JPH0335502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel pump in which the position of a residual fuel relief valve provided in a fuel injection pump is detected using a capacitive potentiometer.

Conventional fuel pumps include, for example, those shown in FIGS. 1a and 1b.

The fuel injection pump 1 shown in FIG. 1b is configured such that a plunger 3 rotates and reciprocates in the axial direction by the rotation of a cam disc 2 connected to a drive shaft (not shown) of a diesel engine. ing.

Then, in the suction stroke, when the plunger 3 moves to the left in the drawing, the suction vertical groove 4 coincides with the fuel inflow passage 5, so that fuel is sucked into the operating space 6 of the plunger 3.

Next, in the discharge stroke, the plunger 3 starts moving to the right in the figure, the sucked fuel passes through the discharge vertical passage 7, and when the discharge vertical groove 8 coincides with the discharge passage 9, the check valve 10 is activated. The liquid is then discharged to an injection valve (not shown) in the cylinder.

At this time, the injection pump 1 finishes discharging fuel from the escape passage 11 formed in the plunger 3 to the outside of the injection pump 1 (space inside the pump housing).
The opening and closing of this relief passage 11 is performed by a cylindrical relief valve 12 that is slidably fitted into the outer periphery of the plunger 3. Furthermore, by sliding the relief valve 12, the opening position of the relief passage 11 can be adjusted.

That is, if the relief valve 12 is moved to the right side in the figure, the closing period of the relief passage 11 will be extended, and the time from the start to the end of fuel discharge will be lengthened accordingly, and the fuel injection amount will be increased. Become. Conversely, if the relief valve 12 is moved to the left in the figure, the time from the start to the end of fuel discharge will be shortened, and the fuel injection amount will be reduced.

The mechanism for sliding the relief valve 12 is as follows:
an electromagnet 15 having two coils 14, 14 wound around an iron core 13 in which a cylindrical gap is formed;
It is generally composed of a rotating permanent magnet 18 rotatably supported by a housing 17 via a rotating shaft 16 within the cylindrical gap.

A sector-shaped piece 19 is provided at the lower end of the rotating shaft 16.
is attached eccentrically, and a spherical engagement piece 20 fixed eccentrically with respect to the center axis of this fan-shaped piece 19 fits into the hole 21 of the relief valve 12, and as the rotating permanent magnet 18 rotates. The relief valve 12 is configured to slide.

A driving current for the electromagnet 15, which determines the rotation angle of the rotating permanent magnet 18, is supplied from a control circuit 23 via an amplifier 22, as shown in FIG. 1a.

The control circuit 23 includes various engine operating parameters such as an engine rotational speed signal from a rotation sensor 25, an accelerator pedal position signal from an oscillator 26, and other (not shown) signals related to intake pipe negative pressure, engine temperature, ambient temperature, etc. Signals are input, and a drive current corresponding to the optimum fuel injection amount determined based on these operating parameters is output and supplied to the electromagnet 15.

Furthermore, a differential transformer 2 is connected to the control circuit 23.
A feedback control signal is supplied from 7.

That is, the movable core 2 of the differential transformer 27
The tip of the arm 27b connected to the arm 7a is in contact with the rotating permanent magnet 18, and the rotating permanent magnet 18
Whether or not the output of the differential transformer 27, which fluctuates as the movable iron core 27a moves in response to the rotation angle of The rotation angle of the rotating permanent magnet 18 is corrected as appropriate.

The rotation sensor 25 is arranged to face a toothed disc 24 attached to the drive shaft of the engine, and generates an alternating current voltage proportional to the engine rotation speed from an induction coil 25b wound around a magnet 25a. 28 is the differential transformer 2
This is an oscillator that supplies an alternating current for exciting the primary coil of No. 7.

With the above configuration, the fuel injection amount is controlled to optimize fuel efficiency and power performance.

However, in the conventional fuel injection pump as described above, since the operating position of the relief valve 12 is indirectly detected based on the rotation angle of the rotating permanent magnet 18, the arm 27b and Installation errors between the rotary permanent magnet 18 and the rotating shaft 16, the eccentric fan-shaped piece 20, the spherical engagement piece 21, etc., errors due to wear, etc., affect the detection accuracy of the operating position of the relief valve 12, and ultimately This was a factor that reduced the accuracy of fuel injection amount control.

