JP6617959B2 - Method and apparatus for detecting screw tightening torque of constant torque electric screwdriver - Google Patents

Description

  In the present invention, a torque limiter is coupled to a drive shaft output via a speed reduction mechanism with respect to a drive output shaft of an electric motor, and a rotary tool such as a driver bit is connected to a driven shaft of the torque limiter to perform screw tightening work. When the screw tightening torque exceeds the torque value set in the torque limiter, the constant torque electric screwdriver is configured so that the torque limiter is activated and the drive shaft idles with respect to the driven shaft to achieve the required screw tightening operation. The present invention relates to a screw tightening torque detection method and apparatus for a constant torque electric screwdriver that can easily and easily detect a screw tightening torque value upon completion of screw tightening associated with operation of a torque limiter.

  The present applicant is suitable for the assembly of small precision parts and the coupling and assembly of fragile parts such as plastic products by applying a torque limiter that can set the tightening torque of the screw tool with high accuracy. Various electric motor-driven electric drivers have been developed and patented.

  An electric driver using this type of torque limiter has a reduction mechanism connected to the output shaft of the electric motor, a drive shaft of the torque limiter is coupled to the output shaft of the reduction mechanism, and the transmission rotation shaft of the torque limiter is connected to the driver bit. And screw tightening based on a torque set value defined by the torque limiter.

  Therefore, for example, on the outer peripheral surface portion of the transmission rotation portion of the torque limiter coupled to the driver bit, a sensor sensing member composed of a plurality of magnets arranged at equal intervals in the circumferential direction is provided, and the sensor sensing member By arranging a sensor composed of a Hall element in the gripper casing corresponding to the above, in the screw tightening operation by the driver bit, the state where the drive shaft side of the torque limiter idles and the transmission rotation unit side stops rotating is described above. A constant-torque electric driver configured to detect by a sensor and thereby stop driving the electric motor was developed, and a patent was obtained (see Patent Document 1).

  The constant torque electric driver described in Patent Document 1 detects the load current or load voltage of the electric motor when the torque limiter detected by the sensor is activated, and the load current value or load voltage value is an initial value. When the value changes to a predetermined value or more as compared with the above, a required alarm is generated so that an abnormality or failure of the screw tightening state can be easily confirmed.

  Further, the present applicant, as an electric motor driving type electric driver using a torque limiter, grips the rear end portion of the electric motor via a flat plate (torsion bar) extending coaxially therewith. A torque-fixed screwdriver was developed that was fixed in a casing and configured to measure a torque value by attaching a strain gauge (strain gauge) to one side of the plate, and obtained a patent (see Patent Document 2).

In the torque fixed type driver described in Patent Document 2, a cylindrical permanent magnet is fixedly arranged on the inner peripheral surface of the outer case, and a drive shaft is rotatably inserted in the center of the permanent magnet. A torque limiter is provided that supports and fixes a cylindrical magnetic member facing and not in contact with the inner peripheral surface of the permanent magnet at the outer peripheral portion of the shaft, and closing and fixing the rear end portion of the outer case with a lid. ,
(1) The torque limiter is rotatably surrounded and held by a gripper casing, and at the rear end of the torque limiter, is coaxial with the drive shaft of the torque limiter with respect to a lid for closing and fixing the case. An output shaft of the electric motor is detachably coupled, (2) an outer casing of the electric motor is detachably coupled to a gripping casing that surrounds and holds the torque limiter, and (3) the electric motor is further coupled The rear end is fixed in the grip casing through a flat plate (torsion bar) extending coaxially therewith, and a strain gauge (strain gauge) is attached to one side of the plate to torque It is comprised so that a value can be measured.

  Further, the present applicant detects that when a required load torque is received at the coupling portion (planetary gear reduction mechanism) between the output shaft of the electric motor and the driven shaft (driver bit), the rotation of the output shaft is detected. An electric rotary tool having a clutch mechanism for interrupting output transmission and a mechanism for simultaneously detecting the torque value at that time and automatically stopping the electric motor was developed and patented (see Patent Document 3). .

