Rotary electric machine system

A rotary electric machine system includes: a rotary electric machine; a lubrication mechanism configured to supply lubricating oil to a bearing of the rotary electric machine; and a control unit configured to control the supply of lubricating oil from the lubrication mechanism. The control unit is configured to acquire an operation status of the rotary electric machine and determine whether there is a possibility of occurrence of electrolytic corrosion in the bearing. The control unit is configured to, when it is determined that there is a possibility of occurrence of electrolytic corrosion, increase the supply of lubricating oil to the bearing by controlling the lubrication mechanism as compared to the supply of lubricating oil to the bearing at a time when it is not determined that there is a possibility of occurrence of electrolytic corrosion.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-191987 filed on Sep. 29, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a rotary electric machine system that prevents occurrence of electrolytic corrosion in a bearing of a rotary electric machine.

2. Description of Related Art

A rotary electric machine that is driven by using electric power is mounted on various devices and used. In a rotary electric machine of this type, induced electromotive force can be generated at a rotor side due to fluctuations in magnetic field resulting from supply of electric power to a stator side, with the result that a potential difference can occur between a rotor shaft and a peripheral member of the rotor shaft. For this reason, if an electrical closed circuit that passes from a rotor core to the rotor shaft is formed, including a bearing that has the rotor shaft rotatably supported on the peripheral member, there is a concern about occurrence of electrolytic corrosion, such as surface roughness, caused by, for example, a spark that is developed on the bearing.

For example, Japanese Patent Application Publication No. 2015-159647 (JP 2015-159647 A) describes the following configuration. An electrical insulating film is provided between a rotor shaft and a rotor core in a rotary electric machine mounted on a vehicle. This interrupts leakage current and, as a result, restricts formation of a closed circuit, and also reduces occurrence of electrolytic corrosion in a bearing.

SUMMARY

However, in the rotary electric machine described in JP 2015-159647 A, it is possible to restrict formation of the closed circuit that passes through the rotor core but it is not possible to restrict formation of a closed circuit in which the bearing is interposed between the rotor shaft and another peripheral member without passing through the rotor core. As a result, there has been a possibility of occurrence of electrolytic corrosion in the bearing.

The disclosure provides a rotary electric machine system that is able to simply ensure the electrical insulating property of a bearing for a rotor shaft of a rotary electric machine.

An aspect of the disclosure provides a rotary electric machine system. The rotary electric machine system includes: a rotary electric machine including a stator and a rotor, a rotor shaft fixed to the rotor being rotatably supported by a case via a bearing; a lubrication mechanism configured to supply lubricating oil to the bearing of the rotary electric machine; and a control unit configured to control the supply of lubricating oil from the lubrication mechanism. The control unit is configured to acquire an operation status of the rotary electric machine and determine whether there is a possibility of occurrence of electrolytic corrosion in the bearing. The control unit is configured to, when it is determined that there is a possibility of occurrence of electrolytic corrosion, increase the supply of lubricating oil to the bearing by controlling the lubrication mechanism as compared to the supply of lubricating oil to the bearing at a time when it is not determined that there is a possibility of occurrence of electrolytic corrosion.

According to the above aspect of the disclosure, at the timing at which it is determined that the rotary electric machine system is placed in an operation state where there is a possibility of occurrence of electrolytic corrosion in the bearing, the supply of lubricating oil to the bearing is increased, and the amount of lubricating oil on the bearing surface is increased. For this reason, the supply of lubricating oil is not unnecessarily increased, and the amount of lubricating oil between the bearing surfaces of the bearing is increased at necessary timing, so the electrical insulating property provided by the lubricating oil is increased.

Therefore, it is possible to provide the rotary electric machine system that is able to ensure the electrical insulating property at the bearing with high reliability with the use of simple control for just increasing the supply of lubricating oil to the bearing as needed.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.FIG. 1toFIG. 6Dare views that illustrate a rotary electric machine system according to a first embodiment of the disclosure.FIG. 1is a view that shows an example of a vehicle on which the rotary electric machine system is mounted.

First Embodiment

As shown inFIG. 1, the vehicle100is a so-called hybrid vehicle on which an internal combustion-type engine101and rotary electric machines111,112are mounted as power sources. Each of the rotary electric machines111,112functions as a motor generator (MG). That is, the vehicle100includes the rotary electric machine system according to the present embodiment. The vehicle100is configured such that the overall vehicle is controlled by an electronic control unit (ECU)1and, for example, these engine101and rotary electric machines111,112are efficiently driven. The power of these engine101and rotary electric machines111,112is transmitted to drive shafts151via a power transmission mechanism121, and the like. The power transmission mechanism121has the function of a differential device. Thus, wheels (not shown) are rotated, and the vehicle100travels.

