Electric oil pump and start method of the same

Abstract

To provide an electric oil pump which solves adhesion of a pump rotor, and to provide a start method of the electric oil pump.SOLUTION: An electric oil pump (1) includes: an oil pump part (5) having a pump rotor (2) and a pump housing (3) which houses the pump rotor (2); and a motor part (9) having a motor stator (6), a motor rotor (7), and a motor housing (8) which houses the motor stator (6) and the motor rotor (7). A rotary shaft protruding from the motor rotor (7) is connected to the pump rotor (2) and the motor rotor (7) is offset from the motor stator (6) in an axial direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric oil pump mounted on a vehicle or the like and a method for starting the electric oil pump. [Background technology]

[0002] An electric oil pump supplies hydraulic pressure to various hydraulically operated devices, such as an automatic gear of a vehicle, etc. The electric oil pump is driven by a motor.

[0003] In electric oil pumps used over a wide temperature range, such as those installed in vehicles, the viscosity of the oil increases in low-temperature environments, such as when starting the pump in cold regions, causing the pump rotor to stick, making it difficult to start the pump.

[0004] Therefore, there is a method for resolving a stuck pump that cannot be started by alternately driving the electric motor forward and backward (for example, Patent Document 1).

[0005] There is also a method in which the electric motor generates a torque sufficient to resolve the locking by driving it with a current exceeding the limit during normal operation during low-temperature startup (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-249059 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-238882 Summary of the Invention [Problem to be solved by the invention]

[0007] Simply driving the electric motor alternately forward and reverse as in Patent Document 1 can only apply a shearing force to the stuck surface due to the rotational force of the motor in the same direction as when it was started, and the stuck state may not be resolved.

[0008] To drive the motor with a current exceeding the limit during normal operation, as in Patent Document 2, requires a circuit and motor that can handle that, which increases the size and cost of the device. Also, the only shear force that can be applied to the stuck surface is the rotational force of the motor in the same direction as when it was started, which may make it impossible to resolve the stuck state.

[0009] The present invention has been made to solve the above-mentioned problems, and aims to provide an electric oil pump and a method for starting an electric oil pump that eliminates stuck pump rotors without increasing the size or cost of the device. [Means for solving the problem]

[0010] To achieve the above object, the electric oil pump according to the present invention includes an oil pump section having a pump rotor and a pump housing that houses the pump rotor, and a motor section having a motor stator, a motor rotor, and a motor housing that houses the motor stator and the motor rotor. A rotating shaft protruding from the motor rotor is connected to the pump rotor, and the motor rotor is axially offset from the motor stator. Here, "axially offset" means that a center position C7 of the motor rotor is axially shifted from a center position C6 of the motor stator.

[0011] With this configuration, the rotational axis of the motor rotor is offset in the axial direction from the motor stator, so that an axial force acts on the rotational axis at start-up, causing the pump rotor to separate axially from the fixed surface between the pump housing and the pump rotor. This effectively resolves the pump rotor's sticking and allows the electric oil pump to start up without increasing the size or cost of the device.

[0012] The motor housing and the pump housing may be connected via a highly heat-conductive member having high thermal conductivity.

[0013] With this configuration, the heat generated in the motor stator is transferred to the pump housing via a highly thermally conductive member, raising the temperature of the fixing surface of the pump rotor, thereby reducing the viscosity of the oil and weakening the fixing force of the pump rotor.

[0014] The motor section may include a phase detector that detects the phase of the motor rotor.

[0015] According to this configuration, by detecting the phase of the motor rotor using a phase detector such as a rotation angle sensor, it is possible to implement a current application method that generates a strong axial peeling force on the fixed surface of the motor rotor.

[0016] The high thermal conductivity member may be formed integrally with either the motor housing or the pump housing.

[0017] This configuration reduces the number of parts and assembly steps, thereby reducing costs.

[0018] The method for starting an electric oil pump according to the present invention is for an electric oil pump including an oil pump section having a pump rotor and a pump housing that houses the pump rotor, and a motor section having a motor stator, a motor rotor, and a motor housing that houses the motor stator and the motor rotor, in which the motor rotor is offset in the axial direction relative to the motor stator, and current is applied in a phase in which a repulsive force acts between the motor stator and the motor rotor when the motor is started.

