JPH0626491A - Electrically driven pump - Google Patents

Abstract

PURPOSE:To provide an electrically driven pump in which a constant circulating flow amount is maintained at all times without being influenced by a pressure used in a pump, and noise generated by water flow is reduced and high efficiency, a long life, high reliability can be provided without having any dangerous property for increasing a temperature abnormally. CONSTITUTION:A radial direction hole 30 for communicating the hole 14A in the axial direction of a motor shaft 14 with a pump chamber 24, is provided in the motor shaft 14 positioned in the vicinity of a passage for leading cooling water from the pump chamber 24 into a motor, and the pump side top end part of the hole 14A in axial direction is sealed in blind condition.

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 system in a motor.

[0002]

2. Description of the Related Art FIG. 16 is an axial sectional view showing an electric pump of a conventional circulating cooling system in a motor.
Is a stator composed of a stator core 3 around which the stator winding 2 is wound 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 that holds the stator 1 by O-rings 6 and 7 at both ends
Watertightly contact with the brackets 9 and 10 that contact both ends of the stator, and the stator can 5, the frame 8 and the brackets 9 and 10 form a stator chamber, which is completely isolated from the rotor chamber. 11 is a rotor core 12 and a rotor conductor 1
The rotor is composed of 3 and is fitted to the motor shaft 14 having a through hole 14a in the axial direction at the center by shrinkage fitting or the like. Reference numeral 15 denotes a non-magnetic cylindrical rotor can fitted on the outer periphery of the rotor 11, and both ends thereof are watertightly joined to a rotor side plate 16 fitted to the motor shaft 14 by shrinkage fitting or the like. Sleeve bearings 17 and 18 are mounted on the brackets 9 and 10, respectively, and 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 fixed to a portion of the motor shaft 14 extending to the pump chamber by a nut 22. Reference numeral 23 denotes a pump casing that abuts the bracket 9 to form a pump chamber 24. Reference numeral 25 denotes a front rotation of the pump chamber 24 and the pump casing. A water passage hole communicating the sub chamber 26, a water passage hole 27 communicating the rear rotor chamber 28 and the through hole 14a of the motor shaft 14, and 29 an orifice provided in the water passage hole 25 or a constant flow valve. It is a flow rate adjusting device.

Next, the operation will be described. Pump room 24
When the impeller 21 inside rotates at high speed, the pump chamber 24
Bracket 9 is used for a part of the pump handling liquid whose pressure is increased by
Through the water passage hole 25 in the front rotor chamber 26, then through the gap between the stator can 5 and the rotor can 15 to reach the rear rotor chamber 28, and from here, the water passage hole 27 in the bracket 10.
Through the through hole 14a of the motor shaft 14 and returns to the suction side (low pressure side) of the pump chamber 24 from the opening at the tip on the pump side. In this way, by utilizing the pressure difference between the discharge side and the suction side of the pump chamber 24 to circulate the handled liquid in the motor,
The motor is cooled and the bearings are lubricated. Here, the flow rate adjusting device 29 provided in the circulation passage of the cooling water makes the circulation flow rate excessively larger than the flow rate required for cooling the motor, especially when the pump is operated in the 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 the deterioration of the pump efficiency and the generation of noise due to water flow.

[0004]

Since the conventional electric pump having the circulating cooling system in the motor is constructed as described above, the circulating 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 working pressure changes depending on the installation location and the amount of water adjusted by the valve, it is impossible to maintain a constant circulating flow rate. For example, when the cooling flow rate (circulation flow rate) required for continuous operation of the motor is 1.5 l / min, if the orifice A is installed as shown in FIG. 17, the pump discharge pressure is 1.5 kgf.
/ Cm ² or more and the pressure in the high pressure region is 6
When operated at kgf / cm ² , the cooling flow rate is 3 l / min, which is higher than the required amount. Similarly, if the orifice B is installed, the pump discharge pressure will be 1.0 kgf /
cm ² or more is required, 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.
It becomes 2.5 l / min in cm ² .

