JP7224260B2 - Load detector - Google Patents

Description

The present disclosure relates to load detection devices.

2. Description of the Related Art Load cells (strain gauges, semiconductor gauges) have been widely used as load detection devices for detecting and measuring loads acting on objects. In this type of device, load cells are mounted along the surface of the object. For example, when a strain gauge is used, the output voltage of the strain gauge changes based on the magnitude of the relative displacement caused by the load between the ends of the strain gauge. This change in voltage enables detection and measurement of the load applied to the object.

Here, the maximum value of the load that can be measured by the load detection device is determined based on the maximum load that can occur in the usage environment of the object. Therefore, it is necessary to increase the rigidity of the object as the value of the maximum load increases. However, when the rigidity is increased in this way, the amount of deformation of the object itself becomes small, so it becomes difficult for the strain gauge to capture a minute load. As a result, there is a possibility that the desired measurement accuracy of the load detection device cannot be ensured. In particular, when the load applied to the object includes an average load as a component that is normally applied and a fluctuating load as a fluctuating component that is superimposed on this average load, it is difficult to detect and measure the fluctuating load. .

Therefore, as described in Patent Literature 1 below, for example, a technique has been proposed in which a preload (load reaction force) is applied to an object in advance by a coil spring to offset the average load as described above. It is said that this makes it possible to detect and measure fluctuating loads without being affected by the average load.

JP-A-2005-114599

However, in the device described in Patent Document 1, the magnitude of the preload is uniquely determined by the characteristics of the selected coil spring. Therefore, depending on the magnitude of the average load, for example, preload cannot be generated appropriately. As a result, there is a risk that the usable range of the load detection device will be limited.

The present disclosure has been made to solve the above problems, and an object thereof is to provide a load detection device that can be applied to a wider range of loads.

In order to solve the above problems, a load detection device according to the present disclosure provides a load including an average load directed from one side to the other side in a first direction and a fluctuating load superimposed on the average load. a supporting portion that supports a rotating shaft as a load portion with respect to a reference plane in a displaceable state in the first direction; an opposite load generator that applies an opposite load that can be changed based on the The rotary shaft includes a columnar shaft body centered on an axis, a cylindrical outer peripheral member through which the shaft body is inserted, and an end on one side in the first direction that protrudes radially outward from the shaft body. and a flange portion that abuts on the outer peripheral member, and the opposite load generating portion applies a force toward the one side of the first direction to the outer peripheral member, so that the The opposite load is applied to the rotating shaft .

According to the present disclosure, it is possible to provide a load detection device that can be applied to a wider range of loads.

1 is a cross-sectional view showing the configuration of a load detection device according to a first embodiment of the present disclosure; FIG. It is the figure which looked at the load detection device concerning the first embodiment of this indication from the direction of an axis. FIG. 10 is a cross-sectional view showing a first modification of the load detection device according to the first embodiment of the present disclosure; FIG. 5 is a cross-sectional view showing a second modification of the load detection device according to the first embodiment of the present disclosure; FIG. 11 is a cross-sectional view showing a third modification of the load detection device according to the first embodiment of the present disclosure; FIG. 4 is a cross-sectional view showing the configuration of a load detection device according to a second embodiment of the present disclosure; FIG. 10 is a cross-sectional view showing the configuration of a load detection device according to a third embodiment of the present disclosure;

<First Embodiment>
(Configuration of load detection device)
A load detection device according to a first embodiment of the present disclosure will be described below with reference to FIGS. 1 and 2. FIG. As shown in FIG. 1, the load detection device 100 according to the present embodiment includes a support portion 2 provided on the outer peripheral side of a rotating shaft 1 (loaded portion) extending along an axis A1 extending in a first direction; A casing 3 that covers the rotating shaft 1 and the support portion 2 from the outer peripheral side, a fixing member 4 that fixes the support portion 2 to the inner peripheral surface of the casing 3, an opposite load generation portion 5, and a deformation amount detection portion 6 and a strain gauge G.

