JP2862057B2 - Electric pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric pump having a circulating cooling structure in a motor.

[0002]

2. Description of the Related Art FIG. 17 is a sectional view in the axial direction showing a conventional electric pump having a circulating cooling structure in a motor.
Is a stator composed of a stator core 3 wound with a stator winding 2 and a lead wire 4, and 5 is an extremely thin non-magnetic cylindrical stator can mounted on the inner diameter of the stator core 3. The frame 8 holds the stator 1 with O-rings 6 and 7 at both ends.
The brackets 9 and 10 are in contact with the ends 9 and 10 in a watertight manner, and the stator chamber is constituted by the stator can 5 and the frame 8 and the brackets 9 and 10, and is completely isolated from the rotor chamber. 11 is a rotor core 12 and a rotor conductor 1
3, which is fitted to the motor shaft 14 having an axial through hole 14a at the center by shrinkage fitting or the like. Reference numeral 15 denotes a rotor can made of a non-magnetic cylinder fitted to the outer periphery of the rotor 11, and both ends thereof are water-tightly joined to a rotor side plate 16 fitted to the motor shaft 14 by shrink fitting or the like. Reference numerals 17 and 18 denote sleeve bearings mounted on the brackets 9 and 10, respectively, which rotatably support the motor shaft 14. Reference numeral 19 denotes a thrust bearing mounted on the bracket 9, which supports an axial load acting on the motor shaft 14 via a thrust disc 20 fitted on the motor shaft 14.
Reference numeral 21 denotes a pump impeller which is fixed to a portion of the motor shaft 14 extending to the pump chamber by a nut 22; 23, a pump casing which abuts on the bracket 9 to form a pump chamber 24; A water passage communicating with the slave chamber 26, a water passage 27 communicating the rear rotor chamber 28 and the through hole 14a of the motor shaft 14, and an orifice or a constant flow valve 29 provided in the water passage 25 are provided. It is a flow control device.

Next, the operation will be described. Pump room 24
When the impeller 21 inside rotates at high speed, the pump chamber 24
A part of the pump handling liquid whose pressure has been increased by the bracket 9
Through the water passage hole 25 into the front rotor chamber 26 and then through the gap between the stator can 5 and the rotor can 15 to the rear rotor chamber 28, from which the water passage hole 27 of the bracket 10 passes.
Through the through hole 14a of the motor shaft 14 and returns from the opening at the tip on the pump side to the suction side (low pressure side) of the pump chamber 24. By circulating the handled liquid into the motor using the pressure difference between the discharge side and the suction side of the pump chamber 24 in this manner,
Motor cooling and bearing lubrication are performed. Here, the flow control device 29 provided in the circulation path of the cooling water is provided so that the circulation flow rate is excessively larger than the flow rate required for cooling the motor, particularly when the pump is operated in a high pressure region and the pressure difference between the discharge side and the suction side is large. It is installed for the purpose of preventing lowering of pump efficiency and generation of noise due to water flow.

[0004]

Since the conventional electric pump having the cooling structure in circulation in the motor is constructed as described above, the circulation flow rate in the motor depends on the pressure when the pump is used and the characteristics of the flow rate adjusting device 29. Decided. In particular, since the pump operating pressure varies depending on the installation location and the amount of water adjusted by a valve, it is impossible to maintain a constant circulation flow rate. For example, when the cooling flow rate (circulation flow rate) required for the continuous operation of the motor is 1.5 l / min, if the orifice A is installed as shown in FIG.
/ Cm ² or more, and a pressure of 6
When operated at kgf / cm ² , the cooling flow rate is 3 l / min, which is larger than the required flow rate. Similarly, if the orifice B is installed, the pump discharge pressure will be 1.0 kgf /
cm ² or more, and at a pressure of 6 kgf / cm ² , 4.
It becomes 1 l / min. If the constant flow valve C is installed, the pressure needs to be 0.6 kgf / cm ² or more, and the pressure is 6 kgf / cm ^2.
In cm ² , it is 2.5 l / min.

