 99 is secured to a valve body 101 and the like in a pressure chamber 97 formed in the storage chamber 93, and a valve element 105 is slidably disposed in a fitting hole 103 formed in the valve body 97 and communicated with the pressure chamber 97. Further, the pressure receiving area of the valve element 105 for the liquid pressure in the high pressure passage 74 is made to be smaller than the receiving area for the liquid pressure in the low pressure passage 60.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection amount control device for a fuel injection pump for a diesel engine. Regarding the side f# device.

[Prior art and its problems] Conventionally, as this type of injection amount control aj device, for example, the one shown in FIG. 3, disclosed in Japanese Patent Application Laid-open No. 118528/1988, is known. That is, the present control device 200 includes a piezo actuator 204 provided in a housing chamber 203 formed in a housing 202, and
The valve body 21 pressurizes the fuel in the pressure chamber 20B through the piston 206 by expanding and contracting 04, and connects the high pressure passage 210 and the low pressure passage 214 communicating with the fuel injection pump main body (not shown) to the valve body 21.
It opens and closes at 6. Valve body 21G of this device 200
A ridge 212 is formed inside, which allows constant communication between the pressure chamber 20 and the high pressure passage 210.

However, in this device 200, the force that moves the valve body 216 is mainly the hydraulic pressure in the pressure chamber 208 due to the pressurization of the piezo actuator 2゜4 and the injection pressure applied to the valve body 216. The valve body 216 is moved, but since the plunger chamber (not shown) communicates with the pressure chamber 20 via the high pressure passage 210 and the ridge 212, the substantial capacity of the plunger chamber increases and the injection pressure is increased. cannot be higher. Also, when viewed from the pressure chamber 20B side, the pressure chamber 20B communicates with the plunger chamber, so the pressurized fluid pressure decreases, and the small actuator 204 reduces the stroke amount of the valve body 216. There is a problem that the piezo actuator 204 becomes larger.

Additionally, if a foreign object gets caught in the sliding surface of the valve body 216,
Since the force for moving the valve body 216 is small, there is a problem in that the valve body 216 cannot perform a return operation to remove foreign matter by its own force.

As a technique to solve this problem, as shown in Figure 4,
A valve element 222 is provided to separate the pressure chamber 20 from the high pressure passage 220 and the low pressure passage 221, and a spring 224 is provided to apply a spring force to the valve element 222 in the valve closing direction. It has also been proposed that the valve body 222 is opened and closed by the valve body 222.

However, in this structure, the injection pressure is transferred between the valve body 222 and the pressure chamber 20.
Since the pressure is received by the piezo actuator 204 via the hydraulic pressure of B, the durability of the piezo actuator remains to be seen before it can be applied to ultra-high pressure fuel injection pumps that will be required in the future. In addition, since the valve body 222 is biased in the valve closing direction by the spring 224, at the time of overflow, the hydraulic pressure in the pressure chamber 20 and the fuel pressure in the high pressure passage 220 communicating with the plunger chamber are balanced. Even if the valve is opened, it may close again due to the spring force when the injection pressure decreases, causing secondary injection by repeating opening and closing.

The present invention has been made in order to solve the problems of the above-mentioned conventional technology, and has low load on the electromechanical transducer, excellent durability, stable movement of the valve body, and the generation of secondary injection. It is an object of the present invention to provide an injection amount control device for a fuel injection pump that is not easy to break down.

[Means for Solving the Problems] The present invention, which was made to solve the above problems, comprises: a pressure chamber filled with liquid; an electromechanical transducer that pressurizes the pressure chamber via a piston; A valve body that has a small pressure receiving area with respect to the pressure chamber and opens and closes between both passages in order to cause the high pressure fuel discharged from the fuel injection pump to overflow from the high pressure passage to the low pressure passage, and a spring that moves the valve body in the valve opening direction. The present invention is characterized in that the valve body is formed such that the pressure receiving area of the valve body for the fuel in the high pressure passage is smaller than the pressure receiving area for the fuel in the low pressure passage.

