JP2009057939A - Piezoelectric element sealing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability of a diaphragm by reducing a per-unit load on a diaphragm. <P>SOLUTION: The piezoelectric element 10 of the piezoelectric element sealing structure A is surrounded and sealed by a sleeve 8, a piezoelectric element base part 7, a piezoelectric element head 9, and a cluster 11 of diaphragms which are provided with a plurality of diaphragms 110, 111, each of which is arranged so that it can exert elastic action. The outer peripheral parts 110b, 111b and the inner peripheral parts 110a, 111a of respective the diaphragms 110, 111 are fixed to each other by sealing weld (B), and the outer peripheral part 110b of the diaphragm 110 on the tip side of the cluster 11 of diaphragms is fixed on the inner peripheral side of the sleeve 8 by the sealing weld (B). Then the outer peripheral part 111b of the diaphragm 111 on the base end side of the cluster 11 of diaphragms is fixed to the projection 9b on the tip side of the outer peripheral part 9a of the piezoelectric element head 9 by the sealing weld (B). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric element sealing structure, and is suitable for a piezoelectric element sealing structure as a drive unit of an injector of a common rail fuel injection device for automobiles.

  Recently, common rail fuel injection devices with excellent characteristics have been put into practical use as fuel injection devices for automobile engines, and environmental measures, high-pressure injection, miniaturization, etc. are used as the driving source of injectors that are components of fuel injection devices. From the viewpoint, a multilayer piezoelectric element is used.

  A fuel injection valve using a piezoelectric element is provided with a piezoelectric element sealing structure that brings the piezoelectric element into a non-contact state from a fuel that has a functional adverse effect for protecting the function of the piezoelectric element.

  This piezoelectric element sealing structure requires a structure that allows expansion and contraction of the piezoelectric element because the piezoelectric element expands and contracts in the stacking direction during the operation of the injector. A structure using a bellows has been used as a structure that allows expansion and contraction of the piezoelectric element. However, a structure using a bellows has a problem that the physique becomes large. From the viewpoint of downsizing and high responsiveness, Patent Document 1 below. As described, a piezoelectric element sealing structure using a diaphragm has been used.

  In the piezoelectric element sealing structure using a diaphragm as described in Patent Document 1 below, the diaphragms (10 in FIG. 1, 21 in FIG. 3, 31 in FIG. 4, 41 in FIG. 6, 41 in FIG. 7) are: Since it is a single plate, that is, a single plate, the single plate diaphragm bears the total amount of expansion and contraction of the piezoelectric element, and a large force acts on the single plate diaphragm with high vibration.

Since the diaphragm is thin and usually curved, if a large vibrational force is applied due to variations in the processing accuracy of the diaphragm, there is a risk of problems such as cracks in the diaphragm. A single-plate diaphragm was used. The piezoelectric element sealing structure described in Patent Document 1 below also has a problem in durability.
JP 2005-533968 A

  The present invention has been made in view of the above points. In the piezoelectric element sealing structure, a diaphragm group structure including a plurality of diaphragms is used, and the entire expansion and contraction amount of the piezoelectric element is shared and borne by each diaphragm. The purpose is to improve the durability of the diaphragm by reducing the load on the diaphragm per sheet.

In the invention according to claim 1, the piezoelectric element, the sleeve disposed on the outer periphery of the piezoelectric element, the piezoelectric element base attached in contact with the proximal end side of the piezoelectric element, and the driving direction of the piezoelectric element A piezoelectric element head attached to the distal end side, and a diaphragm group fixed to the sleeve and the piezoelectric element head,
A piezoelectric element sealing structure in which the piezoelectric element is surrounded and sealed by the sleeve, the piezoelectric element base, the piezoelectric element head, and a group of diaphragms;
The diaphragm group includes a plurality of diaphragms, the diaphragms are arranged so as to exert an elastic action, and the outer peripheral part and the inner peripheral part of each diaphragm are sealed and fixed to each other, and the distal end side of the diaphragm group The outer peripheral part of the diaphragm is sealed and fixed to the sleeve, and the outer peripheral part of the base side diaphragm in the diaphragm group is fixed and sealed to the piezoelectric element head.

  According to the above configuration, the load applied to the diaphragm group applied by the operation of the piezoelectric element can be shared by a plurality of diaphragms. Therefore, the load per diaphragm can be reduced, and the diaphragm thickness and the curvature can be reduced when the diaphragm is manufactured. Even if variations such as shape occur, it is possible to prevent the occurrence of cracks and the like due to repetitive loads resulting from this variation, and it is possible to improve durability.