As described above, in both the orifice and the constant flow valve, there is a region where the circulating flow does not satisfy the flow required for cooling under the use condition where the pump discharge pressure is low, and the discharge pressure is low and the discharge flow is large. Under operating conditions, the pump load is generally overloaded and adverse conditions overlap. Therefore, the temperature rise of the motor is increased, and the life is remarkably shortened, and a motor burnout accident occurs. Further, in the high-pressure region, although there is an effect of restricting the circulation flow rate from becoming excessive, it is still inevitable that the circulation flow rate becomes larger than the required flow rate, and there is a problem that the pump efficiency is reduced.

The noise due to the water flow in the high-pressure region is considerably lower as a whole when the flow control device 29 is installed than when it is not installed. There was a problem that generation could not be prevented.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and always maintains a constant circulating flow rate without being affected by the operating pressure of a pump, further reduces noise caused by water flow, and achieves high efficiency. Another object of the present invention is to obtain a long-life and highly reliable electric pump with low noise and no danger of abnormal temperature rise.

Further, the present invention uses a corrosion-resistant aluminum alloy as the material of the bracket and has an insulating structure so that the bracket and the can and the bracket and the rotor are not electrically connected to each other. The purpose is to obtain a lightweight electric pump.

[0009]

According to a first aspect of the present invention, there is provided an electric pump , wherein a concave portion is provided in an inner wall portion of a pump chamber on a motor side,
The partition member attached to the motor shaft is fitted into this recess.
And make the radial fitting gap narrow, and fit this fitting gap
To introduce the motor cooling water into the motor
Of the water passage hole for introducing the pump handling liquid from the pump chamber into the motor
Near the inlet, the handling liquid enters the motor shaft side.
Is provided .

In the electric pump according to the second aspect of the present invention, a concave portion is provided in the inner wall portion of the pump chamber on the motor side, and a partition member mounted on the motor shaft is fitted into the concave portion, and the radial fitting gap is narrowed. The cooling water is introduced into the motor through this fitting gap, and the partition member is disc-shaped.
The partition member has a disk-shaped outer peripheral portion provided with irregularities .

The electric pump according to the third aspect of the present invention has a structure in which the bracket is made of a corrosion-resistant aluminum alloy and has an insulating structure so that the bracket and the can and the bracket and the rotor are not electrically connected.

[0012]

According to the first aspect of the present invention, foreign matter is transferred to the rotor chamber.
Intrusion can be prevented and the radial fitting gap
Can be prevented from being blocked.

According to the second aspect of the present invention, it is possible to prevent foreign matter from entering the rotor chamber and to prevent the radial fitting gap from being blocked by the foreign matter.

According to the third aspect of the invention, since the bracket using the corrosion-resistant aluminum alloy and the can and the rotor using dissimilar metals such as stainless steel and copper alloy are insulated so as not to be electrically connected to each other, Contact corrosion (electrolytic corrosion) of corrosion resistant aluminum alloy can be prevented.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments, reference examples will be described below.
1 to 7 will be described. Reference Example 1. Reference Example 1 will be described with reference to FIGS. FIG. 1 is a sectional view in the axial direction, and FIG. 2 is a sectional view taken along line II-II in FIG. In the figure, reference numeral 14A denotes an axial hole which does not penetrate to the pump-side tip of the motor shaft 14 and stops between the impeller 21 and the pump chamber 24. Reference numeral 30 denotes a hole provided in the axial hole 14A near the stop portion. A radial hole 31 that communicates with the discharge side of the pump chamber 24 is a water hole that communicates the suction side and the discharge side of the impeller 21. The number and diameter of the holes 30 in the radial direction are determined by the circulation flow rate.

In the electric pump configured as described above, the water passage hole 25 for introducing cooling water into the motor and the radial hole 30 of the motor shaft 14 for returning cooling water to the pump chamber 24 have the same pump discharge portion. , There is no pressure difference and no circulating flow in the motor is generated. Only the pressure generated by the pumping action of the radial holes 30 generates a circulating flow. Therefore, this pressure is determined to be an optimum value so as to match the flow rate required for cooling the motor, and is unchanged as long as the rotation speed of the pump does not change, and the circulation flow rate is also unchanged.

Reference Example 2 In the above reference example 1, as shown in FIG.
If a water passage hole 31 is provided in 1, a part of the handling liquid on the pump discharge side generates a flow returning to the suction side of the impeller 21 as shown by an arrow 32, so that the temperature of the cooling water introduced into the motor is reduced. The rise can be prevented. This is especially true for bracket 9
This is effective when the gap between the motor and the impeller 21 is small.

