JPH09190225A - Driving position detection device for motor driven actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge the present position of a driving rod at the time of restoring power failure even if a motor driven actuator is operated by means of a manual operation at the time of non-conduction such as power failure time. SOLUTION: The rotary movement of a screw shaft when the driving rod advances/recedes is transmitted to the rotary shaft of a driving position detection device through a reduction gear group. A movable body which is screwed onto the rotary shaft and to which a lever body for varying the detection value of a position detection sensor 4 is fitted is moved to an axial direction by adjusting it to the advancing/receding operation of the driving rod and the detection value of the position detection sensor 54 is sequentially changed. The detection value of the position detection sensor 54 when operation switches SW1 and SW2 are turned on and when the driving rod advances and recedes is taken into CPU 63 of a controller 62. The detection value is collated with a limit value which is previously set in CPU 63, and whether the driving rod is to be advanced or receded is judged. Only when it is judged to be advanced/ receded, an electric motor 6 is started and the driving rod is advanced/receded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided, for example, as a drive source in a bed, an electric chair or the like having a drive mechanism for raising and lowering a floor surface to an arbitrary height or raising and lowering a back portion at a constant angle. The present invention also relates to improvement of a drive position detection device for an electric actuator.

[0002]

2. Description of the Related Art In recent years, in electric beds, electric chairs, etc. used in medical institutions, a drive for raising or lowering the floor of the bed or the like to a desired height or raising or lowering the back or the like at a constant angle. Electric actuators are widely used as a source. The electric actuator includes, for example, a drive unit including an electric motor and a speed reducer, a screw shaft drivingly connected to the drive unit, and a drive rod having a nut fixed to the screw shaft and fixed to the screw shaft. By rotating the screw shaft to the right or left by the rotational movement thus performed, the drive rod provided with the nut screwed with the screw shaft is advanced / retracted in the linear direction.

Next, an example of using the electric actuator in an electric bed will be described. For example, when an operation switch for bed operation provided by a patient or the like is turned on, the electric actuator responds to the operation. Then, in response to a command from the drive control means for driving and controlling the electric motor, the electric motor is activated to rotate the screw shaft, and the drive rod screwed to the screw shaft is advanced / retracted in a predetermined direction,
By transmitting the advancing / retreating motions of the drive rod to the floor or back of the bed through a link mechanism, the floor of the bed is raised or lowered, and the back frame or the like is tilted. ing.

In the electric actuator configured as described above, when the advance / retreat limit position of the drive rod is detected, for example, a CPU (central processing unit) provided in the drive control means causes the electric motor to operate. The rotation speed of the electric motor detected by the rotation speed detection sensor such as a hall element or an encoder provided is counted, and the count is C
When the count value (limit value) preset in PU is reached, it is judged that the drive rod has advanced or retracted to the advance limit position or the retract limit position, the motor drive is stopped, and the drive rod advances or retracts the limit. It is configured to prevent driving beyond position. The drive control means causes the CPU to store the count number each time the motor is stopped, and when the power is not supplied such as when a power failure occurs, the CP
The count number stored in U is transferred to and stored in a storage unit (e.g., eeprom) built in the drive control means.

[0005]

However, when the drive position of the drive rod is detected as described above, for example, when the electric actuator is not energized during a power failure or when the device is attached or adjusted to a device, If the screw rod is manually operated to move the drive rod from a predetermined stop position, there is a problem that the advance / retreat limit position of the drive rod cannot be accurately detected at the start of energization.

That is, when the screw shaft is rotated by manual operation when the power is not supplied, the number of rotations is not counted by the CPU (for example, the CPU does not operate during a power failure). When the electric motor of the electric actuator is driven, as described above, only the count number immediately before the occurrence of a power failure or the like is stored in the storage unit of the drive control unit, so that the CPU determines from the count number stored in the storage unit. Since it will start counting, the actual advance / retreat limit position of the drive rod and CP
The advance / reverse limit position determined by the count value of U does not match, and as a result, the electric actuator malfunctions, causing damage to the electric actuator itself or a device equipped with the electric actuator. there were.

In view of the various problems described above, the present invention can reliably detect the advance / retreat limit position of the drive rod after the start of energization, even if the electric actuator is manually operated during non-energization such as power failure. It is an object of the present invention to provide a drive position detection device for an electric actuator that is capable of performing the above.

[0008]

In order to solve the above-mentioned problems, the present invention provides a drive means for an electric actuator, which comprises an electric motor and a speed-reducing means for reducing the output from the electric motor at a predetermined speed reduction ratio. A motion converting means for converting the decelerated rotational motion from the driving means into a linear motion, an output means for advancing / retracting by the linear motion from the motion converting means, and a driving force control means inserted in the middle of the motion converting means. Further, the electric actuator corresponds to a drive position detecting means for detecting the current position of the output means by following the advancing / retracting operation of the output means, and a detection value of the drive position detecting means. The position detection device is composed of a drive control means for driving and controlling the electric motor and an operation means having a plurality of operation switches for operating the electric actuator.

