Electric hydraulic pump

Abstract

To solve a problem of adhesion of iron powder in hydraulic oil to a rotating shaft in an electric hydraulic pump that employs an integrated rotating shaft and a permanent-magnet motor, while maintaining strength, machinability, and cost.SOLUTION: An electric hydraulic pump includes: a pump main body portion 110 that sucks and discharges hydraulic oil using a pump rotor 112; an electric motor portion 120 including a motor rotor 123 using permanent magnets 123a; a rotating shaft 130 that integrally rotates the pump rotor 112 and the motor rotor 123 coaxially; and an oil seal 140 that seals a gap between an outer periphery of the rotating shaft 130 and a motor-side end portion of a pump case 111. The rotating shaft 130 includes: a pump-side rotating shaft 131 formed of magnetic steel material and having the pump rotating element 112 fixed thereto; and a motor-side rotating shaft 132 formed of magnetic steel material and having the motor rotor 123 fixed thereto; where the pump-side rotating shaft and the motor-side rotating shaft are coaxially coupled via a non-magnetic joint 133.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In response to the demand for smaller hydraulic pumps, a configuration has been proposed in which an electric motor and hydraulic pump are driven by a rotating shaft that integrates the pump drive shaft and the motor output shaft. Also, in response to the demand for power saving in hydraulic pumps, motors that use permanent magnets in the motor rotor have been adopted.

[0003] For example, Patent Document 1 discloses a hydraulic pump in which the drive shaft of the inner rotor of an internal gear pump is integrated with the output shaft of an electric motor. Patent Document 2 discloses a hydraulic pump in which the drive shaft of the inner rotor of an internal gear pump is integrated with the output shaft of a permanent magnet motor. Patent Document 3 discloses a hydraulic pump in which the rotating shaft of a vane pump is coaxially coupled with the output shaft of an electric motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-67214 [Patent Document 2] Patent Publication No. 2013-169136 [Patent Document 3] Patent Publication No. 2019-206919 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a motor with a permanent magnet is used as the electric motor and the pump drive shaft and motor output shaft are integrated, the surface of the rotating shaft can be slightly magnetized by the magnetic force of the magnet, and a weak magnetic force can be generated at the contact point of the rotating shaft with the hydraulic oil. Meanwhile, the hydraulic oil passing through the hydraulic pump may contain fine iron powder, and iron powder generated during the initial operation of the hydraulic pump may become mixed into the hydraulic oil. Such iron powder can adhere to the rotating shaft due to magnetic force, become trapped, and form clumps that can become lodged in the sliding parts, causing wear on the sliding parts.

[0006] As a solution to the problem of magnetization of the rotating shaft, Patent Document 2 proposes making the rotating shaft out of a non-magnetic metal. However, making the entire rotating shaft out of a non-magnetic metal, such as aluminum or stainless steel, poses problems in terms of strength, workability, and cost. Another problem is that it is not always possible to utilize the know-how of processing conventional magnetic steel materials.

[0007] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an electric hydraulic pump that employs a coaxially coupled rotating shaft and permanent magnet motor, which is excellent in strength, workability, and cost, and can solve the problem of iron powder in hydraulic oil adhering to the rotating shaft. [Means for solving the problem]