Reference Example 3 In the above-described reference example, the radial hole 30 is provided in the motor shaft 14, and the pressure generated by the pump action is reduced by the radial hole 3.
It is determined by the diameter of the 0 part shaft. Therefore, when it is necessary to further increase the pump pressure, increase the shaft diameter or provide a ring 33 at the position of the radial hole 30 as shown in FIGS.
A hole 34 communicating with the radial hole 30 of No. 4 may be provided.
Further, in addition to the ring 33, an impeller 33A may be disposed as shown in FIG. 5 as means for creating a negative pressure in the vicinity of the radial hole 30, and water is discharged from the radial hole 30 by the impeller. Can be encouraged.

Reference Example 4 Further, when it is desired to increase the circulation flow rate by increasing the pressure generated by the pump action, an auxiliary impeller 35 may be provided in the front rotor chamber 26 as shown in FIG. In FIG. 6, the auxiliary impeller 35 is integrated with the thrust disk 20 fitted to the motor shaft 14, and the suction port thereof communicates with the water hole 25 of the bracket 9.

Reference Example 5 In the above-described reference example 4, the auxiliary impeller 35 in the motor has a structure integrated with the thrust disk 20, but the same effect can be obtained by integrating it with the rotor side plate 16 as shown in FIG. In FIG. 7, the auxiliary impeller 36 is the motor shaft 14.
And a suction side thereof communicates with a water passage hole 25 of the bracket 9.

Reference Example 6 In the above reference examples 4 and 5, the auxiliary impeller 35 in the motor is used.
Although 36 is integrated with the thrust disk 20 or the rotor side plate 16, a similar effect can be obtained by providing a spiral groove (screw) on the outer periphery of the thrust disk 20 as shown in FIG. In FIG. 8, the auxiliary impeller 37 has a spiral groove (screw) provided on the outer peripheral portion of the thrust disk 20 fitted on the motor shaft 14, but the spiral impeller 37 has a spiral groove (screw) on the outer periphery of the rotor side plate 16. ) May be provided.

Reference Example 7 In the above-described reference example 6, the auxiliary impeller 37 in the motor is a spiral groove (screw) provided on the outer periphery of the thrust disk 20. However, as shown in FIG. The same effect can be obtained with the auxiliary impeller 38 provided.

An embodiment of the present invention will be described below. Embodiment 1 FIG . One embodiment of the invention according to claim 1 will be described with reference to FIG. FIG. 10 is an axial cross-sectional view, in which the same or corresponding parts as those in the first to seventh embodiments are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 39 denotes a concave portion provided on the motor-side inner wall portion of the pump chamber 24, that is, the bracket 9;
And is formed by extending the outer peripheral wall of the ring 33. Reference numeral 41 denotes a radial fitting gap of a narrow gap formed between the outer periphery of the partition member 40 and the recess 39.

With such a configuration, the partition member 4
With the rotation of 0 and slight movement in the axial direction, the radial fitting gap 41 serves as a fixed filter,
There is no need to install a filter in the water passage hole 25, and there is no possibility of clogging of the filter. That is, the partition member 4
The rotation of 0 moves the foreign matter in the radial direction, thereby preventing the foreign matter smaller than the gap 41 from entering.

Embodiment 2 FIG. In the first embodiment, the radial fitting gap 41 is set to 0.05
When the distance is set to 0.7 mm, it is possible to prevent foreign substances that cannot pass through the motor gap from entering and prevent the partition member 40 from contacting. Therefore, problems such as restriction of the rotor 11 and damage and breakage of the can 5 can be eliminated, and the filter effect can be improved.

Embodiment 3 FIG. In the first embodiment, if the depth of the radial fitting gap 41 is set to 2 mm or less, an increase in the passage resistance of the circulating cooling water in the motor can be prevented (a motor temperature increase due to a decrease in the amount of cooling water can be prevented). In particular, a great effect of preventing the passage resistance from increasing due to the adhesion of water deposits and the like during long-term use can be obtained. Also, since the passage resistance is small, the radial gap 4
There is also an effect that 1 can be reduced.