(Structure of rotating shaft)
The rotary shaft 1 has a columnar shaft body 11 centered on the axis A1 and a cylindrical outer peripheral member 12 through which the shaft body 11 is inserted. The shaft body 11 is rotatable around the axis A1. The outer peripheral member 12 rotatably supports the shaft body 11 . Although not shown in detail, a bearing device is provided between the inner peripheral surface of the outer peripheral member 12 and the outer peripheral surface of the shaft body 11 . Furthermore, an annular flange portion 11</b>F projecting radially outward from the shaft body 11 is provided at one end of the shaft body 11 in the first direction. The end surface of the flange portion 11</b>F on the other side in the first direction is in contact with the outer peripheral member 12 .

As indicated by the arrow in FIG. 1 , a load is applied to the rotating shaft 1 in the first direction from one side to the other side due to an external force or the like. Specifically, this load is the sum of the average load Favg and the fluctuating load ΔF superimposed thereon. The average load Favg is a component that exhibits a constant magnitude regardless of time. The fluctuating load ΔF is a component that fluctuates with time. Although the details will be described later, the load detection device 100 according to the present embodiment is used to detect and measure such loads.

(Structure of support part)
The support portion 2 protrudes radially outward from the outer peripheral surface of the outer peripheral member 12 with respect to the axis A1. In this embodiment, a plurality of support portions 2 are provided at intervals in the first direction. Further, as shown in FIG. 2, in this embodiment, four support portions 2 are provided at equal intervals in the circumferential direction with respect to the axis A1. That is, in this embodiment, a total of eight support portions 2 are provided. The radially outer end portions of the support portions 2 are fixed to the inner peripheral surface of the fixing member 4 . The fixed member 4 has a cylindrical shape centered on the axis A1. Furthermore, this fixing member 4 is fixed to the inner peripheral surface of the casing 3 . The casing 3 has a cylindrical shape centered on the axis A1, and accommodates the rotary shaft 1, the support portion 2, and the fixed member 4 therein. The inner peripheral surface of the casing 3 is used as a reference surface Sg.

(Structure of Opposite Load Generating Part)
An opposite load generating portion 5 is provided on the other side in the first direction along the axis A1 (that is, on the side opposite to the direction of the load described above). The opposite load generator 5 is provided to offset the average load Favg among the components included in the load. The opposite load generating portion 5 includes an iron core 51 integrally provided on the outer peripheral surface of the outer peripheral member 12, a holder portion 52H fixed to the inner peripheral surface (reference plane Sg) of the casing 3, and the holder portion 52H. and a coil portion 52C provided on the inner peripheral side of. The coil portion 52C faces the iron core 51 with a gap in the radial direction. The coil portion 52C generates an electromagnetic force by an induced current with the iron core 51 by electric power supplied from the outside. This electromagnetic force is transmitted to the shaft body 11 via the flange portion 11F. The magnitude of the electromagnetic force can be adjusted by changing the amount of current supplied to the coil portion 52C.

(Structure of Deformation Detector)
A strain gauge G is attached to the surface of the support portion 2 as a deformation amount detection portion 6 . The strain gauge G changes its output voltage as the support portion 2 deforms. The amount of deformation of the support portion 2 is detected by capturing changes in voltage with an external measuring device (not shown). It should be noted that the strain gauges G may be provided on all the support portions 2 one by one, or may be provided on some of the support portions 2 only. Further, as the deformation amount detection unit 6, instead of the strain gauge G, it is possible to use a semiconductor gauge.

(Effect)
Next, the operation of the load detection device 100 according to this embodiment will be described. As described above, the rotating shaft 1 is applied with a load directed from one side to the other side in the first direction. Due to this load, the rotating shaft 1 is slightly displaced toward the other side in the first direction. As the rotating shaft 1 is displaced, the supporting portion 2 is deformed. Specifically, the support portion 2 inclines toward the other side in the first direction as it goes radially inward. Such deformation can be captured by the strain gauge G described above.

Here, the maximum value of the load that can be measured by the load detection device 100 is determined based on the maximum load that can occur in the usage environment of the object. Therefore, it is necessary to increase the rigidity of the object as the value of the maximum load increases. In the example of this embodiment, it is necessary to increase the rigidity of the support portion 2 . However, when the rigidity is increased in this way, the amount of deformation of the object itself becomes small, so it becomes difficult for the strain gauge to capture a minute load. As a result, there is a possibility that the desired measurement accuracy of the load detection device cannot be ensured. In particular, when the load applied to the object includes an average load Favg as a normally applied component and a fluctuating load ΔF as a fluctuating component superimposed on the average load Favg, the fluctuating load ΔF is detected and measured. difficult to do

Therefore, in the present embodiment, a configuration is adopted in which the opposite load generator 5 applies another load (opposite load Fr) to the rotating shaft 1 from a direction opposite to the load. This opposite load has the same magnitude as the average load Favg, and the direction in which it is applied is opposite to the load. That is, the opposite load Fr is equal to -Favg.

