JPH0468462B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel control device for a fuel injection pump.

[Conventional technology]

There are two types of fuel control for diesel engine fuel injection pumps: one is to end fuel injection by spilling fuel, and the other is to suck in the required amount of fuel during the intake stroke and inject the entire amount. , the present invention is an improvement of the latter type.
Such a fuel control device is disclosed in, for example, Japanese Patent Application Laid-open No. 1986-
It is disclosed in Publication No. 38367.

[Problem that the invention seeks to solve]

The invention described in the above publication forms two pump chambers in the cylinder of a fuel injection pump, and controls the amount of suction into each pump using a solenoid valve, thereby improving the injection amount and timing. It is designed to determine the following. The use of such a fuel injection pump requires complicated assembly, and there are problems in that the solenoid valves available today have limited responsiveness. Currently, more precise fuel injection control is required to reduce fuel consumption, emissions, noise, etc., but devices using electromagnetic valves are no longer able to meet such demands.

Excellent response can be obtained by using an electrostrictive element, but since the amount of operating displacement is small, precise finishing of related parts and accurate positioning during assembly are required, so simply using an electrostrictive element is not possible. Therefore, it is not possible to precisely control fuel injection. An object of the present invention is to provide a fuel control device that can perform precise control using an electrostrictive element.

[Means for solving problems]

According to the present invention, there is provided a fuel control device provided in the middle of a fuel suction passage of a fuel injection pump having a pump chamber formed by a plunger inserted into a cylinder, the fuel control device being provided in the middle of a fuel suction passage of a fuel injection pump, which a housing having a fuel passage formed therein; an electrostrictive element inserted into the cylinder and expanding and contracting according to applied voltage; and an electrostrictive element inserted into the cylinder and reciprocating according to the expansion and contraction of the electrostrictive element. the piston, a valve body capable of blocking the fuel passage, and a pressure chamber formed between the valve body and the piston; The pressure in the pressure chamber is decreased to cause the valve body to open the fuel passage, and the expansion of the electrostrictive element increases the pressure in the pressure chamber to cause the valve body to close the fuel passage. There is provided a fuel control device which sucks fuel between these opening and closing of the body and injects the sucked fuel from the fuel injection pump.

〔Example〕

FIG. 1 shows a distribution type fuel injection pump 1 according to the present invention.
0 and a fuel metering device 12 as a fuel control device incorporated in this pump 10. Second
The figure is an enlarged view of this fuel metering device.

In FIG. 1, a distribution type fuel injection pump 10 has a pump body 14, in which a cylinder 14 and a fuel storage chamber 18 are formed. Fuel is constantly supplied to the fuel storage chamber 18 from a fuel tank 20 by a feed pump 22, and its pressure is maintained approximately constant by a pressure regulating valve 24. A plunger 26 is slidably inserted into the cylinder 16, and a pump chamber 28 is formed at its distal end. The pump chamber 28 communicates with the fuel storage chamber 18 through fuel intake passages 30a and 30b. A distribution port 32 is formed from the tip of plunger 28 through its center, and opens radially at a midpoint location of the plunger. Corresponding to this radial opening,
The same number of distribution passages 34 as the number of cylinders are formed in the cylinder 16 , and the distribution passages 34 communicate with a fuel injection nozzle 38 via a delivery valve 36 . Therefore, when the plunger 26 moves to the left in FIG. 1, fuel is sucked into the pump chamber 28, and when it moves to the right, the fuel in the pump chamber 28 is pressurized and fed to the fuel injection nozzle 38.

The plunger 26 is connected via a known joint to a drive shaft 40 that rotates in synchronization with the engine, similar to a conventional distribution type fuel injection pump, and rotation is transmitted from the drive shaft 40. It has become possible to move freely. Furthermore, a face cam 42 is attached to the plunger 26,
The face cam 42 is urged by a spring 44 and engaged with a roller 46. It will be appreciated that the engagement of face cam 42 and roller 46 causes plunger 26 to reciprocate. As will be explained in more detail below, in the present invention the spring force of spring 44 is selected such that cam 42 and roller 46 are not necessarily in constant contact. Further, the roller 46 is controlled by a known timer mechanism (not shown).