Embodiment 4 FIG. In the first embodiment, if the concave portion 39 is formed as a through hole and the partition member 40 is formed in a disk shape, there is obtained an effect that the structure is simplified and the device can be manufactured at low cost.

Embodiment 5 FIG. In the first embodiment, the partition member 40 and the impeller 2
Integrating 1 with one can reduce the number of parts, and thus has the effect of simplifying the structure and saving space.

Embodiment 6 FIG. In the first embodiment, when the partition member 40 is made of the same material as the pump chamber forming member, an effect of preventing electrolytic corrosion can be obtained.

Embodiment 7 FIG. In the first embodiment, if the partition member 40 is made of resin, there is no restraint due to corrosion and rust does not enter, so that the effect of reducing cost and weight can be obtained.

Embodiment 8 FIG. In the first embodiment, by providing the blocking portion 42 formed by unevenness near the inlet of the water hole 25, the pump handling liquid in the pump chamber 24 enters the motor shaft side without entering the water hole 25. Therefore, it is possible to prevent the cooling water and the foreign matter from staying, to achieve sanitary effects, and to prevent the growth of the foreign matter (increase in the size of the foreign matter).

Embodiment 9 FIG. In the first embodiment, as shown in FIG. 11, the effect of preventing clogging can be enhanced by providing the irregularities 43 on the disk-shaped outer peripheral portion of the partition member 40.

Embodiment 10 FIG. In the first to ninth embodiments, the water passage hole 25 and the radial fitting gap 4
12 are substantially on the same circumferential line, but if the radial fitting gap 41 is shifted in the outer circumferential direction as shown in FIG.
Can be changed.

Embodiment 11 FIG. One embodiment of the invention according to claim 3 will be described with reference to FIG. FIG. 13 is a cross-sectional view in the axial direction. The same or corresponding parts as those of the related art are denoted by the same reference numerals, and description thereof is omitted. The difference from the conventional one is that a resin pipe is attached to the outer periphery of the stator core 3 or an insulating member 44 such as a resin coating is applied to the frame 8 so that the frame 8 has a double insulating structure and the sleeve bearings attached to the brackets 9 and 10. 17,
18 and the thrust bearing 19 are made of an insulating material such as resin or ceramic, and the materials of the brackets 9 and 10 are made of a corrosion-resistant aluminum alloy.

In the canned motor constructed as described above, even if the brackets 9 and 10 and the can 5 come into contact with each other in the cooling water, the next closed circuit in which the corrosion current flows is provided on the outer periphery of the stator core 3. Since it can be cut off by the insulating member 44, contact corrosion (electric corrosion) of the brackets 9 and 10 using a corrosion-resistant aluminum alloy can be prevented. (Closed circuit 1 through which corrosion current flows) Bracket 9 or 10 → Frame 8 → (Insulating member 44
) → Stator core 3 → Can 5 → Cooling water → Bracket 9 or 10

Even if the brackets 9 and 10 and the rotor 11 come into contact with each other in the cooling water, the next closed circuit 2 in which a corrosion current flows is provided.
And 3 can be interrupted by the insulating bearing material,
Contact corrosion (electric corrosion) of the brackets 9 and 10 can be prevented. (Closed circuit 2 in which corrosion current flows) Bracket 9 → radial bearing 17 (cut off by using an insulated bearing) →, bracket 9 → thrust bearing 19 (cut off by using an insulated bearing) → thrust disc 20 →, Motor shaft 14 (above) → rotor core 12 and rotor side plate 16 → rotor can 15 → cooling water → bracket 9 (closed circuit 3 in which corrosion current flows) bracket 10 → radial bearing 18 (insulating bearing and ) → motor shaft 14 → rotor core 12 and rotor side plate 16 → rotor can 15 → cooling water → bracket 10

Embodiment 12 FIG. In the eleventh embodiment, the insulating member 44 is provided on the outer periphery of the stator core 3.
The frame 8 is made of aluminum, the inner diameter of the frame is subjected to an alumite treatment as an insulating film, and the film thickness is set to 10 μm or more, so that the can 5 and the brackets 9 and 10 are formed. It is possible to cut off the corrosion current during this period, and it is possible to achieve the same effects as in the eleventh embodiment.

