JP7262517B2 - electric motor and fuel pump - Google Patents

Description

The present application relates to electric motors and fuel pumps.

A fuel pump is installed in the fuel tank of automobiles such as four-wheeled vehicles and two-wheeled vehicles. The fuel pump is driven by an electric motor. A fuel pump is composed of a pump chamber and an electric motor for driving the chamber.

The electric motor has a rotor through which a shaft penetrates, and a flat plate-shaped commutator perpendicular to the rotating shaft is provided on one side of the rotor in the axial direction. Current is supplied to this commutator by brushes in pressure contact. The rotor coils of the rotor are energized through the brushes and commutator to rotate the motor. The brushes are axially urged against the commutator of the rotor by a resilient member. Therefore, it comes into contact with the rotor and slides according to the rotation of the rotor.

Since the fuel pump is operated while immersed in fuel (eg, hydrocarbon fuel such as gasoline), it is required to have corrosion resistance to the fuel. Therefore, sintered carbon (carbon) is used for the contact member of the commutator that slides on the brushes of the commutator to ensure corrosion resistance to the fuel. At the same time, the use of sintered carbon can reduce wear on the commutator and brushes, extending their life.

In such a motor structure, a brush holder that holds the brushes slidably with respect to the commutator is arranged to face the commutator in the axial direction. A fuel pump may receive an impact load such as vibration from a vehicle in which the fuel pump is mounted, causing the rotor to move in the axial direction (toward the brush holder). In this case, the contact member made of carbon of the commutator collides with the brush holder. As a result of the collision, the sintered carbon contact members of the commutator can break.

As a countermeasure, it has been proposed to provide a brush holder or a rotor with projections. The protrusions restrict axial movement of the rotor. As a result, it is possible to prevent the contact member of the commutator from colliding with the brush holder. Therefore, it is possible to avoid damage to the contact member made of sintered carbon of the commutator due to the impact of the collision (for example, Patent Document 1).

JP-A-9-182381

According to the technique disclosed in Patent Document 1, an impact load is applied to the electric motor that drives the fuel pump due to vibrations from the vehicle. This load causes the rotor to move, and the protrusions of the brush holder come into contact with the rotor, or the protrusions of the rotor come into contact with the brush holder. At this time, since the rotor is rotating, the number of rotations of the rotor decreases due to the sliding frictional resistance of the protrusions, resulting in a decrease in pump efficiency. In addition, there is a possibility that the protrusions are worn by the sliding friction, and the abrasion powder is caught between the contact members of the brushes and the commutator. If the abrasion powder gets caught, it is conceivable that the electric current between the brushes and the commutator is blocked, the electric motor stops, and the fuel cannot be supplied to the engine.

The present application has been made in view of the actual situation as described above. The structure prevents the commutator from contacting the brush holder even when the rotor moves in the axial direction (brush holder side). To provide an electric motor in which power supply between brushes and a commutator is not hindered by powder.

Further, according to the present application, even when the rotor moves in the axial direction (toward the brush holder), the commutator does not come into contact with the brush holder. To provide a highly reliable fuel pump equipped with an electric motor in which energization between brushes and a commutator is not hindered by abrasion powder caused by sliding friction.