A signal rotor 48 is further attached to the drive shaft 40, and the signal rotor 48 has one protrusion 48a provided on its end face and uneven protrusions 48b provided every 5 degrees on its outer circumference. Magnetoresistive element sensors 50 and 52 are provided for detecting passage of protrusions 48a and 48b, respectively. Detection signals from these sensors 50 and 52 are input to an electronic control unit (ECU) 54, and a detection signal from an accelerator opening sensor 56 is also input to the control device 54. The control device 54 can be constituted by a digital computer, and the control device 54 can be configured by a digital computer, and
A control signal is sent to the fuel metering device 12 in response to the detection signals of 0, 52, and 56.

A cylindrical bore 58 is formed in the middle of the fuel suction passage 30 of the pump body 14 . The bottom surface of the cylindrical bore 58 is flat, and a fuel intake port 30a extending from the pump chamber 28 opens at the center of the bottom surface. The side surface of the cylindrical bore 58 is internally threaded to allow the cylindrical housing 60 of the fuel metering device 12 to be screwed thereon. The fuel suction passage 30b through which the fuel storage chamber 18 extends is connected to the cylindrical bore 5.
8 is opened between the bottom surface and the internal threaded portion.

1 and 2, the fuel metering device 12
has a cylindrical housing 60 as described above,
The lower end portion 62 of the outer surface has a smaller cross section than the remaining portion, and an annular passage 63 is formed between the cylindrical bore 58 and the cylindrical bore 58 when attached to the pump body 14.
is beginning to form. An external thread is cut on this small cross-section portion 62 to correspond to the internal thread of the cylindrical bore 58 . Furthermore, a seal ring 64 is disposed between the pump body 14 and the housing 60. Further, an annular projection 65 is formed on the lower end surface of the housing 60, and this annular projection 64
is seated on the bottom surface of the cylindrical bore 58 to separate the opening of the fuel intake passage 30a from the annular passage 63.

A large diameter cylinder 66 and a small diameter bore 68 are continuously formed in the housing 60 and are defined by a shoulder 60a. An electrostrictive element 70 and a piston 72 are inserted into the large diameter cylinder 66. The piston 72 is slidable within the cylinder 66, and a seal ring 74 is provided for sealing between the top and bottom of the piston 72. When the electrostrictive element 70 is used as an actuator, it is constructed as a laminate of disk-shaped elements, for example, 50 elements each having a thickness of 0.5 mm are laminated as is well known.
If a voltage of -500V is applied to a 0.5 mm element, it will shrink by about 1 μm, and a laminate of 50 elements will shrink by 50 μm. The electrostrictive element 70 made of a laminate of these elements has an insulating and heat-shrinkable tube 7.
It is included in 6. Insulating plates 78 are disposed on both end surfaces of the electrostrictive element 70, the insulating plate 78 on one end side contacts the piston 72, and the insulating plate 78 on the other end side is a blind wall of the housing 60 that closes the large diameter cylinder 66. Contact 80. In this way, when the electrostrictive element 70 and the piston 72 are in contact with the blind wall 80, the tip end surface of the piston 72 is located on the side of the cylinder 66 having a larger diameter than the shoulder 60a. ing. Note that there is an annular gap 82 between the large-diameter cylinder 66 and the heat-shrinkable tube 76, and the housing 60 has a blind wall 80 extending in the axial direction from the small-section portion 62.
A fuel passage 84 opens into the cylinder 66 near the
and a fuel passage 90 that opens into the cylinder 66 near the piston 72, extends axially, and opens into an annular groove 87 formed in the inner surface of the small diameter bore 68. Therefore, the electrostrictive element 70 can be cooled by the fuel passing through the large diameter cylinder 66. Further, in the embodiment, a lead wire 92 for energizing the electrostrictive element 70 is extended through the blind wall 80 in a liquid-tight manner.

