JP7600940B2 - Electric actuator, thrust force deriving method for electric actuator, and program - Google Patents

Description

The present invention relates to an electric actuator, a method for deriving thrust force for an electric actuator, and a program.

Electric actuators that convert the rotational force of a motor into linear thrust to operate the actuator have become widespread in recent years.

In an electric actuator, the control amount is determined based on the input, but technology has been disclosed that adjusts the control amount even for the same input, taking into account the influence of the operating environment, etc. For example, Patent Document 1 describes switching the control threshold value in electric brake control according to the input pedal force. Also, Patent Document 2 describes switching the control threshold value in an electric actuator according to the temperature.

JP 2011-11703 A JP 2013-154843 A

On the other hand, the electric actuator as described above may have a waterproof or dustproof structure in consideration of the environment in which it is used. For example, electric actuators for control used in railways are used outdoors, so it is necessary to prevent rainwater and dust from entering the inside of the electric actuator. In the case where the housing member of the electric actuator and the output shaft part are configured to perform piston movement via a connecting member, assuming use in such an environment, a waterproof structure can be used to prevent water from entering around the connecting member. In this configuration, a sealed space is formed around the connecting member. The volume of the sealed space changes with the operation of the electric actuator. This causes the pressure in the sealed space to change, which affects the operation of the electric actuator. In other words, if the above-mentioned waterproof or dustproof structure is used, it becomes difficult to exchange air between the inside and outside, so the air inside is compressed by the operation of the electric actuator, which can become a load that inhibits operation. As a result, even if the control amount is the same, the output by the electric actuator will be different. In this way, it is important to assume a case where the same control amount results in different outputs and understand the actual output of the electric actuator in order to operate the electric actuator with precision.

In consideration of the above problems, the present invention aims to enable an electric actuator to output power while suppressing the effects of load due to internal pressure, taking into account changes in internal pressure that accompany the operation of the electric actuator.

In order to solve the above problems, the present invention has the following configuration.
Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor configured by the output shaft and the housing and configured to detect a pressure in a sealed space in which the connecting mechanism is disposed;
A control unit for controlling the operation of the motor;
an output unit that outputs a thrust force from the output shaft based on the pressure detected by the pressure sensor and a control amount of the motor by the control unit.

Another aspect of the present invention has the following configuration.
Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor configured by the output shaft and the housing and configured to detect a temperature of a sealed space in which the connecting mechanism is disposed;
A control unit for controlling the operation of the motor;
an output unit that derives a thrust force from the output shaft based on a temperature detected by the temperature sensor and a control amount of the motor by the control unit.

Another aspect of the present invention has the following configuration.
Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor for detecting a pressure in a sealed space in which the connecting mechanism is disposed, the pressure sensor comprising:
A thrust deriving method for an electric actuator, comprising the steps of: deriving thrust by the output shaft based on the pressure detected by the pressure sensor and a control amount of the motor.

Another aspect of the present invention has the following configuration.
Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor for detecting a temperature of a sealed space in which the connecting mechanism is disposed, the temperature sensor comprising:
A method for deriving thrust force of an electric actuator, comprising the steps of: deriving thrust force by the output shaft based on a temperature detected by the temperature sensor and a control amount of the motor.

Another aspect of the present invention has the following configuration.
Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor for detecting a pressure in a sealed space including the output shaft and the housing, the pressure sensor detecting a pressure in the sealed space in which the connecting mechanism is disposed,
A program for deriving thrust from the output shaft based on the pressure detected by the pressure sensor and the control amount of the motor.

Another aspect of the present invention has the following configuration.
Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor for detecting a temperature of a sealed space in which the connecting mechanism is disposed, the temperature sensor being configured to detect a temperature of the sealed space in which the connecting mechanism is disposed,
A program for deriving thrust force from the output shaft based on the temperature detected by the temperature sensor and the control amount of the motor.

The present invention makes it possible to output an electric actuator that suppresses the effect of load caused by internal pressure by taking into account changes in internal pressure that occur as the electric actuator operates.

FIG. 1 is a schematic diagram showing an example of an apparatus configuration according to a first embodiment. FIG. 4 is a diagram for explaining pressure inside the electric actuator according to the embodiment of the present invention. FIG. 4 is a diagram for explaining pressure inside the electric actuator according to the embodiment of the present invention. 1 is a diagram for explaining movement inside an electric actuator according to an embodiment of the present invention. FIG. FIG. 4 is a graph illustrating the relationship between the volume, the internal pressure, and the stroke distance of a sealed space according to an embodiment of the present invention. FIG. 4 is a graph illustrating the effect of a change in stroke distance on a thrust force of the electric actuator according to the embodiment of the present invention. FIG. 4 is a graph illustrating the effect of a change in stroke distance on a thrust force of the electric actuator according to the embodiment of the present invention. 4 is a flowchart of a control process for the electric actuator according to the first embodiment. FIG. 11 is a schematic diagram showing an example of an apparatus configuration according to a second embodiment. 10 is a flowchart of a control process for an electric actuator according to a second embodiment. FIG. 13 is a schematic diagram showing an example of an apparatus configuration according to a third embodiment.