Further, the drive position detecting means is screwed to a rotary shaft for transmitting the rotational motion of the motion converting means by decelerating the rotational motion to a predetermined speed, and a screw portion screwed on the rotary shaft to reduce the speed. It is composed of a moving body that moves along the axial direction of the rotating shaft by rotation, and a position detection sensor (sliding resistor) that changes its detection value by following the linear movement of the moving body.

Further, the drive position detecting means sets the length of the threaded portion of the rotary shaft to a length such that the moving body can be disengaged from the threaded portion at both left and right ends thereof, and Elastic members made of compression springs and the like are attached to the left and right ends, for example, when the moving body is disengaged from the screw portion of the rotary shaft, the moving body is pushed toward the screw portion of the rotary shaft.

Further, the drive position detecting means is constructed such that a spacer is attached to the rotary shaft for accommodating various electric actuators having different strokes of the output means.

Further, the drive control means fetches the detection value of the position detection sensor when the operation switch of the operation means is turned on and when the output means is advanced or retracted, and collates it with a limit value preset in the drive control means. Determine whether or not the output means can be advanced or retracted from the current position, and only when the output means can be advanced or retracted, the electric motor is driven and the output means of the electric actuator is advanced or retracted.
Configured to retract.

[0013]

According to the present invention, as described above, the drive position detecting means includes the moving body screwed to the rotary shaft by the rotation of the motion converting means transmitted to the rotary shaft through the reduction gear group. Since it is configured to move along the direction and follow the movement of the moving body to sequentially change the detection value (dividing resistance) of the position detection sensor (sliding resistor), de-energization at the time of power failure etc. Even if the electric actuator is manually operated at this time, the current position of the output means can be determined based on the detection value of the position detection sensor at the start of energization, so that the electric actuator can be operated without causing a malfunction.

Further, since the length of the screw portion of the rotary shaft is set so that the movable body can be disengaged from the screw portion at both left and right ends thereof, the electric actuator is manually operated, for example. In this case, even if a deviation occurs between the current position of the output means and the detected value of the position detection sensor due to an unforeseen situation, the moving body that follows the output means may move out of the screw portion of the rotary shaft. Since it does not exist, the moving body itself and the position detection sensor that follows the moving body are not damaged at all. In addition, since elastic members such as compression springs are attached to the left and right ends of the moving body, when the moving body comes off the threaded portion of the rotary shaft, the output means is driven in the opposite direction. Then, since the moving body is pushed by the elastic force of the elastic member toward the threaded portion side of the rotating shaft and screwed again, the moving body is never held apart from the threaded portion, and it is ensured. The detection value of the position detection sensor can be changed.

Further, when the drive position detecting means is used in an electric actuator having different strokes when the output means advances and retracts by mounting a spacer on the rotary shaft, especially when the stroke of the output means is short. Even when used, the elastic members attached to the left and right ends of the moving body can contact the spacers to remove the backlash, so that the outer diameter of the drive position detecting means can be used without being changed. There is also an advantage that you can.

Further, according to the present invention, as described above, the detection value of the position detection sensor at the time of turning on the operation switch and at the time of the advance / retreat of the output means is collated with the limit value preset in the drive control means. It is configured so that it is possible to judge whether or not the drive rod can be advanced or retracted, and the value detected by the position detection sensor is a value at which the output means must not be advanced or retracted. if there is,
Since no drive command is output to the electric motor, it is possible to surely prevent the problem of inducing a failure of the electric actuator by operating the operation switch at the advance / reverse limit position of the output means.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a plan view showing an example in which the electric actuator equipped with the drive position detecting device of the present invention is used in an electric bed used for medical institutions, for example.
In FIG. 1, reference numeral 1 denotes a bed, which is roughly composed of a base frame 1a in which angle steel or the like is framed in a rectangular shape, and back, floor, and leg frames 1b, 1c, and 1d attached to the upper part of the base frame 1a. A mat or the like (not shown) is laid on each of the frames 1b, 1c, 1d of the back, floor and legs. A _{1 to} A ₃ are electric actuators attached to the lower part of the base frame 1a, which are respectively drivingly connected to a link mechanism (not shown) to move the bed 1 up and down together with the base frame 1a, and the back frame 1b and the leg frame 1d. It is configured to be individually tilted at a predetermined angle.

Next, the structure of the electric actuators A _{1 to} A ₃ will be described with reference to FIGS. The electric actuators A _{1 to} A ₃ have the same structure except for the length of the stroke for the drive rod to advance and retreat, so an example used for the electric actuator A ₁ that raises and lowers the back frame 1b. Will be described. As shown in FIGS. 2 to 4, the electric actuator A ₁ is roughly classified into drive means 2 for driving the electric actuator A _1.
A motion converting means 3 for converting the rotary motion from the driving means 2 into a linear motion; an output means 4 for outputting the linear motion converted by the motion converting means 3; and an intermediate part of the motion converting means 3. The driving force control means 5 and the driving force control means 5 are generally configured.

Next, the structure of the driving means 2 will be described. In FIG. 2, 6 is an electric motor that is a drive source of the electric actuator A, and 7 is a lower side of the electric motor 1 (lower side of FIG. 1). For example, as shown in FIG. 5, a worm 8 connected to a rotor shaft (not shown) protruding from the electric motor 6 and a worm wheel 9 meshing with the worm 8 are used to drive the electric motor 6 to a predetermined position. Decelerate the rotation speed. The electric motor 6 and the speed reducing means 7 drivingly connected to the electric motor 6 constitute the driving means 2 for the electric actuator A.

