JPH0318421B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a motor as a rotational drive member, and in particular, a hollow motor with a ball screw that is useful when performing fine movement and rapid traverse motion by adding a ball screw. Regarding shaft motors.

[Prior Art] Generally, a conventional motor has a rotating shaft that rotates at a predetermined number of rotations, but this rotating shaft is not designed to move forward and backward along the axial direction. Therefore, in order to appropriately move the moving member forward and backward using this type of motor, it is necessary to convert the rotational motion of the motor into linear reciprocating motion of the moving member, for example by using a ball screw unit. Become.

In a conventional ball screw unit, for example, as shown in FIG. 3, a nut 2 is screwed onto a ball screw shaft 1 through a large number of balls 3.
is pivotally supported as a frame by a pair of bearing members 4,
There is one in which a fixing flange 6 is formed on the outer ring 5 of one of the bearing members 4, and a gear 7 for transmitting rotational force is formed on one side of the outer peripheral surface of the nut 2. Therefore, by using this ball screw unit, it is possible to construct a moving table device as shown in FIG. In the figure, the movable table device includes a movable table 12 mounted on a fixed base 11.
are arranged so as to be movable forward and backward via a guide mechanism (not shown), and both end portions of the ball screw shaft 1 are fixed to a fixed base 11.
This ball screw shaft 1 is supported by the upper bearing member 13.
One end side is connected to the shaft of one drive motor 14, and the other drive motor 15 is fixedly installed on the movable table 12 side, and the shaft of this drive motor 15 and the gear 7 of the nut 2 are connected to a transmission gear. 16.

According to this type, each of the drive motors 14,
15 rotation speed and rotation direction as appropriate.
The movable table 12 can be moved slightly or rapidly.

[Problems to be Solved by the Invention] However, in such conventional movable table devices, the rotation center of the nut 2 of the ball screw unit and the rotation center of the drive motor 15 are offset from each other. Therefore, in the process of transmitting the rotational force from the drive motor 15 to the nut 2, the rotational accuracy of the nut 2 will vary due to play in the gear 7, etc., and the rotational movement of the nut 2 will become unstable. It tends to be stable. in this case,
This makes it difficult to accurately feed the movable table 12, resulting in the problem that fine movement and rapid feed cannot be performed with high accuracy.

In order to solve such problems, for example, the fifth
As shown in the figure, the shaft 15a of one drive motor 15 is formed into a hollow shape, and this shaft 15a
The end portion is coupled to one side end of the nut 2, and the hollow portion 15b of the shaft 15a
It is conceivable that the ball screw shaft 1 is disposed penetrating therein. However, even with this type, there is a risk of misalignment when connecting the shaft 15a and the nut 2, so it is not only insufficient as a means for performing fine movement and rapid forwarding with high precision, but also only this type. However, even in the case of the above-mentioned device, since a ball screw unit must be used separately in addition to the pair of drive motors 14 and 15, the basic problem is that the cost of the device inevitably increases as the number of parts increases. have.

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and is capable of performing fine movement and rapid traverse motion of a moving member with high precision without using a separate ball screw unit. The present invention provides a hollow shaft motor with a ball screw that can be used for various purposes.

That is, the hollow shaft motor with a ball screw according to the present invention includes a motor housing, a stator core provided in the motor housing, a rotor core rotatably arranged with respect to the stator core, and a rotor core mounted inside the rotor core. a nut member that constitutes a part of the motor shaft, is rotatably supported by the motor housing via angular contact bearings provided at both ends thereof, and rotates in accordance with the rotation of the rotor core; A ball screw shaft member that penetrates through the member and constitutes a part of the motor shaft, is screwed into the nut member via a number of balls, and has a connecting portion at least one end thereof to be connected to another rotational drive member. The pair of angular contact bearings are provided with a ball raceway surface recessed at both ends of the outer peripheral surface of the nut member, a ball disposed in contact with the ball raceway surface along the ball raceway surface, and a ball raceway contacting the motor housing. It is characterized in that it is configured with an outer ring which is fixed to the nut member and forms an opposing ball rolling surface that holds the ball so that it can roll along with the ball rolling surface of the nut member.

In such technical means, the motor to be applied may be a step motor, a servo motor, etc. as appropriate. Although the basic structure of the motor may be modified as appropriate, in order to maintain good rotational accuracy of the shaft portion of the motor, the nut member should be supported with an angular contact bearing relative to the motor housing.
It is necessary to design the nut member so that it can support thrust and radial loads acting on the nut member. In order to ensure coaxiality between the nut member and the ball screw shaft member, this angular contact bearing omitted the inner ring and formed the ball rolling surface directly on the outer peripheral surface of the nut member. A type with an omitted inner ring is used.
Furthermore, the design of the connecting portion formed at the end of the ball screw shaft may be changed as appropriate as long as it can be directly connected to another rotational drive member.

