Electrically operated hydraulic pump

An electrically operated hydraulic pump having a pump portion and a motor portion includes rotation controlling means controlling rotation of a rotor, first rotor position detecting means detecting rotational position of the rotor on the basis of speed electromotive force induced by exciting coils, second rotor position detecting means detecting the rotational position of the rotor on the basis of magnetic field of a magnet provided at the motor portion, and motor operating condition detecting means detecting operating condition of the motor portion. The rotation controlling means switches a first rotation controlling based on the rotational position of the rotor detected by the first rotor position detecting means, and a second rotation controlling based on the rotational position of the rotor detected by the second rotor position detecting means, on the basis of a result detected by the motor operating condition detecting means.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2006-262669, filed on Sep. 27, 2006, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an electrically operated hydraulic pump which includes a pump portion and a motor portion including a brushless DC motor, and which detects a rotational position of the rotor included in the motor, on the basis of speed electromotive force induced by exciting coils of the motor portion.

BACKGROUND

An electrically operated hydraulic pump is used for supplying operating oil as fluid to a clutch of an automatic transmission mounted on a vehicle such as an automobile, or for supplying cooling oil as fluid to an electric motor mounted on a hybrid type vehicle, and so on. A mechanical hydraulic pump, an electrically operated hydraulic pump, and so on can be employed as a pump mounted on a vehicle. The mechanical hydraulic pump uses driving force of an engine of the vehicle, while the driving force of the engine is not required to the electrically operated hydraulic pump. Before starting the engine, or immediately after the engine started, effective hydraulic pressure is not supplied from the mechanical hydraulic pump. Accordingly, there is a requirement to employ the electrically operated hydraulic pump in such situations.

A conventional electronic operated hydraulic pump is described in Japanese Patent No. 2002-317772 A (hereinafter, referred to as a reference 1). The electrically operated hydraulic pump according to the reference 1 includes a motor portion and a pump portion. The motor portion structures a sensor-less brushless DC motor. The pump portion absorbs and exhausts fluid by means of driving force of a rotating shaft driven by the motor portion. The motor portion includes a stator, a rotor and rotation controlling means. The stator includes plural exciting coils for generating a magnetic field. The rotor includes a magnet which faces the exciting coils and is arranged to be rotatable with the rotating shaft in a space inside of a resin-mold and closed-bottom cylindrical motor housing. The rotation controlling means controls rotation of the rotor by switching electric current of the exciting coils in accordance with a rotating position of the rotor. Further according to the electrically operated hydraulic pump in the reference 1, a fluid returning path is formed between the motor portion and the pump portion. Fluid flowing into a space inside the motor from the pump portion can be returned to the pump portion through the fluid returning path. In other words, the fluid circulates between the pump portion and the space inside the motor portion and therefore, the space of the motor portion, i.e., the stator and the rotor, is cooled. However, when temperature of the fluid is low and viscosity of the fluid is high, rotational resistance for the rotor may be increased because of the fluid adhering to the rotor inside the space of the motor.

As described above, according to the electrically operated hydraulic pump in reference 1, the sensor-less DC motor is employed so that there is an advantage that any particular apparatus for detecting a rotational position or the rotor position, or the like, may not be provided. Further, there is another advantage that the pump can be downsized because any particular apparatus for cooling the rotor of the motor portion, or the like, may not be provided.

The electrically operated hydraulic pump according to the reference 1 detects the rotational position of the rotor on the basis of speed electromotive force induced by the exciting coils. Accordingly, when the rotational speed of the rotor is high, detection precision of the rotational position of the rotor is also increased. However, when the rotation speed of the rotor is not high, the detection precision of the rotational position of the rotor may be decreased. Here, when the temperature of the fluid is low, the rotational speed of the rotor lowers because the viscosity of the fluid is high, i.e., because the fluid may become large rotational resistance to the rotor. Accordingly, when the temperature of the fluid is high, the detection precision of the rotational position of the rotor is increased, while when the temperature of the fluid is low, the detection precision of the rotor rotational position may be lowered. Specifically, before starting the engine or immediately after the engine started, i.e., before the motor is operated or immediately after the motor is operated, the temperature of the fluid may be low and the rotational speed of the rotor may not be increased because the viscosity of the fluid may be high. Accordingly, there is a possibility that the detection precision of the rotor is decreased. Consequently, the rotation of the motor may not be controlled adequately.