[0008] (1) In order to solve the above-mentioned problems, an electric hydraulic pump of the present invention comprises: a pump main body having a pump case and sucking in and discharging hydraulic oil using a pump rotating element; an electric motor including a motor case connected to the pump case and a motor rotor using a permanent magnet; a rotating shaft having one end to which the pump rotating element is fixed and the other end to which the motor rotor is fixed, coaxially rotating the pump rotating element and the motor rotor integrally; and an oil seal that seals a gap between the outer periphery of the rotating shaft and the inner periphery of the pump case at an end of the other end of the pump case, wherein the rotating shaft is a pump-side rotating shaft made of magnetic steel and to which the pump rotating element is fixed, and a motor-side rotating shaft made of magnetic steel and to which the motor rotor is fixed, and are coaxially connected to both sides of a joint made of a non-magnetic member whose base material is metal, ceramics, or hard resin. (2) A pump body having a pump case and sucking in and discharging hydraulic oil using pump rotating elements; an electric motor including a motor case connected to the pump case and a motor rotor using a permanent magnet; a rotating shaft having the pump rotating elements fixed to one end and the motor rotor fixed to the other end, coaxially rotating the pump rotating elements and the motor rotor; and an oil seal at the end of the other end of the pump case, sealing a gap between the outer periphery of the rotating shaft and the inner periphery of the pump case, wherein the rotating shaft is made of magnetic steel and has the pump rotating elements fixed thereto, and a motor side rotating shaft made of magnetic steel and has the motor rotor fixed thereto, which are coaxially connected via a joint made of a non-magnetic member, and a nitride layer of the base material constituting the joint is formed on the surface of the joint, and the nitride layer is non-magnetic. (3) The non-magnetic member may be made of aluminum or non-magnetic stainless steel (SUS303, 304, etc.). (4) A gap between the end of the pump-side rotating shaft and the end of the motor-side rotating shaft that face each other via the joint may be 10% or more of the shaft diameter of the end of the motor-side rotating shaft. (5) The joint may be a substantially short-shaft member having a first tip end portion with a predetermined cross-section at one end and a second tip end portion with a predetermined cross-section at the other end, the pump-side rotating shaft having a first fitting hole drilled from the end face at the other end along the central axis and having a cross-section shaped to fit into the first tip end portion to transmit axial rotation, the motor-side rotating shaft having a second fitting hole drilled from the end face at the one end along the central axis and having a cross-section shaped to fit into the second tip end portion to transmit axial rotation, and the rotating shaft may be formed by fitting the first tip end into the first fitting hole and the second tip end into the second fitting hole. (7) The pump side rotating shaft may have both sides protruding from the pump rotating element and be rotatably supported by the pump case via a first bearing provided on the one end side of the pump rotating element and a second bearing provided on the other end side of the pump rotating element, and the first bearing and the second bearing are provided on the one end side of the oil seal. The pump side rotating shaft may have both sides protruding from the pump rotating element and be rotatably supported by the pump case via a first bearing provided on the one end side of the pump rotating element and a second bearing provided on the other end side of the pump rotating element, and the second bearing may be arranged on the outer circumferential side of the pump side rotating shaft at a portion where the first tip end is fitted into the first fitting hole. (6) The pump side rotating shaft may have both sides protruding from the pump rotating element and be rotatably supported by the pump case via a first bearing provided on the one end side of the pump rotating element and a second bearing provided on the other end side of the pump rotating element, and the second bearing may be arranged on the outer circumferential side of the pump side rotating shaft at the portion where the first tip end portion is fitted into the first fitting hole. The pump may be a variable displacement vane pump, but the electric hydraulic pump of the present invention is not limited to variable displacement vane pumps and can be applied to any pump that uses a pump rotating element to suck in and discharge hydraulic oil, such as a fixed displacement vane pump, a variable displacement / fixed displacement piston pump, or a variable displacement / fixed displacement gear pump. [Effects of the Invention]

[0009] According to the electric hydraulic pump of the present invention, the rotating shaft is formed by coaxially connecting a pump-side rotating shaft made of magnetic steel to which the pump rotating element is fixed, and a motor-side rotating shaft made of magnetic steel to which the motor rotor is fixed, via a joint made of a non-magnetic material. This configuration allows the use of a rotating shaft made of steel, which is excellent in strength, workability, and cost, while the joint made of a non-magnetic material can block magnetization from the motor-side rotating shaft due to the magnetic field from a permanent magnet. As a result, magnetization of the pump-side rotating shaft can be suppressed, thereby reducing adhesion of iron powder to the rotating shaft. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a vertical cross-sectional view showing an electric hydraulic pump according to a first embodiment. [Figure 2] 2 is a cross-sectional view of the electric hydraulic pump shown in FIG. 1 along the line AA. [Figure 3] 2A to 2C are enlarged partial views showing a joint portion of the electric hydraulic pump of FIG. 1, in which (a) is a longitudinal cross-sectional view, (b) is a BB cross-sectional view, and (c) is a CC cross-sectional view. [Figure 4] FIG. 5 is a vertical cross-sectional view showing an electric hydraulic pump according to a second embodiment. [Figure 5] 5A, 5B, and 5C are enlarged partial views showing a joint portion of the electric hydraulic pump of FIG. 4, in which (a) is a longitudinal cross-sectional view, (b) is a DD cross-sectional view, and (c) is an EE cross-sectional view. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. (First embodiment) FIG. 1 is a longitudinal cross-sectional view showing an electric hydraulic pump 100 according to a first embodiment, and FIG. 2 is a cross-sectional view taken along line AA thereof. In the electric hydraulic pump 100 of this embodiment, a pump-side rotating shaft 131 and a motor-side rotating shaft 132 are coaxially coupled to each other on either side of a joint 133 made of non-magnetic austenitic stainless steel (e.g., SUS303 or 304), to form a rotating shaft 130. In other words, the pump-side rotating shaft 131 and the motor-side rotating shaft 132 are mechanically joined to each other through the joint 133, and the rotational force between the pump-side rotating shaft 131 and the motor-side rotating shaft 132 is transmitted through the joint 133. The material of the joint 133 may be any rigid non-magnetic material, excluding flexible materials such as rubber. Examples of suitable materials for the joint 133 include non-magnetic metals (e.g., aluminum and SUS), non-magnetic ceramics, and non-magnetic hard resins.

