JPH04372550A - Geared motor for measuring instrument - Google Patents

Abstract

PURPOSE:To make an output shaft rotatable only within the scope of the rotational angle less than 360 degrees, by providing a stopper mechanism for suppressing the rotational angle of the output shaft. CONSTITUTION:A motor section 1 comprises a stator unit 3 and a rotor 4, and an end part 5' of a shaft 5 of the rotor 4 is subjected to gear cutting. In a speed changing section 2, the speed of the motor section is changed by intermediate gears 6, 7. A stopper 9 is squeezed in an output shaft 8 and is fastened on it, in order to suppress the rotational angles of an output gear 7 and the output shaft 8. The stopper 9 rotates together with the output shaft 8, but the restriction of its rotational angle is generated by an intermediate shaft 10, and the output shaft is made rotatable within the scope of the rotational angle less than 360 degrees. Thereby, there is no possibility of the output shaft so running away as to turn many times.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a geared motor that houses a motor body inside and rotates an output shaft through a gear train that changes the rotation speed of the motor rotor, and particularly relates to a geared motor that rotates an output shaft through a gear train that changes the rotation speed of the motor rotor. This invention relates to geared motors for instruments that require highly accurate ability to perform delicate control.

0002

2. Description of the Related Art In general, an electric motor using an air core coil without iron core, a so-called crossed coil type air core motor, is generally used as an actuator for instruments. The air core motor uses a magnet in the rotor and is an analog control system that controls the rotation angle of the magnet by energizing multiple air core coils.The output shaft can be adjusted to a minute position by balancing the magnetic field strength of the rotor magnet and the air core coil. It rotates in angle.

0003

[Problems to be Solved by the Invention] When the above-mentioned conventional air core motor is applied to various instruments, it is difficult to perform analog control based on the performance of the air core motor when trying to drive it using signals obtained by detection means such as sensors or processed information. I had no choice but to do it. However, in recent years, with the development of various sensors, signals and information in meters have tended to shift from analog to digital, and it is desired to realize digitally controllable actuators. If a large actuator with a motor diameter of 40 mm to 50 mm is used, it is possible to achieve a rotation angle resolution of about 1 degree, but due to the nature of the instrument, it is difficult to use such a large actuator. Therefore, even smaller and more precise actuators are essential.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a small actuator that can be digitally controlled and whose output shaft rotation angle can be finely controlled as a geared motor for instruments.

[0005]

[Means for Solving the Problems] In order to achieve the above objects, the instrument geared motor of the present invention has one of the following features: a motor body is housed inside and rotational torque is transmitted to an output shaft via a gear train. At the same time, a stopper mechanism is provided to suppress the rotation angle of the output shaft, and two are provided with a configuration that allows the output shaft rotation angle to be maintained by the motor's own detent torque when excitation control of the motor is not required. The present invention is characterized in that it includes a mechanism that applies a predetermined rotational torque to the output shaft in one rotational direction using a spiral spring.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing a first embodiment of a geared motor for instruments according to the present invention. A geared motor for an instrument is comprised of a motor section 1 that generates a driving torque and a transmission section 2 that transmits the driving torque of the motor section 1. The motor section 1 is composed of a stator unit 3 that is supplied with electrical energy from the outside and a rotor 4 that generates rotational torque, and the tip 5' of a shaft 5 that transmits the output torque of the rotor 4 is toothed. . In this embodiment, the transmission section 2 is shifted in two stages by an intermediate gear 6 and an output gear 7. A stopper 9 for suppressing the rotation angle of the output gear 7 and the output shaft 8 is press-fitted and fixed to the output shaft 8.
When the shaft 5 of the rotor 4 rotates forward or backward, rotation of the output shaft is transmitted through the intermediate gear 6 and the output gear 7, and when the stopper 9 rotates together with the output shaft 8, the rotation range of the stopper 9 is The rotation angle of the stopper 9 is restricted by the placed intermediate shaft 10, and the stopper 9
can rotate together with the output gear 9 and output shaft 8 within a rotation angle range of less than 360 degrees. Here, the intermediate shaft 10 is also used as a shaft for supporting the intermediate gear 6, thereby saving space.

