JPS6343383A - Piezoelectric drive - Google Patents

Abstract

PURPOSE:To ensure the accurate movement of a moving member by simple structure, to improve injection characteristics by using a piezoelectric drive for a fuel injection valve and to enhance the output, fuel cost, etc. of an internal combustion engine by correcting the error of the quantity of expansion and contraction of one part of a piezoelectric element by the piezoelectric element. CONSTITUTION:First and second piezoelectric elements 4, 5 are each installed inside to a piezoelectric actuator 1 for a piezoelectric drive through insulating plates 3. Voltage is generated in electrodes, 6, 8 when the element 4 is distorted from outside, the element 4 is distorted and elongated in the axial direction whch positive voltage is applied to the electrodes 6, 8 inversely, and the element 4 is shrunk when negative voltage is applied. The elements 5 are connected to the elements 4 through insulating plates 14, and an actuator 2 is penetrated to electrodes 18, 20 from the elements 5 through each hermetic seal 22, 24. A piston 28 is arranged to the element 5 through an insulating plate 26, and a cylinder body 30 is supported slidably to the piston 28. The error of one part of the piezoelectric elements is corrected by the piezoelectric element, thus simplifying the constitution of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to a drive device, and more particularly to a piezoelectric drive device using a piezoelectric element.

[Prior Art] Various piezoelectric drive devices that utilize the piezoelectric effect of piezoelectric elements and have high responsiveness have been proposed (for example, Japanese Patent Laid-Open No. 59-183069). The amount of expansion and contraction of the piezoelectric element is small, and therefore the amount of drive of the piezoelectric drive device is also small.Therefore, this amount of drive is generally amplified by a hydraulic means or the like to obtain a required displacement of 1q. Fuel injection valves are known (
For example, JP-A-59-206668>.

[Problems to be Solved by the Invention] However, in these conventional piezoelectric drive devices, since the expansion and contraction ω of the piezoelectric element is amplified and used, changes in the amount of expansion and contraction due to deterioration of the piezoelectric element over time are similarly amplified. Therefore, there was a problem in maintaining and improving the accuracy of the displacement amount. Therefore, when used in a fuel injection valve, the required displacement cannot be achieved due to aging of the piezoelectric element, and therefore the pressure in the pressure chamber cannot rise sufficiently, making it impossible to obtain the required needle lift i. First, there is a problem in that the injection characteristics of the fuel injection valve may deteriorate.

On the other hand, if a pressure chamber is separately provided with a pressure sensor to detect the pressure chamber pressure, there are problems in that the device becomes large and the injection performance decreases due to an increase in cost and an increase in the volume of the pressure chamber.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and to provide a piezoelectric drive device that has a simple structure and can always provide the necessary elasticity.

Structure of the Invention [Means for Solving the Problems] In order to achieve the above object, the present invention has the following structure as a means for solving the problems. That is, the piezoelectric cord M1 made of laminated IA structure is biased by a spring in the direction of expansion and contraction, the movable member M2 moves due to the expansion and contraction of the piezoelectric element M1, and the spring biasing force due to the expansion and contraction of a portion of the piezoelectric cord M1. or a change in the resultant force of the spring biasing force and the external force as the amount of movement of the moving member M2 using the remaining part of the piezoelectric cord M1; a movement amount comparison means M4 for comparing the movement amount with the movement amount; a part of the piezoelectric element M1 is expanded and contracted; the piezoelectric element M1 is further controlled based on the comparison result of the movement amount comparison means M4; This is the configuration of a piezoelectric drive device including a control means M5 that sets the amount of movement to the target amount of movement.

The piezoelectric cord M1 may have a laminated + f4 structure, for example, two piezoelectric elements having a laminated structure may be further stacked so that one is a part of the piezoelectric cord M1 and the other is the remainder of the piezoelectric element M1, Alternatively, a portion of the piezoelectric element M1 and the remaining portion may be alternately laminated.

