Washer-type load cell, thrust load detection mechanism, injection apparatus, and imaging system

Abstract

To provide a washer-type load cell that can detect thrust loads applied in the shaft direction with high accuracy while being compact.SOLUTION: A washer-type load cell includes a main body which has an opening through which a rotating shaft is inserted and detection means which is fixed to the main body to detect a strain in the main body. The main body includes a first pressure-receiving part that receives a force in the first direction of the shaft direction on one side in the shaft direction of the rotating shaft, and multiple second pressure-receiving parts that counteract the force in the first direction on the opposite side in the shaft direction. The multiple second pressure-receiving parts and the detection means are arranged at farther positions in the radial direction from the center of the opening than the first pressure-receiving part. The detection means is arranged at an intermediate position of at least one pair of adjacent second pressure-receiving parts in the circumferential direction around the opening.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a washer-type load cell, a thrust load detection mechanism including the washer-type load cell, an injection device for injecting a chemical solution, and an imaging system. [Background technology]

[0002] Conventionally, in medical institutions, syringe pumps are used as injection devices for injecting medicinal fluids such as nutritional supplements, blood transfusions, chemotherapy fluids, and anesthetics into the body at a predetermined injection rate. This syringe pump injects the medicinal fluid in the syringe into the body by pressing the piston of the syringe with a linearly movable slider that engages with a feed screw.

[0003] Patent Document 1 discloses a syringe pump that detects the thrust load applied in the axial direction of a feed screw and monitors the drug injection status to determine whether the drug is being injected reliably at a programmed predetermined injection rate.

[0004] Patent Document 2 discloses a washer-type load cell used in press-fitting devices and presses to measure the thrust load acting on the rotating shaft of an electric cylinder that converts the rotational motion of an electric motor into linear motion. The washer-type load cell in Patent Document 2 is annular, and has a load cell body that receives the thrust load and a strain detection means on one side, and has a number of support parts arranged at predetermined intervals in the circumferential direction on the other side, and is configured to distort with the support parts as fulcrums in response to the thrust load. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2003-201958 A [Patent Document 2] JP 2012-088091 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the syringe pump of Patent Document 1, the thrust load applied in the axial direction of the feed screw is detected by an axial displacement detection means arranged at the axial rear end of the feed screw, which makes it difficult to make the device compact in the axial direction.In addition, in Patent Document 2, the pressure receiving part, support part and strain detection means of the washer-type load cell are arranged on the same circumference, and the detection means is fixed avoiding the protruding part of the pressure receiving part, which makes it difficult to arrange the strain detection means in a position where the deformation is large. An object of the present invention is to provide a washer-type load cell that is compact yet capable of detecting a thrust load applied in the axial direction with high accuracy. [Means for solving the problem]

[0007] In order to solve the above problems, the washer-type load cell of the present invention is a washer-type load cell having a main body having an opening into which a rotating shaft is inserted, and a detection means fixed to the main body and detecting strain of the main body, wherein the main body has a first pressure receiving portion on one side in the axial direction of the rotating shaft that receives a force in a first direction in the axial direction, and a plurality of second pressure receiving portions on the other side in the axial direction that resist the force in the first direction, the plurality of second pressure receiving portions and the detection means are arranged at a position radially farther from the center of the opening than the first pressure receiving portion, and the detection means is arranged at an intermediate position between at least a pair of adjacent second pressure receiving portions in a circumferential direction around the opening.

[0008] This makes it possible to provide a washer-type load cell that is compact yet capable of detecting thrust loads applied in the axial direction with high accuracy.

[0009] Further characteristics of the invention will become apparent from the following description of an embodiment thereof, given by way of example only with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic perspective view of an injection device using a washer-type load cell according to a first embodiment. [Diagram 2] FIG. 1 is a block diagram of an injection device using a washer-type load cell according to a first embodiment. [Diagram 3] FIG. 2 is a perspective view of a nut plate of the injection device according to the first embodiment. [Figure 4] FIG. 2 is a perspective view showing a fixing portion of a washer-type load cell in the first embodiment. [Diagram 5] FIG. 2 is an exploded perspective view showing a fixing portion of a washer-type load cell in the first embodiment. [Figure 6] FIG. 2 is a cross-sectional view showing a fixing portion of a washer-type load cell in the first embodiment. [Figure 7] FIG. 1 is a plan view of a washer-type load cell according to a first embodiment. [Figure 8] FIG. 13 is a perspective view showing a modified example of the washer-type load cell of the present invention. [Figure 9] FIG. 4 is an enlarged image diagram of a pressing member of the washer-type load cell in the first embodiment. [Figure 10] FIG. 11 is a block diagram of an injection device using a washer-type load cell according to a second embodiment. [Figure 11] FIG. 11 is an exploded perspective view showing a fixing portion of a washer-type load cell in Example 2. [Figure 12] FIG. 11 is a block diagram of an injection device using a washer-type load cell in Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positions of components, etc. described in the following embodiments are arbitrary and can be changed according to the configuration of the device to which the present invention is applied or various conditions. Furthermore, unless otherwise specified, the scope of the present invention is not limited to the forms specifically described in the embodiments described below. EXAMPLES

[0012] 1 and 2 are a schematic perspective view and a block diagram, respectively, of the injection device 1 of this embodiment. Note that, although the injection head 2 is attached to a stand 11 as shown in Fig. 1, this is merely an example, and it may also be attached to a ceiling suspension device.

