Electric pump

Abstract

To constitute an electric pump that changes the speed of driving force of an electric motor and transmits it to a pump part without causing an increase in size.SOLUTION: An electric pump comprises: an electric motor M comprising a field coil 15 arranged in an annular region around a driving axis X, and a motor rotor 16 supported rotatably around the driving axis X; a speed change part G for changing the speed of rotation of the motor rotor 16 and transmitting it to a driving shaft S; a pump part P to be driven by driving force of the driving shaft S; and a housing H for housing each of the electric motor M, the speed change part G, the driving shaft S, and the pump part P. The motor rotor 16 comprises a permanent magnet 16b on an outer peripheral side of a cylindrical yoke 16a around the driving axis X. The speed change part G is housed in an internal space of the yoke 16a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric pump. [Background technology]

[0002] 2. Description of the Related Art Japanese Patent Application Laid-Open No. 2003-233663 and Japanese Patent Application Laid-Open No. 2003-233664 disclose electric pumps in which the driving force of an electric motor is transmitted to a pump section via a gear-type reduction mechanism.

[0003] The electric pump of Patent Document 1 (referred to as a pump unit in the document) accommodates an electric motor, a pump drive shaft to which the driving force of the electric motor is transmitted, and a pump to which force is transmitted from the pump drive shaft, in a unit housing.

[0004] In the electric pump of Patent Document 1, the pump is configured as an internal gear pump having an inner gear (pump rotor) and an outer gear, and a transmission consisting of a planetary gear reducer is built into the inner gear so that the driving force from the pump drive shaft is reduced and transmitted to the inner rotor.

[0005] In the electric pump of Patent Document 2 (referred to as a dual-system drive pump in the document), a planetary gear mechanism, which transmits the driving force of an engine etc. and the driving force of an electric motor, is housed in a housing, and the housing also houses a drive system that transmits the driving force from this planetary gear mechanism to a pump mechanism.

[0006] In the electric pump of Patent Document 2, when the engine is running, current is passed through the electric motor to keep the carrier of the planetary gear mechanism stationary, and the driving force of the engine is used to rotate the ring gear to drive the pump. Also, when the engine is stopped, the ring gear is stationary, so by driving the electric motor, the driving force of the electric motor is transmitted from the pinion of the planetary gear mechanism to the sun gear to drive the pump. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-189012 A [Patent Document 2] JP 2019-100320 A Summary of the Invention [Problem to be solved by the invention]

[0008] For example, in the case of an electric pump for supplying hydraulic oil in a vehicle, when the viscosity of the hydraulic oil is high, such as in a low-temperature environment, it is necessary to drive the electric pump with high torque. For this reason, a reduction gear is required to reduce the driving force of the electric motor and transmit it to the pump.

[0009] To address these issues, an electric pump that houses a planetary gear reducer in the pump rotor, such as the electric pump described in Patent Document 1, makes it possible to transmit the driving force of the electric motor to the pump rotor after reducing the speed. However, because the planetary gear reducer is housed in the inner gear, not only does the pump rotor become larger, increasing the outer diameter of the rotor, but also necessitating a clearance between the pump rotor and the planetary gear reducer, which makes it easy for rotor meshing to fluctuate due to load fluctuations, etc., raising concerns that this could lead to increased pulsation and operating noise.

[0010] In addition, in a configuration in which two driving forces are transmitted to a planetary gear mechanism, such as the electric pump described in Patent Document 2, it is possible to transmit a reduced driving force to the pump. However, it is conceivable that when the electric motor is driven while the engine is stopped, the pump will rotate at a high speed, reducing the pump's efficiency and increasing noise.

[0011] The electric pump described in Patent Document 2 uses a planetary gear mechanism, which makes it possible to drive the pump using the driving force of the engine and the electric motor simultaneously. However, when driving the pump using the driving force of the engine, it is necessary to supply current to the electric motor just to stop the rotation of the carrier, resulting in unnecessary consumption of current.

[0012] For these reasons, there is a demand for an electric pump that can transmit the driving force of an electric motor to a pump section while changing the speed, without increasing the size of the pump. [Means for solving the problem]

[0013] A characteristic configuration of an electric pump according to the present invention includes an electric motor having a field coil arranged in an annular region centered on a drive shaft core, and a motor rotor supported rotatably about the drive shaft core and rotated by the action of a magnetic field of the field coil, a speed change unit that changes the speed of the rotation of the motor rotor and transmits it to a drive shaft, a pump unit that is driven by the driving force of the drive shaft, and a housing that accommodates the electric motor, the speed change unit, the drive shaft, and the pump unit, and the motor rotor is provided with a permanent magnet on the outer periphery of a cylindrical yoke centered on the drive shaft core, and the speed change unit is accommodated in an internal space of the yoke. The housing has a protruding portion protruding toward the transmission unit inside the housing so as to support the drive shaft in a penetrating state, and a bearing that rotatably supports the motor rotor is supported in contact with the protruding portion. The point is that