Embodiment 13 FIG. In the eleventh embodiment, the insulating member (layer) 44 is provided between the frame 8 and the stator core 3. However, as shown in FIG. 45 and tightening bolt 4
By interposing the insulating washer 47 under the neck of 6, the corrosion current between the can 5 and the brackets 9, 10 can be cut off, and the same effect as in the eleventh embodiment can be obtained.

Embodiment 14 FIG. In Embodiment 13 , the insulating gasket 45 is interposed between the mating surfaces of the frame 8 and the brackets 9 and 10, but the surfaces of the brackets 9 and 10 (including the mating surfaces of the frames) are subjected to an alumite treatment as an insulating film. By setting the film thickness to 10 μm or more, the same effect as the insulating gasket 45 of the thirteenth embodiment can be obtained.

Embodiment 15 FIG. In the eleventh embodiment, the case where the corrosion current between the brackets 9 and 10 and the rotor 11 is interrupted by the insulating bearing material is shown. However, as shown in FIG. 15, the materials of the sleeve bearings 17 and 18 and the thrust bearing 19 are changed. The same effect can be obtained by using a conductive material such as a copper alloy and applying an insulating member 48 to the outer periphery of the sleeve bearings 17 and 18 and interposing an insulating member 49 between the thrust bearing 19 and the bracket 9.

Embodiment 16 FIG. In the eleventh embodiment, the case where the corrosion current between the brackets 9 and 10 and the rotor 11 is interrupted by the insulating bearing material has been described. However, the sleeve bearings 17 and 18 and the thrust bearing 1 are described.
The same effect can be obtained by using 9 as a conductive material such as a copper alloy and using the shaft 14 and the thrust disk 19 constituting the rotor 11 as insulating ceramic materials or the like.

Embodiment 17 FIG. In the above-described embodiment 16 , the shaft 14 constituting the rotor 11 is made of an insulating ceramic or the like.
Similar effects can be obtained by mounting or coating an insulating sleeve such as ceramic on the portions 17a and 18a of the shaft 14 that slide with the sleeve bearings 17 and 18 as shown in FIG.

[0043]

This abnormal temperature in the pump working pressure is low pressure region for according to the pump reference example always without affected by the working pressure of the pump can maintain a constant optimal circulation flow rate of the invention, according to the present invention There is no danger of rising, and the pump operating pressure does not allow excessive circulating water to flow even in the high water pressure range, so that high efficiency, low noise, no risk of abnormal temperature rise, and long life and high reliability can be obtained. There is.

[0044] According to this invention a partition member mounted on the motor shaft fitted in the recess, by introducing motor cooling water through the radial fitting gap between the partition member and the recess, the filter is not necessary In addition, the effect that there is no possibility of clogging is obtained.

Further, according to the present invention, the material of the bracket, which accounts for a large proportion of the total cost of the motor, is made of a corrosion-resistant aluminum alloy. Since it is small, it is possible to reduce the weight of the product, and there is an effect that an inexpensive and high-quality product can be obtained.

[Brief description of the drawings]

1 is an axial cross sectional view showing a reference example 1 of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

Figure 3 is an axial cross-sectional view showing a reference example 3 of the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

Figure 5 is an axial cross-sectional view illustrating a different reference example 3 of this invention.

6 is an axial cross sectional view showing a reference example 4 of the present invention.

7 is an axial cross sectional view showing a reference example 5 of the present invention.

8 is an axial cross sectional view showing a reference example 6 of the present invention.

9 is an axial cross sectional view showing a reference example 7 of the present invention.

FIG. 10 is an axial sectional view showing Embodiment 1 of the present invention.

FIG. 11 is a sectional view of a main part showing Embodiment 9 of the present invention.

FIG. 12 is an axial sectional view showing Embodiment 10 of the present invention.

FIG. 13 is an axial sectional view showing an eleventh embodiment of the present invention.

FIG. 14 is an axial sectional view showing Embodiment 13 of the present invention.

FIG. 15 is an axial sectional view showing Embodiment 15 of the present invention.

FIG. 16 is an axial sectional view showing Embodiment 17 of the present invention.

FIG. 17 is an axial sectional view showing a conventional electric pump.