[0013] The injection device 1 for injecting a medicinal liquid will be described with reference to Fig. 1, which is a schematic perspective view of the injection device 1. The injection device 1 includes an injection head 2 on which a syringe 91 filled with the medicinal liquid is mounted, a pressing unit 401 provided on the injection head 2 for pressing the rear end of a piston 93 as the rear end of the syringe 91, and a control device 5 for controlling the injection head 2. The control device 5 controls the pressing unit 401 to deliver the medicinal liquid from the syringe 91, and moves the piston 93 forward while pressing the rear end of the piston 93.

[0014] Injection device 1 is equipped with syringe holder 92 for mounting syringe 91 on injection head 2. Pressing portion 401 of injection device 1 presses the rear end of syringe 91. Note that in FIG. 1, injection head 2 has two syringe holders 92 in order to mount two syringes 91. However, injection head 2 may have one syringe holder 92 or three or more syringe holders 92.

[0015] Injection device 1 also includes console 6 having a touch panel as a display unit that displays the injection status of the medicinal liquid. Console 6, control device 5, and injection head 2 are each wired connected via metal cable 12, optical cable 13, etc. Alternatively, they may be connected wirelessly, for example, by a wireless method using a frequency band of 2.4 GHz to 5 GHz. Control device 5 also has a power supply (not shown) for injection head 2, but this power supply can be provided in injection head 2 or in console 6. Furthermore, an independent power supply can be provided separately, or the power supply can be replaced by a battery.

[0016] A remote control device such as a hand switch 14 is connected by wire to the console 6 in order to start or stop the injection of the liquid medicine. The remote control device may be connected to the console 6 wirelessly, or may be connected to the injection head 2 by wire or wirelessly.

[0017] Furthermore, injection device 1 is equipped with a caster stand 11 on which injection head 2 is mounted. Incidentally, control device 5 can also be mounted on caster stand 11. In addition, injection head 2 and control device 5 can be integrally configured and both can be mounted on caster stand 11. Furthermore, a ceiling suspension member can be provided instead of caster stand 11, and injection head 2 can be suspended from the ceiling via this ceiling suspension member.

[0018] Injection head 2 is also provided with operation buttons, such as forward button 24, acceleration button 25, reverse button 26, check button 27, and start button 28. The operator can manually operate injection head 2 by operating the operation buttons. Specifically, while the operator is pressing forward button 24, pressing unit 401 moves forward. When the operator presses forward button 24 and acceleration button 25 simultaneously, the forward speed of pressing unit 401 is accelerated. Furthermore, while the operator is pressing reverse button 26, pressing unit 401 moves backward.

[0019] Furthermore, when the operator presses check button 27, injection head 2 waits in a state where it is ready for injection. Thereafter, when the operator presses start button 28, injection head 2 begins injecting the medicinal liquid. Operation buttons such as check button 27 and start button 28 are also displayed on the touch panel of console 6. The operator can also operate injection head 2 manually by operating the touch panel. Note that injection device 1 may be configured so that pressing unit 401 automatically retracts to a predetermined position. For example, injection device 1 may be configured so that when the operator presses retract button 26, pressing unit 401 automatically retracts to a predetermined position.

[0020] The pressing part 401 of the injection head 2 is connected to the driving mechanism 4. For example, the driving mechanism 4 includes a transmission mechanism 47 connected to the ultrasonic motor 3, for example, a shaft 35 of the ultrasonic motor 3, a ball screw shaft 411 connected to the transmission mechanism 47, a ball screw nut 412 engaged with the ball screw shaft 411, and an actuator 40 connected to the ball screw nut 412. The configuration of the transmission mechanism 47 will be described later. The ball screw shaft 411 rotates according to the transmitted rotation, and the ball screw nut 412 slides in the forward or backward direction in accordance with the rotation of the ball screw shaft 411. The pressing part 401 moves forward or backward in accordance with the sliding of the ball screw nut 412. Note that, here, the transmission mechanism 47 is connected to a ball screw and the rotation is converted into a linear motion, but the present invention is not limited to this. For example, it should be noted that the effect of the present invention can be enjoyed even if the rotation-linear motion conversion mechanism is configured with a sliding screw (trapezoidal screw).

[0021] A piston 93 that is slidable within the syringe 91 is attached to the syringe 91 mounted on the injection head 2. When the ultrasonic motor rotates forward with the rear end of the piston 93 in contact with the pressing portion 401, the pressing portion 401 pushes the piston 93 in the forward direction. When the piston 93 moves forward, the medicinal liquid in the syringe 91 is pushed out and injected into the patient's body via an extension tube 900 and a mixing device 910 connected to the tip of the syringe 91. On the other hand, when the ultrasonic motor rotates in the reverse direction, the pressing portion 401 pulls the piston 93 in the backward direction.

[0022] The syringe 91 may be a prefilled syringe. The liquid medicine may be manually filled into the syringe 91, or may be filled into the syringe 91 by the injection device 1 or a filler. The syringe 91 may be provided with a data carrier such as an RFID (Radio Frequency Identifier) ​​or a barcode. Information on the filled liquid medicine, etc., is recorded on this data carrier. The injection device 1 can read the recorded information from the data carrier via the injection head 2 and control the injection pressure of the liquid medicine, etc. For example, the control device 5 can calculate the optimal injection amount per body weight based on the read information on the liquid medicine (such as the amount of iodine and the gadolinium content) and display it on the touch panel of the console 6.