The electric rotary tool described in Patent Document 3 is provided with a grip portion incorporating an electric motor, and a driven shaft is coupled to the output shaft of the electric motor via a planetary gear reduction mechanism to surround the planetary gear reduction mechanism. An internal gear that meshes with the planetary gear of the planetary gear reduction mechanism is rotatably disposed in a cylindrical casing, and a clutch mechanism that uses a steel ball is provided between the internal gear and the grip casing, and this An electric rotary tool provided with a torque detection mechanism provided with a means for detecting the operation of the clutch mechanism,
A notch that opens a part of the internal gear in the clutch mechanism is provided, and one end of the swing detection piece is disposed in this notch with the steel ball of the clutch mechanism, and the other end of the swing detection piece is disposed. It is configured to be fixed to a part of the grip casing and receive a stress displacement during clutch operation, and a strain gauge (strain gauge) is stretched on the displacement part of the swing detecting piece, and the output signal of the strain gauge A torque detection circuit that detects the torque value based on the torque value and an automatic stop circuit that stops the driving of the electric motor based on the torque value are provided to perform the torque detection and automatic stop.

  In this case, as the swing detection piece, a torque adjustment formed by projecting a part of the gripping casing facing the circumferential groove as a clutch surface engraved on the outer peripheral portion of the internal gear radially outward. The spring housing case is disposed in a part of the notch that is close to the gripping part casing, extends outside the notch provided in a part of the gripping part casing and extends in parallel with the output shaft of the electric motor, and It is described that the other end of the motion detection piece is fixed to a part of the grip casing, and a strain gauge is stretched on the parallel extending portion of the swing detection piece.

  The automatic stop circuit detects the peak value of the output signal based on the output signal obtained from the strain gauge, and simultaneously detects that the output signal of the strain gauge decreases due to the clutch operation. A comparison circuit for generating a signal for temporarily shutting off the switch circuit is provided.

Japanese Patent No. 5986640 Japanese Patent No. 4313283 Japanese Patent No. 3600255

  The constant torque electric driver proposed in Patent Document 1 described above detects the load current or load voltage of the electric motor when the torque limiter is activated by a sensor, and compares the load current value or load voltage value with an initial value. In the case where the torque limiter is changed to a predetermined value or more, it is possible to generate a required alarm and check the abnormality or failure of the screw tightening state. It has been found that it is important to detect an appropriate torque value as torque management.

  In a constant torque electric driver using this type of torque limiter, according to the torque fixed type driver described in Patent Document 2 previously proposed, the rear end portion of the electric motor is formed in a flat shape extending coaxially therewith. Since it is fixed in the grip casing through a plate (torsion bar) and a strain gauge is attached to one side of the plate, the torque value can be measured. When a stress displacement as a reaction force corresponding to the screw tightening torque transmitted to the driver bit in the tightening operation is transmitted to the flat plate (torsion bar), an overload of an electric motor or the like is added. In addition, the stress displacement as a reaction force corresponding to the screw tightening torque transmitted to the driver bit in the actual screw tightening operation is expressed as the strain gauge (strain gauge). Be detected as a properly transmitted to the screw tightening torque value for is inadequate, it is trouble even in terms of detection accuracy was confirmed.

  However, in an actual screw tightening operation, as a means that can appropriately detect the stress displacement as a reaction force corresponding to the screw tightening torque transmitted to the driver bit, for example, as an electric driver not using a torque limiter, As shown in Patent Document 3 previously developed by the present applicant, in an electric rotary tool having a clutch mechanism between an internal gear constituting a planetary gear reduction mechanism and a gripper casing, the clutch mechanism It is extremely appropriate to configure the component to detect the torque value by providing a strain gauge (strain gauge) so as to receive the stress displacement during clutch operation, and it is also effective in terms of accuracy. It has been confirmed that there is.

  However, in a constant torque electric screwdriver that does not have the clutch mechanism and uses a torque limiter, it is difficult to configure the torque detection means as shown in Patent Document 3 as it is.

  Therefore, the present inventor has made various studies in order to obtain a torque detection means that can appropriately detect the screw tightening torque loaded on the driver bit in the screw tightening operation in the constant torque electric screwdriver using the torque limiter. As a result of overlapping, a torque limiter that has been adjusted in advance to a hysteresis torque (set torque) corresponding to an appropriate screw tightening torque is provided, and the drive shaft of the electric motor is respectively connected to the drive rotation portion and the driven rotation portion of this torque limiter. When the screw is seated by screw tightening operation, the screw tightening torque by the driver bit exceeds the set torque of the torque limiter. At the same time as the drive rotating part of the torque limiter starts idling, the drive of the electric motor A sudden turning force is generated in the direction in which the internal gear of the planetary gear speed reduction mechanism coupled to the shaft is reversed with respect to the rotation of the output shaft. It has been found that the screw tightening torque by the electric screwdriver can be properly detected by the strain gauge by being configured so that it can be detected by a strain gauge as the stress displacement.

