JP2010103315A - Piezoelectric actuator and fuel injection valve using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator suppressing an increase in manufacturing cost and increasing detection accuracy; and to provide a fuel injection valve using the same. <P>SOLUTION: The piezoelectric actuator 22 for controlling opening/closing driving of a needle 12 of the fuel injection valve 2 includes a piezoelectric unit 23 formed by laminating piezoelectric element layers 61, 71, 81, and internal electrode layers 62a, 62b, 72a, 72b. The piezoelectric unit 23 includes a drive section 70 extended by application of a voltage and a load sensor section 60 detecting a load generated from the drive section 70. A connection layer 80 is provided between the drive section 70 and the load sensor section 60. Both the polarity of a drive section-side terminal inner electrode layer 73 of the drive section 70 on the side of the load sensor section 60 and the polarity of a sensor section-side terminal inner electrode layer 63 of the load sensor section 60 on the side of the drive section 70 are negative. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric actuator and a fuel injection valve using the piezoelectric actuator.

Piezoelectric layers and internal electrode layers are alternately stacked, and a piezoelectric actuator that expands when a voltage is applied to the piezoelectric layer from the internal electrode layer, and a spacer made of a non-conductive member is interposed at the end of the piezoelectric actuator. There is known a fuel injection valve having a load sensor made of a piezoelectric body provided (see Patent Document 1). In this fuel injection valve, a load from a piezoelectric actuator is detected by a load sensor, and a valve opening signal and a valve closing signal transmitted to the piezoelectric actuator are learned and corrected based on the detection result.
JP-A-10-288119

  However, in the above-described conventional fuel injection valve, although the piezoelectric actuator and the load sensor are integrated in the casing, a spacer made of a non-conductive member is interposed between the actuator and the sensor. Yes. For this reason, the manufacturing cost of the actuator and the sensor has been increased, which is one of the causes for increasing the manufacturing cost of the fuel injection valve.

  If the spacer that is considered to be one of the causes of this increase in manufacturing cost is eliminated and the actuator and the sensor are placed adjacent to each other, the above problem will be solved, but the following new problems will occur. There is a risk. In order to suppress an increase in manufacturing cost, if the spacer is simply removed and the actuator and the sensor are arranged adjacent to each other, an electric leak from the piezoelectric actuator to which a high voltage is applied to the load sensor may occur. is there.

  When an electric leak occurs in the load sensor, an electrical noise is added to a voltage signal generated by the load sensor in accordance with the load from the piezoelectric actuator, resulting in a problem that the detection accuracy of the load sensor is lowered. As a result, since the piezoelectric actuator is to be controlled based on the detection result from the load sensor, there arises a problem that the injection control accuracy is lowered.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a piezoelectric actuator capable of suppressing an increase in manufacturing cost and improving detection accuracy, and a fuel injection valve using the piezoelectric actuator. Is to provide.

The invention according to claim 1 is a piezoelectric actuator having a piezoelectric unit in which a plurality of piezoelectric layers and a plurality of internal electrode layers are laminated, the piezoelectric unit comprising a piezoelectric layer and a piezoelectric layer. A piezoelectric layer including a pair of internal electrode layers sandwiched and distorted in accordance with a voltage applied to the piezoelectric layer via the internal electrode layer, and a pair of internal electrode layers sandwiching the piezoelectric layer and the piezoelectric layer A load sensor unit that outputs a load signal corresponding to a load acting on the internal electrode layer,
When a voltage is applied to the piezoelectric layer of the drive unit, the polarity of the internal electrode layer in the drive unit is such that one internal electrode layer is on the positive side and the other internal electrode layer is on the negative side, and a load is applied to the load sensor unit. The polarity of the internal electrode layer in the load sensor portion when acting is such that one internal electrode layer is on the positive side and the other internal electrode layer is on the negative side,
Of the internal electrode layers in the drive unit, the polarity of the drive unit side terminal internal electrode layer disposed closest to the load sensor unit when a voltage is applied to the drive unit, and the internal electrode layer in the load sensor unit, The polarities of the sensor unit side terminal internal electrode layers arranged closest to the drive unit when a load is applied to the load sensor unit are both negative.

  According to the present invention, a load is applied to the polarity when a voltage is applied to the drive unit of the drive unit side terminal internal electrode layer in the drive unit, and to the load sensor unit of the sensor unit side terminal internal electrode layer of the load sensor unit. Since both of the polarities are negative, the potential difference between both terminal internal electrode layers becomes very small. Since the potential difference between both terminal internal electrode layers becomes very small, even if a high voltage is applied to the internal electrode layer including the drive unit side internal electrode layer in order to extend the piezoelectric layer of the drive unit, a load is applied from the drive unit. Electric leakage to the sensor unit can be suppressed. Since electric leakage to the load sensor can be suppressed, the problem of electrical noise on the load signal corresponding to the load taken from the internal electrode layer of the load sensor can be solved, improving the detection accuracy of the load sensor it can.

  In addition, since electric leakage to the load sensor unit can be suppressed, it is not necessary to provide an insulating layer such as a spacer between the load sensor unit and the drive unit, or the insulating layer can be made very thin. An increase in manufacturing cost of the piezoelectric actuator can be suppressed.

  Therefore, by setting the polarities of both terminal internal electrode layers to the negative side, it is possible to provide a piezoelectric actuator capable of suppressing an increase in manufacturing cost and improving detection accuracy in the load sensor unit.

  In addition, “the polarity of the internal electrode layer is negative side” described in the claims means that, in the drive unit, the internal part of the pair of internal electrode layers when the voltage is applied to the drive unit is on the low potential side. It means an electrode layer, and in the load sensor part, it means an internal electrode layer on the side having a lower potential among a pair of internal electrode layers when a load acts on the load sensor part. Therefore, the method of grounding the internal electrode layer whose polarity is on the negative side is not limited.

  According to the second aspect of the present invention, a connection layer is disposed between the sensor unit termination internal electrode layer and the drive unit termination internal electrode layer, and the connection layer is a piezoelectric layer, and the piezoelectric body in the load sensor unit It is characterized by being thicker than the layer or the piezoelectric layer in the driving unit.

  According to the present invention, the connection layer disposed between both terminal internal electrode layers is a piezoelectric layer, and the piezoelectric layer is thicker than the piezoelectric layer in the load sensor unit or the piezoelectric layer in the drive unit. ing. For this reason, the insulation between a load sensor part and a drive part can be made more reliable, and the detection accuracy of a load sensor part can be improved. The thickness of the piezoelectric layer refers to the distance between the surfaces of the internal electrode layers facing each other.

  According to a third aspect of the present invention, a connection layer is disposed between the sensor unit termination internal electrode layer and the drive unit termination internal electrode layer, and the connection layer is formed by alternately laminating piezoelectric layers and internal electrode layers. It is characterized by having.

  According to the present invention, since the connection layer disposed between both terminal internal electrode layers is formed by alternately laminating the piezoelectric layers and the internal electrode layers, the load sensor unit and the drive are provided to increase the insulation of the connection layer. Even if the structure is different from the piezoelectric layer used for the part (for example, the structure is thicker than other piezoelectric layers), the thickness of the connection layer should be increased to increase the insulation. Can do. Further, since the piezoelectric layers and the internal electrode layers are alternately laminated, the laminated structure of the load sensor unit and the driving unit can be made the same.

  According to this, when the piezoelectric body unit is formed as an integral laminated type, the connection layer can also be fired in the same environment as the load sensor unit and the drive unit. For this reason, the state of the connection layer after baking can be made the same as that of the load sensor part and the drive part. When the internal electrode layer has a function as a sintering aid, the mechanical strength of the connection layer can be ensured, and the quality of the piezoelectric unit can be improved. In addition, since the types of thicknesses of the piezoelectric layers constituting the piezoelectric unit can be reduced, an increase in manufacturing cost can be suppressed.

  And the shrinkage | contraction rate at the time of baking differs with the piezoelectric material layer containing an internal electrode layer, and the piezoelectric material layer which does not contain an internal electrode layer. According to the present invention, firing shrinkage between the connection layer, the load sensor unit, and the drive unit can be matched. As a result, peeling, cracking, and the like after firing of the piezoelectric body unit due to mismatching firing shrinkage can be avoided.

  The drive unit side termination internal electrode layer and the termination piezoelectric layer disposed adjacent to the drive unit side termination internal electrode layer on the side opposite to the load sensor unit are provided in the drive unit. It is characterized by being thicker than other piezoelectric layers.

  According to the present invention, the terminal piezoelectric layer disposed adjacent to the side opposite to the load sensor portion of the drive unit side terminal internal electrode layer is thicker than the other piezoelectric layers in the drive unit. The shear stress generated at the end of the drive unit when the drive unit is expanded and contracted can be alleviated.

  According to a fifth aspect of the present invention, the piezoelectric unit includes the piezoelectric layer and the internal electrode layer that constitute the load sensor unit, and the piezoelectric layer and the internal electrode layer that constitute the drive unit. It is characterized by being a laminated fired body.

  The configuration of the piezoelectric unit is roughly divided into two forms. One is a single plate laminate type, and the other is an integral laminate type. A single-plate laminated piezoelectric unit is obtained by laminating a previously fired piezoelectric layer with an internal electrode layer printed and fired, and an integrally laminated piezoelectric unit is a piezoelectric layer (green sheet). In addition, a substrate printed with an internal electrode layer is laminated in advance, and then fired to integrate the piezoelectric layer and the internal electrode layer. The “laminated fired body” described in the claims means an integrally laminated type.

  In a single-plate stacked piezoelectric unit, generally, a conductor (for example, a metal foil such as stainless steel or copper) that electrically connects the internal electrode layer and the outside is disposed between the piezoelectric layers. Yes.

  When the load sensor unit and the drive unit are formed in a single-plate stacked piezoelectric unit, the conductor deforms when the load sensor unit detects the load when the drive unit is extended. For this reason, force transmission loss occurs, and the detection accuracy of the load sensor unit may be reduced. In addition, since the deformation of the conductor changes depending on the usage situation, even if a predetermined voltage is applied to the drive unit to extend a predetermined amount, the detection result of the load sensor unit changes and the detection accuracy decreases.

  On the other hand, according to the present invention, since the piezoelectric unit is a laminated fired body, the internal electrode layer can be easily exposed on the side wall of the piezoelectric layer by grinding or the like. For this reason, there is no need to sandwich the conductor between the piezoelectric layers. As a result, the loss of force transmitted from the drive unit to the load sensor unit can be suppressed, and the detection accuracy of the load sensor unit is improved as compared with the single plate laminated type.

  When the piezoelectric layer is used as an actuator, in order to increase the extension amount of the drive unit as much as possible, it is preferable to form a thin piezoelectric layer per layer and to stack a plurality of them. However, when the drive unit and the load sensor unit are formed as a single laminated fired body with a piezoelectric layer made as thin as possible, when the drive unit is extended, stress is concentrated near the side surface of the drive unit, and the stress is concentrated. There is a risk of damage. This phenomenon becomes more prominent as the number of stacked piezoelectric layers in the driving unit increases.