[0023] The injection head 2 and the control device 5 can be constructed using non-magnetic materials so that they can be placed near an imaging device that utilizes magnetism, for example, in an examination room. For example, non-magnetic materials include stainless steel, aluminum, plastic, brass, copper, and ceramics. In this case, the injection head 2 has an ultrasonic motor constructed using non-magnetic materials. In this ultrasonic motor, for example, the elastic body is made of phosphor bronze, the shaft, the screw, and the spacer are made of brass, the case, the base, and the rotor are made of aluminum, and the bush is made of fluororesin.

[0024] However, when used near other imaging devices, when used sufficiently far away from imaging devices, or when magnetic shielding is applied, the injection head 2 and the control device 5 can be made of magnetic materials. Furthermore, the console 6 can also be placed in the examination room if it is made of non-magnetic materials.

[0025] The control device 5 that controls the injection head 2 has a main CPU (Central Processing Unit) that functions as a control unit, a memory section, an FPGA (Field-Programmable Gate Array), a drive circuit, etc. The console 6 connected to the control device 5 has a CPU that functions as a control unit such as a touch panel, and a memory section. The memory sections of the console 6 and the control device 5 have a RAM (Random Access Memory) that is a system work memory for the CPU to operate, a ROM (Read Only Memory) in which a control program or system software, etc. are stored, and a hard disk drive, etc.

[0026] Injection device 1 can be connected to an imaging device (not shown) by wire or wirelessly. When injecting a medicinal liquid and taking an image, various data are transmitted and received between the imaging device and injection device 1. For example, imaging conditions may be set or displayed in injection device 1, or injection conditions may be set or displayed in the imaging device. Examples of such imaging devices include various medical imaging devices such as a magnetic resonance imaging (MRI) device, a computed tomography (CT) device, an angio imaging device, a positron emission tomography (PET) device, a single photon emission computed tomography (SPECT) device, a CT angio device, an MR angio device, an ultrasonic diagnostic device, and a blood vessel imaging device. Injection device 1 can also transmit information on the injection result (injection history) to an external storage device such as a radiology information system (RIS), a picture archiving and communication systems (PACS), and a hospital information system (HIS) via a network and store the information.

[0027] Next, injection of the medicinal liquid will be described. When injecting the medicinal liquid, the operator turns on the power of injection device 1, connects extension tube 900 or the like to the tip of syringe 91, and mounts syringe 91 in syringe holder 92 to complete preparation for injection. Note that the operator may turn on the power of injection device 1 after mounting syringe 91.

[0028] Then, the operator operates the touch panel or input buttons of the console 6 to input data required for creating an injection protocol. For example, the operator inputs physical data of the patient such as weight, height, body surface area, heart rate, and cardiac output, as well as data on the type of medicinal fluid, etc. The injection protocol and data on medicinal fluid, etc. can also be input to the console 6 from an external storage medium.

[0029] The console 6 pre-stores basic injection protocols such as injection speed, injection amount, injection time, and maximum injection pressure (injection pressure limit value), as well as data on the medicinal liquid. The console 6 then determines an individual injection protocol suitable for an individual patient based on the input data and pre-stored data. The operator checks the contents of the determined injection protocol and changes the contents if necessary. The console 6 then transmits the injection protocol confirmed by the operator to the control device 5. The control device 5 temporarily stores the injection protocol received from the console 6. The injection protocol may be locked with a password to prevent a third party from changing it.

[0030] Furthermore, console 6 displays predetermined data such as injection speed, injection amount, and injection time on a touch panel. If injection head 2 has a head display, injection head 2 may display the predetermined data on the head display. Furthermore, control device 5 may cause an external device such as a portable display or tablet computer to display the predetermined data. These devices are wirelessly connected to injection head 2 or control device 5 according to standards such as Bluetooth (registered trademark) and Wi-Fi, and can replace the head display of injection head 2.

[0031] When the operator has completed preparation for injection and confirmed the injection protocol, he or she presses check button 27 on injection head 2 or the check button on console 6. This causes injection head 2 to wait in a state where injection is possible. The operator then presses start button 28 on injection head 2, a button on hand switch 14, or an injection button displayed on the touch panel to start injection. If injection head 2 has a head display, the operator can also start injection by pressing the injection button displayed on the head display. Then, injection head 2 automatically injects the medicinal liquid according to the injection protocol.

[0032] 2, injection device 1 for injecting a medicinal liquid includes ultrasonic motor 3, drive mechanism 4 driven by ultrasonic motor 3, and control device (controller) 5 for controlling ultrasonic motor 3. Drive mechanism 4 and ultrasonic motor 3 are housed in frame 21 of injection head 2 of injection device 1. Frame 21 has two syringe holders 92 for holding two syringes 91. Injection device 1 exemplified in this embodiment is configured to include two syringes 91, but the present invention is not limited to the number of syringes, and can also be applied to a configuration including one syringe, or three or more syringes.

[0033] The control device 5 has a CPU 51 (Central Processing Unit) that controls the ultrasonic motor 3, a drive circuit 52 for applying a voltage to the ultrasonic motor 3, and a timer 54 for measuring the rotation time of the ultrasonic motor 3 or the injection time of the medicinal liquid. The CPU 51 is electrically connected to the drive circuit 52 to transmit a drive signal to the ultrasonic motor 3, and the drive circuit 52 is electrically connected to the ultrasonic motor 3. An encoder 39 is connected to the ultrasonic motor 3, and transmits information such as the number of rotations and the presence or absence of rotation of the ultrasonic motor 3 to the control device 5. In addition, when the side where the syringe holder 92 is located in the frame 21 is defined as the front side, the ultrasonic motor 3 is disposed in the rear portion.

