CN117040183A - Motor - Google Patents

Abstract

The application provides a motor, which comprises a casing, wherein a motor rotating shaft is arranged in the casing, a brake stator, a brake rotor and a friction disc are sequentially arranged on the motor rotating shaft, the brake rotor is positioned between the friction disc and the brake stator, a limiting part for limiting the brake rotor is also arranged in the casing, and the limiting part is positioned on one side of the brake rotor, which is opposite to the brake rotor. According to the application, the defect that the code disc collides with the encoder stator because the friction disc drives the whole motor shafting to axially displace due to the impact pressure of the brake rotor when the brake in the prior art loses electricity can be overcome, and the braking performance of the motor is improved.

Description

Motor

Technical Field

The application belongs to the technical field of motors, and particularly relates to a motor.

Background

The servo motor is widely applied to the field of robots, is a power source of the robots, the robot joints are driven by the servo motor to realize running and stopping, and when the joints are required to be in a running state, a brake in the servo motor can be opened, and the motor can normally rotate; when the joint needs to be in a stop state, the brake can clamp the motor rotating shaft, so that the joint can keep the existing position.

The brake is divided into an integral brake and a split brake, and an integral brake is proposed in the related art, and when the brake is opened, the friction plate freely moves between the two clamping plates, so that the friction plate and the flange are in clearance fit before, and therefore a back clearance is generated, and the back clearance has an adverse effect on the position of the robot. The split brake has the beneficial effect of zero back clearance because the friction disc is fixedly connected with the rotating shaft.

However, when the brake is powered off and braked, the friction disc can drive the whole motor shaft system to axially displace due to the impact pressure of the brake rotor, so that the encoder can give out fault alarm due to the fact that the displacement of the encoder and the stator of the encoder is reduced, and even the encoder is damaged due to collision of the encoder and the stator of the encoder, as shown in fig. 1 and 2.

Because the friction disc can drive the whole motor shafting to axially displace due to the impact pressure of the brake rotor when the brake in the prior art loses electricity and brakes, the code disc collides with the encoder stator, the code disc is damaged and other technical problems are solved, and the application designs a motor.

Disclosure of Invention

Therefore, the technical problem to be solved by the application is to overcome the defect that the code disc and the encoder stator collide due to the fact that the friction disc is driven to axially displace by the impact pressure of the brake rotor when the brake in the prior art is in power-off braking.

In order to solve the problems, the application provides a motor, which comprises a casing, wherein a motor rotating shaft is arranged in the casing, a brake stator, a brake rotor and a friction disc are sequentially arranged on the motor rotating shaft, the brake rotor is positioned between the friction disc and the brake stator, a limiting part for limiting the brake rotor is also arranged in the casing, and the limiting part is positioned on one side of the brake rotor, which is opposite to the brake rotor.

In some embodiments, the number of the limiting parts is at least two, the limiting parts are connected with the inner wall of the casing, the two limiting parts are oppositely arranged, the distance between the two limiting parts is not smaller than the outer diameter of the friction disc, and the friction disc is located between the two limiting parts.

In some embodiments, the motor further comprises a guide member having a first end and a second end, the first end being disposed on the brake stator, the second end being sleeved on the brake rotor, the guide member being provided with an elastic member.

In some embodiments, a fixing piece is arranged on the brake stator, the fixing piece penetrates through the brake rotor and then is connected with the limiting piece, and the limiting piece is arranged opposite to the friction disc.

In some embodiments, a groove is formed in the peripheral wall of the brake rotor, the fixing piece is located in the groove, the fixing piece penetrates through the limiting piece, adjusting pieces are arranged at two ends of the limiting piece, and the adjusting pieces are connected with the fixing piece.

In some embodiments, the fixing member is provided in plurality along a circumferential direction of the brake stator, the stopper is ring-shaped, and an inner diameter of the stopper is larger than an outer diameter of the friction disc.

In some embodiments, the number of the limiting parts is at least two, the casing is provided with a third end and a fourth end, the motor rotating shaft extends out of the fourth end, the third end is provided with a cover body, a connecting part is arranged on the limiting part, one end of the connecting part is connected with the limiting part, the other end of the connecting part is connected with the cover body, and the limiting part and the friction disc are oppositely arranged along the radial direction of the brake stator.