A need thus exists for an electrically operated hydraulic pump which is not susceptible to the drawback mentioned above.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an electrically operated hydraulic pump includes a motor portion and a pump portion. The motor portion of the electrically operated hydraulic pump includes a hollow and cylindrical motor housing with a bottom and an opening, and a brushless DC motor having a stator which is fixedly provided in the motor housing, a plurality of exciting coils which generates magnetic field, and a rotating shaft which is arranged at a space in the motor housing to be rotatable relative to the stator. The brushless DC motor of the motor portion further has a rotor which is arranged at the space in the motor housing and fixed to the rotating shaft, the rotor which includes a first magnet facing the exciting coils, and rotation control means which controls a rotation of the rotor by switching energizing electric current flow from an exciting coil to another exciting coil, from among the exciting coils in accordance with a rotational position of the rotor. The pump portion of the electrically operated hydraulic pump, which is connected to one end of the rotating shaft, absorbs and exhausts fluid by driving force of the rotating shaft. The electrically operated hydraulic pump further includes first rotor position detecting means, second rotor position detecting means, and motor operating condition detecting means. The first rotor position detecting means includes speed electromotive force detecting means for detecting speed electromotive force induced by the exciting coils and detects the rotational position of the rotor on the basis of a result detected by the speed electromotive force detecting means. The second rotor position detecting means includes a second magnet which is provided at the rotating shaft, and a magnetic field detecting unit which detects magnetic field of the second magnet. The second rotor position detecting means detects the rotational position of the rotor on the basis of a result detected by the magnetic field detecting unit. The motor operating condition detecting means detects an operating condition of the motor portion. The electrically operated hydraulic pump according to the aspect of the present invention is characterized in that the rotation control means of the motor portion is configured to switch a first rotation controlling based on the rotational position of the rotor detected by the first rotor position detecting means and a second rotation controlling based on the rotational position of the rotor detected by the second rotor position detecting means, on the basis of a result detected by the motor operating condition detecting means.

DETAILED DESCRIPTION

An embodiment of the electrically operated hydraulic pump according to the present invention will be described hereinafter with reference to attachedFIGS. 1 through 4.FIG. 1is a longitudinal sectional view schematically illustrating an entire structure of the electrically operated hydraulic pump.FIG. 2is a functional block diagram illustrating a second rotor position detecting means of the electrically operated hydraulic pump illustrated inFIG. 1.FIG. 3is a longitudinal sectional view illustrating in detail the electrically operated hydraulic pump.FIG. 4is a top view of the motor portion of the electrically operated hydraulic pump. As best shown inFIGS. 1 and 3, an electrically operated hydraulic pump1includes a motor portion M and a pump portion P. The motor portion M drives a rotating shaft14to rotate, by means of electric power supplied via a connecting portion11. The pump portion P is provided at one end of the rotating shaft14, and absorbs and exhausts fluid such as oil, water, or the like, by means of driving force of the rotating shaft14. The electrically operated hydraulic pump1according to the embodiment is employed, for example, for supplying fluid-type operating oil to a clutch of an automatic transmission mounted on a vehicle such as an automobile, or for supplying fluid-type cooling oil to an electric motor mounted on a hybrid type vehicle, or the like. Among pumps mounted on the vehicle, even when a mechanical hydraulic pump, which is operated by driving force of an engine of the vehicle, is not available for supplying effective hydraulic pressure before starting the engine of the vehicle, or immediately after the engine started, the electrically operated hydraulic pump1supplies the effective hydraulic pressure. Further, even when the mechanical hydraulic pump supplies the effective hydraulic pressure, the electrically operated hydraulic pressure1is also available.

As illustrated inFIG. 3, the electrically operated hydraulic pump1further includes a hollow and cylindrical motor housing10with a bottom10aand an opening, a pump body25and a pump cover36. The motor housing10structures the motor portion M and is made of resin. Here, the hollow and cylindrical motor housing10may be a cup-shaped housing. The pump body25and the pump cover36structure the pump portion P. Components of the electrically operated hydraulic pump1are accommodated in the motor housing10, in the pump body25and in the pump cover36. A seal member24is provided between the motor housing10and the pump body25. A seal member35is provided between the pump body25and the pump cover36. Accordingly, the motor housing10, the pump body25, and the pump cover36are assembled. The pump portion P closes the opening of the resin-made hollow and cylindrical motor housing10.

The motor housing10includes the connecting portion11and the motor portion M. The connecting portion11receives electric current from an external terminal (not illustrated) connected to the motor housing10. The motor portion M drives the rotating shaft14by means of the electric power supplied via the connecting portion11. Back toFIG. 1, the motor portion M includes a stator16and a rotor15. The stator16includes plural exciting coils18for generating magnetic field. The rotor15includes a magnet15a, which faces the exciting coils18. The magnet15ais arranged in a space13, which is formed inside of the hollow and cylindrical motor housing10, to be rotatable with the rotating shaft14. The motor portion M further includes a rotation controlling means43, which controls a rotation of the rotor15by switching energizing electric current from one exciting coil18to another exciting coil18, from among the exciting coils18, in accordance with a rotational position of the rotor15. As described above, the motor portion M of the electrically operated hydraulic pump1according to the embodiment includes a brushless DC motor.