The electric motor according to the present application is
shaft,
A rotor core attached to a shaft and wound with rotor windings, a disk-shaped commutator connected to the rotor windings and provided on one side in the axial direction of the rotor windings , and supporting the commutator and a commutator holder in which an outer peripheral portion surrounding the commutator protrudes from the commutator to one side in the axial direction,
a brush facing the commutator and protruding toward the other side in the axial direction;
a brush holder that presses the brush against the commutator,
a radial bearing that radially supports the shaft;
a brush holder side thrust bearing that supports the shaft from the brush holder side to the other side in the axial direction,
The first distance, which is the axial distance between the brush holder and the commutator, is greater than the second distance, which is the amount of axial play between the shaft and the brush-holder-side thrust bearing , and A fourth distance, which is the axial distance between the brush holder and the outer circumference of the commutator holder, is larger than the second distance.
Further, the electric motor according to the present application is
shaft,
A rotor having a rotor core attached to a shaft and wound with rotor windings, and a disk-shaped commutator connected to the rotor windings and provided on one axial side of the rotor windings. ,
a brush facing the commutator and protruding toward the other side in the axial direction;
a brush holder that presses the brush against the commutator,
a radial bearing that radially supports the shaft;
a brush holder side thrust bearing supported on the other side in the axial direction from the brush holder side by an elastic body that axially presses the shaft in the direction in which the brush is pressed against the commutator by the brush holder;
The first distance, which is the axial distance between the brush holder and the commutator, is larger than the second distance, which is the amount of axial play between the shaft and the brush holder side thrust bearing. It is something to do.
Furthermore, the electric motor according to the present application is
shaft,
A rotor having a rotor core attached to a shaft and wound with rotor windings, and a disk-shaped commutator connected to the rotor windings and provided on one axial side of the rotor windings. ,
a brush facing the commutator and protruding toward the other side in the axial direction;
a brush holder that presses the brush against the commutator,
a radial bearing that radially supports the shaft;
a brush holder side thrust bearing that axially supports the shaft from the brush holder side to the other side in the axial direction;
The first distance, which is the axial distance between the brush holder and the commutator, is greater than the second distance, which is the amount of axial play between the shaft and the brush holder side thrust bearing, and the brush The holder is characterized in that the brush can be accommodated in such a state that the tip of the brush holder and the brush are on the same plane.

Further, the fuel pump according to the present application is
It is equipped with the electric motor described above.

According to the electric motor according to the present application, the structure is such that the commutator does not come into contact with the brush holder even when the rotor moves in the axial direction (toward the brush holder). It is possible to obtain an electric motor in which electricity supply between the brushes and the commutator is not hindered by abrasion powder caused by sliding friction between the brushes and the brush holder.

Further, according to the fuel pump according to the present application, even when the rotor moves in the axial direction (toward the brush holder), the commutator does not come into contact with the brush holder, thereby preventing damage to the commutator. In addition, since the electric motor can be provided in such a manner that the energization between the brushes and the commutator is not hindered by abrasion powder caused by the sliding friction between the rotor and the brush holder, the reliability of the fuel pump can be improved.

1 is a cross-sectional view of a fuel pump according to Embodiment 1; FIG. 4 is an enlarged view of a commutator portion of the electric motor of the fuel pump according to Embodiment 1; FIG. FIG. 8 is an enlarged view of a commutator portion of the electric motor of the fuel pump according to Embodiment 2; FIG. 11 is an enlarged view of a commutator portion of an electric motor of a fuel pump according to Embodiment 3;

1. Embodiment 1
<Overall composition>
An electric motor and a fuel pump according to the present application will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of fuel pump 101 according to Embodiment 1. FIG. The fuel pump 101 is composed of a pump chamber 201 and an electric motor 202 . The electric motor 202 is provided as a drive source for driving the pump chamber 201 of the fuel pump 101 .

Electric motor 202 has rotor 4 and stator 25 . The rotor 4 is provided with a rotor core 21 through which the shaft 5 passes. A rotor winding 22 is wound around the rotor core 21 . The stator 25 is provided with permanent magnets or stator coils. Here, in FIG. 1, the axial direction is indicated by X, and the one axial side X2 and the other axial side X1 are indicated by arrows.

The shaft 5 is assembled to the main body of the fuel pump 101 by two or more radial bearings 6, and the radial movement of the shaft 5 is restricted while the shaft 5 is rotatably supported. In addition, one or more thrust bearings 8 are attached to the shaft 5, and movement of the shaft 5 in the axial direction X is restricted while the shaft 5 is rotatably supported.