[0012] The electric hydraulic pump 100 of this embodiment includes a pump main body 110, an electric motor 120, a rotary shaft 130, and an oil seal 140.

[0013] The pump main body 110 has a pump case 111 and is a device that draws in and discharges hydraulic oil using a pump rotor 112, which is a pump rotating element, and in this embodiment constitutes a variable displacement vane pump.

[0014] The pump case 111 is configured by joining a pump case body 111a and a pump lid 111b, and forms the outer shell of the pump body 110. An internal space 111c of the pump case 111 accommodates a pump rotor 112, a cam ring 113, and a pump-side rotating shaft 131, which will be described later.

[0015] As shown in Figure 2, the pump rotor 112 is a substantially disk-shaped member. The pump rotor 112 is fixed to a pump-side rotating shaft 131 that passes through a central shaft hole 112a, and rotates integrally with the pump-side rotating shaft 131. A plurality of slits 112b are formed radially on the outer circumferential surface of the pump rotor 112 and are arranged at equal intervals in the circumferential direction. A vane 114 is housed in each slit 112b so that it can move forward and backward in the radial direction.

[0016] The cam ring 113 is a substantially annular member that is disposed in the internal space 111c of the pump case 111 so as to surround the pump rotor 112. Both axial ends of the cam ring 113 and the pump rotor 112 are sealed by side plates 115, 116 (see FIG. 1) that are fixed to the internal space 111c. Therefore, when the pump rotor 112 rotates, the vanes 114 come into contact with the inner circumferential surface of the cam ring 113 due to centrifugal force, and multiple compression chambers 117 are formed that are partitioned by pairs of adjacent vanes 114, 114, the pump rotor 112, the cam ring 113, and the side plates 115, 116.

[0017] Here, cam ring 113 is positioned eccentrically relative to pump rotor 112 and pump-side rotating shaft 131, so the distance between the outer periphery of pump rotor 112 and the inner periphery of cam ring 113 varies depending on the circumferential position. Therefore, when pump rotor 112 rotates, the volume of each compression chamber 117 expands over half its circumference and contracts over half its circumference. Side plate 115 is provided with intake ports 115a (see FIG. 1) at positions where the volumes of compression chambers 117 expand, through which hydraulic oil is drawn into compression chambers 117 from the outside. Furthermore, side plate 115 is provided with discharge ports 115b (see FIG. 1) at positions where the volumes of compression chambers 117 contract, through which hydraulic oil compressed in compression chambers 117 is discharged to the outside. The amount of eccentricity of cam ring 113 within internal space 111c is adjusted by maximum discharge rate adjustment screw 118, and the constraint force of the eccentricity is adjusted by pressure adjustment screw 119.

[0018] As shown in FIG. 1, a through-hole 111d through which the rotating shaft 130 passes is provided in the wall of the other end (the end on the electric motor unit 120 side) of the pump case body 111a, and a blind hole 111e for accommodating one end of the pump-side rotating shaft 131 is provided in the center of the pump lid 111b on the inner space 111c side. A bush-shaped plain bearing 141 made of a soft metal, which serves as a first bearing, is provided on the inner periphery of the blind hole 111e. Meanwhile, a plain bearing 142, which serves as a second bearing, is provided on the inner periphery of the through-hole 111d. These bearings rotatably support the pump-side rotating shaft 131. A ball bearing 143 for supporting the motor-side rotating shaft 132, which will be described later, is provided on the other end side (the electric motor unit 120 side) of the plain bearing 142 of the through-hole 111d.

