JP2012115541A - Fluid injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a piezoelectric element that varies the volume of a fluid chamber of a fluid injection device from being damaged by the application of a tensile force thereto.SOLUTION: The piezoelectric element that varies the volume of the fluid chamber is secured at an end opposite to the fluid chamber and has a movable member provided at the other end on the side of the fluid chamber, the movable member being moved as the piezoelectric element expands. A magnetic force (magnetic attraction or magnetic repulsion) is applied to the movable member to bias the piezoelectric element in a direction to press against a fixed member. In this way, when a force in a pulling direction is generated on the piezoelectric element, the force receives the magnetic force and a tensile force actually working on the piezoelectric element is reduced, whereby the piezoelectric element can be prevented from being damaged by the action of the tensile force.

Description

  The present invention relates to a technique for ejecting a fluid from a nozzle.

2. Description of the Related Art A fluid ejecting apparatus that incises or excises a living tissue by pressurizing a fluid such as water or physiological saline and ejecting the fluid from a nozzle toward the living tissue has been developed. In surgery using such a fluid ejection device, it is possible to selectively incision or excision only of tissues such as organs without damaging nerves and blood vessels, etc., and there is little damage to surrounding tissues. Can be reduced.

In addition, a fluid ejecting apparatus that enables incision and excision of a living tissue with a small amount of ejection by ejecting in a pulse form by periodically changing the jet flow instead of ejecting fluid continuously from a nozzle. It has been proposed (Patent Document 1). In this fluid ejecting apparatus, first, a fluid is supplied to a fluid chamber connected to a nozzle, and the volume of the fluid chamber is instantaneously reduced, so that fluid pressurized in the fluid chamber is ejected in a pulse form from the nozzle. . Subsequently, the volume of the fluid chamber is restored and the fluid is supplied again. By repeating such an operation, a pulsed jet can be ejected periodically.

As a means for changing the volume of the fluid chamber in this way, a laminated piezoelectric element is often used. A stacked piezoelectric element is a columnar structure in which a large number of piezoelectric elements are stacked. When a drive voltage is applied, the stacked piezoelectric element expands and contracts in the stacking direction (thickness direction). The volume of the fluid chamber can be restored by contraction.

JP 2009-45167 A

However, such a piezoelectric element has a characteristic that it is strong against an external compressive force but weak against a tensile force. Therefore, there is a problem that it is easily damaged by receiving an external force in the tensile direction. For example, consider a case where the piezoelectric element expands and contracts due to application of a drive voltage to change the volume of the fluid chamber. When the piezoelectric element expands to reduce the volume of the fluid chamber, the fluid in the fluid chamber is pressurized, so that a compressive force acts on the piezoelectric element as a reaction force. Subsequently, when the piezoelectric element contracts and the volume of the fluid chamber is restored, a negative pressure is generated inside the fluid chamber. Therefore, a tensile force that pulls the contracting piezoelectric element back to the fluid chamber side is caused by the piezoelectric element. Will act. And
When such a tensile force acts on the piezoelectric element every time it contracts, the piezoelectric element is easily damaged.

The present invention has been made to solve the above-described problems of the prior art,
Reducing the tensile force acting on the piezoelectric element that changes the volume of the fluid chamber of the fluid ejection device,
An object of the present invention is to provide a technique capable of preventing breakage of a piezoelectric element.

In order to solve at least a part of the problems described above, the fluid ejecting apparatus of the present invention employs the following configuration. That is,
A fluid ejection device that ejects fluid from a nozzle,
A fluid chamber supplied with the fluid and connected to the nozzle;
A piezoelectric element that extends by applying a driving voltage to reduce the volume of the fluid chamber;
A movable member provided at an end of the piezoelectric element on the fluid chamber side and moving as the piezoelectric element expands;
A fixing member that fixes an end of the piezoelectric element opposite to the fluid chamber;
And a biasing member that biases the piezoelectric element in a direction in which the piezoelectric element is pressed against the fixed member by applying a magnetic force to the movable member.

In such a fluid ejecting apparatus of the present invention, the volume of the fluid chamber is reduced when the piezoelectric element is extended by application of a drive voltage in a state where the fluid is supplied to the fluid chamber, so that the fluid chamber is pressurized. Fluid is ejected from the nozzle. This piezoelectric element has an end opposite to the fluid chamber fixed by a fixing member. A movable member that moves as the piezoelectric element extends is provided at the end of the piezoelectric element on the fluid chamber side. In the fluid ejecting apparatus according to the aspect of the invention, the urging member urges the piezoelectric element in the direction in which the urging member is pressed against the fixed member by applying a magnetic force to the movable member.

The piezoelectric element that reduces the volume of the fluid chamber has a characteristic that it is strong against an external compressive force but weak against a tensile force. Become. Therefore, by applying a magnetic force to the movable member by the urging member so that a compressive force is applied in advance so as to press the piezoelectric element against the fixed member, a force in the tensile direction is generated on the piezoelectric element. Since the magnetic force is received by the force and the tensile force actually acting on the piezoelectric element can be reduced, the piezoelectric element can be prevented from being damaged by the action of the tensile force.

