JP2012189098A - Feed screw mechanism of electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feed screw mechanism of an electric motor capable of eliminating characteristic reduction in position control of a motor caused by viscosity of oil.SOLUTION: A shaft 32 for constituting the feed screw mechanism 1 of the electric motor is formed of metal, and a male screw 42 is formed on its peripheral surface. An out-fitting part 14 for constituting the feed screw mechanism 1 of the electric motor is formed of resin, and a female screw 43 is formed on its inner peripheral surface. An oil releasing groove 91 extending in the axial direction is arranged on a screw forming surface for forming the male screw 42, and one end of the oil releasing groove 91 is opened on a base end surface 93 of the shaft 32. Thus, a communicating space 101 communicating in the axial direction between the shaft 32 and the out-fitting part 14 is formed of the oil releasing groove 91, and the communicating space 101 is opened on the base end side of the feed screw mechanism 1 of the electric motor via an opening 102 of the base end surface 93.

Description

  The present invention relates to a feed screw mechanism for an electric motor built in a motor.

  Conventionally, a stepping motor is provided with a feed screw mechanism that converts a rotary motion of a rotor into a linear motion (see, for example, Patent Document 1).

  This feed screw mechanism is constituted by a metal male screw and a resin female screw, and a linear expansion coefficient difference due to temperature may occur between the two.

  For this reason, in order to absorb this, a predetermined clearance is secured between the male screw and the female screw.

JP 2007-028861 A

  However, the oil drawn from the screw end portion is stored in the clearance between the male screw and the female screw.

  For this reason, when starting in a low temperature environment, the viscous resistance of the internal oil increases, and the rotation control characteristics deteriorate.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a feed screw mechanism of an electric motor that can eliminate a deterioration in the position control characteristics of a motor due to the viscosity of oil. To do.

  In order to solve the above-mentioned problems, in the feed screw mechanism for an electric motor according to claim 1 of the present invention, a shaft portion having a male screw formed on a peripheral surface, and the male screw screwed in a state of being externally fitted to the shaft portion. A feed screw mechanism of an electric motor that converts a rotational motion into a linear motion, and a screw forming surface of the shaft portion on which the male screw is formed and the outer surface on which the female screw is formed. An oil relief groove extending in the axial direction is provided on at least one of the screw forming surfaces of the fitting portion, and a space that opens in the axial direction and is opened at least on one axial end side while the male screw is screwed to the female screw. An oil relief groove was formed.

  That is, between the male screw and the female screw in a screwed state, a space that communicates in the axial direction and opens at least on one end side in the axial direction is formed by an oil relief groove.

  For this reason, excess oil stored between the male screw and the female screw is guided along the space formed by the oil relief groove when the oil temperature is relatively high and the viscosity is lowered. It is discharged from between.

  Thereby, even in a state where the viscosity of the oil is increased at the time of non-operation where the oil temperature is cooled by the outside air, only a minimum amount of oil is stored between the male screw and the female screw, Excessive load input is prevented.

  Further, in the feed screw mechanism of the electric motor according to claim 2, one of the shaft portion and the outer fitting portion is made of resin and the other is made of metal, and the oil relief groove is formed on the other made of metal. Formed.

  Thereby, when the clearance between both members is set widely in order to eliminate a difference in linear expansion coefficient that may occur between the shaft portion and the outer fitting portion, the above-described saliency of the effect is enhanced.

  Further, since the oil escape groove is formed in a member made of metal among the shaft portion and the outer fitting portion, it is easy to maintain the strength.

  As described above, in the feed screw mechanism of the electric motor according to the first aspect of the present invention, excess oil stored between the male screw and the female screw is removed when the oil temperature is relatively high and the viscosity is lowered. It can be discharged through the space formed by the escape groove.

  As a result, even when the viscosity of the oil is increased during non-operation when the oil temperature is cooled, only a minimum amount of oil remains between the male screw and the female screw. Excessive load input can be avoided.

  Therefore, it is possible to prevent a decrease in the rotation control characteristic at the time of low temperature start accompanying an increase in the viscosity resistance of the oil, and it is possible to eliminate the deterioration in the characteristic of the position control of the motor due to the oil viscosity.