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

Further, the noise due to the water flow in the high-pressure region is considerably lower in the case where the flow rate adjusting device 29 is installed as compared with the case where it is not installed, but the noise in this part is reduced in order to narrow the water flow in the flow rate adjusting device part. There was a problem that it could not be prevented.

The present invention has been made in order to solve the above-mentioned problems, and maintains a constant circulating flow rate without being affected by the working pressure of the pump, further reduces noise due to water flow, and has high efficiency. The purpose is to obtain a long-life and highly reliable electric pump that is low in noise and free from the risk of abnormal temperature rise.

Further, according to the present invention, the material of the bracket is a corrosion-resistant aluminum alloy, and the bracket and the can and the bracket and the rotor have an insulating structure so as not to be 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 in which a radial hole that connects an axial hole of a motor shaft with a pump chamber is provided near a cooling water introducing portion from the pump chamber into the motor. Is provided on the motor shaft and the pump-side tip of the axial hole is closed by a blind hole.

In the electric pump according to the invention of claim 5, 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 in the recess, and the radial fitting gap is narrowed. A gap is provided, and the motor cooling water is introduced into the motor through the fitting gap.

According to the fourteenth aspect of the present invention, the electric pump has a bracket 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 invention, the radial hole of the motor shaft performs a pumping action, and a constant circulating flow can be generated in the motor.

According to the fifth aspect of the present invention, it is possible to always maintain a constant optimum circulation flow rate without being affected by the working pressure of the pump.

In the fourteenth aspect of the present invention, since the bracket using the corrosion-resistant aluminum alloy and the can and the rotor using different metals such as stainless steel and copper alloy have an insulating structure so as not to be electrically connected, It is possible to prevent contact corrosion (electrolytic corrosion) of the corrosion resistant aluminum alloy.

[0015]

【Example】

Example 1. 1 and 2 showing an embodiment of the invention according to claim 1.
Will be described. 1 is an axial sectional view, and FIG. 2 is a sectional view taken along the line II-II in FIG. 1. The same or corresponding parts as those of the conventional device are designated by the same reference numerals and the description thereof will be omitted. In the figure, 14A is an axial hole that does not penetrate to the pump-side tip of the motor shaft 14 and stops with the impeller 21 that exits into the pump chamber 24, and 30 is provided in the vicinity of the stop portion of the axial hole 14A. A radial hole communicating with the discharge side of the pump chamber 24 and a water passage hole 31 communicating with the suction side and the discharge side of the impeller 21. The number of holes 30 in the radial direction and the hole diameter are determined by the circulation flow rate.

In the electric pump constructed as described above, the water passage hole 25 for introducing the cooling water into the motor and the radial hole 30 of the motor shaft 14 for returning the cooling water to the pump chamber 24 have the same pump discharge portion. Since there is no pressure difference, a circulating flow in the motor is not generated. It is only the pressure due to the pumping action of the radial holes 30 that creates the circulating flow. Therefore, this pressure is determined to be an optimum value to match the flow rate required for cooling the motor, and is constant unless the rotational speed of the pump is changed, and the circulation flow rate is also unchanged.

Example 2. In the first embodiment described above, when the impeller 21 is provided with the water passage hole 31 as shown in FIG. 1, a part of the liquid handled on the pump discharge side is allowed to flow back to the suction side of the impeller 21 as shown by an arrow 32. Since it is generated, the temperature of the cooling water introduced into the motor can be prevented from rising. This is particularly effective when the gap between the bracket 9 and the impeller 21 is small.

Example 3. In the above embodiment, the radial hole 30 is provided in the motor shaft 14, and the pressure generated by the pump action is determined by the diameter of the shaft of the radial hole 30. Therefore, when it is necessary to further increase the pump pressure, the shaft diameter is increased, or a ring 33 is provided at the position of the radial hole 30 as shown in FIGS. The hole 34 communicating with the hole 30 in the radial direction may be provided.