  According to the sixth aspect of the present invention, the piezoelectric unit includes a piezoelectric layer and an internal electrode layer that constitute the load sensor portion, and a laminated firing that includes the piezoelectric layer and the internal electrode layer that constitute a part of the driving portion. The drive unit is extended by being composed of a piezoelectric unit with a sensor unit, which is a body, and a drive unit piezoelectric unit, which is a laminated fired body having a piezoelectric layer and an internal electrode layer that constitute the other part of the drive unit It is possible to reduce the degree of stress concentrated near the side surface. For this reason, the quality of the piezoelectric body unit can be improved.

  According to a seventh aspect of the present invention, the piezoelectric unit includes a sensor unit piezoelectric unit that is a laminated fired body having a piezoelectric layer and an internal electrode layer that constitute a load sensor unit, a piezoelectric layer that constitutes a drive unit, and The drive unit piezoelectric unit is a laminated fired body having an internal electrode layer.

  According to the present invention, it is not necessary to separate the specifications of the sensor unit piezoelectric unit and the drive unit piezoelectric unit, compared to the case where the load sensor unit and the drive unit are provided in one unit, can do. For this reason, the piezoelectric actuator which has a load sensor part at low cost can be manufactured.

  The invention according to claim 8 is characterized in that the load sensor portion is formed at one end of the piezoelectric unit.

  According to this invention, since the load sensor unit is formed at one end of the piezoelectric body unit, the wiring connected to the internal electrode layer of the load sensor unit and the wiring connected to the internal electrode layer of the drive unit Can be simplified as much as possible. Moreover, since the load sensor part is formed in any one edge part of a piezoelectric body unit, it is hard to receive the influence (disturbances, such as tensile force and heat_generation | fever by expansion) of a drive part.

  According to a ninth aspect of the present invention, there is provided an injection hole through which fuel is injected, a body having a high-pressure fuel passage for supplying high-pressure fuel to the injection hole, and the intermittent connection between the injection hole and the high-pressure fuel passage. A valve member, a high pressure fuel passage that communicates with the high pressure fuel passage and that acts on the valve member to generate a force in the valve opening direction; A second hydraulic chamber for storing high-pressure fuel from the high-pressure fuel passage that generates force in the valve closing direction by acting on the member; and either the first hydraulic chamber or the second hydraulic chamber housed in the body A control valve that controls the fuel pressure, the piezoelectric actuator according to any one of claims 1 to 8, and a displacement transmission unit that transmits a displacement of the piezoelectric actuator to the control valve.

  According to the present invention, the driving state of the control valve can be accurately grasped by using the piezoelectric actuator according to any one of claims 1 to 8 as the actuator that drives the control valve via the displacement transmission unit. Since the drive state of the control valve can be accurately grasped, the drive state of the valve member that is driven in accordance with the operation of the control valve can be accurately grasped. As a result, the fuel injection accuracy of the fuel injection valve can be improved.

  According to a tenth aspect of the present invention, there is provided an injection hole through which fuel is injected, a body having a high-pressure fuel passage for supplying high-pressure fuel to the injection hole, and the injection hole and the high-pressure fuel passage accommodated in the body. And a first hydraulic chamber for storing high-pressure fuel from the high-pressure fuel passage that communicates with the high-pressure fuel passage and generates a force in the valve opening direction by acting on the valve member. A second hydraulic pressure chamber for storing high-pressure fuel from the high-pressure fuel passage that communicates with the high-pressure fuel passage and generates a force in the valve closing direction by acting on the valve member; The cylinder which controls the fuel pressure by changing the volume of either or both of the first hydraulic pressure chamber and the second hydraulic pressure chamber, and the cylinder is directly driven. Piezoelectric actuator as described in It is characterized in that it comprises mediator and, a.

  According to the present invention, the actuator is configured to change the volume of one or both of the first hydraulic pressure chamber and the second hydraulic pressure chamber by moving and to directly drive the cylinder for controlling the fuel pressure. By using the piezoelectric actuator described in the above, it is possible to accurately grasp the driving state of the valve member. As a result, the fuel injection accuracy of the fuel injection valve can be improved.

  According to an eleventh aspect of the present invention, the body is formed with an actuator chamber that accommodates the piezoelectric actuator according to any one of the first to eighth aspects, and the piezoelectric actuator is opposite to the hydraulic pressure adjusting mechanism. The load sensor portion is housed in the actuator chamber so that the load sensor portion is positioned on the fixed end side of the actuator chamber located on the side.

  In this invention, the piezoelectric actuator is accommodated in the actuator chamber so that the load sensor portion is positioned on the fixed end side of the actuator chamber located on the opposite side of the hydraulic pressure adjusting mechanism. Compared with the case where it is arranged on the adjustment mechanism side, transmission loss of the load generated by the drive unit can be suppressed, and the drive state of the hydraulic pressure adjustment mechanism or the valve member can be accurately grasped.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, the overlapping description is abbreviate | omitted by attaching | subjecting the same code | symbol to the component corresponding in each embodiment.

(First embodiment)
Hereinafter, the case where the piezoelectric actuator 22 of the present invention is applied to the fuel injection valve 2 will be described as an example. FIG. 1 is a cross-sectional view showing the overall configuration of a fuel supply device 1 including a fuel injection valve 2 according to a first embodiment of the present invention. The fuel supply device 1 supplies fuel to each cylinder of a multi-cylinder internal combustion engine such as a diesel engine. The fuel handled by the fuel supply device 1 is not limited to diesel fuel, and may be gasoline fuel.

  The fuel supply device 1 includes a fuel injection valve 2, a drive circuit 3, an electronic control device 4 (hereinafter referred to as ECU), and the like. The fuel injection valve 2 is mounted on a cylinder head of a multi-cylinder internal combustion engine. The fuel injection valve 2 directly injects fuel into each cylinder using high-pressure fuel stored in a pressure accumulator (not shown). Of the fuel supplied to the fuel injection valve 2, the fuel not used for fuel injection is returned to the fuel tank 10 through the return path 8.

  The fuel injection valve 2 includes a nozzle 11, a control valve 18, an actuator unit 21, and the like, and these components are accommodated in a body 40 formed in a rod shape.

  The body 40 has a fuel inlet 41 into which high-pressure fuel from the pressure accumulator is introduced, and a fuel outlet 42 connected to the return path 8. A housing portion 43 is formed at one end of the body 40 in the axial direction, and the housing portion 43 houses a nozzle 11 that controls fuel injection and non-injection. The accommodating portion 43 corresponds to a “first hydraulic chamber” described in the claims.

  The nozzle 11 has a needle 12, a nozzle spring 16, and a nozzle cylinder 17. The needle 12 is slidably held in the housing portion 43. A nozzle hole 44 that communicates with the fuel inlet 41 via a high-pressure fuel passage 46 is formed at one axial end of the housing 43.

  A valve seat 45 on which the seat portion 13 formed on the needle 12 is seated is formed on the fuel inlet portion 41 side of the nozzle hole 44. When the seat 13 is seated on the valve seat 45, the flow of fuel to the nozzle hole 44 is closed, and the fuel injection from the nozzle hole 44 is stopped. When the seat portion 13 is separated from the valve seat 45, the flow of fuel to the nozzle hole 44 is allowed, and fuel is injected from the nozzle hole 44.

  The nozzle cylinder 17 is formed in a cylindrical shape, and a piston portion 14 formed at an end portion of the needle 12 opposite to the seat portion 13 is slidably and liquid-tightly inserted on the inner peripheral side. is doing. The nozzle cylinder 17 forms a control chamber 52 in which the internal fuel pressure is switched between high pressure and low pressure together with the piston portion 14 and the inner wall of the accommodating portion 43. The control chamber 52 corresponds to a “second hydraulic chamber” described in the claims.

  A flange portion 15 is formed between the seat portion 13 and the piston portion 14 of the needle 12, and a nozzle spring 16 is provided between the flange portion 15 and the nozzle cylinder 17. The nozzle spring 16 urges the needle 12 in the direction in which the seat portion 13 is seated on the valve seat 45, that is, in the valve closing direction.

  The needle 12 is urged in the valve closing direction by the fuel pressure in the control chamber 52. Further, the needle 12 is urged in a direction in which the seat portion 13 is separated from the valve seat 45, that is, in a valve opening direction, by the high pressure fuel guided from the fuel inlet portion 41 to the accommodating portion 43 through the high pressure fuel passage 46. The movement of the needle 12 in the valve closing direction or the valve opening direction is determined by the balance of the fuel pressure in the control chamber 52, the fuel pressure of the high-pressure fuel guided to the housing portion 43, and the urging force of the nozzle spring 16.

  The control valve 18 is housed in a valve chamber 53 formed in the intermediate portion of the body 40 in the axial direction, and performs switching control between high pressure and low pressure of the fuel pressure in the control chamber 52. The valve chamber 53 is connected to a communication passage 50 that always communicates with the control chamber 52, a high-pressure communication passage 47 that branches off from the housing portion 43, and a low-pressure fuel passage 48. A common orifice 51 is provided in the communication passage 50.

  The control valve 18 includes a valve body 19 and a valve spring 20. The valve body 19 communicates between the valve chamber 53 and the low-pressure fuel passage 48 by separating from and seating on the low-pressure side seat surface 54 formed around the opening of the low-pressure fuel passage 48 in the inner wall of the valve chamber 53. Control the shut-off. Further, the valve element 19 is separated from and seated on the high-pressure side seat surface 55 formed around the opening of the high-pressure communication passage 47 in the inner wall of the valve chamber 53, so that the valve body 19 is located between the valve chamber 53 and the high-pressure communication passage 47. Controls communication and disconnection. The valve body 19 is separated from the high-pressure side seat surface 55 when seated on the low-pressure side seat surface 54, and conversely when the seat 19 is separated from the low-pressure side seat surface 54. Sitting at 55. The valve spring 20 urges the valve body 19 in a direction to be seated on the low pressure side seat surface 54.

  The actuator portion 21 is accommodated in an actuator chamber 56 formed on the other end side of the body 40 in the axial direction. The actuator chamber 56 is connected to the low pressure fuel passage 48 via the low pressure communication passage 49.

  A back pressure valve 9 for controlling the pressure on the low pressure fuel passage 48 side is disposed in the return path 8 that connects the fuel tank 10 and the fuel outlet 42. Whereas the pressure of the high pressure fuel stored in the pressure accumulator is 100 MPa or more, the back pressure valve 9 controls the fuel pressure on the low pressure fuel passage 48 side to about 1 MPa.

  The actuator unit 21 includes a piezoelectric actuator 22 and a displacement transmission unit 30. The piezoelectric actuator 22 is mainly configured by stacking a plurality of piezoelectric layers, and expands and contracts due to charge and discharge. The structure of the piezoelectric actuator 22 will be described in detail later.

  The displacement transmission unit 30 transmits the expansion / contraction displacement of the piezoelectric actuator 22 to the valve body 19 of the control valve 18. The displacement transmission unit 30 includes an actuator cylinder 31, a first piston 32, and a second piston 33. The first piston 32 and the second piston 33 are slidably and liquid-tightly inserted on the inner peripheral side of the actuator cylinder 31. A liquid chamber 34 filled with fuel is formed between the first piston 32 and the second piston 33.

  The first piston 32 is biased toward the piezoelectric actuator 22 by the first spring 35. The first piston 32 is directly driven by the piezoelectric actuator 22. When the piezoelectric actuator 22 is extended, the first piston 32 moves toward the liquid chamber 34, so that the fuel pressure in the liquid chamber 34 increases.