The engine101converts the combustion energy of fuel to rotational driving force and outputs the rotational driving force as power. Each of the rotary electric machines111,112is rotationally driven and outputs power when supplied with alternating-current power converted by an inverter from direct-current power energy stored in a battery (not shown). Each of the rotary electric machines111,112is configured to be able to operate as an electric motor that is driven when supplied with electric power from the battery and also operate as a generator that generates and outputs regenerative electric power for charging the battery during deceleration, or the like.

Each of the rotary electric machines111,112includes a rotor115and a stator116. The rotor115has a rotor core115c.The stator116has a stator core116con which a stator coil116wis wound. The rotor115is rotatably accommodated inside the stator116. In the rotary electric machine111, the rotor core115cis fixed to the rotor shaft111aso as to rotate integrally with the rotor shaft111a.In the rotary electric machine112, the rotor core115cis fixed to the rotor shaft112aso as to rotate integrally with the rotor shaft112a.

The power transmission mechanism121includes a single pinion-type planetary gear122. The planetary gear122includes a sun gear126, a ring gear127, a carrier128and pinion gears129. The sun gear126, the ring gear127, the carrier128and the pinion gears129differentially rotate. The power transmission mechanism121includes an input shaft121ahaving the same rotation axis as an output shaft101aof the engine101. In the power transmission mechanism121, the carrier128is coaxially coupled to the input shaft121aso as to rotate integrally with the input shaft121a,and the sun gear126is coaxially coupled to the rotor shaft111aof the rotary electric machine (MG1)111so as to rotate integrally with the rotor shaft111a.In the power transmission mechanism121, the carrier128supports the plurality of pinion gears129such that the pinion gears129are rotatable, and the ring gear127accommodates these pinion gears129on the radially inner side and is in mesh with these pinion gears129. Each of the pinion gears129rotates or revolves around the sun gear126to epicyclically rotate. Thus, in the power transmission mechanism121, the ring gear127is assembled to the concentric sun gear126via the pinion gears129so as to coaxially rotate with the sun gear126.

A one-way brake139is installed between the output shaft101aof the engine101and the input shaft121aof the power transmission mechanism121. The one-way brake139is fixed to a housing111H. The one-way brake139is configured to stop the rotation of the carrier128of the power transmission mechanism121by fixedly engaging with the output shaft101aso as to restrict rotation in a direction opposite to the rotational direction of the engine101.

In the power transmission mechanism121, an external gear train, and the like, are coupled to a drive gear131such that power is transmitted. The drive gear131is an external gear. The drive gear131is formed at the outer peripheral side of the ring gear127, and integrally rotates with the ring gear127. A counter shaft132is rotatably installed parallel to the input shaft121aof the power transmission mechanism121. A counter driven gear133is fixed to one end of the counter shaft132so as to rotate integrally with the counter shaft132. The counter driven gear133is in mesh with the drive gear131provided at the outer peripheral side of the ring gear127. A counter drive gear136is fixed to the other end of the counter shaft132so as to rotate integrally with the counter shaft132. A reduction gear137is in mesh with the counter driven gear133provided at one end of the counter shaft132. The reduction gear137is fixed to an end of the rotor shaft112aof the rotary electric machine (MG2)112. A ring gear145of a differential gear141is in mesh with the counter drive gear136provided at the other end of the counter shaft132. Thus, the counter drive gear136is coupled to the drive shafts151.

With this structure, the vehicle100is able to cause the rotational power of the engine101, rotary electric machine111or rotary electric machine112to be output from the corresponding output shaft101a,rotor shaft111aor rotor shaft112a.The rotational power to be output is able to cause the wheels (not shown) to roll when transmitted to the drive shafts151via the power transmission mechanism121, thus making it possible to cause the vehicle100to travel.

The vehicle100includes a mechanical oil pump (hereinafter, also simply referred to as MOP)11and an electric oil pump (hereinafter, also simply referred to as EOP)21in order to supply lubricating oil to lubricated portions that require cooling or lubrication in the rotary electric machines111,112, the power transmission mechanism121, and the like.

The MOP11is installed so as to be directly coupled to the output shaft101aof the engine101and driven by the engine101. The MOP11is operated simultaneously with startup of the engine101, and starts supplying lubricating oil to the rotary electric machines111,112, and the like.

The EOP21is installed so as to be operable independently of the engine101. A pump portion (not shown) of the EOP21is driven to operate by a motor22, and starts supplying lubricating oil to the rotary electric machines111,112, and the like. The motor22is driven when supplied with electric power stored in a battery (not shown). That is, the MOP11is not operable during a stop of the engine101, but the EOP21is able to operate and supply lubricating oil to the rotary electric machines111,112, and the like, even during a stop of the engine101.

These MOP11and EOP21are incorporated in a hydraulic circuit161shown inFIG. 2, and each are configured so as to supply lubricating oil to the lubricated portions of the rotary electric machines111,112, and the like. The hydraulic circuit161includes a suction oil passage162, a first distributing oil passage163, a second distributing oil passage164, a first supply oil passage165and a second supply oil passage166.

