JP4403593B2 - Electric motor with reduction gear - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor with a reduction gear provided with a rotation sensor that detects a rotational displacement of an output shaft.
[0002]
[Prior art]
An electric motor with a reduction gear provided with a rotation sensor is used for operating an operation unit in various control devices, for example. For example, in a control device for an internal combustion engine, an electric motor with a reduction gear provided with a rotation sensor is used as an actuator for operating means for adjusting the amount of fuel supplied to the internal combustion engine (a control rack of a throttle valve or a fuel pump).
[0003]
In addition, in a load driven by a motor through a speed reducer, when it is necessary to control the load position to coincide with the target position, the output shaft of the motor with a speed reducer is used to detect the position of the load. In some cases, a rotation sensor for detecting the rotation angle is provided.
[0004]
FIG. 3 shows a conventional electric motor with a reduction gear (utility model registration No. 3001320) equipped with a rotation sensor for detecting the rotation angle of the output shaft. In FIG. 3, reference numeral 1 denotes a first case half 1A and Case 2 divided into second case half 1B, 2 is a load driving speed reduction mechanism housed in case 1, 3 is supported by case 1 and coupled to the output of speed reduction mechanism 2 The output shaft, and the case 1, the speed reduction mechanism 2, and the output shaft 3 constitute a speed reducer 4 for driving a load. Reference numeral 5 denotes an electric motor attached to the second case half 1 </ b> B, and its rotating shaft 5 a is introduced into the case 1.
[0005]
The load driving speed reduction mechanism 2 transmits the rotation of the electric motor to the output shaft 3 after being reduced by the gears 2a to 2h. The gear 2a constituting the input portion of the speed reduction mechanism is provided on the rotation shaft 5a of the electric motor. Yes. The output shaft 3 is rotatably supported by the second case half 1B via a bearing, and a gear 2h constituting an output portion of the speed reduction mechanism 2 is attached to the output shaft 3. One end 3a connected to the load of the output shaft 3 is led out from the second case half 1B.
[0006]
A rotation sensor 6 is attached to a frame 9A fixed to the first case half 1A. The rotation sensor 6 includes a sensor input shaft 6A and a signal generator 6B that outputs a detection signal including information on the rotation angle of the input shaft, and includes, for example, a potentiometer, a differential transformer, a rotary encoder, and the like. Yes. In this example, the rotation sensor 6 is configured as an endless type, and a detection signal corresponding to the rotation angle of 360 degrees of the sensor input shaft 6A is output.
[0007]
The rotation sensor 6 is arranged on the extension of the rotation shaft 2i of the gear 2g in the preceding stage of the gear 2h attached to the output shaft 3, and a planetary gear mechanism is formed between the sensor input shaft 6A and the rotation shaft 2i. The sensor drive speed reducer 7 and the coupling 8 are connected to each other. A protective cover 9B that covers the speed reducer 7, the coupling 8, and the rotation sensor 6 is attached to the first case half 1A, and an output lead wire of the rotation sensor 6 is a hole provided through the protective cover 9B. It is led out through a grommet (not shown) attached to the outside.
[0008]
In this example, an output is provided by a gear transmission mechanism that transmits the rotation of the output shaft of the electric motor 5 to the rotation shaft 2 i and the sensor drive speed reducer 7 provided between the rotation shaft 2 i and the input shaft of the rotation sensor 6. A sensor drive mechanism is configured to transmit the rotation of the electric motor 5 to the sensor input shaft 6A so as to rotate the sensor input shaft 6A of the rotation sensor at a rotational speed proportional to the rotational speed of the shaft 3.
[0009]
In the electric motor with a reduction gear, the rotation of the electric motor 5 is transmitted to the output shaft 3 through the reduction mechanism 2, and a load (not shown) is driven by the rotation of the output shaft 3. The rotation of the electric motor 5 is also transmitted to the input shaft of the rotation sensor 6 through a gear constituting a part of the load driving speed reduction mechanism 2 and the sensor driving speed reducer 7, and the sensor input shaft 6 A is connected to the output shaft 3. Is rotated at a reduction ratio of 10 to 1 with respect to the rotation of the motor. At this time, the signal generator 6B can detect the rotation angle (3600 degrees) of the output shaft 3 over 10 rotations. When the rotation of the motor is transmitted to the sensor input shaft 6A so that the sensor input shaft is rotated at a rotational speed obtained by reducing the rotation of the output shaft by a predetermined reduction ratio, the reduction ratio is appropriately selected. Thus, the detectable rotation angle range can be arbitrarily set.