  In the invention according to claim 2, the seal fixing of the outer peripheral portion of the front end side diaphragm to the sleeve is performed by fixing the outer peripheral portion of the front end side diaphragm to the inner peripheral side of the sleeve from the outer peripheral side of the sleeve. It is characterized by that.

  According to the above configuration, since the welding is performed from the outer peripheral side of the sleeve larger than the thickness of the diaphragm, the diaphragm is melted into the sleeve having a large heat capacity, and the diaphragm can be reliably welded to the sleeve.

  According to a third aspect of the present invention, the diaphragm group includes an even number of diaphragms, and seal fixing of the outer peripheral portion of the base end side diaphragm to the piezoelectric element head is performed when the outer peripheral portion of the base end side diaphragm is the piezoelectric element. It is characterized by being fixed by welding at the outer periphery of the head.

  According to the above configuration, since the diaphragm group is composed of an even number of diaphragms, the load per diaphragm can be reduced, and the outer peripheral portion of the base side diaphragm is positioned on the outer peripheral portion of the piezoelectric element head. The base end diaphragm and the piezoelectric element head can be welded and fixed on the outer peripheral portion of the piezoelectric element head, and welding is easy.

  The invention according to claim 4 is characterized in that the diaphragm group has an even number of diaphragms, and an outer peripheral portion of the base end side diaphragm is welded and fixed to an inner peripheral side of the outer peripheral portion of the piezoelectric element head. .

  According to the above configuration, in addition to the effect of reducing the load per diaphragm and facilitating welding, welding fixing between the base end diaphragm and the piezoelectric element head is performed on the inner peripheral side of the outer peripheral portion of the piezoelectric element head. Therefore, the base end diaphragm can be easily welded and the base end diaphragm is melted into the piezoelectric element head having a large heat capacity, so that the base end diaphragm can be reliably welded to the piezoelectric element head.

  The invention according to claim 5 is characterized in that the diaphragm group has an odd number of diaphragms, and an inner peripheral portion of the base end side diaphragm is welded and fixed to a central inclined portion of the piezoelectric element head.

  According to the above configuration, in addition to reducing the load per diaphragm by configuring the diaphragm group with an odd number of diaphragms, the inner peripheral portion of the base side diaphragm is inclined at the central portion of the piezoelectric element head. In the seal welding fixing, the lap length between the inner peripheral portion of the base end diaphragm and the central portion of the piezoelectric element head can be taken, and good seal welding B can be performed.

  The invention according to claim 6 is characterized in that the diaphragms of the diaphragm group are arranged in a warped shape in which the curved shapes of the diaphragms are reversed from each other.

 According to the above configuration, the mutual elastic repulsive force is strong and can sufficiently cope with the expansion and contraction driving of the piezoelectric element 10.

  The invention according to claim 7 is characterized in that the diaphragms of the diaphragm group are arranged in a warped shape in which the curved shapes of the diaphragms are the same direction.

  According to the said structure, the height can be made small compared with the diaphragm of the curvature shape reversed mutually, and a physique can be reduced in size while maintaining an elastic force.

  Hereinafter, embodiments of a piezoelectric element sealing structure according to the present invention will be described with reference to the drawings. 1 and 2, an overall structure and a main part of an injector of an automobile fuel injection device having a piezoelectric element sealing structure of the present invention will be described.

  The injector 1 includes a drive unit 2 including the piezoelectric element sealing structure A of the present invention, a connector unit 3 that supplies power to the drive unit 2, a fuel control unit 4 that is controlled by the drive unit 2, and a fuel control unit 4 that injects fuel. A fuel injection unit 5 is provided. The drive unit 2 is accommodated in the injector body 6. In the description, as shown in the figure, the “tip side” means the fuel injection part 5 side, and the “base end side” means the connector part 3 side.

  The piezoelectric element sealing structure A of the present invention includes a piezoelectric element base 7 that is secretly attached on the proximal end side of the injector body 6, a cylindrical sleeve 8 that is secretly joined on the proximal end side of the piezoelectric element base 7, A piezoelectric element head 9 disposed on the distal end side in the sleeve 8, a laminated piezoelectric element 10 composed of a plurality of piezoelectric element chips disposed in pressure contact between the piezoelectric element base 7 and the piezoelectric element head 9; A diaphragm group 11 secretly sealed to the sleeve 8 and the piezoelectric element head 9 is provided on the distal end side of the sleeve 8, and a sealed space is formed by the piezoelectric element base 7, the sleeve 8, the piezoelectric element head 9, and the diaphragm group 11. And the piezoelectric element 10 is arrange | positioned in this sealed space, and the non-contact state is maintained from the fuel for the function protection.