A disc-shaped commutator 1 is provided perpendicularly to the axial direction X on one side X2 of the rotor in the axial direction. Rotor winding 22 is electrically connected to commutator 1 . A brush 3 protrudes toward the other side X1 in the axial direction so as to face the commutator 1 . The brush 3 is supported by a brush holder 7 and pressed against the commutator 1 by a pressing member 2 provided on the brush holder. When the rotor 4 rotates, the commutator 1 also rotates and the brushes 3 slide while contacting the commutator 1 . This sliding maintains the electrical connection between the brushes 3 and the commutator 1 . A field current is supplied to the rotor winding 22 through the brushes 3 and the commutator 1 to rotate the rotor 4 .

<Commutator and brush>
The fuel pump 101 is installed in the fuel tank of the vehicle, and the inside of the electric motor 202 is also immersed in fuel during use. Since they are immersed in a hydrocarbon liquid fuel such as gasoline, even if a current spark occurs between the brushes 3 and the commutator 1, the fuel will not ignite. This is because there is no air, only fuel, so no combustion occurs.

Since the brush 3 and the commutator 1 slide while immersed in fuel, they are required to have conductivity, corrosion resistance to the fuel, physical toughness against sliding, and low frictional resistance. For this reason, sintered carbon (carbon) is used for the contact member of the commutator 1 that contacts the brush 3 . By forming the contact member of the commutator 1 from sintered carbon, it becomes possible to conduct electricity while improving corrosion resistance and wear resistance, maintaining low frictional resistance, and keeping the electrical resistance value low.

Since the fuel pump 101 is installed in the vehicle, it is subjected to vibrations due to acceleration/deceleration, turning, and impact from the road surface that accompany running of the vehicle. In particular, the shaft 5 of the electric motor 202 moves in the X-axis direction due to the impact in the X-axis direction. Movement of the shaft 5 changes the distance between the commutator 1 provided on the rotor 4 and the brush holder 7 attached to the motor body. However, since the brushes 3 are pressed against the commutator 1 by the pressing member 2 attached to the brush holder 7, the amount of protrusion of the brushes 3 from the brush holder 7 is adjusted, and the brushes 3 to the commutator 1 are adjusted. Contact is maintained. A coil spring, a leaf spring, or the like is used as the pressing member 2 .

<Electricity inhibition between commutator and brush>
When a large impact is applied to the vehicle in the axial direction X, the shaft 5 may move greatly and the commutator 1 and the brush holder 7 may collide. At this time, the commutator 1 may collide with the brush holder 7 and be damaged. In addition, since the commutator 1 rotates together with the rotor 4, abrasion powder may be generated due to sliding friction between the colliding brush holder 7 and the commutator 1. FIG. When the abrasion powder is caught between the commutator 1 and the brushes 3, it may interfere with the contact between the commutator 1 and the brushes 3, increase the contact resistance, and cut off the current flow.

The fuel pump 101 is a highly important safety component in the vehicle. When the fuel pump 101 stops operating, the fuel supply to the internal combustion engine is interrupted, and the vehicle becomes unable to run. In order to improve the failure tolerance of the vehicle and maintain the limp home function (a function that ensures minimum driving performance even if the function is degraded), it is necessary to ensure that the fuel pump continues to operate.

Conventionally, in order to avoid damage to the commutator due to collision between the commutator 1 and the brush holder 7, projections are provided on the brush holder 7 or the rotor 4 so that the commutator 1 directly contacts the brush holder 7. has been proposed to prevent However, although this method can prevent the commutator 1 from coming into direct contact with the brush holder 7, contact between the protrusions provided on the brush holder 7 and the rotor 4 and the protrusions provided on the rotor 4 and the brush holder 7 or contact between the protrusions provided on the rotor 4 and the protrusions provided on the brush holder 7 occurs. Since the rotor 4 is rotating, there remains a possibility that abrasion powder will be generated due to sliding friction due to contact between them. It cannot be ruled out that abrasion powder is caught between the commutator 1 and the brushes 3, inhibits contact between the commutator 1 and the brushes 3, increases the contact resistance, and cuts off the current.