[0014] According to this characteristic configuration, when driving the pump section, a current is supplied to the field coil to rotate the motor rotor, and the rotational force of the motor rotor is transmitted to the pump section via the drive shaft after being changed in speed by the speed change section, thereby driving the pump section. In addition, since the speed change section is disposed inside the yoke constituting the motor rotor, it is possible to dispose the speed change section by effectively utilizing the internal space of the electric motor, for example, without forming a space for disposing the speed change section inside the housing. In addition, with this characteristic configuration, the pump section does not need to be made larger, as in Patent Document 1. Thus, an electric pump is configured in which the driving force of the electric motor is changed in speed and transmitted to the pump section without increasing the size.

[0015]

[0016] Also, According to this, by using, for example, a ball bearing or roller bearing as the bearing and supporting the inner race of this bearing by, for example, fitting it externally onto the protruding portion of the housing, the motor rotor can be supported in a state in which it can rotate stably.

[0017] In addition to the above configuration, the transmission unit may be configured as a planetary gear type that includes a sun gear, a ring gear arranged in an area surrounding the sun gear, and a plurality of planetary gears that mesh with the sun gear and the ring gear, thereby changing the speed of the driving force transmitted from the motor rotor and transmitting it to the drive shaft.

[0018] According to this, the transmission section is configured as a planetary gear type, which makes it possible to achieve a large gear ratio while suppressing an increase in size.

[0019] In addition to the above configuration, the transmission unit is configured as a planetary gear type that includes a sun gear, a ring gear arranged in an area surrounding the sun gear, a plurality of planetary gears meshing with the sun gear and the ring gear, and a carrier supporting the plurality of planetary gears, and thereby changes the speed of the driving force transmitted from the motor rotor and transmits it to the drive shaft; the pump unit includes a first pump mechanism of an internal gear type having a first inner rotor and a first outer rotor that rotates in conjunction with the first inner rotor, and a second inner rotor that rotates in conjunction with the first inner rotor. The pump may further include a second pump mechanism having a narrow rotor and an internal gear type second outer rotor that rotates in conjunction with the second inner rotor, the drive shaft having a first drive shaft one end connected to the first inner rotor and the other end connected to the carrier, and a cylindrical second drive shaft one end connected to the second inner rotor and the other end connected to the ring gear, and fitted around the first drive shaft so as to be rotatable relative to the first drive shaft, and a pump switching unit that stops operation of one of the first pump mechanism and the second pump mechanism to enable operation of the other.

[0020] According to this, when the operation of the first pump mechanism is stopped by the pump switching unit in a state where the electric motor is driven, for example, the rotation of the carrier connected to the first inner rotor and the first drive shaft of the first pump mechanism is stopped, so that the rotational force of the ring gear is transmitted to the second inner rotor via the second drive shaft, and the second pump mechanism can discharge the fluid. On the other hand, when the operation of the second pump mechanism is stopped, the rotation of the ring gear connected to the second inner rotor and the second drive shaft of the second pump mechanism is stopped, so that the rotational force of the carrier is transmitted to the first inner rotor via the first drive shaft, and the first pump mechanism can discharge the fluid. In addition, with this configuration, when switching between the first pump mechanism and the second pump mechanism, there is no wasteful consumption of current as in Patent Document 2.

[0021] In other words, in a planetary gear type transmission, the gear ratio differs between a drive mode in which the rotational force of the ring gear is extracted with the carrier constrained, and a drive mode in which the rotational force of the carrier is extracted with the ring gear constrained, so that by selecting one of the drive modes, it is possible to drive the first pump mechanism and the second pump mechanism at different gear ratios.

[0022] In addition to the above configuration, the pump switching unit may include a flow path selection valve that selects one of a first discharge portion of the first pump mechanism and a second discharge portion of the second pump mechanism to limit the discharge of hydraulic oil.

[0023] According to this, by blocking either the discharge port of the first pump mechanism or the discharge port of the second pump mechanism with the flow path selection valve, it is possible to drive only one of the first pump mechanism or the second pump mechanism to discharge fluid.

[0024] In addition to the above configuration, the transmission unit may have an output gear provided in the internal space of the yoke so as to rotate integrally with the motor rotor around the drive shaft core, and an input gear provided in the internal space so as to mesh with the output gear, and the rotational force of the input gear may be transmitted from the drive shaft to the pump unit.