  That is, in this case, when detecting the rotational force generated suddenly in the reverse direction of the internal gear in the above-described screw tightening operation by the strain gauge as the stress displacement, the planetary gear reduction coupled to the drive shaft of the electric motor. The internal gear holding the mechanism is supported in a rotatable state, and a projection is provided on a part of the lower end surface of the internal gear, and the outside of the casing surrounding the internal gear with respect to the projection In addition, a torsion bar is provided in each of the upper and lower parts via a support member in parallel with the output shaft of the planetary gear speed reduction mechanism, the torsion bar is fixed by the upper support member, and the lower support member is set to be rotatable. A displacement detection arm projects horizontally from a part of the outer periphery of the lower support member, and its tip is provided on the casing. The displacement of the rotational force generated suddenly in the reverse direction with respect to the output shaft of the internal gear is achieved by engaging with the protrusion provided on the lower end surface of the internal gear through the portion. Can be effectively transmitted to the torsion bar via the displacement detection arm, and by appropriately providing a strain gauge on the side surface of the torsion bar, the above-described screw tightening torque can be easily detected. I found what I could do.

  When detecting the screw tightening torque by the strain gauge, in the work for screw tightening by the electric screwdriver, the start time of screw tightening by the driver bit is detected by the push operation switch, and then the required screw rotation until reaching the screw seating The amount of torque is detected by a rotary encoder provided in the torque limiter, and at the timing, the stress displacement generated in the internal gear of the planetary gear speed reduction mechanism is set to be detected. Detection can be easily achieved.

  In addition, since the appropriate screw tightening torque can be detected as described above, if an abnormality occurs in the timing for detecting the stress displacement generated in the internal gear described above, it is determined that the screw tightening is defective. Therefore, it is possible to appropriately and effectively achieve the quality determination of the screw tightening operation in this type of constant torque electric screwdriver.

  Accordingly, an object of the present invention is to detect an appropriate screw tightening torque in a screw tightening operation in a constant torque electric screwdriver using a torque limiter, and to easily and reliably achieve a screw tightening state determination. An object of the present invention is to provide a screw torque detection method and apparatus for a constant torque electric screwdriver.

In order to achieve the above object, a screw torque detection method for a constant torque electric screwdriver according to claim 1 of the present invention is such that a drive rotating part of a torque limiter is coupled to a drive shaft of an electric motor via a planetary gear reduction mechanism. And using a constant torque electric screwdriver configured to couple the driven rotating portion of the torque limiter to a driver bit and perform screw tightening based on the set torque of the torque limiter,
When the screw is seated by the screw tightening operation, the screw tightening torque by the driver bit exceeds the set torque of the torque limiter, and the drive rotating part of the torque limiter starts idling, and at the same time, coupled to the drive shaft of the electric motor The abrupt rotational force generated in the direction in which the internal gear of the planetary gear speed reduction mechanism is reversed with respect to the rotation of the output shaft is transmitted as stress displacement to the torsion bar, and the stress displacement of the torsion bar is screwed by a strain gauge. It is detected as torque.

  According to a second aspect of the present invention, there is provided a method for detecting a screw tightening torque of a constant torque electric screwdriver, wherein a screw tightening start time detected by the driver bit is detected by a push operation switch, and then the required screw rotation until the screw is seated. The amount is detected by a rotary encoder provided in the torque limiter, and the stress displacement generated in the internal gear of the planetary gear reduction mechanism is detected at the timing when the screw is seated.

  According to a third aspect of the present invention, there is provided a method for detecting a screw tightening torque of a constant torque electric screwdriver, wherein the screw tightening start time is detected by a push operation switch, and then the screw encoder is seated by a rotary encoder provided in the torque limiter. When the screw rotation amount is detected as a preset screw rotation amount and within an allowable range thereof, it is determined that the screw tightening torque is determined by proper screw tightening.

  According to a fourth aspect of the present invention, there is provided a method for detecting screw tightening torque of a constant torque electric screwdriver, wherein a screw tightening start point is detected by a push operation switch, and then a screw encoder is installed by a rotary encoder provided in a torque limiter. When the screw rotation amount is detected as being out of the preset screw rotation amount and its allowable range, it is determined that the screw tightening torque is due to screw tightening failure.