  The tip 90 of the piezoelectric element head 9 is in contact with the piezoelectric element head receiver 12, the piezoelectric element head receiver 12 is in contact with the piston 13, and the expansion of the piezoelectric element 10 is via the piezoelectric element head 9 and the piezoelectric element head receiver 12. Then, the piston 13 is pushed down toward the tip side to control the fuel.

  Next, the piezoelectric element sealing structure A of the present invention will be described in detail with reference to FIGS. Each of the drawings shows an enlarged structure of the sleeve 8, the piezoelectric element head 9, and the diaphragm group 11, which are the main parts of the piezoelectric element sealing structure A of the present invention.

  3 to 8 show the state of the diaphragm group 11 having an even number of diaphragms, FIGS. 3 to 6 show the state of two diaphragms, and FIGS. 7 and 8 show the state of four diaphragms. . 9 and 10 show the state of three diaphragms in the state of the diaphragm group 11 provided with an odd number of diaphragms.

  First, the diaphragm group 11 having two diaphragms will be described. In FIG. 3, the diaphragm group 11 includes two diaphragms, a distal end side diaphragm 110 and a proximal end side diaphragm 111. Each diaphragm is formed to have an elastic (spring) action in a curved shape by pressing a thin stainless steel plate. A through hole through which the distal end portion 90 of the piezoelectric element head 9 is inserted is formed at the center of both the distal end side diaphragm 110 and the proximal end side diaphragm 111.

 The distal end side diaphragm 110 and the proximal end side diaphragm 111 formed in a curved shape are alternately arranged so as to be in a warped state in which the directions of the curves are reversed. That is, the bending direction of the distal end side diaphragm 110 protrudes toward the proximal end side, and the bending direction of the proximal end side diaphragm 111 protrudes toward the distal end side so as to repel each other. The degree of bending is variously set, and an appropriate bending shape may be set in consideration of the material, plate thickness, size, and the like.

  The distal end side diaphragm 110 and the proximal end side diaphragm 111 are fixed to the sleeve 8 and the piezoelectric element head 9 as follows.

  First, the inner peripheral portions 110a and 111a of the distal end side diaphragm 110 and the proximal end side diaphragm 111 that are alternately arranged as shown in the figure are sealed and fixed in a circumferential (entire circumference) shape by laser welding B.

  Next, the distal end side diaphragm 110 and the diaphragm group 11 of the proximal end side diaphragm 111 which are sealed and fixed by the inner peripheral portions 110a and 111a are set in the piezoelectric element head 9 so that the distal end portion 90 of the piezoelectric element head 9 is inserted, The outer peripheral portion 111b of the base end side diaphragm 111 and the distal end side protruding portion 9b of the outer peripheral portion 9a of the piezoelectric element head 9 are sealed and fixed in a circumferential shape (entire circumference) by laser welding B. In this case, the piezoelectric element head 9 is sealed and fixed in a state where it is taken out from the sleeve 8.

  Next, the piezoelectric element head 9 and the diaphragm group 11 are set in the sleeve 8, and the outer peripheral portion 110 b of the distal end side diaphragm 110 is attached to the sleeve 8 in a state where the piezoelectric element head 9 is pushed up to the proximal end side (preload is applied). The seal is fixed to the circumference (entire circumference) by laser welding B. As a result, a sealed space is formed in the sleeve 8 by sealing the outer peripheral portion 110 b of the distal end side diaphragm 110 and the outer peripheral portion 111 b of the proximal end side diaphragm 111 to the sleeve 8 and the piezoelectric element head 9.

  Laser welding seal fixation between the outer peripheral portion 111 b of the base end side diaphragm 111 and the piezoelectric element head 9 is performed from the outside of the distal end side protruding portion 9 b of the outer peripheral portion 9 a of the piezoelectric element head 9. In addition, laser welding seal fixing between the outer peripheral portion 110 b of the distal end side diaphragm 110 and the sleeve 8 is also performed from the outside of the sleeve 8. This is performed by irradiating a laser beam from the outside of the sleeve 8 and the piezoelectric element head 9 having a larger heat capacity than the distal end diaphragm 110 and the proximal end diaphragm 111, and the sleeve 8 and the piezoelectric element head heated to a high temperature with a large amount of heat. 9, welding is performed in a state where the outer peripheral portion 110 b of the distal end side diaphragm 110 and the outer peripheral portion 111 b of the proximal end side diaphragm 111 are sucked and absorbed in the meat portion, and a strong seal is fixed over the entire circumference. Is called.

  When the seal fixing of the distal end side diaphragm 110 and the proximal end side diaphragm 111 is completed, a free state is established, and the preload is removed, and a load in the distal end direction acts on the distal end side diaphragm 110 and the proximal end side diaphragm 111 as a reaction. However, this load is offset by the fuel pressure at the time of injector operation acting on the outer side of the distal diaphragm 110 in the proximal direction, thereby maintaining a balance.