The suction oil passage162is connected to a reservoir111Hp via a strainer171. The reservoir111Hp is installed at the bottom inside the housing111H, and stores lubricating oil. Branch passages162a,162bthat branch off from the strainer171are respectively connected to a suction port11iof the MOP11and a suction port21iof the EOP21. Thus, the MOP11and the EOP21each are able to draw and discharge lubricating oil strained by the strainer171.

The first distributing oil passage163is connected to a discharge port11oof the MOP11. The first supply oil passage165and the second supply oil passage166are connected to the first distributing oil passage163so as to branch off from the first distributing oil passage163. Similarly, the second distributing oil passage164is connected to a discharge port21oof the EOP21. The first supply oil passage165and the second supply oil passage166are connected to the second distributing oil passage164so as to branch off from the second distributing oil passage164. That is, the first supply oil passage165and the second supply oil passage166communicate with each of the first distributing oil passage163and the second distributing oil passage164at the corresponding connecting portion, and are connected to each of the first distributing oil passage163and the second distributing oil passage164in parallel with each other. Thus, the MOP11is able to feed lubricating oil under pressure to the first supply oil passage165and the second supply oil passage166via the first distributing oil passage163, and the EOP21is able to feed lubricating oil under pressure to the first supply oil passage165and the second supply oil passage166via the second distributing oil passage164.

The rotary electric machine111and the rotary electric machine112are connected to the first supply oil passage165in parallel with each other at the other end opposite to the end to which the first distributing oil passage163and the second distributing oil passage164are connected in parallel with each other. Similarly, the rotary electric machine111and the power transmission mechanism121are connected to the second supply oil passage166in parallel with each other at the other end opposite to the end to which the first distributing oil passage163and the second distributing oil passage164are connected in parallel with each other.

Thus, the rotary electric machine (MG1)111, the rotary electric machine (MG2)112and the power transmission mechanism121receive via the first supply oil passage165and the second supply oil passage166lubricating oil that is discharged from the MOP11or the EOP21and fed under pressure to the first distributing oil passage163or the second distributing oil passage164. As a result, the lubricated portions of these rotary electric machine (MG1)111, rotary electric machine (MG2)112and power transmission mechanism121are, for example, lubricated. At this time, in the power transmission mechanism121, particularly, the planetary gear122including the sun gear126, and the like, is supplied with lubricating oil and is, for example, lubricated. The rotary electric machine (MG1)111is supplied with lubricating oil from both the first supply oil passage165and the second supply oil passage166and is, for example, lubricated.

The hydraulic circuit161is configured to effectively obtain cooling effect from lubricating oil by interposing an oil cooler172in the first supply oil passage165. Of course, an oil cooler may also be interposed in the second supply oil passage166.

Relief valves173a,173bare installed in the first supply oil passage165. Each of the relief valves173a,173bfunctions when lubricating oil has a pressure equal to or higher than a certain pressure. Thus, each of the relief valves173a,173bprevents damage to the downstream-side rotary electric machines111,112. Each of the relief valves173a,173bhas a set operating pressure such that one constantly functions and the other auxiliary functions.

A check valve174ais installed in the first distributing oil passage163on the discharge side of the MOP11at a portion upstream of a portion at which the first supply oil passage165and the second supply oil passage166branch off. A check valve174bis installed in the second distributing oil passage164on the discharge side of the EOP21at a portion upstream of a portion at which the first supply oil passage165and the second supply oil passage166branch off. Each of the check valves174a,174bpermits flow of lubricating oil only in one direction. The check valve174arestricts backflow of lubricating oil from the first supply oil passage165or the second supply oil passage166to the first distributing oil passage163. The check valve174brestricts backflow of lubricating oil from the first supply oil passage165or the second supply oil passage166to the second distributing oil passage164. Thus, the check valves174a,174bprevent damage to the MOP11and the EOP21.

An orifice175is installed in the second supply oil passage166at a position downstream of the check valves174a,174b.The orifice175reduces fluctuations in the flow rate of lubricating oil that is supplied to the second supply oil passage166. Thus, lubricating oil is preferentially supplied to the rotary electric machines111,112via the first supply oil passage165.

Incidentally, as shown inFIG. 3, the rotary electric machine111according to the present embodiment is arranged across the planetary gear122of the power transmission mechanism121from the engine101, and the rotor shaft111ais rotatably supported by the housing111H so as to be coaxial with the output shaft101aof the engine101and the input shaft121aof the power transmission mechanism121.

The housing111H includes a front member111Ha, a body member111Hb, a partition member111Hc, a rear member111Hd and a pump housing111He. The housing111H is formed so as to accommodate the rotary electric machine111and the planetary gear122of the power transmission mechanism121.