More specifically, the rotor15of the motor portion M is fixedly provided relative to the rotating shaft14, and the stator16of the motor portion M is cylindrically provided around the rotor15with set space relative to the rotor15. The stator16includes a core17, a bobbin portion20and the exciting coils18. The core17is formed by laminating plural iron plates. The bobbin portion20is formed of insulative resin material and partially covers a surface of the core17. Each exciting coil18is wound around the bobbin portion20in a vertically circumferential direction, and the exciting coils18are arranged to surround the core17assuring insulation to the core17. Further, the resin-made bobbin portion20retains the stator16and terminal members12(12a,12band12c) which the connecting portion11includes. One end portion of each terminal member12is connected to the exciting coils18of the stator16, while the other end portion of each terminal member12structures a connecting terminal40of the connecting portion11. The terminal members12include plate-shaped metal material. Still further, a recessed portion22is formed at an outer surface of the bottom10aof the motor housing10to be coaxial with an axis X of the rotating shaft14. A diameter of the recessed portion22is arranged to be smaller than an inner diameter of the stator16.

As illustrated inFIG. 4, six tooth portions are provided surrounding the core17and three terminal members12a,12b, and12care applied with alternating electric current voltage. Each phase of the alternating electric current voltage to the terminal member12a, to the terminal member12b, and to the terminal member12cis different. Accordingly, the terminal member12b, a tooth portion19aand a tooth portion19dare in phase V (V phase). The terminal member12aand a tooth portion19band a tooth portion19eare in phase U (U phase), and further, the terminal member12c, a tooth portion19cand a tooth portion19fare in phase W (W phase).

Back toFIG. 3, the motor housing10is partially formed with a cylindrical portion including a closed-end portion and an opening portion. The connecting portion11includes the cylindrical portion and is configured in a manner where the connecting terminal40(i.e., the other end portions of the terminal members12) protrudes into the cylindrical portion of the motor housing10. Then, the external terminal, which supplies the electric power to the motor portion M, is inserted into the cylindrical portion so as to be in contact with the connecting terminal40.

The pump body25, which structures the pump portion P, contains a pump-operating portion26. The pump operating portion26absorbs and exhausts the fluid by means of rotational force of the rotating shaft14which is driven by the motor portion M. In the embodiment, a trochoid-type pump is employed as the pump operating portion26. The pump cover36accommodates an intake port37for intaking the fluid to the pump operating portion26, and an exhaust port38for exhausting the fluid from the pump operating portion26. The pump operating portion26includes an inner rotor27and an outer rotor28. The inner rotor27is arranged inside the outer rotor28, in a manner where external splines of the inner rotor27are engaged with internal splines of the outer rotor28. A bearing bore32is formed inside the pump body25and the rotating shaft14is inserted into the bearing bore32. Then, the inner rotor27is fixedly provided around the rotating shaft14, which is driven by the motor portion M, and is rotated with the rotating shaft14. Accordingly, plural pump operating chambers29are formed between the inner rotor27and the outer rotor28. A volume of each pump operating chamber29is changed to be increased or reduced, in accordance with the rotations of the inner and outer rotors27and28. When the volume of each pump operating chamber29is increased, negative pressure is generated inside each pump operating chamber29which is communicated to an intake chamber30. Therefore, the fluid flows into each pump operating chamber29through the intake port37and the intake chamber30. The fluid flowing into each pump operating chamber29is transferred to an exhaust port31in accordance with the rotation of the inner rotor27, and is exhausted from the exhaust port31. Accordingly, when the rotating shaft14is rotated by the driving force of the motor portion M, the fluid is sucked by the intake port37and is exhausted from the exhaust port38.

The electrically operated hydraulic pump1according to the embodiment is formed with a cutout portion33for communicating the exhaust chamber31with the bearing bore32, and is configured in order that the fluid comes out of a surface of the rotating shaft14. On the other hand, the electrically operated hydraulic pump1is not provided with any means for preventing the fluid from being transferred to the motor portion M from the pump operating portion26through the surface of the rotating shaft14. Accordingly, the fluid coming out from the pump operating portion26through the rotating shaft14flows into the space13of the motor portion M and is adhered to the rotor15, the stator16, and so on. Further according to the electrically operated hydraulic pump1, a returning path34is provided between the motor portion M and the pump portion P. The returning path34communicates the motor portion M with the intake chamber30so that the fluid flowing into the space13of the motor portion M can return to the pump portion P. Then, when the negative pressure is generated inside the intake chamber30, the fluid, which flows into the space13from the pump portion P, is partially sucked into the intake chamber30through the returning path34, because of the negative pressure. As described above, a fluid recirculation system, in which the fluid flows from the pump portion P to the motor portion M and returns to the pump portion P through the space13of the motor portion M and the returning path34, is established. Accordingly, the fluid assumes a role of cooling the rotor15, the stator16and so on by extracting heat of such components, in the space13of the motor portion M.