When the piezoelectric element M1 is further controlled by the control means M5 (the piezoelectric cord M1 to be controlled is, for example, the piezoelectric element M
It may be a part of piezoelectric element M1, or it may be the remainder of piezoelectric element M1, or even a piezoelectric element! All of v11 is also fine.

[Operation] The piezoelectric drive device of the present invention having the above configuration has a control means M
5 expands and contracts a part of the piezoelectric element M1 to move the movable member, and the movement amount detecting means M3 detects the change in the spring biasing force due to the expansion and contraction or the change in the resultant force of the spring biasing force and the external force of the piezoelectric cord M1. The amount of movement of the moving member M2 is detected by the remaining portion, the amount of movement is compared with a predetermined target amount of movement by the amount of movement comparison means M4, and the amount of movement of the piezoelectric element is detected by the control means M5 based on the comparison result of the amount of movement comparison means M4. It further controls M1 and works to make the movement ■ of the moving member M2 the target movement amount.

[Example] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 is a schematic diagram of a piezoelectric drive device that is an embodiment of the present invention. Piezoelectric actuator 1 of this piezoelectric drive device
A first piezoelectric element 4 and a second piezoelectric element 5 are housed in an actuator body 2 with an insulating plate 3 interposed therebetween.

This first piezoelectric element 4 has a laminated structure in which a large number of piezoelectric elements are laminated. From the first piezoelectric element 4, two electrodes 6,
8 is pulled out, and the two electrodes 6 and 8 are inserted through the actuator body 2 through hermetic seals 10 and 12, respectively. An external J is attached to this first piezoelectric cord 4.

When a positive voltage is applied to the two electrodes 6, 8, a voltage is generated between the two electrodes 6, 8, and conversely, when a positive voltage is applied to the two electrodes 6, 8, a strain is generated in the first piezoelectric element 4, causing it to elongate in the axial direction.

Moreover, when a negative voltage is applied, it shrinks (so-called piezoelectric effect).

The second piezoelectric cord 5 is connected to the first piezoelectric element 4 via an insulating plate 14. Two electrodes 18 and 20 are drawn out from the second piezoelectric element 5, and two electrodes 1B and 20 are connected to the actuator body 2 via Hermedic wheels 22 and 24, respectively. This second piezoelectric element 5, like the first piezoelectric element 4, is a laminated structure made of piezoelectric elements having the same outer diameter as the first piezoelectric element 4. Overall, it has a thickness 403.5 times that of the first piezoelectric element. .

A piston 28 is connected to the second piezoelectric element 5 with an insulating plate 26 in between. A cylinder body 30 that movably supports this piston 28 is screwed to the actuator body 2, and the cylinder body 30 is screwed to the actuator body 2.
A disc spring 32 is inserted between the two. This disc spring 3
2, the first piezoelectric element 4 and the second piezoelectric element 4 are connected via screws I to 28.
The piezoelectric element 5 is biased upward in the figure.

Next, the electronic control circuit 50 of the piezoelectric drive device of this embodiment will be explained.

As shown in FIG. 2, the electronic control circuit 50 is a well-known CPU 5.
1. ROM52. The RAM 53 is configured as a central logic operation circuit, and input/output circuits that perform input/output with the outside, in this case, a first piezoelectric element input/output circuit 54, a second piezoelectric element output circuit 55, etc., are interconnected via a common bus 56. It is composed of

The CPU 51 inputs the signal from the first piezoelectric cable 4 via the first piezoelectric element input/output circuit 54 . Further, the value of the spring force when a predetermined deflection is given to the 1 m spring 32, the amount of movement of one eye, etc. are written in the ROM 52 in advance. on the other hand,
Based on these signals and data in the ROM 52 and RAM 53, the CPU 51 outputs a drive signal to the first piezoelectric cable 4 via the first piezoelectric element input/output circuit 54, and outputs a drive signal to the first piezoelectric cable 4 via the second piezoelectric element output circuit 55. A drive signal is output to the two piezoelectric elements 5 to control the amount of movement of the screws 1-28.