The above-described fluid ejecting apparatus of the present invention may be configured as follows. First, at least one of the movable member and the urging member is formed of a magnetic material, and the other member is formed of at least a part of a permanent magnet. Then, the urging member is fixed at a position closer to the fixed member than the movable member, and the movable member is moved in the direction in which the piezoelectric element is pressed against the fixed member by the magnetic attractive force acting between the movable member and the urging member. May be energized.

According to such a configuration, the movable member is attracted to the urging member (fixed member side) by the magnetic attraction force acting between the permanent magnet and the magnetic material, so that the movable member is sandwiched between the movable member and the fixed member. In addition, a compressive force can be applied to the piezoelectric element. When a force in the tensile direction is generated on the piezoelectric element, the force is received by the magnetic attraction force to reduce the tensile force acting on the piezoelectric element, thereby preventing the piezoelectric element from being damaged by the action of the tensile force. be able to.

Further, the above-described fluid ejecting apparatus of the present invention may be configured as follows. First, the movable member is provided with a first protrusion toward the biasing member, and the biasing member is provided with a second protrusion facing the first protrusion with a predetermined gap. Either one of the first protrusion and the second protrusion is formed of a permanent magnet or a magnetic material, and the other is formed of a permanent magnet. And you may form the 1st protrusion and the 2nd protrusion in the shape (taper shape) which cross-sectional area becomes narrow toward a front-end | tip.

The magnetic attraction force acting between the movable member and the urging member acts most strongly in the portion where the distance between them is the shortest (shortest portion), so the positional relationship between the movable member and the urging member is the shortest portion. When the direction shifts in the decreasing direction, a force acts in the restoring direction, that is, the direction that maintains (increases) the shortest portion. Further, by forming the first protrusion and the second protrusion facing each other with a predetermined gap in a tapered shape, if the shortest portion is limited in advance, the first protrusion and the second protrusion are flat rather than tapered (the same cross-sectional area as the base). ) Compared with the case where the surfaces face each other, a slight positional shift is greatly reflected in the reduction rate of the shortest portion, so that the restoring force works sharply. Therefore, when the first protrusion and the second protrusion are appropriately formed in advance, when assembling the fluid ejecting apparatus by the action of determining the positional relationship between the movable member and the urging member so as to secure a large number of the shortest portions. In addition, the movable member can be appropriately positioned with high accuracy.

In the fluid ejecting apparatus of the present invention, the following may be performed. First, one of the movable member and the biasing member is formed of a permanent magnet, and the other is formed of a magnetic material. A coil is provided on the member made of a magnetic material. And it is good also as detecting the displacement amount of expansion | extension of a piezoelectric element based on the voltage which arises in a coil when the distance of a permanent magnet and a coil changes by expansion | extension of a piezoelectric element.

When the piezoelectric element extends and the distance between the permanent magnet and the coil changes, the magnetic flux passing through the inside of the coil changes, so that a voltage is generated in the coil (electromagnetic induction). The magnitude of the voltage generated at this time is proportional to the amount of time change of the magnetic flux passing through the inside of the coil, and if the piezoelectric element expands greatly,
Since the amount of time change of the magnetic flux increases, a large voltage is generated. Therefore, it is possible to detect the amount of displacement of the expansion of the piezoelectric element from the voltage generated in the coil.

In addition, by monitoring the amount of displacement of the expansion of the piezoelectric element, it is possible to grasp a problem that has occurred in the fluid ejection device. For example, if bubbles are mixed in the fluid chamber, the bubbles are only compressed even if the volume of the fluid chamber is reduced by the expansion of the piezoelectric element, and no pressure is applied to the fluid. Therefore, when normal (when there are no bubbles in the fluid chamber) As compared with the above, the reaction force applied to the piezoelectric element is small. Therefore, when bubbles are mixed in the fluid chamber, the piezoelectric element expands more than normal, and a large voltage is generated in the coil. Therefore, the presence or absence of bubbles in the fluid chamber can be determined based on whether or not the voltage generated in the coil due to the expansion of the piezoelectric element is higher than the normal voltage. Also, if the piezoelectric element is damaged and cannot fully expand, the voltage generated in the coil will be smaller than normal (when the piezoelectric element is not damaged), so it is determined that a defect has occurred in the piezoelectric element. Can do.

Further, the above-described fluid ejecting apparatus of the present invention may be configured as follows. First, at least a part of the movable member is formed of a magnetic material including a permanent magnet, and at least a part of the biasing member is formed of a permanent magnet. Then, the urging member is fixed at a position opposite to the fixed member with respect to the movable member, and the piezoelectric element is pressed against the fixed member by a magnetic repulsive force acting between the movable member and the urging member. The movable member may be biased in the direction.