The present invention has been made in view of the above circumstances, and in a fuel injection pump that controls the amount of fuel injection by adjusting the operating position of the relief valve, such as the conventional example, the operating position of the relief valve can be adjusted to a static position. By using a capacitance type potentiometer for direct detection, the detection accuracy of the operating position of the relief valve is improved, good responsiveness is ensured, and the control accuracy of the fuel injection amount is improved. The purpose of the present invention is to provide a fuel injection pump with improved performance.

Hereinafter, embodiments of the present invention will be described in detail using the drawings from FIG. 2 onwards.

FIG. 2 is a sectional view showing one embodiment of the fuel injection pump according to the present invention (hereinafter referred to as the first embodiment). Note that the same components as those of the conventional example shown in FIGS.

The fuel injection pump shown in the same figure has the same cam disc 2 and plunger 3 as the conventional example shown in Fig. 1b.
The fuel intake and discharge strokes are configured to be performed in the same manner as in the conventional example.

In this fuel injection pump, a relief valve 29 opens and closes the fuel relief passage 11.
However, an annular permanent magnet 30 is slidably fitted into the outer periphery of the plunger 3, and ring-shaped magnetic pole pieces 31a made of magnetic material are joined to both ends of the permanent magnet 30.
31b, and a ring-shaped moving electrode 32 made of a conductive material such as aluminum attached to both ends of the permanent magnet 30 via these magnetic pole pieces 31a and 31b.
a, 32b.

Further, an electromagnetic actuator 70 (hereinafter simply referred to as an actuator) is provided so as to cover the outer periphery of the relief valve 29 in a non-contact manner. and two field coils 33a and 33b arranged in parallel in the axial direction of the plunger 3, an outer covering yoke 36 made of an annular magnetic material that covers and fixes the outer periphery of these field coils 33a and 33b, and this outer covering. It is generally composed of operating position sensors 34a and 34b fitted to both ends of a yoke 36.

As shown in FIG. 4, the operating position sensors 34a, 34b are made of an insulating material such as ceramic or synthetic resin, and are formed in a medium-height annular shape with an annular protrusion 38 formed in the center. 38 On the top surface,
Two-part ring-shaped fixed electrodes 35a, 35b, 35c, and 35d made of a good conductor such as copper are formed by printing and firing or the like. Furthermore, each of the fixed electrodes 3
5a, 35b, 35c, 35d have lead terminals 37a, 37b, 37 that penetrate to the back surface of the convex portion 38.
c and 37d are connected to each other.

The operating position sensors 34a, 34b
As shown in FIG. 3, each of the fixed electrodes 35a, 35
b, 35c, 35d face the end surfaces of the moving electrode rings 32a, 32b of the relief valve 29,
They are arranged with small gaps l ₁ and l ₂ in between.

The sum of the small gaps l ₁ and l ₂ (l ₁ + l ₂ ) is constant,
This becomes the movement range of the relief valve 29.

Actuator drive and relief valve 29
Electrical control of detection of the operating position is performed by a control system shown in FIG.

In the same figure, the arithmetic circuit 40 is shown in FIG.
As shown in FIG. 2, the engine rotation speed signal from the rotation sensor 25, the access pedal position signal from the oscillator 26, and other engine operating parameter signals such as signals related to intake pipe negative pressure (not shown), engine temperature or ambient temperature, etc. is input, the optimum fuel injection amount is calculated based on these operating parameters, and the calculated injection amount data is sent to the control circuit 41.
It is intended to be supplied to

The control circuit 41 controls the excitation current of the field coils 33a and 33b supplied via the drive circuit 42, and uses the injection amount data supplied from the arithmetic circuit 40 and the relief supplied from the sensor circuit 43. The excitation current is controlled so that the detected data of the operating position of the valve is compared and the two are in an equilibrium state.

The drive circuit 42 controls the field coils 33a and 3 based on the excitation current control signal from the control circuit 41.
The relief valve 29 is moved and positioned to a predetermined operating position by varying the direction and magnitude of the excitation current supplied to the magnet 3b and changing the magnetic field acting on the permanent magnet 30 of the relief valve 29.

The sensor circuit 43 is connected to the operating position sensor 34.
It outputs detection data of the operating position of the relief valve based on the capacitance data obtained from the capacitors a and 34b, and constitutes a type of capacitance type potentiometer.

That is, fixed electrode 35a - moving electrode 32a -
Variable capacitors C ₁ and C ₂ are formed between the fixed electrodes 35b and between the fixed electrodes 35c, the moving electrodes 32b, and the fixed electrodes 35d, respectively.
These capacitors C ₁ and C ₂ are incorporated into an AC bridge 44 as shown in FIG. 6, and an output based on the level of the unbalanced voltage e is supplied to the control circuit 41 as the detection data.