[0034] The driving mechanism 4 is disposed between the syringe holder 92 and the ultrasonic motor 3. The driving mechanism 4 includes a transmission mechanism 47 connected to the shaft 35 of the ultrasonic motor 3, a ball screw (rotation-linear conversion mechanism) 41 connected to the transmission mechanism 47, and an actuator 40 connected to the ball screw 41. The transmission mechanism 47 is connected to a ball screw shaft (rotation shaft) 411 of the ball screw 41, and a ball screw nut (linear part) 412 of the ball screw 41 is connected to the actuator 40. The ball screw nut 412 is screwed into an intermediate portion of the ball screw shaft 411. The transmission mechanism 47 transmits the rotation from the ultrasonic motor 3 to the ball screw shaft 411 by a direct drive method. The transmission mechanism 47 can be configured, for example, by an Oldham type or cross joint type coupling.

[0035] A cylinder outer tube 446 is fixed to the bearing housing (base) 44, surrounding the outer periphery of the ball screw shaft 411 and extending to almost the front end of the ball screw shaft 411. A front base 447 is fixed to the front end of the cylinder outer tube 446, and has an opening through which the actuator 40 advances and retreats. A ball screw nut 412 engages with the ball screw shaft 411, and the ball screw nut 412 advances and retreats in the axial direction by the rotation of the ball screw shaft 411. A nut plate 413 is fixed to the ball screw nut 412. A guide hole 4131 is formed in the nut plate 413, through which a guide shaft 448, which is fixed between 44 and 447 and extends in the axial direction, is slidably inserted. This makes it possible to suppress the rotation of the ball screw nut 412 around its axis, and the ball screw nut 412 can be moved in the axial direction by the rotation of the ball screw shaft 411. An actuator 40 is fixed to the front of the nut plate 413, and is arranged to cover the ball screw shaft 411.

[0036] Optical sensors 449a and 449b are fixed to the inner circumferential surfaces of the front and rear ends of the cylinder outer tube 446, respectively. As shown in FIG. 3, a sensor dog 4132 is formed on the outer periphery of the nut plate 413. The sensor dog 4132 is configured to be in a position to block light to the light receiving parts of the optical sensors 449a and 449b when the nut plate 413 moves in the axial direction to the positions of the optical sensors 449a and 449b. Output signals of the optical sensors 449a and 449b are input to the control device 5, and the movable end of the actuator 40 can be controlled by the control device 5.

[0037] In addition, the sensor dog 4132 is formed in a recess 4133 formed on the outer circumferential surface of the nut plate 413 in a phase different from the position where the guide hole 4131 of the nut plate 413 is formed around the axis. The optical sensors 449a and 449b are fixed so as to protrude from the outside to the inside of the cylinder outer tube 446 through holes penetrating the cylinder outer tube 446 in the radial direction. This makes it possible to install the optical sensors 449a and 449b while maintaining the airtightness of the inside of the cylinder outer tube 446 without increasing the size of the cylinder outer tube 446. In addition, in the mechanism for detecting the position of the actuator 40, the sensor dog 4132 serving as a light-shielding part is formed on the nut plate 413 on the movable part side, and since the movable part does not require input and output of electrical signals, it is suitable for maintaining the airtightness of the inside of the cylinder outer tube 446.

[0038] The transmission mechanism 47 is a rotation transmission mechanism that does not easily transmit axial forces. In addition, the axial reaction force (eccentric reaction force) generated by misalignment between the shafts is weak, so the bearings can bear most of the axial load, and the axial load is approximately constant regardless of the amount of eccentricity between the shafts, so that the load fluctuation on the bearings can be suppressed, i.e., the load fluctuation on the load cell can be suppressed.

[0039] The thrust load detection mechanism in the injection device 1 of this embodiment will be described. The thrust load detection mechanism is a mechanism for detecting a thrust load acting in the axial direction of ball screw shaft 411, and includes angular ball bearing 42, washer-type load cell 43, bearing housing (base) 44, and retainer member 45, which are fixed to ball screw shaft 411. The manner in which ball screw shaft 411 is fixed to frame 21 of injection head 2 so as to be rotatable about its axis will be described with reference to the perspective view of Fig. 4, the exploded perspective view of Fig. 5, and the cross-sectional view of Fig. 6.

[0040] An inner ring 421 of angular ball bearing 42 is fixed to ball screw shaft 411 by inner ring fixing member 46. An outer ring 422 of angular ball bearing 42 is inserted from the ultrasonic motor 3 side into a holding portion 440 of a bearing housing 44 fixed to frame 21 of injection head 2. By fixing (fastening) pressing member 45 to bearing housing 44, washer-type load cell 43 is supported by bearing housing 44. As a result, outer ring 422 and washer-type load cell 43 are sandwiched between pressing member 45 and bearing housing 44 with play in the axial direction. The configuration with play will be described in detail later.

[0041] At least during injection of the drug solution, the axial force (thrust load) applied from the bearing housing 44 to the outer ring 422 is negligibly small compared to the axial force applied from the washer-type load cell 43 to the outer ring 422. More specifically, the outer ring 422 of the angular ball bearing 42 is not inserted into the retaining portion 440 of the bearing housing 44 in a so-called press-fit state. Due to this configuration, the axial force acting on the ball screw shaft 411 as a reaction force when the piston 93 is pushed out by the drive mechanism 4 (when the drug solution is injected) is received by the washer-type load cell 43 and transmitted to the bearing housing 44 via the washer-type load cell 43.