Here, the present fuel injection pump may be one that compresses fuel in a plunger chamber and pumps high-pressure fuel by using a plunger that receives driving force from an engine, and for example, a pump that compresses fuel in a plunger chamber and pumps high-pressure fuel. In addition to inner cam type pumps, it is also applicable to face cam type pumps and square-type fuel injection pumps.

The electromechanical transducer mentioned above refers to a piezoelectric element such as a piezo element, an electrostrictive element, a magnetostrictive element, etc. whose shape expands and contracts in response to an electric signal.

[Operation] When an electric signal is applied to the electromechanical transducer of the injection amount control device of the present invention, the electromechanical transducer expands, and the liquid in the pressure chamber is compressed through the piston to become high pressure. The high pressure of this fluid is applied to the end face of the valve body, and the valve body closes against the spring force and the hydraulic pressure of the high pressure◆low pressure passage. In this state, the forces that are applied to the valve body in the valve opening direction are the injection pressure in the high pressure passage and the fuel pressure and spring force in the low pressure passage, but the pressure receiving area of the valve body for fuel is in the direction of the high pressure passage. Since the fuel pressure passage is formed smaller than the low pressure passage, high pressure corresponding to the fuel pressure from the high pressure passage is not applied to the pressure chamber via the valve body.

Therefore, the injection pressure pushes the valve body and reduces the pressure applied to the electromechanical transducer from the hydraulic pressure in the pressure chamber via the piston, increasing the durability of the electromechanical transducer.

In addition, since the high pressure passage communicating with the plunger chamber is separated from the pressure chamber by the valve body, the capacity of the plunger chamber for pumping fuel becomes substantially smaller, thus increasing the injection pressure. .

Furthermore, when the electrical signal to the electromechanical transducer stops,
As the element shrinks, the hydraulic pressure in the pressure chamber decreases. As a result, the force applied to the valve body by the hydraulic pressure in the pressure chamber becomes smaller than the sum of the spring force and the injection pressure, and the valve opens quickly. Once the valve is opened, the valve is kept open by the splash even if the injection pressure decreases, so secondary injection does not occur.

[Example code] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a fuel injection pump for a diesel engine and its peripheral equipment, and this equipment has a foot pump 1, a fuel injection pump main body 3, and an injection amount control device 9 as main components.

The feed pump 1 pumps up fuel from a tank 13 through a passage 11 and supplies the fuel to the fuel injection pump main body 3 and the injection amount control device 9 through a passage 15. The fuel is then returned from the fuel injection pump body 3 through the passage 17. This passage 17 and the passage 1
3, a pressure regulating valve 23 for regulating the fuel supply pressure is provided.

The fuel injection pump main body 3 has a fitting hole 32 in the housing 31.
The rotor 41 is supported together with a bearing 39 in the through hole 37 of the sleeve 33 and rotationally driven by an engine (not shown). The fuel injection pump body 3 also includes a pressurizing mechanism 43 that pressurizes fuel to generate high-pressure fuel, and further includes a passage in the rotor 41, the housing 31, etc. for guiding the high-pressure fuel from the pressurizing mechanism 43. are doing.

Next, to explain the pressurizing mechanism 43 and its surroundings, a plurality of cylindrical holes 46 are formed in the rotor 41 in the radial direction around the plunger chamber 45, and a plunger/17 is installed in each of the cylindrical holes 46. The roller shoes 51 are fitted to be slidably movable, and a roller shoe 51 is disposed at the radially outer end of the blunter 47 to rotatably hold the roller 53. Further, an inner cam 55 having a cam crest formed on its inner surface is arranged on the outside of the roller 53, and therefore, the rotation of the rotor 41 causes the roller 53 to rotate against the cam surface formed on the inner circumferential surface of the inner cam 55. When the roller 53 slides, the roller 53 reciprocates in the radial direction based on the cam surface, and this movement of the rotor 53 causes the roller shoe 51 to move back and forth.
It is transmitted to plunger 47 through. Here, the stroke in which the plunger 47 moves outward in the radial direction of the rotor 41 is a suction stroke, and the stroke inward is a discharge stroke.