<Setting the thrust bearing>
FIG. 2 is an enlarged view of the commutator 1 portion of the electric motor 202 of the fuel pump 101 according to the first embodiment. In Embodiment 1 of the present application, contact between the rotor 4 and the brush holder 7 is prevented by setting the thrust bearing 8 that supports the shaft 5 in the axial direction X. FIG. This setting will be explained. A thrust bearing is a bearing that receives an axial load and restricts axial movement while enabling rotation with low friction. Thrust bearings are sometimes called axial bearings.

The distance in the axial direction X between the disk-shaped commutator 1 provided on the rotor 4 and the brush holder 7 is shown as a first distance L1 in FIG. There is play in the axial direction X between the shaft 5 and the thrust bearing 8 . The amount of this play is shown as the second distance L2 in FIG. The play in the bearing is also called internal clearance or backlash. Contact between the rotor 4 and the brush holder 7 can be prevented by setting the relationship between the first distance L1 and the second distance L2 as L1>L2.

When a large impact is applied to the vehicle in the axial direction X and the rotor 4 and the shaft 5 of the fuel pump 101 try to move to the one axial side X2, the tip of the shaft 5 is restrained by the thrust bearing 8. be done. As a result, the commutator 1 of the rotor 4 can maintain a clearance with the brush holder 7 and avoid collision.

In FIG. 2, the thrust bearing 8 has a single ball shape. Since the electric motor 202 is used while immersed in fuel, it is lubricated by the fuel, and even the thrust bearing 8 of such a simple form can maintain a small rotational friction. The thrust bearing 8 may also be a thrust bearing containing a plurality of ball bearings sandwiched between flat plates, a thrust bearing containing a plurality of roll bearings sandwiched between flat plates, or a slide bearing. This is because any bearing that restricts the movement of the shaft 5 in the axial direction X may be used. Further, here, the thrust bearing 8 that restricts the movement of the shaft 5 in the direction of one side X2 in the axial direction has been described, but a thrust bearing that restricts the movement of the shaft 5 in the direction of the other side X1 in the axial direction is added. may be provided.

In FIG. 2, the radial bearing 6 that regulates the radial movement of the shaft 5 is of a type in which a plurality of roll bearings are sandwiched between large and small cylindrical structures. As the radial bearing, in addition to this, a radial bearing or sliding bearing of a type in which a plurality of ball bearings are incorporated and sandwiched between large and small cylindrical structures may be used.

<Movement of brush>
Here, the relative position of the brush 3 with respect to the brush holder 7 will be described. The brush 3 is partially housed in the brush holder 7 and protrudes to the other side X1 in the axial direction to come into contact with the commutator 1 . The first distance L1 between the commutator 1 and the brush holder 7 changes due to the impact in the axial direction X received by the fuel pump 101 due to vehicle motion. Even in such a case, the brush 3 receives force from the brush holder 7 so as to protrude from the brush holder 7 in the direction of the other side X1 in the axial direction so that the brush 3 can maintain contact with the commutator 1 .

A variable range of the amount of brush 3 protruding from brush holder 7 is shown as third distance L3 in FIG. The third distance L3 is obtained as the difference between the position when the pressing member 2 is most compressed and the position when the pressing member 2 is most extended. It can also be said to be the difference between the position where the brush 3 is most retracted into the brush holder 7 and the position where the tip is most protruded from the brush holder 7 when the brush 3 protrudes from the brush holder 7 . The relationship between the first distance L1 and the third distance L3 is preferably L3>L1. Even if the positions of the commutator 1 and the brush holder 7 change, the brush 3 must always keep contact with the commutator 1 . This is because the third distance L3, which is the movable distance of the brush 3, should exceed the first distance L1, which is the distance between the commutator 1 and the brush holder 7. FIG.