[0042] The shaft 35 of the ultrasonic motor 3 is connected to the ball screw shaft 411 by a transmission mechanism 47, and the rotation from the ultrasonic motor 3 is transmitted to the ball screw shaft 411 by a direct drive system. The ball screw nut 412 moves in a forward direction (front direction, toward the piston 93) or a backward direction (rear direction, toward the ultrasonic motor 3) relative to the ball screw shaft 411 as the ball screw shaft 411 rotates. As a result, the actuator 40 moves linearly (forward and backward) as the ball screw nut 412 moves. That is, when the shaft 35 rotates forward, the actuator 40 moves forward, and when the shaft 35 rotates reversely, the actuator 40 moves backward.

[0043] When injecting a medicinal liquid, a syringe 91 filled with the medicinal liquid is mounted on a syringe holder 92. A piston 93 that is slidable within the syringe 91 is attached to the syringe 91. The syringe 91 is mounted so that the rod of the piston 93 abuts against the tip of the actuator 40. As a result, when the ball screw nut 412 slides forward with the syringe 91 mounted, the actuator 40 pushes the piston 93 forward. When the piston 93 moves forward, the medicinal liquid in the syringe 91 is pushed out and is injected into the patient's body via a catheter (not shown) or the like connected to the tip of the syringe 91. When the ball screw nut 412 moves backward, the actuator 40 pulls the piston 93 backward.

[0044] The console 6 stores an injection protocol as a program for controlling the injection in advance, and the injection of the liquid medicine is automatically performed according to the injection protocol. It is also possible to insert a storage medium in which the injection protocol is stored into the console 6 and to inject the liquid medicine according to the injection protocol read from the storage medium. A preset voltage is applied from the drive circuit 52 to the ultrasonic motor 3 by control according to the injection protocol.

[0045] In this injection protocol, for example, an injection time, an injection speed, an injection amount, and an injection pressure limit value are set. The contents of the injection protocol are displayed on the display, so that the user can confirm the contents of the injection protocol. The control device 5 controls the injection time using a timer 54. Furthermore, the control device 5 may monitor the injection status and automatically stop the injection of the liquid if an abnormality in the injection pressure is detected. For example, a drop in the injection pressure may be due to a disconnection of a joint in the injection piping system, and an increase in the injection pressure may be due to an abnormality such as a bent flexible tube in the injection piping system, a narrowing blockage due to the inclusion of foreign matter, or a narrowing of the flow path. The injection pressure is detected by a washer-type load cell 43.

[0046] Figure 7 is a plan view of the washer-type load cell 43 of the injection device 1 of Example 1, where (a) is a plan view seen from the ultrasonic motor 3 side (right side of Figure 2), and (b) is a plan view seen from the ball screw nut 412 side (left side of Figure 2).

[0047] The outer ring 422 of the angular ball bearing 42 is arranged to be sandwiched between a receiving portion 441 of the bearing housing 44 and a first pressure receiving portion 433 of the washer type load cell 43 with a play in the axial direction. As shown in Figs. 2 to 7, the washer type load cell 43 has a ring-shaped main body 430 having an opening 436 through which the ball screw shaft 411 is inserted. The washer type load cell 43 has a second pressure receiving portion 432 that protrudes radially outward from the outer periphery of the main body 430, and is supported by the bearing housing 44 by fixing the pressing member 45 to the bearing housing 44 through a through hole 435 formed in the second pressure receiving portion 432. That is, the washer type load cell 43 has a pressure receiving portion that receives an axial force (force in a first direction) from the angular ball bearing 42 side on one side in the axial direction, and a plurality of support portions that resist the force in the first direction on the other side.

[0048] In the first embodiment, the pressing member 45 is formed of a screw (first screw), and the pressing member 45 is screwed into a screw hole (first screw hole) 442 of the bearing housing 44, thereby fixing the washer-type load cell 43 to the bearing housing. In the present embodiment, the second pressure receiving portion 432 and the screw hole 442 are formed at four locations at approximately equal intervals in the circumferential direction, but the present invention is not limited to this, and they may be formed at two or three locations at approximately equal intervals in the circumferential direction.

[0049] The washer-type load cell 43 has a pair of strain gauges (detection means) 434 installed on both sides in the axial direction at a substantially central position (intermediate position) between at least a pair of adjacent second pressure receiving parts 432. In the washer-type load cell 43, opposing forces in the axial direction act on the first pressure receiving part 433 and the four second pressure receiving parts 432.

[0050] The first pressure receiving portion 433 is configured in a ring shape along the opening 436. The force from the outer ring 422 received by the first pressure receiving portion 433 is distributed to four second pressure receiving portions 432 located radially outward from the first pressure receiving portion 433, so that a large strain is generated at the position of the strain gauge 434 arranged between the second pressure receiving portions 432 in the circumferential direction. In particular, the washer-type load cell 43 of this embodiment has the second pressure receiving portions 432 protruding radially outward from the periphery. Therefore, the length between the adjacent second pressure receiving portions 432 is long, and the axial force acting on the angular ball bearing 42 can be detected more sensitively through the strain detected by the strain gauge 434.

[0051] In addition, a recess 431 may be formed in the portion of the washer-type load cell 43 where the strain gauge 434 is installed so that the axial thickness of the washer-type load cell 43 is reduced. By installing the strain gauge 434 in the recess 431 formed in the washer-type load cell 43, it becomes possible to detect the axial force acting on the angular ball bearing 42 more sensitively through the strain detected by the strain gauge 434. However, the present invention is not limited to a configuration having the recess 431. In addition, the strain gauge 434 is installed on both sides of the washer-type load cell 43 in the axial direction to form a strain gauge bridge, thereby achieving temperature compensation, increased output voltage (high sensitivity), and high accuracy.