A passage 59 connected to the passage 15 from the feed pump 1 is provided as a passage in the housing 31 and the rotor 41 of the fuel injection pump main body 3, and an annular gear rally 61 connected to this passage 59 is provided. -61
A passage 63 in the sleeve 33, a suction passage 65 in the rotor 41, and an axial passage 66 are formed to supply fuel therein to the plunger chamber 45. Also, this passage 66
A discharge passage 67 communicating with and ? u? A passage 69 for M is formed to face in the radial direction of the rotor 41 and communicate with passages 71 and 73 provided in the sleeve 31, respectively. The other passage 73 is connected to a passage 74 communicating with the gear rally 61. In addition, sleeve 3
3 and the rotor 41, the passage 63 and the passage 65 communicate with each other during the suction stroke, and the passage 67 and the passage 71 communicate with each other during the suction stroke.
Then, the passage 73 and the passage 69 are blocked, and the situation is reversed during the discharge stroke.

Next, the operation of this embodiment will be explained.

A tank 13 is driven by an engine-driven feed pump 1.
The pressure of the fuel pumped up is regulated by the pressure regulating valve 23, and the fuel is constantly supplied to the gear rally 61 in the housing 31 through the passage 15.59.

Now, when the rotor 41 driven by the engine enters the intake stroke, the passage 63 and the passage 65 are connected to the sleeve 33.
(the position of the passage indicated by the glass line in FIG. 1), and the gear rally 61 communicates with the plunger chamber 45 through the passages 65 and 66 of the rotor 41. Then, the plunger 47 moves toward the outer circumferential side along the inner circumferential surface of the inner cam 55 via the shoe 51, so that the gear rally 6
Fuel is supplied from 1 to the plunger chamber 45 through each of the passages described above.

Roughly, the rotor 41 rotates, the passage 65 and the passage 63 are gradually closed, and the plunger chamber 45 is hermetically sealed. Then, the injection amount control device 9, which will be described later, is closed to close the passage 74, thereby starting the discharge stroke.

When the rotor 41 further rotates in this state, the roller 53 slides along the cam surface of the cam ridge of the inner cam 55, and the roller 53 moves radially inward based on the cam surface. As a result, the movement of the roller 53 is controlled by the roller shoe 5.
1 to the plunger 47. Plunger 4
7 pressurizes the fuel in the plunger chamber 45, and the passage 6
Fuel is pumped from delivery valve 77 via 6.67.75. Subsequently, when the injection amount control device 9 is deenergized and the valve is opened, the passage 74 and the passage 60 are brought into communication, the fuel in the plunger chamber 45 overflows, and the fuel injection ends. Then repeat the suction stroke again.

Next, the configuration and operation of the fuel injection amount control device 9 for overflowing the fuel from the fuel injection pump described above will be described using the enlarged view of FIG. 2. The injection amount control device 9 includes a casing 9
1 and opens and closes between a high-pressure side passage 74 and a low-pressure side passage 60 communicating with the plunger chamber 45. A storage chamber 93 is formed in the casing 91, and a piezo actuator 9 that is in contact with a piston 94 is placed in this storage chamber 93.
5 is stored. This piezo actuator 95 is made into a cylindrical shape by laminating about 80 disk-shaped piezo elements each having a thickness of about 0.5 mm, and is made of, for example, ceramic whose main component is lead zirconate titanate. When a voltage of about 500V is applied to the element, it expands by about 40u.