The front member111Ha has a closed-end cylindrical shape such that an accommodation space for the planetary gear122is provided around the input shaft121aof the power transmission mechanism121. The input shaft121ais coupled to the output shaft101aof the engine101. The partition member111Hc is assembled to a cylindrical open end of the front member111Ha by screws. As a result, the front member111Ha accommodates the input shaft121aof the power transmission mechanism121in a state where the input shaft121aextends through the center of the cylindrical front member111Ha so as to be rotatable, and the accommodation space is closed.

The body member111Hb has substantially a cylindrical shape such that an accommodation space having such a diameter that the rotor115and stator116of the rotary electric machine111are allowed to be accommodated in the accommodation space. The partition member111Hc and both the rear member111Hd and the pump housing111He are respectively assembled to both ends of the cylindrical body member111Hb by screws. Thus, the accommodation space of the body member111Hb is closed.

The partition member111Hc is assembled to the front member111Ha. The partition member111Hc allows the coupling portion of the input shaft121aof the power transmission mechanism121with the rotor shaft111aof the rotary electric machine111to extend therethrough and supports the coupling portion so as to be rotatable. The partition member111Hc closes the accommodation space for the planetary gear122. The stator core116cof the stator116of the rotary electric machine111inside the body member111Hb is fixed to the partition member111Hc by screws.

The rear member111Hd has a flat ring shape such that the substantially disc-shaped pump housing111He is allowed to be connected to the center of the rear member111Hd. The outer peripheral side of the rear member111Hd is screwed to one end of the body member111Hb so as to face the partition member111Hc. The rear member111Hd closes the body member111Hb together with the pump housing111He.

The pump housing111He is fixed to the axis side of the rear member111Hd. The pump housing111He supports the rotor shaft111aof the rotary electric machine111such that the rotor shaft111ais rotatable, and holds the MOP11inside such that the MOP11rotates coaxially with the rotor shaft111aof the rotary electric machine111.

In the power transmission mechanism121, the sun gear126, the ring gear127, the carrier128, the pinion gears129and the drive gear131that constitute the planetary gear122are arranged around the input shaft121a.The planetary gear122of the power transmission mechanism121is accommodated in the space defined by the front member111Ha and partition member111Hc of the housing111H.

The rotor shaft111aof the rotary electric machine111is arranged along the same rotation axis as the input shaft121aso as to coaxially rotate integrally with the sun gear126of the power transmission mechanism121. The rotor115and stator116of the rotary electric machine111are arranged around the rotor shaft111a.The rotor115and stator116of the rotary electric machine111are accommodated in the space defined by the body member111Hb, partition member111Hc, rear member111Hd and pump housing111He of the housing111H. The stator core116cof the stator116is fixed to the partition member111Hc of the housing111H so as to face the rotor core115cof the rotor115, and the stator coil116wthat is supplied with electric power from the above-described battery is wound on the stator core116c.

As shown inFIG. 4in enlarged view, the sun gear126of the planetary gear122is supported on the outer periphery of the input shaft121aof the power transmission mechanism121so as to coaxially rotate with the input shaft121a.The sun gear126has a cylindrical portion126athat extends toward the rotor shaft111aof the rotary electric machine111along the outer periphery of the input shaft121aof the power transmission mechanism121. Splines126sare provided on the outer periphery of the cylindrical portion126a.Splines111sare also provided on the outer periphery of the end of the rotor shaft111aof the rotary electric machine111. The inner faces of cylindrical portions183,184of a flange-shaped member181respectively face the splines126sof the cylindrical portion126aof the sun gear126and the splines111sof the end of the rotor shaft111a.When splines183s,184srespectively provided on the inner faces of the cylindrical portions183,184of the flange-shaped member181are respectively in mesh with and spline-fitted to the splines126sof the cylindrical portion126aof the sun gear126and the splines111sof the end of the rotor shaft111a,the sun gear126of the power transmission mechanism121and the rotor shaft111aof the rotary electric machine111are coupled to each other so as to be relatively non-rotatable.

In the power transmission mechanism121, radial bearings191,192are respectively fitted at positions on both sides of the ring gear127in the rotation axis direction such that the radial bearing191is interposed between the ring gear127and the front member111Ha of the housing111H and the radial bearing192is interposed between the ring gear127and the partition member111Hc of the housing111H. The flange-shaped member181located on the rotor shaft111aof the rotary electric machine111has a disc-shaped portion185that protrudes radially outward. A thrust bearing193is fitted between the disc-shaped portion185and the partition member111Hc of the housing111H. Similarly, the input shaft121aof the power transmission mechanism121has a flange-shaped portion187that protrudes in a disc shape from the outer periphery on the side of the output shaft101aof the engine101. A thrust bearing195is fitted between the side face of the sun gear126and the flange-shaped portion187. A thrust bearing194is fitted between the front member111Ha of the housing111H and the flange-shaped portion187. The sun gear126and the front member111Ha are provided on both surface sides of the flange-shaped portion187. Thus, the power transmission mechanism121is rotatably supported such that the power transmission mechanism121is positioned in the thrust direction by the radial bearings191,192and the thrust bearings193,194,195on the outer peripheral side of the input shaft121aand a sliding load in the thrust direction or the radial direction is reduced.