The following describes the embodiment of the present invention with reference to the drawings. Note that the embodiment described below is one embodiment for explaining the present invention, and is not intended to be interpreted as limiting the present invention, and not all of the configurations described in each embodiment are necessarily essential configurations for solving the problems of the present invention. In addition, in each drawing, the same components are given the same reference numbers to indicate their correspondence.

First Embodiment
A first embodiment of the present invention will be described below.

[Device configuration]
Fig. 1 is a schematic diagram showing an example of the overall configuration of the device according to this embodiment. In Fig. 1, an electric actuator 10 according to this embodiment is configured to include a drive unit 100 and a control device 200. The control device 200 is also communicably connected to a host device 20 that is positioned above the electric actuator 10. The electric actuator 10 operates based on instructions from the host device 20.

The drive unit 100 outputs a predetermined thrust based on the control of the control device 200. The motor 102 rotates based on the current input from the control device 200. The motor 102 is equipped with a rotational position sensor 103. The rotational position sensor 103 detects the rotational position associated with the rotational operation of the motor 102 using an encoder (not shown) or the like, and transmits it to the control device 200. A reducer 104 for transmitting the rotational force of the motor 102 is provided inside the housing 101. The reducer 104 is connected to the linear motion mechanism 108, and the rotational force from the reducer 104 is transmitted to the linear motion mechanism 108. The output shaft 105 and the linear motion mechanism 108 are connected via a connecting mechanism 107. When the linear motion mechanism 108 rotates, the connecting mechanism 107 moves along the axial direction of the linear motion mechanism 108 (the direction indicated by the arrow A in FIG. 1), and the output shaft 105 also moves (piston operation) accordingly, and the thrust by the electric actuator 10 is output. The direction of movement of the output shaft 105 and the connecting mechanism 107 is determined according to the direction of rotation of the motor 102.

The linear motion mechanism 108 is configured with a screw shaft having a helical screw groove on its outer circumferential surface. The connecting mechanism 107 is arranged by being fitted into the screw groove. At this time, the rolling elements (not shown) of the connecting mechanism 107 are configured to be able to roll freely in the screw groove of the linear motion mechanism 108, and the connecting mechanism 107 moves in a predetermined direction as the linear motion mechanism 108 rotates. A lubricant (lubricating oil, grease, etc.) may be supplied around the rolling elements and the screw groove by any lubrication method to reduce friction therebetween.

The housing 101 and the output shaft 105 form a sealed space 109 including the connecting mechanism 107 and the linear motion mechanism 108. In other words, in this embodiment, it is assumed that the sealed space 109 formed by the housing 101 and the output shaft 105 is configured to prevent the inflow of liquids and the like into the sealed space 109. By providing a sealed space, dustproofing and waterproofing can be achieved, but it becomes difficult to exchange air with the outside. A pressure sensor 106 for detecting the pressure within the sealed space 109 is provided in the sealed space 109. In FIG. 1, the sealed spaces 109 are shown on both sides of the connecting mechanism 107, but these are connected to form a single sealed space 109. Note that, here, the pressure sensor 106 is described as detecting air pressure, but a sensor that detects liquid pressure (e.g., oil pressure) may be used depending on the configuration of the electric actuator 10. The pressure sensor 106 transmits information on the detected pressure to the control device 200.

The control device 200 is connected to the higher-level device 20 so as to be able to communicate with it. The control device 200 may be composed of, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or a dedicated circuit. Although not shown in FIG. 1, the control device 200 is composed of volatile and non-volatile storage media such as a HDD (Hard Disk Drive), a ROM (Read Only Memory), or a RAM (Random Access Memory). Note that, although FIG. 1 shows one higher-level device 20 and one electric actuator 10, this is not limiting, and one higher-level device 20 may be configured to control and manage multiple electric actuators 10.

The motor braking unit 201 outputs a signal to the inverter 202 to control the motor 102 according to instructions from the higher-level device 20. Based on the signal from the motor braking unit 201, the inverter 202 converts the power supplied from the power source 203 into a current for operating the motor 102 and supplies it to the motor 102. The motor 102 rotates based on this supplied current. Note that although the inverter 202 and the power source 203 are shown as components provided in the control device 200, they may be provided outside the control device 200.