[Operation] According to the above-mentioned technical means, the motor has a nut member that rotates together with the rotor core, and the motor shaft is constituted by this nut member and a ball screw shaft member that is threadedly engaged with the nut member. Since the motor shaft itself can function as a ball screw unit, there is no need to connect a separate ball screw unit to the motor.

Furthermore, since the nut member is installed to the motor housing via an angular contact bearing, the thrust and radial loads acting on the nut member are reliably supported, and the nut member and ball screw shaft member Not only is the motor shaft consisting of
Since the nut member is inserted and locked into the rotor core, and the ball screw shaft member is inserted into this nut member, there is little risk that the nut member and the ball screw shaft member will be misaligned, and the coaxiality of both is almost non-existent. Well kept.

In particular, in the present invention, since the ball rolling surface between the ball screw shaft member and the ball rolling surface of the bearing can be coaxially formed on the inner peripheral surface and the outer peripheral surface of the nut member, The coaxiality between the ball screw shaft member and the nut member is provided with high precision.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the accompanying drawings.

In the embodiment shown in FIG. 1, the basic configuration of the drive motor (hollow shaft motor with ball screw) M is that a motor housing 20 is composed of a yoke 21 and a motor side plate 22, and the inner peripheral surface of the yoke 21 is While the magnet 23 is disposed, a stator core 24 is disposed inside the magnet 23, and a rotor core 25 is disposed inside the stator core 24, and a motor shaft 30 having a ball screw function is fixedly attached to the rotor core 25. It is something that has been established.

In this embodiment, the rotor core 25 has an insertion hole 26 for the motor shaft 30,
The motor shaft 30 includes a ball screw shaft member 3
1 and a nut member 33 screwed together via a large number of balls 32. Then, a portion of the outer peripheral surface of the nut member 33 excluding both ends is inserted and locked into the insertion hole 26 of the rotor core 25, and both ends of the outer peripheral surface of the nut member 33 are connected to the motor via a pair of angular contact bearings 34. Shaft 20
It is rotatably supported by the side plate 22 portion of. and,
The angular contact bearing 34 includes a ball raceway surface 35 recessed at both ends of the outer peripheral surface of the nut member 33, a ball 36 disposed in contact with the ball raceway surface 35, and a motor housing 20.
The ball 36 is fixed in contact with the presser projection piece 22a on the side plate 22 of the
The bearing 34 is comprised of an outer ring 37 that rotatably holds the nut member 33.
The nut member 33 is designed to support thrust and radial loads acting on the nut member 33, and to maintain good rotational accuracy of the nut member 33.

Further, on one end side of the ball screw shaft member 31, there is formed a connecting shaft portion 40 which is inserted and locked into a recess of a coupling coupling (not shown) as a connecting portion with another drive motor M'. There is.

Therefore, if the motor according to this embodiment is used,
For example, a moving table device as shown in FIG. 2 can be constructed. In the same figure, this movable table device has a movable table 1 mounted on a fixed base 11.
The motor M according to this embodiment is fixedly installed on the movable table 12 side, and the other drive motor M' is fixed on the fixed table 11 side. The connecting shaft portion 40 at the end of the ball screw shaft member 31 in , and the shaft MS end of the other drive motor M′ are directly connected by a coupling 51 , and further, the connection shaft portion 40 at the end of the ball screw shaft member 31 in
The vicinity of the other end is rotatably supported by a bearing support member 52.

In such a movable table device, if the rotation direction of each drive motor M, M' is the same, and the rotation speed is slightly different, the nut member 33 will be able to rotate each drive motor M, M'.
Since the movable table 12 moves slightly relative to the ball screw shaft member 31 by the amount corresponding to the rotational difference of M', the movable table 12 follows the nut member 33 and is slightly moved.

Furthermore, if the rotation direction of each drive motor M, M' is reversed and the rotation speed is set to a certain degree, the rotation difference between each drive motor M, M' becomes large, and this large Since the nut member 33 moves relative to the ball screw shaft member 31 at high speed based on the rotation difference, the movable table 12 follows the nut member 33 and is moved rapidly.

In such a process of feeding the movable table 12, the nut member 33 rotates following the rotor core 25 of the drive motor M.
3 not only rotates accurately without being misaligned with respect to the rotation center of the drive motor M, but also the ball screw shaft member 31 is directly connected to the shaft MS of another drive motor M' through the connecting shaft portion 40. Since the ball screw shaft member 31 and other drive motors
The amount of eccentricity with respect to M' can be suppressed to almost zero.
Therefore, at the stage when the rotation of each drive motor M, M' is transmitted to the ball screw shaft member 31 and the nut member 33, the ball screw shaft member 31 and the nut member 33 do not vibrate due to eccentricity and rotate accurately. Operate.