  The diaphragm group 11 sealed and fixed to the sleeve 8 and the piezoelectric element head 9 in this way has an elastic action, enables the piezoelectric element 10 to expand and contract, forms a sealing structure, and exhibits the function of an injector.

  Due to the repeated expansion and contraction action of the piezoelectric element 10, repeated expansion and contraction stress is generated in the diaphragm group 11, but the repeated expansion and contraction stress is borne by the two diaphragms of the distal end side diaphragm 110 and the proximal end side diaphragm 111. Because the burden is halved compared to the diaphragm structure of this type, even if there is a variation in the diaphragm thickness, curved shape, etc. during the fabrication of the diaphragm, it is possible to prevent the occurrence of cracks due to repeated loads due to this variation, and durability Can be improved.

  Further, if the diaphragm group 11 is composed of an even number of diaphragms, the outer peripheral portion 111b of the base end side diaphragm 111 can be positioned on the outer peripheral portion 9a of the piezoelectric element head 9, and accordingly, the outer peripheral portion 111b of the base end side diaphragm 111 can be positioned. The seal welding B between the piezoelectric element head 9 and the piezoelectric element head 9 can be easily performed.

  FIG. 4 is a modification of the shape of the portion where the outer peripheral portion 111 b of the base end side diaphragm 111 is fixed to the outer peripheral portion 9 a of the piezoelectric element head 9 with respect to the embodiment shown in FIG. 3. The portion of the outer peripheral portion 9a for fixing the seal is a circumferential flange portion 9c extending radially in the outer peripheral portion 9a. Laser seal welding is also performed from the side (upper side in the drawing) where the outer peripheral portion 111b of the base end side diaphragm 111 is not located in the circumferential flange portion 9c for the reason described above. In such a structure, it is easy to press the base end side diaphragm 111 simply by bending the front end of the outer peripheral portion 111b of the base end side diaphragm 111 to the base end side. About the structure of another part, it is the same as that of the example shown in FIG. 3, and exhibits the same effect.

  FIG. 5 is a modified example of the portion where the outer peripheral portion 111 b of the base end side diaphragm 111 is sealed to the outer peripheral portion 9 a of the piezoelectric element head 9 with respect to the embodiment shown in FIGS. 3 and 4. The portion of the outer peripheral portion 9a for fixing the seal is the outer peripheral side portion 9d of the outer peripheral portion 9a. Laser seal welding is performed from the outside of the outer peripheral portion 111b of the base end side diaphragm 111 in the outer peripheral side portion 9d.

 In such a structure, the outer peripheral portion 9 of the piezoelectric element head 9 may have a simple shape, and since the side length of the outer peripheral side portion 9d can be increased, the outer peripheral portion 111b of the proximal end side diaphragm 111 and The adhesion strength can be secured. About the structure of another part, it is the same as that of the example shown in FIG. 3, FIG. 4, and exhibits the same effect.

  FIG. 6 shows an example in which the curved shape of the proximal diaphragm 111 is changed with respect to the embodiment shown in FIGS. 3, 4, and 5. The curved shapes of the distal end side diaphragm 110 and the proximal end side diaphragm 111 shown in FIGS. 3, 4, and 5 are alternately arranged so as to be in a warped state in which the directions of bending are reversed, but are shown in FIG. The curved shape of the proximal end side diaphragm 111 exhibits a curved shape that warps in the same direction as the curved warp of the distal end side diaphragm 110. Also in this case, the base end side diaphragm 111 has an elastic action, and exhibits the elastic action as the diaphragm group 11 in combination with the front end side diaphragm 110.

 In such a structure, the elastic force of the base end side diaphragm 111 is slightly smaller than that of the base end side diaphragm 111 shown in FIGS. 3, 4, and 5, but the height of the base end side diaphragm 111 is reduced. As a whole, the diaphragm group 11 can be reduced in size. About the structure of another part, it is the same as that of the example shown in FIG. 5, and substantially the same effect is exhibited.

 The shape of the outer peripheral portion 9 of the piezoelectric element head 9 was the same as the shape having the outer peripheral side portion 9d shown in FIG. 5, but the shape of the outer peripheral portion 9 was changed to the tip side protruding portion 9b shown in FIG. The shape of the circumferential flange portion 9c shown in FIG. 6 may be used, and if the shape of the tip side protruding portion 9b or the circumferential flange portion 9c is satisfactory, a good laser seal from the outside of the outer circumferential portion 9 of the piezoelectric element head 9 as described above can be obtained. It may be fixed by welding.