In some embodiments, the two limiting members are disposed opposite to each other, and a distance between the two limiting members is not smaller than an outer diameter of the friction disc, the friction disc being located between the two limiting members.

In some embodiments, the stopper mover is provided with a through hole, the second end of the guide is positioned in the through hole, and the displacement distance of the stopper mover is not greater than the depth of the through hole.

In some embodiments, the guide member is provided in plurality along a circumferential direction of the brake stator, and the second end is located on the same plane as an end surface of the brake rotor facing away from the brake stator.

The motor provided by the application has the following beneficial effects:

through the locating part, when stopper stator coil loses electricity, the stopper active cell receives the backward axial force of spring, and the friction disc is pushed down backward, and the locating part carries out axial spacing to the stopper active cell for can not continue taking place axial displacement after the stopper active cell pushes down the friction disc, avoid the stopper active cell to drive the shafting of motor along axial displacement, thereby encoder code wheel collides with encoder stator, causes the encoder to damage, accurate regulation and restriction split type stopper active cell's axial displacement reduces braking moment, improves the braking performance of motor.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It will be apparent to those skilled in the art from this disclosure that the drawings described below are merely exemplary and that other embodiments may be derived from the drawings provided without undue effort.

The structures, proportions, sizes, etc. shown in the present specification are shown only for the purposes of illustration and description, and are not intended to limit the scope of the application, which is defined by the claims, so that any structural modifications, changes in proportions, or adjustments of sizes, which do not affect the efficacy or the achievement of the present application, should fall within the ambit of the technical disclosure.

FIG. 1 is a schematic diagram of a prior art motor;

FIG. 2 is an enlarged view of a portion of FIG. 1;

FIG. 3 is a schematic diagram of an electric machine according to an embodiment of the present application;

FIG. 4 is a schematic illustration of a brake in an electric machine according to an embodiment of the present application;

FIG. 5 is an enlarged view of a portion of FIG. 4;

fig. 6 is an exploded view of fig. 4.

The reference numerals are expressed as:

1. a housing; 2. a brake stator; 3. a brake mover; 4. a friction plate; 5. an encoder code wheel; 6. an encoder stator; 7. a limiting piece; 8. a motor shaft; 9. a motor rotor; 10. a front bearing; 11. a rear bearing; 12. an adjusting member; 13. an elastic member; 14. a guide member; 15. a fixing member; 16. a motor stator.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

It should be understood that the term "and/or" as used herein is merely one relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present application unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

In the description of the present application, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present application and simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present application; the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present application.

Referring to fig. 3 to 6, according to an embodiment of the present application, a motor is provided, including a casing 1, a motor rotating shaft 8 is disposed in the casing 1, one end of the motor rotating shaft 8 extends out of the casing 1, the other end is provided with an encoder code disc 5, a brake stator 2, a brake rotor 3 and a friction disc 4 are sequentially disposed on the motor rotating shaft 8, the brake rotor 3 is located between the friction disc 4 and the brake stator 2, the friction disc 4 is located between the brake rotor 3 and the encoder code disc 5, and the limiting member 7 is located on a side of the brake rotor 3 facing away from the brake rotor 3, that is, the limiting member 7 is located between the brake rotor 3 and the encoder code disc 5. In this technical scheme, through locating part 7, when the power loss of the stator 2 coil of stopper, stopper rotor 3 receives the backward axial force of spring, push down friction disc 4 backward, locating part 7 carries out axial spacing to stopper rotor 3 for stopper rotor 3 can not continue to take place axial displacement after pushing down friction disc 4, avoid stopper rotor 3 to drive the shafting of motor to follow axial displacement, thereby encoder code wheel 5 collides with encoder stator 6, cause the encoder to damage, accurate regulation and restriction split type stopper rotor 3's axial displacement reduces the braking moment, improve the braking performance of motor. The motor of the application has the advantage of zero backlash because the friction disc 4 is fixed with the motor shaft 8.