[0010]
[Problems to be solved by the invention]
In a conventional motor with a speed reducer, the output shaft 3 of the speed reducer is connected via a gear drive 2h, 2g, 2f constituting a part of the speed reduction mechanism 2 and a sensor drive speed reducer 7 and a coupling 8 comprising a planetary gear mechanism. Thus, the rotation sensor 6 is connected to the input shaft 6A. A reduction mechanism using a planetary gear is composed of many gears, and the backlash of the gear generated by the planetary gear mechanism becomes very large. Therefore, the rotation shaft 2i of the load drive reduction mechanism and the input shaft of the rotation sensor If the planetary gear mechanism is interposed between the rotary shaft 6A and the rotational shaft, the rotational displacement of the output shaft and the rotational displacement of the input shaft of the rotation sensor do not correspond accurately, and there is a problem that the detection error increases. For example, when the sensor drive speed reducer 7 including a planetary gear mechanism is configured to rotate the input shaft of the rotation sensor at a reduction ratio of 25: 1 with respect to the rotation of the rotation shaft 2i of the load drive speed reduction mechanism, It has been shown that backlash as high as 30 degrees occurs.
[0011]
In addition, when the rotation of the load drive speed reduction mechanism is transmitted to the input shaft of the rotation sensor via the reduction gear using the planetary gear mechanism, the output of the rotation sensor is caused by gear backlash generated in the planetary gear mechanism. There is a problem that a large hysteresis occurs in the output characteristics of the sensor that gives the relationship between the rotation speed of the output shaft of the reduction gear.
[0012]
FIG. 4 shows a state in which hysteresis occurs in the output characteristics of the rotation sensor 6. In the figure, the horizontal axis indicates the rotation angle of the output shaft 3 of the speed reducer, and the vertical axis is obtained from the rotation sensor 6. The output voltage is shown. In this example, it is assumed that the rotation sensor 6 is a potentiometer, and the voltage obtained between the output terminals of the potentiometer when a constant voltage is applied to both ends of the potentiometer resistor is used as the output voltage of the rotation sensor 6. Yes.
[0013]
The straight lines a, b, and c in FIG. 4 are characteristic straight lines that give a relationship between the output voltage of the rotation sensor 6 and the rotation angle of the output shaft 3, and the rotation sensor when the output shaft 3 of the speed reducer is rotated in one direction. 6 rises along the straight line a from the origin O of FIG. 4, and when the rotation angle of the output shaft 3 reaches 360 degrees, the output voltage reaches V1. When the output shaft 3 is rotated 360 degrees in one direction and then rotated in the reverse direction, the rotation of the output shaft 3 is not transmitted to the input shaft of the rotation sensor 6 due to the backlash of the gear first, so that the output shaft 3 is reversed. During the Δθ rotation in the direction, the output voltage of the rotation sensor 6 is kept constant as shown by the straight line b in FIG.
[0014]
In the range in which the rotation angle of the output shaft 3 in the reverse direction exceeds Δθ, the output voltage of the rotation sensor decreases along the straight line c as the output shaft 3 rotates, and the rotation angle position of the output shaft 3 is the origin. The output voltage of the rotational displacement sensor 6 becomes 0 when the O ′ point shown in FIG. In this way, if there are many gears between the output shaft of the reduction gear and the input shaft of the rotation sensor, a large hysteresis occurs due to the backlash of the gears. Therefore, when the output shaft is rotated in one direction There is a difference in the output of the rotation sensor between the rotation in the other direction and the problem that the rotational displacement of the output shaft cannot be detected accurately.
[0015]
Further, conventionally, since the coupling 8 is required between the rotation sensor 6 and the sensor driving speed reducer 7, the dimension in the axial direction of the portion where the rotation sensor and the sensor driving speed reducer are provided becomes longer, and the rotation sensor portion is In addition to increasing the size, it was inevitable that the number of parts would increase and the cost would increase.