  The second piston 33 is urged toward the valve body 19 side of the control valve 18 by the second spring 36. The second piston 33 is mechanically connected to the valve body 19, and the second piston 33 receives the fuel pressure in the liquid chamber 34 and moves toward the valve body 19 to move the valve body 19 to the valve chamber. 53 and the low-pressure fuel passage 48 are moved in a communication direction.

  When the piezoelectric actuator 22 is extended, the first piston 32 moves in the direction of the liquid chamber 34. Then, the fuel pressure in the liquid chamber 34 increases. The second piston 33 receives the increased fuel pressure in the liquid chamber 34, communicates the valve body 19 between the valve chamber 53 and the low pressure fuel passage 48, and connects the valve chamber 53 and the high pressure communication passage 47. Move in the direction that cuts off the communication between them.

  When the piezoelectric actuator 22 contracts, the fuel pressure in the liquid chamber 34 decreases. The second piston 33 moves to the first piston 32 side by the urging force of the valve spring 20 of the control valve 18. The urging force of the valve spring 20 is larger than the urging force of the second spring 36. As a result, the valve body 19 blocks communication between the valve chamber 53 and the low-pressure fuel passage 48 and moves in a direction to communicate between the valve chamber 53 and the high-pressure communication passage 47.

  The piezoelectric actuator 22 includes a piezoelectric unit 23 and a metal housing 24. The piezoelectric unit 23 is formed by laminating a piezoelectric layer (hereinafter referred to as a piezoelectric element layer) P and an internal electrode layer E, and applies a voltage to the piezoelectric element layer P through the internal electrode layer E. And a load sensor unit 60 that outputs a load signal corresponding to a load acting upon extension through the internal electrode layer E. The load sensor unit 60 utilizes the piezoelectric effect of the piezo element layer P. In the present embodiment, the load signal output from the internal electrode layer E of the load sensor unit 60 is a charge and voltage signal corresponding to the load.

  The piezoelectric actuator 22 is connected to the drive circuit 3. The drive circuit 3 supplies a charging current to the drive unit 70 of the piezoelectric actuator 22 to increase the piezoelectric voltage of the drive unit 70. The extension amount of the drive unit 70 changes according to the piezo voltage. An ECU 4 is connected to the drive circuit 3. The ECU 4 generates a charge control signal corresponding to the piezoelectric voltage supplied to the drive unit 70 and the energization timing based on various information, and transmits it to the drive unit 70 as a command signal.

  Further, the load sensor unit 60 is connected to the drive circuit 3. The charge and voltage signals from the load sensor unit 60 are input to the ECU 4 via the drive circuit 3. The ECU 4 is also connected to various sensors (not shown) for detecting the intake air amount, accelerator pedal depression amount, internal combustion engine speed, fuel pressure in the accumulator, and the like, and signals from these various sensors are input. It is like that.

  In the present embodiment, a multi-switching method (hereinafter referred to as an MS method) is adopted as a method for charging and discharging the drive unit 70 of the piezoelectric actuator 22.

  The drive circuit 3 includes a switching element (not shown) capable of directly disconnecting the DC power supply in a path for energizing the piezoelectric actuator 22 from a DC power supply (not shown) via an inductor (not shown). Yes. In the MS system, the drive unit 70 of the piezoelectric actuator 22 is charged in several times by turning the switching element on / off a plurality of times based on a charge control signal from the ECU 4.

  While the switching element is on, a charging current that gradually increases flows to the drive unit 70. When the switching element is turned off, a charging current that gradually decreases to the drive unit 70 by the flywheel action flows. Thus, while the charging current flows through the drive unit 70, the piezoelectric voltage in the piezoelectric element layer P of the drive unit 70 continues to increase. The detailed driving method and circuit configuration of the MS method are well known, for example, in Japanese Patent Laid-Open No. 2001-53348.

  The ECU 4 includes an MPU 5, an AD conversion unit 6, a DSP 7, and the like. The ECU 4 includes a ROM, an EEPROM, a RAM, and the like (not shown). The MPU 5 performs arithmetic processing according to a program stored in the ROM. The ECU 4 calculates a load acting when the drive unit 70 extends by performing high-speed A / D processing on the charge and voltage signals input from the load sensor unit 60 in the AD conversion unit 6, and calculates the calculated load. In addition, based on signals input from various sensors, a charging control signal to be given to the driving unit 70 is generated.

  Next, the operation of the fuel supply device 1 will be described. When the drive unit 70 of the piezoelectric actuator 22 is not extended, the second piston 33 is moved to the first piston 32 side by the biasing force of the valve spring 20 of the control valve 18. As a result, the valve body 19 receives the fuel pressure in the valve chamber 53, moves in the direction of the low pressure fuel passage 48 and is seated on the low pressure side seat surface 54, and the communication between the valve chamber 53 and the low pressure fuel passage 48 is established. The valve chamber 53 and the high-pressure communication passage 47 are communicated with each other. Thereby, the fuel pressure in the valve chamber 53 becomes equal to the fuel pressure in the high pressure fuel passage 46, and the fuel pressure in the control chamber 52 communicating with the valve chamber 53 becomes equal to the fuel pressure in the high pressure fuel passage 46. .

  At this time, the force in the valve opening direction generated in the needle 12 due to the fuel pressure in the high-pressure fuel passage 46 acting around the needle 12 is due to the fuel pressure in the control chamber 52 acting on the piston portion 14 of the needle 12. It is smaller than the sum of the force in the valve closing direction generated at the needle 12 and the force in the valve closing direction generated at the needle 12 due to the urging force of the nozzle spring 16. Therefore, the seat portion 13 of the needle 12 is seated on the valve seat 45, and fuel injection from the injection hole 44 is stopped.

  When the drive unit 70 of the piezoelectric actuator 22 is extended by a command from the ECU 4, the first piston 32 moves toward the liquid chamber 34 as the drive unit 70 is extended. Then, the fuel pressure in the liquid chamber 34 increases. The second piston 33 receives the increased fuel pressure and moves toward the valve body 19 side. The valve body 19 moves in the direction of the high-pressure communication passage 47 and is seated on the high-pressure side seat surface 55, and communicates between the valve chamber 53 and the low-pressure fuel passage 48, and between the valve chamber 53 and the high-pressure communication passage 47. Block communication between them. Then, the fuel in the control chamber 52 is returned to the fuel tank 10 via the common orifice 51, the communication passage 50, the valve chamber 53, and the low pressure fuel passage 48. As a result, the fuel pressure in the control chamber 52 decreases.

  At this time, the force in the valve opening direction generated in the needle 12 due to the fuel pressure in the high-pressure fuel passage 46 acting around the needle 12 is due to the fuel pressure in the control chamber 52 acting on the piston portion 14 of the needle 12. It is larger than the sum of the force in the valve closing direction and the force in the valve closing direction due to the urging force of the nozzle spring 16. Therefore, the seat portion 13 of the needle 12 is separated from the valve seat 45, and fuel is injected from the injection hole 44.

  Thereafter, when the drive unit 70 contracts again, the second piston 33 moves to the first piston 32 side by the urging force of the valve spring 20 as the drive unit 70 contracts. As a result, the valve body 19 is seated on the low pressure side seat surface 54, shuts off communication between the valve chamber 53 and the low pressure fuel passage 48, and communicates between the valve chamber 53 and the high pressure communication passage 47. As a result, the high pressure fuel from the pressure accumulator is introduced into the control chamber 52 via the high pressure fuel passage 46, the high pressure communication passage 47, the valve chamber 53, the communication passage 50, and the common orifice 51.

  Thereby, the fuel pressure in the control chamber 52 rises again. Therefore, the force in the valve opening direction generated at the needle 12 is smaller than the force in the valve closing direction generated at the needle 12, and the seat portion 13 of the needle 12 is seated on the valve seat 45. As a result, fuel injection from the nozzle hole 44 is stopped. By repeatedly expanding and contracting the piezoelectric actuator 22, fuel injection from the injection hole 44 is interrupted.

  Next, control when the piezoelectric actuator 22 of the fuel supply device 1 is driven will be described with reference to FIGS. FIG. 2 is a flowchart showing a control process executed by the ECU 4. FIG. 3 is a time chart showing an operation example when the control process is performed.

  The process shown in FIG. 2 is started when an injection permission signal for allowing fuel to be injected from the fuel injection valve 2 is turned on. The injection permission signal is generated by the ECU 4 based on signals from various sensors input to the ECU 4.

  As shown in FIG. 2, when the injection permission signal is turned on, in step S10 (hereinafter simply referred to as S10, the same applies to other steps), a charge control signal for controlling the operation of the drive circuit 3 is driven. Output to circuit 3.

  While the charge control signal is on, the aforementioned switching element is turned on and a charging current that gradually increases flows to the drive unit 70. When the charge control signal is turned off, the switching element is turned off and the drive unit is operated by the flywheel action. A charging current that gradually decreases to 70 flows. As a result, the piezo voltage continues to increase.

  In S <b> 20, the load generated by the drive unit 70 (hereinafter referred to as a piezo load) at the first time Ta and the second time Tb is detected from the charge and voltage signals acquired from the load sensor unit 60.

  Here, a time T0 in FIG. 3 is a time when the supply of the charging current from the drive circuit 3 to the drive unit 70 is started. Hereinafter, the time T0 is referred to as a charging start time. The first time Ta is when a predetermined time has elapsed from the charging start time T0, and is preset in the vicinity of the timing at which the valve body 19 is separated from the low-pressure side seat surface 54. This first time Ta is stored in the ROM of the ECU 4. In the present embodiment, the piezo load Fa detected at the first time Ta is referred to as a first time load Fa.

  The second time Tb is a time when a predetermined time has elapsed from the first time Ta, and is set in advance at a timing immediately before the valve body 19 is seated on the high-pressure side seat surface 55. This second time Tb is stored in the ROM of the ECU 4. In the present embodiment, the piezo load Fb detected at the second time Tb is referred to as a second time load Fb.

  In S <b> 30, the first time load Fa and the second time load Fb are compared to determine whether or not the valve body 19 is separated from the low-pressure side seat surface 54.

  Here, in a state where the valve body 19 is seated on the low pressure side seat surface 54, the valve body 19 is urged toward the low pressure side seat surface 54 due to a pressure difference between the valve chamber 53 and the low pressure fuel passage 48. On the other hand, when the valve body 19 is not seated on either the low-pressure side seat surface 54 or the high-pressure side seat surface 55, no force is generated to bias the valve body 19 toward the low-pressure side seat surface 54 due to the pressure difference. . Therefore, if Fa> Fb, that is, if the determination in S30 is YES, it is determined that the valve body 19 is operating normally, and the process proceeds to S40.

  In S <b> 40, a timing Tc (hereinafter referred to as a high pressure side closing time) at which the valve body 19 is seated on the high pressure side seat surface 55 and the communication between the valve chamber 53 and the high pressure communication passage 47 is cut off is detected. Specifically, when the valve body 19 is seated on the high-pressure side seat surface 55, the piezo load increases. Therefore, when the piezo load reaches the threshold value Fc after the second time Tb, the valve body 19 moves to the high-pressure side seat surface 55. It is estimated that the communication between the valve chamber 53 and the high-pressure communication passage 47 is blocked.