In the application, referring to fig. 3, since the inner ring of the front bearing 10, the inner ring of the motor rotor 9, the inner ring of the rear bearing 11, the friction disk 4 and the encoder code disk 5 are all fixed on the motor rotating shaft 8, all the components can be defined as the shaft system of the motor. The encoder comprises an encoder code disc 5 and an encoder stator 6, the brake comprises a brake stator 2, a brake rotor 3 and a friction disc 4, the friction disc 4 and the brake stator 2 are fixed on a motor rotating shaft 8, the brake rotor 3 can move along the axial direction of the motor rotating shaft 8, a motor stator 16 is arranged in a machine shell 1, a motor rotor 9 is sleeved in the motor stator 16, the motor rotating shaft 8 is sleeved in the motor rotor 9, one end of the motor rotating shaft 8 extends out of the machine shell 1, the encoder code disc 5 is arranged at the other end of the motor rotating shaft, the encoder stator 6 is positioned between the encoder code disc 5 and the inner wall of the machine shell 1, a front bearing 10 is arranged between the motor rotating shaft 8 and the machine shell 1, a rear bearing 11 is also arranged on the motor rotating shaft 8, a gap b is arranged between the motor rotor 9 and the brake, and the encoder code disc 5 and the encoder stator 6 are provided with a gap b. When the brake is opened, a gap a exists between the friction disc 4 and the brake rotor 3, the friction disc 4 can rotate along with the motor, when the brake is braked, the gap a=0, and the rotation of the friction disc 4 is limited, so that the motor is limited to rotate, and the brake is realized.

In some embodiments, as shown in fig. 4, at least two limiting members 7 are provided, the limiting members 7 are connected to the inner wall of the casing 1, the two limiting members 7 are disposed opposite to each other, and a distance between the two limiting members 7 is not smaller than an outer diameter of the friction disc 4, and the friction disc 4 is located between the two limiting members 7. In this technical scheme, locating part 7 is platy, locating part 7 arranges along friction disc 4 circumference, and, the terminal surface of locating part 7 is located the coplanar with the terminal surface of friction disc 4, namely, the thickness of locating part 7 is the same with the thickness of friction disc 4, along the radial of friction disc 4, locating part 7 is located the outside of friction disc 4, through locating part 7, carry out axial spacing to stopper rotor 3 when locating part 7 for stopper rotor 3 can not continue to take place axial displacement after pushing down friction disc 4, avoid stopper rotor 3 to drive the shafting of motor along axial displacement, thereby encoder code wheel 5 collides with encoder stator 6.

In some embodiments, the motor further comprises a guide member 14, the guide member 14 has a first end and a second end, the first end is disposed on the brake stator 2, the second end is sleeved on the brake rotor 3, and the guide member 14 is provided with an elastic member 13. In the technical scheme, preferably, the elastic piece 13 adopts a spring, the elastic piece 13 is sleeved on the guide piece 14, the radial direction of the brake rotor 3 is limited through the guide piece 14, the radial shaking of the brake rotor 3 is avoided, the brake rotor 3 is guaranteed to move radially only, preferably, the guide piece 14 adopts a guide pin, one end of the guide pin is fixed on the brake stator 2, and the other end of the guide pin is sleeved on the brake rotor 3, so that the brake rotor 3 can move along the guide piece 14.

In some embodiments, the fixing member 15 is disposed on the brake stator 2, and the fixing member 15 is connected to the limiting member 7 after passing through the brake rotor 3, where the limiting member 7 is disposed opposite to the friction disc 4. In this technical scheme, the stopper 7 is mounted on the brake stator 2, and the stopper 7 is fixed by the brake stator 2.

In some embodiments, as shown in fig. 5 and 6, a groove is formed in the peripheral wall of the brake rotor 3, the fixing member 15 is located in the groove, the fixing member 15 penetrates through the limiting member 7, two ends of the limiting member 7 are provided with adjusting members 12, and the adjusting members 12 are connected with the fixing member 15. In this technical scheme, through being provided with the recess on the periphery wall of stopper active cell 3, mounting 15 is located in the recess for stopper active cell 3 when moving, avoided mounting 15 to produce the influence to stopper active cell 3, of course, also can set up the through-hole on stopper active cell 3, the diameter of through-hole is greater than the external diameter of locating part 7, make locating part 7 pass the through-hole, thereby guarantee the displacement of stopper active cell 3, preferably, regulating part 12 adopts the nut, mounting 15 adopts the bolt, regulating part 12 and mounting 15 threaded connection, two regulating parts 12 are located the both sides of locating part 7 respectively, thereby can be according to the performance of elastic component 13, adjust the distance between locating part 7 and the stopper active cell 3, thereby guarantee the limiting effect.