Fitted within the small diameter bore 68 are an upper piece 94, a cylinder piece 95, and a lower piece 96, which have equal diameters, parallel flat end surfaces, and which connect the nut 98 to the housing 60.
The housing 60 is fixed by screwing into the shoulder 60a, and at this time the upper piece 94 comes into contact with the shoulder 60a. As mentioned above, the piston 72 is attached to the shoulder 6
Since the pressure has not reached 0a, a pressure chamber 100 is formed between the piston 72 and the upper piece 94. A disc spring 102 is disposed within the pressure chamber 100 and urges the piston 72 upward against the fixed upper piece 94.

A small through hole 104 is located in the center of the upper piece 94.
is formed. A cylinder 106 formed in the center of the cylinder piece 95 has a larger diameter than the small hole 104, and a valve body 108 is slidably inserted into the cylinder 106. In this case, cylinder 106
and the valve body 108, and through this clearance, fuel is supplied from below the valve body 108 to the pressure chamber 100 through the small hole 104 of the upper piece 94. It's becoming like that. Furthermore, a concave portion 110 is formed in the center of the bottom surface of the cylinder piece 90. The annular groove 88 on the inner surface of the bore 68 of the housing 60 described above is provided at a position corresponding to this recess 110, and radial small holes 112 are provided connecting the central recess 110 and the annular groove 88. It will be done. And lower piece 96 and nut 98
Small holes 114 and 116 are also provided in each of them.
Further, the valve body 108 is slightly shorter than the distance between the upper and lower surfaces of the upper piece 94 and the lower piece 96 that sandwich it, and can slide by the difference in distance, so that the outer circumference on the upper end side of the valve body 108 is reduced in diameter. By doing so, the spring 118 is arranged and the valve body 10 is
8 toward the lower piece 96 and is constantly energized. Further, the portion of the valve body 108 exposed within the concave portion 110 is formed in a stepped manner so that the pressure of the fuel within the concave portion 110 acts to move the valve body 108 upward. The fuel passage of the fuel metering device 12 described above is formed by the fuel passage 84, the cylinder 66, the fuel passage 90, the annular groove 88, the radial small hole 112, the recessed part 110, and the small holes 114, 116. As fuel passes through the electrostrictive element 70
It is designed so that it can be cooled.
However, it is also possible to connect the fuel passage directly to the recess 110 without passing through the cylinder 66.

When assembling the fuel metering device 12 having the above configuration, it is sufficient to tighten the nut 98 until the upper piece 104 comes into contact with the shoulder 60a, and no other adjustment is necessary. Further, when assembling the fuel metering device 12 to the fuel injection pump 10, it is sufficient to tighten the housing 60 to the bore 58 until the annular projection 65 is seated on the bottom surface of the bore 58, and no adjustment such as positioning is necessary. In addition, compared to conventional fuel injection pumps, fuel cut valves, suction ports, governors, plunger suction groups, etc. are unnecessary, and the structure of the injection pump can be made smaller and simpler.

[Effect]

The electrostrictive element 70 of the fuel metering device 12 is normally unenergized or has a positive voltage applied thereto, so that the electrostrictive element 70 is in an extended position and the valve body 108 is in the position of the piston 72. and pressure chamber 100
The small hole 114 is closed by the pressure of the hydraulic pressure. As mentioned above, the plunger 26 of the fuel injection pump 10 reciprocates and rotates in synchronization with the engine, and when the plunger 26 moves to the right in FIG. 1, it pressurizes and distributes the fuel in the pump chamber 28. port 32
and pumping fuel to specific fuel injection nozzles 38 via distribution passages 34 . When the plunger 26 moves to the left, it draws fuel into the pump chamber 28. In the present invention, the entire amount sucked into the pump chamber 28 when the plunger 26 moves to the left is pumped during the rightward movement of the plunger.