[0016]
An object of the present invention is to provide an electric motor with a speed reducer that can reduce the number of parts, reduce gear backlash, and detect the angle of the output shaft with higher accuracy than before. .
[0017]
Another object of the present invention is to provide an electric motor with a speed reducer that can reduce hysteresis generated between an output voltage of a rotation sensor and a rotation angle of an output shaft for driving a load.
[0018]
Still another object of the present invention is to provide an electric motor with a reduction gear that can reduce the number of components and reduce the assembly cost.
[0019]
Still another object of the present invention is to provide an electric motor with a speed reducer that prevents an increase in size of a portion where a rotation sensor and a sensor driving speed reducer are provided.
[0020]
[Means for Solving the Problems]
The present invention relates to a load drive speed reducer in which a load drive speed reduction mechanism in which one end of an output shaft is connected to a load is housed in a case, and an input portion of the load drive speed reduction mechanism attached to the case. A rotation sensor that has a sensor input shaft to which rotational displacement is applied and generates a detection signal corresponding to the rotation angle of the sensor input shaft, and rotates at a rotational speed proportional to the rotational speed of the output shaft A sensor drive mechanism for transmitting the rotation of the electric motor to the sensor input shaft so as to rotate the sensor input shaft of the sensor, and obtaining a detection signal corresponding to the rotation angle of the output shaft of the load drive deceleration mechanism from the rotation sensor This is related to a motor with a machine.
[0021]
In the present invention, the rotation sensor is fixed to the case in a state where the sensor input shaft is disposed in parallel with the output shaft of the load driving speed reduction mechanism.
[0022]
The sensor drive mechanism is attached to the output shaft of the load drive speed reduction mechanism or a pinion gear provided on the rotation shaft of the load drive speed reduction mechanism located on the upstream side of the output shaft, and the sensor input shaft of the rotation sensor. The spur gear and the pinion gear are engaged with each other directly or via another gear.
[0023]
In a preferred aspect of the present invention, the rotation sensor has the sensor input shaft arranged in parallel to the output shaft of the load driving speed reduction mechanism, and the same direction as the direction in which the other end of the output shaft faces the tip of the sensor input shaft It is fixed to the case in the state of
[0024]
The rotation sensor outputs a detection signal corresponding to the rotation angle of the sensor input shaft. This type of sensor uses a change in resistance value such as a potentiometer, or an inductance such as a differential transformer. There are analog sensors such as those using the change of the sensor, and digital sensors such as a rotary encoder that generates a pulse at every minute rotation angle. The rotation sensor used in the present invention may be any of these types. . Which type of rotation sensor is used is determined according to the use of the actuator and the configuration of the control device that inputs the output signal. The detection signal output from the rotation sensor may be an electrical signal (voltage, current, resistance value, reactance value, etc.) or an optical signal.
[0025]
As described above, a pinion gear is provided on the rotation shaft of the load driving speed reduction mechanism, and a spur gear is attached to the input shaft of the rotation sensor so that the pinion gear and the spur gear are engaged directly or via another gear. Then, since many backlashes do not occur as in the case of using a planetary gear mechanism, the angle of the output shaft can be detected with high accuracy.
[0026]
Further, if configured as described above, gear backlash generated in the gear transmission system existing between the output shaft and the input shaft of the rotation sensor can be reduced, so that the output of the rotation sensor and the load drive speed reduction mechanism can be reduced. Hysteresis generated between the rotation angle of the output shaft and the rotation angle of the output shaft can be reduced to increase the detection accuracy of the rotation angle of the output shaft.
[0027]
Further, if configured as described above, it is not necessary to interpose a coupling between the input shaft of the rotation sensor and the rotation shaft of the load driving speed reduction mechanism, so that the axial dimension of the rotation sensor portion is prevented from increasing. Further, the rotation sensor unit can be reduced in size, and the cost can be reduced by reducing the number of parts and the number of assembly steps.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the present invention, in which 11 is a case that is divided into two parts, a first case half 11A and a second case half 11B. The second case halves 11A and 11B are fastened to each other by through bolts 11C in a state where the respective openings are abutted.