In the prior art, referring to fig. 1 and 2 in combination, there is an air gap between the motor stator 16 and the motor rotor 9, and the motor rotor 9 has magnets thereon, and when alternating current is applied to the coils on the motor stator 16, the motor rotor 9 rotates. The motor rotor 9 is in interference fit with the motor rotating shaft 8, the motor rotating shaft 8 is supported on the front bearing and the rear bearing, the direction of the motor rotor 9 to the front bearing 10 is defined as the forward direction, and the direction of the motor rotor 9 to the rear bearing 11 is defined as the backward direction.

A brake is arranged behind the rear bearing 11 and consists of a brake stator 2, a brake rotor 3 and a friction disc 4, wherein the friction disc 4 is fixed on a rotating shaft through a flat key and a pin.

The rear of the brake is provided with an encoder, the encoder consists of an encoder code disc 5 and an encoder stator 6, wherein the encoder code disc 5 is fixed on a motor rotating shaft 8, a gap b is arranged between the encoder code disc 5 and the encoder stator 6, and the encoder is a precise angle sensor, so that the dimensional accuracy requirement of the gap b is high, the allowable deviation is generally +/-0.15 mm, and fault alarm occurs when the allowable deviation exceeds the allowable deviation.

A coil is arranged in the brake stator 2 to provide electromagnetic attraction force which is larger than the spring force, so that the brake rotor 3 is separated from the friction disc 4; the compression spring is used for providing the pressure of the brake rotor 3 and the friction disc 4 so as to generate enough friction torque; the friction disc 4 is fixed on the motor rotating shaft 8, when the brake is opened, a gap a exists between the friction disc 4 and the brake rotor 3, the friction disc 4 can rotate along with the motor, when the brake is braked, the gap a=0, the rotation of the friction disc 4 is limited, and therefore the motor is limited to rotate, and the brake is realized; this split brake solution has the advantage of zero backlash, since the friction disc 4 is fixed to the motor shaft 8.

The front bearing 10 and the rear bearing 11 are ball bearings, and because of the play of the ball bearings, when the ball bearing outer ring is fixed and the inner ring receives axial force, the bearing inner ring and the bearing outer ring are dislocated, namely, the inner ring generates axial displacement, and the larger the axial force received by the bearing inner ring is, the larger the axial displacement of the inner ring is.

In summary, when the coil of the brake stator 2 is de-energized, the brake rotor 3 moves backward and presses against the friction disc 4 due to the spring force, and the entire shaft system receives the backward axial force from the brake rotor 3. Too small spring force can cause the brake time to be prolonged and friction torque to be reduced, the brake performance to be reduced, too large spring force can cause the backward displacement of the shaft system to exceed the allowable tolerance of the clearance b, even the too large spring force can exceed the size of the clearance b, the encoder code wheel 5 can contact and collide with the encoder stator 6, and the encoder code wheel 5 is damaged. Even if a spring with an appropriate elastic force is selected at a certain temperature, the spring modulus of the spring varies with temperature and time, and thus long-term reliability is not ensured.