Next, operation of the electrically operated hydraulic pump1according to the embodiment will be described hereinafter. As described above, the electrically operated hydraulic pump1includes the motor portion M and the pump portion P. The motor portion M includes the brushless DC motor. The brushless DC motor includes the stator16having plural exciting coils18which generates the magnetic field, the rotor15having the magnet15awhich faces the exciting coils18and is arranged to be rotatable with the rotating shaft14in the space13of the resin-mold hollow and cylindrical motor housing10, and the rotation controlling means43for controlling the rotation of the rotor15by switching the electric current to the exciting coils18. Further, the electrically operated hydraulic pump1includes a fluid temperature detecting means45. The fluid temperature detecting means45corresponds to a motor operating condition detecting means44, which detects an operating condition of the motor portion M. The rotation controlling means43is configured to switch a first rotation controlling and a second rotation controlling, for controlling the rotation of the rotor15, on the basis of a result detected by the fluid temperature detecting means45serving as the motor operating condition detecting means44. In other words, according to the embodiment, fluid temperature detected by the fluid temperature detecting means45corresponds to an operating condition of the motor portion M. Here, the first rotation controlling is based on a rotational position of the rotor15detected by a first rotor position detecting means41, and the second rotation controlling is based on a rotational position of the rotor15detected by a second rotor position detecting means50.

The fluid temperature detecting means45includes at least either a fluid temperature measuring means45aor a fluid temperature estimating means45b. The fluid temperature detecting means45ameasures the temperature of the fluid directly, while the fluid temperature estimating means45bestimates the temperature of the fluid by means other than a fluid temperature parameter. As one of the parameter (i.e., the parameter relating to the temperature of the fluid), which the fluid temperature estimating means45butilizes for estimating the fluid temperature, for example temperature of cooling water (cooling water of a radiator) for cooling an internal combustion engine of a vehicle, can be used. According to the embodiment, the fluid temperature can be detected by using either the fluid temperature measuring means45aor the fluid temperature estimating means45b. Further, either a result of the fluid temperature detected by the fluid temperature measuring means45aor a result of the fluid temperature detected by the fluid temperature estimating means45bis selectively employed on the basis of a certain condition.

The fluid temperature detecting means45may detect the temperature of the fluid flowing in the pump portion P, or may detect temperature of the fluid in the space13of the motor portion13. In a case where the fluid temperature detecting means45detects temperature of the fluid flowing in the pump portion P, for example, the fluid temperature detecting means45(here, corresponding to the fluid temperature measuring means45a) may be provided at a fluid flowing channel (not illustrated) communicated with the intake port37or with the exhaust port38. On the other hand, in a case where the fluid temperature detecting means45detects the temperature of the fluid flowing in the space13of the motor portion M, the fluid temperature detecting means45(here, corresponding to the fluid temperature measuring means45a) may be provided in the space13of the motor portion M. According to the embodiment, the fluid temperature detecting means45may be provided wherever possible, as long as the fluid temperature detecting means45are arranged to detect the temperature of the fluid.

More specifically, when the fluid temperature detected by the fluid temperature detecting means45is higher than a set temperature condition, the rotation controlling means43controls the rotation of the rotor15on the basis of the rotational position of the rotor15detected by the first rotor position detecting means41, i.e., the rotation controlling means43implements the first rotation controlling. On the other hand, when the fluid temperature detected by the fluid temperature detecting means45is lower than the set temperature condition, the rotation controlling means43controls the rotation of the rotor15on the basis of the rotational position of the rotor15detected by the second rotor position detecting means50, i.e., the rotation controlling means43implements the second rotation controlling.

The first rotor position detecting means41includes a speed electromotive force detecting means42, and detects the rotational position of the rotor15on the basis of a result detected by the speed electromotive force detecting means42, which detects speed electromotive force induced by the exciting coils18. More specifically, as illustrated inFIG. 4, the speed electromotive force detecting means42outputs a detected result regarding a zero cross point of the speed electromotive force, which is induced by each of U phase, V phase, and W phase, of non-energized exciting coils18. Consequently, the first rotational position detecting means41can detect the rotational position of the rotor15on the basis of the speed electromotive force detecting means42.