  According to a fifth aspect of the present invention, there is provided a method for detecting screw tightening torque of a constant torque electric screwdriver, wherein the stress displacement generated in the internal gear of the planetary gear reduction mechanism is screw tightened by a strain gauge at the timing of screw seating. When it detects as torque, it sets so that stop control of an electric motor may be performed.

According to a sixth aspect of the present invention, there is provided a constant torque electric screwdriver tightening torque detecting device that couples a drive rotating portion of a torque limiter to a drive shaft of an electric motor via a planetary gear speed reduction mechanism, and follows the torque limiter Composed of a constant torque electric screwdriver configured to couple a rotating part to a driver bit and perform screw tightening based on a set torque of the torque limiter,
Providing a protrusion on a part of the lower end surface of the internal gear, supporting the internal gear holding the planetary gear reduction mechanism coupled to the drive shaft of the electric motor in a rotatable state,
A torsion bar fitted with a strain gauge is provided in parallel with the output shaft of the planetary gear speed reduction mechanism on the outside of the casing surrounding the internal gear with respect to the protrusion, and a displacement detection arm is projected from one end thereof. ,
When the tip of the displacement detection arm is engaged with the protrusion and the screw is seated by a screw tightening operation, the stress displacement of the rotational force that occurs suddenly in the reverse direction from the output shaft of the internal gear is It is configured to transmit to the torsion bar via the displacement detection arm.

  According to a seventh aspect of the present invention, in the screw torque detecting device for a constant torque electric screwdriver, a strain gauge provided in parallel with the output shaft of the planetary gear reduction mechanism is mounted on the outside of the casing surrounding the internal gear. The torsion bar has one end fixed by an upper support member and the other end rotatably supported by a lower support member, and a displacement detection arm is disposed in a horizontal direction from a part of the outer periphery of the lower support member. The front end of the internal gear is configured to pass through an opening provided in the casing and engage with a protrusion provided on the lower end surface of the internal gear.

  The screw torque detection device for a constant torque electric screwdriver according to claim 8 of the present invention is provided with a push operation switch that performs a switch operation in response to an axial displacement of the driver bit, and is provided on the outer periphery of the torque limiter. A rotary encoder for detecting rotational displacement is provided, and the screw rotation amount is detected by the rotary encoder based on the switch operation of the push operation switch during screw tightening operation.

  According to the screw torque detection method for a constant torque electric screwdriver according to claim 1 of the present invention, a drive rotating portion of a torque limiter is coupled to a drive shaft of an electric motor via a planetary gear reduction mechanism, and the torque limiter is coupled. The driven rotation portion of the screwdriver bit is coupled to the driver bit so that the screw is tightened based on the set torque of the torque limiter. When the screw is seated by the screw tightening operation, the screw tightening torque by the driver bit is reduced. When the set torque of the torque limiter is exceeded, the drive rotation part of the torque limiter starts idling, and at the same time, the internal gear of the planetary gear reduction mechanism coupled to the drive shaft of the electric motor is reversed with respect to the rotation of the output shaft. The stress displacement due to the rapid rotational force generated in the direction of The quality determination of the screwing state can be performed reliably and easily with the detection of the screw tightening torque.

  According to the method for detecting screw tightening torque of the constant torque electric screwdriver according to claim 2 of the present invention, in the screw tightening operation, by detecting the start time of screw tightening by the driver bit by the push operation switch, Since the detection and setting of the timing at which the screw is seated can be made consistent, the detection of the screw tightening torque and the determination of pass / fail of the screw tightening state can be performed appropriately and reliably and easily.

  According to the method for detecting screw tightening torque of the constant torque electric screwdriver according to claim 5 of the present invention, by detecting the timing of screw seating and the stress displacement generated in the internal gear of the planetary gear reduction mechanism. The stop control of the electric motor can be appropriately performed.