Reference numeral 10 designates a hollow cylindrical shape in which a speed reducing means 7 drivingly connected to the driving means 2 and a motion converting means 3 interlocking with the speed reducing means 7 for decelerating driving are linearly (horizontally) arranged and housed. On one end portion (left side in FIG. 2) of the casing 10, an electric motor 6 constituting a main part of the driving means 2 is vertically erected vertically as shown in FIG. 7 and is rotatably mounted.

Next, the structure of the motion converting means 3 will be described. The motion converting means 3 is an electric motor 6 of the driving means 2.
A cylinder that is formed at the other end (right side in FIG. 2) of the casing 10 as shown in FIG. A trapezoidal screw 12 with a certain lead in a portion protruding from the opening 11 of the shape, and a screw shaft 13 on which the worm wheel 9 of the speed reducer 7 is pivotally mounted on the base end side without the trapezoidal screw 12. Hollow output means 4 drivingly coupled via a nut 14 screwed with the trapezoidal screw 12 of the screw shaft 13.
And the drive rod 15 as

On the other hand, in a portion located inside the opening 11 of the screw shaft 13 inside the casing 10, the screw shaft 13 located on the bottom side inside the opening 11 of the casing 10 (right side in FIG. 2) is A thrust bearing 17 inserted through a collar 16 that is fixed by using a locking pin or the like, and a speed reduction means 7
A radial bearing 19 inserted into the bearing housing 18 by being fitted to the screw shaft 13 on the side, and the screw shaft 13 is attached to the radial bearing 19 and the opening end of the casing 10 that opens toward the speed reduction means 7 side. Bearing member 2 provided on the cover 20
It is rotatably supported by 0a.

Further, as shown in FIG. 2, the base end of the fixed cylinder 21 into which the drive rod 15 as the output means 4 is inserted so as to move forward and backward is inserted into the opening 11 of the casing 10 inside the opening 11. Is affixed to the stepped portion with a stopper 21a and is non-removably screwed. Then, as shown in FIG. 2, the drive rod 15 loosely fitted to the fixed cylinder 21 is drivingly connected to the screw shaft 13 of the motion converting means 3 via a nut 14 to rotate the screw shaft 13 in a predetermined direction. Then, the nut 14 is moved forward and backward in a linear direction by the screw action of the nut 14, and the member fixed to the tip of the drive rod 15 can be pushed or pulled back. The stopper 21a limits the backward movement of the nut 14, and the tip of the trapezoidal screw 12 of the screw shaft 13 is also provided with a stopper (not shown) that limits the forward movement of the nut 14.

Next, the driving force control means 5 will be described. The driving force control means 5 is a one-way clutch 23 provided on a holder 22 that is attached to the screw shaft 13 and is interposed between the bearing housing 18 and the thrust bearing 17.
A brake shoe 24 fixed to one end portion (left side in FIG. 2) of the holder 22 and attached to an end portion (right side in FIG. 2) of the bearing housing 18 while being held in sliding contact with the brake shoe 24 at all times. And a brake disc 25.

The one-way clutch 23 is configured to rotate integrally with the rotating object (screw shaft 13 in this example) in one direction, and freely rotate the object in the other direction. When the one-way clutch 23 is attached to the screw shaft 13 shown in FIG. 2 in this example, when the screw shaft 13 is to be rotated in the advancing direction of the drive rod 15, the screw shaft 13 is freely rotated, and conversely, the screw shaft 13 is rotated. When it is intended to rotate 13 in the backward direction, it is attached so as to rotate together with it.

Therefore, when the screw shaft 13 is rotated by the drive means 2 in the direction in which the drive rod 15 is retracted, the one-way clutch 23 and the holder 22 fitted with the one-way clutch 23 are provided.
Since the screw shaft 13 is rotated while rotating the screw shaft 13 integrally with the screw shaft 13, in this case, the screw shaft 13 holds the brake shoe 24 fixed to the holder 22 and the brake disc 25 attached to the bearing housing 18. A large braking force is applied by the sliding of the and, and the rotation thereof is suppressed.

Further, in FIG. 2, reference numeral 26 denotes the casing 1.
It is a fixing member such as a snap ring which is a C-shaped ring that is fitted inside the opening end that is open in the direction in which the zero speed reducing means 7 is accommodated and that prevents the bearing housing 18 from being pulled out. In FIG. 3, 27 and 27 are pivot shafts of an electric actuator A formed integrally with the casing 10 so as to project in a direction orthogonal to the axial direction of the casing 10, and the electric actuator A is provided at the center. attaching hole 2 of the screw holes or the like for pivotally supporting _one
8, 28 are drilled. In addition, in FIGS.
Reference numeral 29 is a mounting hole provided at the tip of the drive rod 15. Although the screw shaft 13 is rotatably supported in the casing 10 by a radial bearing 19 and a bearing member 20a provided on the cover 20, the screw shaft 13 is substantially the radial bearing 19, the bearing member 20a, and the screw shaft. It goes without saying that it is rotatably supported while being maintained in a horizontal state by a nut 14 screwed to 13.