In the first embodiment, when a large impact is applied to the vehicle in the axial direction X, rotor 4 and shaft 5 of fuel pump 101 tend to move to one axial side X2. In this case, the tip of the shaft 5 is restricted from moving by the thrust bearing 8 . At this time, the actual amount of movement between the rotor 4 and the motor main body is regulated by the second distance L2. Therefore, it is sufficient for the third distance L3, which is the amount of movement of the brush 3, to satisfy the condition of L3>L2.

However, even if the thrust bearing 8 fails for some reason and the regulation in the axial direction X becomes impossible, the brush 3 must always keep contact with the commutator 1 . Therefore, it is significant that the third distance L3, which is the movable distance of the brush 3, is larger than the first distance, which is the distance between the brush holder 7 and the commutator 1. FIG. This is because the brushes 3 can be brought into contact with the commutator 1 to rotate the electric motor 202 even if the thrust bearing 8 fails for some reason and the regulation in the axial direction X becomes impossible. This is because the operation of the fuel pump 101 can be maintained and the limp home function can be ensured.

2. Embodiment 2
<Elastic body of thrust bearing>
FIG. 3 is an enlarged view of the commutator 1 portion of the electric motor 202a of the fuel pump 101a according to the second embodiment. In the fuel pump 101a according to Embodiment 2, the electric motor 202a is provided with a thrust bearing 8a of a built-in ball bearing type. The thrust bearing 8a restricts the axial movement of the shaft 5a in the one side X2 direction. The thrust bearing 8a is supported by the main body of the electric motor 202a by an elastic body 9. As shown in FIG. Further, the shaft 5a is fixed to the main body of the electric motor 202a by a radial bearing 6a of a type in which a plurality of ball bearings are incorporated and sandwiched between large and small cylindrical structures. Fuel pump 101a according to the second embodiment differs from fuel pump 101 according to the first embodiment only in these points.

The thrust bearing 8a is supported by the main body of the electric motor 202a by an elastic body 9. As shown in FIG. Therefore, when the rotor 4a moves in the one axial direction X2 due to the motion of the vehicle, the impact is alleviated. The elastic body 9 can suppress the contact noise caused by the collision between the shaft 5a and the thrust bearing 8a. Therefore, it is possible to prevent the driver from feeling discomfort due to abnormal noise. In addition, it is possible to prevent the life of the thrust bearing 8a and the shaft 5a from being shortened due to the impact caused by the collision.

The elastic body 9 that fixes the thrust bearing 8a to the main body of the electric motor 202a may be a coil spring, a plate spring, or a cushion material. It is desirable that the pressing force Fs applied to the thrust bearing 8a or the shaft 5a by the elastic body 9 is set larger than the pressing force Fb applied to the brush 3 by the pressing member 2 arranged in the brush holder 7. FIG. That is, the relationship between the pressing force Fs and the pressing force Fb is set to Fs>Fb.

The elastic body 9 supporting the thrust bearing 8a must play a role of receiving and mitigating the inertia and acceleration of the rotor 4a, and must be designed to withstand a large impact. On the other hand, the pressing force Fb of the pressing member 2 for pressing the brush 3 against the commutator 1 only needs to play the role of bringing the brush 3 into contact with the commutator 1 . If the pressing force Fb for pressing the brushes 3 against the commutator 1 is excessive, the sliding resistance increases and the output of the electric motor 202a decreases. Furthermore, the sliding friction wears the contact surface between the brush 3 and the commutator 1, leading to a shortened life. Therefore, it is desirable that the pressing force Fb of the pressing member 2 for pressing the brushes 3 against the commutator 1 is small as long as the electrical connection between the brushes 3 and the commutator 1 can be maintained.

3. Embodiment 3
<Commutator holder>
FIG. 4 is an enlarged view of the commutator 1a portion of the electric motor 202b of the fuel pump 101b according to the third embodiment. The electric motor 202b according to the third embodiment differs from the electric motor 202a according to the second embodiment in that the commutator 1a of the rotor 4b is attached to the commutator holder 11. FIG. The fuel pump 101b according to the third embodiment differs from the fuel pump 101a according to the second embodiment only in this respect.