The thrust derivation unit 204 derives the thrust output from the electric actuator 10 as a result of operating the motor 102. The thrust derivation method according to this embodiment will be described later. The motor angle derivation unit 205 derives the rotation angle of the motor 102 based on position information acquired from the rotation position sensor 103 provided in the motor 102. Here, the configuration may be such that the rotation speed of the motor 102 is also derived. The current sensor 206 detects the current supplied to the motor 102 by the inverter 202. The status monitoring unit 207 collects various information from various sensors and parts, and monitors the status of the drive unit 100 and the control device 200. In addition, the status monitoring unit 207 transmits the monitoring results (presence or absence of abnormality, operating status, etc.) to the status output unit 208. The status output unit 208 outputs the information acquired from the status monitoring unit 207 to the upper device 20.

The higher-level device 20 may be realized, for example, by an information processing device including a control unit, a storage unit, and an input/output unit (not shown). The control unit may be composed of a CPU, an MPU, a DSP, an ECU (Electronic Control Unit), or a dedicated circuit. The storage unit is composed of volatile and non-volatile storage media such as a HDD, a ROM, or a RAM, and is capable of inputting and outputting various information in response to instructions from the control unit. The input/output unit may be composed of various interfaces, and is at least connected to the control device 200 so as to be able to communicate with it.

[Pressure changes in a sealed space]
2 and 3 are diagrams for explaining the change in pressure in the sealed space 109 configured in the electric actuator 10 according to the present embodiment and its influence. FIG. 2(a) shows a case where the output shaft 105 in the driving unit 100 operates in the extension direction from the most contracted state. At this time, it is assumed that the control device 200 receives an instruction from the upper device 20 with the thrust by the driving unit 100 as a thrust P1a in the extension direction. In the state of FIG. 2(a), the sealed space 109 of the driving unit 100 is compressed, and as a result, the internal pressure of the sealed space 109 increases. Therefore, the force P2a in the extension direction due to the internal pressure in the sealed space 109 is combined with the thrust P1a of the driving unit 100 controlled based on the instruction. As a result, the thrust output by the driving unit 100 becomes P3a (=P1a+P2a).

2(b) shows a case where the drive unit 100 operates in the extension direction from a state where the output shaft 105 is extended to a certain extent. At this time, the control device 200 accepts an instruction from the upper device 20, regarding the thrust by the drive unit 100 as thrust P1b in the extension direction. In the state of FIG. 2(b), the volume of the sealed space 109 of the drive unit 100 is expanded compared to the state of FIG. 2(a), and as a result, the internal pressure of the sealed space 109 is reduced. Therefore, the force P2b due to the internal pressure in the sealed space 109 is combined with the thrust P1b of the drive unit 100, which is controlled based on the instruction. Here, as an example, the force P2b due to the internal pressure is shown to be in the opposite (-) direction to the thrust of the drive unit 100 (i.e., the contraction direction). As a result, the thrust output by the drive unit 100 is P3b (=P1b-P2b).

2(b), the volume of the sealed space 109 is larger than that of the state of FIG. 2(a), and the internal pressure of the sealed space 109 fluctuates accordingly, changing the degree of influence on the thrust force output by the drive unit 100. As shown by force P2b in FIG. 2(b), whether or not a force is generated in the direction opposite to the direction in which the output shaft 105 extends varies depending on the volume of the sealed space 109, the configuration of the electric actuator 10, etc.

Figure 3(a) shows a case where the output shaft 105 of the drive unit 100 moves in the contraction direction from a contracted state to a certain extent. At this time, it is assumed that the control device 200 receives an instruction from the upper device 20 regarding the thrust by the drive unit 100 as a thrust P1c in the contraction direction. In the state of Figure 3(a), the sealed space 109 of the drive unit 100 is compressed, and as a result, the internal pressure of the sealed space 109 increases. Therefore, the force P2c due to the internal pressure in the sealed space 109 is combined with the thrust P1c of the drive unit 100 controlled based on the instruction. Here, as an example, the force P2c due to the internal pressure is shown to be in the opposite (-) direction to the thrust of the drive unit 100 (i.e., the extension direction). As a result, the thrust output by the drive unit 100 becomes P3c (= P1c - P2c).

Figure 3(b) shows a case where the output shaft 105 of the drive unit 100 contracts from a certain extended state. At this time, the control device 200 accepts an instruction from the upper device 20 to set the thrust from the drive unit 100 as a thrust P1d in the contraction direction. In the state of Figure 3(b), the volume of the sealed space 109 of the drive unit 100 is expanded compared to the state of Figure 3(a), and as a result, the internal pressure of the sealed space 109 decreases. Therefore, the force P2d in the contraction direction due to the internal pressure in the sealed space 109 is combined with the thrust P1d of the drive unit 100, which is controlled based on the instruction. As a result, the thrust output by the drive unit 100 becomes P3d (= P1d + P2d).