According to such a configuration, the movable member is urged toward the fixed member so as to move away from the urging member by the magnetic repulsive force that acts between the permanent magnet and the permanent magnet. A compressive force can be applied to the piezoelectric elements sandwiched therebetween. When a force in the tensile direction is generated on the piezoelectric element, the force is received by the magnetic repulsive force, and the tensile force acting on the piezoelectric element is reduced, so that damage to the piezoelectric element due to the action of the tensile force is prevented. be able to.

In the fluid ejecting apparatus of the present invention, the movable member and the urging member may all be made of a magnetic material. As a result, an efficient magnetic circuit having strong magnetic characteristics can be configured, so that a stronger magnetic attraction force or magnetic repulsion force can be obtained.

It is explanatory drawing which showed the rough structure of the fluid injection apparatus of a present Example. It is sectional drawing which showed the detailed structure of the pulsation generation | occurrence | production part. It is explanatory drawing which showed the shape of the permanent magnet and magnetic member seen from the reinforcement board side. It is explanatory drawing which showed a mode that a pulsation generation | occurrence | production part injects a fluid. It is sectional drawing which showed the shape of the permanent magnet and magnetic member which were provided in the pulsation generation | occurrence | production part of the 1st modification. It is explanatory drawing which showed a mode that a permanent magnet and a magnetic member function as positioning of a reinforcement board in the pulsation generation | occurrence | production part of a 1st modification. It is sectional drawing which showed the structure of the pulsation generation | occurrence | production part of a 2nd modification. It is sectional drawing which showed the pulsation generation | occurrence | production part which employ | adopted the structure which applies a magnetic repulsive force to a reinforcement board.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Configuration of fluid ejection device:
B. Configuration of pulsation generator:
C. Variations:
C-1. First modification:
C-2. Second modification:

A. Configuration of fluid ejection device:
FIG. 1 is an explanatory diagram showing a rough configuration of a fluid ejecting apparatus 10 according to the present embodiment. The illustrated fluid ejection device 10 is used in a surgical method for incising or excising a biological tissue by ejecting a fluid such as water or physiological saline toward the biological tissue.

As shown in the figure, the fluid ejection device 10 of the present embodiment includes a pulsation generator 100 that ejects fluid such as water and physiological saline in a pulsed manner, and a fluid that is ejected from the pulsation generator 100. A fluid supply means 300 for supplying the fluid, a fluid container 306 for containing the fluid to be ejected,
The pulsation generating unit 100 and the control unit 200 for controlling the operation of the fluid supply means 300 are configured.

The pulsation generator 100 has a structure in which the second case 106 and the first case 108 are overlapped and screwed together, and a circular pipe-shaped fluid ejection pipe 104 is connected to the front surface of the second case 106. A nozzle 102 is provided at the tip of the fluid ejection pipe 104. A thin disk-shaped fluid chamber 110 is provided on the mating surface of the second case 106 and the first case 108, and the fluid chamber 110 is connected to the nozzle 102 via the fluid ejection pipe 104. . The first case 108 is provided with a piezoelectric element 112 composed of a laminated piezoelectric element. By driving the piezoelectric element 112 by applying a driving voltage waveform, the fluid chamber 11 is provided.
By changing the volume of 0, the fluid in the fluid chamber 110 can be ejected in a pulse form from the nozzle 102. The detailed configuration of the pulsation generator 100 will be described later.

The fluid supply means 300 is connected to the fluid container 306 via the first connection tube 302, and supplies the fluid sucked from the fluid container 306 to the fluid chamber 110 of the pulsation generator 100 via the second connection tube 304. To do. The fluid supply means 300 of this embodiment is configured such that two pistons slide in the cylinder, and when one piston moves forward, the other piston moves backward and the two pistons are in opposite phases. It is possible to pump the fluid toward the pulsation generating unit 100 without interruption by sliding.

The controller 200 controls the operation of the piezoelectric element 112 built in the pulsation generator 100 and the operation of the fluid supply means 300. In the fluid ejecting apparatus 10 of the present embodiment, the fluid supply means 300
By changing the flow rate of the fluid supplied from the nozzle and the maximum voltage value and frequency of the drive voltage waveform applied to the piezoelectric element 112, it is possible to change the mode of ejection of the fluid from the nozzle 102.

B. Configuration of pulsation generator:
FIG. 2 is a cross-sectional view showing a detailed configuration of the pulsation generator 100. As described above, the pulsation generator 100 is configured by screwing the second case 106 and the first case 108 together. The first case 108 is formed with a circular shallow recess 108c substantially at the center of the surface mating with the second case 106. A circular cross-sectional through-hole penetrating the first case 108 is formed at the center of the recess 108c. 108h is formed.

A circular diaphragm 114 formed of a thin metal plate or the like is airtightly fixed to the bottom surface of the recess 108c so as to close the through hole 108h. Furthermore, on the diaphragm 114 (second
An annular spacer 120 is fitted into the recess 108c from the side of the surface mated with the case 106). The thickness of the spacer 120 is such that the diaphragm 114 and the spacer 1
The thickness obtained by adding 20 is set to be the same as the depth of the recess 108c.