  FIG. 7 shows an example in which four diaphragms are provided as the diaphragm group 11. In this structure, two intermediate diaphragms 112 and 113 are arranged between the distal diaphragm 110 and the proximal diaphragm 111. The four diaphragms 110, 111, 112, 113 are alternately arranged so as to be in a warped state in which the directions of bending are reversed. That is, they are arranged so as to repel each other. The material, plate pressure, formation method, etc. of each diaphragm are the same as those described in FIG.

  These four diaphragms are first fixed by laser welding B sealing at the inner peripheral portion 110a of the front diaphragm 110 and the inner peripheral portion 112a of the intermediate diaphragm 112, and the outer peripheral portion 112b of the intermediate diaphragm 112 and the outer peripheral portion of the intermediate diaphragm 113. The laser welding B seal is fixed at 113b, and the circumferential (full circumference) seal is fixed by laser welding B at the inner peripheral portion 113a of the intermediate diaphragm 113 and the inner peripheral portion 111a of the proximal end side diaphragm 111.

  Next, the distal end portion 90 of the piezoelectric element head 9 is inserted through the series of four diaphragm groups 11 that are sealed in this manner, and the outer peripheral portion 111b of the base end side diaphragm 111 and the outer peripheral portion 9a of the piezoelectric element head 9 are inserted. A circumferential (all circumference) seal is fixed by laser welding B at the outer peripheral side portion 9d.

  Next, the four diaphragm groups 11 fixed with the seal are set on the piezoelectric element head 9 so that the distal end portion 90 of the piezoelectric element head 9 is inserted, and the outer peripheral portion 111b of the proximal end side diaphragm 111 and the piezoelectric element head 9 are set. The outer peripheral side 9d of the outer peripheral portion 9a is sealed and fixed in a circumferential (entire) shape by laser welding B. In this case, the piezoelectric element head 9 is sealed and fixed in a state where it is taken out from the sleeve 8.

  Next, the piezoelectric element head 9 and the four diaphragm groups 11 are set in the sleeve 8, and the outer peripheral portion 110 b of the distal end side diaphragm 110 is moved in a state where the piezoelectric element head 9 is pushed up to the proximal end side (preloading is applied). The sleeve 8 is sealed with a laser welding B in a circumferential (entire) shape. As a result, the inside of the sleeve 8 forms a sealed space by mutual sealing and fixing by the distal end side diaphragm 110, the intermediate diaphragms 112 and 113, the proximal end side diaphragm 111, the sleeve 8 and the piezoelectric element head 9.

  When the distal end diaphragm 110, the intermediate diaphragms 112 and 113, the proximal end diaphragm 111, the sleeve 8 and the piezoelectric element head 9 complete the mutual sealing and fixing, the preload is removed and the diaphragm group 11 has a distal direction as a reaction. The load of acts. However, the load is offset by the fuel pressure during the operation of the injector in the base end direction outside the front end diaphragm 110 to maintain a balance.

  In this way, the four diaphragm groups 11 which are sealed and fixed to the sleeve 8 and the piezoelectric element head 9 have an elastic action, enable the piezoelectric element 10 to expand and contract, form a sealing structure, and function as an injector. To do.

 Due to the repeated expansion and contraction action of the piezoelectric element 10, repeated expansion and contraction stress is generated in the four diaphragm groups 11, but the repeated expansion and contraction stress is borne by the four diaphragms 110, 112, 113, and 111. Since the burden is reduced by a factor of 4 compared to the diaphragm structure, even if there is a variation in the diaphragm thickness, curved shape, etc. during the fabrication of the diaphragm, it is possible to prevent the occurrence of cracks, etc. due to repeated loads due to this variation. And the durability can be greatly improved.

  FIG. 8 shows an example in which the curved shapes of the intermediate diaphragms 112 and 113 and the proximal diaphragm 111 are changed with respect to the embodiment shown in FIG. The curved shapes of the distal end side diaphragm 110, the intermediate diaphragms 112 and 113, and the proximal end side diaphragm 111 shown in FIG. 7 are all arranged in a staggered manner so that the curved directions are reversed with respect to each other. The curved shapes of the intermediate diaphragms 112 and 113 and the proximal end side diaphragm 111 shown in FIG. 3 are curved in the same direction as the curved warp of the distal end side diaphragm 110. Also in this case, the intermediate diaphragms 112 and 113 and the proximal end side diaphragm 111 have an elastic action, and together with the distal end side diaphragm 110, the elastic action as the diaphragm group 11 is exhibited.

  In such a structure, the elastic forces of the intermediate diaphragms 112 and 113 and the proximal diaphragm 111 are slightly smaller than those of the intermediate diaphragms 112 and 113 and the proximal diaphragm 111 shown in FIG. The height of the base end side diaphragm 111 can be reduced, and the diaphragm group 11 can be downsized as a whole. About the structure of another part, it is the same as that of the example shown in FIG. 7, and substantially the same effect is exhibited.