Next, referring to FIGS. 6 to 14, the casing 1
0 (see FIG. 2), the drive position detection device 4 of the present invention.
The structure of 0 will be described. In FIG. 6, reference numeral 41 denotes a reduction gear group that decelerates the rotational movement of the screw shaft 13 to about 1/2 and transmits it to the drive position detecting device 40. As shown in FIG. The drive gear 42 fixed to a position close to the drive gear 42 is provided on the drive position detecting device 40 side that meshes with the drive gear 42 by utilizing the opening 11a formed by cutting the upper surface inside the opening 11 of the casing 10. It is composed of an intermediate gear and a driven gear described later.

7 to 9, reference numeral 43 denotes a frame of the drive position detecting device 40, and as shown in FIG. 7, mounting portions 43a formed at both ends thereof are provided on the casing 10 by tightening members such as screws. Screw seat (only one is shown in Fig. 2) 1
It is attached to the casing 10 by being fastened to 0b. As shown in FIGS. 7 and 9, reference numeral 44 denotes a rotary shaft which is rotatably arranged along the axial direction of the frame 43, and a screw portion 45 is screwed at a substantially central portion thereof. A driven gear 46 is provided at one end of the rotary shaft 44.
However, the rotary shaft 44 is fixed to the rotary shaft 44 so as to be rotatable in cooperation therewith, and a retaining ring 47 is fixed to the other end of the rotary shaft 44 so as not to be removed from the frame 43. Further, an elastic member 47a such as a spring is inserted between the retaining ring 47 and the frame 43 to remove the play of the rotary shaft 44 which adversely affects the position detection accuracy.

48 is a frame 4 as shown in FIGS.
3 is a support shaft that horizontally projects integrally with the frame 43 from the extending end of the right side wall 43d. The support shaft 48 meshes with a large gear 49a that meshes with the drive gear 42 and a driven gear 46. An intermediate gear 49 composed of a small gear 49b is rotatably attached to a retaining ring 50 so as not to be removed.

Reference numeral 51 denotes a moving body which is movably screwed into the threaded portion 45 of the rotary shaft 44, and as shown in FIGS.
The engaging portion 51a formed on the upper portion of the frame 43 is engaged with the recessed groove 43c (see FIG. 11) of the guide 43b extending from the rear back portion 43e of the upper surface toward the front side (right side in FIG. 10). As a result, the moving body 51 moves on the rotating shaft 44 along the guide 43b without rotating.
8 and 9, reference numeral 52 denotes a pair of elastic members, which are compression springs and the like attached to the left and right ends of the moving body 51 by screwing the bases thereof, and as shown in FIG. When the threaded portion 51b screwed on the inner peripheral surface of the moving body 51 falls off from the threaded portion 45 of the rotary shaft 44, the free end of one elastic member 52 is pressed against the left side wall 43f of the frame 43 or a spacer described later. The moving body 51 is pushed toward the threaded portion 45 side of the rotary shaft 44 and screwed again by the elastic force generated as a result.

Further, the free end of the elastic member 52 is brought into contact with the left side wall 43f (left side in FIG. 9) of the frame 43 or the spacer described later at the limit position of advance / retreat of the drive rod 15. The backlash existing in the threaded portion between the rotary shaft 44 and the moving body 51, which adversely affects the accuracy of position detection, is eliminated, and in particular, the drive rod 15
It also has the function of improving the position detection accuracy in the vicinity of the forward / backward limit position.

As shown in FIG. 1, since the electric actuators A _{1 to} A ₃ used for the bed 1 have different strokes for advancing / retreating the driving rod 15 at the respective places of use, the shorter the stroke of the driving rod 15 is. Since the moving amount of the moving body 51 of the drive position detecting device 40 is also small, the rotary shaft 44 of the drive position detecting device 40 of the electric actuator A ₁ having a short stroke of the drive rod 15 is
As shown in FIGS. 10 to 12, the spacer 53 is a frame 4
3, the lower opening 43g of the spacer 53 is used to move from the opening end 53a of the spacer 53 to the rotary shaft 44 as shown by the chain double-dashed line in FIG.
11 and insert the spacer 53 in this state by rotating it counterclockwise by 90 °, as shown by the solid line in FIG. 11, to bring the spacer 53 into contact with the elastic member 52 attached to the moving body 51. Thus, the backlash generated between the screw portion 45 of the rotary shaft 44 and the moving body 51 is removed.

Further, the drive position detecting device 4 shown in FIG.
0 (driving position detecting device for the electric actuator A ₁ having a short stroke of the driving rod 15) removes the spacer 53 from the rotating shaft 44 and replaces the rotating shaft 44 and the position detecting sensor 54 as shown in FIG. By
The elastic member 52 of the moving body 51 is the right side wall 43 of the frame 43.
Since the backlash can be removed by contacting d, the electric actuator A having a long stroke of the drive rod 15
₂ (see FIG. 1) can be shared as the drive position detecting device 40a.