[0029]
The case 11 houses a load driving speed reduction mechanism 12 including a gear speed reduction mechanism including gears 12a to 12h. The output shaft 13 of the speed reduction mechanism 12 is supported by the first case half 11A and the second case half 11B via bearings 14 and 14 ', respectively, and one end 13a connected to the load of the output shaft 13 is The second case half part 11B is led out to the outside through a hole 11B2 provided in the bottom wall part 11B1. The case 11, the gear reduction mechanism 12, and the output shaft 13 constitute a load drive reduction gear 15.
[0030]
The electric motor 16 is attached to the first case half 11 </ b> A, and a gear 12 </ b> A constituting the input portion of the speed reduction mechanism 12 is directly carved at the tip of the rotating shaft 16 a of the electric motor 16 inserted into the case 11. A cylindrical projection 11A1 is formed integrally with the case half 11A, and the other end of the output shaft 13 of the speed reduction mechanism 12 is introduced into a space formed inside the projection 11A1.
[0031]
A rotation sensor 17 is disposed in a space inside the cylindrical protrusion 11A1. The rotation sensor 17 includes a sensor main body 17a and a first end of the sensor main body 17a. The sensor main body 17a includes a substrate holding a resistor having a circular pattern and a sliding contact sliding on the resistor in a cylindrical case. And a sensor input shaft 17c which is supported in a state of being rotatably penetrated through a tubular neck portion 17b and is connected to the sliding contact in the main body 17a, and an endless potentiometer. . The rotation axis of the rotation sensor 17 can be rotated 360 degrees in both directions, and the resistance value between the contact point and one end of the resistor returns to zero when the sensor input shaft 17c rotates once. .
[0032]
In the illustrated example, in order to hold the rotation sensor 17, a sensor plate 18 integrally including a bottomed shallow cylindrical portion 18a and a flange plate portion 18b protruding radially outward from the outer peripheral portion of the cylindrical portion 18a. Is provided. The rotation sensor 17 is arranged in a state in which the neck portion 17b is fitted in a hole formed in the center of the bottom portion of the cylindrical portion 18a of the sensor plate 18, and a screw provided on the outer periphery of the neck portion 17b in the cylindrical portion 18a. The sensor plate 18 is fastened to the main body 17a of the rotation sensor 17 by a nut 18c screwed to the rotation sensor 17.
[0033]
The sensor plate 18 holding the rotation sensor 17 is inserted inside the protruding portion 11A1 provided in the first case half 11A, and the collar plate portion 18b is provided inside the protruding portion 11A1. The sensor mounting portion 19 is fastened to the sensor mounting portion 19 by a screw 20. With the sensor plate 18 fixed to the sensor mounting portion 19 in this way, the sensor input shaft 17c of the rotation sensor 17 is parallel to the output shaft 13 of the load driving speed reducer , and the tip of the sensor input shaft 17c is the output shaft. It arrange | positions in the state which faced the same direction as the direction where the other end of 13 is directed . The sensor plate 18 collar plate portion axial through hole 18a is formed, the side of the sensor input shaft 17c of the rotation sensor 17 in a state where the other end of the output shaft 13 of the load driving speed reducer penetrates loosely axial through hole 18a It is arranged in the direction.
[0034]
A spur gear 23 </ b> A is attached to the sensor input shaft 17 c of the rotation sensor 17. The illustrated spur gear 23 </ b> A has a boss portion 23 </ b> A <b> 1, a hole having a D-shaped section is formed inside the boss portion, and a D-shaped section formed on the sensor input shaft 17 c of the rotation sensor 17. Is fitted into the inner hole of the boss portion 23A1, and the spur gear 23A and the sensor input shaft 17c are coupled in a state in which no relative rotation occurs between them. The boss portion of the spur gear 23A is also provided with a screw hole penetrating the boss portion in the radial direction, and the spur gear 23A is fixed to the sensor input shaft 17c of the rotation sensor by a screw 24 screwed into the screw hole. Has been.