  In the embodiment shown in FIGS. 7 and 8, the shape of the outer peripheral portion 9a of the piezoelectric element head 9 is the same as the shape having the outer peripheral side portion 9d shown in FIGS. The shape may be the shape of the distal end side protruding portion 9b shown in FIG. 3 or the circumferential flange portion 9c shown in FIG. 4, and the piezoelectric element as described above may be used as long as the shape is the distal end side protruding portion 9b or the circumferential flange portion 9c. Good laser seal welding and fixing from the outside of the outer peripheral portion 9 of the head 9 may be performed.

  FIG. 9 shows an example in which three diaphragms are provided as the diaphragm group 11. This is a structure in which one intermediate diaphragm 112 is disposed between the distal end side diaphragm 110 and the proximal end side diaphragm 111. The three diaphragms 110, 111, and 112 all have a through hole at the center, and are arranged in a staggered manner so that the curvature directions are reversed. That is, they are arranged so as to repel each other. The material, plate pressure, formation method, etc. of each diaphragm are the same as those described in FIG.

  These three diaphragms are first sealed and fixed by laser welding B at the inner peripheral portion 110a of the distal diaphragm 110 and the inner peripheral portion 112a of the intermediate diaphragm 112, and the outer peripheral portion 112b of the intermediate diaphragm 112 and the proximal diaphragm 111 are fixed. A circumferential (full circumference) seal is fixed by laser welding B at the outer peripheral portion 111b.

  Next, the distal end portion 90 of the piezoelectric element head 9 is inserted through the series of three diaphragm groups 11 that are sealed and fixed in this manner, so that the inner peripheral portion 111a of the proximal end diaphragm 111 and the central portion of the piezoelectric element head 9 are inserted. A circumferential (all circumference) seal is fixed by laser welding B at the inclined portion 9e.

  Next, the three diaphragm groups 11 which are sealed and fixed are set on the piezoelectric element head 9 so that the distal end portion 90 of the piezoelectric element head 9 is inserted, and the inner peripheral portion 111a of the proximal end side diaphragm 111 and the piezoelectric element head are set. 9 is fixed to the circumference (entire circumference) by laser welding B at an inclined portion 9e at the center portion of 9. In this case, the piezoelectric element head 9 is sealed and fixed in a state where it is taken out from the sleeve 8.

  Next, the piezoelectric element head 9 and the three diaphragm groups 11 are set in the sleeve 8, and the outer peripheral portion 110 b of the distal end side diaphragm 110 is moved in a state where the piezoelectric element head 9 is pushed up to the proximal end side (applying preload). The sleeve 8 is fixed by a laser welding B in a circumferential (entire) shape. As a result, a sealed space is formed in the sleeve 8 by mutual sealing and fixing by the distal end side diaphragm 110, the intermediate diaphragm 112, the proximal end side diaphragm 111, the sleeve 8, and the piezoelectric element head 9.

  When the seal fixing by the distal diaphragm 110, the intermediate diaphragm 112, the proximal diaphragm 111, the sleeve 8 and the piezoelectric element head 9 is completed, a free state is obtained, and the preload is removed and the diaphragm group 11 is loaded in the distal direction as a reaction. Works. However, the load is offset by the fuel pressure during the operation of the injector in the base end direction outside the front end diaphragm 110 to maintain a balance.

  In this way, the three diaphragm groups 11 sealed and fixed to the sleeve 8 and the piezoelectric element head 9 have an elastic action, enable the piezoelectric element 10 to expand and contract, form a sealing structure, and function as an injector. To do.

  The repeated expansion / contraction action of the piezoelectric element 10 causes repeated expansion / contraction stress in the three diaphragm groups 11. However, since the repeated expansion / contraction stress is borne by the three diaphragms 110, 112, 111, the conventional single diaphragm structure Since the burden is reduced to one-third compared to the above, even if there is a variation in the thickness of the diaphragm, the curved shape, etc. during the fabrication of the diaphragm, it is possible to prevent the occurrence of cracks due to repeated loads due to this variation. , Durability can be greatly improved.

  Further, if the diaphragm group 11 is composed of an odd number of diaphragms, the inner peripheral portion 111a of the base end side diaphragm 111 can be positioned at the central portion inclined portion 9e of the piezoelectric element head 9, and accordingly, the base end side diaphragm The wrap length between the inner peripheral portion 111a of the 111 and the piezoelectric element head 9 can be sufficiently taken, and the seal welding B between the inner peripheral portion 111a of the proximal end side diaphragm 111 and the piezoelectric element head 9 can be easily performed.