The second rotor position detecting means50includes a sensor unit52, which is located at opposite of the pump portion P, i.e., which is located at the other end of the rotating shaft11, and serves as a magnetic field detecting unit. The sensor unit52detects magnetic field from a magnet21(for example, a dipolar permanent magnet) provided at the other end of the rotating shaft14. Further, the sensor unit52includes a plurality of hole IC and detects magnetic field formed by the permanent magnet21, at an outside of the bottom portion10aof the motor housing10. Then, the second rotor position detecting means50detects the rotational position of the rotor15on the basis of the result detected by the sensor unit52. More specifically, the second rotor position detecting means50includes a memory unit51and a calculation processing unit53. The memory unit51memorizes a relationship between the rotational position of the rotor15and the magnetic field detected by the sensor unit52. The calculation processing unit53calculates the rotational position of the rotor15on the basis of the relationship memorized in the memory unit51and the result detected by the sensor unit52. Then, information regarding the calculated rotational position of the rotor15is outputted from an output unit54, which is included in the second rotor position detecting means50, to the rotation controlling means43. As described above, the memory unit51memorizes the relationship between the rotational position of the rotor15and the magnetic field detected by the sensor unit52. Accordingly, the calculation processing unit53readily and accurately calculates the rotational position of the rotor15.

As described above, the sensor unit52, which is included in the second rotor position detecting means50, detects the magnetic field formed by the permanent magnet21, which is provided at the other end of the rotating shaft14and is arranged in the space13of the motor housing10, from the outside of the motor housing10. Accordingly, it is preferable that a distance between the sensor unit52and the permanent magnet21is smaller. According to the embodiment, the recessed portion22, of which diameter is smaller than the inner diameter of the recessed portion22, is formed at the outer surface of the bottom portion10aof the motor housing10to be coaxial with the rotating shaft14. The sensor unit52of the second rotor position detecting means50is provided at the recessed portion22. Accordingly, the sensor unit52can detect the magnetic field formed by the permanent magnet21provided at the second end of the rotating shaft14, with higher sensitivity. Therefore, the detection precision of the sensor unit52to detect the rotational position of the rotor15may be enhanced. Further, according to the embodiment, a recess23is formed at a center of the recessed portion22formed at the outside of the bottom portion10aof the motor housing10. Then, the sensor unit52of the second rotor position detecting means50is provided at the recess23formed at the recessed portion22. Here, a position to provide the permanent magnet21relative to the rotating shaft14, and a position to provide the sensor unit52of the second rotor position detecting means50are not limited to the configuration described above and can be modified.

Here, in a case where the temperature of the fluid is low, the viscosity of the fluid is higher (i.e., the fluid can become large rotational resistance to the rotor15). Therefore, the rotational speed of the rotor15is lowered. On the other hand, in a case where the temperature of the fluid is high, the viscosity of the fluid is lower (i.e., the rotor15may not be the large rotational resistance to the rotor15). Therefore, the rotational speed of the rotor15is increased. Accordingly, when the temperature of the fluid becomes higher (i.e., the rotational speed of the rotor15becomes higher), the first rotor position detecting means41detects the rotational position of the rotor15with higher detection precision. However, when the temperature of the fluid becomes lower (i.e., when the rotational speed of the rotor15becomes lower), the first rotor position detecting means41may detect the rotational position of the rotor15with lower detection precision. On the other hand, even when the temperature of the fluid is low (i.e., the rotational speed of the rotor15is low), the second rotor position detecting means50detects the rotational position of the rotor15with sufficiently high detection precision. However, when the temperature of the fluid rises, temperature of the permanent magnet21fixedly provided at the rotating shaft14also rises. Accordingly, magnetic force of the permanent magnet21becomes weaker, and the detection precision of the second rotor position detecting means50, to detect the rotational position of the rotor15, may be weaken.

Accordingly, when the fluid temperature detected by the fluid temperature detecting means45is higher than the set temperature condition (for example, when the fluid temperature is equal to, or higher than a set temperature threshold value), the rotation controlling means43controls the rotation of the rotor15on the basis of the first rotor position detecting means41, i.e., the rotation controlling means43implements the first rotation controlling. On the other hand, when the fluid temperature detected by the fluid temperature detecting means45is lower than the set temperature condition (for example, when the temperature of the fluid is equal to, or lower than the set temperature value), the rotation controlling means43controls the rotation of the rotor15on the basis of the second rotor position detecting means50, i.e., the rotation controlling means43implements the second rotation controlling.