As shown in FIG. 4, the commutator 1a is housed in a commutator holder 11 whose outer peripheral portion surrounding the commutator 1a protrudes from the commutator 1a in the direction of one side X2 in the axial direction by a dimension d. By arranging the commutator holder 11 in this way, even if the brush holder 7 collides with the rotor 4b, the contact surface of the commutator 1a can be protected. Since the outer peripheral portion of the commutator holder 11 collides with the brush holder before the contact surface of the commutator 1a contacts the brush holder 7, the contact surface of the commutator 1a is protected.

Consider the fourth distance L4, which is the distance in the axial direction X between the brush holder 7 and the outer peripheral portion of the commutator holder 11 in the configuration shown in FIG. Consider the relationship with the second distance L2, which is the amount of play in the axial direction X between the shaft 5a and the thrust bearing 8a. Contact between the commutator holder 11 and the brush holder 7 can be prevented by setting the relationship between the fourth distance L4 and the second distance L2 to satisfy L4>L2.

By setting the second distance L2, which is the amount of play in the axial direction X between the shaft 5a and the thrust bearing 8a, contact between the commutator holder 11 and the brush holder 7 can be suppressed. . Even when the rotor 4b of the electric motor 202b moves in the axial direction X, damage due to contact between the commutator holder 11 and the brush holder 7 is prevented, and abrasion powder due to sliding friction does not hinder current flow between the brushes 3 and the commutator 1a. can be made

<Amount of protrusion of the brush>
Here, the amount by which the brush 3 protrudes from the brush holder 7 will be examined. The commutator 1a is protected by a commutator holder 11, and the outer peripheral portion of the commutator holder 11 protrudes from the contact surface of the commutator 1a by a dimension d in the one side X2 direction in the axial direction. Therefore, it is conceivable that the brush 3 can be pulled into the brush holder 7 to a position where it protrudes from the brush holder 7 by the dimension d.

However, it is desirable that the brush 3 can be retracted into the brush holder 7 to the tip, and the brush can be housed in a state where the tip of the brush holder 7 and the brush 3 are on the same plane. Originally, the amount of movement of the shaft 5a is limited by the thrust bearing 8a. Further, the shaft 5a does not move to the one side X2 in the axial direction beyond the second distance L2, which is the amount of play of the thrust bearing 8a, and the commutator holder 11 does not come into contact with the brush holder 7. .

However, if the thrust bearing 8a fails and the axial movement cannot be restricted, it is assumed that the commutator holder 11 will come into contact with the brush holder 7 . In that case, it can be assumed that the outer peripheral portion of the commutator holder 11 rotates while contacting the brush holder 7 and wears due to sliding.

When the outer peripheral portion of the commutator holder 11 wears out and becomes flush with the contact surface of the commutator 1 , the commutator 1 comes into contact with the brush holder 7 . If the brush 3 can be accommodated in a state where the brush 3 is pulled into the brush holder 7 to the tip and the tip of the brush holder 7 and the tip of the brush 3 are on the same plane, the brush 3 can be accommodated in the brush holder 7. Electrical connection with the commutator 1 can be maintained.

When the brush 3 cannot be accommodated in the brush holder 7 up to the brush tip, the brush tip projects from the brush holder 7 and is fixed. At this time, it is conceivable that excessive force is applied to the tip of the protruding brush and the brush 3 is destroyed. If the brush can be housed in a state where the tip of the brush holder 7 and the brush 3 are on the same plane, the brush 3 can maintain electrical connection with the commutator 1 while being housed in the brush holder 7, and the fuel pump 101b can be maintained. is significant because it can maintain the minimum function for fuel supply.

It is not limited to the electric motor 202b according to the third embodiment that the brush holder 7 can accommodate the brush 3 in a state where the tip of the brush holder 7 and the brush 3 are on the same plane. The same can be said for the electric motors 202 and 202a according to the first and second embodiments.