[0052] 7, the strain gauges 434 are installed at two locations facing each other with respect to the axis, but the number and arrangement are not necessarily limited to this. The strain gauges 434 are arranged in recesses 431 formed between adjacent second pressure receiving parts 432. The recesses 431 are formed between each of the adjacent second pressure receiving parts 432, but which recess 431 the strain gauge 434 is arranged in may be appropriately selected depending on the needs of wiring when fixing the washer type load cell 43 to the bearing housing 44, etc.

[0053] 8(a) shows an example in which a first pressure receiving portion 4331 is composed of a plurality of protrusions extending toward the center of an opening 436 through which a ball screw shaft 411 passes, only during the phase of the position of the second pressure receiving portion 432 around the axis of the washer-type load cell 43. Fig. 8(b) shows an example in which a position 4333 of the phase of the second pressure receiving portion 432 in Fig. 7 is thinned around the axis of the washer-type load cell 43, so that the outer ring 422 and the washer-type load cell 43 do not come into contact, and only the portion of the phase at the intermediate position comes into contact as the first pressure receiving portion 4332.

[0054] 8(a) and (b) is composed of a plurality of first pressure receiving parts spaced apart from each other in the circumferential direction, each of which is made up of a part of a ring shape along the opening 436. The plurality of first pressure receiving parts 433 and the plurality of second pressure receiving parts 432 are disposed at intermediate positions between each other in the circumferential direction around the opening 436. Therefore, in the configuration shown in FIGS. 8(a) and (b), the strain gauge 434 is disposed at a position in phase with the first pressure receiving parts 4331 and 4332 in the circumferential direction around the opening 436.

[0055] 8(a) and 8(b), the washer-type load cell 43 does not receive the axial force from the outer ring 422 of the angular ball bearing 42 over the entire circumference around the axis. In the washer-type load cell 43, the positions of the first pressure-receiving parts 4331 and 4332 and the position of the second pressure-receiving part 432 are out of phase with each other in the circumferential direction. Therefore, a larger strain appears at the position of the strain gauge 434, and the strain (force) can be detected with high sensitivity and high accuracy.

[0056] The support of the washer-type load cell 43 on the bearing housing 44 by the retainer member 45 will now be described. 9 shows an enlarged image of the holding member 45. The holding member 45 has a head 451 that can be rotated by engaging with a tool such as a screwdriver, a threaded portion 455 that screws into the threaded hole 442 of the bearing housing 44, and a fitting portion 453 between the head 451 and the threaded portion 455. The fitting portion 453 has an outer diameter that is smaller than the outer diameter of the head 451, larger than the outer diameter of the threaded portion 455, and larger than the inner diameter of the threaded hole 442 of the bearing housing 44. The axial length of the fitting portion 453 is larger than the axial thickness of the washer-type load cell 43.

[0057] Therefore, when the threaded portion 455 of the pressing member 45 is screwed into the threaded hole 442 of the bearing housing 44 and fixed, the end face 454 of the fitting portion 453 abuts against the ring-shaped receiving surface 443 (see FIG. 5) of the bearing housing 44. In this state, the washer-type load cell 43 is held in the bearing housing 44 with play in the axial direction corresponding to the difference between the axial length of the fitting portion 453 and the axial thickness of the washer-type load cell 43.

[0058] In this way, washer-type load cell 43 is fixed to bearing housing 44 with some play in the axial direction, so there is no need to manage the pressure during assembly, and the effects of deformation due to manufacturing errors, temperature changes, etc. on strain detection can be suppressed. When used in an injection device for medical applications, it is used with a constant load of at least a certain amount being applied in the axial direction of ball screw shaft 411. Therefore, washer-type load cell 43 is used with its face abutting and pressed against end face 452 of head 451 of pressing member 45, so this play does not pose a problem.

[0059] When the injection device is used while controlling the injection speed at a very low level, it is necessary to stabilize the detection of strain at low pressure. For this purpose, a spring washer or other elastic material may be inserted between the washer-type load cell 43 and the bearing housing 44, or between the washer-type load cell 43 and the retainer member 45, or another member may be inserted between them to apply pressure and maintain constant contact.

[0060] By using the washer-type load cell 43 of this embodiment, it is not necessary to place a load cell on the axial extension of the actuator 40 to measure the injection pressure, and the axial size of the injection device can be reduced. In addition, it is possible to avoid problems such as the need to lay signal wiring from the moving part, which occurs when the load cell is sandwiched between the actuator 40 and the piston in the axial direction, and the associated difficulty in maintaining airtightness of the actuator. In addition, the washer-type load cell 43 of the present invention has the effect of being easily accessible for replacement, maintenance, etc. from the rear of the frame 21 (the ultrasonic motor 3 side). EXAMPLES

[0061] A detailed description will be given of injection device 1 according to the second embodiment. Fig. 10 is a block diagram of injection device 1 according to the second embodiment. Injection device 1 of embodiment 2 differs from injection device 1 of embodiment 1 in the mechanism for fixing washer-type load cell 43 to bearing housing 44. Explanation of the same configuration as in embodiment 1 will be omitted, and only the configuration different from embodiment 1 will be explained.

[0062] The manner in which ball screw shaft 411 is fixed to frame 21 of injection head 2 so as to be rotatable about its axis in injection device 1 of this embodiment will be described with reference to the exploded perspective views of FIGS. 11(a) and (b).