  In a state where the valve body 19 is seated on the high pressure side seat surface 55, the valve body 19 is urged in a direction away from the high pressure side seat surface 55 by the fuel pressure from the high pressure communication passage 47, so In order to reliably block communication with the communication passage 47, it is necessary to press the valve body 19 against the high-pressure side seat surface 55 with a larger force as the fuel pressure increases.

  Therefore, the threshold value Fc is increased as the fuel pressure in the accumulator increases. Thereby, the timing at which the valve body 19 substantially cuts off the communication between the valve chamber 53 and the high-pressure communication passage 47 can be accurately detected. A map defining the relationship between the threshold value Fc and the pressure accumulator is stored in the ROM of the ECU 4.

  In S50, a time ΔT (hereinafter referred to as a control valve response time) from when charging of the drive unit 70 is started until the valve body 19 blocks communication between the valve chamber 53 and the high-pressure communication passage 47 is calculated. . Specifically, the control valve response time ΔT is the time from the charging start time T0 to the high-pressure side closing time Tc (ΔT = Tc−T0).

  In S60, it is determined whether or not the control valve response time ΔT is within a predetermined allowable range (ΔTmin ≦ ΔT ≦ ΔTmax). ΔTmin is an allowable minimum value of the control valve response time ΔT that can be corrected, and ΔTmax is an allowable maximum value of the control response time ΔT that can be corrected.

  In the present embodiment, the control valve response time ΔT is made to coincide with the target control valve response time ΔTp by appropriately correcting the increase speed Vc of the piezo voltage (hereinafter referred to as the charging speed Vc).

  If the control valve response time ΔT is within the allowable range, that is, if the determination in S60 is YES, the process proceeds to S70.

  In S70, the charging speed Vc at the next injection and the charge control signal at the next injection are calculated. Specifically, the charging speed Vc at the next injection is calculated based on the target control valve response time ΔTp at the next injection so that the control valve response time ΔT matches the target control valve response time ΔTp. Further, a corrected charge control signal for realizing the charging speed Vc at the next injection is calculated.

  When the target control valve response time ΔTp at the next injection is shorter than the control valve response time ΔT at the current injection, the charging speed Vc at the next injection is increased. Specifically, as indicated by the alternate long and short dash line, the on-time of the first charge control signal at the next injection is lengthened, and the period during which the gradually increasing charging current flows to the drive unit 70 is lengthened. At this time, the on-time of the second and subsequent charge control signals at the next injection is shortened so that the total charge energy amount at the next injection becomes equal to the total charge energy amount at the current injection.

  On the other hand, when the target control valve response time ΔTp at the next injection is longer than the control valve response time ΔT at the current injection, the on-time of the first charge control signal at the next injection is shortened to charge at the next injection Reduce the speed Vc. The charging speed Vc is calculated by an arithmetic expression stored in the ROM of the ECU 4. A map defining the relationship between the charging speed Vc and the charging control signal is stored in the ROM of the ECU 4. The ECU 4 calculates a charge control signal corresponding to the charging speed Vc at the next injection using the map.

  In S80, after the charging of the drive unit 70 is completed, a piezo load F1 (hereinafter referred to as a post-charge load F1) at the third time Td when the piezo load is stabilized is measured. The third time Td is stored in the ROM of the ECU 4.

  In S90, a load error ΔF (ΔF = F1−F0) between the post-charge load F1 and the target post-charge load F0 is calculated. The target post-charge load F0 is stored in the ROM of the ECU 4.

  In S100, it is determined whether or not the load error ΔF is within a predetermined range (ΔFmin ≦ ΔF ≦ ΔFmax). ΔFmin is an allowable minimum value of the load error ΔF, and ΔFmax is an allowable maximum value of the load error ΔF. In the present embodiment, the post-charge load F1 is set to an appropriate magnitude by further correcting the charge control signal obtained in S70 and appropriately correcting the charge energy amount.

  When the load error ΔF is within the predetermined range, that is, when the post-charge load F1 is within the allowable load range (S100 is YES), the process proceeds to S110. In S110, the current charging energy amount E0 is held, and the charging energy amount E1 at the next injection is set to E0. Therefore, the charge control signal calculated in S70 is not corrected, and the post-charge load F1 at the next injection does not change.

  On the other hand, if the load error ΔF is not within the predetermined range in S100, that is, if the determination in S100 is NO, the process proceeds to S120. In S120, a charging energy correction value ΔE that is a function of the load error ΔF is calculated based on the load error ΔF. A map defining the relationship between the load error ΔF and the charging energy correction value ΔE is stored in the ROM of the ECU 4. The ECU 4 calculates the charging energy correction value ΔE using this defined map.

  In S130, it is determined whether or not the charge energy correction value ΔE is within a predetermined range (ΔEmin ≦ ΔE ≦ ΔEmax). ΔEmin is an allowable minimum value of the charging energy correction value ΔE, and ΔEmax is an allowable maximum value of the charging energy correction value ΔE. ΔEmin and ΔEmax are stored in the ROM of the ECU 4.

  If the charging energy correction value ΔE is within the range, that is, if the determination in S130 is YES, the process proceeds to S140.

  In S140, a charge energy amount E1 at the next injection and a charge control signal (corrected charge control signal) at the next injection are calculated.

  Specifically, a value obtained by adding the charging energy correction value ΔE to the charging energy amount E0 at the current injection is set as the charging energy amount E1 at the next injection. Further, in order to realize the charging energy amount E1 at the next injection, the charging control signal calculated in S70 is further corrected.

  For example, when the charge energy correction value ΔE is positive, the on-time of the last charge control signal in the charge control signal calculated in S70 is lengthened. When the charge energy correction value ΔE is negative, the on-time of the last charge control signal in the charge control signal calculated in S70 is shortened.

  A map defining the relationship between the charging energy amount E1 at the next injection and the correction amount of the charging control signal is stored in the ROM of the ECU 4. The ECU 4 calculates the correction amount of the charge control signal using this defined map.

  In the next S10, the charge control signal calculated in S70 or the charge control signal further corrected in S140 is output to the drive circuit 3.

  By controlling the charging of the drive unit 70 based on the charging control signal corrected in S140, the post-charging load F1 is adjusted within the allowable load range, so that the valve element 19 is pressed against the high-pressure side seat surface 55. It is possible to prevent seal failure due to insufficient load, and to prevent or suppress wear of the valve body 19 and the high-pressure side seat surface 55 due to excessive pressing load.

  In S150 executed following S110 or S140, it is determined whether or not the injection permission signal is turned off. If it is determined in S150 that the injection permission signal is not turned off, the determination of whether or not the injection permission signal is turned off is repeated. If it is determined in S150 that the injection permission signal is turned off, the process proceeds to S160.

  In S160, a discharge control signal is output to the drive circuit 3, and the charge charged in the drive unit 70 is discharged by a known method. Accordingly, the valve body 19 is separated from the high pressure side seat surface 55 so that the valve chamber 53 and the high pressure communication passage 47 communicate with each other, and the valve body 19 is seated on the low pressure side seat surface 54 to Communication with the low-pressure fuel passage 48 is cut off, and fuel injection stops. This flow ends after executing the processing of S160.

  When S30 is NO, that is, when Fa ≦ Fb, when S60 is NO, that is, when ΔTmin> ΔT> ΔTmax, when S130 is NO, that is, when ΔEmin> ΔE> ΔEmax, It is determined that the control valve 18 is malfunctioning due to an abnormality in the displacement transmission unit 30 and the like, and the process proceeds to S170.

  In S170, information on which cylinder of the fuel injection valve 2 determined to be abnormal in S30, S60, and S130 is stored in the EEPROM of the ECU 4, and a process of stopping the fuel injection of the cylinder is performed. To do.

  The communication between the valve body 19 and the valve chamber 53 and the high-pressure communication passage 47 after the charging of the driving unit 70 is started in the time from when charging of the driving unit 70 is started until the injection is started. The time until the valve is shut off is affected by the characteristics of the drive unit 70, but the time from when the valve body 19 shuts off the communication between the valve chamber 53 and the high pressure communication passage 47 until the injection is started is driven. It is not affected by the characteristics of the unit 70.

  Therefore, by controlling the charging of the driving unit 70 based on the charging control signal calculated in S70, the charging of the driving unit 70 is started regardless of the individual variation of the characteristics of the driving unit 70 or deterioration with time. After that, the control valve response time ΔT from when the valve body 19 is disconnected to the communication between the valve chamber 53 and the high-pressure communication passage 47 can be matched with the target control valve response time ΔTp. According to this, it is possible to control the injection start timing and the injection amount with high accuracy irrespective of the individual variation of the characteristics of the drive unit 70 and the deterioration over time.

  Next, the characteristic part of this embodiment is demonstrated in detail using FIGS. 4-8.

  4 is a perspective view of the piezoelectric unit 23 of the piezoelectric actuator 22 in FIG. FIG. 5 is a cross-sectional view of the piezoelectric unit 23. FIG. 6 is an enlarged cross-sectional view of a part of the piezoelectric unit 23.

  As shown in FIG. 4, the piezoelectric unit 23 is formed by stacking piezoelectric element layers 61, 71, 81 and internal electrode layers 62a, 62b, 72a, 72b. The appearance of the piezoelectric actuator 22 is an octagonal prism.

  At the upper end portion of the piezoelectric unit 23, a load sensor unit 60 including a plurality of piezo element layers 61 and a plurality of internal electrode layers 62a and 62b sandwiching the piezo element layers 61 is formed. Below the load sensor unit 60, a driving unit 70 including a plurality of piezo element layers 71 and a plurality of internal electrode layers 72 a and 72 b sandwiching the piezo element layers 71 is also formed from the piezo element layers 81. The connection layer 80 is formed. The load sensor unit 60 may include at least one piezo element layer 61 and at least a pair of internal electrode layers 62a and 62b sandwiching the piezo element layer 61.

  As shown in FIG. 1, the piezoelectric unit 23 has a load sensor 60 directly on a fixed end 57 on the other axial end side of the actuator chamber 56 formed on the other axial end side of the body 40, or It is accommodated so as to contact indirectly.

  On one side surface of the piezoelectric unit 23, a positive electrode side external electrode 65 a of the load sensor unit 60 and a positive electrode side external electrode 75 a of the drive unit 70 are provided. The negative side external electrode 65b of the load sensor unit 60 and the negative side external electrode 75b of the drive unit 70 are provided on the other side surface, which is the side surface opposite to the one side surface on which the positive electrode side external electrodes 65a and 75a are provided. Is provided.

  The positive external electrode 65a is connected to the higher potential terminal of the pair of terminals that receive the load signal generated by the load sensor unit 60 in the drive circuit 3, and the negative external electrode 65b is connected to the other potential. (Not shown).

  The positive external electrode 75a is connected to the higher potential terminal of the pair of terminals for applying a voltage to the drive unit 70 in the drive circuit 3, and the negative external electrode 75b is the other low potential. Is connected to a terminal on the side (not shown).

  The positive electrode side and negative electrode side external electrodes 65a and 65b of the load sensor unit 60 and the positive electrode side and negative electrode side external electrodes 75a and 75b of the drive unit 70 do not need to be provided on the same side surface. As shown in FIG. 7, the arrangement of the positive and negative external electrodes 65a and 65b and the arrangement of the positive and negative external electrodes 75a and 75b may be offset by 90 degrees.