[0019] This method generates an axial force that separates the stuck interface, which is in a different direction from the rotational torque of the motor, without increasing the size or cost of the device, thereby effectively eliminating the stuck motor rotor and starting the electric oil pump at low cost.

[0020] When the motor is stopped, current may be supplied to the motor stator and the motor rotor in a phase where an attractive force acts between them, thereby correcting the phase of the motor rotor to a predetermined position while the motor is stopped.

[0021] According to this method, even if a phase detector for detecting the phase of the motor rotor is not provided, the phase of the motor rotor is known when the motor is started, and the above-described start-up method for generating an axial force on the motor rotor can be implemented.

[0022] The pump rotor or the pump housing may be heated before starting the motor.

[0023] This method reduces the viscosity of the oil before the motor starts, thereby weakening the adhesion of the pump rotor. [Effects of the Invention]

[0024] According to the electric oil pump and the method for energizing the electric oil pump of the present invention, the rotating shaft of the motor rotor is offset in the axial direction from the motor stator, so that an axial force acts on the rotating shaft at the time of start-up, causing the pump rotor to separate in the axial direction from the fixed surface between the pump housing and the pump rotor. This effectively resolves the sticking of the pump rotor and allows the electric oil pump to start up without increasing the size or cost of the device. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view of an electric oil pump according to a first embodiment of the present invention. [Figure 2A] 1 is a schematic diagram of a motor according to the present invention, showing energized phases at startup. FIG. [Figure 2B] 1 is a schematic diagram of a motor according to the present invention showing energized phases when stopped; [Figure 2C] FIG. 2 is a schematic diagram of a motor according to the present invention, showing phases when not energized. [Figure 3] FIG. 4 is a cross-sectional view of an electric oil pump according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view of an electric oil pump according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] First Embodiment An electric oil pump 1 according to a first embodiment of the present invention will be described. As shown in FIG. 1, the electric oil pump 1 includes an oil pump section 5 having a pump rotor 2 and a pump housing 3 that houses the pump rotor 2, and further includes a motor section 9 having a motor stator 6, a motor rotor 7, and a motor housing 8 that houses the motor stator 6 and the motor rotor 7, with the pump rotor 2 and the motor rotor 7 being coaxially connected by a rotating shaft 10.

[0027] In the following description, the pump rotor 2 side (right side in FIG. 1) in the axial direction of the electric oil pump 1 will be referred to as the "front side," and the motor rotor 7 side (left side in FIG. 1) will be referred to as the "rear side." Furthermore, in the following description, unless otherwise specified, the "axial direction" refers to the direction along the central axis of the rotating shaft 10 that constitutes the electric oil pump, and the "radial direction" refers to the radial direction of a circle centered on the central axis of the rotating shaft 10.

[0028] (Oil pump part 5) As shown in FIG. 1, the oil pump unit 5 is located on the front side of the motor unit 9 and is driven by the motor unit 9 via a rotating shaft 10 arranged along a central axis A extending in the axial direction, to discharge oil from a discharge port (not shown).

[0029] The pump rotor 2 is housed in a pump housing 3 and fixed to the front end of a rotary shaft 10. The pump rotor 2 rotates as the rotary shaft 10 rotates. In the illustrated example, the pump rotor 2 and pump housing 3 are cylindrical, but they may have any shape as long as they can function as an oil pump. In this embodiment, it is assumed that the pump rotor 2 and pump housing 3 are stuck together at the rear end face 31 of the pump rotor 2.

[0030] (Motor section 9) The motor section 9 is an inner rotor type motor in which the motor rotor 7 is fixed to the outer peripheral surface of the rotating shaft 10, and the motor stator 6 is arranged radially outside the motor rotor 7. The motor stator 6 is arranged so that its inner peripheral surface faces the outer peripheral surface of the motor rotor 7. The motor stator 6 and motor rotor 7 are housed radially inside the motor housing 8. The motor stator 6 is fixed to the motor housing 8 by press fitting, adhesive, or the like. In the illustrated example, the motor housing 8 is cylindrical, but it may have any shape as long as it can house the motor stator 6 and motor rotor 7 and perform the functions of the motor section 9 as a whole.