In other words, in the state of FIG. 3(b), the volume of the sealed space 109 is larger than in the state of FIG. 3(a), and the internal pressure of the sealed space 109 fluctuates accordingly, changing the degree of influence on the thrust force output by the drive unit 100. As shown by force P2d in FIG. 3(b), whether or not a force is generated in the same direction as the contraction direction of the output shaft 105 varies depending on the volume of the sealed space 109, the configuration of the electric actuator 10, etc.

Figure 4 is a diagram for explaining the operation around the output shaft 105 of the drive unit 100. The connecting mechanism 107 is configured to be able to move within the sealed space 109 along the linear motion mechanism 108 within the movable range shown in Figure 4. When the connecting mechanism 107 moves in the contraction direction shown in Figure 4, the volume of the sealed space 109 decreases. On the other hand, when the connecting mechanism 107 moves in the extension direction, the volume of the sealed space 109 increases. Here, the pressure sensor 106 is omitted. The movable range can vary depending on the arrangement of the pressure sensor 106, etc.

In FIG. 4, the center of the movable range in the moving direction of the connecting mechanism 107 is set as the reference position _P0 . In addition, the center of the connecting mechanism 107 in the moving direction of the connecting mechanism 107 is set as the central position _Pc . The distance between the reference position _P0 and the central position _Pc is set as the stroke distance (= _P0 - _Pc ). In this example, when the central position _Pc is located on the contraction direction side from the reference position _P0 , the stroke distance indicates a negative value, and when the central position _Pc is located on the expansion direction side from the reference position _P0 , the stroke distance indicates a positive value. Note that the method of calculating the stroke distance is not limited to this. For example, the reference position _P0 may be set at the end of the movable range, or the end of the connecting mechanism 107 may be used instead of the central position Pc.

5 is a diagram for explaining the relationship between the volume, stroke distance, and internal pressure of the sealed space 109 of the drive unit 100 according to this embodiment. In FIG. 5(a), the horizontal axis indicates the stroke distance, and the vertical axis indicates the volume of the sealed space 109. At a stroke distance L _min where the output shaft 105 is in the most contracted state, the volume of the sealed space 109 is the minimum volume V _min . At a stroke distance L _max where the output shaft 105 is in the most extended state, the volume of the sealed space 109 is the maximum volume V _max . As shown in FIG. 5, the volume of the sealed space 109 increases as the stroke distance increases. When the stroke distance is 0, that is, when the center position P _c shown in FIG. 4 coincides with the reference position P ₀ , the volume is defined as V ₀ .

In Fig. 5(b), the horizontal axis represents the volume of the sealed space 109, and the vertical axis represents the internal pressure of the sealed space 109. In Fig. 5(b), when the volume of the sealed space 109 is the maximum volume _Vmax , the internal pressure of the sealed space 109 is the minimum internal pressure _Pmin . Also, when the volume of the sealed space 109 is the minimum volume _Vmin , the internal pressure of the sealed space 109 is the maximum internal pressure _Pmax . The relationship shown in Fig. 5(b) can be derived from the configuration of the electric actuator 10 and Boyle's law, etc.

6 and 7 are diagrams for explaining the influence of the internal pressure of the sealed space 109 of the drive unit 100 on the thrust and the relationship with the stroke distance. In FIG. 6, the vertical axis indicates the change (force) of the thrust due to the internal pressure in the extension direction, and the horizontal axis indicates the stroke distance. That is, FIG. 6 shows the relationship between the thrust and the stroke distance during the extension operation described with reference to FIG. 2. At the stroke distance L _min , the change amount is the maximum change amount ΔF _max . Also, at the stroke distance L _max , the change amount is the minimum change amount ΔF _min . In this example, when the stroke distance is 0, the change amount is 0, and there is no influence on the thrust that the electric actuator 10 wants to output. When the change amount indicates a negative value, as shown in FIG. 2(b), a force in the opposite direction to the direction of the thrust that the electric actuator 10 wants to output acts. On the other hand, when the change amount indicates a positive value, as shown in FIG. 2(a), a force in the same direction as the direction of the thrust that the electric actuator 10 wants to output acts.

In Fig. 7, the vertical axis indicates the change (force) in thrust due to the internal pressure in the contraction direction, and the horizontal axis indicates the stroke distance. That is, Fig. 7 shows the relationship between thrust and stroke distance during the contraction operation described with reference to Fig. 3. At stroke distance _Lmin , the change is the minimum change amount _ΔFmin . At stroke distance _Lmax , the change is the maximum change amount _ΔFmax . In this example, when the stroke distance is 0, the change amount is 0, and there is no effect on the thrust that the electric actuator 10 wants to output. When the change amount indicates a negative value, as shown in Fig. 3(a), a force acts in the opposite direction to the direction of the thrust that the electric actuator 10 wants to output. On the other hand, when the change amount indicates a positive value, as shown in Fig. 3(b), a force acts in the same direction as the direction of the thrust that the electric actuator 10 wants to output.