18 is a diagram illustrating a characteristic example of the flow rate adjusting device in FIG. 17;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator 9 Bracket 10 Bracket 11 Rotor 14 Motor shaft 14A Axial hole 15 Rotor can 16 Rotor side plate 20 Thrust disk 21 Pump impeller 24 Pump room 25 Water hole 26 Front rotor room 27 Water hole 28 Rear rotor chamber 30 Radial hole 31 Water passage hole 33 Ring 34 Ring hole 35 Auxiliary impeller 36 Auxiliary impeller 37 Auxiliary impeller 38 Auxiliary impeller 39 Recess 40 Partition member 41 Radial fitting gap 42 Inhibitor 43 Irregularity 44 Insulation Member 45 Insulating gasket 48 Insulating member 49 Insulating member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification symbol FI H02K 9/19 H02K 9/19 Z (58) Field surveyed (Int.Cl. ⁶ , DB name) F04D 13/06 H02K 1 / 32 H02K 5/128 H02K 5/20 H02K 9/19

Claims (11)

(57) [Claims] 1. A motor circulation system in which a part of the pump handling liquid is introduced into the motor as motor cooling water, and the cooling water passing through the gap of the motor is returned to the pump chamber through a hole formed in the motor shaft in the axial direction. In the electric pump having a cooling system, a concave portion is provided in the inner wall portion of the pump chamber on the motor side, a partition member mounted on the motor shaft is fitted into the concave portion, and a radial fitting gap is a narrow gap, The motor cooling water is introduced into the motor through the fitting gap,
An electric pump provided with a blocking part near an inlet of a water passage hole for introducing a pump handling liquid from a pump chamber into a motor, for preventing the pump handling liquid from entering the motor shaft side. 2. A motor in which a part of a pump handling liquid is introduced into the motor as motor cooling water, and the cooling water having passed through the gap of the motor is returned to the pump chamber through a hole formed in the motor shaft in the axial direction. In the electric pump having a circulating cooling structure, a recess is provided in the inner wall portion of the pump chamber on the motor side, and a partition member mounted on the motor shaft is fitted into the recess, and the radial fitting gap is a narrow gap. An electric pump, wherein the motor cooling water is introduced into the motor through the fitting gap, the partition member is formed in a disk shape, and irregularities are provided on an outer peripheral portion of the disk shape of the partition member. 3. A stator core with a coil wound around the inner diameter of the frame is mounted, and a can made of ultra-thin non-magnetic stainless steel is provided on the inner diameter of the stator core. The can separates the stator chamber and the rotor chamber. An electric pump in which a bracket is provided at both ends of the frame, the bearing being provided with bearings for rotatably supporting the rotor, and the cooling water is sealed or forcedly circulated in the rotor chamber. And
An electric pump having an insulating structure so that the bracket and the can and the bracket and the rotor are not electrically connected to each other. 4. The electric pump according to claim 3, wherein an insulating resin pipe is attached to the outer periphery of the stator core or a resin coating or the like is applied, and the frame has a double insulating structure. 5. The frame is made of aluminum, an alumite film having a thickness of 10 μm or more is formed on the inner diameter of the frame, and the frame has a double insulating structure.
Electric pump. 6. An alumite film having a thickness of 10 μm or more is formed on a surface of a bracket made of a corrosion-resistant aluminum alloy, and an insulating washer is interposed under a neck of a bolt for fastening the bracket to a frame. Item 3
Electric pump. 7. The electric pump according to claim 3, wherein an insulating gasket is interposed between the mating surfaces of the frame and the bracket. 8. The electric pump according to claim 3, wherein a material of the bearing mounted on the bracket is an insulating material such as resin or ceramic. 9. The electric pump according to claim 3, wherein a bearing material mounted on the bracket is made of a conductive material such as a copper alloy, and an insulating member is interposed between the bracket and the bearing material. 10. A bearing material mounted on the bracket is made of a conductive material such as a copper alloy, and a shaft of a rotor and a thrust disk sliding with the bearing are made of an insulating ceramic or the like. 3 electric pump. 11. A bearing material to be mounted on the bracket is made of a conductive material such as a copper alloy, and an insulating sleeve is mounted or a ceramic coating is applied to a shaft of a rotor that slides with the bearing, and a thrust disk is made of an insulating material. The electric pump according to claim 3, wherein the electric pump is made of ceramic or the like.