Example 4. Further, when it is desired to increase the pressure generated by the pump action to increase the circulation flow rate, an auxiliary impeller 35 may be provided inside the front rotor chamber 26 as shown in FIG. In FIG. 5, the auxiliary impeller 35 is integrated with the thrust disc 20 fitted to the motor shaft 14, and its suction port communicates with the water passage hole 25 of the bracket 9.

Example 5. In the fourth embodiment, the auxiliary impeller 35 in the motor has a structure integrated with the thrust disc 20, but the same effect can be obtained even if it is integrated with the rotor side plate 16 as shown in FIG. In FIG. 6, the auxiliary impeller 36 is integrated with the rotor side plate 16 fitted to the motor shaft 14, and the suction side thereof is the water passage hole 2 of the bracket 9.
It communicates with 5.

Example 6. In the fourth and fifth embodiments described above, the auxiliary impellers 35 and 36 in the motor are integrated with the thrust disc 20 or the rotor side plate 16. However, as shown in FIG. ), The same effect can be obtained. In FIG. 7, the auxiliary impeller 3
Reference numeral 7 shows a thrust disc 20 fitted to the motor shaft 14 provided with a spiral groove (screw) on the outer peripheral portion thereof, but a spiral groove (screw) may be provided on the outer periphery of the rotor side plate 16. .

Example 7. In the sixth embodiment, the auxiliary impeller 37 in the motor is a spiral groove (screw) provided on the outer periphery of the thrust disc 20, but as shown in FIG. 8, a helical groove like a helical gear is formed on the outer periphery of the thrust disc 20. The same effect can be obtained even with the auxiliary impeller 38 provided.

Example 8. An embodiment of the invention according to claim 5 will be described with reference to FIG. FIG. 9 is an axial sectional view,
The same or corresponding parts as those of the first to seventh embodiments are designated by the same reference numerals and the description thereof will be omitted. In the figure, 39 is the pump chamber 2
4 is a motor-side inner wall portion, that is, a concave portion provided in the bracket 9, and 40 is a partition member fitted in the concave portion 39.
3 is formed by extending the outer peripheral wall portion. Reference numeral 41 denotes a radial fitting gap of a slit formed between the outer periphery of the partition member 40 and the recess 39.

With this structure, the partition member 4
With the rotation of 0 and a 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
By rotating 0, the foreign matter is moved in the radial direction to prevent the foreign matter smaller than the gap 41 from entering.

Example 9. In the eighth embodiment, if the radial fitting gap 41 is set to 0.05 to 0.7 mm, foreign matter that cannot pass through the motor gap can be prevented from entering and the partition member 40 can be prevented from contacting. Therefore rotor 1
Problems such as restraint of No. 1 and scratches and breakage of the can 5 can be solved, and the filter effect can be improved.

Example 10. In the eighth embodiment, when the depth of the radial fitting gap 41 is set to 2 mm or less, the passage resistance of the circulating cooling water in the motor can be prevented from increasing (the motor temperature can be prevented from rising due to the reduction of the cooling water amount).
In particular, it has a great effect of preventing an increase in passage resistance due to adhesion of water stain or the like when used for many years. Further, since the passage resistance is small, there is an effect that the radial gap 41 can be reduced.

Embodiment 11. In the eighth embodiment, when the recess 39 is formed as the through hole and the partition member 40 is formed in the disk shape, the structure is simplified and the manufacturing cost can be reduced.

Example 12 In the eighth embodiment, if the partition member 40 and the impeller 21 are integrated, the number of parts can be reduced, so that the structure can be simplified and the space can be saved.

Example 13 In the eighth embodiment, if the partition member 40 is made of the same material as the pump chamber forming member, the effect of preventing electrolytic corrosion can be obtained.

Example 14 In the eighth embodiment, if the partition member 40 is made of resin, there is no restraint due to corrosion and no invasion of rust, so that it is possible to obtain the effects of low cost and light weight.