Similarly, a radial bearing197is fitted between the rotor shaft111aof the rotary electric machine111and the partition member111Hc of the housing111H, and a radial bearing198is fitted between the rotor shaft111aof the rotary electric machine111and the pump housing111He of the housing111H. Thus, the rotor shaft111aof the rotary electric machine111is rotatably supported while a sliding load in the radial direction is reduced. That is, the housing111H including the partition member111Hc and the pump housing111He constitutes a case that supports the rotor shaft111asuch that the rotor shaft111ais rotatable.

Each of the rotor shaft111aof the rotary electric machine111and the input shaft121aof the power transmission mechanism121is formed of a hollow cylindrical member. A drive shaft31formed of a similar cylindrical member is accommodated in a hollow space111mof the rotor shaft111aof the rotary electric machine111. Splines121sare provided on the inner face of the rotary electric machine111-side end of the input shaft121aof the power transmission mechanism121.

Splines31sare provided on the outer periphery of the power transmission mechanism121-side end of the drive shaft31inside the rotor shaft111aof the rotary electric machine111. The splines31sare in mesh with and spline-fitted to the splines121sof the rotary electric machine111-side end of the input shaft121aof the power transmission mechanism121. The other end of the drive shaft31, opposite from the splines31s,is rotatably supported by the pump housing111He. Thus, the drive shaft31is integrally rotated coaxially with the input shaft121aof the power transmission mechanism121.

The pump housing111He is connected to the radially inner side of the rear member111Hd so as to be located at the side of the axis of the rotor shaft111aof the rotary electric machine111and supports the rotor shaft111avia the radial bearing198such that the rotor shaft111ais rotatable. The MOP11is connected to the drive shaft31that is rotatably supported inside the rotor shaft111a.

Although not shown inFIG. 3in details, the MOP11is formed of, for example, a general-purpose internal gear pump, an inner rotor is fixed to the drive shaft31, and an outer rotor is fixed to the pump housing111He. In this state, the MOP11is driven when the drive shaft31rotates integrally with the input shaft121aof the power transmission mechanism121, that is, the output shaft101aof the engine101. Thus, the MOP11discharges lubricating oil drawn and strained from the reservoir111Hp inside the housing111H to the first distributing oil passage163, and supplies the lubricating oil to the rotary electric machine111, the rotary electric machine112and the power transmission mechanism121via the first supply oil passage165or the second supply oil passage166for lubrication, and the like.

The power transmission mechanism121-side end of the drive shaft31is inserted in the input shaft121a,and an internal hollow space31mcommunicates with a hollow space121minside the input shaft121a.The end of the hollow space31mof the drive shaft31across from the input shaft121acommunicates with a flow passage33, thus constituting part of the second supply oil passage166. The flow passage33is formed by attaching a flow passage cover32to the external end faces of the rear member111Hd and pump housing111He. Communication holes121hare perforated at multiple portions of the input shaft121aof the power transmission mechanism121. The communication holes121hextend from the outer periphery to the hollow space121m.The communication holes121hfunction as the second supply oil passage166. Thus, lubricating oil flowing into the hollow space31mof the drive shaft31penetrates via the communication holes121hor gaps between the members. In this way, lubrication of sliding portions, such as the radial bearings191,192,197,198, thrust bearings193,194,195, and the like, of the rotary electric machine111and power transmission mechanism121accommodated inside the housing111H is ensured. The communication holes121hthat function as the second supply oil passage166are provided also in members, and the like, that constitute the ring gear127and the pinion gears129as needed.

For example, since the gap between the sun gear126and the inner faces of the cylindrical portions183,184of the flange-shaped member181connects with the hollow space121mof the input shaft121aof the power transmission mechanism121via the communication holes121hand functions as the second supply oil passage166, the radial bearing197is supplied with lubricating oil that is fed under pressure from the MOP11or the EOP21for lubrication. Since an outer surface side space111moof the drive shaft31in the hollow space111minside the rotor shaft111afunctions as the second supply oil passage166that is routed from the end of the rotor shaft111a,the radial bearing198is supplied with lubricating oil that is fed under pressure from the MOP11or the EOP21for lubrication.

Although not particularly described with reference to the drawing, the rotary electric machine112has a substantially similar configuration to the rotary electric machine111, and has such a structure that a rotor shaft united with a rotor inside a stator is rotatably supported by bearings provided at certain positions. As shown inFIG. 2, the bearings provided at certain positions are also similarly supplied with lubricating oil via the first supply oil passage165.