Further, the nut member 33 is attached to the angular contact bearing 34 with respect to the motor housing 20.
is pivotally supported via the nut member 33.
A ball screw shaft member 31 is provided on the inner circumferential surface and outer circumferential surface of the ball screw shaft member 31.
Since the ball raceway surface 38 between the bearing 34 and the ball raceway surface 35 of the bearing 34 can be manufactured coaxially,
The ball screw shaft member 31 and the nut member 33 constituting the motor shaft 30 are reliably arranged coaxially, and the relative rotational movement between the ball screw shaft member 31 and the nut member 33 is performed with high precision.

Therefore, the rotation of each drive motor M, M' is accurately transmitted to the ball screw shaft member 31 and the nut member 33, and the ball screw shaft member 31
Since the nut member 33 moves coaxially, the amount of relative movement of the nut member 33 is kept highly accurate, and the movable table 12 can be accurately moved slightly or rapidly.

Furthermore, in this embodiment, when configuring the movable table device, there is no need to use a separate ball screw unit as in the past, so the number of constituent members of the movable table device is reduced accordingly, and its configuration is simplified.

In the above embodiment, the drive motor M to which the invention is applied is fixedly installed on the movable table 12 side, and the other drive motor M' is fixedly installed on the fixed table 11 side, but the positional relationship between the two is There is no problem in setting it in the opposite way.

[Effects of the Invention] As explained above, according to the hollow shaft motor with a ball screw according to the present invention, the motor shaft is designed to perform the same function as the ball screw unit. Not only can the moving mechanism be easily configured without using a separate mechanism, but since the nut member is rotatably provided to the motor housing via an angular contact bearing, the thrust and radial direction acting on the nut member can be easily configured. The load can be reliably supported, and the support stability of the motor shaft consisting of the nut member and the ball screw shaft member can be ensured.

In addition, the nut member constituting the motor shaft can be rotated following the rotor core, and the ball screw shaft member can be directly connected to other drive motors through the connecting portion, so that the ball screw can be connected directly from each motor to the other drive motor. In addition to basically eliminating rotational transmission errors in the process of transmitting rotational force to the shaft member and the nut member, we have adopted a configuration that basically maintains the coaxiality between the ball screw shaft member and the nut member. Since the ball raceway surface between the ball screw shaft member and the ball raceway surface of the angular contact bearing can be coaxially manufactured on the inner and outer peripheral surfaces of the nut member, the nut member and the ball To ensure coaxiality with a screw shaft member, thereby reliably avoiding vibrations due to misalignment, and to make the rotational movement of a nut member and a ball screw shaft member extremely accurate. Can be done.

Therefore, the amount of relative movement of one member of the motor shaft to the other member can be made extremely accurate. Therefore, when a moving mechanism is configured using such a motor, the member to be moved can be moved slightly or rapidly with high precision.

Furthermore, since the inner ring of the angular contact bearing is omitted and the inner ring equivalent part (ball rolling surface) is integrally formed on the outer peripheral surface of the nut member, it is possible to reduce the weight of the motor rotor, and the weight of the motor rotor can be reduced accordingly. , the inertial force of the rotor can be reduced, the rotation stop precision of the rotor can be improved, and the device can be made more compact.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a hollow shaft motor with a ball screw according to the present invention, FIG. 2 is an explanatory diagram showing an example of a moving table device to which the motor according to the embodiment is applied, and FIG. The figure is an explanatory diagram showing an example of a conventional ball screw unit, FIG. 4 is an explanatory diagram showing an example of a moving table device using a conventional ball screw unit, and FIG. 5 is an explanatory diagram showing another example of a conventional moving table device. FIG. Explanation of symbols, M, M'... Drive motor, 25... Rotor core, 30... Motor shaft, 31... Ball screw shaft member, 32... Ball body, 33... Nut member, 34... Angular contact bearing, 4
0...Connection shaft part (connection part).

Claims (1)

[Claims] 1. A motor housing, a stator core provided within the motor housing, a rotor core rotatably disposed relative to the stator core, and a part of a motor shaft mounted inside the rotor core. a nut member that is rotatably supported by the motor housing through angular contact bearings provided at both ends thereof and rotates following the rotation of the rotor core; and a motor shaft that passes through the nut member. and a ball screw shaft member that is screwed into the nut member via a number of balls and has a connecting portion at least one end thereof to be connected to another rotational drive member, The angular contact bearing has a ball raceway surface recessed on both ends of the outer peripheral surface of the nut member, a ball placed in contact with the ball raceway surface along the ball raceway surface, and a ball fixed to the motor housing. 1. A hollow shaft motor with a ball screw, comprising a ball raceway and an outer ring on which an opposing ball raceway is formed which holds the balls so that they can roll.