Thus, the average load Favg applied to the rotating shaft 1 as the load receiving portion can be offset by the opposite load Fr generated by the opposite load generating portion 5 . In this state, the strain gauge G as the deformation amount detector 6 detects the deformation amount due to the fluctuating load ΔF generated in the support portion 2 . Therefore, the fluctuating load ΔF can be precisely detected and measured without being affected by the magnitude of the average load Favg. In particular, the magnitude of the counterload Fr generated by the counterload generator 5 can be changed based on the magnitude of the average load Favg. Therefore, the fluctuating load ΔF can be precisely detected in a wider range according to the environmental conditions (magnitude of the assumed maximum load and average load Favg) in which the load detection device 100 is used. In other words, the range of loads to which the load detection device 100 can be applied can be widened.

Furthermore, according to the above configuration, the opposite load generating portion 5 can apply the opposite load Fr to the rotating shaft 1 based on the electromagnetic force generated between the iron core 51 and the coil portion 52C. That is, the magnitude of the opposite load Fr can be adjusted only by changing the magnitude of the current flowing through the coil portion 52C. As a result, the accuracy of detection and measurement can be further improved, and the range of loads to which the load detection device 100 can be applied can be further widened.

<First modification>
As a first modified example of the load detection device 100 described above, it is also possible to adopt the configuration shown in FIG. In the example of FIG. 3, a load cell Lc is used as the deformation amount detector 6b instead of the strain gauge G described above. Specifically, a piezoelectric load cell is preferably used as the load cell Lc. The load cell Lc changes its output voltage according to the compressive force or tensile force applied to itself. Further, in the example shown in the figure, the support portion 2b includes a first member 21 provided on the side of the reference plane Sg (that is, the fixing member 4), and a first member 21 on the other side in the first direction with respect to the first member 21. and a second member 22 spaced apart and fixed to the outer peripheral surface of the outer peripheral member 12 . The load cell Lc is sandwiched between the first member 21 and the second member 22 .

In the above configuration, when a fluctuating load ΔF is applied to the rotating shaft 1, the relative distance between the first member 21 and the second member 22 changes based on the fluctuating load ΔF. The change in this relative distance changes the output voltage of the load cell Lc. By detecting this voltage change with an external measuring device or the like, the magnitude of the fluctuating load ΔF can be measured more precisely.

<Second modification>
Furthermore, as a second modified example, it is possible to employ the configuration shown in FIG. In the example of FIG. 4, while the supporting portion 2 has the same configuration as that of the first embodiment, the configuration of the opposite load generating portion 5b differs from that of the first embodiment and the first modified example. Specifically, the opposite load generating portion 5b has a solenoid 53 provided between the holder portion 52H and the outer peripheral member 12 described above. Specifically, a push-pull solenoid is preferably used as the solenoid 53 . This type of solenoid 53 can generate compressive force or tensile force by changing its length according to the magnitude of power supplied from the outside.

According to the above configuration, based on the force generated by the solenoid 53, the opposite load Fr can be applied to the rotary shaft 1 as the load receiving portion. In particular, the magnitude of the counterload Fr can be adjusted only by changing the magnitude of the current flowing through the solenoid 53 . This makes it possible to further improve the accuracy of detection and measurement.

<Third modification>
As a third modified example, it is also possible to employ the configuration shown in FIG. In the example of FIG. 5, a configuration is adopted in which the deformation amount detecting portion 6b having the load cell Lc described in the first modified example and the opposite load generating portion 5b having the solenoid 53 described in the second modified example are combined. there is With such a configuration as well, it is possible to obtain the same effects as those of the first embodiment, and to further improve the accuracy of detection and measurement.