Example 15 In the eighth embodiment, by providing the blocking portion 42 formed by the unevenness near the inlet of the water passage hole 25, the pump handling liquid in the pump chamber 24 does not enter the water passage hole 25 but enters the motor shaft side. As a result, it is possible to prevent the retention of cooling water and foreign matter and to prevent the growth of foreign matter (increasing the size of foreign matter) in a hygienic manner.

Example 16 In Example 8 above, FIG.
As shown in FIG. 0, by providing the unevenness 43 on the disk-shaped outer peripheral portion of the partition member 40, the effect of preventing clogging can be enhanced.

Example 17 In the above-mentioned Examples 8 to 16, the water passage hole 25 and the radial fitting gap 41 were on substantially the same circumferential line, but the radial fitting gap 41 was shifted in the outer circumferential direction as shown in FIG. If it is located, the filter effect is increased and the configuration of the pump chamber 24 can be changed.

Example 18. An embodiment of the invention according to claim 14 will be described with reference to FIG. FIG. 12 is a cross-sectional view in the axial direction, and the same or corresponding parts as those of the conventional one are designated by the same reference numerals and the description thereof will be omitted. The difference from the conventional one is that a resin pipe is attached to the outer circumference of the stator core 3 or an insulating member 44 such as resin coating is applied to the frame 8
Has a double insulating structure, and the sleeve bearings 17 and 18 and the thrust bearing 19 mounted on the brackets 9 and 10
The material is an insulating material such as resin or ceramic, and the brackets 9 and 10 are corrosion resistant aluminum alloys.

In the canned motor thus constructed, even if the brackets 9 and 10 and the can 5 come into contact with each other in the cooling water, the following closed circuit through which the corrosion current flows is provided on the outer circumference of the stator core 3. Since it can be blocked by the insulating member 44, it is possible to prevent contact corrosion (electrolytic corrosion) of the brackets 9 and 10 using the corrosion-resistant aluminum alloy. (Closed circuit 1 in which corrosion current flows) Bracket 9 or 10
→ Frame 8 → (Isolated by insulating member 44) → Stator core 3
→ can 5 → cooling water → bracket 9 or 10

Further, even if the brackets 9 and 10 and the rotor 11 come into contact with each other in the cooling water, the following closed circuit 2 in which the corrosion current flows
Since it can be blocked by the insulating bearing material, contact corrosion (electrolytic corrosion) of the brackets 9 and 10 can be prevented. (Closed circuit 2 in which corrosion current flows) Bracket 9 or 10
→ Radial bearings 17 and 18 (blocking by using insulating bearings) → Thrust bearing 19 (blocking by using insulating bearings) → Thrust disk 20 → Shaft 14 → Encapsulated liquid → Bracket 9 or 10

Example 19 In the eighteenth embodiment, the stator core 3 is provided with the insulating member 44 on the outer periphery. However, the material of the frame 8 is aluminum, and the inner diameter of the frame is subjected to an alumite treatment, which is an insulating coating. 10
By setting the thickness to be equal to or more than μm, the corrosion current between the can 5 and the brackets 9 and 10 can be cut off, and the same effect as that of the eighteenth embodiment can be obtained.

Example 20. In the eighteenth embodiment, the insulating member (layer) 44 is provided between the frame 8 and the stator core 3, but as shown in FIG. 13, an insulating gasket is provided on the mating surfaces of the frame 8 and the brackets 9 and 10. 45 and the insulating washer 4 under the tightening bolt 46.
By interposing 7 between them, the corrosion current between the can 5 and the brackets 9 and 10 can be interrupted, and the same effect as that of the above-described eighteenth embodiment can be obtained.

Example 21. In the 20th embodiment, the insulating gasket 45 is interposed between the mating surfaces of the frame 8 and the brackets 9 and 10. However, the surfaces of the brackets 9 and 10 (including the frame mating surface) are anodized as an insulating film. By setting the film thickness to 10 μm or more, the same effect as that of the insulating gasket 45 of the twentieth embodiment can be obtained.