[0025] According to this, when the electric motor is driven, the rotational force of the output gear is transmitted to the input gear meshing with the output shaft, and the rotational force of the output gear is transmitted from the drive shaft to the pump section, thereby driving the pump section. In particular, with this configuration, the output gear and the input gear are disposed in the internal space of the motor rotor, so that the overall size of the electric pump is not increased. [Brief description of the drawings]

[0026] [Figure 1] FIG. 4 is a cross-sectional view of the electric pump in a state where a first pump portion is driven. [Diagram 2] FIG. 4 is a cross-sectional view of the electric pump in a state where the second pump portion is driven. [Diagram 3] FIG. 2 is a hydraulic circuit diagram of an electric pump. [Figure 4] FIG. 11 is a cross-sectional view of an electric pump according to another embodiment (a). [Diagram 5] FIG. 11 is a cross-sectional view of an electric pump according to another embodiment (b). [Figure 6] FIG. 11 is a cross-sectional view of an electric pump according to another embodiment (c). [Figure 7] FIG. 11 is a cross-sectional view of an electric pump according to another embodiment (d). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Basic configuration] As shown in Figures 1 and 2, electric pump A is configured by accommodating a brushless electric motor M, a planetary gear type transmission unit G, a drive shaft S to which the rotational force reduced (an example of a transmission) by this transmission unit G is transmitted, and an internal gear type pump unit P in a housing H, and also by providing a control unit C in the housing H that controls the electric motor M.

[0028] Although the electric pump A can be used in any position, the positional relationship of each part will be described with the up-down direction fixed as shown in Figs.

[0029] 1 and 2 show an electric pump A used as an oil pump for pumping hydraulic oil in a vehicle such as a passenger car. This electric pump A reduces the driving force of an electric motor M in a transmission unit G (one example of a transmission) and transmits it to a pump unit P via a drive shaft S, thereby drawing in hydraulic oil from a suction port 6P formed at the end of a housing H and pumping it out from a discharge port 7P.

[0030] In this electric pump A, a motor rotor 16 of an electric motor M is configured to be rotatable around a drive shaft core X. The electric pump A is configured to switch between two types of discharge amount of hydraulic oil from a pump section P, and a drive shaft S of the electric pump A has a cylindrical first drive shaft Sa arranged coaxially with the drive shaft core X, and a second drive shaft Sb fitted inside the first drive shaft Sa so as to be rotatable relative to the first drive shaft Sa. The pump section P also has a first pump mechanism Pa driven by the drive force of the first drive shaft Sa, and a second pump mechanism Pb driven by the drive force of the second drive shaft Sb.

[0031] As shown in Figures 1 to 3, the first pump mechanism Pa has a smaller capacity than the second pump mechanism Pb by setting the diameter of the first outer rotor 32 of the first pump mechanism Pa smaller than the diameter of the second outer rotor 34 of the second pump mechanism Pb.

[0032] In particular, the electric pump A is configured so that by stopping the operation of one of the first pump mechanism Pa and the second pump mechanism Pb, the other is operated, and the driving force from the transmission unit G is transmitted to the other pump mechanism, thereby driving the first drive shaft Sa and the second drive shaft Sb at different gear ratios. These configurations will be described in detail below.

[0033] 〔housing〕 As shown in Figures 1 and 2, the housing H is constructed by stacking a first housing 1 made of resin that houses the electric motor M, a second housing 2 made of metal that houses the first pump mechanism Pa, a third housing 3 made of metal that houses the second pump mechanism Pb, a fourth housing 4 made of metal that is arranged at the bottom, and a lid-shaped fifth housing 5 that is arranged on the upper side of the first housing 1 so as to cover the control unit C.

[0034] The first housing 1 accommodates the electric motor M, the speed change unit G, and also accommodates an electromagnetic switching valve V (an example of a pump switching unit T). A field coil 15 of the electric motor M and the electromagnetic switching valve V are inserted into this first housing 1 during molding using a metal mold. The field coil 15 has a structure in which a coil wire is wound around multiple teeth of a stator core made of laminated electromagnetic steel plates, and is disposed in an annular region centered on the drive shaft core X.

[0035] The second housing 2 accommodates the first pump mechanism Pa and has a protruding portion 2a that protrudes into the upper housing space in a direction along the drive shaft core X. A shaft support hole through which the drive shaft S passes is formed in the protruding portion 2a and is coaxial with the drive shaft core X. As a result, the first drive shaft Sa of the drive shaft S is rotatably supported by the shaft support hole.

[0036] The third housing 3 accommodates the second pump mechanism Pb. The fourth housing 4 has an intake passage 6 and a discharge passage 7 formed therein, and also has an intake port 6P connected to the intake passage 6 and a discharge port 7P connected to the discharge passage 7 formed on the bottom surface. The fourth housing 4 also has a flow path selection valve 8 (an example of a pump switching unit T) formed therein.