Further, when the spacer 53 is attached to the rotating shaft 44 as described above, as shown in FIG. 11, the collar piece 53b located on the opposite side of the opening end 53a comes into contact with the wall portion 43h of the frame 43. Since it is possible to prevent the rotation, the spacer 53 is rotated by vibration or the like and the rotation shaft 4 is rotated.
4 does not fall out of the spacer 4, and the free end of the one elastic member 52 attached to the moving body 51 is securely attached to the spacer 5
The backlash can be removed by abutting on No. 3.

Reference numeral 54 denotes a position detecting sensor composed of, for example, a sliding resistor whose resistance value is varied in a straight line direction. As shown in FIG. 7, the sensor main body 54a is mounted on the guide 43b of the frame 43. Mounting piece 54
b is fixed to the upper back portion 43e of the upper surface of the frame 43 by ultrasonic welding or the like and attached to the frame 43. Reference numeral 55 denotes a lever body that protrudes from the lower portion of the position detection sensor 54 for varying the detection value (resistance value) of the position detection sensor 54, and is screwed onto the rotary shaft 44 as shown in FIGS. By engaging with the engaging groove 51a ₁ of the engaging portion 51a of the moving body 51, the rotary shaft 4 can be integrated with the moving body 51.
4 to move the detection value (resistance value) of the position detection sensor 54. Reference numeral 56 is a signal line for sending the detected value to a CPU (central processing unit) of a controller (drive control means) described later.

Next, FIG. 18 is a drive circuit diagram for driving the drive unit (electric actuator A ₁ ) of the bed 1, for example. In FIG. 18, reference numeral 60 denotes an operator unit for performing a raising / lowering operation of the back frame 1b of the bed 1, for example, as shown in FIGS.
Operation switch (UP switch) SW to wake up
₁ and the operation switch for lowering the back frame 1b (D
OWN switch) SW _2, and each operation switch SW ₁ , SW ₂ is connected to an input / output interface 61 in the controller, which will be described later.

Reference numeral 62 denotes a controller (drive control means) for the electric actuator A ₁ , which is an input / output interface 61.
A CPU 63, a drive unit 64 of the electric motor 6, a power supply unit 65 of the position detection sensor 54, and a low-pass filter 67.
It is roughly configured by. Next, the drive unit 64 of the electric motor 6 selects a speed detection unit 68 for controlling the speed of the electric motor 6, a rotation direction and a speed of the electric motor 6,
It is composed of an inverter 69 for driving the electric motor 6 and a power supply unit 70 for supplying electric power to the electric motor 6.

An input / output interface 61 is connected to the input end I _{1 of the} CPU 63, and a position detection sensor 54 is connected to the input end I ₂ via a low-pass filter 67. Further, the speed detecting unit 68 is provided at the output terminal O _1.
However, the output terminal O ₂ is connected to the inverter 69, the output terminal O ₃ is connected to the power supply section 70 of the electric motor 6, and the output terminal O ₄ is connected to the power supply section 65 of the position detection sensor 54. Reference numeral 71 denotes a step-down resistor when the signal line 55 of the position detection sensor 54 is broken. Note that reference numeral 30 shown in FIG. 2 is a cover body that covers the drive position detection device 40 that covers the upper surface of the casing 10.

Next, the operation of the electric actuator A ₁ of the present invention will be described with reference to FIGS. 2, 4 and 15 to 19. _First , a case where the electric actuator A ₁ is driven to raise the back frame 1b of the bed 1 at a predetermined angle will be described. When the back frame 1b is to be tilted, SW _{1 is set} to SW in step 100 of FIG.
₂ and step 103 may be replaced with retreat in advance, so the description thereof will be omitted.

When raising the back frame 1b of the bed 1, first, as shown in FIGS. 15, 18 and 19, it is judged whether or not the operation switch SW ₁ (UP switch) of the operator section 60 is turned on ( Step 10 of FIG.
0). If it is determined in step 100 that the operation switch SW ₁ is turned on to raise the back frame 1b of the bed 1, the process proceeds to step 101 C
Power is supplied from the sensor power supply unit 65 to the position detection sensor 54 according to a command from the PU 63. If it is determined in step 100 that the operation switch SW ₁ is not turned on, the process proceeds to step 106, in which the CPU 63 does not output a drive command to the electric motor 6 via the drive unit 64, so the electric motor 6 is stopped (see FIG. 19). Step 107) Hold the state.

Subsequently, the current position information (detection value) of the drive rod 15 detected by the position detection sensor 54 by the supply of the power is passed through the low pass filter 67 and the A / D converter (not shown) built in the CPU 63. The CPU6
3 (step 102 in FIG. 19). Then, based on the input detection value, it is determined in step 103 whether or not the drive rod 15 may be advanced from the current position. When it is determined that the drive rod 15 may be advanced from the current position, the process proceeds to step 104, the CPU 63 outputs a drive command to the drive unit 64, and the motor 6 is started in step 105. When it is determined in step 103 that the drive rod 15 should not be advanced based on the detection value from the position detection sensor 54, the process proceeds to step 106, in which the CPU 63 does not output a drive command to the electric motor 6 via the drive unit 64. Therefore, the electric motor 6 maintains the stopped state (step 107 in FIG. 19).