<Second embodiment>
Next, a load detection device 200 according to a second embodiment of the present disclosure will be described with reference to FIG. In addition, the same code|symbol is attached|subjected about the structure similar to said 1st embodiment and its modification, and detailed description is abbreviate|omitted. As shown in FIG. 6, the support portion 2c according to this embodiment further includes a third member 23 in addition to the first member 21 and the second member 22 described in the first modified example. . The third member 23 is supported so as to be relatively displaceable in the first direction with respect to the first member 21 . Specifically, the third member 23 is supported and fixed to the fixed member 4 by a feed screw B as the counterload generating portion 5c. Also, the third member 23 is in contact with the reference surface Sg in a slidable manner. Therefore, by changing the screwing amount of the feed screw B, it is possible to adjust the relative position of the third member 23 with respect to the fixed member 4 and the first member 21 . In other words, by screwing the feed screw B, the opposite load Fr can be applied to the rotating shaft 1 .

Further, between the second member 22 and the third member 23, another load cell Lc is provided as the deformation amount detection section 6. As shown in FIG. That is, in this embodiment, load cells Lc are provided between the first member 21 and the second member 22 and between the second member 22 and the third member 23 as well. In the following description, the load cell Lc provided between the first member 21 and the second member 22 is called the first load cell Lc1, and the load cell provided between the second member 22 and the third member 23 is called the first load cell Lc1. Lc is called a second load cell Lc2.

In the above configuration, a compressive force due to the opposite load Fr is normally applied to these load cells Lc. In this state, for example, when the second member 22 provided on the rotating shaft 1 side as a load receiving portion is displaced to the other side in the first direction (that is, a fluctuating load ΔF directed from one side to the other side is generated case), a tensile force is applied to the first load cell Lc1 on one side, and a further compressive force is applied to the second load cell Lc2 on the other side. Here, it is generally known that a load cell can sufficiently withstand compressive force, but is weak against tensile force. This tendency is particularly noticeable in piezoelectric load cells. However, in the above configuration, the compressive force due to the opposite load Fr is also applied in advance to the first load cell Lc1 on one side to which the tensile force is applied. Therefore, when a tensile force due to displacement as described above is applied, the compressive force and the tensile force cancel each other out. As a result, the first load cell Lc1 on the one side is not deformed from the initial state due to the tension, or is only slightly deformed. As a result, detection/measurement can be performed with a margin to the durability limit of the load cell Lc. In other words, the durability limit required for the load cell Lc can be kept low. As a result, the manufacturing cost and maintenance cost of the device can be reduced.

Furthermore, according to the above configuration, by changing the screwing amount of the feed screw B, it is possible to easily and precisely adjust the magnitude of the counterload Fr. Further, since the opposite load generating portion 5c can be configured only by providing the feed screw B, the configuration of the device can be simplified and the cost can be reduced accordingly.

<Third Embodiment>
Next, a load detection device 300 according to a third embodiment of the present disclosure will be described with reference to FIG. In addition, the same code|symbol is attached|subjected about the structure similar to said each embodiment and each modification, and detailed description is abbreviate|omitted. As shown in FIG. 7, in this embodiment, in place of the configuration of the second embodiment, the opposing load generating section 5d includes a solenoid 53b provided between the third member 23 and the fixed member 4 described above. have. Specifically, the push-pull solenoid described above is preferably used as the solenoid 53b. The length of the solenoid 53b changes according to the power supplied from the outside. Therefore, for example, when the solenoid 53b is contracted, a load is applied to the load cell Lc and the second member 22 via the third member 23. This load is transmitted to the rotating shaft 1 via the second member 22 . That is, the opposite load Fr can be applied to the rotating shaft 1 .

According to the above configuration, in addition to the same effects as the second embodiment, by changing the forward/backward amount (length) of the solenoid 53b, the magnitude of the opposite load Fr can be easily and precisely adjusted. can. In addition, since the opposite load generating section 5d can be configured only by providing the solenoid 53b, it is possible to simplify the configuration of the device and reduce costs based thereon.

The embodiments of the present disclosure and their modifications have been described in detail above with reference to the drawings. Note that the specific configuration is not limited to this embodiment and its modifications, and includes design changes and the like that do not deviate from the gist of the present disclosure.
For example, in each of the above-described embodiments and modifications thereof, the rotating shaft 1 is used as an example of the load-bearing portion. However, the load receiving portion is not limited to the rotating shaft 1, and any device or part exposed to a load acting in a specific direction can be used as the load receiving portion.