The piezoelectric element 112 is housed in the through hole 108h closed by the diaphragm 114, and the opening of the through hole 108h is closed by the third case 118. A circular reinforcing plate 116 is inserted between the piezoelectric element 112 and the diaphragm 114. In the state where the piezoelectric element 112 is housed in the through hole 108h of the first case 108 and the through hole 108h is closed by the third case 118, the diaphragm 114, the reinforcing plate 116,
The thickness of the reinforcing plate 116 is set so that the piezoelectric element 112 and the third case 118 are just in contact with each other. In addition, one end of the piezoelectric element 112 is fixed to the third case 118, and the reinforcing plate 116 is fixed to the other end of the piezoelectric element 112. The surface of the reinforcing plate 116 opposite to the piezoelectric element 112 is fixed to the diaphragm 114. The reinforcing plate 116 of the present embodiment corresponds to a “movable member” of the present invention, and the third case 118 of the present embodiment corresponds to a “fixed member” of the present invention.

Further, in the pulsation generating unit 100 of the present embodiment, the surface on the piezoelectric element 112 side of the reinforcing plate 116 is
A permanent magnet 122 is provided around the piezoelectric element 112. Furthermore, the piezoelectric element 1 described later
A magnetic member 124 made of a magnetic material such as iron, cobalt, nickel, or an alloy thereof attracted to the magnet is provided at a position facing the permanent magnet 122 with respect to the 12 expansion directions (compression directions). The end of the magnetic member 124 opposite to the permanent magnet 122 is fixed to the third case 118. A gap G (0.05 mm in this embodiment) is provided between the permanent magnet 122 and the magnetic member 124 so that a magnetic attractive force acts. The magnetic member 124 of this embodiment corresponds to the “biasing member” of the present invention. The roles of the permanent magnet 122 and the magnetic member 124 will be described in detail later.

FIG. 3 is an explanatory view showing the shapes of the permanent magnet 122 and the magnetic member 124 as seen from the reinforcing plate 116 side. First, FIG. 3A shows the shapes of the permanent magnet 122 and the magnetic member 124 provided in the pulsation generator 100 of the present embodiment. As shown in the drawing, the permanent magnet 122 is formed in an annular shape so as to surround the periphery of the quadrangular prism piezoelectric element 112. The magnetic member 124 is formed in a circular tube having the same cross-sectional shape as the permanent magnet 122, and the piezoelectric element 112 is located in the center of the internal space of the magnetic member 124. In the pulsation generating unit 100 of the present embodiment, the quadrangular prism piezoelectric element 112 is used, but the shape of the piezoelectric element 112 is not limited to this, and may be, for example, a cylinder. Further, the permanent magnet 122
The magnetic member 124 does not necessarily have a series of annular shapes as long as it is evenly arranged with respect to the piezoelectric element 112, and is a divided member as shown in FIG. 3B or 3C. May be.

On the other hand, as shown in FIG. 2, the second case 106 has a surface to be combined with the first case 108,
A circular shallow recess 106c is formed. The inner diameter of the concave portion 106c is the same as that of the first case 10.
8 is set to approximately the same size as the inner diameter of the spacer 120 fitted into the spacer 8. Then, when the second case 106 and the first case 108 are screwed together, the recess 106c provided in the second case 106, and the inner peripheral surface of the diaphragm 114 and the spacer 120 provided on the first case 108 side As a result, a substantially disc-shaped fluid chamber 110 is formed.

The second case 106 is provided with an inflow passage 106 a that guides the fluid supplied by the fluid supply means 300 from the side of the second case 106 to the fluid chamber 110. Furthermore, an outflow passage 106 b that guides the fluid pressurized in the fluid chamber 110 to the fluid ejection pipe 104 is provided at the central position of the recess 106 c. In the pulsation generator 100 configured as described above, a fluid is ejected as follows by applying a drive voltage waveform to the piezoelectric element 112.

FIG. 4 is an explanatory diagram showing a state in which the pulsation generator 100 ejects fluid. First, FIG.
a) shows a state where the piezoelectric element 112 is not driven (a state before a drive voltage waveform is applied to the piezoelectric element 112). In this state, as shown by the thick dashed arrow in the figure,
The fluid chamber 110 is filled with the fluid supplied from the fluid supply means 300. As described above, since the fluid is supplied from the fluid supply means 300 without interruption, when the fluid chamber 110 is filled with the fluid, the fluid in the fluid chamber 110 is discharged even if the piezoelectric element 112 is not driven. It is pushed out toward the fluid ejection pipe 104. In addition, when the piezoelectric element 112 is not driven, no tension is applied to the diaphragm 114, and therefore the diaphragm 114 does not push the piezoelectric element 112 in the direction of contraction.