  As shown in FIGS. 5 and 6, the internal electrode layers 62a and 62b in the load sensor unit 60 have electrode exposed portions 64a and 64b exposed on the one side surface and the other side surface of the piezoelectric unit 23, respectively. ing. The internal electrode layers 62a and 62b are connected to one of the pair of positive electrode side and negative electrode side external electrodes 65a and 65b through the electrode exposed portions 64a and 64b. The internal electrode layers 62a and 62b change the connection-destination external electrodes 65a and 65b alternately every other layer.

  Similarly to the internal electrode layers 62a and 62b in the load sensor unit 60, the internal electrode layers 72a and 72b in the one drive unit 70 also have electrode exposed portions 74a and 74b exposed on the one side surface and the other side surface. is doing. The internal electrode layers 72a and 72b are connected to one of the pair of positive electrode side and negative electrode side external electrodes 75a and 75b via the electrode exposed portions 74a and 74b. The internal electrode layers 72a and 72b alternately change the connection destination external electrodes 75a and 75b every other layer.

  In the present embodiment, the piezoelectric unit 23 includes piezoelectric element layers 61, 71, 81 made of a ceramic material such as lead zirconate titanate (PZT), and internal electrode layers 62a, 62b, 72a made of an Ag / Pd alloy. 72b is laminated so as to have the above-described arrangement, and then fired to obtain an integrally laminated fired product that is completely integrated.

  In the present embodiment, of the internal electrode layers 62a and 62b in the load sensor unit 60, the sensor unit side terminal internal electrode layer 63 closest to the drive unit 70 is connected to the negative electrode side external electrode 65b. On the other hand, of the internal electrode layers 72a and 72b in the drive unit 70, the drive unit side terminal internal electrode layer 73 closest to the load sensor unit 60 is connected to the negative electrode side external electrode 75b.

  The sensor unit side termination internal electrode layer 63 and the drive unit side termination internal electrode layer 73 are both negative electrode layers. A connection layer 80 is interposed between both terminal internal electrode layers 63 and 73.

  Here, when a charging current is supplied to the driving unit 70 as shown in FIG. 1, the piezo element layer 71 in the driving unit 70 extends in the stacking direction. When the drive unit 70 extends in the stacking direction, a voltage signal corresponding to the load generated by the drive unit 70 is generated in the load sensor unit 60 as shown in FIG. The generated voltage is about 0V to 50V.

  In the present embodiment, as described above, both the terminal internal electrode layers 63 and 73 are connected to the negative external electrode layers 65b and 75b. Therefore, the polarities of the terminal internal electrode layers 63 and 73 are on the negative side. . For this reason, even when a charge current is supplied to the drive unit 70 and a charge and voltage signal are generated in the load sensor unit 60, the potential difference between the terminal internal electrode layers 63 and 73 becomes very small.

  Even if a high voltage of about 150 V is applied to the piezo element layer 71 in order to supply a charging current to the driving unit 70, the polarities of both terminal internal electrode layers 63 and 73 are on the negative side. Electric leakage to the sensor unit 60 can be suppressed. At this time, a voltage signal of about several tens of volts is generated in the piezo element layer 61 of the load sensor unit 60. Since electric leakage to the load sensor unit 60 can be suppressed, the problem that electrical noise is applied to the voltage signal corresponding to the load of the drive unit 70 taken out from the internal electrode layers 62a and 62b in the load sensor unit 60 is solved. The detection accuracy of the load sensor unit 60 can be improved.

  Thereby, the detection accuracy of the piezo load in S20, S40, and S80 in the control flow of FIG. 3 is remarkably improved. For this reason, it becomes possible to grasp | ascertain an operating state reliably. As a result, since the detection accuracy of the control valve response time ΔT is improved, the injection start timing and the injection amount can be controlled with higher accuracy.

  Further, since electrical leakage to the load sensor unit 60 can be suppressed, it is not necessary to provide, for example, an insulating layer other than the piezo element layer 81 in the connection layer 80 that connects the load sensor unit 60 and the drive unit 70. That is, the connection layer 80 can be the piezo element layer 81 only as in this embodiment, and an increase in the manufacturing cost of the piezoelectric actuator 22 can be suppressed. When used for the fuel injection valve 2 of the piezoelectric actuator 22, an increase in the manufacturing cost of the fuel injection valve 2 can be suppressed.

  In the present embodiment, the connection layer 80 is only the piezo element layer 81. However, if a technique is adopted in which the polarities of both terminal internal electrode layers 63 and 73 are set to the negative side, even if a spacer is used, The spacer can be made as thin as possible, and an increase in manufacturing cost can be suppressed.

  In the present embodiment, the load sensor unit 60 is formed at one end of the drive unit 70. For this reason, the manufacture of the piezoelectric body unit 23 becomes easy, and an increase in manufacturing cost can be suppressed.

  By setting the polarities of both terminal internal electrode layers 63 and 73 to the negative side, an increase in manufacturing cost can be suppressed, and the detection accuracy in the load sensor unit 60 can be improved, and the piezoelectric actuator 22 can be provided. .

  Further, in the present embodiment, as shown in FIG. 1, the piezoelectric body unit 23 is accommodated so that the load sensor unit 60 directly or indirectly contacts the fixed end 57 on the other axial end side of the actuator chamber 56. Has been. According to this, the first time load Fa at the first time Ta when the valve body 19 is separated from the low pressure side seat surface 54 and the second time Tb immediately before the valve body 19 is seated on the high pressure side seat surface 55. The difference from the two-time load Fb, the second time load Fb, and the high-pressure side closing time Tc when the valve body 19 is seated on the high-pressure side seat surface 55 and the communication between the valve chamber 53 and the high-pressure communication passage 47 is blocked. The difference from the threshold value Fc can be made larger than when the load sensor unit 60 is provided on one end side in the axial direction of the actuator chamber 56 (see FIGS. 1 and 3). For this reason, the state of the valve body 19 (separation from the low-pressure side seat surface 54, seating on the high-pressure side seat surface 55, interruption of communication between the valve chamber 53 and the high-pressure communication passage 47). Detection accuracy is improved.

  Next, when the load sensor unit 60 is disposed on one axial end side (displacement transmitting unit 30 side) of the actuator chamber 56 and when it is disposed on the other axial end side (fixed end 57 side) of the actuator chamber 56. The change of the piezo load is explained.

  FIG. 9 is a time chart of only the piezo load portion extracted from the time chart of FIG. In the figure, a solid line indicates the present embodiment, and a broken line indicates a comparative example.

  As is apparent from FIG. 9, in this embodiment, the difference between the first time load Fa at the first time Ta and the second time load Fb at the second time Tb, and the second time load Fb and the high-pressure side closing time Tc. The difference from the threshold value Fc is larger than that of the comparative example indicated by the broken line.

  When the load sensor unit 60 is located on the other end side in the axial direction of the actuator chamber 56, there is no load loss compared to the one located on the one end side in the axial direction. The load increases. When the load sensor unit 60 is positioned on one end side in the axial direction of the actuator chamber 56, the displacement transmission unit 30, the liquid chamber 34, and the movable members of the various springs 20, 35, and 36 exist on the end surface of the load sensor unit 60. Therefore, load loss is generated by these members, and the first time load Fa and the threshold value Fc are considered to be lower than those of the present embodiment. On the other hand, at the second time Tb, the load is applied to some extent from both ends of the load sensor unit 60, so the second time load Fb is considered to be higher than that of the present embodiment.

  For this reason, the difference between the first time load Fa and the second time load Fb is achieved by bringing the load sensor unit 60 into direct or indirect contact with the fixed end 57 side of the actuator chamber 56 as in the present embodiment. In addition, the difference between the second time load Fb and the threshold value Fc can be increased.

  Next, a method for manufacturing the piezoelectric unit 23 of this embodiment will be described with reference to FIGS.

  The piezoelectric unit 23 in the present embodiment is manufactured through a green sheet manufacturing process, an electrode printing process, a burnout slit printing process, a pressure bonding process, a laminate cutting process, a baking process, an insulating resin arranging process, and a polarization process. Hereinafter, each manufacturing process will be described.

(Green sheet production process)
First, a ceramic raw material powder such as lead zirconate titanate (PZT) serving as a piezoelectric element material was prepared. Specifically, Pb ₃ O ₄ , SrCO ₃ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ and Nb ₂ O ₅ are prepared as starting materials, and these starting materials are used as the target composition PbZrO ₃ —PbTiO ₃ —Pb ( Y _1/2 Nb _1/2 ) O ₃ was weighed in a stoichiometric ratio, wet mixed, and calcined at a temperature of 850 ° C. for 5 hours.

  Next, the calcined powder was wet pulverized by a pearl mill. After drying this calcined powder pulverized product (particle size (D50 value): 0.7 ± 0.05 μm), a solvent, a binder, a plasticizer, a dispersant, etc. are added and mixed by a ball mill, and the resulting slurry is obtained. While stirring with a stirrer in a vacuum apparatus, vacuum defoaming and viscosity adjustment were performed.

  And the said slurry was apply | coated on the carrier film with the doctor blade method, and the 80-micrometer-thick green sheet | seat was shape | molded. The green sheet was cut into a predetermined size to produce a wide green sheet 100.

  In addition to the doctor blade method used in the present embodiment, an extrusion molding method and various other methods can be employed as a green sheet molding method.

(Electrode printing process)
Next, as shown in FIGS. 10 and 11, electrode materials 101a and 101b to be the internal electrode layers 62a, 62b, 72a and 72b are printed on the green sheet 100, and the first electrode printed sheet 110a and the second electrode printed sheet 110b are printed. Two types of sheets were formed.

  In forming the first electrode print sheet 110a, as shown in FIG. 10, in the print region 102 on the green sheet 100, the electrode material 101a is printed on the portions that will eventually become the internal electrode layers 62a and 72a. An electrode print sheet 110a was formed.

  In forming the second electrode print sheet 110b, as in the first electrode print sheet 110a, as shown in FIG. 11, in the print region 102 on the green sheet 100, the electrode material 101b is formed on the portions to be the internal electrode layers 62b and 72b. Was printed to form a second electrode printed sheet 110b.

  In the first electrode printed sheet 110a and the second electrode printed sheet 110b, the electrode materials 101a and 101b formed on the green sheet 100 are exposed on the aforementioned one side surface and the other side surface, respectively.

  In this embodiment, paste-like Ag / Pd alloys are used as the electrode materials 101a and 101b. As the electrode materials 101a and 101b, in addition to the above, simple metals such as Ag, Pd, Cu, and Ni, and alloys such as Cu / Ni may be used.

(Burn slit printing process)
In this embodiment, as shown in FIG. 13, the slit groove part 120 is provided in the side surface of the piezoelectric element layer 71 of the piezoelectric unit 23 to be manufactured. In addition, in the piezoelectric body unit 23 shown in FIGS. 4 to 6, the description of the slit groove 120 is omitted for the sake of explanation. The slit groove 120 has a function of relieving internal stress generated when the piezoelectric actuator 22 is operated. The slit groove 120 is formed by sandwiching the burned slit print sheet 111 formed in this step between the first electrode print sheet 110a and the second electrode print sheet 110b.