  FIG. 10 shows an example in which the curved shapes of the intermediate diaphragm 112 and the base end side diaphragm 111 are changed with respect to the embodiment shown in FIG. 9. The curved shapes of the distal end side diaphragm 110, the intermediate diaphragm 112 and the proximal end side diaphragm 111 shown in FIG. 9 are alternately arranged so as to be in a warped state in which the curved directions are reversed with respect to each other. The curved shapes of the intermediate diaphragm 112 and the proximal-side diaphragm 111 are curved in the same direction as the curved curvature of the distal-side diaphragm 110. Also in this case, the intermediate diaphragm 112 and the base end side diaphragm 111 have an elastic action, and together with the front end side diaphragm 110, the elastic action as the diaphragm group 11 is exhibited.

  In such a structure, the elastic force of the intermediate diaphragm 112 and the base end side diaphragm 111 is slightly smaller than that of the intermediate diaphragm 112 and the base end side diaphragm 111 shown in FIG. The height can be reduced, and the diaphragm group 11 can be downsized as a whole. About the structure of another part, it is the same as that of the example shown in FIG. 9, and substantially the same effect is exhibited.

  In the embodiment shown in FIGS. 9 and 10, the sealing of the inner peripheral portion 111 a of the base end side diaphragm 111 and the piezoelectric element head 9 is performed through the through holes in the central portions of the front end side diaphragm 110 and the intermediate diaphragm 112. This is performed at the inclined portion 9e at the center of the element head 9. By forming the inclined portion 9e, the curved shape near the inner peripheral portion 111a of the base end side diaphragm 111 is maintained, and seal fixing by laser welding B is enabled. Yes.

  As described above, in the piezoelectric element sealing structure of the present invention, the diaphragm constituting the piezoelectric element sealing structure is the diaphragm group 11 including a plurality of diaphragms. Therefore, the load applied to the diaphragm group 11 due to the operation of the piezoelectric element 10 is a plurality of loads. The load can be shared by the diaphragm, so the load per diaphragm can be reduced, and even if there is a variation in the diaphragm thickness, curved shape, etc. during the fabrication of the diaphragm, the occurrence of cracks due to repeated loads caused by this variation is prevented. And durability can be improved.

  Further, in the piezoelectric element sealing structure of the present invention, the seal fixing of the outer peripheral portion 110b of the front end side diaphragm 110 to the sleeve 8 is performed on the outer peripheral side of the sleeve 8 when the outer peripheral portion 110b of the front end side diaphragm 110 is on the inner peripheral side of the sleeve 8. Since the diaphragm 110 is melted into the sleeve 8 having a large heat capacity, the diaphragm 110 can be securely fixed to the sleeve 8 by welding.

  Further, in the piezoelectric element sealing structure of the present invention, when the diaphragm group 11 has an even number of diaphragms, the outer peripheral portion 111b of the base end side diaphragm 111 can be positioned on the outer peripheral portion 111b of the piezoelectric element head 9, and the base end Seal welding B between the outer peripheral portion 111b of the side diaphragm 111 and the piezoelectric element head 9 is easy.

  Further, in the piezoelectric element sealing structure of the present invention, when the diaphragm group 11 has an odd number of diaphragms, the inner peripheral portion 111a of the base end side diaphragm 111 can be positioned at the central inclined portion 9e of the piezoelectric element head 9. In the seal welding fixing, the lap length between the inner peripheral portion 111a of the base end side diaphragm 111 and the central portion of the piezoelectric element head 9 can be taken, and good seal welding B can be performed.

  Moreover, in the piezoelectric element sealing structure of the present invention, since the base end side diaphragm 111 and the piezoelectric element head 9 are fixed by welding on the inner peripheral side of the outer peripheral portion 9a of the piezoelectric element head 9, welding is easy. In addition, the base end diaphragm 111 is melted into the piezoelectric element head 9 having a large heat capacity, and the base end diaphragm 111 can be reliably welded to the piezoelectric element head 9.

  Moreover, in the piezoelectric element sealing structure of the present invention, the diaphragms constituting the diaphragm group 11 are arranged in a warped shape in which the curved shapes of the diaphragms are reversed from each other. This can sufficiently cope with the expansion / contraction driving of the element 10.

  Moreover, in the piezoelectric element sealing structure of the present invention, the base end side diaphragm and the intermediate diaphragm constituting the diaphragm group 11 are arranged in a warped shape in which the curved shape of the base end side diaphragm and the intermediate diaphragm is the same direction as the front end side diaphragm. Therefore, the height can be reduced as compared with the warped diaphragms reversed to each other, and the physique can be reduced in size while maintaining the elastic force.