  In addition, in the feed screw mechanism of the electric motor according to claim 2, when the clearance between both members is set wide in order to eliminate the difference in linear expansion coefficient that may occur between the shaft portion and the outer fitting portion, The effect can be made more remarkable.

  Then, by forming the oil relief groove in a member made of metal among the shaft portion and the outer fitting portion, it is possible to easily maintain the strength and maintain a predetermined rigidity.

It is explanatory drawing which shows the 1st Embodiment of this invention. It is an enlarged view which shows the principal part of the embodiment, (a) is an enlarged view which shows 1st Embodiment, (b) is an enlarged view which shows 2nd Embodiment.

  (First embodiment)

  A first embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a stepping motor 2 provided with a feed screw mechanism 1 for an electric motor according to the present embodiment. The stepping motor 2 is disposed inside, for example, an automatic transmission of an automobile, and is automatically changed. Used to control the hydraulic pressure in the aircraft.

  A rotation drive unit 12 is provided in the casing 11 of the stepping motor 2, and the rotation drive unit 12 includes a coil 13 and an outer fitting unit 14 constituting a rotor disposed inside the coil 13. It is comprised by. A connector connecting portion 15 is provided on a side portion of the casing 11, and the coil 13 is connected to an electrode 16 of the connector connecting portion 15.

  The outer fitting portion 14 is rotatably supported by the casing 11 via a front bearing 21 and a rear bearing 22, and a permanent magnet 23 is provided in an intermediate portion thereof. . Thereby, by controlling the signal supplied to the electrode 16 of the connector connecting portion 15, the magnetic force generated from the coil 13 is varied to control the rotation of the outer fitting portion 14 including the permanent magnet 23. It is configured to be able to.

  A hollow portion 31 is formed in the outer fitting portion 14, and a shaft portion 32 constituting an operating shaft is inserted into the hollow portion 31. A front insertion hole 33 through which the shaft portion 32 is inserted is provided at the front end and the rear end of the casing 11, and the shaft portion 32 protrudes from the casing 11 through the front insertion hole 33. It is configured to be able to. Thereby, the stepping motor 2 is configured so that the amount of protrusion of the front end portion of the shaft portion 32 from the casing 11 can be varied.

  A male screw 42 is formed on the peripheral surface of the rear portion side of the shaft portion 32, and a female screw 43 that is screwed with the male screw 42 is formed on the inner surface of the rear end portion of the outer fitting portion 14. . Further, a flat surface portion 44 formed by removing a part of a cylinder is formed on the peripheral surface on the front portion side of the shaft portion 32, and a rotation restricting portion having a D-shaped cross section is formed on the front portion of the shaft portion 32. 45 is formed.

  The front insertion hole 33 through which the front end portion of the shaft portion 32 is inserted is formed with a linear chord portion 51 that is in sliding contact with the flat surface portion 44 of the shaft portion 32, and is adapted to the rotation restricting portion 45. It has a D-shaped cross section.

  Accordingly, the rotation restricting portion 45 of the shaft portion 32 is configured such that the flat portion 44 is slidably engaged with the chord portion 51 of the front insertion hole 33, so that the central shaft 46 of the shaft portion 32 extends. The feed screw mechanism of the electric motor is configured so as to be able to regulate rotation while allowing movement in the present direction, and converts rotational movement from the outer fitting portion 14 into linear movement in the axial direction of the shaft portion 32. 1 is configured.

  Further, a stopper 62 is provided on the front side of the shaft portion 32, and the stopper 62 protrudes sideways. As a result, when the outer fitting portion 14 is rotationally controlled and the shaft portion 32 is moved to the left side in FIG. 1, the shaft portion 32 can be moved until the stopper 62 contacts the front end portion of the casing 11. It is configured as follows.

  FIG. 2A is an enlarged view showing a screwed portion between the shaft portion 32 and the outer fitting portion 14 constituting the feed screw mechanism 1 of the electric motor. In this screwed state, the shaft portion 32 is shown. The external thread 71 is disposed in the internal thread valley 72 of the external fitting portion 14, and the internal thread 73 of the external engagement portion 14 is disposed in the external thread valley 74 of the shaft portion 32. Yes.