Each of the rotary electric machines111,112rotates the rotatably supported rotor shaft111awhen magnetic flux that is generated as a result of supply of driving electric power from the above-described battery to the stator coil116wlinks the stator core116cwith the rotor core115cto form a magnetic circuit. At this time, in each of the rotary electric machines111,112, since magnetic field varies as alternating-current power is supplied to the stator coil116w,induced electromotive force is generated due to electromagnetic induction that occurs in the peripheral members including the rotor core115caround the rotor shaft111aor the rotor shaft112a.For this reason, a potential difference can occur between the peripheral members and the rotor shaft111aor the rotor shaft112aand, as a result, a closed circuit through which current circulates may be formed.

For example, a current circuit that passes through the rotor shaft111ato the partition member111Hc of the housing111H via the radial bearing197or a current circuit that passes through the rotor shaft111ato the pump housing111He of the housing111H via the radial bearing198can be formed. In this case, there is a possibility of occurrence of electrolytic corrosion, such as surface roughness, on the bearing surface due to a spark that is developed on the radial bearing197or the radial bearing198.

Incidentally, as described above, lubricating oil that is supplied to the lubricated portions, such as the radial bearings197,198, is conceivably effectively utilized to prevent occurrence of electrolytic corrosion in the radial bearings197,198, and the like, since lubricating oil has an electrical insulating property, in addition to lubricating and cooling functions. That is, a withstand voltage characteristic against a potential difference that occurs as a result of the above-described electromagnetic induction also varies with the amount of lubricating oil remaining at the lubricated portions, such as the bearing surfaces of the radial bearings197,198.

In contrast, with the structure that lubricating oil that is discharged at a constant rate from the MOP11is supplied like the radial bearings197,198of the rotary electric machines111,112, depending on the operation status of each of the rotary electric machines111,112, lubricating oil, for example, may flow out as the lubricating oil on the bearing surfaces, and the like, of the radial bearings197,198is utilized, resulting in a situation that sufficient electrical insulating property is not obtained. This situation similarly occurs also in the case where lubricating oil that is discharged at a constant rate from the EOP21is supplied at the time when the vehicle travels in a so-called electric vehicle (EV) mode in which the engine101is stopped and only at least one of the rotary electric machines111,112is operated.

When the ECU1according to the present embodiment executes various control processes by executing control programs prestored in a memory2on the basis of various parameters, the ECU1operates the EOP21as needed by transmitting a control signal to the EOP21, thus increasing the supply of lubricating oil.

For example, when the ECU1efficiently drives the engine101and the rotary electric machines111,112in cooperation with each other on the basis of a torque that is required to output in response to the traveling status of the vehicle100, the ECU1executes the control process (control method) shown in the flowchart ofFIG. 5. Particularly, when the ECU1determines on the basis of the operating status of each of the rotary electric machines111,112that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, the ECU1increases the supply of lubricating oil by driving the EOP21under a driving condition different from that of a lubricating oil supply process in a steady state, and prevents occurrence of electrolytic corrosion.

At this time, when the MOP11is driven in interlocking with the operating engine101while the EOP21is stopped, the ECU1transmits a control signal for causing the EOP21to be driven as an auxiliary pump to start driving the EOP21at a preset rotation speed at which the EOP21discharges the increased supply of lubricating oil. When the EOP21is being driven in synchronization with the operation of at least one of the rotary electric machines111,112while the MOP11is stopped during a stop of the engine101, the ECU1transmits a control signal for enhancing lubrication to the EOP21to start driving the EOP21at a preset rotation speed at which the EOP21discharges the increased supply of lubricating oil in addition to the supply of lubricating oil in a steady state. That is, the hydraulic circuit161including the MOP11and the EOP21constitutes a lubrication mechanism according to the present embodiment, the ECU1constitutes a control unit, the MOP11constitutes a mechanical oil pump, and the EOP21constitutes an electric oil pump.

Specifically, the ECU1calculates a torque that is required to output from at least one of the rotary electric machines111,112on the basis of the traveling speed of the vehicle100, a driver's operational request, and the like, and determines an electric power to be supplied to the stator coil116w,or the like. At this time, the ECU1acquires an energization condition, such as a current value of supplied electric power commensurate with the output torque of at least one of the rotary electric machines111,112or an energization carrier frequency that determines the rotation speed, as an operation status, and determines whether there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like. When the ECU1determines that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, the ECU1executes electrolytic corrosion preventative process for increasing the supply of lubricating oil by the EOP21in parallel. The carrier frequency is a frequency that determines a pulse width modulation period in a pulse width modulation (PWM) control system. It is possible to adjust the rotation speed of each of the rotary electric machines111,112(rotor115) by adjusting the carrier frequency. In the present embodiment, the case where the rotation speed of each of the rotary electric machines111,112is adjusted with the use of the carrier frequency is described as an example; however, the method of adjusting the rotation speed of each of the rotary electric machines111,112is not limited to this method. Another parameter, such as a duty ratio, may be used instead.