When the drive voltage waveform is applied to the piezoelectric element 112 in a state where the fluid chamber 110 is filled with the fluid as described above, the piezoelectric element 112 expands as the drive voltage increases as shown in FIG. 4B. Since the diaphragm 114 is pushed toward the fluid chamber 110 through the reinforcing plate 116, the volume of the fluid chamber 110 is reduced, and as a result, the fluid in the fluid chamber 110 is pressurized. The fluid thus pressurized in the fluid chamber 110 is ejected from the nozzle 102 via the outflow passage 106b and the fluid ejection pipe 104, as indicated by the thick dashed arrows in FIG. When the piezoelectric element 112 expands and pressurizes the fluid in the fluid chamber 110, a force to push back is applied to the surface of the diaphragm 114 on the fluid chamber 110 side as a reaction force. The piezoelectric element 112 is also loaded in the compression direction via the. A thick solid line arrow in FIG. 4B schematically represents a reaction force applied to the diaphragm 114 when the fluid in the fluid chamber 110 is pressurized.

When the fluid is ejected in this manner, subsequently, as shown in FIG. 4C, the piezoelectric element 112 contracts to return to the original length due to the decrease in the driving voltage. As described above, the piezoelectric element 1
One end of 12 is fixed to the third case 118, and the other end of the piezoelectric element 112 is connected to the reinforcing plate 11.
6 is fixed. Further, since the reinforcing plate 116 is fixed to the diaphragm 114, when the piezoelectric element 112 contracts, the diaphragm 114 is attracted to the fluid chamber 1.
Increase 10 volume (restore to original volume). At this time, since the inside of the fluid chamber 110 instantaneously becomes a negative pressure, a force is applied to the diaphragm 114 to pull it back to the fluid chamber 110 side. A thick solid arrow in FIG. 4C schematically represents the force that the negative pressure generated in the fluid chamber 110 when the piezoelectric element 112 contracts tries to pull back the diaphragm 114.

Due to the contraction of the piezoelectric element 112, the volume of the fluid chamber 110 is restored to the original volume, and the fluid is supplied from the fluid supply means 300 to the fluid chamber 110, whereby the piezoelectric element 1 shown in FIG.
It returns to the state before 12 is driven. Then, again, the piezoelectric element 112 is increased by increasing the driving voltage.
As shown in FIG. 4B, the fluid pressurized in the fluid chamber 110 is transferred to the nozzle 10 as shown in FIG.
2 is injected. By repeating such an operation, the pulsation generator 100 of this embodiment is used.
Then, it is possible to eject the fluid from the nozzle 102 in a pulse shape.

Here, in the fluid ejection device 10 of the present embodiment, the piezoelectric element 1 that changes the volume of the fluid chamber 110.
12, a laminated piezoelectric element that expands and contracts by applying a drive voltage waveform is used. Such a piezoelectric element has a characteristic that it is strong against an external compressive force but weak against a tensile force. As described above, when the piezoelectric element 112 expands and pressurizes the fluid in the fluid chamber 110, the reaction force acts in the direction of compressing the piezoelectric element 112, so that a force in the tensile direction acts on the piezoelectric element 112. Never do. In contrast, the piezoelectric element 112 contracts and the fluid chamber 110 is compressed.
When the volume of the diaphragm 114 is increased, the diaphragm 114 is caused by the negative pressure generated in the fluid chamber 110.
Therefore, a force in the pulling direction acts on the piezoelectric element 112 through the reinforcing plate 116 fixed to the diaphragm 114. And
When such a tensile force acts every time the piezoelectric element 112 contracts, the piezoelectric element 112 constituted by the stacked piezoelectric elements may be delaminated and damaged. Also,
When the piezoelectric element 112 is not driven, as described above, the piezoelectric element 112 is not urged in the compression direction by the diaphragm 114. Therefore, when some external force acts on the piezoelectric element 112 in the tensile direction, The piezoelectric element 112 may be damaged.

In view of these points, in the fluid ejecting apparatus 10 of this embodiment, as described above, the reinforcing plate 116 is used.
A permanent magnet 122 is provided on the surface of the piezoelectric element 112, and a magnetic member 124 facing the permanent magnet 122 with a gap G in the expansion direction (compression direction) of the piezoelectric element 112 is the third.
Since it is fixed to the case 118 (see FIG. 2), the piezoelectric element 112 is as follows.
It is possible to prevent damage to the machine. First, since a magnetic attractive force acts between the permanent magnet 122 and the magnetic member 124, the reinforcing plate 116 is moved to the third case 118 by this magnetic attractive force.
As a result, the piezoelectric element 112 sandwiched between the reinforcing plate 116 and the third case 118 is in a state in which a force in the compression direction is applied so as to be pressed against the third case 118. In this way, if a magnetic attractive force is applied to the reinforcing plate 116 and a compressive force is applied to the piezoelectric element 112 in advance, a tensile force is generated when the piezoelectric element 112 contracts (see FIG. 4C). In this case, the tensile force actually acting on the piezoelectric element 112 can be reduced by receiving the tensile force by the magnetic attraction force, thereby reducing the possibility of the piezoelectric element 112 being damaged by the action of the tensile force. Can do.