In the application, the spacing piece 7 can be matched with tools such as a plug gauge through 2 adjusting pieces 12 on the stud, the clearance c between the spacing piece 7 and the brake rotor 3 can be adjusted, and the mounting manufacturability is good;

in order to ensure the friction torque performance of the brake and prevent the encoder from alarming due to overlarge deviation of the clearance b, the size of the clearance c should be:

(gap a+0.05) < gap c < (gap a+0.15);

in the motor of the application, the coil of the brake stator 2 is electrified to attract the brake rotor 3 to be separated from the friction disc 4, and the brake is in an open state at the moment. When the coil of the brake stator 2 is de-energized, the brake rotor 3 is subjected to the backward axial force of the elastic piece 13, and the friction disc 4 is pressed backward, so that the motor shaft system moves backward axially until the brake rotor 3 contacts with the limiting piece 7, and good contact between the brake rotor 3 and the friction disc 4 is ensured because c is more than a+0.05. The specific analysis is as follows:

assuming that the shafting displacement is x, the gap between the final encoder disk 5 and the encoder stator 6 is b ', i.e., b' =b-x;

in the process, the brake rotor 3 moves backwards by c, the friction disc 4 moves backwards by (c-a), and the shafting displacement is the same as the friction disc 4 displacement, namely x= (c-a);

since c < a+0.15;

therefore, x+a < a+0.15, i.e., x < 0.15, i.e., b' -b < 0.15, so as to meet the accuracy requirement of the encoder for the deviation of the gap b.

In some embodiments, a plurality of fixing members 15 are provided along the circumferential direction of the brake stator 2, the limiting member 7 is annular, and the inner diameter of the limiting member 7 is larger than the outer diameter of the friction disc 4. In this technical scheme, locating part 7 is cyclic annular, and friction disc 4 is located locating part 7, and fixed locating part 7 through a plurality of mounting 15 guarantees that locating part 7 can not take place the displacement when receiving the impact of stopper active cell 3, improves spacing effect.

In some embodiments, the number of the limiting members 7 is at least two, the casing 1 has a third end and a fourth end, the motor rotating shaft 8 extends out of the fourth end, the third end is provided with a cover, the limiting members 7 are provided with connecting members, one ends of the connecting members are connected with the limiting members 7, the other ends of the connecting members are connected with the cover, and the limiting members 7 are arranged opposite to the friction disc 4 along the radial direction of the brake stator 2. Further, the two limiting members 7 are oppositely arranged, and the distance between the two limiting members 7 is not smaller than the outer diameter of the friction disc 4, and the friction disc 4 is located between the two limiting members 7. In the technical proposal, the cover body is a rear cover of the motor, the limiting piece 7 is arranged on the rear cover, the end surface of the limiting piece 7 and the end surface of the friction disk 4 are positioned on the same plane, namely, the thickness of the limiting piece 7 is the same as the thickness of the friction disk 4, along the radial direction of the friction disk 4, the limiting piece 7 is positioned outside the friction disk 4,

according to the motor, a coil of a brake stator 2 is powered on, a brake rotor 3 is driven by the brake stator 2, and a fixing piece 15 is arranged on the brake stator 2; the brake rotor 3 is provided with grooves, and the brake rotor 3 is limited by the guide member 14 and is under the elastic action of the compression elastic member 13 while avoiding the fixing member 15 and the adjusting member 12; when the limiting piece 7 is annular, the inner hole diameter of the limiting piece 7 is larger than the outer diameter of the friction disc 4, so that the normal operation of the friction disc 4 is not affected; the stopper 7 is provided behind the brake rotor and is fixed to the fixing member 15 by the adjusting member 12.

In the application, when the brake is powered off, the brake rotor 3 can axially press the friction disc 4 under the action of the spring, so that the brake is in a braking state, and the motor can not rotate at the moment; when the brake is powered on, the brake rotor 3 overcomes the spring force under the action of electromagnetic attraction and is separated from the friction disc 4, so that the brake is in an open state, the motor can rotate freely at the moment, and the brake is provided with a limiting piece 7, so that the axial displacement of the brake rotor 3 can be limited. The brake stator 2 is provided with a fixing member 15, and the stopper 7 is fixed to the fixing member 15, and the gap between the stopper 7 and the brake rotor 3 can be adjusted by adjusting the adjusting member 12 on the fixing member 15. Through accurate regulation and restriction split type stopper active cell 3's axial displacement, the excessive axial displacement of motor shafting when avoiding losing the electric brake to avoid causing encoder trouble warning or damage, avoid braking moment to reduce, braking performance variation.