[0008] The shaft 5 of the rotor 4 is connected to the lower case 11.
The intermediate shaft 10 is fixed by the intermediate plate 12 and the upper case 13 and rotatably supports the intermediate gear 6, and the output shaft 8 is rotatably supported by the intermediate plate 12 and the upper case 13. Possibly supported.

Referring to the dimensions of this first embodiment, the outer diameter of the stator unit 3 is approximately 15 mm, the outer diameters of the motor section 1 and the transmission section 2 are 20 mm, and the total length of the geared motor is approximately 25 mm. It has become possible to construct a very small instrument actuator. Here, one of the objects of the present invention is
We will explain how to control the small rotation angle. The motor of this embodiment adopts the configuration of a PM type stepping motor, and by applying 20 pulse-like drive signals to the stator unit 3, the rotor 4 is moved at a minute angle (
18 degrees) for a total of 360 degrees. In other words, when a one-pulse drive signal is applied to the stator unit 3, the shaft 5 of the rotor 4 rotates 18 degrees. The tip 5' of the shaft 5 is geared, and the transmission ratio with the intermediate gear 6 is 3.
It's 10 to 10. Further, the transmission ratio between the intermediate gear 6 and the output gear 7 is 5:27, and the transmission ratio is 1:18. Therefore, if a one-pulse drive signal is applied to the stator unit 3, the shaft 5 will rotate by 18 degrees and the output shaft 8 will rotate by one degree, thus achieving the initial objective. If the drive signal of the stator unit 3 is more delicately controlled by microstep drive or the like, the rotation angle of the output shaft 8 will be further divided, and the output shaft 8 will appear to be rotating smoothly.

FIG. 3 is a plan view showing the concept of a conventional air core motor of an instrument actuator.

The rotor 15 is composed of a rotor magnet 16 magnetized to two poles (N pole, S pole) and an output shaft 17, and includes a pair of air core coils A18 and another pair of air core coils B.
By flowing current through the rotor magnet 19 in a well-balanced manner, the rotor magnet 16 rotates by a certain rotation angle and the output shaft 17 is driven. Here, in the conventional air core motor, in order to stably hold the output shaft 17 at a certain rotated position, current must be permanently passed through the air core coil A 18 and the air core coil B 19.
Alternatively, a mechanical holding function was essential. In contrast, in the first embodiment of the geared motor for instruments according to the present invention, when the instrument is moved by a certain rotation angle, if the indicated value of the instrument does not change, even if the stator unit 3 is de-energized, the output shaft remains unchanged. The meter needle (not shown) attached to 8 does not shift to other rotational angle positions, and can continue to provide stable indications. The reason for this is that since a PM type stepping motor is employed in the motor section 1, the output shaft 8 can be stably fixed by the detent torque TDM generated by the PM type stepping motor. Incidentally, the detent torque TDM generated by the motor section 1 in the first embodiment of the present invention is approximately 3
gcm, and the detent torque TD at the output shaft 8 is
Even excluding transmission loss, S is 40 to 45 gcm, and it is clear that even if some external force is applied to the output shaft 8, a constant holding force can be generated.

Furthermore, if an element capable of detecting the position of the stopper 9, such as an optical sensor or a magnetic sensor, is provided in the vicinity where the stopper 9 and the intermediate shaft 10 contact each other (not shown), the position of the stopper 9 can be detected. It is possible to provide an origin recognition function.

FIG. 2 is a longitudinal sectional view showing a second embodiment of the geared motor for instruments according to the present invention.