Next, the processing carried out in the electronic control circuit 50 described above will be explained with reference to the flowchart shown in FIG.

When this piezoelectric drive device is powered on, it executes a piezoelectric drive device control routine shown in the flowchart of FIG. First, the second piezoelectric element 5 is connected via the second piezoelectric element output circuit 55.
A predetermined voltage corresponding to the target movement m is applied to (step 100). At this time, the second piezoelectric element 5 expands by a predetermined amount in the axial direction according to the applied voltage. The expansion of the second piezoelectric element 5 compresses the disc spring 32, and moves the piston 28 upward in the drawing against the tensile force of the disc spring 32 in the drawing. Along with this, a force acting on the piston 28 according to the amount of compression of the disc spring 32 is applied. The constant plate 26.14° acts on the first piezoelectric element 4 via the second piezoelectric element 5. In response to this acting force, a voltage is generated between the electrodes 6 and 8 of the first piezoelectric element 4 due to the piezoelectric effect of the first piezoelectric element 4, and this voltage is read through the first piezoelectric element input/output circuit 54 (step 110). . next,
From the acting force corresponding to this detected voltage, the ROM5
The amount of deflection of the disk spring 32 is calculated based on the relationship between the deflection of the disk spring 32 and the spring force value stored in step 2. Belleville spring 3
The deflection of the piston 26 is equal to the amount of movement of the piston 26, and this amount of deflection is calculated to determine the amount of movement of the piston 26 (step 120). Next, the movement error amount A is obtained by subtracting the calculated movement amount from the target movement amount (step 130).
).

When this error ff1A is positive (step 14
0), a positive voltage corresponding to the error amount A is applied to the first piezoelectric element 4 via the first piezoelectric element input/output circuit 54, and the first piezoelectric element 4 is expanded to correct the error ■A (step 150
). Further, when the error mA is negative (step 140), a negative voltage corresponding to the error amount Δ is applied to the first piezoelectric cable 4, the first piezoelectric element 4 is reduced, and the error amount A is corrected. (Step 160). On the other hand, when the error ff1A is zero, no voltage is applied to the first piezoelectric cord 4.

When the driving of the first piezoelectric cord 4 and the second piezoelectric element 16 is completed in this way, the voltage applied to the first and second piezoelectric elements 4.5 is removed, and the spring force of the disc spring 32 causes the piston 28 and other At step 170), the present control routine is ended.

In addition, in this control routine 43, the case where the second piezoelectric element 5 is extended and the piston 28 is moved has been explained, but the second piezoelectric element 5 is contracted and the piston 28 is moved upward in the figure, and the amount of movement is Correcting by the first piezoelectric element 4 can also be performed in a similar manner.

As described above, the piezoelectric drive device of this embodiment detects the amount of movement of the piston 28 by the second piezoelectric cable 5 using the first piezoelectric cable 4, and expands and contracts the first piezoelectric cable 4 according to the error ff1A. Correct the amount of movement. Thereby, even if the second piezoelectric element 5 does not expand or contract by a predetermined amount due to some reason, for example due to deterioration over time, and an error occurs in the amount of movement of the piston 28, this movement can be performed by expanding or contracting the first piezoelectric element 4. The amount can be corrected. Therefore, even if an error occurs in the amount of expansion and contraction of the second piezoelectric element 5, the amount of movement of the piston 28 can be maintained accurately. In addition, the amount of expansion and contraction of the second piezoelectric element 5 is not limited.
By detecting the expansion/contraction speed with the first piezoelectric cord 4, the second
It is also possible to control the expansion and contraction speed of the piezoelectric element 5 (see FIG. 5(a)). Furthermore, the amount of expansion and contraction can be controlled by keeping the expansion and contraction speed of the second piezoelectric element 5 constant (see FIG. 5).
b)).