Note that the relationships between the parameters shown in Figures 5 to 7 are merely examples and are not limiting. For example, the slopes of the straight lines and the curvatures of the curves shown in Figures 5 to 7 may vary depending on the configuration of the electric actuator 10 and the ambient temperature.

[Processing flow]
8 is a flowchart of the control process of the electric actuator 10 according to this embodiment. This process is executed by the control device 200, for example, by reading out from a storage device (not shown) and executing a program for implementing each part shown in FIG.

In S801, the control device 200 receives an operation instruction for the electric actuator 10 from the higher-level device 20. The operation instruction here may be, for example, a thrust value to be output by the electric actuator 10, or the amount of movement of the output shaft 105.

In S802, the control device 200 outputs a current for operating the motor 102 based on the operation instruction received in S801. The current here is supplied to the motor 102 after being converted by the inverter 202 from the power source 203 based on a signal instructed by the motor braking unit 201.

At S803, the control device 200 acquires the value of the current supplied to the motor 102 using the current sensor 206.

In S804, the control device 200 derives the torque of the motor 102 from the current value acquired in S803. The method of derivation here is not particularly limited, but may be performed by, for example, referring to a table (not shown) that associates current with torque, or by using a predefined calculation formula.

At S805, the control device 200 acquires the internal pressure of the sealed space 109 using the pressure sensor 106.

In S806, the control device 200 causes the thrust derivation unit 204 to derive the thrust of the output shaft 105 based on the torque derived in S804 and the internal pressure acquired in S805. First, the thrust derivation unit 204 derives the thrust from the torque derived in S804. Here, the thrust may be derived by referring to a table (not shown) that associates torque with thrust, or may be derived using a predefined calculation formula. Next, the thrust derivation unit 204 derives the change amount ΔF for the thrust from the internal pressure acquired in S805 based on the relationship as described in Figures 6 and 7. Then, the thrust derivation unit 204 derives the thrust by the output shaft 105 by combining the thrust based on the torque and the change amount. Then, this processing flow ends.

The control device 200 may be configured to adjust the rotational operation of the motor 102 based on the thrust derived in S806 of FIG. 8. The control device 200 may also be configured to output information on the derived thrust to the higher-level device 20 via the status output unit 208.

For example, if a difference occurs between the thrust based on the operation command and the thrust output due to the influence of a change in internal pressure, the torque of the motor 102 is adjusted to offset the difference. This feedback function controls the thrust based on the operation command to be equal to the thrust actually output, regardless of the change in internal pressure in the sealed space. In other words, even if a load that inhibits the operation of the electric actuator 10 occurs due to the provision of a sealed space, the influence of this load can be reduced, making it possible to output the thrust based on the operation command.

As described above, this embodiment makes it possible to output an electric actuator that suppresses the effect of load due to internal pressure by taking into account internal pressure changes that occur with the operation of the electric actuator.

Second Embodiment
A second embodiment of the present invention will be described below. In the first embodiment, the pressure sensor 106 was used to detect the state of the sealed space 109 of the electric actuator 10. In this embodiment, a configuration in which a temperature sensor 901 is used instead of the pressure sensor 106 will be described. Note that descriptions of points that overlap with the first embodiment will be omitted, and the description will focus on the differences.

[Device configuration]
Fig. 9 is a schematic diagram showing an example of the overall configuration of the device according to this embodiment. The difference from the configuration shown in Fig. 1 is that a temperature sensor 901 is provided in place of the pressure sensor 106 in the sealed space 109 of the electric actuator 10. In addition, the control device 200 further includes a pressure lead-out unit 902.

The temperature sensor 901 detects the temperature inside the sealed space 109 and transmits it to the control device 200. The pressure derivation unit 902 derives the pressure based on the temperature of the sealed space 109 and the volume of the sealed space. An example of the derivation method will be described later.

[Processing flow]
10 is a flowchart of the control process of the electric actuator 10 according to this embodiment. This process is executed by the control device 200, for example, by reading out from a storage device (not shown) and executing a program for implementing each part shown in FIG.

In S1001, the control device 200 receives an operation instruction for the electric actuator 10 from the higher-level device 20. The operation instruction here may be, for example, a thrust value to be output by the electric actuator 10, or the amount of movement of the output shaft 105.

In S1002, the control device 200 outputs a current for operating the motor 102 based on the operation instruction received in S1001. The current here is supplied to the motor 102 after being converted by the inverter 202 from the power source 203 based on a signal instructed by the motor braking unit 201.

At S1003, the control device 200 acquires the value of the current supplied to the motor 102 using the current sensor 206.