Referring to FIG. 3, A in the figure shows the plunger 26.
The upper right line segment indicates the pumping stroke, and the lower right line segment indicates the suction stroke. During the pressure feeding stroke of the plunger 26, fuel injection is performed from the fuel injection nozzle 38 as shown in FIG. On the other hand, in FIG. 1, one sensor 5 of the two magnetoresistive element sensors 50 and 52 that detects the angular position of the drive shaft 40
0 generates a reference signal θ ₁ B every rotation of the drive shaft 40, the other sensor 52 generates a phase signal C every 5 degrees, and the control unit (ECU) 54 generates a reference signal θ 1 B when the reference signal θ ₁ is turned on. Count the phase signal from . In the control unit (ECU) 54, the timing and engine to apply electricity to the electrostrictive element 70 are stored in advance in the form of a function of the accelerator opening degree and the rotation speed. For example, as shown in FIG. -500V is applied to the electrostrictive element 70 at θ ₂ of the suction stroke of No. 26. Then,
As described above, the electrostrictive element 70 contracts by about 50 μm, the piston 72 is pushed by the disc spring 102 and follows the electrostrictive element 70, and the pressure in the pressure chamber 100 decreases. Since a substantially constant hydraulic pressure is always acting on the shoulder of the valve element 108, the valve element 108 is pushed open by this oil pressure, and the upper end surface of the valve element 108 comes into close contact with the lower end surface of the upper piece 94. Since there is a substantial clearance between the valve body 198 and its cylinder 106, the hydraulic pressure in the pressure chamber 100 is at most equal to the pressure below the valve body 108, and the received pressure product is the pressure product of the small hole 104. becomes the cross-sectional area. On the other hand, the valve body 10
When the valve body 108 opens, the pressure receiving area on the lower side of the valve body 8 includes not only the above-mentioned shoulder but also the small diameter tip face when the valve body 108 opens. The valve state is maintained. Thus, fuel is sucked into the pump chamber 28 through the fuel suction passage 30a.

At a predetermined time θ ₃ , the above-mentioned −500V is removed or a slight positive voltage is applied, and the electrostrictive element 70 extends to its original position. Therefore, the piston 72 is pushed and the pressure in the pressure chamber 100 increases, and the valve body 108 is pushed down by the pressure and seats on the upper end surface of the lower piece 96, thereby closing the valve. The small hole 104 of the upper piece 94 acts as a throttle and allows a rapid increase in pressure, but as time passes, the pressure decreases and eventually becomes equal to the pressure below the valve body 108. However, the valve body 10
8 is biased by a spring 118, the valve is maintained in a closed state, and furthermore, the fuel passage 30
Even if high pressure acts from side a, the high pressure is limited to that corresponding to the cross-sectional area of the small hole 114 of the lower piece 96, and compared to this, the hydraulic pressure applied to the upper end surface of the valve body 108, which has a relatively large diameter, is The valve remains closed against such high pressure.

In this way, the amount of fuel is measured according to the period from when the valve body 108 opens to when it closes. Furthermore, as shown in the right half of FIG. 3, when the amount of fuel needs to be increased, it is sufficient to increase the energization period θ ₄ −θ ₅ to the electrostrictive element 70, and the amount of fuel can be set to an arbitrary amount. is possible. Furthermore, more precise control is possible by controlling the energization timing based on phase (angle) rather than time.

The plunger 26 of the fuel injection pump 10 changes its retracted position to the left in FIG. 1 depending on the amount of fuel sucked in. For example, when the amount of fuel intake is small, the inside of the pump chamber 28 becomes a negative pressure state while the plunger 26 is being returned by the spring 44 during its suction stroke, and the plunger 26 absorbs this negative pressure and the spring 44. Linear motion is stopped at the position where the spring forces are balanced. This position is shown by way of example in FIG. 3A by a. If the intake fuel quantity is large, the plunger 26 will stop further to the left, this position being indicated by b. The rotation of the plunger 26 is maintained at all times. Therefore, the start of the next fuel pumping stroke will vary depending on the amount of fuel sucked. In other words, when the intake fuel amount is small, the injection start timing θ ₆ is relatively late;
In the case where there are many cases, the plunger start timing θ ₇ is relatively early. This is convenient for fueling the engine.
Furthermore, if the energization start timings θ ₂ and θ ₄ are set to be immediately before the end of the pressure feeding stroke of the plunger 26, the pressure drop of the fuel injection nozzle 38 at the end of fuel injection will be rapid, resulting in failures such as secondary injection. Simultaneous injection can be prevented. Naturally, by controlling the energization start timing, the fuel injection amount can be accurately controlled.

