JP5348000B2 - Press-in method and apparatus for piezo actuator - Google Patents

Description

  The present invention relates to a gap measurement press-fitting method and apparatus for assembling a piezo actuator, particularly an injector piezo actuator.

  In a diesel engine, a common rail system that accumulates high-pressure fuel on a common rail common to each cylinder is known. High pressure fuel is pumped from the fuel supply pump to the common rail and controlled to a predetermined pressure, and fuel is injected into each cylinder at a predetermined timing. The fuel injection device for the common rail has a control chamber that applies pressure in the valve closing direction to the nozzle needle, and a control valve that controls the pressure in the control chamber. The control valve is driven by a piezoelectric actuator to control the pressure in the control chamber. It is configured to increase or decrease.

The piezo actuator found in Patent Document 1 can be expected to perform advanced fuel injection control because of its good response, and has the following structure.
A driving force transmission device that transmits the driving force of a piezo actuator via hydraulic pressure forms an oil-tight chamber between two pistons and transmits the displacement of the actuator hydraulically, and uses two pistons with different diameters. Then, the displacement is enlarged and transmitted according to the pressure receiving area ratio of the large diameter piston and the small diameter piston. As the control valve, a three-way valve structure for selectively communicating the control chamber with the high-pressure passage or the low-pressure passage is used. The control valve moves between the low-pressure side seat leading to the low-pressure passage and the high-pressure side seat leading to the high-pressure passage. Switch. When the piezo actuator is extended by energization, the hydraulic driving force transmission device drives the control valve to be separated from the low-pressure side seat, and then is seated on the high-pressure side seat. As a result, the pressure in the control chamber is lowered, the nozzle needle is lifted, and fuel is injected.

In the assembly process of such a piezo actuator, the following problems have occurred. FIGS. 1A and 1B are explanatory views of a process of assembling a piezo actuator. (A) is before assembly and (b) is after assembly.
The piezoelectric actuator 1 includes a pipe 3 and a housing 4, and a piston 10 is attached to the pipe 3 via a diaphragm 2. The subassembly in which the diaphragm 2 and the piston 10 are attached to the pipe 3 will be referred to as the pipe 3 below. When the piezoelectric actuator is assembled, the pipe 3 is press-fitted into the housing 4 (see FIG. 1A). 5 is a piezo stack. Individual piezos are bonded and stacked with an adhesive to form a piezo stack.

  In such a pipe assembling process, whether or not the pipe press-fitting position is normal is confirmed by checking whether or not the amount of movement of the piston is appropriate for the product after the final process, and performing quality control. That is, when the pipe is covered, it is sealed and the inside gap (referring to the gap between the end face of the piezo stack 5 and the piston 10; see FIG. 1B) cannot be seen. By passing an electric current, the piezo moves up and down by a minute amount, causing the piston to swing), and the amount of movement of the piston is detected and confirmed. For this reason, since assembly is performed without measuring the gap between the end face of the piezo stack and the piston at the time of pipe press-fitting, there has been a problem that defects often occur.

JP 2007-231737 A

  In view of the above problems, the present invention provides a gap measurement press-fitting method and apparatus for assembling a piezo actuator, particularly an injector piezo actuator.