[0019] 1, the electric motor unit 120 includes a motor case 121 coupled to the pump case 111, and a motor rotor 123 using permanent magnets 123a. In this embodiment, an IPM motor is configured in which the permanent magnets 123a are embedded in the motor rotor 123.

[0020] The motor case 121 is configured by joining a motor case main body 121a and a motor lid 121b, and forms the outer shell of the electric motor unit 120. An internal space 121c of the motor case 121 accommodates a stator 122, a motor rotor 123, and a motor-side rotating shaft 132 (described later). The motor case main body 121a is a substantially cylindrical member with both ends open. The other end of the motor case main body 121a (the side opposite the pump main body 110) is sealed with the motor lid 121b, and one end (the side facing the pump main body 110) is joined to the pump case main body 111a. As a result, the motor case 121 and the pump case 111 form an integrated casing. A bearing holder 121d is provided in the motor lid 121b at the center thereof, facing the internal space 121c. A ball bearing 144 for supporting the other end side (the side opposite to the pump main body 110) of the motor side rotating shaft 132 is fitted into the bearing holder 121d.

[0021] The stator 122 is held on the inner periphery of the motor case main body 121a. The stator 122 has comb-like teeth provided on the inner periphery of a stator core (not shown) that is circular when viewed in the axial direction, and windings (not shown) are wound around each of these teeth. The stator 122 generates a rotating magnetic field. The motor rotor 123 is a substantially disk-shaped or cylindrical member that is arranged on the inner periphery of the stator 122 with a predetermined air gap between them. Permanent magnets 123a are embedded inside the motor rotor 123 near the outer periphery at regular intervals in the circumferential direction. The motor rotor 123 is fixed to a motor-side rotating shaft 132 that passes through a central shaft hole 123b, and is capable of rotating integrally with the motor-side rotating shaft 132.

[0022] The rotating shaft 130 is a member that coaxially and integrally rotates the pump rotor (pump rotating element) 112 and the motor rotor 123. The pump rotor 112 is fixed to one end of the rotating shaft 130, and the motor rotor 123 is fixed to the other end. In this embodiment, as shown in an enlarged view in FIG. 3, the rotating shaft 130 is formed by coaxially connecting a pump-side rotating shaft 131 and a motor-side rotating shaft 132 via a joint 133.

[0023] The pump-side rotating shaft 131 is made of magnetic steel (e.g., SCM material). The pump-side rotating shaft 131 is inserted into and fitted into a shaft hole 112a of the pump rotor 112 (see FIG. 1) and is configured to rotate integrally with the pump rotor 112. The pump-side rotating shaft 131 has a first fitting hole 131a at its other end (electric motor side). The first fitting hole 131a has an involute spline shape in cross section and is drilled along the central axis from the end face of the pump-side rotating shaft 131 at its other end (electric motor side). The first fitting hole 131a is configured to fit into a first tip end portion 133a of a joint 133 (described later) to transmit axial rotation. As shown in FIG. 1, the pump-side rotating shaft 131 has protruding portions that protrude from one end and the other end (left and right directions in FIG. 1) from the pump rotor 112. The protruding portion on one end is rotatably supported by a plain bearing 141 held by the pump lid 111b. The protruding portion on the other end is rotatably supported by a plain bearing 142 provided in a through hole 111d of the pump case body 111a. The plain bearing 142 is disposed on the outer periphery of the pump-side rotating shaft 131, at the fitting portion between the first tip end 133a of the joint 133 and the first fitting hole 131a. This configuration reduces axial wobble of the pump-side rotating shaft 131 at the joint between the pump-side rotating shaft 131 and the joint 133, thereby reducing vibration during rotation.

[0024] The motor-side rotating shaft 132 is made of magnetic steel (e.g., SC material). The motor-side rotating shaft 132 is inserted into and fitted into a shaft hole 123b of the motor rotor 123, and is configured to rotate integrally with the motor rotor 123. The motor-side rotating shaft 132 has a second fitting hole 132a at one end (the pump body side). As shown enlarged in FIG. 3, the second fitting hole 132a has a circular cross section with two chamfered sides, and is drilled along the central axis from the end face of the motor-side rotating shaft 132 at one end (the pump body side). The second fitting hole 132a is configured to fit into a second tip end 133b of a joint 133 (described later) to transmit axial rotation. As shown in FIG. 1, the motor-side rotating shaft 132 protrudes from the motor rotor 123 at one end and the other end (in the left-right direction in FIG. 1). The protruding portion on one end side is rotatably supported by a ball bearing 143 provided in a through hole 111d of the pump case main body 111a. The protruding portion on the other end side is rotatably supported by a ball bearing 144 provided in the motor case 121. The tip portion of one end side (pump main body side) of the motor side rotating shaft 132 protrudes from the ball bearing 143, and an oil seal 140 is in sliding contact with the outer periphery thereof.