It is a partial cross section whole view which shows embodiment of the injector provided with the piezoelectric element sealing structure of this invention. It is sectional drawing which shows the piezoelectric element sealing structure part of this invention in FIG. It is an expanded sectional view which shows the principal part of this invention piezoelectric element sealing structure, and shows the example of the diaphragm group provided with the diaphragm of 2 sheets. It is a figure which shows the other example of the piezoelectric element sealing structure of this invention shown in FIG. It is a figure which shows the further another example of the piezoelectric element sealing structure of this invention shown in FIG. It is a figure which shows the further another example of the piezoelectric element sealing structure of this invention shown in FIG. It is an expanded sectional view which shows the principal part of this invention piezoelectric element sealing structure, and shows the example of a diaphragm group provided with four diaphragms. It is a figure which shows the other example of the piezoelectric element sealing structure of this invention shown in FIG. It is an expanded sectional view which shows the principal part of this invention piezoelectric element sealing structure, and shows the example of the diaphragm group provided with the diaphragm of 3 sheets. It is a figure which shows the other example of this invention piezoelectric element sealing structure shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injector 2 Drive part 3 Connector part 4 Fuel control part 5 Fuel injection part 7 Piezoelectric element base 8 Sleeve 9 Piezoelectric element head 9a Outer peripheral part 9b of piezoelectric element head 9 Front end side protrusion part 9c of outer peripheral part 9a of piezoelectric element head 9 Piezoelectric 9 d Circumferential flange portion 9 d of outer peripheral portion 9 a of the element head 9 Outer peripheral side portion 9 e of the outer peripheral portion 9 a of the piezoelectric element head 9 Inclined portion of the central portion of the piezoelectric element head 90 90 Tip portion of the piezoelectric element head 9 10 Piezoelectric elements 11 Diaphragm group 110 Front end diaphragm 110a Inner peripheral portion 110b of the front end side diaphragm 110 Outer peripheral portion of the front end side diaphragm 110 111 Base end side diaphragm 111a Inner peripheral portion of the base end side diaphragm 111 111b Outer peripheral portions 112, 113 of the base end side diaphragm 111 113a Intermediate diaphragm 112, 113 The inner peripheral portion 112b, the outer peripheral portion A piezoelectric element sealing structure 113b intermediate diaphragm 112 and 113 B seal welding

Claims (7)

A piezoelectric element;
A sleeve disposed on the outer periphery of the piezoelectric element;
A piezoelectric element base attached in contact with the proximal end side of the piezoelectric element;
A piezoelectric element head attached to the front end side in the driving direction of the piezoelectric element;
A diaphragm group fixed to the sleeve and the piezoelectric element head;
A piezoelectric element sealing structure in which the piezoelectric element is surrounded and sealed by the sleeve, the piezoelectric element base, the piezoelectric element head, and a group of diaphragms;
The diaphragm group includes a plurality of diaphragms, and the diaphragms are arranged to exert an elastic action with each other,
The outer peripheral part and inner peripheral part of each diaphragm are sealed and fixed to each other,
The outer peripheral part of the front end side diaphragm in the diaphragm group is sealed and fixed to the sleeve,
A piezoelectric element sealing structure, wherein an outer peripheral portion of a base end side diaphragm in the diaphragm group is fixed to the piezoelectric element head by sealing.   2. The seal fixing of the outer peripheral portion of the front end side diaphragm to the sleeve is characterized in that the outer peripheral portion of the front end side diaphragm is welded and fixed to the inner peripheral side of the sleeve from the outer peripheral side of the sleeve. The piezoelectric element sealing structure as described.   The diaphragm group has an even number of diaphragms, and seal fixing of the outer peripheral portion of the base end side diaphragm to the piezoelectric element head is performed by fixing the outer peripheral portion of the base end side diaphragm to the outer peripheral portion of the piezoelectric element head. 3. The piezoelectric element sealing structure according to claim 1, wherein the piezoelectric element sealing structure is provided.   3. The piezoelectric device according to claim 1, wherein the diaphragm group has an even number of diaphragms, and an outer peripheral portion of the base end side diaphragm is welded and fixed to an inner peripheral side of the outer peripheral portion of the piezoelectric element head. Element sealing structure.   3. The piezoelectric element according to claim 1, wherein the diaphragm group includes an odd number of diaphragms, and an inner peripheral portion of the base end side diaphragm is welded and fixed to a central inclined portion of the piezoelectric element head. Sealing structure.   6. The piezoelectric element sealing structure according to claim 1, wherein the diaphragms of the diaphragm group are arranged in a warped shape in which curved shapes of the diaphragms are reversed from each other. The piezoelectric element sealing structure according to any one of claims 1 to 5, wherein each diaphragm of the diaphragm group is arranged in a warped shape in which the curved shape of each diaphragm is the same direction.