  As shown in FIG. 12, in the printing region 102 on the green sheet 100, a burned slit layer 112 made of a burned material that is burned off by baking is printed on a portion that finally becomes the slit groove portion 120. Formed.

  In the electrode printing process and the burnout slit printing process, as shown in FIGS. 10 to 12, the gap 103 is provided so as to avoid the portion to be cut in the subsequent laminated body cutting process, and the electrode materials 101 a and 101 b and the burnout slit are formed. The layer 112 is printed.

(Crimping process)
Next, as shown in FIG. 14, the formed first electrode print sheet 110 a, second electrode print sheet 110 b and burnt slit print sheet 111 were laminated in a predetermined order with the printing regions 102 aligned in the lamination direction. In the present embodiment, both the electrode print sheet positioned at the end of the drive unit 70 on the load sensor unit 60 side and the electrode print sheet positioned at the end of the load sensor unit 60 on the drive unit 70 side are both second electrodes. A green sheet 100 on which the electrode materials 101a and 101b and the burned-out slit layer 112 were not printed was laminated between the second electrode print sheets 110b. The green sheet 100 becomes the connection layer 80 after firing. Then, the green sheets 100 on which the electrode materials 101a and 101b and the burned-out slit layer 112 were not printed were laminated on both ends of the piezoelectric unit 23 (see FIG. 15).

  The laminated body thus laminated was heated at a temperature of 100 ° C. and pressurized at 50 MPa in the lamination direction to produce a preliminary laminated body 130.

(Laminate cutting process)
Next, as shown in FIGS. 15 and 16, the formed preliminary laminated body 130 was cut in the lamination direction along the cutting position, and an intermediate laminated body 140 was formed. Note that the preliminary laminated body 130 may be cut for each intermediate laminated body 140 or may be cut including a plurality of intermediate laminated bodies 140. In this embodiment, it cut | disconnects for every intermediate | middle laminated body 140, and it cut | disconnected so that each electrode material 101a, 101b and the burning-out slit layer 112 might be exposed to the side surface of the intermediate | middle laminated body 140. FIG.

(Baking process)
Next, 90% or more of the binder resin contained in the green sheet 100 of the intermediate laminate 140 was removed by heating (degreasing). Heating was performed by gradually raising the temperature to 500 ° C. over 80 hours and holding for 5 hours.

  Next, the degreased intermediate laminate 140 was fired. Firing was performed by gradually raising the temperature to 1050 ° C. over 12 hours, holding for 2 hours, and then gradually cooling.

  In this manner, as shown in FIGS. 4 to 6, an integrally laminated piezoelectric unit 23 made of a completely integrated fired product was formed. In this manner, after the firing step, although not shown in FIGS. 4 to 6, the burnt slit layer 112 is burned out and the slit-shaped slit groove 120 is formed on the side surface of the piezoelectric body unit 23 ( (See FIG. 13).

  Next, after firing, the four corners of the piezoelectric unit 23 were cut out along the stacking direction. Thereby, the piezoelectric unit 23 has an octagonal columnar cross section in the radial direction. Thereafter, the entire surface is polished to expose the electrode exposed portions 64a, 64b, 74a, and 74b of the internal electrode layers 62a, 62b, 72a, and 72b on the side surfaces, and to form the piezoelectric unit 23 having a predetermined size. did. Further, positive electrode side and negative electrode side external electrodes 65a and 65b for the load sensor unit 60, and positive electrode side and negative electrode side external electrodes 75a and 75b for the drive unit 70 were formed by screen printing.

  At this time, the electrode exposed portions 64a and 64b of the internal electrode layers 62a and 62b are electrically connected to the positive external electrode layer 65a and the negative external electrode layer 65b of the load sensor unit 60, respectively. The electrode exposed portions 64a and 64b of the internal electrode layers 72a and 72b are electrically connected to the positive electrode side external electrode layer 75a and the negative electrode side external electrode layer 75b of the drive unit 70, respectively.

  The positive electrode side and negative electrode side external electrodes 65a and 65b of the load sensor unit 60 and the positive electrode side and negative electrode side external electrodes 75a and 75b of the drive unit 70 were formed so as to maintain a constant electrical insulation distance. Preferably, the electric field strength is 1 kV / mm or less.

  Then, lead wires or mesh-like electrode plates are respectively connected to the positive electrode side, negative electrode side external electrodes 65a and 65b of the load sensor unit 60, and the positive electrode side and negative electrode side external electrodes 75a and 75b of the driving unit 70 with conductive resin or solder. Etc.

(Insulating resin placement process)
Next, in this embodiment, the insulating resin 121 is disposed in the slit groove 120 as shown in FIG. Specifically, the insulating resin 121 made of a thermosetting silicone resin was applied to the slit groove portion 120 and heated to be cured. As the insulating resin 121, a highly heat-resistant urethane resin or fluorosilicone resin may be used.

(Polarization process)
Next, polarization processing is performed on the piezoelectric unit 23 that has undergone the above-described steps. In this embodiment, a DC voltage of 160 V is applied to the load sensor unit 60 and the drive unit 70 for 2 minutes. At that time, the polarity of the sensor unit side termination internal electrode layer 63 (see FIGS. 5 and 6) in the load sensor unit 60 and the polarity of the drive unit side termination internal electrode layer 73 (see FIGS. 5 and 6) in the drive unit 70 Also, the polarization process is performed so as to be on the negative electrode side.

  The polarization processing of the load sensor unit 60 and the drive unit 70 may be performed simultaneously or separately. Further, the polarization process may be executed in a state of being attached to a jig for applying a predetermined preload according to the number of layers of the load sensor unit 60 and the drive unit 70. Moreover, you may change the atmospheric temperature at the time of performing a polarization process. For example, the polarization process may be performed at 140 ° C. The polarization process may be performed not only by applying a DC voltage but also by applying an AC voltage such as a sine wave or a trapezoidal wave.

  Through the polarization process described above, the piezoelectric unit 23 in which both the sensor unit side termination internal electrode layer 63 and the drive unit side termination internal electrode layer 73 are on the negative electrode side was obtained.

  In the present embodiment, the burnout slit print sheet 111 is inserted between the first electrode print sheet 110 a and the second electrode print sheet 110 b constituting the drive unit 70, and the slit groove 120 is formed on the side surface of the drive unit 70. Although formed, this burn-out slit print sheet 111 is not necessarily required.

  In this embodiment, the piezoelectric unit 23 is formed as a so-called monolithic piezoelectric unit. As a form of the piezoelectric unit 23, there is a single-plate laminated type in addition to the integral laminated type. A single-plate laminated piezoelectric unit is different from an integral laminated type in that an internal electrode layer is printed and fired on a previously fired piezo element layer and laminated appropriately to form a piezoelectric unit.

  Even in this single-plate stacked piezoelectric unit, the effects of the above-described embodiment can also be achieved by setting the polarities of the sensor unit side termination internal electrode layer 63 and the drive unit side termination internal electrode layer 73 to the negative side. Can get.

  However, when the piezoelectric unit 23 is an integral laminate type, it is superior to the single plate laminate type in the following points. In a single-plate stacked piezoelectric unit, generally, a conductor (for example, a metal foil such as stainless steel or copper) that is electrically connected to an internal electrode layer and the outside is disposed between piezoelectric element layers.

  When the load sensor unit 60 and the drive unit 70 are formed as a single-plate laminated type, if the load sensor unit 60 tries to detect the load when the drive unit 70 is extended, the load sensor unit 60 and the drive unit 70 are arranged between the piezoelectric element layers. The conductor is deformed. For this reason, force transmission loss occurs, and the detection accuracy of the load sensor unit 60 may be reduced. In addition, since the deformation of the conductor changes depending on the use situation, even if a predetermined voltage is applied to the drive unit 70 to extend a predetermined amount, the detection result of the load sensor unit 60 changes and the detection accuracy is improved. descend.

  On the other hand, the piezoelectric unit 23 of the present embodiment is formed as an integrally laminated fired body as described above. Here, as described above, in the integrally laminated piezoelectric unit 23, the electrode exposed portions 64a, 64b, 74a, and 74b of the internal electrode layers 62a, 62b, 72a, and 72b are exposed by baking and firing. Is easy. Therefore, in the integrally laminated piezoelectric unit 23, there is no need to insert a conductor between the piezoelectric element layers. By using the piezoelectric unit 23 as an integral laminate type, loss of force transmitted from the drive unit 70 to the load sensor unit 60 can be suppressed, and the detection accuracy of the load sensor unit 60 is improved as compared with a single plate laminate type.

  In addition, since the monolithic piezoelectric unit 23 is a single fired product, the physical properties of the load sensor unit 60 and the drive unit 70 are higher than those of the single plate laminate type in which the fired products fired separately are stacked. Very close. For this reason, calibration (correction) of the temperature characteristics of the voltage signal output from the load sensor unit 60 is easy.

(Second Embodiment)
As shown in FIGS. 17 and 18, the second embodiment of the present invention is a modification of the first embodiment. In the first embodiment, the piezoelectric unit 23 is composed of one fired product, whereas in the second embodiment, the piezoelectric unit 23 is composed of a single unit 23a and a plurality of units 23a, 23b. ing. Specifically, the piezoelectric unit 23 includes one sensor unit-equipped piezoelectric unit 23 a having a part of the load sensor unit 60 and the driving unit 70, and five driving units having only other parts of the driving unit 70. The piezoelectric units 23b are stacked.

  The external appearance of the piezoelectric body unit 23 in this embodiment is almost the same as that of the first embodiment, and has an octagonal prism shape. As shown in FIGS. 17 and 18, on the side surface of the piezoelectric unit with sensor part 23a, the positive side of the load sensor part 60, the negative side external electrodes 65a and 65b, the positive side of the drive part 70, and the negative side external electrode 75a. , 75b. The drive unit piezoelectric unit 23b is also provided with positive and negative external electrodes 75a and 75b of the drive unit 70.

  As shown in FIG. 18, the sensor unit-attached piezoelectric unit 23 a, the drive unit piezoelectric unit 23 b, and the drive unit piezoelectric unit 23 b are joined together by, for example, a silicone-based adhesive 90.

  Also in the present embodiment, the sensor unit-equipped piezoelectric unit 23a and the drive unit piezoelectric unit 23b are integrally laminated piezoelectric units, like the piezoelectric unit 23 of the first embodiment. The manufacturing method is the same as the method described in the first embodiment.

  In this way, by combining a plurality of piezoelectric units into one piezoelectric unit, the following effects can be obtained.

  Here, when the piezoelectric unit 23 having a predetermined length is formed as an integrally fired product as in the first embodiment, when the driving unit 70 is extended, stress may be concentrated near the side surface of the driving unit 70. . If stress concentrates in the vicinity of the side surface, the portion where the stress is concentrated may be damaged. This phenomenon becomes more prominent as the number of stacked piezoelectric element layers 71 of the drive unit 70 increases.

  On the other hand, in the second embodiment, the piezoelectric unit 23 having a predetermined length is formed by stacking one piezoelectric unit with a sensor unit 23a and a plurality of driving unit piezoelectric units 23b.