In the pulsation generating unit 100 of the present embodiment, it has been described that the reinforcing plate 116 is provided with the permanent magnet 122 and the magnetic member 124 is fixed to the third case 118 (see FIG. 2). However, on the contrary, an annular magnetic member is provided on the reinforcing plate 116, and a circular tube-shaped permanent magnet facing the expansion direction (compression direction) of the piezoelectric element 112 with a gap G therebetween. May be fixed to the third case 118. By doing so, the permanent magnet can be thickened, so that a stronger magnetic attractive force can be obtained. In addition, a permanent magnet is provided on the reinforcing plate 116, and another permanent (N pole and S pole) faces each other with a gap G between the permanent magnet and the extension direction (compression direction) of the piezoelectric element 112. A magnet may be fixed to the third case 118. As a result, a stronger magnetic attractive force can be obtained between the two permanent magnets.
The tensile force acting on the piezoelectric element 112 can be more reliably suppressed.

As described above, in the fluid ejecting apparatus 10 of this embodiment, the reinforcing plate 116 is fixed to the end of the piezoelectric element 112 that changes the volume of the fluid chamber 110 on the fluid chamber 110 side. By applying a magnetic attraction force to the piezoelectric element 112, a compressive force (preload) is applied to the piezoelectric element 112 so as to be pressed against the third case 118. This
When a force in the tensile direction is generated with respect to the piezoelectric element 112, the force is received by the magnetic attractive force, and the tensile force applied to the piezoelectric element 112 is reduced. Therefore, the piezoelectric element 112 is not damaged due to the action of the tensile force. It becomes possible to reduce. As a result, the multilayer piezoelectric element is replaced with the piezoelectric element 11.
The durability of the fluid ejection device 10 mounted as 2 can be improved.

C. Modified example:
There are several variations of the fluid ejecting apparatus 10 of the present embodiment described above. Hereinafter, these modified examples will be described. In the description of the modification, the same components as those of the above-described embodiment are denoted by the same reference numerals as those of the above-described embodiment, and the detailed description thereof is omitted.

C-1. First modification:
In the fluid ejection device 10 of the first modification, the permanent magnet 122 provided inside the pulsation generator 100.
In order to use the magnetic attractive force acting between the magnetic member 124 and the magnetic member 124 not only to urge the reinforcing plate 116 toward the third case 118 but also to position the reinforcing plate 116, the following configuration is used. Adopted.

FIG. 5 shows the permanent magnet 122 and the magnetic member 1 provided in the pulsation generator 100 of the first modification.
It is sectional drawing which showed the shape of 24. In FIG. 5, the second case 106 and the third case 118 are shown.
Is omitted. As shown in the figure, the pulsation generator 100 of the first modification example is also
Similar to the above-described embodiment (see FIG. 2), the permanent magnet 122 is provided on the surface of the reinforcing plate 116 on the piezoelectric element 112 side, and the permanent magnet 12 is in the expansion direction (compression direction) of the piezoelectric element 112.
2 and a magnetic member 124 facing each other with a gap G therebetween are fixed to the third case 118. However, in the first modification, unlike the above-described embodiments, the respective end portions of the permanent magnet 122 and the magnetic member 124 facing the expansion direction (compression direction) of the piezoelectric element 112 have a cross-sectional area toward the tip. It is formed into a narrow shape. That is, a first protrusion is formed at the end of the permanent magnet 122 facing the magnetic member 124, while a second protrusion is formed at the end of the magnetic member 124 facing the permanent magnet 122. Thus, the permanent magnet 12
2 and the respective end portions of the magnetic member 124 facing each other are tapered so that the reinforcing plate 116 can be used for positioning. This point will be described below.

FIG. 6 is an explanatory view showing a state in which the permanent magnet 122 and the magnetic member 124 function as positioning of the reinforcing plate 116. As described above, each of the permanent magnet 122 and the magnetic member 124 according to the first modified example has a tapered shape at each end that faces the expansion direction (compression direction) of the piezoelectric element 112 with a gap G therebetween. . These permanent magnet 122 and magnetic member 12
The magnetic attraction force acting between the magnetic force 4 and the magnetic force 4 acts most strongly in the portion where the distance between the two becomes the shortest (the portion overlapping with the gap G therebetween). FIG. 6A shows a stable state with the most overlapping portions with a gap G therebetween.

It is assumed that the reinforcing plate 116 provided with the permanent magnet 122 is shifted in the right direction in the drawing from the state shown in FIG. 6A as shown in FIG. 6B. At this time, the permanent magnet 122 has the structure shown in FIG.
As indicated by the white arrow in (b), a force acts to return to the state of FIG. 6 (a). This is the same as when the distance between the permanent magnet 122 and the distance between the permanent magnet 122 and the magnetic member 124 is reduced when the permanent magnet 122 is shifted laterally, and the distance between the permanent magnet 122 and the magnetic member 124 decreases. For this reason, the force acts in the direction of pulling it back, that is, in the direction of increasing the overlapping portion with the gap G.