  That is, the shaft portion 32 is made of a metal such as SUS, and the male screw 42 is formed on the peripheral surface of the shaft portion 32 by cutting or rolling. On the other hand, the outer fitting portion 14 is made of resin, and the female screw 43 is also formed of resin. Thereby, one of the shaft portion 32 and the outer fitting portion 14 is made of resin, and the other is made of metal.

  A gap 81 is secured between the male screw 42 of the shaft portion 32 and the female screw 43 of the outer fitting portion 14, and a linear expansion coefficient between the male screw 42 made of metal and the female screw 43 made of resin. Even if a difference in expansion occurs due to the difference, it is configured to absorb this.

  An oil relief groove 91 extending in a direction intersecting with the male screw thread 71 is formed by cutting on a peripheral surface constituting a screw forming surface in which the male screw 42 is formed in the shaft portion 32 made of metal, The oil escape groove 91 extends in the axial direction. The depth of the oil relief groove 91 is set to be larger than the height dimension of the male thread 71, and the bottom surface 92 of the oil relief groove 91 is located closer to the center of the shaft portion 32 than the male thread valley 74. Has reached. Further, one end of the oil escape groove 91 reaches the base end of the shaft portion 32, and one end of the oil escape groove 91 is opened on the base end surface 93 of the shaft portion 32.

  As a result, the male screw valleys 74, 74 on both sides defined by the male screw thread 71 in the state where the male screw 42 of the shaft portion 32 is screwed into the female screw 43 of the outer fitting portion 14, the oil relief groove 91. A communication space 101 communicating in the axial direction is formed by the oil relief groove 91 between the shaft portion 32 and the outer fitting portion 14.

  One end of the oil escape groove 91 is open to the base end surface 93, and the communication space 101 formed between the shaft portion 32 and the outer fitting portion 14 is an opening opened to the base end surface 93. It opens to the base end side of the feed screw mechanism 1 of the electric motor via the portion 102.

  In the present embodiment having the above-described configuration, the stepping motor 2 is used, for example, in oil in an automatic transmission of an automobile, and the oil enters the feed screw mechanism 1 of the electric motor.

  At this time, between the male screw 42 of the shaft portion 32 and the female screw 43 of the outer fitting portion 14 in a screwed state, a communication space 101 that communicates in the axial direction and opens to the axial base end side is formed by the oil relief groove 91. Has been.

  For this reason, the excess oil stored between the male screw 42 and the female screw 43 receives the heat from the coil 13 during operation, for example, and has a reduced viscosity, so that the communication space formed by the oil escape groove 91 is formed. 101 is guided to the base end side along 101 and discharged from the base end side of the feed screw mechanism 1 of the electric motor.

  As a result, even when the viscosity of the oil is increased when the oil temperature is cooled by the outside air or the like, only the minimum amount of oil is stored between the male screw 42 and the female screw 43. Therefore, it is possible to avoid an excessive load input when the stepping motor 2 is activated.

  Therefore, it is possible to prevent a decrease in the rotation control characteristic at the time of low temperature start accompanying an increase in the viscosity resistance of the oil, and it is possible to eliminate the deterioration in the position control characteristic of the stepping motor 2 due to the oil viscosity.

  Here, in the present embodiment, the shaft portion 32 is made of metal, while the outer fitting portion 14 is made of resin, and linear expansion that can occur between the shaft portion 32 and the outer fitting portion 14. In order to eliminate the coefficient difference, the gap 81 between both members is set slightly wider. Thereby, since the amount of oil entering the gap 81 is increased, the above-described effects can be made more remarkable.

And since the said oil escape groove | channel 91 was formed in the said axial part 32 comprised with the metal, maintenance of intensity | strength becomes easy and predetermined | prescribed rigidity can be ensured.

  (Second Embodiment)

  FIG. 2B shows the second embodiment. The same or equivalent parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and different parts are attached. Only explained.

  That is, the shaft portion 32 is made of resin, and the resin external thread 42 is formed on the outer peripheral surface of the shaft portion 32. The outer fitting portion 14 is formed of a metal such as SUS, and the female female screw 43 is cut and formed on the inner peripheral surface of the outer fitting portion 14. Thereby, one of the shaft portion 32 and the outer fitting portion 14 is made of resin, and the other is made of metal.