In order to solve the above problems, the invention of claim 1 is to press a pipe (3) having a piston (10) attached through a diaphragm (2) by a press-fitting punch (51) driven by a servo motor. The piezoelectric actuator press-fitting method for press-fitting into a housing (4) having a piezo stack (5) so that a gap is appropriately maintained between the piston (10) and the piezo stack (5). The first press-fitting step of press-fitting the pipe (3) into the housing (4), and the pipe (3) is press-fitted into the housing (4) by a predetermined amount, and the pipe (3 ) Under a press-fitting pressure (P ₃ ), a second press-fitting step having a gap detecting step of detecting a first gap amount (x) generated between the piston (10) and the piezo stack (5). When, Gap detecting step, wherein the independent suspension into the press punch (51), said piston retainer moves the piston presser (52) which is driven (52) by the pressing to Rukoto the piston (10) by the pulse motor, wherein After the piston presser (52) starts moving from the zero point position by the pulse motor, the position of the piston presser (52) until the piston (10) is seated on the end face of the piezo stack (5) is measured. to the first gap amount (x) is configured to detect, after the gap detection step is completed, he said after opening the injection pressure (P _3), the gap of the pipe (3) Taking into account the first gap amount (x) detected in the detection step and the amount of elastic deformation in the axial direction of the pipe (3) due to the release of the press-fitting pressure (P ₃ ) of the pipe (3). And Serial is a third piezo actuator pressed method of and a press-fitting step of press-fitting to the pipe (3) of the housing (4).

  As a result, the assembly can be performed without generating a gap between the end face of the piezo stack and the piston at the time of pipe press-fitting or within an allowable range. It became possible to suppress the occurrence of defects.

According to a second aspect of the present invention, in the first aspect of the invention, the predetermined amount to be press-fitted in the second press-fitting step is zero, and the press-fitting pressure (P ₃ ) in the second press-fitting step is It is equal to the press-fitting pressure in the press-fitting process of No. 1. Thereby, the press-fitting process can be simplified.

The invention of claim 3 is a piezo actuator press-fitting device for press-fitting a pipe (3) having a piston (10) attached via a diaphragm (2) into a housing (4) having a piezo stack (5). A press-fitting punch (51) driven by a servo motor that presses the pipe (3), and a piston presser (52) that is independently suspended from the press-fitting punch (51) and driven by a pulse motor. In the press-fitting device for a piezo actuator, the pipe (3) is preliminarily disposed in a housing (so that the press-fitting punch (51) holds an appropriate gap between the piston (10) and the piezo stack (5). 4), and the pipe (3) is press-fitted into the housing (4) by a predetermined amount, and after the press-fitting pressure (P3) of the pipe (3) after the predetermined amount of press-fitting. Then, the piston presser (52) is moved to move the piston presser (52) through the gap (x) generated between the piston (10) and the piezo stack (5), and the piston presser (52) presses the piston (10). by be Rukoto, the piston retainer (52) is, after starting to move by the pulse motor from the zero point position, said piston retainer to said piston (10) is seated on the end face of the piezo stack (5) ( 52), the gap (x) is detected, the press-fit pressure (P3) of the pipe (3) is released, and the press-fit pressure (P3) of the gap (x) and the pipe (3) is released. The piezoelectric actuator is controlled so that the pipe (3) is further press-fitted into the housing (4) in consideration of the amount of elastic deformation in the axial direction of the pipe (3) due to the opening of the pipe (3). It is an indentation device. Thereby, the same effect as that of the invention of claim 1 is produced.

  In addition, the code | symbol attached | subjected above is an example which shows a corresponding relationship with the specific embodiment as described in embodiment mentioned later.

(A), (b) is explanatory drawing of the process of assembling a piezoelectric actuator. (A) is before assembly and (b) is after assembly. (A) is sectional drawing which shows the outline | summary of an injector. (B) is an expanded sectional view which shows the piezoelectric actuator of (a). (A)-(c) is explanatory drawing explaining the coupling | bonding method of the structural member of a piezoelectric actuator. It is explanatory drawing explaining the press injection process of one Embodiment of this invention. (A) is 1st press injection, (b) is 2nd press injection, (c) is explanatory drawing which shows the 3rd press injection. (D) is a schematic explanatory diagram for explaining the state of pressure to the servomotor at the first to third press-fitting (actually different from this). It is explanatory drawing explaining the clearance gap detection performed at the time of completion | finish of the 2nd press injection of one Embodiment of this invention. (A) is the situation before the end of the second press-fitting and before the start of the gap detection, (b) is the situation where the piston is seated on the end face of the piezo stack, (c) is the situation after the gap is detected (the piston presser 52 rises and the situation has returned to a fourth set pressure P ₄ of the press-fitting punch 51 in FIG. 4 (d)), (d ) is an explanatory diagram showing a status in which the third press-fitted is started. 1 is an overall view of a press-fitting device according to an embodiment of the present invention. 3 is a partial view showing the structure of a press-fit punch 51 and a piston presser 52. FIG. In a gap detection system, it is a figure showing a detection waveform at the time of gap detection. (A) is explanatory drawing explaining the condition where the pipe 3 is elastically deformed by the applied load N in the pipe axial direction. (B) is a graph showing the relationship between the applied load N in the pipe axis direction and the amount of elastic deformation in the pipe axis direction.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. About each embodiment, the same code | symbol is attached | subjected to the part of the same structure, and the description is abbreviate | omitted. Similarly, with respect to the prior art, parts having the same configuration are denoted by the same reference numerals and description thereof is omitted.