Since the fuel metering device according to the present invention has very good responsiveness, it is also possible to perform pilot injection, which is effective for improving fuel efficiency, emissions, and noise reduction. In this case, if the electrostrictive element 70 is energized at θ ₈ immediately after the start of pumping and the energization is stopped at θ ₉ after a short period of time, the valve body 108 will open momentarily and the pressure in the pump chamber 28 will be reduced. decrease. By this, Figure 3 F
Pilot injection as shown is possible.
In this case, the fuel in the pump chamber 28 will flow backwards, so it is necessary to set the fuel supply amount in consideration of this.

FIG. 5 shows an example of a fuel metering device 12 having a valve body 108 having a conical tip, and the other structure is the same as the example shown in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, by using an electrostrictive element, the accuracy of fuel metering can be greatly increased, and pilot injection can also be performed. By arranging such a fuel control device in the fuel suction passage of the injection pump, the structure of the fuel control device and the fuel injection pump can be simplified, and assembly and assembly can be performed easily. become able to. and,
Since the fuel at a relatively low pressure in the middle of the fuel intake passage is controlled, a small driving force is required, and from this point of view as well, the fuel control device can be downsized. Furthermore, by inserting fuel only when the electrostrictive element contracts, a fail-safe function can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a fuel injection pump to which the present invention is applied, FIG. 2 is an enlarged view of the fuel metering device of FIG. 1,
FIG. 3 is a diagram for explaining the operation, FIG. 4 is a diagram for explaining another operation, and FIG. 5 is a sectional view of a second embodiment of the fuel metering device. 10... Injection pump, 12... Fuel metering device,
26...Plunger, 28...Pump chamber, 30
a, 30b... Fuel intake passage, 60... Housing, 84, 90, 110, 114, 116... Fuel passage, 66... Cylinder, 70... Electrostrictive element,
72...piston, 108...valve body.

Claims (1)

[Scope of Claims] 1. A fuel control device provided in the middle of a fuel suction passage of a fuel injection pump having a pump chamber formed by a plunger inserted into a cylinder, the device comprising: a housing in which a fuel passage forming a part is formed; an electrostrictive element that is inserted into the cylinder and expands and contracts according to the applied voltage; and an electrostrictive element that is inserted into the cylinder and reciprocates according to the expansion and contraction of the electrostrictive element. a moving piston,
comprising a valve body capable of blocking the fuel passage, and a pressure chamber formed between the valve body and the piston,
Retraction of the electrostrictive element reduces the pressure in the pressure chamber via the piston, causing the valve body to open the fuel passage, and expansion of the electrostrictive element increases the pressure in the pressure chamber. The fuel control device is configured to cause the valve body to shut off the fuel passage, and to cause the fuel injection pump to inject fuel sucked in between opening and shutoff of the valve body. 2. The control means includes a control means for applying a voltage to the electrostrictive element, and a sensor for detecting the angular position of the plunger, and the control means starts energization to the electrostrictive element and controls the energization based on the output of the sensor. Claim 1, characterized in that the energization end timing is controlled.
Fuel control device as described in section. 3. The control means energizes the electrostrictive element during the pump's pressure feeding stroke to open the valve body for a predetermined period of time, thereby temporarily lowering the pressure in the pump chamber to perform pilot injection. A fuel control device according to claim 2, characterized in that: 4. The control means energizes the electrostrictive element to open the valve body immediately before the end of the pump's pumping process,
3. The fuel control device according to claim 2, wherein the fuel injection is terminated by rapidly reducing the pressure within the pump chamber.