[0037] The fifth housing 5 is disposed in a position covering a recess that is formed in the upper part of the first housing 1 and opens upward. A control board 9 provided in the space covered by the fifth housing 5 constitutes a control unit C. The control unit C controls the electric motor M and the solenoid switching valve V.

[0038] In other words, the control unit C includes a power control unit that supplies power to the field coil 15 of the electric motor M, a rotation control unit that controls the rotational speed (number of rotations per unit time) of the motor rotor 16, and a valve control unit that controls the electromagnetic switching valve V.

[0039] [Electric motor / transmission section] The electric motor M includes a field coil 15 arranged in an annular region centered on the drive shaft core X, and a motor rotor 16 that rotates around the drive shaft core X by a magnetic field acting from the field coil 15. The motor rotor 16 includes a plurality of permanent magnets 16b on the outer periphery of a cylindrical yoke 16a made of a magnetic material such as iron, and the lower end of this yoke 16a is supported by a roller bearing type bearing 17 on the outer periphery of a protruding portion 2a inside the second housing 2 so as to be rotatable around the drive shaft core X.

[0040] The transmission section G includes a sun gear 21 that is coaxially disposed with the drive shaft center X and protrudes downward from the lower surface of a rotor plate 18 that is fixed to the upper end of the motor rotor 16, a ring gear 22 that has an internal tooth portion formed in an annular region centered on the drive shaft center X, a plurality of planetary gears 23 that mesh with the sun gear 21 and the ring gear 22, and a pair of upper and lower carriers 25 that support support shafts 24 for the plurality of planetary gears 23.

[0041] In particular, a sun gear 21, a ring gear 22, a plurality of planetary gears 23, and a pair of carriers 25 that constitute the transmission G are housed in the internal space of the motor rotor 16 (the space inside the yoke 16a).

[0042] [Pump section] As described above, the pump section P includes the first pump mechanism Pa and the second pump mechanism Pb. As shown in Fig. 3, the first pump mechanism Pa includes a first inner rotor 31 having a plurality of external teeth, and a first outer rotor 32 having internal teeth whose number is one more than the number of external teeth of the first inner rotor 31. The second pump mechanism Pb includes a second inner rotor 33 having a plurality of external teeth, and a second outer rotor 34 having internal teeth whose number is one more than the number of external teeth of the second inner rotor 33.

[0043] In the pump section P (a generic concept of the first pump mechanism Pa and the second pump mechanism Pb), negative pressure acts on the region where the space between the inner teeth and the outer teeth expands as the inner rotor (first inner rotor 31, second inner rotor 33) and the outer rotor (first outer rotor 32, second outer rotor 34) rotate, and positive pressure acts on the region where the space between the inner teeth and the outer teeth contracts as the rotor rotates. For this reason, the region where negative pressure acts is connected to the suction passage 6, and the region where positive pressure acts is connected to the discharge passage 7.

[0044] In particular, the flow path selection valve 8 is disposed in the discharge path 7 midway between the first discharge portion of the first pump mechanism Pa and the discharge port 7P, and an intermediate region in the discharge path 7 between the first discharge portion and the flow path selection valve 8 is referred to as a first discharge path 7a. Also, the flow path selection valve 8 is disposed in the discharge path 7 midway between the second discharge portion of the second pump mechanism Pb and the discharge port 7P, and an intermediate region in the discharge path 7 between the second discharge portion and the flow path selection valve 8 is referred to as a second discharge path 7b.

[0045] The first discharge portion is a portion in the first pump mechanism Pa from which hydraulic oil is discharged as the first pump mechanism Pa is operated, and the second discharge portion is a portion in the second pump mechanism Pb from which hydraulic oil is discharged as the second pump mechanism Pb is operated.

[0046] [Drive structure / pump switching operation] As shown in Figures 1 and 2, one end (upper end) of the first drive shaft Sa of the drive shaft S is connected to an end plate 26 that rotates integrally with the ring gear 22, and the other end (lower end) of the first drive shaft Sa is connected to the first inner rotor 31 of the first pump mechanism Pa.

[0047] In addition, one end (upper end) of the second drive shaft Sb of the drive shaft S is connected to the lower carrier 25 of the pair of carriers 25, and the other end (lower end) of this second drive shaft Sb is connected to the second inner rotor 33 of the second pump mechanism Pb.

[0048] The planetary gear type transmission G has the property that the ring gear 22 rotates when the rotation of the carrier 25 is stopped while the sun gear 21 is rotating, and the carrier 25 rotates when the rotation of the ring gear 22 is stopped while the sun gear 21 is rotating.