As described above, the rotation controlling means43switches the first rotation controlling based on the result detected by the first rotor position detecting means and the second rotation controlling based on the result detected by the second rotor position detecting means, for controlling the rotation of the rotor15. Therefore, a phenomenon such that the detection precision of the first rotor position detecting means to detect the rotational position of the rotor15lowers when the fluid temperature is low (i.e., when the rotational speed of the rotor15is low), and a phenomenon such that the detection precision of the second rotor position detecting means to detect the rotational position of the rotor15lowers when the fluid temperature is high (i.e., when the rotational speed of the rotor15is high), may be solved.

According to the electrically operated hydraulic pump1of the present invention, the above-described set temperature condition is appropriately set in accordance with a temperature characteristic of the fluid, the characteristic of the motor portion M, and so on. For example, the set temperature condition includes a set temperature threshold value assigned as zero degree Celsius. In such a case, the rotation controlling means43controls the electric current to the exciting coils18in accordance with the rotational position of the rotor15detected by the second rotor position detecting means50, when the fluid temperature is lower than zero degree Celsius upon the fluid temperature rising. When the fluid temperature becomes equal to, or higher than zero degree Celsius upon the fluid temperature rising, the rotation controlling means43controls the electric current to the exciting coils18in accordance with the rotational position of the rotor15detected by the first rotor position detecting means41. Further, when the fluid temperature becomes equal to, or lower than zero degree Celsius upon the fluid temperature being lowered, the rotation controlling means43controls the electric current to the exciting coils18in accordance with the rotational position of the rotor15detected by the second rotor position detecting means50.

Modified Embodiments

(1) In the aforementioned embodiment, a configuration of the motor operating condition detecting means44is described such that the motor operating condition detecting means44corresponds to the fluid temperature detecting means45, and the operating condition of the motor portion M corresponds to the fluid temperature detected by the fluid temperature detecting means45. Alternatively, modified configurations of the motor operating condition detecting means44may be employed. For example, the operating condition of the motor portion M detected by the motor operating condition detecting means44may correspond to a rotational speed of the motor portion M (i.e. the rotational speed of the rotor15). Here, the rotation controlling means43can recognize not only the rotational position of the rotor15, but also the rotational speed of the rotor15, on the basis of the result detected by the first rotor position detecting means41or the second rotor position detecting means50. Accordingly, at least either the first rotor position detecting means41or the second rotor position detecting means50may be employed as the operation condition detecting means44. Then, the rotation controlling means43is configured to switch the first rotation controlling, which is based on the rotational position of the rotor15detected by the first rotor position detecting means41, and second rotation controlling, which is based on the rotation position of the rotor15detected by the second rotor position detecting means50, on the basis of a result detected by the motor operating condition detecting means44.

More specifically, when the rotation speed of the rotor15is higher than a set rotational speed condition, the rotation controlling means43controls the rotation of the rotor15on the basis of the rotational speed of the rotor15detected by the first rotor position detecting means41, i.e., the rotation controlling means43implements the first rotation controlling. On the other hand, when the rotation speed of the rotor15is lower than the set rotational speed condition, the rotation controlling means43controls the rotation of the rotor15on the basis of the second rotor position detecting means50, i.e., the rotation controlling means43implements the second rotation controlling. Accordingly, a phenomenon such that the detection precision of the first rotor position detecting means41to detect the rotational position of the rotor15lowers when the rotational speed of the rotor15is low (i.e., when the fluid temperature is low) and a phenomenon such that the detection precision of the second rotor position detecting means50to detect the rotational position of the rotor15lowers when the rotational speed of the rotor15is high (i.e., when the fluid temperature is high) may be solved. In addition, the rotation controlling means43is configured to switch the first rotation controlling, which is based on the rotational position of the rotor15detected by the first rotor position detecting means41, and the second rotation controlling, which is based on the rotation position of the rotor15detected by the second rotor position detecting means50, on the basis of a combination of the set temperature condition and the set rotational speed condition, both which are described above.

(2) In the embodiment described above, the set condition of the fluid temperature is defined as one set temperature threshold value. Alternatively, the set condition of the fluid temperature may include plural set temperature threshold values. For example, the set condition of the fluid temperature may include first set temperature threshold value, which is employed when the fluid temperature is rising, and a second set temperature threshold value, which is set to be lower than the first set temperature threshold value and is employed when the fluid temperature is being lowered. An operation of the rotation controlling means43, in a condition where the first set temperature threshold value is assigned as zero degree Celsius and the second set temperature threshold value is assigned as ten degrees Celsius below zero, will be described hereinafter. In such a case, when the fluid temperature is rising and the value of fluid temperature is below zero degree Celsius, the rotation controlling means43controls the electric current to the exciting coils18in accordance with the rotational position of the rotor15detected by the second rotor position detecting means50. When the fluid temperature is rising and the value of the fluid temperature exceeds zero degree Celsius, the rotation controlling means43controls the electric current to the exciting coils18in accordance with the rotational position of the rotor15detected by the first rotor position detecting means41. Further, when the fluid temperature is being lowered and the value of the fluid temperature lowers to 10 degrees Celsius below zero, the rotation controlling means43controls energizing the electric current to the exciting coils18in accordance with the rotational position of the rotor15detected by the second rotor position detecting means50.