In S1004, the control device 200 derives the torque of the motor 102 from the current value acquired in S1003. The method of derivation here is not particularly limited, but may be performed by, for example, referring to a table (not shown) that associates current with torque, or by using a predefined calculation formula.

At S1005, the control device 200 acquires the temperature inside the sealed space 109 using the temperature sensor 901.

At S1006, the control device 200 acquires position information associated with the rotational operation of the motor 102 using the rotational position sensor 103.

In S1007, the control device 200 derives the volume of the sealed space 109 at that time based on the position information acquired in S1006. As described above, the rotation angle and rotation speed of the motor 102 can be derived based on the position information acquired from the rotation position sensor 103, and this can be used to derive the extension/contraction state of the output shaft 105 (i.e., the stroke distance shown in FIG. 4). Then, as shown in FIG. 5(a), the volume is determined from the relationship between the stroke distance and the volume of the sealed space 109. Information indicating the relationship shown in FIG. 5 is specified in advance and stored in a memory unit (not shown).

In S1008, the control device 200 derives the pressure inside the sealed space 109 based on the volume of the sealed space 109 derived in S1007 and the temperature acquired in S1005. The derivation method here is not particularly limited, but may be, for example, derived using a table (not shown) that specifies the correspondence between temperature and volume and pressure, or may be derived using a calculation formula that is specified in advance based on the Boyle-Charles law or the like.

In S1009, the control device 200 causes the thrust derivation unit 204 to derive the thrust of the output shaft 105 based on the torque derived in S1004 and the internal pressure derived in S1008. First, the thrust derivation unit 204 derives the thrust from the torque derived in S1004. Here, the thrust may be derived by referring to a table (not shown) that associates torque with thrust, or may be derived using a predefined calculation formula. Next, the thrust derivation unit 204 derives the amount of change in thrust from the internal pressure derived in S1008 based on the relationship described in Figures 6 and 7. Then, the thrust derivation unit 204 derives the thrust by the output shaft 105 by combining the thrust based on the torque and the amount of change. Then, this processing flow ends.

After that, if a difference occurs between the thrust based on the operation command and the thrust output due to the influence of the change in internal pressure, the torque of the motor 102 is adjusted to offset the difference. This feedback function controls the thrust based on the operation command to be equal to the thrust actually output, regardless of the change in the internal pressure of the sealed space. In other words, even if a load that inhibits the operation of the electric actuator 10 occurs due to the provision of the sealed space, it is possible to reduce the effect and output the thrust based on the operation command.

As described above, this embodiment makes it possible to output an electric actuator that suppresses the effect of load due to internal pressure by taking into account internal pressure changes that occur with the operation of the electric actuator, even when a temperature sensor is used instead of a pressure sensor.

Third Embodiment
A third embodiment of the present invention will be described below. In the second embodiment, the temperature sensor 901 is provided inside the sealed space 109. In this embodiment, a mode in which the temperature sensor 901 is provided outside the sealed space 109 will be described. Note that a description of parts that overlap with the second embodiment will be omitted, and the description will focus on the differences.

[Device configuration]
Fig. 11 is a schematic diagram showing an example of the overall configuration of the device according to this embodiment. The difference from the configuration shown in Fig. 9 is that a temperature sensor 901 is provided outside the sealed space 109. As the temperature sensor 901 is provided outside the sealed space 109, the pressure lead-out unit 902 according to this embodiment takes into account the thermal conductivity of the housing 101 and the like when leading out the pressure in the sealed space 109. The processing flow is the same as that shown in Fig. 10 in the second embodiment.

Note that, although FIG. 11 shows a configuration in which the temperature sensor 901 is installed on the outer periphery of the housing 101, this is not limiting. For example, the temperature sensor 901 may be installed on the outer periphery of the output shaft 105. Alternatively, the temperature sensor 901 may be configured as an infrared sensor or thermography, and may be installed away from the housing 101.

This embodiment uses a temperature sensor 901, as in the second embodiment, to take into account the internal pressure changes that accompany the operation of the electric actuator, and enables the output of the electric actuator to suppress the effects of load due to internal pressure. In addition, in this embodiment, there is no need to provide space around the output shaft 105 to install the temperature sensor 901, which improves design freedom.

<Other embodiments>
In addition, the present invention can also be realized by supplying a program or application for realizing the functions of one or more of the above-mentioned embodiments to a system or device via a network or a storage medium, etc., and having one or more processors in a computer of the system or device read and execute the program.

It may also be realized by a circuit that realizes one or more functions (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)).

As such, the present invention is not limited to the above-described embodiment, and the invention also contemplates the mutual combination of the various components of the embodiment, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known technology, and these are included in the scope of the protection sought.