Example 22. In the eighteenth embodiment described above, the insulating bearing material blocks the corrosion current between the brackets 9 and 10 and the rotor 11, but as shown in FIG. 14, the sleeve bearings 17 and 18 and the thrust bearing 19 are made of different materials. Conductive material such as copper alloy, sleeve bearing 17,1
8 is provided with an insulating member 48 on the outer periphery of the thrust bearing 19
Even if an insulating member 49 is interposed between the bracket 9 and the bracket 9, the same effect can be obtained.

Example 23. In the eighteenth embodiment, the insulating bearing material blocks the corrosion current between the brackets 9 and 10 and the rotor 11, but the sleeve bearing 17,
The same effect can be obtained by using 18 and the thrust bearing 19 as a conductive material such as a copper alloy, and using the shaft 14 and the thrust disk 19 that form the rotor 11 as an insulating ceramic material.

Example 24. In Example 23, the rotor 1
Although the shaft 14 constituting the shaft 1 is made of an insulating ceramic or the like, as shown in FIG. 15, an insulating sleeve made of ceramic or the like is provided on the parts 17a and 18a of the shaft 14 that slide with the sleeve bearings 17 and 18. The same effect can be obtained even if the device is attached or ceramic coated.

[0043]

As described above, according to the present invention, a constant optimum circulation flow rate can be maintained at all times without being affected by the working pressure of the pump, so that an abnormal temperature rise even in the low working pressure range of the pump. In addition, there is no danger that the circulating water will flow too much even in the high water pressure range where the pump is used. Therefore, it is possible to obtain a highly efficient product with high efficiency, low noise, no risk of abnormal temperature rise and long life. is there.

Further, according to the present invention, the partition member mounted on the motor shaft is fitted in the recess, and the motor cooling water is introduced through the radial fitting gap between the partition member and the recess, thereby eliminating the need for the filter. As a result, there is no possibility of clogging.

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 the corrosion-resistant aluminum alloy, so die casting can be performed, the productivity is improved, the finished product is good and the specific gravity is high. Since it is small, it is possible to reduce the weight of the product, and it is possible to obtain an inexpensive and high-quality product.

[Brief description of drawings]

FIG. 1 is an axial sectional view showing a first embodiment of the present invention.

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

FIG. 3 is an axial sectional view showing a third embodiment of the present invention.

4 is a cross-sectional view taken along the line IV-IV in FIG.

FIG. 5 is an axial sectional view showing a fourth embodiment of the present invention.

FIG. 6 is an axial sectional view showing a fifth embodiment of the present invention.

FIG. 7 is an axial sectional view showing Embodiment 6 of the present invention.

FIG. 8 is an axial sectional view showing Embodiment 7 of the present invention.

FIG. 9 is an axial sectional view showing Embodiment 8 of the present invention.

FIG. 10 is a cross-sectional view of essential parts showing Embodiment 16 of the present invention.

FIG. 11 is an axial sectional view showing Embodiment 17 of the present invention.

FIG. 12 is an axial sectional view showing Embodiment 18 of the present invention.

FIG. 13 is an axial sectional view showing Embodiment 20 of the present invention.

FIG. 14 is an axial sectional view showing Embodiment 22 of the present invention.

FIG. 15 is an axial sectional view showing Embodiment 24 of the present invention.

FIG. 16 is an axial sectional view showing a conventional electric pump.

17 is a diagram showing a characteristic example of the flow rate adjusting device of FIG.