It is necessary to consider the case where the movement restriction of the shafts 5, 5a by the thrust bearings 8, 8a is lost. When the brush 3 protrudes long from the brush holder 7 and slides on the commutator 1 while receiving a large pressing force, the brush 3 may be broken. If the tip of the brush 3 can be accommodated in the brush holder 7, such destruction can be avoided. Thereby, the function of the fuel pump can be maintained.

While this application describes various exemplary embodiments and examples, various features, aspects, and functions described in one or more embodiments may not apply to particular embodiments. can be applied to the embodiments singly or in various combinations. Accordingly, numerous variations not illustrated are envisioned within the scope of the technology disclosed herein. For example, modification, addition or omission of at least one component, extraction of at least one component, and combination with components of other embodiments shall be included.

Reference Signs List 1, 1a commutator 2 pressing member 3 brush 4, 4a, 4b rotor 5, 5a shaft 6, 6a radial bearing 7 brush holder 8, 8a thrust bearing 9 elastic body 11 commutator holder , 21 rotor core, 22 rotor winding, 25 stator, 101, 101a, 101b fuel pump, 201 pump chamber, 202, 202a, 202b electric motor, d dimension, Fb, Fs pressing force, L1 first distance, L2 second distance, L3 third distance, L4 fourth distance, X axial direction, X1 axial direction other side, X2 axial direction one side

Claims (7)

shaft,
a rotor core attached to the shaft and wound with a rotor winding; a disc-shaped commutator connected to the rotor winding and provided on one axial side of the rotor winding ; a commutator holder in which an outer peripheral portion that supports a commutator and surrounds the commutator protrudes from the commutator toward one side in the axial direction;
a brush facing the commutator and protruding toward the other side in the axial direction;
a brush holder that presses the brush against the commutator;
a radial bearing that radially supports the shaft;
a brush holder side thrust bearing that supports the shaft from the brush holder side to the other side in the axial direction;
A first distance, which is the axial distance between the brush holder and the commutator, is greater than a second distance, which is the amount of axial play between the shaft and the brush-holder-side thrust bearing. and a fourth distance, which is an axial distance between the brush holder and the outer peripheral portion of the commutator holder, is greater than the second distance. shaft,
A rotor core attached to the shaft and wound with a rotor winding, and a disc-shaped commutator connected to the rotor winding and provided on one side in the axial direction of the rotor winding. a rotor having a
a brush facing the commutator and protruding toward the other side in the axial direction;
a brush holder that presses the brush against the commutator;
a radial bearing that radially supports the shaft;
a brush holder side thrust bearing supported on the other side in the axial direction from the brush holder side by an elastic body that axially presses the shaft in the direction in which the brush is pressed against the commutator by the brush holder;
A first distance, which is the axial distance between the brush holder and the commutator, is greater than a second distance, which is the amount of axial play between the shaft and the brush-holder-side thrust bearing. An electric motor characterized by : 3. The electric motor according to claim 2 , wherein the pressing force of said elastic body is greater than the pressing force with which said brush holder presses said brush against said commutator. shaft,
A rotor core attached to the shaft and wound with a rotor winding, and a disc-shaped commutator connected to the rotor winding and provided on one side in the axial direction of the rotor winding. a rotor having a
a brush facing the commutator and protruding toward the other side in the axial direction;
a brush holder that presses the brush against the commutator;
a radial bearing that radially supports the shaft;
a brush holder side thrust bearing that axially supports the shaft from the brush holder side to the other side in the axial direction;
A first distance, which is the axial distance between the brush holder and the commutator, is larger than a second distance, which is the amount of axial play between the shaft and the brush-holder-side thrust bearing. The electric motor according to claim 1, wherein the brush holder can accommodate the brush in a state in which the tip of the brush holder and the brush are on the same plane. 5. The electric motor according to any one of claims 1 to 4, wherein the electric motor is used with its surroundings and inside immersed in fuel. The electric motor according to any one of claims 1 to 5, wherein the commutator has a contact surface with the brush made of sintered carbon. A fuel pump comprising the electric motor according to any one of claims 1 to 6.

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