A part of the storage chamber 93 on the piston 94 side is a pressure chamber 97.
It becomes. At the bottom of this pressure chamber 97, a disk-shaped stopper 99 having a through hole 99a in the center is provided on the casing 9.
1 by the stepped portion 91a and the valve body 101. This valve body 101 is provided with a fitting hole 103 connected to the pressure chamber 97, and a valve body 105 is slidably fitted into this fitting hole 103. This valve body 105 includes a large diameter portion 107 having a diameter that fits into the fitting hole 103;
A small diameter part 109 having a smaller diameter than the large diameter part 107 is connected to the large diameter part 107, and the outer circumferential surface therebetween is formed into a tapered surface 111. Furthermore, the small diameter part 109 has a tip surface 113 at its tip and a tapered surface at its peripheral edge. 115 is formed to abut against the valve seat 117. A passage 74 communicating with the plunger chamber 45 described above is formed in the valve body 101, and a portion of this passage 74 is an annular passage 74a surrounding the valve body 105. A low-pressure side passage 60 communicating with the lower end of the annular passage 71a in the drawing is formed. Therefore, the valve body 105 has a large diameter portion 1
07 and the small diameter portion 109, the pressure receiving area of the valve body 105 corresponding to the hydraulic pressure of the passage 74 on the high pressure side almost corresponds to the tapered surface 111, and the pressure receiving area of the valve body 105 corresponding to the hydraulic pressure of the passage 60 on the low pressure side corresponds to the tip surface 113 etc. It is smaller than the pressure receiving area of .

Further, a spring 119 is provided that contacts the tip end surface 113 of the valve body 115 and the inner wall of the passage 60 on the low pressure side, and the spring 119 biases the valve body 105 toward the pressure chamber 97 side. are doing.

Note that the pressure chamber 97 is connected to the valve body 10 as shown in FIG.
1 → a passage 133 in the sleeve 33 → a passage 135 in the outer circumference of the rotor 41 → a passage 63 in the sleeve 33 so that the rotor can be connected to the gear rally 61 at the suction stroke position of the rotor 41 41 passage 135 is passage 1
33 and the passage 63 are communicated with each other to supply fuel from the gear rally 61 to the pressure chamber 97.

This injection amount control device 9 receives a signal indicating the operating state of the engine, such as an accelerator opening sensor 121 shown in FIG. 1 or a rotation angle sensor 123 built in the distributor.
The piezo actuator 95 is driven by applying a control signal to the piezo actuator 95 by the electronic control unit 125 based on detection signals such as the above.

To explain the operation of the injection amount control device 9, when a control voltage is output to the piezo actuator 95 during the discharge stroke, the piezo actuator 95
expands and increases the pressure of the fuel in the pressure chamber 97 via the piston 94. This high) sound pressure is applied to the end face of the valve body 105, and the valve body 105 moves in the direction of the arrow a against the spring force and the fuel pressure applied to the valve body 105, thereby closing the passage 74.

At this time, the force applied to the valve body 105 in the direction of the arrow is the force exerted by the injection pressure of the passage 74 on the high pressure side on the tapered surface 111 of the valve body 105, and the low pressure applied to the tip surface 113 of the valve body 105. This is the sum of the fuel pressure in the side passage 60 and the splashing force.

Then, in the above-described state in which the passage 74 is blocked, fuel injection is performed by the fuel injection pump.

Next, to stop fuel injection, the voltage applied to the piezo actuator 95 is deenergized.

As a result, when the hydraulic pressure in the pressure chamber 97 decreases, the valve body 10
The force applied in the direction of the arrow 5 exceeds the force in the direction of the arrow a, and the valve body 105 lifts.

As a result, the fuel in the high pressure side passage 74 is transferred to the low pressure side passage 60.
The fuel will overflow and fuel injection will stop. Then, when the fuel injection stroke starts again after passing through the suction stroke, a control voltage is applied to the piezo actuator 95, the passage 74 is closed by the valve body 105, and the process waits until the time of beneficial flow.

In addition, since the passage 135 on the outer periphery of the rotor 41 communicates with the passage 63.133 of the sleeve 33 during the suction stroke, fuel is replenished from the gear rally 61 to the pressure chamber 97.
The initial pressure in the pressure chamber 97 is stabilized.

Therefore, the injection amount control device 9 has the following effects.