  According to the screw torque detection device for a constant torque electric driver according to claim 6 of the present invention, the drive rotating portion of the torque limiter is coupled to the drive shaft of the electric motor via the planetary gear reduction mechanism, and the torque limiter A constant torque electric driver configured to couple a driven rotating part to a driver bit and perform screw tightening based on a set torque of the torque limiter, and to hold an planetary gear reduction mechanism coupled to a drive shaft of the electric motor. A planetary gear reduction mechanism is provided on the outer side of the casing that surrounds the internal gear with respect to the protrusion by providing a protrusion on a part of the lower end surface of the internal gear while supporting the null gear in a rotatable state. A torsion bar equipped with a strain gauge in parallel with the output shaft of When the tip of the position detection arm is engaged with the protrusion and the screw is seated by the screw tightening operation, the stress displacement of the rotational force generated suddenly in the direction opposite to the output shaft of the internal gear is By configuring so as to transmit to the torsion bar via the displacement detection arm, it is possible to reliably and easily achieve pass / fail judgment of the screw tightening state with appropriate detection of the screw tightening torque with a relatively simple structure. .

  According to the screw tightening torque detecting device of the constant torque electric screwdriver according to claim 7 of the present invention, the system for detecting the stress displacement generated in the internal gear of the planetary gear reduction mechanism for detecting the screw tightening torque. The configuration can be constructed simply and easily.

  According to the constant-torque electric screwdriver screw tightening torque detecting device according to the eighth aspect of the present invention, in the screw tightening operation, the screw tightening is performed by providing the push operation switch for detecting the start time of the screw tightening by the driver bit. Since the detection and setting of the timing at which the screw is seated can be matched, the detection of the screw tightening torque and the quality determination of the screw tightening state can be made appropriate and performed reliably and easily.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration explanatory diagram showing a system configuration for detecting screw tightening torque as an embodiment of a constant torque electric screwdriver screw tightening torque detection method according to the present invention. It is explanatory drawing which shows one Example of the main structures of the screwing torque detection apparatus of the constant torque electric driver which concerns on this invention. FIG. 3 is an explanatory plan view of a main part that performs screw tightening torque detection of the screw tightening torque detection device of the constant torque electric screwdriver shown in FIG. 2. FIG. 4 is an enlarged explanatory view of a main part of a main part that performs screw tightening torque detection of the screw tightening torque detection device of the constant torque electric driver shown in FIG. 3.

  Next, an embodiment of a torque detection method for a constant torque electric screwdriver according to the present invention will be described in detail below with reference to the accompanying drawings in relation to an apparatus for performing the method.

  FIG. 1 is a schematic configuration explanatory view showing an apparatus for carrying out a torque detection method for a constant torque electric screwdriver according to the present invention. That is, in FIG. 1, reference numeral 10 indicates a constant torque electric screwdriver. An electric motor 12, a drive switch 14 for driving the electric motor 12, and the electric motor 12 are provided in a grip portion of the electric screwdriver 10. A planetary gear speed reduction mechanism 16 and a torque limiter 18 coupled to a drive shaft (not shown) are respectively built in, and a driver bit 20 is coupled via the torque limiter 18.

  In the electric driver 10, the switch operating member 15 that operates the drive switch 13 of the electric motor 12, the electric motor control circuit 22 that performs drive control and stop control of the electric motor 12, and the rotation amount of the torque limiter 18. A rotary encoder 24 is provided for detection, that is, counting of the rotation state. Further, a known push operation switch 26 is provided for the driver bit 20 for detecting the axial displacement and detecting the start point of the screw tightening operation.

  In the present invention, in the planetary gear reduction mechanism 16, when the screw is seated by the screw tightening operation, the internal gear constituting the planetary gear reduction mechanism 16 is reversed with respect to the rotation of the output shaft. A strain gauge 28 is provided for detecting a stress displacement as a rapid rotational force generated in the screw tightening torque.

  In the constant torque electric screwdriver 10 of the present embodiment, a brushless motor can be suitably used as the electric motor 12. The switch operating member 15 for operating the drive switch 14 to drive the electric motor 12 is configured, for example, as a known lever member provided on the outer periphery of the grip portion of the electric motor 12 or as a known push operating member. can do.

  In the constant torque electric screwdriver 10 of the present embodiment, as the torque limiter 18, for example, a known torque limiter using a magnetic method is used as disclosed in Patent Documents 1 and 2, or in Patent Document 2 described above. As disclosed, a known torque limiter using a coil spring system can be used.

  Further, the torque limiter 18 is coupled to an output shaft (not shown) of the planetary gear speed reduction mechanism 16 and is driven to rotate integrally with the driver bit 20 in the screw tightening direction during the screw tightening operation, as will be described later. For this reason, a known magnetic rotary encoder 24 is provided on the outer periphery thereof, and the rotational state of the torque limiter 18 in relation to the driver bit 20, that is, the amount of screw tightening rotation is detected or counted.