According to a condition where the set condition of the fluid temperature is defined as one set temperature threshold value as described in the aforementioned embodiment, the rotation controlling means43is required to switch the first rotation controlling, which is based on the rotational position of the rotor15detected by the first rotor position detecting means41, and the second rotational control, which is based on the rotation position of the rotor15detected by the second rotor position detecting means50, every time the fluid temperature rises over and lowers below the set temperature threshold value. In other words, when the fluid temperature is at a value around the set temperature threshold value, control hunting may occur. However, as described above, the set temperature threshold value upon the fluid temperature rising and the set temperature threshold value upon the fluid temperature being lowered may be set by different values. Therefore, the control hunting described above may be prevented from being generated.

In the same manner, as described in the modified embodiment (1), when the operating condition of the motor portion M (rotor15) detected by the motor operating condition detecting means44corresponds to the rotational speed of the motor portion M (rotor15), the set rotational speed condition may include plural set rotational speed threshold values. For example, the set rotational speed condition may include a first set rotational speed threshold value, which is employed when the rotational speed of the rotor14is rising, and a second set rotational speed threshold value, which is set to be lower than the first set rotational speed threshold value and is employed when the fluid temperature is being lowered.

(3) According to the electrically operated hydraulic pump in the embodiment described above, the pump portion P is arranged to close the opening of the motor housing10, and the returning path34is formed between the motor portion M and the pump portion P so that the fluid flowing into the space13of the motor portion M from the pump portion P returns to the pump portion P. However, the configuration of the electrically operated hydraulic pump is not limited as described above and may be modified. For example, the fluid may not necessarily circulate between the motor portion and the pump portion. In addition, the electrically operated hydraulic pump may not necessarily be formed with the returning path as described above.

Due to the above described structure, the rotation control means43switches the first rotation controlling based on the rotational position of the rotor15detected by the first rotor position detecting means41and the second rotation controlling based on the rotational position of the rotor15detected by the second rotor position detecting means50, on the basis of the result detected by the motor operating condition detecting means44. In other words, the first rotation controlling, which is based on the rotational position of the rotor15detected by the first rotor position detecting means41, is implemented on the condition where the operating condition of the motor portion M based on the rotational position of the rotor15detected by the first rotor position detecting means41, is more accurate. On the other hand, the second rotation controlling, which is based on the rotational position of the rotor15detected by the second rotor position detecting means50, is implemented on the condition where the operating condition of the motor portion M based on the rotational position of the rotor15detected by the second rotor position detecting means50, is more accurate. Here, rotational speed of the rotor15, the fluid temperature, and a combination of the fluid temperature and the rotational speed of the rotor15, may be employed as the operating condition of the motor portion M, which is detected by the motor operating condition detecting means44. Accordingly, the electrically operated hydraulic pump1, which appropriately controls rotation of a motor portion M regardless of an operating condition of the motor portion M, may be provided.

According to the above described embodiment, the pump portion P, of the electrically operated hydraulic pump1, is arranged to close the opening of the motor housing10. In addition, the electrically operated hydraulic pump1further includes a fluid returning path34, which is provided between the motor portion M and the pump portion P so as to return fluid flowing into the space13of the motor portion M to the pump portion P. Further, the sensor unit52of the second rotor position detecting means50detects the magnetic field of the permanent magnet21, which is provided at the other end of the rotating shaft14in the space13of the motor portion M, from an outside of a bottom portion10aof the motor housing10.

Due to the above described structure, the fluid flows into the space13of the motor portion M from the pump portion P and returns to the pump portion P. In other words, the fluid assumes a role of cooling the motor portion M. In such condition, the fluid flowing into the space13of the motor portion M can become rotational resistance to the rotor15of the motor portion M so that the operating condition of the motor portion M is largely changed in accordance with a change of viscosity of the fluid. Accordingly, below such the condition where the operating condition of the motor portion M can be changed, it is effective that the rotation controlling means43switches the first rotation controlling based on the rotational position of the rotor15detected by the first rotor position detecting means41, and the second rotation controlling based on the rotational position of the rotor15detected by the second rotor position detecting means50, in accordance with the operating condition detected by the motor operating condition detecting means44.