[0031] The front side (right side) of the rotating shaft 10 serving as the motor shaft projects from the front end of the motor stator 6 and is connected to the pump rotor 2.

[0032] Although not shown, the motor stator 6 is formed by a stator core made of laminated thin plates of magnetic material and coil windings wound around the stator core through grooves formed in the stator core. A magnetic field generated by passing current through the coil windings rotates the rotating shaft 10 and the motor rotor 7 fixed to the outer circumferential surface of the rotating shaft 10.

[0033] The motor stator 6 and the motor rotor 7 are offset in the axial direction. That is, the axial center positions C6 and C7 of the motor stator 6 and the motor rotor 7 are offset in the axial direction of the rotating shaft 10, with the center position C7 being located a distance D forward of the center position C6. In this embodiment, the motor stator 6 and the motor rotor 7 have the same axial length. Therefore, the rear end face 7a of the motor rotor 7 is offset forward from the rear end face 6a of the motor stator 6 by a distance D corresponding to the offset, and the rear end face 7a of the motor rotor 7 is located forwardly from the rear end face 6a of the motor stator 6 by the distance D. In this case, the dimensions of the motor housing 8 and / or the high-thermal-conductivity member 11 (described later) are set so that the front end face 7b of the motor rotor 7 does not contact the rear end face 3a of the pump housing 3. The motor stator 6 and the motor rotor 7 usually have the same length, but may have different lengths.

[0034] When the motor stator 6 and the motor rotor 7 are different lengths, distance D is determined by the amount of offset based on the center positions C6 and C7. Distance D is preferably larger than air gap H, which is the radial space formed between the motor stator 6 and the motor rotor 7. Air gap H can be expressed as H = (H6 - H7) / 2, where H6 is the inner diameter of the motor stator 6 and H7 is the outer diameter of the motor rotor 7. By making D > H, it is possible to generate a sufficient axial force to eliminate sticking.

[0035] The motor unit 9 includes a phase detector 20 that detects the phase of the motor rotor 7, but may not include one. The phase detector 20 is, for example, a rotation angle sensor such as a resolver or an encoder.

[0036] The pump housing 3 and the motor housing 8 are connected via a high thermal conductivity member 11. The front end face 6b of the motor stator 6 and the front end face 8b of the motor housing 8 are in contact with the rear end face 11a of the high thermal conductivity member 11, and the rear end face 3a of the pump housing 3 is in contact with the front end face 11b of the high thermal conductivity member 11. In the illustrated example, the high thermal conductivity member 11 is cylindrical, but this is not limiting. Furthermore, it is preferable that the thermal conductivity of the high thermal conductivity member 11 be equal to or greater than that of the pump housing 3 and the motor housing 8.

[0037] The motor housing 8, the pump housing 3 and the highly heat-conductive member 11 are made of metal such as copper, aluminum, aluminum alloy, or iron-based metal such as stainless steel, or resin.

[0038] Next, a method for starting the electric oil pump 1 will be described with reference to FIGS. 2A to 2C. First, a start-up method when the motor unit 9 has a phase detector 20 will be described. When starting the electric oil pump 1, as shown in FIG. 2A , the motor stator 6 and the motor rotor 7 are excited in a phase where the motor stator 6 and the motor rotor 7 have the same polarity in accordance with the phase of the motor rotor 7 measured by the phase detector 20, and current is applied to the motor stator 6 so that a repulsive force acts between the motor stator 6 and the motor rotor 7. For example, if the north pole side of the motor rotor 7 is stopped in a position facing the U phase of the motor stator 6, a repulsive force acts between the motor stator 6 and the motor rotor 7 by applying current so that the U phase of the motor stator 6 becomes the north pole of the motor rotor 7, the V phase becomes the south pole of the motor rotor 7, and the W phase becomes the south pole of the motor rotor 7. As shown in FIG. 1 , the motor rotor 7 is disposed axially displaced from the motor stator 6 by a distance D corresponding to the offset, and therefore the repulsive force acting between the motor stator 6 and the motor rotor 7 includes an axial repulsive force F1 acting on the motor rotor 7 toward the front side.