[Explanation 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 chamber 25 Water passage hole 26 Front rotor chamber 27 Water passage 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 Blocking part 43 Indentation 44 Insulation Member 45 Insulating gasket 48 Insulating member 49 Insulating member

Claims (22)

[Claims] 1. A motor in which a part of the pump handling liquid is introduced into the motor as motor cooling water, and the cooling water that has passed through a gap in the motor is returned to the pump chamber through a hole formed in the motor shaft in the axial direction. In an electric pump having a circulating cooling structure, a radial hole that communicates the axial hole and the pump chamber is provided in a motor shaft near a cooling water introduction part from the pump chamber into the motor, and the axial direction The electric pump is characterized in that the end of the hole on the pump side on the pump side is covered with a blind. 2. The electric pump according to claim 1, wherein a ring is provided at a position of a radial hole on the outer periphery of the motor shaft, and a hole is provided in the ring so as to communicate with the radial hole. 3. An auxiliary impeller for generating a circulating flow is provided in the front rotor chamber of the motor.
Electric pump. 4. The electric pump according to claim 1, wherein the impeller of the pump chamber is provided with a water passage hole that connects the suction side and the discharge side. 5. A motor in which a part of the pump handling liquid is introduced into the motor as motor cooling water and the cooling water that has passed through the motor gap is returned to the pump chamber through a hole formed in the motor shaft in the axial direction. In an electric pump having a circulating cooling structure, a recess is provided in the motor-side inner wall portion of the pump chamber, a partition member mounted on the motor shaft is fitted in the recess, and the radial fitting gap is defined as a slit. An electric pump characterized in that the motor cooling water is introduced into the motor through the fitting gap. 6. The radial fitting gap is 0.05 to 0.7 m.
The electric pump according to claim 5, wherein the electric pump is m. 7. The electric pump according to claim 5, wherein the depth of the radial fitting gap is 2 mm or less. 8. The electric pump according to claim 5, wherein the recess has a through hole and the partition member has a disk shape. 9. The electric pump according to claim 5, wherein the partition member and the impeller are integrated. 10. The electric pump according to claim 5, wherein the pump chamber forming member and the partition member are made of the same material. 11. The electric pump according to claim 5, wherein the partition member is made of resin. 12. A blocking portion is provided near an inlet of a water passage hole for introducing the pump handling liquid from the pump chamber into the motor, the blocking portion preventing the pump handling liquid from entering the motor shaft side. The electric pump according to claim 5. 13. The electric pump according to claim 8, wherein the disk-shaped outer peripheral portion of the partition member is provided with irregularities. 14. A stator core having a coil wound around the inner diameter of a frame is mounted, and a can made of ultra-thin non-magnetic stainless steel is provided at the inner diameter of the stator core. The can separates the stator chamber and the rotor chamber. In an electric pump that is provided with brackets, which are isolated and have bearings that rotatably support the rotor, at both ends of the frame, and fill or forcibly circulate cooling water in the rotor chamber, the material of the bracket is a corrosion-resistant aluminum alloy. 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. 15. The electric pump according to claim 14, wherein an insulating resin pipe is attached to the outer periphery of the stator core or a resin coating is applied to the frame to have a double insulating structure. 16. The material of the frame is aluminum, and an alumite film having a film thickness of 10 μm or more is formed on the inner diameter of the frame,
The electric pump according to claim 14, wherein the frame has a double insulation structure. 17. A bracket made of a corrosion-resistant aluminum alloy is formed with an alumite film having a film thickness of 10 μm or more, and an insulating washer is interposed under a neck of a bolt for fastening the bracket to a frame. Item 14. The electric pump according to item 14. 18. The insulating gasket is interposed between the mating surfaces of the frame and the bracket.
Electric pump. 19. The electric pump according to claim 14, wherein the material of the bearing mounted on the bracket is an insulating material such as resin or ceramic. 20. The electric pump according to claim 14, wherein the 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. 21. The bearing material to be mounted on the bracket is made of a conductive material such as copper alloy, and the shaft and thrust disc of the rotor sliding on the bearing are made of insulating ceramic or the like. 14 electric pumps. 22. A bearing mounted on the bracket is made of a conductive material such as a copper alloy, and an insulating sleeve is attached to the shaft of a rotor sliding on the bearing or a ceramic coating is applied, and a thrust disk is made of an insulating ceramic. The electric pump according to claim 14, characterized in that