In some embodiments, the stopper mover 3 is provided with a through hole, the second end of the guide member 14 is positioned in the through hole, and the displacement distance of the stopper mover 3 is not greater than the depth of the through hole. Specifically, a plurality of guide members 14 are provided along the circumferential direction of the brake stator 2, and the second end and the end surface of the brake rotor 3 facing away from the brake stator 2 are located on the same plane. In this technical scheme for the second end of guide 14 does not stretch out the terminal surface of stopper rotor 3, prevent that stopper rotor 3 from when rotating, or when compressing tightly friction disc 4, guide 14 causes the damage to friction disc 4, simultaneously, the installation of locating part 7 of also being convenient for, of course, the second end of guide 14 also can stretch out the terminal surface of stopper rotor 3, only need guarantee that guide 14 extension's length is not greater than the distance between stopper rotor 3 and the friction disc 4 can.

It will be readily appreciated by those skilled in the art that the above advantageous ways can be freely combined and superimposed without conflict.

The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application. The foregoing is merely a preferred embodiment of the present application, and it should be noted that it will be apparent to those skilled in the art that modifications and variations can be made without departing from the technical principles of the present application, and these modifications and variations should also be regarded as the scope of the application.

Claims (10)

1. The utility model provides a motor, its characterized in that, includes casing (1), be provided with motor shaft (8) in casing (1), motor shaft (8) are last to have set gradually stopper stator (2), stopper rotor (3) and friction disc (4), stopper rotor (3) are located friction disc (4) with between stopper stator (2), still be provided with in casing (1) and be used for right stopper rotor (3) spacing locating part (7), locating part (7) are located stopper rotor (3) are dorsad one side of stopper rotor (3).

2. A motor according to claim 1, characterized in that at least two of the limiting members (7) are provided, the limiting members (7) are connected to the inner wall of the casing (1), the two limiting members (7) are disposed opposite to each other, the distance between the two limiting members (7) is not smaller than the outer diameter of the friction disc (4), and the friction disc (4) is disposed between the two limiting members (7).

3. An electric machine according to claim 1, characterized in that the electric machine further comprises a guide member (14), the guide member (14) having a first end and a second end, the first end being arranged on the brake stator (2), the second end being arranged over the brake rotor (3), the guide member (14) being provided with an elastic member (13).

4. A motor according to claim 3, characterized in that the brake stator (2) is provided with a fixing member (15), the fixing member (15) is connected to the limiting member (7) after passing through the brake rotor (3), and the limiting member (7) is arranged opposite to the friction disc (4).

5. An electric motor according to claim 4, characterized in that the outer peripheral wall of the brake rotor (3) is provided with a groove, the fixing member (15) is located in the groove, the fixing member (15) penetrates through the limiting member (7), two ends of the limiting member (7) are provided with adjusting members (12), and the adjusting members (12) are connected with the fixing member (15).

6. An electric motor according to claim 4, characterized in that the fixing member (15) is provided in plural in the circumferential direction of the brake stator (2), the stopper member (7) is annular, and the inner diameter of the stopper member (7) is larger than the outer diameter of the friction disc (4).

7. A motor according to claim 1, characterized in that the number of the limiting members (7) is at least two, the housing (1) is provided with a third end and a fourth end, the motor rotating shaft (8) extends out of the fourth end, the third end is provided with a cover body, the limiting members (7) are provided with connecting members, one ends of the connecting members are connected with the limiting members (7), the other ends of the connecting members are connected with the cover body, and the limiting members (7) are arranged opposite to the friction disc (4) along the radial direction of the brake stator (2).

8. An electric machine according to claim 7, characterized in that two of the limit pieces (7) are arranged opposite each other, and that the distance between the two limit pieces (7) is not smaller than the outer diameter of the friction disc (4), the friction disc (4) being located between the two limit pieces (7).

9. A motor according to claim 3, characterized in that the brake rotor (3) is provided with a through hole, the second end of the guide (14) being located in the through hole, and that the displacement distance of the brake rotor (3) is not greater than the depth of the through hole.

10. An electric machine according to claim 9, characterized in that the guide (14) is provided in a plurality in the circumferential direction of the brake stator (2), the second end being in the same plane as the end face of the brake rotor (3) facing away from the brake stator (2).