As described above, the present specification discloses the following:
(1) An electric actuator,
Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor configured by the output shaft and the housing and configured to detect a pressure in a sealed space in which the connecting mechanism is disposed;
A control unit for controlling the operation of the motor;
The actuator further includes a derivation unit that derives a thrust force from the output shaft based on the pressure detected by the pressure sensor and a control amount of the motor by the control unit.
According to this configuration, it is possible to output the electric actuator while suppressing the influence of the load due to the internal pressure, taking into account the internal pressure change caused by the operation of the electric actuator. In particular, since it is possible to derive the actual thrust force that is output in response to the change in the internal pressure, it is possible to further control the electric actuator based on this derived value.

(2) The electric actuator according to (1), wherein the control unit adjusts a control amount of the motor so that a thrust force generated by the output shaft based on an operation command is equal to a thrust force derived by the derived portion.
With this configuration, even if a load that impedes the operation of the electric actuator is generated due to the provision of a sealed space, the effect of this load can be reduced and control can be made to output a thrust based on an operation command.

(3) The electric actuator according to (1) or (2), wherein the pressure in the sealed space varies in response to linear movement of the output shaft.
According to this configuration, it is possible to derive the actual output of the electric actuator by taking into account the pressure change in the sealed space that accompanies the linear movement of the output shaft of the electric actuator.

(4) a housing;
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor configured by the output shaft and the housing and configured to detect a temperature of a sealed space in which the connecting mechanism is disposed;
A control unit for controlling the operation of the motor;
an output unit that derives a thrust force from the output shaft based on a temperature detected by the temperature sensor and a control amount of the motor by the control unit.
According to this configuration, it is possible to output the electric actuator while suppressing the influence of the load due to the internal pressure, taking into account the internal temperature change and the pressure change due to the volume change caused by the operation of the electric actuator. In particular, since it is possible to derive the actual thrust force that is output in response to the change in the internal pressure, it is possible to further control the electric actuator based on this derived value.

(5) The control unit
A pressure in the sealed space is derived based on a temperature detected by the temperature sensor and a volume of the sealed space derived from a control amount of the motor;
The electric actuator according to (4) is characterized in that a thrust force from the output shaft is derived based on the pressure and a control amount of the motor by the control unit.
According to this configuration, it is possible to derive the actual output of the electric actuator by taking into account the internal temperature change accompanying the operation of the electric actuator and the pressure change accompanying the volume change.

(6) The electric actuator according to (5), wherein the control unit adjusts a control amount of the motor so that a thrust force generated by the output shaft based on an operation command is equal to a thrust force derived by the derived portion.
With this configuration, even if a load that impedes the operation of the electric actuator is generated due to the provision of a sealed space, the effect of this load can be reduced and control can be made to output a thrust based on an operation command.

(7) The electric actuator according to any one of (4) to (6), wherein the temperature sensor is installed within the sealed space.
According to this configuration, it is possible to directly measure the temperature inside the sealed space and to accurately derive the actual thrust of the electric actuator based on the temperature.

(8) The electric actuator according to any one of (4) to (6), wherein the temperature sensor is installed in contact with an outer periphery of the housing or the output shaft that defines the sealed space.
According to this configuration, it is possible to improve the degree of freedom in designing the area around the output shaft while deriving the actual thrust force of the electric actuator.

(9) The electric actuator according to any one of (4) to (6), wherein the temperature sensor is configured to detect the temperature without contacting the housing or the output shaft that constitutes the sealed space.
According to this configuration, it is possible to improve the degree of freedom in designing the area around the output shaft while deriving the actual thrust force of the electric actuator.

(10) a housing;
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
A method for deriving thrust of an electric actuator including the output shaft and the housing, and a pressure sensor for detecting a pressure in a sealed space in which the connecting mechanism is disposed, comprising:
A thrust force by the output shaft is derived based on the pressure detected by the pressure sensor and a control amount of the motor.
According to this configuration, it is possible to output the electric actuator while suppressing the influence of the load due to the internal pressure, taking into account the internal pressure change caused by the operation of the electric actuator. In particular, since it is possible to derive the actual thrust force that is output in response to the change in the internal pressure, it is possible to further control the electric actuator based on this derived value.

(11) a housing;
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor for detecting a temperature of a sealed space in which the connecting mechanism is disposed, the temperature sensor comprising:
A method for deriving thrust force of an electric actuator, comprising the steps of: deriving thrust force by the output shaft based on a temperature detected by the temperature sensor and a control amount of the motor.
According to this configuration, it is possible to output the electric actuator while suppressing the influence of the load due to the internal pressure, taking into account the internal temperature change and the pressure change due to the volume change caused by the operation of the electric actuator. In particular, since it is possible to derive the actual thrust force that is output in response to the change in the internal pressure, it is possible to further control the electric actuator based on this derived value.