In step 105, when the electric motor 6 is started, the output from the electric motor 6 is decelerated to a predetermined rotational speed by the speed reducing means 7 and transmitted to the motion converting means 3, and the driving rod 15 advances the screw shaft 13. It rotates in the direction (for example, counterclockwise). Then, by rotating the screw shaft 13, the nut 14 is moved from the base end side of the screw shaft 13 shown in FIG. 2 to the tip end side of the screw shaft 13 as shown in FIG. The back frame 1b of the bed 1 can be raised at a predetermined angle from a horizontally tilted state via a link mechanism.

Since the screw shaft 13 which is rotated by the activation of the electric motor 6 is set to freely rotate with respect to the one-way clutch 23 when the drive rod 15 advances, the screw shaft 13 is the one-way clutch. 23
Brake shoe 24 fixed to holder 22 fitted with
The brake disc 25 can be smoothly rotated without being braked by sliding.

Next, the above steps 100 to 10
When the drive rod 15 is advanced by repeating the operations up to 5 and the back frame 1b of the bed 1 is stopped at a desired angle, the operator (patient or the like) operates the operation switch SW of the operator unit 60. _When you stop inputting ₁ ,
In step 100, it is determined that the operation switch SW ₁ has not been turned on, and the process proceeds to step 106, in which the electric motor 6
Since the output of the drive command to is stopped, the electric motor 6 stops its drive in step 107 of FIG. 19 and stops the advance of the drive rod 15. When the back frame 1b stopped at the time when the desired angle is reached is raised again, the operation switch SW ₁ may be turned on again.

Further, the above steps 100 to 10
By repeating the operation up to 5, the drive rod 1
5 is advanced to raise the back frame 1b of the bed 1, and when the back frame 1b is automatically stopped when a predetermined limit angle is reached, the drive rod 1
The moving body 51 of the drive position detecting device 40 following the advance of FIG.
Moves from the left side of the rotary shaft 44 shown in FIG. 17 to the right side of the rotary shaft 44 shown in FIG. 16, and when the detection value of the position detection sensor 54 becomes a value that should not advance the drive rod 15 further, the CPU 63 In step 103, it is determined that the drive rod 15 should not be advanced based on the detection value from the position detection sensor 54, and the process proceeds to step 106, in which the output of the drive command to the electric motor 6 is stopped, so step 107 in FIG. At, the electric motor 6 stops its driving and automatically stops the drive rod 15 at the advance limit position.

In this state, even if the operation switch SW ₁ is turned on to further raise the back frame 1b, C
Since the PU 63 determines that the drive rod 15 should not be advanced based on the detection value of the position detection sensor 54 and does not drive the electric motor 6, the occurrence of an accident can be prevented. In addition, the operator (patient etc.) can operate the operation switch SW.
Even if the operation rod SW is turned on by the operation switch SW ₁ being turned on due to an unforeseen situation such as keeping on inputting ₁ without knowing it, or mischievous or placing an object on the operator unit 60, As described above, since the drive rod 15 automatically stops at the advance limit position, it is possible to prevent an accident from occurring due to an operation error or an unexpected situation.

Further, as shown in FIG. 4, the drive rod 15 is usually provided with a nut 14 screwed to the base end of the drive shaft 15.
The advancing operation is stopped by contacting a stopper (not shown) provided at the tip of the trapezoidal screw 12 of No. 3, so that the moving body 51 of the drive position detecting device 40 that follows the drive rod 15 rotates. Threaded portion 45 of shaft 44
Therefore, it is possible to reliably suppress the problem that the electric actuator A ₁ malfunctions due to a deviation between the position of the drive rod 15 and the detection value of the position detection sensor 54.

As described above, the moving body 51 follows the advancing operation of the drive rod 15, and the rotating shaft 4 shown in FIG.
When moving from the left side of FIG. 4 to the right side as shown in FIG. 16, an unexpected situation (for example, during maintenance of the electric actuator A ₁ or the like, the position of the drive rod 15 and the detection value of the position detection sensor 54 are erroneously detected. When the moving body 51 is disengaged from the threaded portion 45 of the rotating shaft 44 as shown in FIG. 13 due to the case where the electric actuator A ₁ is attached to the bed 1 in the state where the gap is still generated, The moving body 51 moves the rotary shaft 44 in a direction opposite to that in the past, that is,
By rotating the drive rod 15 in the backward direction, the elastic force of the elastic member 52 attached to the right end portion is used to push the screw rod 45 side of the rotary shaft 44 and screw it again. By matching the current position of the drive rod 15 with the detection value of the position detection sensor 54, the moving body 51 follows the drive rod 15 and moves the rotary shaft 44 to reliably detect the current position of the drive rod 15. can do.

Further, when the advance of the drive rod 15 is stopped midway (when the drive means 2 is stopped), the drive rod 1
When the drive rod 15 stops at the advance limit position of 5, the screw rod 13 tries to rotate the screw shaft 13 in reverse due to the weight of the operator (patient, etc.), but one end of the holder 22 fitted with the one-way clutch 23. Brake shoe 24 fixed to
Is strongly pressed against the brake disc 25 by the weight or the like to generate a braking force, so that the drive rod 15 can be stopped well by the braking force.