When both a current energization condition that the acquired current value that is supplied to at least one of the rotary electric machines111,112exceeds a current threshold preset in the memory2and a frequency energization condition that the carrier frequency at which electric power is supplied to at least one of the rotary electric machines111,112exceeds a carrier threshold preset in the memory2are satisfied, the ECU1determines that the operation status of at least one of the rotary electric machines111,112can cause electrolytic corrosion to occur in the radial bearings197,198, and the like. That is, the ECU1constitutes an electrolytic corrosion determination unit. In the present embodiment, the case where affirmative determination that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, is made when both the current energization condition and the frequency energization condition are satisfied is described as an example; however, the method of determining a possibility of occurrence of electrolytic corrosion is not limited to this method. Affirmative determination may be made when only one of the current energization condition and the frequency energization condition is satisfied.

The ECU1counts the number of times of affirmative determination that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like. When the number of counts exceeds a threshold preset in the memory2, the ECU1permits execution of the electrolytic corrosion preventative process for increasing the supply of lubricating oil. When an elapsed time from the execution of the electrolytic corrosion preventative process exceeds an elapsed time threshold preset in the memory2, the ECU1ends the electrolytic corrosion preventative process, and returns the process to the process of supplying lubricating oil at the time when it is determined that there is no possibility of occurrence of electrolytic corrosion (in a steady state). Thus, the ECU1is able to prevent occurrence of electrolytic corrosion while avoiding wasteful frequent execution of the electrolytic corrosion preventative process based on the possibility of damage due to electrolytic corrosion, and is also able to avoid useless continuation of the increased amount of lubricating oil through the electrolytic corrosion preventative process. That is, the ECU1constitutes a lubrication control unit.

More specifically, the ECU1executes the electrolytic corrosion preventative control process shown in the flowchart ofFIG. 5in accordance with a predetermined sampling period, and initially acquires the current value of electric power supplied and the carrier frequency of electric power supplied as the operation status of each of the rotary electric machines111,112(step S11). The current value of electric power supplied is a first energization condition. The carrier frequency of electric power supplied is a second energization condition.

Subsequently, the ECU1determines whether the current value, that is, the first energization condition, of electric power that is supplied to at least one of the rotary electric machines111,112exceeds a set current threshold (step S12). When the current value does not exceed the set current threshold, the ECU1proceeds to step S20, and once ends the control process.

Subsequently, after the ECU determines that the current value of electric power that is supplied to at least one of the rotary electric machines111,112exceeds the set current threshold, the ECU1further determines whether the carrier frequency, that is, the second energization condition, of electric power that is supplied to at least one of the rotary electric machines111,112exceeds the set carrier threshold (step S13). When the carrier frequency does not exceed the set carrier threshold, the ECU1proceeds to step S20, and once ends the control process.

Subsequently, after the ECU1determines that the carrier frequency of electric power that is supplied to at least one of the rotary electric machines111,112exceeds the set carrier threshold, the ECU1determines that there is a possibility of occurrence of electrolytic corrosion that should be prevented by increasing the supply of lubricating oil to the radial bearings197,198, and the like, utilizes a provided counter function, starts up a counter and increments the counter by 1 (step S14).

At this time, as shown inFIG. 6AtoFIG. 6C, when the energization current value that is supplied to each of the rotary electric machine111,112does not exceed the set current threshold or when the energization carrier frequency of electric power supplied does not exceed the set carrier threshold even when the energization current value exceeds the set current threshold, the ECU1determines that there is a low possibility of occurrence of electrolytic corrosion that requires the increased supply of lubricating oil, and does not start counting.

Subsequently, the ECU1determines whether the number of counts of the counter exceeds the set threshold (step S15). When the number of counts does not exceed the set threshold, the ECU1once ends the control process.

Subsequently, after the ECU1repeats the above-described step S11to step S15at the predetermined sampling period and determines that the number of counts of the counter that counts determination that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, exceeds the set threshold, the ECU1executes the electrolytic corrosion preventative process for increasing the supply of lubricating oil by the EOP21(step S16-1). At this time, when the EOP21is stopped, the ECU1starts up the EOP21and increases the supply of lubricating oil by driving the EOP21at a preset rotation speed, whereas, when the EOP21is being driven at a steady rotation speed, the ECU1increases the supply of lubricating oil by increasing the rotation speed of the EOP21to the preset rotation speed.

Thus, as shown inFIG. 6AtoFIG. 6D, it is determined at appropriate timing that the radial bearings197,198, and the like, of at least one of the rotary electric machines111,112are placed in an operating situation in an operation state where there is a possibility of occurrence of electrolytic corrosion, and lubricating oil that is supplied to these lubricated portions is increased. As a result, the insulating property on the radial bearings197,198, and the like, is improved to such an extent that it is possible to prevent occurrence of electrolytic corrosion due to a spark, or the like.