  In the constant torque electric driver 10 of the present embodiment, the planetary gear reduction mechanism 16 is a two-stage planetary gear mechanism as shown in FIG. 2 and is provided at the tip of the drive shaft 13 of the electric motor 12. The first stage planetary gear 16a meshes with the pinion gear 13a, and then the support shaft of the disk-like support part 17a that supports the first stage planetary gear 16a is one of the disk-like support parts 17b of the second pinion gear 13b. The planetary gear 16b of the second stage meshes with the second pinion gear 13b, and the support shaft of the disc-like support portion 17b that supports the second planetary gear 16b serves as the planetary gear reduction mechanism 16. Forming the output shaft. The first-stage planetary gear 16 a and the second-stage planetary gear 16 b are meshed with an internal gear 21 that is rotatably supported in the gripping part casing 10 a of the constant torque electric driver 10.

  Therefore, in the present embodiment, the planetary gear speed reduction mechanism 16 having the above-described configuration is provided with a protrusion 21a on a part of the lower end surface of the internal gear 21, and the internal gear 21 is provided to the protrusion 21a. A torsion bar 50 is fixedly disposed on the outer side of the surrounding gripping part casing 10a in parallel with the output shaft (17b) of the planetary gear speed reduction mechanism 16 via an upper support member 51 and an upper support member 52, respectively. .

  The torsion bar 50 is fixed to a part of the casing 10a by an upper support member 52, and a lower support member 53 is set to be rotatable to a part of the casing 10a. Displacement detection arm 54 is arranged in a horizontal direction from the portion, and its front end 54a is passed through opening 56 provided in casing 10a, and is engaged with projection 21a provided on the lower end surface of internal gear 21. (See FIG. 3).

  However, when the internal gear 21 is screwed, in the first screwing process, the drive shaft 13 of the electric motor 12 is rotated to rotate the first stage planetary gear 16a and the second stage planetary gear 16b. Thus, rotational force is applied in the same direction (indicated by a broken line arrow) as the rotation of the drive shaft 13 of the electric motor 12 (see FIG. 3). However, in this case, the projection 21a provided on the lower end surface of the internal gear 21 is engaged with the tip 54a of the displacement detection arm 54. Therefore, as shown in FIG. Rotation with the 16 output shafts (17b) is prevented.

  In the subsequent screw tightening step, when the screw is seated, a reverse load is applied to the driver bit 20 in the direction opposite to the screw tightening rotation direction, and this load torque is equal to or higher than a preset torque (hysteresis torque) preset in the torque limiter 18. Then, the drive rotation part of the torque limiter 18 idles with respect to the driven rotation part. The planetary gear coupled to the drive shaft 13 of the electric motor 12 when the output shaft (17b) of the planetary gear reduction mechanism 16 coupled to the drive rotating portion of the torque limiter 18 starts to idle. A sudden turning force is generated in a direction (indicated by a solid line arrow) in which the internal gear 21 of the speed reduction mechanism 16 is reversed with respect to the rotation of the output shaft (17b), and this turning force is converted into a stress displacement via the displacement detection arm 54. Can be effectively transmitted to the torsion bar 50 (see FIGS. 3 and 4).

  Therefore, in this embodiment, by attaching a pair of strain gauges 28 to the side surfaces of the torsion bar 50, the screw tightening torque at the time when the screw is seated is properly detected in the screw tightening step. Can do.

  Next, a method for detecting the screw tightening torque by the torque detecting device of the constant torque electric screwdriver according to the above-described embodiment will be described.

  At the time of the screw tightening operation, a required screw is attached to the tip of the driver bit 20 of the constant torque electric screwdriver 10, and the drive switch operation signal S14 is controlled by the control unit 30 by the operation of the drive switch 14 operated by the switch operation member 15. To the CPU 32. Therefore, in the control unit 30, when the drive switch operation signal S14 is input to the CPU 32, the electric motor drive control signal S22a is output and input to the electric motor control circuit 22 to control the drive of the electric motor 12 (FIG. 1).

  As the electric motor 12 is driven to rotate, the driver bit 20 is driven to rotate via the planetary gear reduction mechanism 16 and the torque limiter 18. In this case, a rotation count signal S24 corresponding to the rotation amount of the driver bit 20 is detected by the rotary encoder 24 provided in the torque limiter 18 and is input to the CPU 32.