Further according to the above described embodiment, the electrically operated hydraulic pump1further includes a recessed portion22, which is provided at the outside of the bottom portion10a, of the motor housing10, to be coaxial with the rotating shaft14and which has a diameter smaller than an inner diameter of the stator16. Further, the sensor unit52of the second rotor position detecting means50is arranged at the recessed portion22coaxially with the rotating shaft.

Due to the above described structure, a distance between the sensor unit52of the second rotor position detecting means50and the permanent magnet21provided at the other end of the rotating shaft14can be arranged smaller. In other wards, the sensor unit52can detect the magnetic field formed by the permanent magnet21with higher sensitivity. Accordingly, the detection precision to detect the rotational position of the rotor15may be enhanced.

Still further according to the embodiment described above, the motor operating condition detecting means44includes fluid temperature detecting means45for detecting a fluid temperature, and in such a case, the fluid temperature corresponds to the operating condition of the motor portion M. Then, the rotation controlling means43implements the first rotation controlling, which is based on the rotational position of the rotor15detected by the first rotor position detecting means41, when the fluid temperature detected by the fluid temperature detecting means45is higher than a set fluid temperature condition. On the other hand, the rotational controlling means43implements the second rotation controlling, which is based on the rotational position of the rotor15detected by the second rotor position detecting means50, when the fluid temperature detected by the fluid temperature detecting means45is lower than the set fluid temperature condition. Further, the rotation controlling means43implements at least one of the first and second rotation controllings when the fluid temperature detected by the fluid temperature detecting means45is equal to the set fluid temperature condition.

When the fluid temperature is low (i.e., when the rotational speed of the rotor15is low), the detection precision of the first rotor position detecting means41to detect the rotational position of the rotor15becomes lower. On the other hand, when the fluid temperature is high (i.e., when the rotational speed of the rotor15is high), the detection precision of the second rotor position detecting means50to detect the rotational position of the rotor15becomes lower. However, due to the above described structure and characteristic, the rotation controlling means43implements the first rotation controlling based on the result detected by the first rotor position detecting means41when the fluid temperature detected by the fluid temperature detecting means45is higher than the set temperature condition (for example, when the fluid temperature is equal to, or higher than a set temperature threshold value). On the other hand, the rotation controlling means43implements the second rotation controlling based on the result detected by the second rotor position detecting means50when the fluid temperature detected by the fluid temperature detecting means45is lower than the set temperature condition (for example, when the fluid temperature is equal to, or lower than the set temperature threshold value). Accordingly, the phenomenon described above may be solved because the rotation controlling means43switches the first rotation controlling and the second rotation controlling, in accordance with the fluid temperature detected by the fluid temperature detecting means.

Still further according to the above described embodiment, the fluid temperature detecting means45includes at least one of fluid temperature measuring means45afor measuring the fluid temperature, and fluid temperature estimating means45bfor estimating the fluid temperature.

Due to the above described structure, the fluid temperature is detected directly by the fluid temperature measuring means45a, or indirectly by the fluid temperature estimating means45b. For example, in a case where the electrically operated hydraulic pump1is mounted on a vehicle such as an automobile or the like, the fluid temperature is estimated, by the fluid temperature estimating means45b, from temperature of a radiator cooling water, or the like.

Still further according to the above described embodiment, the set fluid temperature condition includes a first fluid temperature threshold value which is employed when the fluid temperature is rising, and a second fluid temperature threshold value which is lower than the first fluid temperature threshold value and is employed when the fluid temperature is lowering.

In a condition where the set condition of the fluid temperature is defined as one set temperature threshold value, the rotation controlling means43needs to switch the first rotation controlling and the second rotational controlling every time the fluid temperature rises over and lowers below the set temperature threshold value. In other words, when the fluid temperature is at a value around the set temperature threshold value, control hunting may occur. However, due to the above described structure, the set temperature threshold value upon the fluid temperature rising and the set temperature threshold value upon the fluid temperature being lowered may be set by different values. Therefore, the control hunting described above may be prevented from being generated.

Still further according to the above described embodiment, the second rotor position detecting means50further includes a memory unit51, which memorizes a relationship between the magnetic field detected by the sensor unit52of the second rotor position detecting means50and the rotational position of the rotor15, and a calculation processing unit53, which calculates the rotational position of the rotor15on the basis of the relationship memorized in the memory unit51and the result detected by the sensor unit52.

Due to the above described structure, the memory unit51memorizes a relationship between the magnetic field detected by the sensor unit52and the rotational position of the rotor15. Accordingly, the calculation processing unit53readily and accurately calculates the rotational position of the rotor15. Therefore, the rotation controlling means43appropriately implements the second rotation controlling on the basis of the rotational position of the rotor15detected by the second rotor position detecting means50.