<Appendix>
The load detection device described in each embodiment is understood as follows, for example.

(1) In the load detection device 100 according to the first aspect, a load including an average load Favg directed from one side to the other side in the first direction and a fluctuating load ΔF superimposed on the average load Favg is applied. a supporting portion 2 that supports the load receiving portion 1 with respect to the reference plane Sg in a state displaceable in the first direction; and a deformation amount detection unit that detects the amount of deformation due to the fluctuating load ΔF generated in the support portion 2. 6 and .

According to the above configuration, the average load Favg applied to the load receiving portion 1 can be offset by the opposite load Fr generated by the opposite load generating portion 5 . In this state, the deformation amount detection unit 6 detects the deformation amount caused by the fluctuating load ΔF generated in the support member 2 . Therefore, the fluctuating load ΔF can be precisely detected and measured without being affected by the magnitude of the average load Favg. In particular, the magnitude of the counterload Fr generated by the counterload generator 5 can be changed based on the magnitude of the average load Favg. Therefore, the fluctuating load ΔF can be precisely detected in a wider range according to the environmental conditions (magnitude of the assumed maximum load and average load Favg) in which the load detection device 100 is used.

(2) In the load detection device 100 according to the second aspect, the opposite load generating portion 5 is provided on the iron core 51 provided in the load receiving portion 1 and on the reference plane Sg side. and a coil portion 52</b>C that applies an electromagnetic force as the opposite load Fr to the load receiving portion 1 by facing the .

According to the above configuration, the opposite load Fr can be applied to the load receiving portion 1 based on the electromagnetic force generated between the iron core 51 as the opposite load generating portion 5 and the coil portion 52C. In particular, the magnitude of the opposite load Fr can be adjusted only by changing the magnitude of the current flowing through the coil portion 52C. This makes it possible to further improve the accuracy of detection and measurement.

(3) In the load detection device 100 according to the third aspect, the opposite load generating portion 5b is provided between the reference plane Sg and the load receiving portion 1, and is arranged opposite to the load receiving portion 1. It is the solenoid 53 that gives the load Fr.

According to the above configuration, the opposite load Fr can be applied to the load receiving portion 1 based on the force generated by the solenoid 53 . In particular, the magnitude of the counterload Fr can be adjusted only by changing the magnitude of the current flowing through the solenoid 53 . This makes it possible to further improve the accuracy of detection and measurement.

(4) In the load detection device 100 according to the fourth aspect, the support portion 2b includes the first member 21 provided on the reference plane Sg side and the deformation amount detection portion 6b with respect to the first member 21. and a second member 22 connected from the first direction via and provided to the load receiving portion 1, and the deformation amount detection portion 6b detects the first member based on the fluctuating load ΔF 21 and the second member 22, the voltage of which changes according to the relative displacement.

According to the above configuration, the relative displacement caused by the fluctuating load ΔF between the first member 21 and the second member 22 can be detected as the voltage change of the load cell Lc. This makes it possible to more precisely detect and measure the magnitude of the fluctuating load ΔF and its change.

(5) In the load detection device 200 according to the fifth aspect, the support portion 2c further includes a third member 23 supported so as to be displaceable in the first direction with respect to the first member 21, and the The deformation amount detection unit 6c is provided between the second member 22 and the third member 23, and detects relative displacement generated between the second member 22 and the third member 23 based on the fluctuating load ΔF. It further has another load cell Lc whose voltage changes according to .

According to the above configuration, the load cells Lc are provided between the first member 21 and the second member 22 and between the second member 22 and the third member 23, respectively. A compressive force due to the opposite load Fr is normally applied to these load cells Lc. In this state, for example, when the second member 22 provided on the side of the load receiving portion 1 is displaced to the other side in the first direction (that is, when a fluctuating load ΔF directed from one side to the other side occurs), A tensile force is applied to the load cell Lc on one side, and a further compressive force is applied to the load cell Lc on the other side. Here, it is generally known that a load cell can sufficiently withstand compressive force, but is weak against tensile force. This tendency is particularly noticeable in the piezoelectric load cell Lc. However, in the above configuration, the compressive force due to the opposite load Fr is also applied in advance to the one-side load cell Lc to which the tensile force is applied. Therefore, when a tensile force due to displacement as described above is applied, the compressive force and the tensile force cancel each other out. As a result, the one-side load cell Lc is not deformed from the initial state due to the tension, or is only slightly deformed. As a result, detection/measurement can be performed with a margin to the durability limit of the load cell Lc. In other words, the durability limit required for the load cell Lc can be kept low. As a result, the manufacturing cost and maintenance cost of the device can be reduced.