  According to this, the degree of stress concentrated in the vicinity of the side surface of the drive unit 70 when the drive unit 70 is extended can be reduced. For this reason, damage to the piezoelectric unit 23 can be suppressed as much as possible, and the quality can be improved.

(Third embodiment)
As shown in FIG. 19, the third embodiment of the present invention is a modification of the second embodiment. In the third embodiment, the piezoelectric unit 23 is common to the piezoelectric unit of the second embodiment in that the piezoelectric unit 23 includes a plurality of units, but the configuration of the piezoelectric unit having the load sensor unit 60 is different. Specifically, the piezoelectric unit 23 is configured by stacking a plurality of sensor unit piezoelectric units 25 a including only the load sensor unit 60 and a driving unit piezoelectric unit 25 b including only the driving unit 70. Note that there may be at least one drive unit piezoelectric body unit 25b, and a plurality of drive unit piezoelectric units need not necessarily be stacked.

  As shown in FIG. 19, the sensor unit side termination internal electrode layer 63 of the sensor unit piezoelectric unit 25a and the drive unit side termination internal electrode layer 73 of the drive unit piezoelectric unit 25b are both negative electrode layers.

  Further, as shown in FIG. 19, an insulating ceramic plate 91 made of alumina, silicon nitride, or the like is provided between the sensor unit piezoelectric unit 25a and the drive unit piezoelectric unit 25b. Thereby, it is possible to reliably prevent electrical leakage from the drive unit piezoelectric unit 25b to the sensor unit piezoelectric unit 25a from the drive unit piezoelectric unit 25b to the sensor unit piezoelectric unit 25a.

  Also, according to this embodiment, the sensor unit piezoelectric body unit 25a and the drive unit piezoelectric are compared with the case where a unit including the load sensor unit 60 and the drive unit 70 is prepared in one unit as shown in the second embodiment. There is no need to divide the specifications of the body unit 25b, and a piezoelectric body unit having a common specification can be obtained. For this reason, the piezoelectric actuator 22 having the load sensor unit 60 can be manufactured at low cost.

(Fourth embodiment)
As shown in FIG. 20, the fourth embodiment of the present invention is a modification of the first to third embodiments. In the fourth embodiment, the structure of the connection layer 80a is different from that of the other embodiments. Specifically, the thickness of the piezo element layer 81 a is thicker than the piezo element layers 61 and 71 in the other load sensor unit 60 and the drive unit 70.

  For this reason, the insulation between the load sensor part 60 and the drive part 70 can be made more reliable, and the detection accuracy of the load sensor part 60 can be improved.

(Fifth embodiment)
As shown in FIG. 21, the fifth embodiment of the present invention is a modification of the first to fourth embodiments. In the fifth embodiment, the structure of the connection layer 80b is different from that of the other embodiments. Specifically, the connection layer 80 b is formed not only by the piezo element layer 81 but also by alternately laminating the piezo element layers 81 and the internal electrode layers 82. The piezo element layer 81 and the internal electrode layer 82 are composed of the same green sheet 100 and electrode materials 101a and 101b as the piezo element layers 61 and 71 and the internal electrode layers 62a, 62b, 72a and 72b in the load sensor section 60 and the drive section 70. Has been. The internal electrode layer 82 is not connected to any external electrode 65a, 65b, 75a, 75b.

  According to this configuration, after firing, the same green sheet 100 disposed in the portion serving as the connection layer 80b can be used as the green sheet 100 disposed in the portion serving as the load sensor unit 60 or the driving unit 70. , Increase in manufacturing cost can be suppressed.

  In addition, since the piezo element layers 81 and the internal electrode layers 82 are alternately stacked, a plurality of piezo element layers 81 can be stacked. Also with this configuration, since the connection layer 80 can be formed thick, insulation between the load sensor unit 60 and the drive unit 70 can be ensured.

  Also, like the load sensor unit 60 and the drive unit 70, the connection layer 80b also includes the piezoelectric element layers 81 and the internal electrode layers 82 that are alternately stacked. The layer 80 b can also be fired in the same environment as the load sensor unit 60 and the drive unit 70, and the state of the connection layer 80 b after firing can be the same as that of the load sensor unit 60 and the drive unit 70. If the internal electrode layer 82 sandwiching the piezoelectric element layer 81 has a function as a sintering aid, the mechanical strength of the connection layer 80b can be secured, and the quality of the piezoelectric unit 23 can be improved.

  The piezo element layer including the internal electrode layer and the piezo element layer not including the internal electrode layer have different shrinkage rates upon firing. According to the present embodiment, the firing shrinkage of the connection layer 80b, the load sensor unit 60, and the drive unit 70 can be matched. As a result, peeling, cracking, and the like after firing of the piezoelectric body unit 23 due to mismatching firing shrinkage can be avoided.

(Sixth embodiment)
As shown in FIG. 22, the sixth embodiment of the present invention is a modification of the first to fifth embodiments. In the sixth embodiment, the structure of the piezo element layer 71a disposed between the drive unit-side terminal internal electrode layer 73 and the internal electrode layer 72a in the drive unit 70 adjacent thereto is different from those of the other embodiments. Specifically, the thickness of the piezo element layer 71 a is made thicker than that of the piezo element layer 71 at the center of the drive unit 70. According to this configuration, the shear stress generated at the end of the drive unit 70 when the drive unit 70 is expanded and contracted can be relaxed.

(Seventh embodiment)
As shown in FIG. 23, the seventh embodiment of the present invention is a modification of the first embodiment. In the seventh embodiment, the mechanisms for controlling the valve closing drive and the valve opening drive of the needle 212 are different. In the fuel injection valve 2 according to the first embodiment, the displacement actuator 30 is directly driven by the piezoelectric actuator 22, and the displacement in the displacement transmitter 30 is transmitted to the control valve 18. It drives to adjust the pressure in the control chamber 246 to control the opening / closing drive of the needle 212. On the other hand, the fuel injection valve 200 in the seventh embodiment controls the fuel pressure in the control chamber 246 by changing the movement amount of the cylinder 217 by the piezoelectric actuator 22 and controls the opening / closing drive of the needle 212.

  The fuel injection valve 200 includes a nozzle 211, a cylinder 217, a fixed piston 220, an actuator portion 230, and the like, and these components are accommodated in a body 240 formed in a rod shape.

  The body 240 includes a fuel inlet 241 into which high-pressure fuel from the pressure accumulator is introduced. A housing portion 242 is formed on one end side of the body 240 in the axial direction, and the housing portion 242 houses a nozzle 211 that controls fuel injection and non-injection. The accommodating portion 242 corresponds to the “first hydraulic chamber” described in the claims.

  The nozzle 211 has a needle 212 and a nozzle spring 216. The needle 212 is slidably held in the housing portion 242. An injection hole 243 that communicates with the fuel inlet 241 via the high-pressure fuel passage 245 is formed at one axial end side of the housing 242.

  A valve seat 244 on which the seat portion 213 formed on the needle 212 is seated is formed on the fuel inlet portion 241 side of the nozzle hole 243. When the seat portion 213 is seated on the valve seat 244, the flow of fuel to the injection hole 243 is blocked, and fuel injection from the injection hole 243 is stopped. By separating the seat portion 213 from the valve seat 244, the flow of fuel to the injection hole 243 is released, and fuel is injected from the injection hole 243. A piston portion 214 is formed at the end of the needle 212 opposite to the seat portion 213.

  The piston part 214 is slidably inserted into the cylinder 217. A flange portion 215 is formed between the seat portion 213 and the piston portion 214 of the needle 212, and a nozzle spring 216 is provided between the flange portion 215 and the cylinder 217. The nozzle spring 216 urges the needle 212 in the direction in which the seat portion 213 is seated on the valve seat 244, that is, in the valve closing direction.

  The actuator portion 230 is accommodated on the other axial end side of the accommodation portion 242. The actuator unit 230 includes the piezoelectric actuator 22 described in the first to fifth embodiments, and a push plate 231 that transmits the displacement from the piezoelectric actuator 22 to the cylinder 217. When the drive unit 70 of the piezoelectric actuator 22 expands and contracts, the cylinder 217 is driven via the push plate 231.

  The cylinder 217 is a stepped cylindrical member having a stepped portion on the inner peripheral surface, and a first cylinder hole 218 is formed on one side of the stepped portion, and a first cylinder is formed on the other side of the stepped portion. A second cylinder hole 219 having a diameter larger than that of the hole 218 is formed. The cylinder 217 is accommodated in the accommodating portion 242 such that the first and second cylinder holes 218 and 219 are arranged along the axial direction of the body 240. The first cylinder hole 218 is disposed closer to the injection hole 243 than the second cylinder hole 219.

  A fixed piston 220 is slidably inserted into the second cylinder hole 219. The fixed piston 220 includes a fixed piston portion 221 and a flange portion 222 that protrudes radially outward from the fixed piston portion 221. Only the fixed piston portion 221 is inserted into the second cylinder hole 219.

  A control chamber 246 is formed between the fixed piston portion 221 and the piston portion 214 of the needle 212 by the cylinder 217, the fixed piston portion 221 and the piston portion 214. The high-pressure fuel that has flowed into the accommodating portion 242 flows into the control chamber 246 via the clearance between the first cylinder hole 218 and the piston portion 214, and the second cylinder hole 219 and the fixed piston portion 221. . The control chamber 246 corresponds to a “second hydraulic chamber” described in the claims.

  FIG. 24 is a XXIV view of the fixed piston 220 as viewed from the injection hole 243 side. As shown in this figure, the flange portion 222 of the fixed piston 220 is divided into three pieces along the circumferential direction, and a notch 223 is formed between the adjacent flange portions 222. As shown in FIG. 23, the flange portion 222 is sandwiched between a spacer 234 supported on the inner wall of the housing portion 242 and a fixed spring 235 supported on the inner wall of the housing portion 242, whereby the fixed piston 220 is Fixed to the body 240.

  FIG. 25A is a front view of the push plate 231, and FIG. 25B is a bottom view of the push plate 231. As shown in FIG. 25, the push plate 231 includes a columnar disc portion 232 and three columnar leg portions 233 protruding in the axial direction from one end surface of the disc portion 232.

  These leg portions 233 are provided along the circumferential direction at positions where the leg portions 233 are inserted into the notches 223 when the push plate 231 and the fixed piston 220 are combined (see FIG. 24). As shown in FIG. 23, the push plate 231 is accommodated in the accommodating portion 242 such that the disc portion 232 abuts on the driving portion 70 of the piezoelectric actuator 22 and the leg portion 233 abuts on the cylinder 217.

  Next, the operation of the fuel injection valve 200 will be described. When the drive unit 70 of the piezoelectric actuator 22 is not extended, the cylinder 217 is moved to the piezoelectric actuator 22 side by the urging force of the nozzle spring 216. At this time, high-pressure fuel in the accommodating portion 242 flows into the control chamber 246 through the clearance between the first cylinder hole 218 and the piston portion 214 and the clearance between the second cylinder hole 219 and the fixed piston portion 221. The fuel pressures in the control chamber 246 and the accommodating portion 242 are equal.