■ During the discharge stroke, the passage 74 communicating with the plunger chamber 45 has a high injection pressure, and this injection pressure causes the valve body 1 to
Since the force acting on the piezo actuator 05 is only the force acting on the tapered surface 111, the pressing force applied to the piezo actuator 95 is reduced, the load on the piezo actuator 95 is lightened, and the durability of the device is increased.

■ When the control voltage to the piezo actuator 95 is deenergized, the piezo actuator 95 returns to its original state and the hydraulic pressure in the pressure chamber 97 decreases, but the force for opening the valve is
In addition to the injection pressure applied to the tapered surface 111, the spring force of the spring 119 also acts on the valve body 105, so the valve is quickly opened, fuel overflows, and injection is stopped. Moreover, after the valve is opened, the spring force of the spring 119 is always acting in the direction of opening the valve, so as explained in the prior art (Fig. 4), the injection pressure in the passage 74 can be increased or decreased. Regardless of the timing, the valve does not close, and therefore, secondary injection does not occur.

■ Since the pressure chamber 97 of the injection amount control device 9 and the passage 74 are separated by the valve body 105, the flow of fuel near the sliding part of the valve body 105 is small, so that the amount of fuel contained in the fuel is reduced. Foreign matter is difficult to get caught between the valve body 105 and the fitting hole 103, and even if it gets caught in the valve body 105, the pressure chamber 9
The valve body 105 receives high hydraulic pressure when pressurized in step 7 and moves quickly, and foreign matter is quickly and easily removed, so the self-returning force is large.

(2) Since the plunger chamber 45 is separated from the pressure chamber 97, the substantial capacity of the plunger chamber 45 that pressurizes the fuel is reduced, making it possible to achieve high injection pressure. vice versa,
When viewed from the pressure chamber 97 side, the substantial capacity of the pressure chamber 97 itself is also small, so the piezo actuator 95 may also be small.

(2) Moreover, since the pressure chamber 97 of the injection amount control device 9 is oil-tight, the valve body 105 returns quickly without using a spring 115 with a large spring force.

[Effects of the Invention] As explained above, according to the present invention, since the pressure receiving area of the valve body to which the fuel injection pressure is applied is made small, high pressure is applied to the electromechanical transducer through the hydraulic pressure of the pressure chamber. Since no pressure is applied, the load on the piezo actuator is reduced, and the durability of the device can be increased.

In addition, when the application of the control voltage to the electromechanical transducer is stopped and the hydraulic pressure in the pressure chamber is reduced, the valve is opened, and the stable valve opening state is maintained by the force of the spring in the valve opening direction.
No secondary injection occurs.

Furthermore, since the valve body moves quickly due to the high hydraulic pressure in the pressure chamber, foreign matter that impedes movement of the valve body is easily removed, and self-returning force is large.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a fuel injection pump and its peripheral equipment according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view showing an injection amount control device of the same embodiment, and FIGS. 3 and 4 are conventional FIG. 3 is a cross-sectional view showing the fuel injection control valve of FIG. 3...Fuel injection pump body 9...Injection amount control device 93...Storage chamber 95...Piezo actuator (electromechanical conversion element) 97...Pressure chamber 101...Valve body 105...
Valve body 107... Large diameter part 109... Small diameter part 11
9... Hane agent Patent attorney Tsutomu Sadatsu (and 1 other person) Figure 2 Q9 Figure 4, (/ ~□

Claims (1)

[Scope of Claims] A pressure chamber filled with liquid, an electromechanical transducer that pressurizes the pressure chamber via a piston, and high-pressure fuel that has a smaller pressure receiving area for the pressure chamber than the piston and is discharged from a fuel injection pump. A valve for fuel in a high-pressure passage, comprising: a valve element that opens and closes between both passages in order to cause fuel to overflow from the high-pressure passage to the low-pressure passage; and a spring that applies a spring force to the valve element in the valve opening direction. An injection amount control device for a fuel injection pump, characterized in that a valve body is formed so that a pressure receiving area of the valve body is smaller than a pressure receiving area for fuel in a low pressure passage.