The above unbalanced voltage e is expressed by the above capacitors C ₁ and C ₂
Let Ca and Cb be the capacitances of Since it is determined depending on the length _of the small gaps l _{1 and l 2} , _the following relationship holds true: Relief valve 29
The operating position of is found.

The unbalanced voltage e outputted from the AC bridge 44 is rectified by a full-wave rectifier 45, amplified by a differential amplifier 46, and then converted to a DC voltage level via a peak hold circuit 47 as detected data. Output.

As mentioned above, for this fuel injection pump,
By adopting a configuration in which the operating position of the relief valve is directly detected by the operating position sensors 34a and 34b, detection accuracy can be greatly improved.

In addition, in this embodiment, the relief valve is configured with an annular permanent magnet 30, and by controlling the excitation current supplied to the field coils 33a and 33b of the actuator, the relief valve can be moved and positioned in a non-contact manner. Because it is a non-contact direct acting type and a detection type, the structure is simpler than conventional mechanical actuators, and installation errors can be reduced. , good responsiveness can be ensured.

It goes without saying that the permanent magnet 30 may be arranged only on the outer circumferential surface of the relief valve.

FIG. 7 shows another embodiment (hereinafter referred to as the second embodiment) of the present invention.
FIG. In this figure, only the relief valve and the actuator are shown, but the other components are the same as those in the first embodiment, so illustrations and explanations will be omitted, and the same as shown in FIG. The same components are given the same reference numerals and their explanations will be omitted.

The relief valve 50 of the fuel injection pump shown in the same figure is
Similar to the first embodiment, magnetic pole pieces 31 are attached to both ends of the annular permanent magnet 30 fitted into the plunger 3.
Ring-shaped moving electrodes 51a and 51b made of a conductor such as aluminum are attached via a and 32b.

The outer peripheries of the movable electrodes 51a and 51b are formed into a tapered shape that contracts toward the tips.

Further, as in the first embodiment, the actuator includes field coils 33a and 33b surrounding the outer periphery of the relief valve 50 in a non-contact manner, an outer yoke 36, and an actuator fitted into openings at both ends of the outer yoke 36. It is composed of position sensors 52a and 52b.

As in the first embodiment, the operating position sensors 52a and 52b are made of an insulating material such as ceramic or synthetic resin, and are formed into a medium-height annular shape with an annular convex portion provided in the center.

The central circular hole is formed in a tapered shape corresponding to the outer peripheral shape of the moving electrodes 51a and 51b of the relief valve 50 so as to face the tapered surfaces of the moving electrodes 51a and 51b of the relief valve 50 with a small gap therebetween. , said first
Two-part tapered fixed electrodes 53a, 53b, 53c made of the same good conductor as in the embodiment,
53d is formed. Although not shown, lead terminals are connected to each of the fixed electrodes 53a, 53b, 53c, and 53d.

In the fuel injection pump configured as described above, the operation of detecting the operating position of the relief valve and the driving operation of the actuator are completely performed by the control system shown in FIGS. 5 and 6 as in the first embodiment. It is done in the same way. Therefore, a description of the operation will be omitted.

Therefore, the fuel injection pump of the second embodiment exhibits the same effects as the fuel injection pump of the first embodiment, and as described above, the movable electrodes 51a, 51b and the operating position sensors 52a, 5
By making the surface facing 2b tapered to expand the electrode area, the change in capacitance associated with the movement of the relief valve 50 becomes large, thereby further improving the detection accuracy of the operating position of the relief valve 50. It becomes possible to do so.

FIG. 8 shows still another embodiment of the present invention (hereinafter referred to as
FIG. 3 is a sectional view showing a third embodiment (referred to as a third embodiment). In addition, in the figure, similarly to the second embodiment,
Although only the relief valve and the actuator are shown, the other components are the same as those in the first embodiment, so illustrations and explanations are omitted. Omitted.

The relief valve 60 of the fuel injection pump shown in the same figure is
It consists of a permanent magnet 30 similar to the first embodiment fitted into the plunger 3, and magnetic pole pieces 31a and 31b attached to both end faces of the permanent magnet 30. Along this outer peripheral surface, a moving electrode 64 made of a conductive material such as aluminum and formed in an annular shape with a constant width is provided.