In addition, the detection signal level for the same pressure can be improved by increasing the thickness of the piezoelectric element of the first piezoelectric element 4 (it may be made into a single layer), or the thickness of the piezoelectric element 4 may be made thinner and the number of laminated layers increased to increase the static A configuration may be adopted in which the capacitance is increased to stabilize the signal level and improve the detection accuracy, and the thickness of the piezoelectric unit may be optimized depending on the usage conditions.

Next, a fuel rE+ injection valve to which the piezoelectric drive device of this embodiment is applied will be explained with reference to FIG. 4, which is a sectional view of the fuel injection valve.

The piezoelectric actuator 1 or the attached fuel 1!31
The injection valve is connected to a fuel injection valve main body 150 and has a nozzle hole 9.
52 and a nozzle holder 156 that is mounted on the nozzle 154 and fixes the nozzle 154 to the fuel injection valve main body 150.

In addition, a throttle passage 158 is formed with a predetermined gap in the fuel injection valve main body 150, and a control rod 160 is inserted in the axial direction so as to be able to move in the same direction. Possibly inserted needles 162 are arranged in series.

Furthermore, a spring chamber 1 is formed at the lower end of the fuel injection valve body 150.
A spring 166 that urges the needle 162 downward in the figure is inserted into the spring 64 .
is pressed downward in the figure.

This needle 162 has a conical pressure receiving surface 162a formed in its middle portion, and an oil pool 168 is provided in the nozzle 154 around this pressure receiving surface 162a.

A fuel inlet 170 is provided on the side surface of the fuel injection valve main body 150.
A fuel hole 172 is formed in connection with this fuel inlet 170.

A fuel hole 174 is provided in the nozzle 154, which communicates the fuel hole 172 with the oil pool 168.

Further, the oil reservoir 168 is communicated with the throttle passage 158 by an annular fuel passage 176 and a spring 164 formed around the upper part of the needle 162, and through an annular fuel passage 178 formed around the lower part of the needle 162. and communicates with the nozzle hole 152.

On the other hand, in the piezoelectric drive device, the fuel injection valve is attached to the water body 150 by a connecting nut 180 whose one end is screwed into the cylinder body 30 and the other end is screwed into the fuel injection valve body 150. This connecting nut 180, the cylinder body 30.
A pressure chamber 182 is formed by the piston 28, and
Connection nut 180, fuel injection valve body 150. A back pressure chamber] 84 is formed by the control rod 160, and the pressure chamber 1
A fuel hole 186 is formed in the connecting nut 180, which communicates the fuel hole 82 with the back pressure chamber 184. The cross-sectional area of this pressure chamber 182 is larger than the cross-sectional area of the back pressure chamber 184, so the amount of movement of the piston 28 is amplified and transmitted to the control iron 160.

In the fuel injection valve having the above configuration, fuel pressurized to a predetermined pressure is supplied to the fuel inlet 17 by a fuel supply pump (not shown).
0, fuel is supplied to fuel holes 172.174. Oil pool 168. Fuel passage 176, spring chamber 164. The fuel sequentially passes through the throttle passage 158 and flows into the back pressure chamber 184, and further flows into the pressure chamber 182 via the fuel hole 186.

Next, when a negative voltage is applied to the second piezoelectric element 5, the second piezoelectric element 5 contracts, and the piston 28 moves upward in the figure by the force of the disc spring 32.The amount of movement of the piston 28 is amplified. is transmitted to the control rod 160 and the control rod 16
Move 0 upwards in the diagram.

This control rod 160 moves upward in the figure, and the control rod 1
When the upper end surface of the piezoelectric element 60 comes into contact with the connecting collars 1 to 180, the pressure within the pressure chamber 182 rapidly decreases, and the pressure applied to the first piezoelectric element 4 and the biasing force of the disc spring 32 also decrease rapidly. This sudden drop can be detected by the electronic control circuit 50 to confirm the rise of the control rod 160. At this time, if a sudden drop in pressure is not detected within a predetermined time, it is determined that the second piezoelectric element 5 is not sufficiently reduced and the control rod 160 is not raised sufficiently, and the electronic control circuit 50 causes the first piezoelectric element 4 to A negative voltage is applied to reduce the control rod 160 and further raise the control rod 160.