  (A) of FIG. 2 is sectional drawing which shows the outline | summary of an injector. (B) is an expanded sectional view which shows the piezoelectric actuator of (a). The injector shown in FIG. 2 (a) incorporates a piezo actuator assembled according to an embodiment of the present invention. FIG. 3A to FIG. 3C are explanatory views for explaining a method of connecting the constituent members of the piezoelectric actuator. The structure and operation of the injector in FIG. 2A are described in Patent Document 1 (essentially the same as that of Patent Document 1), and thus the description thereof is omitted.

  First, the structure of the piezo actuator 1 assembled according to one embodiment of the present invention will be described. The piezo actuator 1 of FIG. 2B assembled according to an embodiment of the present invention is merely an example, and the present invention is not limited to this. Further, the injector in which the piezo actuator 1 assembled according to the embodiment of the present invention is incorporated is not limited to the example of FIG.

A piezoelectric actuator 1 shown in FIG. 2B includes a pipe 3 and a housing 4, and a piston 10 is attached to the pipe 3 via a diaphragm 2. (It is the same as the structure and reference numerals in FIG. 1 described above. For the gap, see FIG. 1B.) In the following description, the piezo actuator 1 shown in FIG. 2B is turned upside down. explain.
As shown in FIG. 3A, the piston 10 is fixed to the diaphragm 2 by laser welding. The diaphragm 2 is razor welded to the pipe 3 at the position shown in FIG. After the pipe 3 is press-fitted into the housing 4, the pipe 3 is razor welded to the housing 4 as shown in FIG. One embodiment of the present invention relates to a process of press-fitting a pipe 3 to which a piston 10 and a diaphragm 2 are fixed by laser welding into a housing 4. When this press-fitting process is completed, the end of the pipe 3 is razor welded to the housing.

FIG. 4 is an explanatory diagram illustrating a press-fitting process according to an embodiment of the present invention. (A) is 1st press injection, (b) is 2nd press injection, (c) is explanatory drawing which shows the 3rd press injection. (D) is a schematic explanatory diagram for explaining the state of pressure to the servomotor at the first to third press-fitting (actually different from this). FIG. 5 is an explanatory diagram illustrating gap detection performed at the end of the second press-fitting according to an embodiment of the present invention. (A) is the situation before the end of the second press-fitting and before the start of the gap detection, (b) is the situation where the piston is seated on the end face of the piezo stack, and (c) is the situation after the gap is detected (piston presser 52 is rises and the situation has returned to a fourth set pressure P ₄ of the press-fitting punch 51 in FIG. 4 (d)), (d ) is an explanatory diagram showing a status in which the third press-fitted is started. FIG. 6 is an overall view of a press-fitting device according to an embodiment of the present invention. FIG. 7 is a partial view showing the structure of the press-fitting punch 51 and the piston presser 52 in FIG.