[0049] By utilizing this property, the electric pump A is equipped with a pump switching unit T that takes driving force from the ring gear 22 by stopping the rotation of the carrier 25 and takes driving force from the carrier 25 by stopping the rotation of the ring gear 22.

[0050] The pump switching unit T includes an electromagnetic switching valve V and a flow path selection valve 8. As shown in Fig. 1 and Fig. 2, it has a spool that is housed movably in a spool hole formed in the fourth housing 4, and this spool has land portions 8a formed at both ends in the longitudinal direction. In addition, a compression coil type spring 10 that applies pressure to one end of this flow path selection valve 8 is housed in the spool hole, and a pressure chamber 11 that can apply the pressure of hydraulic oil to the other end of this flow path selection valve 8 is formed.

[0051] Furthermore, the flow path selection valve 8 selectively closes one of the first discharge path 7a through which the hydraulic oil is delivered from the first pump mechanism Pa and the second discharge path 7b through which the hydraulic oil is delivered from the second pump mechanism Pb by operating a spool, enabling control to deliver lubricating oil from the other path through a discharge port 7P. The second discharge path 7b is provided with a check valve 12 that opens and closes by the operation of a ball to prevent reverse flow of the hydraulic oil.

[0052] The flow passage selection valve 8 is configured to be freely switchable between a first selection position shown in Fig. 1 and a second selection position shown in Fig. 2. In the first selection position, one land portion 8a closes the second discharge passage 7b, allowing the first discharge passage 7a to communicate with the discharge port 7P. Conversely, in the second selection position, the other land portion 8a closes the first discharge passage 7a, allowing the second discharge passage 7b to communicate with the discharge port 7P.

[0053] The solenoid switching valve V controls the flow of hydraulic oil in a first control flow passage 13a to which hydraulic oil is supplied from the discharge port 7P and a second control flow passage 13b that communicates with the pressure chamber 11. When the electromagnetic solenoid is not energized, this solenoid switching valve V does not supply hydraulic oil to the second control flow passage 13b, and reduces the pressure in the pressure chamber 11. As a result, the biasing force of the spring 10 sets the flow passage selection valve 8 to the first selection position shown in FIG.

[0054] In response to this, by energizing the electromagnetic solenoid, hydraulic oil is supplied from the first control flow path 13a to the second control flow path 13b, and pressure is applied to the pressure chamber 11 from the discharge port 7P. As a result, the flow path selection valve 8 is set to the second selection position shown in FIG.

[0055] The pump switching unit T may be configured to reduce the pressure in the pressure chamber 11 when the electromagnetic solenoid of the electromagnetic switching valve V is energized, and to increase the pressure in the pressure chamber 11 when the electromagnetic solenoid is not energized.

[0056] Although not shown in the drawings, the control unit C detects the temperature of the hydraulic oil using an oil temperature sensor (not shown), and if the detected oil temperature is below a set value, the control unit C controls the solenoid switching valve V to set the flow path selection valve 8 to the first selection position, and if the detected oil temperature exceeds the set value, the control unit C sets the flow path selection valve 8 to the second selection position.

[0057] In other words, when the temperature of the hydraulic oil is below a set value, the control unit C drives the electric motor M to rotate and controls the solenoid of the solenoid switching valve V not to energize, thereby reducing the pressure in the pressure chamber 11 and setting the flow path selection valve 8 to the first selection position shown in Figure 1 by the biasing force of the spring 10.

[0058] As a result, in the first selection position, the second pump mechanism Pb cannot discharge hydraulic oil, and the second inner rotor 33 is prevented from rotating. Therefore, the transmission G maintains a state in which the carrier 25 is fixed, and the ring gear 22 rotates, so that the rotational force of the ring gear 22 is transmitted from the first drive shaft Sa to the first pump mechanism Pa, and as a result, the first pump mechanism Pa is driven and hydraulic oil is sent out to the first discharge passage 7a. When hydraulic oil is supplied to the first discharge passage 7a in this manner, the pressure of the hydraulic oil opens the check valve 12 as shown in FIG. 1.

[0059] On the other hand, when the temperature of the hydraulic oil exceeds the set value, the control unit C controls the electric motor M to rotate and energizes the electromagnetic solenoid of the electromagnetic switching valve V, thereby increasing the pressure in the pressure chamber 11 and setting the flow path selection valve 8 to the second selection position shown in Figure 2 against the biasing force of the spring 10.