In addition, as shown in FIG. 6C, when the permanent magnet 122 and the magnetic member 124 face each other on the surfaces whose end portions are not tapered and the cross-sectional area does not change (the same cross-sectional area as the base), Even if the permanent magnet 122 is shifted laterally by the same amount as in the case of FIG. 6B, the reduction rate of the overlapping portion with a gap G is slight. Compared to this, when the end portions of the permanent magnet 122 and the magnetic member 124 facing each other are formed in a tapered shape, the overlapping portion with the gap G therebetween is limited in advance, and therefore, as shown in FIG. As described above, even if the position of the permanent magnet 122 is slightly shifted, it is greatly reflected in the reduction rate of the overlapping portion with the gap G therebetween, and the force for pulling back this acts sharply.

As described above, in the fluid ejection device 10 according to the first modified example, the gap G is formed by forming the end portions of the permanent magnet 122 and the magnetic member 124 facing the expansion direction (compression direction) of the piezoelectric element 112 in a tapered shape. Since the overlapping portion (the portion where the magnetic attractive force acts most strongly) is limited, the force to return to the original position is sharp even when the positional relationship between the permanent magnet 122 and the magnetic member 124 is slightly shifted. Working, the positional relationship with the most overlapping parts with a gap G (
The state of FIG. 6A is maintained. And such a permanent magnet 122 and the magnetic member 124 are used.
When the pulsation generator 100 is assembled by the action of maintaining the positional relationship with the reinforcing plate 1
Since 16 is appropriately positioned with high accuracy, it is possible to suppress variations in manufacturing of the position of the reinforcing plate 116.

C-2. Second modification:
In the fluid ejection device 10 of the second modified example, the following configuration is adopted in order to detect bubbles mixed in the fluid chamber 110 using the permanent magnet 122 provided on the reinforcing plate 116.

FIG. 7 is a cross-sectional view showing the configuration of the pulsation generator 100 of the second modification. As shown in the drawing, the pulsation generating unit 100 of the second modified example is also provided with a permanent magnet 122 on the surface of the reinforcing plate 116 on the piezoelectric element 112 side, as in the above-described embodiment (see FIG. 2). Piezoelectric element 112
Magnetic member 1 facing the permanent magnet 122 with a gap G with respect to the stretching direction (compression direction) of
24 is fixed to the third case 118. However, the pulsation generator 100 of the second modification differs from the above-described embodiment in that the coil 126 is wound around the magnetic member 124. The coil 126 is connected to a voltmeter (not shown) provided in the control unit 200, and the control unit 200 can detect a voltage generated in the coil 126. In the fluid ejecting apparatus 10 of the second modified example having such a configuration, the fluid chamber 11 is as follows.
It is possible to detect bubbles in zero.

First, when the distance between the permanent magnet 122 and the coil 126 changes due to the extension of the piezoelectric element 112, the magnetic flux passing through the inside of the coil 126 changes, so that a voltage is generated in the coil 126 (electromagnetic induction). The magnitude of the voltage generated at this time is proportional to the amount of time change of the magnetic flux passing through the inside of the coil 126, and when the piezoelectric element 112 expands greatly (the distance between the permanent magnet 122 and the coil 126 changes greatly), the magnetic flux Since the amount of time change of becomes large, a large voltage is generated. As described above, since the coil 126 is connected to the control unit 200, the control unit 200 can detect the amount of expansion displacement of the piezoelectric element 112 from the voltage generated in the coil 126. Such a control unit 200 of the present embodiment corresponds to the “displacement amount detection means” of the present invention.

When air bubbles are not mixed in the fluid chamber 110, when the piezoelectric element 112 expands and pressurizes the fluid in the fluid chamber 110 as described above with reference to FIG. The element 112 is loaded in the compression direction. On the other hand, when bubbles are mixed in the fluid chamber 110, even if the volume of the fluid chamber 110 is reduced by the extension of the piezoelectric element 112, the bubbles only contract and no pressure is applied to the fluid. As a result, the load on the piezoelectric element 112 is also reduced. For this reason, when bubbles are mixed in the fluid chamber 110, the piezoelectric element 11 is compared with the normal time.
2 can extend greatly, and a large voltage is generated in the coil 126.

As described above, when bubbles are mixed in the fluid chamber 110, a voltage larger than that in the normal state is generated in the coil 126. Therefore, the voltage generated in the coil 126 in the normal state is used as a reference value.
Based on whether or not the voltage value detected by the voltmeter connected to the coil 126 is higher than the reference value, the presence or absence of bubbles in the fluid chamber 110 can be determined.

The piezoelectric element 1 is based on the voltage generated in the coil 126 due to the expansion of the piezoelectric element 112.
Since the amount of displacement of the 12 expansions can be monitored, it is possible to detect not only the bubbles mixed in the fluid chamber 110 but also some troubles occurring in the piezoelectric element 112. For example, if the piezoelectric element 112 is damaged and does not expand sufficiently, the voltage generated in the coil 126 is smaller than that in the normal state, and therefore it can be determined that a problem has occurred in the piezoelectric element 112.