  Next, the screw attached to the driver bit 20 is positioned on a required object to which the screw is attached, and the push bit 26 is actuated by pressing the driver bit 20 against the object to start the screw tightening operation. Thus, the push operation switch detection signal 26 is input to the CPU 32. Therefore, the CPU 32 sets the count start point of the rotation count signal corresponding to the rotation amount of the driver bit 20 detected by the rotary encoder 24 based on the input of the push operation switch detection signal 26, and Detection and recording of the rotation amount of the driver bit 20 is performed.

  In this way, when the required screw tightening operation is performed and the screw is seated on the attachment target, as described above, a reverse load is applied to the driver bit 20 in the direction opposite to the screw tightening rotation direction, When the load torque becomes equal to or higher than a preset torque (hysteresis torque) preset in the torque limiter 18, the drive rotation portion of the torque limiter 18 rotates idly with respect to the driven rotation portion. In this case, the drive rotating portion of the torque limiter 18, that is, the output shaft (17 b) of the planetary gear speed reduction mechanism 16 coupled thereto, is coupled to the drive shaft 13 of the electric motor 12 when starting idling. Rapid turning power is generated in the direction (arrow) in which the internal gear 21 of the planetary gear speed reduction mechanism 16 is reversed with respect to the rotation of the output shaft (17b), and this turning power is converted into stress displacement via the displacement detection arm 54. Effectively transmitted to the torsion bar 50. Then, a screw tightening torque detection signal S28 corresponding to the stress change detected by the strain gauge 28 attached to the torsion bar 50 is input to the CPU 32 and recorded.

  Therefore, if the screw tightening torque input and recorded in the CPU 32 is within the allowable range of the screw tightening torque value set in advance, it is determined that the screw tightening state is appropriate and good, and the required display 40 is displayed. On the other hand, a screw tightening state display signal S40 based on the determination can be output from the CPU 32 and displayed appropriately. Further, the CPU 32 of the control unit 30 outputs an electric motor stop control signal S22b corresponding to the input of the screw tightening torque detection signal S28 and also inputs it to the electric motor control circuit 22 to stop the electric motor 12. Take control.

  In the torque detection method of the present invention, as described above, in the screw tightening operation, the push operation switch 26 is activated, and the push operation switch detection signal S26 is input to the CPU 32 and detected by the rotary encoder 24. The count start point of the rotation count signal corresponding to the rotation amount of the driver bit 20 is set, and the rotation amount of the driver bit 20 is detected and recorded. In this case, if the rotation amount of the driver bit 20 is within an allowable range as compared with a required screw tightening rotation amount set in advance corresponding to the screw to be screwed, it is appropriate as described above. And it can transfer to a good screw tightening state.

  However, if the amount of rotation of the driver bit 20 is outside the allowable range compared to the required amount of screw tightening rotation set in advance corresponding to the screw to be screwed, the screw bite, the screw itself or It is determined that the screw tightening state is defective or defective due to the occurrence of a screw hole defect or the like, and a screw tightening state display signal S40 based on the determination is output from the CPU 32 to the display unit 40 to display appropriately. Can do.

  In the CPU 32 of the control unit 30 described above, when comparing each other with respect to a signal detected and recorded from each component on the constant torque electric screwdriver 10 side, data set in advance in the CPU 32, and the like, By appropriately patterning the signal and data recording and setting processes, the handling and determination processes can be smoothly achieved.

  The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment. For example, when the torque limiter operates exceeding its set torque, the internal gear in the planetary gear reduction mechanism is described. Many design changes can be made without departing from the spirit of the present invention, such as a shape configuration for detecting a stress displacement generated in the strain gauge with a strain gauge.

DESCRIPTION OF SYMBOLS 10 Constant torque electric screwdriver 10a Grasp part casing 12 Electric motor 13 Drive shaft 13a Pinion gear 13b Second pinion gear 14 Drive switch 15 Switch operating member 16 Planetary gear reduction mechanism 16a First stage planetary gear 16b Second stage planetary gear 17a Disk Support 17b Disc support (output shaft)
18 Torque limiter 20 Driver bit 21 Internal gear 22 Electric motor control circuit 24 Rotary encoder 26 Push operation switch 28 Strain gauge 30 Control unit 32 CPU
40 Indicator 50 Torsion Bar 52 Upper Support Member 53 Lower Support Member 54 Displacement Detection Arm 54a Tip 56 Opening S14 Drive Switch Operation Detection Signal S22a Electric Motor Drive Control Signal S22b Electric Motor Stop Control Signal S24 Rotation Amount Detection Signal S26 Push Operation Switch detection signal S28 Screw tightening torque detection signal S40 Screw tightening state detection signal