[0025] In this embodiment, the joint 133 is a substantially short-shaft-shaped member made of non-magnetic steel (austenitic stainless steel SUS303, SUS304, etc.). As shown in FIG. 3 , the joint 133 has a first tip portion 133a with an involute spline cross section at one end (pump body side) and a second tip portion 133b with a circular cross section with two chamfered sides at the other end (electric motor side). In this embodiment, the first tip portion 133a of the joint 133 is fitted into a first fitting hole 131a of the pump-side rotating shaft 131, and the second tip portion 133b of the joint 133 is fitted into a second fitting hole 132a of the motor-side rotating shaft 132. With this configuration, the pump-side rotating shaft 131 and the motor-side rotating shaft 132 are connected via the joint 133 to form the rotating shaft 130 of this embodiment. This configuration allows the rotating element side rotating shaft and the motor rotor side rotating shaft to be coaxially coupled via the joint with a simple structure.

[0026] In the rotating shaft 130 formed in this manner, the gap g between the end of the pump-side rotating shaft 131 and the end of the motor-side rotating shaft 132, which face each other via the joint 133 shown in Figure 3(a), is set to be 10% or more of the shaft diameter d of the end of the motor-side rotating shaft 132. With this configuration, a sufficient magnetization shielding effect can be obtained between the motor-side rotating shaft 132 and the pump-side rotating shaft 131.

[0027] As shown in FIG. 1, the oil seal 140 seals the gap between the outer periphery of the rotating shaft 130 and the inner periphery of the pump case 111 at the other end (electric motor unit 120 side) of the pump case 111. The oil seal 140 thereby prevents hydraulic oil from the pump main body 110 side from entering the electric motor unit 120 side. In this embodiment, the oil seal 140 is made of rubber and formed into an annular shape with a generally U-shaped cross section. The oil seal 140 is fitted into the inner periphery of the through hole 111d of the pump case main body 111a. The inner periphery of the oil seal 140 is in sliding contact with the outer periphery of the tip of one end (pump main body side) of the motor-side rotating shaft 132.

[0028] Next, the operation of the electric hydraulic pump 100 of this embodiment configured as described above will be described with reference to Figures 1 and 2. This operation is basically the same as that of a conventional variable displacement vane pump. That is, when the electric motor unit 120 is started, a rotating magnetic field is generated by the stator 122, and the motor rotor 123 rotates in accordance with the rotation of this magnetic field. At this time, the pump rotor 112, which is connected to the motor rotor 123 via the rotating shaft 130, also rotates.

[0029] As explained above about the pump portion, when the pump rotor 112 rotates, the volume of each compression chamber 117 expands over half its circumference and contracts over half its circumference. At the position where the volume of the compression chamber 117 expands, hydraulic oil is drawn into the compression chamber 117 from the outside through the intake port 115a (see FIG. 1) of the side plate 115. On the other hand, at the position where the volume of the compression chamber 117 contracts, the hydraulic oil compressed in the compression chamber 117 is discharged to the outside through the discharge port 115b (see FIG. 1) of the side plate 115. This allows the hydraulic oil to be pumped out.

[0030] A portion of this hydraulic oil spreads throughout the pump main body 110 shown in FIG. 1 and lubricates the plain bearings 141 and 142. This hydraulic oil also comes into contact with the rotating shaft 130 (i.e., the joint 133 and the pump-side rotating shaft 131) on the one end side (pump main body side) of the oil seal 140, which has traditionally resulted in a problem of iron powder in the hydraulic oil adhering to the rotating shaft 130. This problem is particularly likely to occur when using a motor rotor 123 equipped with a permanent magnet 123a, as the rotating shaft 130 may be magnetized by the magnetic field of the permanent magnet 123a. In the electric hydraulic pump 100 of this embodiment, the joint 133 is made of nonmagnetic steel, so magnetization from the motor-side rotating shaft 132 due to the magnetic field from the permanent magnet 123a is blocked by this joint 133. As a result, the surfaces of the joint 133 and the pump-side rotating shaft 131, which constitute the one end side (pump main body side) of the oil seal 140, are less likely to be magnetized. This reduces the amount of iron powder that adheres to these parts of the rotary shaft 130 that come into contact with the hydraulic oil. In addition, iron powder is less likely to adhere to the pump-side rotating shaft, reducing damage to these bearings.