As mentioned above, although various embodiment was demonstrated about the fluid injection apparatus of this invention, this invention is not restricted to all the said embodiment, It is possible to implement in a various aspect in the range which does not deviate from the summary. is there.

For example, in the above-described embodiment, by applying a magnetic attractive force to the reinforcing plate 116,
A compressive force was applied to the piezoelectric element 112 so as to press against the third case 118. However, a compression force may be applied to the piezoelectric element 112 by applying a magnetic repulsive force to the reinforcing plate 116. FIG. 8 is a cross-sectional view showing the pulsation generator 100 that employs a configuration in which a magnetic repulsive force is applied to the reinforcing plate 116. As shown, the reinforcing plate 116
A first permanent magnet 130 is provided on the surface of the diaphragm 114 side. The second case 106 has a piezoelectric element 112 at a position opposite to the reinforcing plate 116 across the fluid chamber 110.
The second permanent magnet 13 that faces the first permanent magnet 130 with respect to the extending direction (compression direction) of
2 is embedded. The first permanent magnet 130 and the second permanent magnet 132 are provided so that the same poles (N pole or S pole) face each other, and a magnetic repulsive force acts between them. The reinforcing plate 116 is urged toward the third case 118 by the force. As a result, the piezoelectric element 112 is in a state where a force in the compression direction is applied so as to be pressed against the third case 118. When a force in the tensile direction is generated on the piezoelectric element 112, the force is received by the magnetic repulsive force, and the tensile force applied to the piezoelectric element 112 is reduced.
Similar to the embodiment described above, it is possible to reduce the occurrence of damage to the piezoelectric element 112 due to the action of the tensile force.

It should be noted that by combining the configuration in which the magnetic repulsive force is applied to the reinforcing plate 116 shown in FIG. 8 and the configuration in which the magnetic attractive force is applied to the reinforcing plate 116 shown in FIG. It is good also as making a magnetic repulsive force act together. As a result, since a stronger compressive force can be applied to the piezoelectric element 112, the tensile force acting on the piezoelectric element 112 can be reduced, and the occurrence of damage to the piezoelectric element 112 can be more reliably reduced. It becomes possible.

DESCRIPTION OF SYMBOLS 10 ... Fluid injection apparatus, 100 ... Pulsation generation | occurrence | production part, 102 ... Nozzle,
104: Fluid ejection pipe 110: Fluid chamber 112: Piezoelectric element
114 ... Diaphragm, 116 ... Reinforcing plate, 118 ... Third case,
122 ... Permanent magnet, 124 ... Magnetic member, 126 ... Coil,
200 ... Control unit, 300 ... Fluid supply means, 302 ... First connection tube,
304 ... Second connection tube, 306 ... Fluid container

Claims (5)

A fluid ejection device that ejects fluid from a nozzle,
A fluid chamber supplied with the fluid and connected to the nozzle;
A piezoelectric element that extends by applying a driving voltage to reduce the volume of the fluid chamber;
A movable member provided at an end of the piezoelectric element on the fluid chamber side and moving as the piezoelectric element expands;
A fixing member that fixes an end of the piezoelectric element opposite to the fluid chamber;
A fluid ejecting apparatus comprising: an urging member that urges the piezoelectric element in a direction to press the piezoelectric element against the fixed member by applying a magnetic force to the movable member. The fluid ejection device according to claim 1,
Either one of the movable member and the urging member is at least partly formed of a magnetic material, and one of the movable member and the urging member is at least partly formed of a permanent magnet,
The biasing member is
It is fixed at a position closer to the fixed member than the movable member,
A fluid ejecting apparatus that is a member that urges the movable member by a magnetic attractive force acting between the movable member and the movable member. The fluid ejecting apparatus according to claim 2,
The movable member is provided with a first protrusion toward the biasing member,
The biasing member is provided with a second protrusion that faces the first protrusion with a predetermined gap therebetween,
Either one of the first protrusion and the second protrusion is made of a permanent magnet or a magnetic material, and the other is made of a permanent magnet,
The fluid ejecting apparatus, wherein the first protrusion and the second protrusion are formed in a shape in which a cross-sectional area becomes narrower toward a tip. The fluid ejecting apparatus according to claim 2 or 3,
Either one of the movable member and the biasing member is formed of a permanent magnet, and the other is formed of a magnetic material,
Of the movable member and the biasing member, the member formed of the magnetic material is provided with a coil.
A fluid ejecting apparatus comprising: a displacement amount detecting unit configured to detect a change amount of expansion of the piezoelectric element based on a voltage generated in the coil when a distance between the permanent magnet and the coil is changed due to expansion of the piezoelectric element. The fluid ejection device according to claim 1,
The movable member is at least partially formed of a permanent magnet,
The biasing member is
At least a part is formed of a permanent magnet, and is fixed at a position opposite to the fixed member with respect to the movable member,
A fluid ejecting apparatus that is a member that biases the movable member by a magnetic repulsive force acting between the movable member.

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