The basic configuration is the same as that of the first embodiment and consists of a motor section 1 and a transmission section 2. The difference between the first embodiment and the second embodiment lies in the inside of the transmission section 2. Output gear 7 fixed to output shaft 8
In addition to 9 and 9, a spiral spring 14 is added. One end of the inner circumference of the spiral spring 14 is connected to the end 7 of the output gear 7.
', and one end of the outer periphery of the spiral spring 14 is fixed to the intermediate shaft 10. Here, it is necessary to apply a rotational torque TS to the spiral spring 14 in either a coiled or uncoiled state, and furthermore, this rotational torque TS is always one rotation within the rotational angle range in which the output shaft 8 can rotate. It is also necessary to have the ability to apply force in the same direction. Note that the inner periphery of the spiral spring 14 may be fixed to the output shaft 8 or the stopper 9. Further, the outer periphery of the spiral spring 14 may be fixed to the upper case 13 or the middle plate 12. Also, rotational torque TS
When is smaller than the detent torque TDS at the output shaft 8 due to the detent torque TDM generated by the motor section 1, the backlash of each gear train is eliminated, and the rotational torque TS is the detent torque TDS at the output shaft 8.
If it is larger, the stopper will hit the intermediate shaft. Furthermore, the rotational torque TS is the driving torque T of the motor.
If the rotational torque of the output shaft exceeds T1S according to No. 1, it is not suitable for instrument use, so care must be taken.

In the embodiment of the present invention, there are two gears, but the same function can be achieved whether there is one gear or three or more gears. Further, it is more effective to configure the stopper and the spiral spring 14 on the output shaft side after the final gear of the gear change.

[0016]

[Effects of the Invention] By using the instrument geared motor of the present invention as an instrument actuator, the following great effects can be obtained.

■ By providing a stopper in the geared motor for instruments that regulates and suppresses the rotation angle of the rotating output shaft, even if an external force is applied to the instrument, the rotation range of the output shaft will be at least less than 360 degrees. It is within the range of , and there is no runaway that causes it to rotate many times. Furthermore, even if the motor runs out of control, it will continue to rotate until the stopper is activated, and if the position detection function described in the embodiment is not provided, it will be possible to easily return to the origin (or reset to zero).

■In the case of the present invention in which the motor section of the instrument geared motor has a detent torque, when the motor section does not need to be continuously driven, that is, when the instrument pointer does not have to swing, Since the output shaft (pointer) can be held by the detent torque without excitation of the motor, not only does the stator unit generate no heat due to energization, but the life of the power supply is greatly extended, for example, when the stator unit is powered by a battery. Therefore, it is very efficient and effective.

■ The spiral spring in the second embodiment of the present invention can suppress small fluctuations and hysteresis of the instrument pointer in order to eliminate backlash in the gear shift stage, and can also suppress the small fluctuations and hysteresis of the instrument pointer, as well as the rotation at a certain constant speed as described in the embodiment By setting the torque, it is possible to always return to the origin when the power is not energized, which is particularly effective as a return method in emergencies and abnormalities. In addition, applying grease, examining the material of the gear, and changing the shape of the teeth are effective methods for suppressing the noise caused by the gear transmission, but the present invention, which uses a spiral spring to constantly contact the tooth surface, further enhances the noise reduction effect.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a geared motor for instruments according to the present invention.

FIG. 2 is a longitudinal sectional view showing a second embodiment of the instrument geared motor of the present invention.

FIG. 3 is a plan view showing the concept of a conventional instrument actuator.

[Explanation of symbols]

1 Motor part 2　　　　Transmission section 3 Stator unit 4 Rotor 5 Shaft 6 Intermediate gear 7 Output gear 8 Output shaft 9 Stopper 10 Intermediate shaft 11 Lower case 12 Middle plate 13 Upper case 14 Spiral spring 15 Rotor 16 Rotor magnet 17 Output shaft 18 Air core coil A 19 Air core coil B

Claims (3)

[Claims] Claim 1: A motor that serves as a power source, an output gear that rotates an output shaft from the motor shaft via a gear train, and a stopper mechanism that makes the rotation angle at which the output shaft can move backwards less than 360 degrees. A geared motor for instruments that is characterized by: 2. The geared motor for instruments according to claim 1, further comprising a structure capable of generating detent torque that opposes load torque even when the motor serving as the power source is not excited. [Claim 3] A spiral spring that engages with the output shaft or a part or plurality of the output gear or stopper mechanism integrated with the output shaft is provided, and the spiral spring applies a predetermined rotational torque in one rotation direction of the output shaft. The geared motor for instruments according to claim 2, further comprising a mechanism for.