[0039] Next, a start-up method will be described when the motor unit 9 does not have a phase detector 20. In the case of a sensorless type motor that estimates the phase of the motor rotor 7 by detecting the current and voltage while rotating, the phase of the motor rotor 7 cannot be estimated when the electric oil pump 1 is started while the rotation of the motor rotor 7 is stopped. For this reason, there are cases where it is not possible to implement the start-up method in which the motor stator 6 and motor rotor 7 are excited in a phase where they have the same polarity, and a repulsive force acts between the motor stator 6 and motor rotor 7.

[0040] Therefore, when the electric oil pump 1 is stopped from an operating state, current is applied at a specific phase as shown in Fig. 2B, so that the phase of the motor rotor 7 is known even when the motor rotor 7 is stopped. For example, if current is applied so that the U phase of the motor stator 6 becomes the S pole of the motor rotor 7, the V phase becomes the N pole of the motor rotor 7, and the W phase becomes the N pole of the motor rotor 7, the motor rotor 7 will stop at a position where the N pole side of the motor rotor 7 faces the U phase of the motor stator 6. After stopping, in a de-energized state, the motor rotor 7 is fixed in the above-mentioned stopped position by the attractive force of the magnetic force acting between the iron core of the motor stator 6 and the motor rotor 7, as shown in Fig. 2C.

[0041] In this way, by correcting the phase of the stopped motor rotor 7 to a predetermined position, the phase of the motor rotor 7 is known, and therefore, when starting the electric oil pump 1, the starting method shown in FIG. 2A described above can be carried out to generate a repulsive force between the motor stator 6 and the motor rotor 7. Here, the "predetermined position" refers to a position where the starting method of the present invention can be carried out, for example, a position where the N pole or S pole of the motor rotor 7 faces the U phase, V phase, or W phase of the motor stator 6. Note that, although the motor unit 9 has been described as a three-phase AC motor, it is not limited to a three-phase AC motor, and the number of phases is not limited as long as the effects of the present invention can be achieved.

[0042] According to the electric oil pump 1 of the present invention, in situations where starting is difficult due to sticking of the pump rotor 2, which occurs particularly at low temperatures, the sticking can be resolved effectively and at low cost and the electric oil pump 1 can be started by generating an axial force that separates the stuck interface, which is in a direction different from the rotational torque of the motor, without increasing the size of the device or increasing costs due to an increase in current.

[0043] In the electric oil pump 1, the motor housing 8 and the pump housing 3 shown in FIG. 1 are connected via a highly heat-conductive member 11 having high thermal conductivity. Therefore, heat generated in the motor stator 6 is transferred to the pump housing 3 by the highly heat-conductive member 11, and the temperature of the fixing surface of the pump rotor is increased, thereby reducing the viscosity of the oil and weakening the fixing force of the pump rotor 2.

[0044] To further reduce the heat-induced adhesion of the pump rotor 2, the pump rotor 2 or the pump housing 3 may be heated by a heater or the like before starting the motor. By preheating the pump rotor 2 and / or the pump housing 3, adhesion of the pump rotor 2 can be quickly resolved by two types of heat: heat from the heater or the like when the motor starts, and heat generated by the motor stator 6 after the motor starts.

[0045] Because the motor section 9 has a phase detector 20 that detects the phase of the motor rotor 7, by knowing the phase of the motor rotor 7, it is possible to energize the motor stator 6 so that a repulsive force acts between the motor stator 6 and the motor rotor 7, i.e., so that an axial force is generated against the fixing surface 31. Even if the motor section 9 does not have a phase detector 20 that detects the phase of the motor rotor 7, as already explained, it is possible to implement a start-up method in which a repulsive force acts between the motor stator 6 and the motor rotor 7 by energizing the motor at a specific phase when the electric oil pump 1 is stopped from an operating state and keeping the phase of the motor rotor 7 known even when the motor rotor 7 is stopped.

[0046] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as the previously described embodiment unless otherwise specified. The same functions and effects are achieved from the same configuration. It is possible to combine not only the parts specifically described in each embodiment, but also parts of the embodiments together, provided that there is no particular problem with the combination.