[0031] According to the configuration of the above embodiment, a rotating shaft made of steel, which is excellent in strength, workability, and cost, can be used, while a joint made of a non-magnetic material can block magnetization of the motor-side rotating shaft due to the magnetic field from the permanent magnet. As a result, magnetization of the pump-side rotating shaft can be suppressed, thereby reducing iron powder adhesion to the rotating shaft. Furthermore, adhesion of iron powder to the rotating shaft of a variable displacement vane pump can be reduced, thereby extending the pump's lifespan.

[0032] (Second embodiment) FIG. 4 is a longitudinal cross-sectional view of an electric hydraulic pump according to a second embodiment of the present invention, and FIG. 5 is a partially enlarged view of a joint portion thereof. An electric hydraulic pump 200 according to this embodiment is similar to the electric hydraulic pump 100 according to the first embodiment, except that the joint 133 has a non-magnetic plating layer formed on its surface. In this embodiment, a hard chrome plating layer 233c is provided as this non-magnetic plating layer to improve the wear resistance of the joint 233. However, the non-magnetic plating layer is not limited to the chrome plating layer 233c, and may be, for example, a high-P to medium-P nickel plating layer. Alternatively, a nitride layer may be formed by nitriding the surface of the joint 233. For example, a nitride layer of the base material (e.g., a non-magnetic metal) constituting the joint 233 may be formed on the surface of the joint 233. The formed nitride layer is also non-magnetic. Other than that, the configuration of the electric hydraulic pump 200 is the same as that of the electric hydraulic pump 100 of the first embodiment, so the same components are given the same reference numerals and detailed description thereof will be omitted.

[0033] As shown in Fig. 5, the shape of joint 233 is the same as that of joint 133 of the first embodiment shown in Fig. 3. As in the first embodiment, rotating shaft 230 of this embodiment is formed by connecting pump-side rotating shaft 131 and motor-side rotating shaft 132 via joint 233. As in the first embodiment, oil seal 140 is disposed at the very tip of one end (pump body side) of motor-side rotating shaft 132. Therefore, joint 233 and pump-side rotating shaft 131 correspond to the one end side (pump body side) of oil seal 140.

[0034] The operation of the electric hydraulic pump 200 of this embodiment is basically the same as that of the electric hydraulic pump 100 of the first embodiment. In this embodiment, too, magnetization from the motor-side rotating shaft 132 side due to the magnetic field from the permanent magnet 123a (see FIG. 4) is blocked by the joint 233. In addition, the chrome plating layer 233c applied to the joint 233 is also non-magnetic and has a magnetization blocking effect, making the surface of the pump-side rotating shaft 131 less likely to be magnetized. This makes it possible to reduce iron powder adhering to those parts of the rotating shaft 230 that come into contact with hydraulic oil. In addition to the above effects, the chrome plating layer 233c also has the effects of increasing the surface hardness of the joint 233 to improve wear resistance and increasing oil film retention to improve lubrication characteristics.

[0035] Although the embodiment of the present invention has been described above, various design modifications can be made to the present invention without departing from the gist of the invention.

[0036] For example, in the first and second embodiments, a variable displacement vane pump is described as an example of the pump. However, the present invention is not limited to this, and the pump may be any pump that uses a pump rotating element. For example, a fixed displacement vane pump, a variable displacement or fixed piston pump, a variable displacement or fixed gear pump, etc. may be used.

[0037] In the first and second embodiments, an IPM motor is described as an example of the motor, but the present invention is not limited to this, and the motor may be any motor that uses a permanent magnet, such as an SPM motor.