[0060] As a result, the first pump mechanism Pa cannot discharge hydraulic oil, and the rotation of the first inner rotor 31 is prevented. Therefore, the transmission G maintains a state in which the ring gear 22 is fixed, and the carrier 25 rotates, so that the rotational force of the carrier 25 is transmitted from the second drive shaft Sb to the second pump mechanism Pb, and as a result, the second pump mechanism Pb is driven and hydraulic oil is sent to the second discharge passage 7b. When hydraulic oil is sent to the second discharge passage 7b in this manner, the pressure of the first discharge passage 7a decreases, so that the check valve 12 is closed as shown in FIG. 2. For example, even if hydraulic oil leaking from the flow passage selection valve 8 tries to flow in the direction of the first discharge passage 7a, the check valve 12 prevents the flow.

[0061] [Effects of the embodiment] In this way, since the transmission unit G is housed inside the motor rotor 16 of the electric motor M, it is possible to reduce the driving force of the electric motor M and transmit it to the pump unit P without increasing the size of the electric pump A. In addition, since the transmission unit G is configured as a planetary gear type, the transmission unit G does not increase the size of the electric pump A as a whole.

[0062] In this electric pump A, the yoke 16a that constitutes the motor rotor 16 of the electric motor M has a cylindrical portion that opens toward the pump section P, and this cylindrical portion is supported on the protruding portion 2a by a bearing 17, thereby achieving stable rotation of the motor rotor 16.

[0063] Furthermore, since the diameter of the second outer rotor 34 of the second pump mechanism Pb is larger than the diameter of the first outer rotor 32 of the first pump mechanism Pa, the frictional force acting during rotation is greater than the frictional force acting on the first pump mechanism Pa.

[0064] When the temperature of the hydraulic oil detected by the oil temperature sensor is below a set value, the viscosity of the hydraulic oil is high. For this reason, when the temperature of the hydraulic oil is below a set value, the control unit C controls the pump switching unit T to drive the first pump mechanism Pa, thereby driving the electric motor M with a current less than that required to drive the second pump mechanism Pb, thereby enabling the supply of hydraulic oil.

[0065] On the other hand, when the temperature of the hydraulic oil exceeds the set value, the viscosity of the hydraulic oil is low (lower than the viscosity at high temperatures). For this reason, when the temperature of the hydraulic oil exceeds the set value, the control unit C controls the pump switching unit T to drive the second pump mechanism Pb, thereby enabling the supply of hydraulic oil by driving the second pump mechanism Pb without supplying a large current.

[0066] In particular, when driving the second pump mechanism Pb, the second pump mechanism Pb is driven at the most efficient rotational speed (number of rotations per unit time), and the electric motor M is driven at the most efficient rotational speed, thereby achieving the most efficient supply of hydraulic oil.

[0067] In other words, the rotational speed at which the pump section P most efficiently supplies hydraulic oil is different from the rotational speed at which the electric motor M most efficiently rotates. For this reason, when the electric pump A supplies a set flow rate of hydraulic oil required for the vehicle, the second pump mechanism Pb is driven at a rotational speed (revolutions per unit time) that provides the most efficiency, and the gear ratio in the transmission section G (the gear ratio transmitted via the second drive shaft Sb) is set so that the electric motor M is driven at a rotational speed that provides the most efficiency.

[0068] By setting the rotation speed in this manner, for example, compared to a configuration in which the rotation of the electric motor M is transmitted without changing the speed to rotate the pump section P at high speed, it is possible to drive with improved quietness and there is no wasteful consumption of current because the electric motor M is driven efficiently. Also, because the first pump mechanism Pa is driven in a situation in which no current is applied to the electromagnetic solenoid of the solenoid switching valve V, there is no need to supply current to the electromagnetic solenoid in a situation in which a large amount of current is required in the vehicle, such as when starting the vehicle engine.

[0069] [Another embodiment] The present invention may be configured as follows other than the above-described embodiment (common numbers and symbols as in the embodiment are used to designate components having the same functions as in the embodiment).

[0070] The electric pump A is configured as in the alternative embodiments (a) to (d). The configurations of these alternative embodiments (a) to (d) are shown in Fig. 4 to Fig. 7, respectively, and in each of the alternative embodiments, the configuration of the electric motor M is the same as that of the electric motor M in the embodiment, and the configuration in which the speed change unit G is accommodated in the internal space (the space inside the yoke 16a) of the motor rotor 16 of the electric motor M is the same as in the embodiment, but the pump unit P is of a single internal gear type, and the configuration of the speed change unit G is different from that in the embodiment.

[0071] In the alternative embodiments (a) to (d), the pump section P is housed in a hole-like section that vertically penetrates the third housing 3, and is disposed at a position where it is sandwiched from above and below between the lower surface of the second housing 2 and the fourth housing 4. Also, a suction port 6P and a discharge port 7P are formed in the lower surface of the fourth housing 4.