[0035]
On the outer periphery of the other end of the output shaft 13 loosely passing through the shaft through hole provided in the collar plate portion of the sensor plate 18, a pinion gear 23B constituting the input portion of the sensor drive speed reducer is engraved. The gear 23B is meshed with the spur gear 23A. The pinion gear 23B and the spur gear 23A constitute a sensor driving speed reducer 23, and the load driving speed reducing mechanism 12 and the sensor driving speed reducer 23 have a rotation sensor at a rotational speed proportional to the rotational speed of the output shaft 13. A sensor drive mechanism that transmits the rotation of the electric motor 16 to the sensor input shaft 17c is configured to rotate the 17 sensor input shafts 17c. The opening of the protrusion 11A1 is closed by a cover plate 26 fixed to the opening end of the protrusion 11A1 by a screw 25.
[0036]
In the example shown in FIG. 1, the rotational displacement detector 27 is configured by the sensor driving speed reducer 23 and the rotation sensor 17.
[0037]
If comprised as mentioned above, since it is not necessary to arrange | position many components between the output shaft 13 and the rotation sensor 17 of the reduction gear for a load drive, the number of components can be reduced. Further, since the number of gears interposed between the output shaft 13 and the rotation sensor 17 can be reduced, the backlash of the gears can be reduced and the angle of the output shaft can be detected with high accuracy.
[0038]
Further, since the backlash of the gear can be reduced when configured as described above, the hysteresis generated between the output of the rotation sensor 17 and the rotation angle of the output shaft 13 of the load drive speed reducer is reduced, and the output is reduced. The detection accuracy of the rotation angle of the shaft can be increased.
[0039]
Furthermore, if comprised as mentioned above, since the number of conventional reduction gear parts shown in FIG. 3 can be reduced and an assembly man-hour can be reduced, cost reduction can be aimed at.
[0040]
Further, if configured as described above, the reduction gear for driving the sensor can be directly coupled to the rotation sensor, so there is no need to provide a coupling between the rotation sensor and the reduction gear for driving the sensor. Therefore, it is possible to prevent the portion where the rotation sensor and the sensor driving speed reducer are provided from becoming large.
[0041]
FIG. 2 shows a main part of another configuration example of the electric motor with a reduction gear according to the present invention. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals. In the example shown in FIG. 2, the tip of the rotating shaft 12g of the load driving speed reduction mechanism 15 that is one stage before the output shaft 13 (not shown in FIG. 2) of the load driving speed reduction mechanism is the rotation sensor side. The pinion gear 23B is provided at the tip of the rotary shaft 12g. In this example, the spur gear 23A attached to the input shaft 17c of the sensor 17 is the same as that used in the example of FIG. 1, and the boss 23A1 of the spur gear 23A is directed to the sensor 17 side. ing. In the example shown in FIG. 2, a shaft 30 extending in parallel with the input shaft 17c of the rotation sensor is fixed to the sensor plate 18 between the pinion gear 23B and the spur gear 23A, and the intermediate gear 23C is attached to the shaft 30. It is attached. The intermediate gear 23C integrally includes a large gear 23C1 and a small gear 23C2, and is attached to the shaft 30 with the large gear 23C1 positioned on the rotation sensor 17 side. The large gear 23C1 is attached to the pinion gear 23B. The small gears 23C2 are meshed with the spur gears 23A, respectively.
[0042]
As shown in FIG. 2, when the intermediate gear 23C is interposed between the spur gear 23A and the pinion gear 23B, the reduction ratio of the sensor input shaft 17c of the rotation sensor 17 with respect to the rotation of the output shaft 13 can be increased. The rotation angle range that can be detected by the rotation sensor 17 can be expanded.
[0043]
Further, as described above, if the direction of the spur gear 23A is reversed as required, the sensor driving speed reducer is configured by the two gears 23A and 23B and the three gears 23A to 23C. In this case, the same spur gear can be shared, so that the types of gears to be prepared can be reduced to reduce costs.
[0044]
In the example shown in FIG. 2, the configuration of other parts is the same as that of the example shown in FIG.
[0045]
【The invention's effect】
As described above, according to the present invention, the pinion gear is provided on the rotation shaft of the load driving speed reduction mechanism, and the spur gear is attached to the input shaft of the rotation sensor so that the pinion gear and the spur gear can be directly connected to each other or another gear. Therefore, it is possible to prevent the occurrence of many backlashes as in the case of using a planetary gear mechanism, and to detect the angle of the output shaft with high accuracy.