(12) a housing;
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor for detecting a pressure in a sealed space including the output shaft and the housing, the pressure sensor detecting a pressure in the sealed space in which the connecting mechanism is disposed,
A program for deriving thrust from the output shaft based on the pressure detected by the pressure sensor and the control amount of the motor.
According to this configuration, it is possible to output the electric actuator while suppressing the influence of the load due to the internal pressure, taking into account the internal pressure change caused by the operation of the electric actuator. In particular, since it is possible to derive the actual thrust force output affected by the internal pressure change, it is possible to further control the electric actuator based on this derived value.

(13) a housing;
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor for detecting a temperature of a sealed space in which the connecting mechanism is disposed, the temperature sensor being configured to detect a temperature of the sealed space in which the connecting mechanism is disposed,
A program for deriving thrust force from the output shaft based on the temperature detected by the temperature sensor and the control amount of the motor.
According to this configuration, it is possible to output the electric actuator while suppressing the influence of the load due to the internal pressure, taking into account the internal temperature change and the pressure change due to the volume change caused by the operation of the electric actuator. In particular, since it is possible to derive the actual thrust force that is output in response to the change in the internal pressure, it is possible to further control the electric actuator based on this derived value.

10... Electric actuator 20... Upper device 100... Drive unit 101... Housing 102... Motor 103... Rotational position sensor 104... Reducer 105... Output shaft 106... Pressure sensor 107... Linking mechanism 108... Linear motion mechanism 109... Sealed space 200... Control device 201... Motor braking unit 202... Inverter 203... Power supply 204... Thrust derivation unit 205... Motor angle derivation unit 206... Current sensor 207... Status monitoring unit 208... Status output unit 901... Temperature sensor 902... Pressure derivation unit

Claims (13)

Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor configured by the output shaft and the housing and configured to detect a pressure in a sealed space in which the connecting mechanism is disposed;
A control unit for controlling the operation of the motor;
an output unit that outputs a thrust force from the output shaft based on the pressure detected by the pressure sensor and a control amount of the motor by the control unit. The electric actuator according to claim 1, characterized in that the control unit adjusts the control amount of the motor so that the thrust force generated by the output shaft based on the operation command is equal to the thrust force derived by the derived unit. The electric actuator according to claim 1 or 2, characterized in that the pressure in the sealed space varies in response to the linear movement of the output shaft. Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor configured by the output shaft and the housing and configured to detect a temperature of a sealed space in which the connecting mechanism is disposed;
A control unit for controlling the operation of the motor;
an output unit that derives a thrust force from the output shaft based on a temperature detected by the temperature sensor and a control amount of the motor by the control unit. The control unit is
A pressure in the sealed space is derived based on a temperature detected by the temperature sensor and a volume of the sealed space derived from a control amount of the motor;
5. The electric actuator according to claim 4, wherein a thrust force from the output shaft is derived based on the pressure and a control amount of the motor by the control unit. The electric actuator according to claim 4 or 5, characterized in that the control unit adjusts the control amount of the motor so that the thrust force generated by the output shaft based on the operation command is equal to the thrust force derived by the derived unit. The electric actuator according to any one of claims 4 to 6, characterized in that the temperature sensor is installed within the sealed space. The electric actuator according to any one of claims 4 to 6, characterized in that the temperature sensor is installed in contact with the outer periphery of the housing or the output shaft that constitutes the sealed space. The electric actuator according to any one of claims 4 to 6, characterized in that the temperature sensor is configured to detect the temperature without contacting the housing or the output shaft that constitutes the sealed space. Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor for detecting a pressure in a sealed space in which the connecting mechanism is disposed, the pressure sensor comprising:
A thrust deriving method for an electric actuator, comprising the steps of: deriving thrust by the output shaft based on the pressure detected by the pressure sensor and a control amount of the motor. Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor for detecting a temperature of a sealed space in which the connecting mechanism is disposed, the temperature sensor comprising:
A method for deriving thrust force of an electric actuator, comprising the steps of: deriving thrust force by the output shaft based on a temperature detected by the temperature sensor and a control amount of the motor. Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a pressure sensor that detects a pressure in a sealed space in which the connecting mechanism is disposed, the pressure sensor being configured to detect a pressure in a sealed space in which the connecting mechanism is disposed,
A program for deriving thrust from the output shaft based on the pressure detected by the pressure sensor and the control amount of the motor. Housing and
A motor;
A screw shaft to which a rotational force from the motor is input;
A connecting mechanism configured to move linearly along the screw shaft as the screw shaft rotates due to the rotational force;
a hollow output shaft connected to the connecting mechanism and moving linearly together with the connecting mechanism to output a thrust;
a temperature sensor for detecting a temperature of a sealed space in which the connecting mechanism is disposed, the temperature sensor being configured to detect a temperature of the sealed space in which the connecting mechanism is disposed,
A program for deriving thrust force from the output shaft based on the temperature detected by the temperature sensor and the control amount of the motor.

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