(6) In the load detection device 200 according to the sixth aspect, the opposite load generating portion 5c is provided between the first member 21 and the third member 23, It has a feed screw B for changing the relative position in the first direction with respect to the member 21 .

According to the above configuration, by changing the screwing amount of the feed screw B, it is possible to easily and precisely adjust the magnitude of the counterload Fr. In addition, since the opposite load generating portion 5c can be configured only by providing the feed screw B, the configuration of the device can be simplified and the cost can be reduced accordingly.

(7) In the load detection device 300 according to the seventh aspect, the opposite load generating portion 5d is provided between the first member 21 and the third member 23, and the first It has a solenoid 53b that changes the position relative to the member 21 in the first direction.

According to the above configuration, it is possible to easily and precisely adjust the magnitude of the opposite load Fr by changing the forward/backward movement (length) of the solenoid 53b. In addition, since the opposite load generating section 5d can be configured only by providing the solenoid 53b, it is possible to simplify the configuration of the device and reduce costs based thereon.

100, 200, 300 Load detector 1 Rotating shaft (loaded part)
11 Shaft main body 11F Flange portion 12 Peripheral member 2, 2b, 2c Support portion 21 First member 22 Second member 23 Third member 3 Casing 4 Fixed member 5, 5b, 5c, 5d Opposite load generating portion 51 Iron core 52C Coil portion 52H holder parts 6, 6b deformation amount detection part A1 axis line Favg average load Fr opposite load ΔF fluctuating load G strain gauge Lc load cell Lc1 first load cell Lc2 second load cell Sg reference surface

Claims (7)

A state in which a rotating shaft as a loaded portion to which a load including an average load directed from one side to the other side in the first direction and a fluctuating load superimposed on the average load is applied is displaceable in the first direction. a supporting portion that supports against the reference surface at
an opposite load generating part that applies an opposite load to the load receiving part from the other side to the one side in the first direction and that can be changed based on the magnitude of the average load;
a deformation amount detection unit that detects a deformation amount due to the fluctuating load occurring in the support part;
with
The rotating shaft includes a cylindrical shaft body centered on an axis, a cylindrical outer peripheral member through which the shaft body is inserted, and an end portion on one side in the first direction that protrudes radially outward from the shaft body. and a flange portion that abuts on the outer peripheral member,
The counter load generating section applies a force toward one side in the first direction to the outer peripheral member, thereby applying the counter load to the rotating shaft via the flange section. The opposite load generating section is
an iron core provided in the load-bearing portion;
a coil portion that is provided on the reference plane and faces the iron core to apply an electromagnetic force as the opposite load to the load receiving portion;
The load detection device according to claim 1, comprising: The opposite load generating section is
2. The load detecting device according to claim 1, wherein the solenoid is provided between the reference surface and the load-receiving portion and applies the opposite load to the load-receiving portion. The support part is
a first member provided on the reference surface side;
a second member connected to the first member from the first direction via the deformation amount detection section and provided at the load receiving section;
has
The deformation amount detection unit is
4. The load detecting device according to any one of claims 1 to 3, wherein the load cell is a load cell in which a voltage changes due to relative displacement occurring between the first member and the second member based on the fluctuating load. The support part further has a third member supported displaceably in the first direction with respect to the first member,
The deformation amount detection unit is provided between the second member and the third member, and the voltage changes according to the relative displacement generated between the second member and the third member based on the fluctuating load. 5. The load detection device according to claim 4, further comprising another load cell. 6. The opposite load generating portion has a feed screw provided between the first member and the third member for changing the position of the third member relative to the first member in the first direction. The load detection device according to . 6. According to claim 5, wherein the opposite load generating section has a solenoid provided between the first member and the third member and changing the relative position of the third member in the first direction with respect to the first member. A load detection device as described.

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