[0063] In the second embodiment, the pressing member that holds the washer-type load cell 43 in the bearing housing 44 is composed of a ring-shaped pressing member (ring-shaped pressing member) 48 and a screw (second screw) 49. The pressing member 48 has a through hole 483 that passes through in the axial direction. The pressing member 48 is fixed to the bearing housing 44 by threading the screw 49 into a screw hole (second screw hole) 445 of the bearing housing 44 through the through hole 483.

[0064] When the pressing member 48 is fixed to the bearing housing 44, a surface 484 of the pressing member 48 is pressed against a surface 444 of the bearing housing 44. The pressing member 48 is provided with abutment surfaces (abutment portions) 482 that abut against and support the surfaces of the four second pressure-receiving portions 432 of the washer-type load cell 43 during injection, and the abutment surfaces (abutment portions) 482 are formed at positions recessed in the axial direction with respect to the surfaces 484.

[0065] At least one of the contact surfaces 482 is formed with a convex portion 481 that is convex in the axial direction. The convex portion 481 engages with a through hole 435 that passes through the second pressure receiving portion 432 of the washer-type load cell 43 in the axial direction with some play in the radial direction of the through hole 435. This allows the washer-type load cell 43 to be positioned relative to the pressing member 48 in a plane perpendicular to the axial direction and the rotation direction around the axis.

[0066] The axial thickness of the washer-type load cell 43 is smaller than the distance between the receiving surface 443 of the bearing housing 44 and the abutment surface 482 of the presser member 48 when the presser member 48 is fixed to the bearing housing 44. Therefore, when the presser member 48 is fixed to the bearing housing 44, the washer-type load cell 43 is supported between the receiving surface 443 of the bearing housing 44 and the abutment surface 482 of the presser member 48 with some play in the axial direction.

[0067] In this way, the washer-type load cell 43 is fixed to the bearing housing 44 with some play in the axial direction, so that the influence of initial strain during assembly, manufacturing errors, deformation due to temperature changes, etc. on strain detection can be suppressed. When the injection device is used for injection, the ball screw shaft 411 is always used with a certain or higher load applied in the axial direction. Therefore, the washer-type load cell 43 is used in a state where its face is in contact with and pressed against the contact surface 482 of the pressing member 48, so this play does not cause a problem.

[0068] When the injection device is used while controlling the injection speed at a very low level, it affects the strain detection performance at low pressure. Therefore, it is possible to insert an elastic material such as a spring washer between the washer-type load cell 43 and the bearing housing 44, or between the washer-type load cell 43 and the pressing member 48, or to sandwich them with other members to apply pressure and maintain constant contact.

[0069] In this embodiment, the contact surface 482 with which the surface of the second pressure receiving portion 432 of the washer-type load cell 43 comes into contact is formed of the same material as the pressing member 48. Therefore, the contact surface 482 is formed in the same plane, and the surface of the second pressure receiving portion 432 of the washer-type load cell 43 can be pressed with a more uniform pressing force, enabling more accurate detection of strain. EXAMPLES

[0070] FIG. 12 shows a block diagram of an injection device using a washer-type load cell according to the third embodiment.

[0071] The basic configuration of the injection device 1 using the washer-type load cell of Example 3 is the same as that of Example 1. However, the injection device 1 of Example 3 is different from the injection device 1 of Example 1 shown in FIG. 2 in that it has a detection unit 403 fixed to a pressing unit 401 and a guide pipe 402 that guides a signal line from the detection unit 403 to a nut plate 413. The guide pipe 402 extends from the pressing unit 401 at the tip of the actuator 40 to the nut plate 413, and is fixed to the pressing unit 401 and the nut plate 413. Therefore, the guide pipe 402 slidably passes through a through hole 447a that passes through the front base 447 in the axial direction, and moves together with the forward and backward movement of the actuator 40.

[0072] A signal line from the detection unit 403 passes through the guide pipe 402, is guided to the nut plate 413, and comes out of the cylinder outer tube 446 at the nut plate 413. For this reason, a long hole 446a is formed in the cylinder outer tube 446 at the guide pipe 402 portion, penetrating in the radial direction, in the axial range in which the nut plate 413 of the cylinder outer tube 446 moves. By forming the long hole 446a in the cylinder outer tube 446, it is possible to easily route the signal line coming out from the rear end (ultrasonic motor 3 side) of the guide pipe 402 as the actuator 40 moves forward and backward. The signal line from the detection unit 403 coming out from the rear end of the guide pipe 402 is connected to the CPU 51.

[0073] The detection unit 403 may be, for example, a detection unit that detects the distance between the pressing unit 401 and the rear end of the piston 93, or a predetermined proximity state. This makes it possible to prevent the actuator 40 from being moved forward excessively and pushing out unnecessary liquid medicine when preparing for injection by moving the actuator 40 forward with respect to the syringe 91 set in the syringe holder 92. The CPU 51 can control the drive circuit 52 so as to control the amount of extrusion (amount of advance) of the actuator 40 based on a signal from the detection unit 403. The detection unit 403 in this case may be a contact type detection unit, or may be, for example, an optical non-contact detection unit.

[0074] Furthermore, detection unit 403 may be, for example, a detection unit for detecting the injection pressure disposed between pressing unit 401 and the rear end of piston 93. This allows detection unit 403 to be used as a backup for washer-type load cell 43, and can be used as a backup for measuring the injection pressure when washer-type load cell 43 breaks down or becomes defective, thereby improving the reliability of the injection device. For example, in this case, detection unit 403 can be composed of a strain gauge.

[0075] Furthermore, detection unit 403 may be a detection unit for purposes other than those exemplified above. For example, detection unit 403 may be a detection unit that identifies the type or ID of syringe 91 set in syringe holder 92.