  FIG. 6 shows an example of a press-fitting device that performs the press-fitting process of the present invention. When rotation of the press-fitting servo motor 30 is transmitted to the ball screw 40 by belt electric drive, the central pressing portion 50 is linearly driven along the guide 31. The central pressing unit 50 is provided with a pulse motor (not shown). FIG. 7 shows an enlarged view of the press-fitting punch 51 provided in the central pressing portion 50. In FIG. 7, the pipe 3 is held by the pipe subassembly chuck 32 shown in FIG. 6 (not shown in FIG. 7). The piston presser 52 is a pulse motor installed in the central pressing unit 50 and is driven independently of the servomotor with respect to the press-fit punch 51 provided in the central pressing unit 50 driven by the servomotor. (The piston presser 52 is suspended independently from the press-fit punch 51).

  The piston presser 52 presses the mountain-shaped top portion 10 ′ of the piston 10. The piston 10 is fixed to the pipe 3 by the diaphragm 2. When the piston presser 52 moves in the axial direction of the piston presser, the piston 10 elastically supported by the diaphragm 2 is moved in the axial direction of the pipe 3.

With reference to FIGS. 4 and 5, the press-fitting process of one embodiment of the present invention will be described.
The press-fitting process of one embodiment of the present invention basically includes 1-3 press-fitting processes. In the first press-fitting process (first press-fitting process) shown in FIG. 4A, the servomotor is driven and the press-fit punch 51 (the piston presser 52 does not operate) to press-fit the pipe 3 into the housing 4. At this time, the pipe 3 and the housing 4 are preliminarily press-fitted so as to be temporarily fixed so that at least a gap (a suitable amount of space) is generated between the piston 10 and the piezo stack 5 based on the material dimensions of each member. This press-fitting is positioned as aiming at temporary fixing of the pipe 3 and the housing 4 to the last. Let P _{1 be} the final pressure of the press-fitting punch 51 in the first press-fitting process.

Next, the pressure P at which the press-fitting punch 51 presses the pipe 3 is dropped to about 1/10 to 1/100 of P ₁ (P ₂ ) and then enters the second press-fitting process (second press-fitting process). . The pressure P ₂ is not may be other any pressure. In the second press-fitting process shown in FIG. 4B, the position is controlled so that the pipe 3 is press-fitted into the housing 4 by about 0.05 mm as an example. Press fitting punch 51 at 0.05mm advanced position as the target value is stopped and the pressure P at that time and P _3. The target value of 0.05 mm should be determined as a predetermined amount as appropriate.

After the press-fitting punch 51 is stopped, gap detection is performed by the gap detection system shown in FIG. 5 (gap detection step). This gap detection system will be described next. In a state where the press-fitting punch 51 is stopped and the pressure P at which the press-fitting punch 51 presses the pipe 3 is maintained at P ₃ , the piston presser 52 starts to move from the zero point position by the pulse motor, and the piston 10 The position at which the piezo stack 5 is seated is measured. The distance between the seating position and the zero point position is the gap amount x (first gap amount) between the end face of the piezo stack 5 and the piston 10. For the gap detection system that measures the position where the piston 10 is seated on the end face of the piezo stack 5, the piezoelectric effect of the piezo may be used. FIG. 8 is a diagram illustrating a detection waveform when a gap is detected in the gap detection system. In addition, in order to detect the time point when the piston 10 is seated on the end face of the piezo stack 5, it may be appropriately performed by a known technique.

  When the piston 10 is lowered by the pulse motor and seated on the piezo stack 5 as shown in FIG. 5B, a change in voltage per unit time is observed due to the piezoelectric effect of the piezo. A point in time when there is a predetermined voltage change amount ΔV (for example, 10 mV / 10 msec) is detected as a position where the piston 10 is seated on the piezo stack 5 (see FIG. 8). The gap amount x can be calculated from the position before the pulse motor descends (zero point position) and the position data (sitting position) of the pulse motor stopped when the piezo voltage change amount ΔV reaches a predetermined value. .