[0047] <Second embodiment> Next, an electric oil pump 1 according to a second embodiment of the present invention will be described. As shown in Figure 3, in this embodiment, high thermal conductivity member 11 is integrally formed with motor housing 8. This configuration reduces the number of parts and assembly steps, thereby keeping costs down. Here, "integrally formed" means that high thermal conductivity member 11 and motor housing 8 are not formed by combining multiple elements, but are formed as part or the whole of a single object from a single material by, for example, forging, casting, machining, etc.

[0048] Furthermore, the high thermal conductivity member 11 is not limited to being integrated with the motor housing 8, but may be formed integrally with the pump housing 3. By forming the high thermal conductivity member 11 integrally with either the motor housing 8 or the pump housing 3 in this way, the number of parts and the number of assembly steps can be reduced, and costs can be held down. Furthermore, the high thermal conductivity member 11 may be formed integrally with both the motor housing 8 and the pump housing 3. In this case, as in the above, the number of parts and the number of assembly steps can be reduced, and costs can be held down.

[0049] <Third embodiment> Next, an electric oil pump 1 according to a third embodiment of the present invention will be described. 4, in the motor section 9 of this embodiment, the front end face 7b of the motor rotor 7 is offset toward the rear (left side) by a distance D corresponding to the offset from the front end face 6b of the motor stator 6. That is, in this embodiment, the motor rotor 7 is disposed offset by the distance D in the direction opposite to the offset direction in the first embodiment.

[0050] When the motor rotor 7 is positioned offset by a distance D in the direction opposite to the offset direction in the first embodiment, and the motor stator 6 and the motor rotor 7 are excited in a phase in which they have the same polarity, and current is passed through the motor stator 6 so that a repulsive force acts between the motor stator 6 and the motor rotor 7, the motor rotor 7 is offset so that it protrudes toward the rear side from the motor stator 6, and therefore the repulsive force includes an axial repulsive force F2 acting on the motor rotor 7 toward the rear side.

[0051] According to this configuration, if the pump rotor 2 and the pump housing 3 are stuck at the front end face of the pump rotor 2, the repulsive force F2 is an axial force that separates the stuck surface 31, so the combined force of the repulsive force F2 and the rotational torque of the motor can eliminate the sticking of the pump rotor 2.

[0052] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0053] 1... electric oil pump, 2... pump rotor, 3... pump housing, 5... oil pump section, 6... motor stator, 7... motor rotor, 8... motor housing, 9... motor section, 10... rotating shaft, 11... high heat conductive member, 20... phase detector

Claims

1. an oil pump unit having a pump rotor and a pump housing that houses the pump rotor; An electric oil pump including a motor unit having a motor stator, a motor rotor, and a motor housing that accommodates the motor stator and the motor rotor, a rotating shaft protruding from the motor rotor is connected to the pump rotor; An electric oil pump in which the motor rotor is offset in the axial direction relative to the motor stator.

2. 2. The electric oil pump according to claim 1, wherein the motor housing and the pump housing are connected via a highly heat-conductive member having high thermal conductivity.

3. 3. The electric oil pump according to claim 1, wherein the motor section includes a phase detector that detects the phase of the motor rotor.

4. 3. The electric oil pump according to claim 2, wherein the high heat conductivity member is formed integrally with either the motor housing or the pump housing.

5. an oil pump unit having a pump rotor and a pump housing that houses the pump rotor; A method for starting an electric oil pump including a motor unit having a motor stator, a motor rotor, and a motor housing that accommodates the motor stator and the motor rotor, comprising: The motor rotor is offset in the axial direction relative to the motor stator, A method for starting an electric oil pump, wherein when starting the electric oil pump, current is applied to the motor stator in a phase where a repulsive force acts between the motor stator and the motor rotor at the time of starting the motor.

6. 6. A method for starting an electric oil pump according to claim 5, wherein when the motor is stopped, current is applied in a phase in which an attractive force acts between the motor stator and the motor rotor, and the phase of the motor rotor while stopped is corrected to a predetermined position.

7. 7. The method for starting an electric oil pump according to claim 5, wherein the pump rotor or the pump housing is heated before starting the motor.

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