Claims (8)

The drive rotation part of the torque limiter is coupled to the drive shaft of the electric motor via a planetary gear speed reduction mechanism, and the driven rotation part of the torque limiter is coupled to a driver bit, and screwed based on the set torque of the torque limiter. Use a constant torque electric screwdriver configured to
When the screw is seated by the screw tightening operation, the screw tightening torque by the driver bit exceeds the set torque of the torque limiter, and the drive rotating part of the torque limiter starts idling, and at the same time, coupled to the drive shaft of the electric motor The abrupt rotational force generated in the direction in which the internal gear of the planetary gear speed reduction mechanism is reversed with respect to the rotation of the output shaft is transmitted as stress displacement to the torsion bar, and the stress displacement of the torsion bar is screwed by a strain gauge. A method for detecting screw tightening torque of a constant torque electric screwdriver, characterized by detecting the torque as torque.   The start time of screw tightening by the driver bit is detected by a push operation switch, and then the required screw rotation amount until reaching the screw seat is detected by a rotary encoder provided in the torque limiter, and at the timing of screw seating 2. The method for detecting a tightening torque of a constant torque electric screwdriver according to claim 1, wherein the setting is made so as to detect the stress displacement generated in the internal gear of the planetary gear reduction mechanism.   When the screw tightening start time is detected by the push operation switch, and then the screw rotation amount until the screw is seated by the rotary encoder provided in the torque limiter is detected as the preset screw rotation amount and its allowable range 3. The method for detecting screw tightening torque of a constant torque electric screwdriver according to claim 2, wherein the screw tightening torque is determined by proper screw tightening.   When the screw tightening start time is detected by the push operation switch, and then the screw rotation amount until the screw is seated by the rotary encoder provided in the torque limiter is detected as outside the preset screw rotation amount and its allowable range 3. The method for detecting screw tightening torque of a constant torque electric screwdriver according to claim 2, wherein the screw tightening torque is determined to be due to screw tightening failure. It is set so that stop control of the electric motor is performed when the stress displacement generated in the internal gear of the planetary gear speed reduction mechanism is detected as a screw tightening torque by a strain gauge at the timing when the screw is seated. A method for detecting a screw tightening torque of a constant torque electric screwdriver according to any one of claims 1 to 4 . The drive rotation part of the torque limiter is coupled to the drive shaft of the electric motor via a planetary gear speed reduction mechanism, and the driven rotation part of the torque limiter is coupled to a driver bit, and screwed based on the set torque of the torque limiter. Consists of a constant torque electric screwdriver configured to perform
Providing a projection on a part of the lower end surface of the internal gear, supporting the internal gear holding the planetary gear reduction mechanism coupled to the drive shaft of the electric motor in a rotatable state,
A torsion bar fitted with a strain gauge is provided in parallel with the output shaft of the planetary gear speed reduction mechanism on the outside of the casing surrounding the internal gear with respect to the protrusion, and a displacement detection arm is projected from one end thereof. ,
When the tip of the displacement detection arm is engaged with the protrusion and a screw is seated by a screw tightening operation, the stress displacement of the rotational force that occurs suddenly in the reverse direction from the output shaft of the internal gear is A screw tightening torque detecting device for a constant torque electric screwdriver, wherein the screw tightening torque detecting device is configured to transmit to the torsion bar via the displacement detecting arm.   A torsion bar having a strain gauge provided parallel to the output shaft of the planetary gear speed reduction mechanism on the outside of the casing surrounding the internal gear is fixed at one end by an upper support member and at the other end by a lower support member. A displacement detecting arm is supported in a pivotable manner and is horizontally disposed from a part of the outer periphery of the lower support member, and a tip end of the lower end surface of the internal gear is passed through an opening provided in the casing. The screw torque detecting device for a constant torque electric screwdriver according to claim 6, wherein the screw tightening torque detecting device is configured to engage with a protrusion provided on the screw. A push operation switch that switches according to the axial displacement of the driver bit is provided, and a rotary encoder that detects the rotational displacement is provided on the outer periphery of the torque limiter. The screw tightening torque detecting device for a constant torque electric screwdriver according to claim 6 or 7, wherein the screw rotation amount is detected by the rotary encoder based on the above.

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