After the gap detection process by the gap detection system is finished, as shown in FIG. 4D, the pressure P _{4 at} which the press-fitting punch 51 presses the pipe 3 is lowered to about 100 Pa, and the third press-fitting process ( The third press-fitting step is entered. In order not to make the relationship between the pipe 3 and the housing 4 unstable, the pressure P ₄ is not set to zero but about 100 Pa, and the pressure P ₄ may be any other pressure. When the press-fitting is completed and the load is released, the bulge returns due to the elastic deformation of the pipe, and the gap amount increases and changes. This is because the pipe 3 swells in a barrel shape during press-fitting and elastic deformation occurs. FIG. 9A is an explanatory diagram illustrating a situation in which the pipe 3 is elastically deformed by the applied load N in the pipe axial direction. (B) is a graph showing the relationship between the applied load N in the pipe axis direction and the amount of elastic deformation in the pipe axis direction.

As shown in FIG. 9 (a), the press-fitting is opened the load P ₃ ended, when the bulge barrel-shaped pipes had returned by elastic deformation, the elastic deformation amount of the pipe 3 and y . This y is also referred to as an insufficient press-fitting amount. As shown in FIG. 9B, the relationship between the applied load N in the pipe axis direction and the amount of elastic deformation in the pipe axis direction is experimentally known (it can also be calculated by calculation). Therefore, if the applied load N in the pipe axial direction is known, the elastic deformation amount of the pipe 3 can be obtained. The relationship between the applied load N in the pipe axis direction and the amount of elastic deformation in the pipe axis direction may be approximated by a linear expression such as the following expression. In this case, information processing becomes easy.
Press-in insufficient amount y = α * P ₃
α: Coefficient (value calculated from experimental data)

In the third press-fitting, this press-fitting insufficient amount y is calculated based on the applied load N (P ₃ , P _{4 in} this embodiment) and the actual data of the deformation amount as shown in FIG. As in the second time, the outer periphery of the diaphragm is pressed by a servo motor, the correction amount is added, and the pressure is further advanced by a predetermined amount (0.05 mm). In this case, the pressing amount ΔX by the servo motor is ΔX = x + y + 0.05. Thereby, when the pipe 3 is covered, the pipe 3 is hermetically sealed, and the pipe 3 can be press-fitted into the housing 4 without a gap even when the gap inside is not visible. When this press-fitting process is completed, the end of the pipe 3 is razor welded to the housing 4 as shown in FIG.

  So far, when the pipe is covered, it will be sealed, so the gap in the inside will be visible, and the gap amount could not be set accurately, but according to this embodiment, the press-fitting process without causing a gap defect It can be performed.

As another embodiment of the present invention, the following modifications can be considered.
The first press-fitting and the second press-fitting may be combined into one, and P ₁ = P ₂ = P ₃ as shown by the dotted line in FIG. In this case, the press-fitting process can be simplified. If the pipe 3 and the housing 4 are temporarily fixed in the previous process, the first press-fitting process can be omitted. In the above-described embodiment of the present invention, in the second and third press-fitting, the press-fitting is performed by 0.05 mm. However, it is needless to say that the numerical value is not limited to this value and may be zero.

In the above description, the press-fitting method has been described, but the following press-fitting device is also included as an embodiment of the present invention.
A press-fitting device for a piezo actuator that press-fits a pipe 3 to which a piston 10 is attached via a diaphragm 2 into a housing 4 having a piezo stack 5. The press-fitting punch 51 driven by a servo motor presses the pipe 3. A press-fitting device for a piezo actuator that is independently suspended from the press-fitting punch 51 and driven by a pulse motor, wherein the press-fitting punch 51 is interposed between the piston 10 and the piezo stack 5. The pipe 3 is preliminarily press-fitted into the housing 4 so that the gap is appropriately maintained, and further, the pipe 3 is press-fitted into the housing 4 by a predetermined amount, and after the press-fitting pressure P ₃ of the pipe 3 after the predetermined amount of press-fitting. , The gap x generated between the piston 10 and the piezo stack 5 is By moving 52, wherein detecting a gap x, to release the injection pressure P ₃ of the pipe 3, and the gap x, the axial direction of the pipe 3 by opening the injection pressure P ₃ of the pipe 3 In consideration of the amount of elastic deformation, the pipe 3 is controlled to be further press-fitted into the housing (4). The press-fitting device has a control unit that controls the operation.