[0046]
Further, according to the present invention, it is possible to reduce gear backlash generated in the gear transmission system existing between the output shaft and the sensor input shaft of the rotation sensor. Hysteresis generated between the rotation angle of the output shaft and the rotation angle of the output shaft can be reduced to increase the detection accuracy of the rotation angle of the output shaft.
[0047]
Furthermore, according to the present invention, since it is not necessary to interpose a coupling between the sensor input shaft of the rotation sensor and the rotation shaft of the load driving speed reduction mechanism, it is possible to prevent the axial dimension of the rotation sensor portion from increasing. In addition to reducing the size of the rotation sensor unit, it is possible to reduce costs by reducing the number of parts and the number of assembly steps.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a configuration example of an electric motor with a reduction gear according to the present invention.
FIG. 2 is a longitudinal sectional view showing only a main part of another configuration example of the electric motor with a reduction gear according to the present invention.
FIG. 3 is a longitudinal sectional view showing a conventional example.
FIG. 4 is a diagram for explaining hysteresis that occurs between an output voltage of a rotation sensor and a rotation angle of a load driving output shaft in a conventional electric motor with a reduction gear.
[Explanation of symbols]
13 Output shaft 17 Rotation sensor 17c Input shaft 18 Sensor plate 23A Spur gear 23B Pinion gear 23C Intermediate gear

Claims (3)

A load drive speed reducer in which a load drive speed reduction mechanism having one end of an output shaft connected to a load is housed in a case, and a rotary shaft attached to the case coupled to an input portion of the load drive speed reduction mechanism A rotation sensor that has a sensor input shaft to which rotational displacement is applied and generates a detection signal corresponding to the rotation angle of the sensor input shaft, and the rotation at a rotation speed proportional to the rotation speed of the output shaft. A sensor drive mechanism for transmitting the rotation of the electric motor to the sensor input shaft so as to rotate the sensor input shaft of the sensor, and detection corresponding to the rotation angle of the output shaft of the load driving deceleration mechanism from the rotation sensor In a motor with a speed reducer that obtains a signal,
The rotation sensor is fixed to the case in a state where the sensor input shaft is arranged in parallel with the output shaft of the load driving speed reduction mechanism,
The sensor drive mechanism includes an output shaft of the load drive speed reduction mechanism or a pinion gear provided on a rotation shaft of the load drive speed reduction mechanism located on the upstream side of the output shaft, and a sensor input shaft of the rotation sensor And a spur gear attached to the pinion gear, wherein the spur gear and the pinion gear are meshed directly or via another gear. A load drive speed reducer in which a load drive speed reduction mechanism having one end of an output shaft connected to a load is housed in a case, and a rotary shaft attached to the case coupled to an input portion of the load drive speed reduction mechanism A rotation sensor that has a sensor input shaft to which rotational displacement is applied and generates a detection signal corresponding to the rotation angle of the sensor input shaft, and the rotation at a rotation speed proportional to the rotation speed of the output shaft. A sensor drive mechanism for transmitting the rotation of the electric motor to the sensor input shaft so as to rotate the sensor input shaft of the sensor, and detection corresponding to the rotation angle of the output shaft of the load driving deceleration mechanism from the rotation sensor In a motor with a speed reducer that obtains a signal,
The rotation sensor has the sensor input shaft arranged in parallel with the output shaft of the load driving speed reduction mechanism, and the tip of the sensor input shaft is oriented in the same direction as the direction of the other end of the output shaft. Fixed to the case
The sensor drive mechanism includes an output shaft of the load drive speed reduction mechanism or a pinion gear provided on a rotation shaft of the load drive speed reduction mechanism located on the upstream side of the output shaft, and a sensor input shaft of the rotation sensor And a spur gear attached to the pinion gear, wherein the spur gear and the pinion gear are meshed directly or via another gear.   The electric motor with a reduction gear according to claim 1 or 2, wherein the rotation sensor is an endless sensor that outputs a detection signal corresponding to a rotation angle over a rotation range of 360 degrees of the sensor input shaft.

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