  An oil relief groove 201 extending in a direction intersecting the female screw thread 73 is formed by cutting on an inner peripheral surface constituting a screw forming surface in which the female screw 43 is formed in the metal outer fitting portion 14. The oil relief groove 201 extends in the axial direction. The depth of the oil relief groove 201 is set to be larger than the height dimension of the female thread 73, and the bottom surface 202 of the oil relief groove 201 is located on the outer peripheral side of the outer fitting portion 14 from the female thread valley 72. Has reached. Further, one end of the oil escape groove 201 reaches the base end of the outer fitting portion 14, and one end of the oil escape groove 201 is opened on the base end surface of the outer fit portion 14 (not shown). ).

  As a result, in the state where the male screw 42 of the shaft portion 32 is screwed into the female screw 43 of the outer fitting portion 14, the female screw valleys 72, 72 on both sides defined by the female screw thread 73 can A communication space 211 communicating in the axial direction is formed by the oil relief groove 201 between the shaft portion 32 and the outer fitting portion 14.

  In addition, one end of the oil escape groove 201 is open to the base end surface of the outer fitting portion 14, and the communication space 211 formed between the shaft portion 32 and the outer fitting portion 14 is the outer fitting portion. It opens to the base end side of the feed screw mechanism 1 of the electric motor through an opening portion opened to the base end surface of 14.

  In the present embodiment according to the above configuration, a communication space that communicates in the axial direction and opens to the axial base end side between the male screw 42 of the shaft portion 32 and the female screw 43 of the outer fitting portion 14 in a screwed state. 211 is formed by the oil relief groove 201.

  For this reason, the excess oil stored between the male screw 42 and the female screw 43 receives the heat from the coil 13 during operation, for example, and the viscosity is lowered, so that the communication space formed by the oil relief groove 201 is formed. It is induced | guided | derived to the base end side along 211, and is discharged | emitted from the base end side of the feed screw mechanism 1 of the said electric motor.

  As a result, even when the viscosity of the oil is increased when the oil temperature is cooled by the outside air or the like, only the minimum amount of oil is stored between the male screw 42 and the female screw 43. Therefore, it is possible to avoid an excessive load input when the stepping motor 2 is activated.

  Therefore, it is possible to prevent a decrease in the rotation control characteristic at the time of low temperature start accompanying an increase in the viscosity resistance of the oil, and it is possible to eliminate the deterioration in the position control characteristic of the stepping motor 2 due to the oil viscosity.

  At this time, in the present embodiment, while the shaft portion 32 is made of resin, the outer fitting portion 14 is made of metal, and a wire that can be generated between the shaft portion 32 and the outer fitting portion 14. In order to eliminate the difference in expansion coefficient, the gap 81 between both members is set slightly wider. Thereby, since the amount of oil entering the gap 81 increases, the above-described operational effects can be made more remarkable.

  And since the said oil escape groove | channel 201 was formed in the said external fitting part 14 comprised with the metal, maintenance of intensity | strength becomes easy and predetermined | prescribed rigidity can be ensured.

  In both of the embodiments described above, the best mode in which the oil release grooves 91, 201 are formed on the metal member side has been described. However, the present invention is not limited to this, and the oil member side is made of oil. The problem can be solved even if the relief grooves 91, 201 are formed.

DESCRIPTION OF SYMBOLS 1 Feed screw mechanism of electric motor 2 Stepping motor 14 Outer fitting part 32 Shaft part 42 Male screw 43 Female screw 81 Gap 91 Oil relief groove 101 Communication space 201 Oil relief groove 211 Communication space

Claims (2)

Feeding of an electric motor comprising a shaft portion having a male screw formed on the peripheral surface and an outer fitting portion having a female screw threadedly engaged with the male screw in a state of being fitted on the shaft portion, and converting rotational motion into linear motion In the screw mechanism,
An oil relief groove extending in the axial direction is provided on at least one of the screw forming surface of the shaft portion on which the male screw is formed and the screw forming surface of the outer fitting portion on which the female screw is formed, and the male screw is attached to the female screw. A feed screw mechanism for an electric motor, characterized in that a space that communicates in the axial direction in a screwed state and opens at least on one end side in the axial direction is formed by the oil relief groove.   2. The electric motor according to claim 1, wherein one of the shaft portion and the outer fitting portion is made of resin and the other is made of metal, and the oil relief groove is formed on the other made of metal. Feed screw mechanism.

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