[0072] Incidentally, the electric pump A can be used in any position, but in these other embodiments, the positional relationship of each part will be described with the up-down direction fixed as shown in Figs.

[0073] 4(a), an electric pump A accommodates a planetary gear type transmission G in the internal space of a cylindrical yoke 16a of a motor rotor 16. As in the embodiment, the transmission G includes a sun gear 21, a ring gear 22, a planetary gear 23, and a pair of carriers 25 supported by a support shaft 24. The lower end of the yoke 16a of an electric motor M is rotatably supported by a protruding portion 2a of a housing H via a bearing 17.

[0074] Furthermore, the lower end of the ring gear 22 of the transmission unit G is fixed in an externally fitted state to the protruding portion 2a of the housing H, and the lower of the pair of carriers 25 of the transmission unit G is connected to the drive shaft S, and this drive shaft S is connected to the inner rotor of the pump unit P.

[0075] In the electric pump A of this alternative embodiment (a), the driving force of the electric motor M is reduced in speed change section G and transmitted to the drive shaft S, and the driving force of the drive shaft S is transmitted to the pump section P. As a result, the pump section P draws in hydraulic oil from the suction port 6P and delivers the hydraulic oil from the discharge port 7P.

[0076] In the electric pump A of this alternative embodiment (a), the transmission unit G is made compact by using a planetary gear, and the compact transmission unit G is accommodated in the internal space of the motor rotor 16, thereby making the entire electric pump A compact.

[0077] In addition, in the electric pump A of the alternative embodiment (a), the gear ratio of the transmission G is set so that the pump section P is driven at the most efficient rotational speed and the electric motor M is driven at the most efficient rotational speed when the hydraulic oil is supplied to the vehicle at a set flow rate. This setting of the gear ratio suppresses wasteful consumption of energy when the electric pump A is operating.

[0078] 5(b), electric pump A accommodates planetary gear type transmission G in the internal space of cylindrical yoke 16a of motor rotor 16. Transmission G includes ring gear 22 that rotates integrally with yoke 16a on the inner periphery of yoke 16a, sun gear 21 on the upper end of drive shaft S, and a plurality of planetary gears 23 that mesh with ring gear 22 and sun gear 21. Electric motor M has a lower end of its yoke 16a supported rotatably on protruding portion 2a of housing H by bearing 17.

[0079] Furthermore, by supporting shafts 24 of a plurality of planetary gears 23 of this transmission unit G on the protruding portion 2a of the second housing 2, this transmission unit G is configured as a speed increasing type (an example of a speed changing type). This transmission G can be considered as a planetary type with a fixed carrier 25.

[0080] In the electric pump A of this alternative embodiment (b), the ring gear 22 is rotated by the driving force of the electric motor M, and this rotation is transmitted from the sun gear 21 to the drive shaft S via a plurality of planetary gears 23, and the driving force of the drive shaft S is transmitted to the pump section P. Note that the speed-changing section G of this alternative embodiment (b) is of the speed-increasing type, and as a result, the pump section P is driven at a speed higher than the rotational speed (number of rotations per unit time) of the electric motor M.

[0081] 6, an electric pump A has a cylindrical yoke 16a of a motor rotor 16 rotatably disposed about a drive shaft core X, and a lower end of the yoke 16a is rotatably supported by a bearing 17 on a protruding portion 2a of a housing H. A transmission G is accommodated in the internal space of the yoke 16a.

[0082] In the electric pump A of this alternative embodiment (c), the transmission G includes a pinion gear 41 (an example of an output gear) that rotates integrally with the rotor plate 18 fixed to the upper end of the motor rotor 16, and is disposed in a downwardly protruding position. The transmission G also includes a cylindrical gear 42 (an example of an input gear) on the upper end of the drive shaft S, the cylindrical gear 42 having internal teeth that mesh with the pinion gear 41, and transmits the driving force of the drive shaft S to the pump section P.

[0083] The transmission unit G is configured as a reduction type in which the number of teeth of the cylindrical gear 42 is greater than the number of teeth of the pinion gear 41. The drive shaft S is rotatably supported by the protruding portion 2a of the housing H so as to be rotatable about a driven shaft center Y that is parallel to a drive shaft center X. Therefore, the driving force of the electric motor M is reduced in speed (changed in speed) by the transmission unit G and transmitted from the drive shaft S to the pump unit P, thereby driving the pump unit P, and the hydraulic oil sucked in from the suction port 6P is discharged from the discharge port 7P.

[0084] In this alternative embodiment (c), the electric pump A is made smaller by accommodating the transmission unit G in the internal space of the motor rotor 16. In addition, in the electric pump A of this alternative embodiment (c), the gear ratio of the transmission unit G is set so that, when supplying hydraulic oil at a set flow rate required for the vehicle, the pump unit P is driven at the most efficient rotational speed and the electric motor M is driven at the most efficient rotational speed. Setting the gear ratio in this way reduces unnecessary energy consumption when the electric pump A is operating.