In this way, the operation switches SW ₁ , SW ₂
When the drive rod 15 of the electric actuator A ₁ is moved forward and backward by operating the, and the back frame 1b of the bed 1 is raised and lowered, the present invention uses the reduction gear group 41 to rotate the rotary shaft 4.
The rotation of the screw shaft 13 transmitted to the moving body 4 causes the moving body 51 screwed to the rotating shaft 44 to move along the axial direction of the rotating shaft 44, and follows the movement of the moving body 51 to detect the position detection sensor 54. It is determined whether or not the drive rod 15 may be advanced / retracted based on the detection value of the position detection sensor 54 at the time when the operation switches SW ₁ and SW ₂ are turned on. Is configured to.

Therefore, for example, at the time of a power failure or the like, the cover 20 of the electric actuator A ₁ is removed, and the screw shaft 13 is manually operated by a manual handle or the like, so that the back frame 1 of the bed 1 is
Even if b is raised at a predetermined angle or tilted horizontally, the drive position detecting device 40 drivingly connected to the screw shaft 13 via the reduction gear group 41 causes the nut 14 to be attached to the screw shaft 13.
Since the current position is detected by following the advancing / retracting of the drive rod 15 screwed through the drive rod, the current position of the drive rod 15 can be determined based on the detection value of the position detection sensor 54 at the time of power recovery. As a result, if the value detected by the position detection sensor 54 is a value that does not allow the drive rod 15 to advance or retract at the time of restoration from the power failure, the drive command to the electric motor 6 is not output, so the operation switch SW ₁ ，
By operating SW ₂ at the limit position of advance / retreat of the drive rod 15, no malfunction occurs at all, and thus the problem that the electric actuator A ₁ causes a failure can be prevented.

Further, the drive rod 15 stops its advancing operation by coming into contact with a stopper (not shown) provided at the tip of the trapezoidal screw 12 of the screw shaft 13, so that the drive position detecting device 40 following the drive rod 15 is stopped. Moving body 51
Does not disengage from the threaded portion 45 of the rotary shaft 44, and it is possible to reliably suppress the problem that the electric actuator A ₁ malfunctions due to a deviation between the position of the drive rod 15 and the detection value of the position detection sensor 54. be able to. Further, since the length of the threaded portion 45 of the rotary shaft 44 is set to such a length that the moving body 51 can be disengaged from the threaded portion 45 at both left and right ends thereof, the electric actuator A
_In the case where ₁ is manually operated, even if the current position of the drive rod 15 and the detection value of the position detection sensor 54 deviate due to an unexpected situation, the moving body 51 that follows the drive rod 15 is Since the movable body 51 itself and the position detection sensor 54 that follows the movable body 51 are damaged because they do not move out of the screw portion 45, the problem that the position of the drive rod 15 cannot be accurately detected can be prevented. it can. In addition, in order to return the moving body 51 to the screw portion 45, the elastic force of the elastic members 52 attached to the left and right ends of the moving body 51 is used to move the screw shaft 13 in the opposite direction with the manual handle. It can be done simply by rotating it.

Although the operator section 60 of the electric actuator A ₁ of the present invention has been described as being provided with only the operation switches SW ₁ and SW ₂ , the back frame or the like is detected based on the detection value of the position detection sensor. It goes without saying that a plurality of light emitting diodes (LEDs) for displaying a tilted state or the like may be arranged, or an operation switch for raising and lowering the base frame 1a and raising and lowering the leg frame 1d may be provided. Is. Further, although the present invention has been described with reference to the example in which the back frame 1b of the bed 1 is raised, the back frame 1
It goes without saying that the same can be done when tilting b, when raising and lowering the base frame 1a, and when raising and lowering the leg frame 1d. Further, in the present invention, the position detection sensor 54 has been described by using the linear movement type sliding resistor as an example, but a rotary type sliding resistor may be used instead.

[0055]

Since the present invention is configured as described above, it has the following effects. (1) In the present invention, the moving body screwed to the rotating shaft is moved along the axial direction of the rotating shaft by the rotation of the screw shaft transmitted to the rotating shaft via the reduction gear group, and the moving body is moved. Since the detection value of the position detection sensor is changed sequentially following the above, even if the electric actuator is manually operated during a power failure, etc., the current position of the output means is detected by the detection value of the position detection sensor when the power is restored. Can be detected, the electric actuator can be operated without causing a malfunction.

(2) Further, since the length of the screw portion of the rotary shaft is set so that the moving body can be disengaged from the screw portion at both left and right ends thereof, the electric actuator is manually operated. In this case, even if there is a deviation between the current position of the drive rod and the detection value of the position detection sensor due to an unforeseen situation, the moving body that follows the drive rod does not move out of the threaded portion of the rotating shaft. The moving body itself and the position detecting sensor that follows the moving body are never damaged. In addition, since elastic members such as compression springs are attached to the left and right ends of the moving body, when the moving body comes off the threaded portion of the rotating shaft, the drive rod is driven in the opposite direction. Then, the moving body is pushed by the elastic force of the elastic member toward the screw portion side of the rotating shaft and screwed again, so that the moving body is never left out of the screw portion, and the position is surely maintained. The detection value of the detection sensor can be changed.