  In the above description, the piezoelectric actuator has been described as an example. However, the present invention is not limited to this, and the press-fitting method or apparatus of the present invention can be applied to other methods.

1 Piezo Actuator 2 Diaphragm 3 Pipe 4 Housing 5 Piezo Stack 10 Piston 51 Press-In Punch 52 Piston Press

Claims (3)

The pipe (3) to which the piston (10) is attached via the diaphragm (2) is pressed by a press-fitting punch (51) driven by a servo motor, and press-fitted into a housing (4) having a piezo stack (5). A press-fitting method for a piezo actuator,
A first press-fitting step of pre-pressing the pipe (3) into the housing (4) so that an appropriate gap is maintained between the piston (10) and the piezo stack (5);
Further, the pipe (3) is press-fitted into the housing (4) by a predetermined amount, and the piston (10) and the piezo stack (5) are inserted under the press-fitting pressure (P3) of the pipe (3) after the predetermined amount of press-fitting. A second press-fitting step having a gap detecting step of detecting a first gap amount (x) generated during
The clearance detecting step, wherein the independent suspension into the press punch (51), said piston retainer moves the piston presser (52) which is driven (52) by the pressing to Rukoto the piston (10) by the pulse motor, The position of the piston retainer (52) until the piston (10) is seated on the end face of the piezo stack (5) after the piston retainer (52) starts moving from the zero point position by the pulse motor. Is configured to measure and detect the first gap amount (x),
After the gap detection step, the first pressurization pressure (P3) of the pipe (3) is released, and then the first gap amount (x) detected in the gap detection step and the press-fitting of the pipe (3) are detected. A third press-fitting step of press-fitting the pipe (3) into the housing (4) in consideration of the amount of elastic deformation in the axial direction of the pipe (3) due to the release of the pressure (P3). Press-in method for piezo actuators.   The predetermined amount of press-fitting in the second press-fitting step is zero, and the press-fitting pressure (P3) in the second press-fitting step is equal to the press-fitting pressure in the first press-fitting step. Item 2. A press-fitting method for a piezo actuator according to Item 1. A piezoelectric actuator press-fitting device for press-fitting a pipe (3) to which a piston (10) is attached via a diaphragm (2) into a housing (4) having a piezo stack (5),
A press-fitting punch (51) driven by a servo motor for pressing the pipe (3);
In a press-fitting device for a piezo actuator, comprising a piston presser (52) suspended independently from the press-fitting punch (51) and driven by a pulse motor,
The press-fitting punch (51) preliminarily press-fits the pipe (3) into the housing (4) so that an appropriate gap is maintained between the piston (10) and the piezo stack (5),
Further, the pipe (3) is press-fitted into the housing (4) by a predetermined amount, and the piston (10), the piezo stack (5), and the pipe (3) are pressed under the press-fitting pressure (P3) of the pipe (3). the gap (x) that occurred during, by the piston retainer (52) is pressed to Rukoto the piston (10) moving said piston retainer (52), said piston retainer (52), the zero point position Measure the position of the piston presser (52) until the piston (10) is seated on the end face of the piezo stack (5) after starting to move by the pulse motor, and detect the gap (x) And
Release the press-fitting pressure (P3) of the pipe (3),
Considering the gap (x) and the amount of elastic deformation in the axial direction of the pipe (3) due to the release of the press-fitting pressure (P3) of the pipe (3), the pipe (3) is accommodated in the housing (4). And a press-fitting device for a piezo-actuator, which is controlled to be further press-fitted.