[0038] In the first and second embodiments, the joints 133 and 233 are configured such that the tip ends of the joints on each side fit into the fitting holes of the respective shafts, but the present invention is not limited to this. For example, the tip ends of the shafts may fit into the fitting holes on each side of the joint, or the tip end of one shaft may fit into the fitting hole on one side of the joint, and the tip end of the other side of the joint may fit into the fitting hole of the other shaft. [Explanation of symbols]

[0039] 100, 200 Electric hydraulic pump 110 Pump body 111 Pump case 111a Pump case body 111b Pump cover 111c interior space 111d Through hole 111e blind hole 112 Pump rotor 112a Shaft hole 112b Slit 113 Cam Ring 114 Vane 115 Side Plate 115a Inlet 115b Discharge port 116 Side Plate 117 Compression Chamber 118 Maximum discharge volume adjustment screw 119 Pressure adjustment screw 120 Electric motor section 121 Motor case 121a Motor case body 121b Motor cover 121c interior space 121d Bearing holder 122 Stator 123 Motor rotor 123a Permanent magnet 123b Shaft hole 130, 230 rotation axis 131 Pump side rotating shaft 131a First fitting hole 132 Motor side rotating shaft 132a Second fitting hole 133, 233 joints 133a First tip 133b Second tip 140 Oil seal 141, 142 Plain bearings 143, 144 Ball bearings 233c Chrome plating layer

Claims

1. a pump main body having a pump case and configured to suck in and discharge hydraulic oil using a pump rotating element; an electric motor section including a motor case coupled to the pump case and a motor rotor using a permanent magnet; a rotating shaft having one end side to which the pump rotating element is fixed and the other end side to which the motor rotor is fixed, so that the pump rotating element and the motor rotor are coaxially rotated integrally; an oil seal that seals a gap between an outer periphery of the rotary shaft and an inner periphery of the pump case at an end portion on the other end side of the pump case, an electric hydraulic pump, characterized in that the rotating shaft comprises a pump-side rotating shaft made of magnetic steel and having the pump rotating element fixed thereto, and a motor-side rotating shaft made of magnetic steel and having the motor rotor fixed thereto, the rotating shafts being coaxially coupled to each other on either side of a joint made of a non-magnetic member whose base material is metal, ceramic, or hard resin.

2. a pump main body having a pump case and configured to suck in and discharge hydraulic oil using a pump rotating element; an electric motor section including a motor case coupled to the pump case and a motor rotor using a permanent magnet; a rotating shaft having one end side to which the pump rotating element is fixed and the other end side to which the motor rotor is fixed, so that the pump rotating element and the motor rotor are coaxially rotated integrally; an oil seal that seals a gap between an outer periphery of the rotary shaft and an inner periphery of the pump case at an end portion on the other end side of the pump case, the rotating shaft is a pump-side rotating shaft made of magnetic steel and having the pump rotating element fixed thereto, and a motor-side rotating shaft made of magnetic steel and having the motor rotor fixed thereto, which are coaxially connected via a joint made of a non-magnetic member; An electric hydraulic pump, characterized in that a nitride layer of a base material constituting the joint is formed on a surface layer of the joint, and the nitride layer is a non-magnetic material.

3. 3. The electric hydraulic pump according to claim 1, wherein the non-magnetic member is a non-magnetic stainless steel or aluminum member.

4. 3. The electric hydraulic pump according to claim 1, wherein a gap between the end of the pump-side rotating shaft and the end of the motor-side rotating shaft that face each other via the joint is 10% or more of a shaft diameter of the end of the motor-side rotating shaft.

5. the joint is a substantially short-shaft-shaped member, and has a first tip portion having a predetermined cross-sectional shape at the one end side, and a second tip portion having a predetermined cross-sectional shape at the other end side, the pump-side rotating shaft has a first fitting hole drilled from the end face on the other end side along a central axis and having a cross section shaped to fit into the first tip portion and transmit axial rotation; the motor-side rotating shaft has a second fitting hole drilled along a central axis from an end face on the one end side, the second fitting hole having a cross section shaped to fit into the second tip portion and transmit axial rotation; the rotating shaft is formed by fitting the first tip end portion into the first fitting hole and the second tip end portion into the second fitting hole, the pump-side rotating shaft has both ends protruding from the pump rotating element, and is rotatably supported by the pump case via a first bearing provided on the one end side of the pump rotating element and a second bearing provided on the other end side of the pump rotating element; 3. The electric hydraulic pump according to claim 1, wherein the second bearing is disposed on an outer circumferential side of the pump-side rotating shaft at a portion where the first tip end portion is fitted into the first fitting hole.

6. the pump-side rotating shaft has both ends protruding from the pump rotating element, and is rotatably supported by the pump case via a first bearing provided on the one end side of the pump rotating element and a second bearing provided on the other end side of the pump rotating element; 3. The electric hydraulic pump according to claim 1, wherein the first bearing and the second bearing are provided closer to the one end than the oil seal.

Images