(3) Further, since the spacer is attached to the rotary shaft of the drive position detecting device used for the electric actuator having a short stroke of the drive rod, the elastic member attached to the moving body screwed to the rotary shaft is By abutting the spacer, it is possible to remove backlash between the threaded portion of the rotary shaft and the moving body, so that the drive position is detected by the electric actuator having different strokes when the drive rod advances and retracts. Even when the device is used, there is an advantage that it can be used without changing the outer diameter dimension of the drive position detecting device.

(4) Further, according to the present invention, the drive rod is moved forward by collating the detection value of the position detection sensor at the time when the operation switch is turned on and when the drive rod is advanced / retracted with the limit value preset in the controller. -It is configured to judge whether or not it is possible to move backward, and the motor is driven and output only when the value detected by the position detection sensor allows the output means to move forward or backward at this point. Since the means is advanced and retracted, the output means
By operating the operation switch at the backward limit position, it is possible to prevent the problem that the electric actuator causes a failure.

[Brief description of the drawings]

FIG. 1 is a plan view showing a state in which an electric actuator including a drive position detecting device of the present invention is used in an electric bed.

FIG. 2 is a vertical cross-sectional view showing a state in which the drive rod is retracted in the electric actuator including the drive position detecting device of the present invention.

FIG. 3 is a plan view showing a notched main portion of an electric actuator including the drive position detection device of the present invention.

FIG. 4 is a vertical cross-sectional view showing a state in which a drive rod is advanced in an electric actuator equipped with the drive position detecting device of the present invention.

FIG. 5 is a cross-sectional view showing a notch of a main part of a speed reducer.

FIG. 6 is a side view showing a coupled state of the screw shaft and the drive position detecting device.

FIG. 7 is a plan view showing a coupled state of a screw shaft and a drive position detecting device.

FIG. 8 is a front view of a drive position detection device.

FIG. 9 is a front view showing a driving position detection device in a vertical section.

10 is a vertical cross-sectional side view taken along line XX of FIG.

11 is a vertical cross-sectional side view taken along the line YY of FIG.

FIG. 12 is a perspective view of a spacer.

FIG. 13 is an enlarged front view showing a main part of the drive position detecting device.

FIG. 14 is a vertical sectional front view showing another example of the drive position detecting device.

FIG. 15 is a plan view of an operator section.

FIG. 16 is a vertical cross-sectional front view showing a state in which the position detection sensor is detecting the advance limit position of the drive rod.

FIG. 17 is a vertical cross-sectional front view showing a state in which the position detection sensor detects the backward limit position of the drive rod.

FIG. 18 is a schematic drive circuit diagram of an electric actuator.

FIG. 19 is a flowchart for advancing (retracting) a drive rod.

[Explanation of symbols]

6 Electric Motor 13 Screw Shaft 15 Drive Rod 40 Drive Position Detecting Device 41 Reduction Gear Group 44 Rotating Axis 51 Moving Object 52 Elastic Member 53 Spacer 54 Position Detecting Sensor 60 Operator Part 62 Controller 63 CPU A _{1 to} A ₃ Electric Actuator SW ₁ , SW ₂ Operation switch

Claims (5)

[Claims] 1. A drive unit comprising a motor for generating a rotary motion and a decelerating unit for decelerating the rotary motion of the electric motor to a predetermined speed, and the rotary motion decelerated to the predetermined speed by the speed reducer is converted into a linear motion. And a driving force control means inserted in the middle of the motion converting means, and an electric actuator is configured. A driving position detecting unit that is drivingly connected to the motion converting unit and detects the current position of the output unit by following the advancing / retreating of the output unit to the electric actuator; Drive control means for correspondingly controlling the drive means, and operation means provided with a plurality of operation switches for operating the electric actuator. Drive position detection device for electric actuator. 2. The drive position detecting means is screwed to a rotary shaft for transmitting the rotary motion of the motion converting means through a reduction gear group and a screw portion screwed to the rotary shaft, to thereby perform the decelerating rotation. By the moving body that moves along the axial direction of the rotation axis,
2. A position detecting sensor that changes the detection value of the moving body so as to follow the movement of the moving body.
A drive position detection device for the electric actuator described. 3. The drive position detecting means sets the length of the threaded portion of the rotating shaft to a length at which the moving body can be disengaged from the threaded portion at both left and right ends of the moving body. An elastic member, such as a compression spring, is attached to each of the left and right ends so as to push the moving body toward the threaded portion of the rotating shaft when the moving body is disengaged from the threaded portion of the rotating shaft. The drive position detection device for an electric actuator according to claim 1. 4. The drive position detecting means is provided with a spacer attached to the rotary shaft for accommodating various electric actuators having different strokes of the output means. Drive position detection device for the electric actuator of. 5. The drive control means includes a detection value of the drive position detection means at the time when the operation switch of the operation means is turned on and when the output means is advanced and retracted, and a limit value preset in the drive control means. Is checked to determine whether the output means may be advanced or retracted from the current position,
2. The drive position detecting device for an electric actuator according to claim 1, wherein the drive means is driven only when it is determined that the output means can be advanced or retracted, and the output means is advanced or retracted.