[0076] By configuring an imaging system that includes an injection device according to the present invention that injects a contrast agent and an imaging device that is connected to the injection device via a wired or wireless connection and that images a subject, it is possible to realize an imaging system that enjoys the effects of the present invention. [Explanation of symbols]

[0077] 411: Ball screw shaft (shaft) 43: Washer type load cell 430: Main body 432: Second pressure receiving part 433, 4331, 4332: First pressure receiving part 434: Strain gauge (detection means) 436: Opening

Claims

1. A washer-type load cell comprising: a body having an opening into which a rotating shaft is inserted; and a detection means fixed to the body for detecting a strain of the body, the main body has a first pressure receiving portion on one side in the axial direction of the rotation shaft, the first pressure receiving portion receiving a force in a first direction in the axial direction, and a plurality of second pressure receiving portions on the other side in the axial direction, the second pressure receiving portions resisting the force in the first direction, the second pressure receiving portions and the detection means are disposed at positions radially farther from the center of the opening than the first pressure receiving portion, The washer-type load cell is characterized in that the detection means is disposed at a middle position between at least one pair of adjacent second pressure receiving portions in a circumferential direction around the opening.

2. 2. The washer-type load cell according to claim 1, wherein the second pressure receiving portions are disposed at positions farther in a radial direction from a center of the opening than the detection means.

3. 2. The washer-type load cell according to claim 1, wherein the first pressure-receiving portion is in a ring shape that conforms to the opening.

4. 2. The washer-type load cell according to claim 1, wherein the first pressure-receiving portion is made up of a plurality of first pressure-receiving portions spaced apart from one another in the circumferential direction and each of which is formed of a part of a ring shape along the opening.

5. 5. The washer-type load cell according to claim 4, wherein the first pressure-receiving portions and the second pressure-receiving portions are disposed at intermediate positions between each other in a circumferential direction around the opening.

6. 5. The washer-type load cell according to claim 4, wherein the plurality of first pressure receiving portions are constituted by a plurality of protrusions extending toward the center of the opening.

7. 2. The washer-type load cell according to claim 1, wherein the first pressure-receiving portion is made of a part of a ring shape formed by changing the thickness in the axial direction along the opening, and is made of a plurality of parts spaced apart from each other in the circumferential direction.

8. 2. The washer-type load cell according to claim 1, wherein the detection means are arranged at opposing positions across the opening in a circumferential direction around the opening.

9. 2. The washer-type load cell according to claim 1, wherein the detection means is disposed on the one side and the other side of the body in the axial direction at the same circumferential position around the opening.

10. 2. The washer-type load cell according to claim 1, wherein the plurality of second pressure-receiving portions are disposed at four locations at equal intervals in a circumferential direction around the opening.

11. 2. The washer-type load cell according to claim 1, wherein the plurality of second pressure-receiving portions are disposed at three locations equidistant from one another in a circumferential direction around the opening.

12. 2. The washer-type load cell according to claim 1, wherein the plurality of second pressure-receiving portions are disposed at two locations equidistant from each other in a circumferential direction around the opening.

13. 5. The washer-type load cell according to claim 4, wherein the detection means is disposed at a position in phase with the first pressure-receiving portion in a circumferential direction around the opening.

14. 8. The washer-type load cell according to claim 7, wherein the detection means is disposed at a position in phase with the first pressure-receiving portion in a circumferential direction around the opening.

15. A washer-type load cell according to any one of claims 1 to 14, a bearing having an inner ring fixed to the rotating shaft and an outer ring that abuts against the first pressure receiving portion of the washer-type load cell to transmit a thrust load acting on the rotating shaft; a pressing member against which the second pressure receiving portions of the washer-type load cell come into contact; A base to which the pressing member is fixed; having A thrust load detection mechanism, characterized in that the washer-type load cell is fixed to the base with play in the axial direction when there is no thrust load.

16. the retaining member is a first screw, The thrust load detection mechanism according to claim 15, characterized in that, in a state in which the first screw is threadedly engaged with the first screw hole of the base through the axial through hole formed in the second pressure receiving portion and fixed thereto, the washer-type load cell is fixed to the base with play in the axial direction.

17. the pressing member includes a ring-shaped pressing member having contact portions that contact the second pressure-receiving portions of the washer-type load cell, and a second screw that fixes the ring-shaped pressing member to the base, the second pressure-receiving portion has a through hole in the axial direction, At least one of the contact portions of the ring-shaped pressing member has a protrusion that engages with the through hole with play in the radial direction, The thrust load detection mechanism according to claim 15, characterized in that when the second screw is screwed into the second screw hole of the base and the ring-shaped pressing member is fixed to the base, the washer-type load cell is held relative to the base with play in the axial direction.

18. An injection device for injecting a medicinal solution, A syringe for filling the drug solution; a syringe holder on which the syringe is mounted; An ultrasonic motor; The thrust load detection mechanism according to claim 15, a rotary-linear motion conversion mechanism that converts the rotation of the rotary shaft connected to the ultrasonic motor into linear motion of a linear motion part; a piston connected to the linear motion unit of the rotary-linear motion conversion mechanism and configured to push out the liquid medicine from the syringe; and a control unit that controls the drive of the ultrasonic motor based on a signal detected by the detection means of the washer-type load cell of the thrust load detection mechanism, and controls the injection of the medicinal liquid from the syringe.

19. An injection device for injecting the contrast agent according to claim 18; an imaging device connected to the injection device by wire or wirelessly, and configured to capture an image of a subject;

Images