  In this state, the needle 212 is closed by a force in the valve closing direction generated by the needle 212 due to the fuel pressure in the control chamber 246 acting on the piston portion 214 and a force generated by the urging force of the nozzle spring 216. The sum of the forces in the valve direction is larger than the force in the valve opening direction generated in the needle 212 due to the high pressure fuel in the accommodating portion 242 acting on the needle 212. For this reason, the seat part 213 of the needle 212 is seated on the valve seat 244, and the fuel injection from the injection hole 243 is stopped (state shown in FIG. 23).

  When the drive unit 70 extends, the cylinder 217 moves toward the nozzle hole 243 as the drive unit 70 extends. Since the diameter of the first cylinder hole 218 is smaller than that of the second cylinder hole 219, the volume in the control chamber 246 increases when the cylinder 217 moves to the injection hole 243 side. As a result, the fuel pressure in the control chamber 246 decreases as the cylinder 217 moves. Thereby, the total force in the valve closing direction generated in the needle 212 becomes smaller than the force in the valve opening direction, the needle 212 moves in the valve opening direction, and the seat portion 213 is separated from the valve seat 244, Fuel is injected from the injection hole 243.

  Thereafter, when the drive unit 70 contracts again, the cylinder 217 moves to the piezoelectric actuator 22 side by the urging force of the nozzle spring 216, and the volume of the control chamber 246 decreases. Thereby, the fuel pressure in the control chamber 246 increases, and the total force in the valve closing direction becomes larger than the force in the valve opening direction. Accordingly, the seat portion 213 is seated on the valve seat 244, and fuel injection from the injection hole 243 is stopped.

It is sectional drawing which shows the whole structure of the fuel supply apparatus containing the fuel injection valve by 1st Embodiment of this invention. It is a flowchart which shows the control processing performed in the electronic controller which controls the fuel injection valve shown in FIG. It is a time chart which shows the action | operation of a fuel injection valve when the control processing in FIG. 2 is performed. It is a perspective view of the piezoelectric body unit in the piezoelectric actuator provided in FIG. It is sectional drawing which shows the structure of the piezoelectric material unit shown in FIG. It is sectional drawing to which some piezoelectric body units shown in FIG. 4 were expanded. It is a perspective view which shows the structure of the piezoelectric body unit which shows the other example of the piezoelectric body unit shown in FIG. FIG. 5 is a characteristic diagram showing a relationship between a load generated from the piezoelectric unit shown in FIG. 4 and an output from a load sensor unit. 5 is a time chart showing a piezo load for explaining an effect when the load sensor part of the piezoelectric body unit shown in FIG. 4 is arranged on one end side in the axial direction of the actuator chamber or on the other end side in the axial direction. It is a perspective view which shows the structure of the 1st electrode printing sheet in an electrode printing process among the manufacturing processes of the piezoelectric material unit shown in FIG. It is a perspective view which shows the structure of the 2nd electrode printing sheet in an electrode printing process among the manufacturing processes of the piezoelectric material unit shown in FIG. It is a perspective view which shows the structure of the burnout slit printing sheet in a burnout slit printing process among the manufacturing processes of the piezoelectric material unit shown in FIG. It is sectional drawing to which some piezoelectric body units shown in FIG. 4 were expanded. It is a perspective view which shows the structure of the preliminary | backup laminated body in a crimping | compression-bonding process among the manufacturing processes of the piezoelectric material unit shown in FIG. It is a side view which shows the structure of the preliminary | backup laminated body in a laminated body cutting process among the manufacturing processes of the piezoelectric material unit shown in FIG. It is a side view which shows the structure of the intermediate | middle laminated body after cut | disconnecting at the laminated body cutting process among the manufacturing processes of the piezoelectric material unit shown in FIG. It is a perspective view which shows the structure of the piezoelectric body unit in the piezoelectric actuator by 2nd Embodiment. FIG. 18 is an enlarged sectional view of a part of the piezoelectric unit shown in FIG. 17. It is sectional drawing to which some piezoelectric body units in the piezoelectric actuator by 3rd Embodiment were expanded. It is sectional drawing to which some piezoelectric material units in the piezoelectric actuator by 4th Embodiment were expanded. It is sectional drawing to which some piezoelectric body units in the piezoelectric actuator by 5th Embodiment were expanded. It is sectional drawing to which some piezoelectric material units in the piezoelectric actuator by 6th Embodiment were expanded. It is sectional drawing which shows the structure of the fuel injection valve by 7th Embodiment. It is a XXIV view of the fixed piston of FIG. (A) is a front view of the push plate of FIG. 23, (b) is a bottom view of the push plate.

Explanation of symbols

  1 fuel supply device, 2 fuel injection valve, 3 drive circuit, 4 electronic control unit (ECU), 8 return path, 9 back pressure valve, 10 fuel tank, 11 nozzle, 12 needle, 16 nozzle spring, 17 nozzle cylinder, 18 control Valve, 19 Valve body, 20 Valve spring, 21 Actuator part, 22 Piezoelectric actuator, 23 Piezoelectric unit, 30 Displacement transmission part, 34 Liquid chamber, 40 Body, 41 Fuel inlet part, 43 Housing part, 44 Injection hole, 46 High pressure Fuel passage, 47 high pressure communication passage, 48 low pressure fuel passage, 49 low pressure communication passage, 50 communication passage, 52 control chamber, 53 valve chamber, 54 low pressure side seat surface, 55 high pressure side seat surface, 56 actuator chamber, 57 fixed end, 60 Load sensor part, 61 Piezo element layer, 62a and 62b Internal electrode layer, 63 Sensor unit side termination internal electrode layer, 64a / 64b electrode exposed portion, 65a positive electrode side external electrode, 65b negative electrode side external electrode, 70 drive unit, 71 piezo element layer, 72a / 72b internal electrode layer, 73 drive unit side termination internal electrode Layer, 74a / 74b electrode exposed portion, 75a positive electrode external electrode, 75b negative electrode external electrode, 80 connection layer, 81 piezo element layer, 82 internal electrode layer, 100 green sheet, 101a electrode material, 101b electrode material, 102 printing area 110a first electrode printing sheet, 110b second electrode printing sheet, 111 burnout slit printing sheet, 112 burnout slit layer, 130 preliminary laminate, 140 intermediate laminate

Claims (11)

A piezoelectric actuator having a piezoelectric unit formed by laminating a plurality of piezoelectric layers and a plurality of internal electrode layers,
The piezoelectric unit includes a pair of internal electrode layers sandwiching the piezoelectric layer and the piezoelectric layer, and a drive unit that is distorted according to a voltage applied to the piezoelectric layer via the internal electrode layer; A load sensor unit including a piezoelectric layer and a pair of internal electrode layers sandwiching the piezoelectric layer, and outputting a load signal corresponding to a load acting on the piezoelectric layer via the internal electrode layer;
The polarity of the internal electrode layer in the drive unit when a voltage is applied to the piezoelectric layer of the drive unit is such that one of the internal electrode layers is on the positive side and the other internal electrode layer is on the negative side.
The polarity of the internal electrode layer in the load sensor portion when a load is applied to the load sensor portion is such that one internal electrode layer is on the positive side and the other internal electrode layer is on the negative side,
Of the internal electrode layers in the drive unit, the polarity of the drive unit side terminal internal electrode layer disposed closest to the load sensor unit when a voltage is applied to the drive unit, and the load sensor unit in the load sensor unit Among the internal electrode layers, when the load is applied to the load sensor unit, the polarity of the sensor unit side terminal internal electrode layer disposed closest to the drive unit is both negative, . A connection layer is disposed between the sensor unit termination internal electrode layer and the drive unit termination internal electrode layer,
2. The piezoelectric actuator according to claim 1, wherein the connection layer is the piezoelectric layer and is thicker than the piezoelectric layer in the load sensor unit or the piezoelectric layer in the driving unit. A connection layer is disposed between the sensor unit termination internal electrode layer and the drive unit termination internal electrode layer,
2. The piezoelectric actuator according to claim 1, wherein the connection layer is formed by alternately laminating the piezoelectric layers and the internal electrode layers.   The terminal piezoelectric layer disposed adjacent to the drive unit side termination internal electrode layer and the drive unit side termination internal electrode layer on the opposite side of the load sensor unit is the other piezoelectric element in the drive unit. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator is thicker than the body layer.   The piezoelectric unit is a laminated fired body having the piezoelectric layer and the internal electrode layer constituting the load sensor unit, and the piezoelectric layer and the internal electrode layer constituting the drive unit. The piezoelectric actuator according to any one of claims 1 to 4.   The piezoelectric unit is a laminated fired body having the piezoelectric layer and the internal electrode layer constituting the load sensor unit, and the piezoelectric layer and the internal electrode layer constituting a part of the driving unit. It is comprised from the piezoelectric part unit with a part, and the drive part piezoelectric material unit which is the laminated fired body which has the said piezoelectric material layer and the said internal electrode layer which comprise the other part of the said drive part. Item 5. The piezoelectric actuator according to any one of Items 1 to 4.   The piezoelectric unit includes a sensor unit piezoelectric unit that is a laminated fired body including the piezoelectric layer and the internal electrode layer constituting the load sensor unit, and the piezoelectric layer and the internal electrode constituting the driving unit. 5. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator includes a drive unit piezoelectric unit that is a laminated fired body having layers.   The piezoelectric actuator according to any one of claims 1 to 7, wherein the load sensor unit is formed at one end of the piezoelectric unit. An injection hole through which fuel is injected, a body having a high-pressure fuel passage for supplying high-pressure fuel to the injection hole;
A valve member that is housed in the body and controls the intermittent connection between the nozzle hole and the high-pressure fuel passage;
A first hydraulic pressure chamber for storing high-pressure fuel from the high-pressure fuel passage that communicates with the high-pressure fuel passage and generates force in the valve opening direction by acting on the valve member;
A second hydraulic pressure chamber for storing high-pressure fuel from the high-pressure fuel passage that communicates with the high-pressure fuel passage and generates a force in a valve closing direction by acting on the valve member;
A control valve housed in the body for controlling the fuel pressure of either the first hydraulic chamber or the second hydraulic chamber;
The piezoelectric actuator according to any one of claims 1 to 8,
A displacement transmitting portion for transmitting the displacement of the piezoelectric actuator to the control valve;
A fuel injection valve comprising: An injection hole through which fuel is injected, and a body having a high-pressure fuel passage for supplying high-pressure fuel to the injection hole;
A valve member that is housed in the body and controls the intermittent connection between the nozzle hole and the high-pressure fuel passage;
A first hydraulic pressure chamber for storing high-pressure fuel from the high-pressure fuel passage that communicates with the high-pressure fuel passage and generates force in the valve opening direction by acting on the valve member;
A second hydraulic pressure chamber for storing high-pressure fuel from the high-pressure fuel passage that communicates with the high-pressure fuel passage and generates a force in a valve closing direction by acting on the valve member;
A cylinder that is accommodated in the body and moves to change the volume of either the first hydraulic chamber or the second hydraulic chamber or both, and to control the fuel pressure;
The piezoelectric actuator according to any one of claims 1 to 8, which directly drives the cylinder;
A fuel injection valve comprising: The body is formed with an actuator chamber that accommodates the piezoelectric actuator according to any one of claims 1 to 8,
11. The piezoelectric actuator is housed in the actuator chamber so that the load sensor portion is positioned on a fixed end side of the actuator chamber positioned on the opposite side to the valve member. The fuel injection valve described in 1.

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