The actuator includes field coils 33a, 33b and a jacket yoke 3 similar to the first embodiment.
6 is formed around the outer periphery of the relief valve 60 in a non-contact manner, and ring-shaped flat plates 61a and 61b made of an insulating material such as ceramic or synthetic resin are fitted into the openings at both ends of the outer cover yoke 36. Further, the two field coils 33a, 3
3b, these field coils 33a, 33
An operating position sensor 6 formed in an annular shape concentric with b
2 is provided.

As shown in FIG. 9, this operating position sensor 62 is formed in the shape of a ring with a constant width and has an inner circumferential surface facing the outer circumferential surface of the movable electrode 64 with a minute gap (for example, several tens to several hundreds of μm) therebetween. , and fixed electrodes 62a, 62 made of a good conductor such as copper, fixed in parallel and spaced apart from each other at equal intervals by an insulating material 63.
b, 62c are formed.

The three fixed electrodes 62a, 62b,
62c, the central fixed electrode 62b is used as a common electrode, the fixed electrode 62a, the moving electrode 60, and the fixed electrode 62b correspond to the capacitor _C1 in the first embodiment, and the fixed electrode 62b, the moving electrode 60, and the fixed electrode 62c are arranged as a common electrode. It is also configured to correspond to capacitor _C2 .

The operating position detection operation of the relief valve 60 and the drive control operation of the actuator in the fuel injection pump configured as described above are carried out in the same manner as in the first embodiment by the control system shown in FIGS. 5 and 6. It is carried out as follows. Therefore, a description of the operation will be omitted.

Therefore, the fuel injection pump of the third embodiment exhibits the same effects as the fuel injection pump of the first embodiment, and as described above, the movable electrode 64 is placed on the outer peripheral surface of the relief valve 60. forming an operating position sensor 62, the inner peripheral surface of which is connected to the moving electrode 64.
By forming the movable electrode 64 and the fixed electrodes 62a, 62b,
62c can be made narrower, thereby increasing the capacitance change accompanying movement of the relief valve 60, and further improving the accuracy of detecting the operating position of the relief valve 60. .

In each of the embodiments described above, the capacitance changes of the capacitors C ₁ and C ₂ constituted by the fixed electrodes of the operating position sensor are detected not only by the AC bridge 44 but also by incorporating the capacitance of the CR oscillator, for example. , convert it into an oscillation frequency change and detect it,
Other means, such as incorporating it into a delay circuit and converting it into a delay time change and detecting it, may be used, and the same effect can be obtained.

Furthermore, in each of the above embodiments, the relief valve is provided with an annular permanent magnet and the movement and position of the relief valve is determined by controlling the excitation current of the two field coils of the actuator. However, it is clear that the operating position of the relief valve can be directly detected by providing an operating position sensor as shown in each of the above embodiments.

As explained in detail below, according to the present invention, the following effects can be obtained.

(1) Since the permanent magnet, which is the drive part of the relief valve, and the moving electrode, which is the detection part, are integrally formed, when mounting it on the fuel injection pump, all you need to do is manage the mounting accuracy on the electromagnetic actuator side.
The accuracy of the movement position of the relief valve can also be guaranteed.

(2) Since the movement and positioning of the relief valve is a non-contact direct acting type and a detection type, good responsiveness can be ensured.

[Brief explanation of drawings]

1A and 1B are diagrams showing the configuration of a conventional fuel injection pump, FIG. 2 is a sectional view showing an embodiment of the fuel injection pump according to the present invention, and FIG. 3 is a sectional view showing the main parts thereof, FIG. 4 is a perspective view showing the external appearance of the operating position sensor of the same embodiment, FIG. 5 is a block diagram showing the electrical control system of the same embodiment, and FIG.
Circuit configuration diagram showing an example of the sensor circuit in the figure, No. 7
The figure is a sectional view showing another embodiment of the present invention, FIG. 8 is a sectional view showing still another embodiment of the invention, and FIG. 9 is an enlarged sectional view showing details of the operating position sensor portion of FIG. 8. It is. 29, 50, 60...Relief valve, 32a, 32
b, 51a, 51b, 64... moving electrode, 34a,
34b, 52a, 52b, 62...Movement position sensor, 43...Sensor circuit, 70...Electromagnetic actuator.

Claims (1)

[Scope of Claims] 1. In a fuel injection pump that controls the amount of fuel injection by adjusting the operating position of a relief valve for releasing residual fuel into a predetermined cavity using an electromagnetic actuator, a permanent seal is attached to the outer circumferential surface of the relief valve. A fuel injection pump characterized in that a magnet and a moving electrode are arranged, and a plurality of fixed electrodes are provided integrally with the electromagnetic actuator and facing the moving electrode.