As the control rod 160 rises, the needle 162 moves downward in the figure against the urging force of the spring 166 due to the fuel pressure acting on the pressure receiving surface 162a, and fuel is injected from the nozzle hole 152.

On the other hand, when a positive voltage is applied to the second piezoelectric element 5, the second piezoelectric element 5 expands, and this amount of expansion is amplified, so that the control rod 1
60. Therefore, the control rod 160 moves downward in the figure, and the needle 162 moves downward in the figure,
Needle 162 and nozzle 154 abut. Due to this contact, the pressure within the pressure chamber 182 rises rapidly, and increases due to the pressure applied to the first piezoelectric element 4 and the biasing force of the II'11 spring 32.

This increase can be detected by the electronic control circuit 50 to confirm the lowering of the control rod 160. At this time, if a sudden increase in pressure is not detected within a predetermined time, the second piezoelectric cord 5
Assuming that the lowering of the control rod 160 is insufficient due to insufficient extension, the electronic control circuit 50 applies a positive voltage to the first piezoelectric element 4 to extend it, and further lower the control rod 160. This lowering brings the needle 162 and nozzle 154 into contact, cutting off fuel injection.

In this way, by applying the piezoelectric control device of this embodiment to a fuel injection valve, it is possible to confirm the movement of the needle 162, and when the amount of movement of the needle 162 by the second piezoelectric element 5 is insufficient, the first piezoelectric Element 4 can correct this. Therefore, it is possible to correct changes in the amount of expansion and contraction of the second piezoelectric element 5 due to deterioration over time, etc., and to reliably perform fuel injection by the fuel injection valve. Furthermore, since the amount of movement can be freely controlled, it is possible to change the injection rate pattern and improve the accuracy in variable injection rate control.

Although the embodiments of the present invention have been described above, the present invention is not equally limited to these embodiments, and may be implemented in various forms without departing from the gist of the present invention.
9, of course.

Effects of the Invention As detailed above, according to the piezoelectric drive device of the present invention,
Since the error in the amount of expansion and contraction of a part of the piezoelectric element is corrected by the piezoelectric element, an excellent effect is achieved in that an accurate amount of movement of the moving member can be ensured with a simple structure. Therefore, for example, when the piezoelectric drive device of the present invention is used in a fuel injection valve, the injection characteristics can be improved, and the output, fuel consumption, noise, emissions, etc. of the internal combustion engine can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram illustrating an embodiment of the present invention, and FIG. 3 is an example of a control routine performed in the control circuit of this embodiment. 4 is a sectional view showing an example of a fuel injection valve to which the present invention is applied; FIG. 5(a) is a graph showing the relationship between the amount of expansion of the piezoelectric element and time using speed as a parameter; b) is a graph showing changes in the amount of elongation of the piezoelectric element over time; 1... Piezoelectric actuator 4... First piezoelectric element 5... Second piezoelectric element 28... Piston 5
0...Electronic control circuit

Claims (1)

[Scope of Claims] A piezoelectric element having a laminated structure that is biased by a spring in an expansion/contraction direction, a moving member that moves due to expansion and contraction of the piezoelectric element, and a change in the biasing force of the spring due to expansion and contraction of a portion of the piezoelectric element, or Movement amount detection means for detecting a change in the resultant force of the spring biasing force and external force as the movement amount of the moving member using the remainder of the piezoelectric element, and movement amount comparison means for comparing the movement amount with a predetermined target movement amount. and control means for expanding and contracting a part of the piezoelectric element, further controlling the piezoelectric element based on the comparison result of the movement amount comparison means, and setting the movement amount of the moving member to the target movement amount. piezoelectric drive device.