[0085] 7, an electric pump A has a cylindrical yoke 16a of a motor rotor 16 rotatably disposed about a drive shaft core X, and a lower end of the yoke 16a is rotatably supported by a bearing 17 on a protruding portion 2a of a housing H. A transmission G is accommodated in the internal space of the yoke 16a.

[0086] In the electric pump A of this alternative embodiment (d), the speed change section G is composed of an internally toothed driving gear section 44 formed on the inner periphery of the yoke 16a of the motor rotor 16, and an externally toothed driven gear 45 meshing with the internally toothed driving gear section 44. The driven gear 45 is provided on the upper end of the drive shaft S, and the driving force from the drive shaft S is transmitted to the inner rotor of the pump section P.

[0087] The transmission unit G is configured as a speed-increasing type in which the number of teeth of the internally toothed drive gear portion 44 is greater than the number of teeth of the driven gear 45. The drive shaft S is rotatably supported by the protruding portion 2a of the housing H so as to be rotatable about a driven shaft center Y that is parallel to the drive shaft center X. Therefore, the driving force of the electric motor M is increased (changed) in the transmission unit G and transmitted from the drive shaft S to the pump portion P to drive the pump portion P, and the hydraulic oil sucked in from the suction port 6P is discharged from the discharge port 7P.

[0088] In this alternative embodiment (d), the electric pump A is made smaller by accommodating the speed change unit G in the internal space of the motor rotor 16. In addition, the speed change unit G of the electric pump A in this alternative embodiment (d) is of the speed increasing type, and as a result, the pump unit P is driven at a speed higher than the rotation speed (number of rotations per unit time) of the electric motor M.

[0089] (e) The transmission G is not limited to the reduction gear structure shown in the embodiment and the other embodiments, and may be one that changes the speed using a plurality of gears. Even if the transmission G has such a configuration, the electric pump A can be made smaller by accommodating it in the internal space of the motor rotor 16.

[0090] (f) As in the embodiment, two pump mechanisms are used, and the flow path selection valve 8 of the embodiment is configured as an electromagnetically operated type operated by an electromagnetic solenoid as a pump switching unit T that selects between operating and stopping the two pump mechanisms, without providing an electromagnetic switching valve V. By configuring in this way, the number of parts can be reduced, making it possible to reduce the size. [Industrial Applicability]

[0091] The present invention can be used in an electric pump. [Explanation of symbols]

[0092] 2a Protrusion 6P suction port 7P discharge port 8 Flow path selection valve (pump switching section) 15 Field coil 16 Motor rotor 16a York 16b Permanent magnet 17 Bearings 21 Sun gear 22 Ring gear 23 Planetary Gear 25 Career 31 First inner rotor 32 First outer rotor 33 2nd inner rotor 34 2nd outer rotor 41 Pinion gear (output gear) 42 Cylindrical gear (input gear) G Shift section H Housing M Electric motor P Pump section Pa First pump mechanism Pb Second pump mechanism S Drive shaft Sa 1st drive shaft Sb Second drive shaft T Pump switching section V Solenoid switching valve (pump switching section) X Drive shaft core

Claims

1. an electric motor having a field coil disposed in an annular region centered on a drive shaft, and a motor rotor supported rotatably about the drive shaft and rotated by the action of a magnetic field of the field coil; a speed change unit that changes the speed of the rotation of the motor rotor and transmits the rotation to a drive shaft; a pump section driven by the driving force of the drive shaft; a housing that accommodates the electric motor, the transmission, the drive shaft, and the pump, The motor rotor includes a permanent magnet on an outer circumferential side of a cylindrical yoke centered on the drive shaft, and the speed change unit is accommodated in an internal space of the yoke. the housing has a protrusion protruding toward the transmission unit inside the housing so as to support the drive shaft in a penetrating state, a bearing that rotatably supports the motor rotor is supported in contact with the protruding portion;

2. The electric pump of claim 1, wherein the transmission unit is configured as a planetary gear type that includes a sun gear, a ring gear arranged in a region surrounding the sun gear, and a plurality of planetary gears that mesh with the sun gear and the ring gear, thereby changing the speed of the driving force transmitted from the motor rotor and transmitting it to the drive shaft.

3. the transmission unit has an output gear provided in the internal space of the yoke so as to rotate integrally with the motor rotor around the drive shaft core, and an input gear provided in the internal space so as to mesh with the output gear, 2. The electric pump according to claim 1, wherein the rotational force of the input gear is transmitted from the drive shaft to the pump section.

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