Subsequently, the ECU1utilizes the counter function, starts up a timer, and starts measuring an elapsed time from when the supply of lubricating oil is increased by the EOP21(step S17).

Subsequently, the ECU1repeatedly determines whether the measured time of the timer that measures the duration of the electrolytic corrosion preventative process that uses the EOP21exceeds the set elapsed time threshold (step S18).

Subsequently, after the ECU1determines in step S18that the measured time of the timer exceeds the set elapsed time threshold, the ECU1ends the electrolytic corrosion preventative process, and returns the EOP21to a driving state before the supply of lubricating oil is increased (step S19-1).

Thus, as shown inFIG. 6CandFIG. 6D, it is possible to avoid unnecessary continuation of the increased supply of lubricating oil after the supply of lubricating oil is increased until the electrical insulating property of the radial bearings197,198, and the like, of each of the rotary electric machines111,112is recovered and a necessary and sufficient amount of lubricating oil is supplied. As a result, it is possible to prevent useless deterioration of fuel efficiency through electric power consumption, and the like, caused by the driving of the EOP21.

Subsequently, the ECU1, for example, resets the counter function utilized as the counter or the timer in preparation to start the next electrolytic corrosion preventative process (step S20), and then once ends the control process.

Therefore, for example, as shown inFIG. 6AtoFIG. 6D, when the operation state where there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, of at least one of the rotary electric machines111,112is continued, it is determined again that there is a possibility of occurrence of electrolytic corrosion, and the electrolytic corrosion preventative process for increasing the supply of lubricating oil is similarly resumed. Thus, the electrical insulating property at the lubricated portions is maintained.

In this way, the ECU1according to the present embodiment is able to appropriately determine whether there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, of at least one of the rotary electric machines111,112, and, when there is the possibility, the ECU1is able to increase the supply of lubricating oil to the lubricated portions, such as the radial bearings197,198, with the use of lubricating oil that is discharged from the EOP21for only a certain period of time. For this reason, it is possible to prevent occurrence of electrolytic corrosion due to a spark, or the like, by ensuring the electrical insulating property provided by lubricating oil on the radial bearings197,198, and the like.

Therefore, the frequency of maintenance of the radial bearings197,198, and the like, of each of the rotary electric machines111,112does not increase due to occurrence of electrolytic corrosion, cost is reduced by reducing the number of times of the maintenance, and the quality of rotation of the radial bearings197,198, and the like, is ensured.

Next,FIG. 7A,FIG. 7BandFIG. 8are views that illustrate a rotary electric machine system according to a second embodiment of the disclosure. The configuration of the present embodiment is substantially similar to the configuration of the above-described first embodiment. Like reference numerals denote similar components, so similar description is omitted and a characteristic portion will be described (this also applies to a third embodiment that will be described later).

Second Embodiment

As shown inFIG. 7AandFIG. 7B, a pressure regulating valve41is installed on the discharge side of the MOP11in the first distributing oil passage163of the hydraulic circuit161in which the MOP11and the EOP21are incorporated, and a pressure regulating valve42is installed on the discharge side of the EOP21in the second distributing oil passage164of the hydraulic circuit161. The pressure regulating valve41is set so as to reduce the hydraulic pressure of lubricating oil that is discharged to the first distributing oil passage163to a certain pressure in order not to receive the influence of fluctuations in pressure that is discharged from the MOP11. The pressure regulating valve42is set so as to reduce the hydraulic pressure of lubricating oil that is discharged to the second distributing oil passage164to a certain pressure in order not to receive the influence of fluctuations in pressure that is discharged from the EOP21. That is, the pressure regulating valves41,42constitute a pressure reducing valve.

In the hydraulic circuit161according to the present embodiment, a bypass oil passage45that bypasses the pressure regulating valve41is provided in the first distributing oil passage163, and a bypass oil passage46that bypasses the pressure regulating valve42is provided in the second distributing oil passage164. A solenoid valve45vthat is controlled to be driven by the ECU1is provided in the bypass oil passage45. A solenoid valve46vthat is controlled to be driven by the ECU1is provided in the bypass oil passage46.

When the ECU1determines that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, and then executes the electrolytic corrosion preventative process by executing the control programs prestored in the memory2on the basis of various parameters, the ECU1operates at least one of the solenoid valves45v,46vas needed by transmitting a control signal to the at least one of the solenoid valves45v,46vto switch from a closed state to an open state. The solenoid valve45vswitches the bypass oil passage45from the closed state to the open state. The solenoid valve46vswitches the bypass oil passage46from the closed state to the open state. Thus, the path of supplying lubricating oil that is discharged from the MOP11is switched from the first distributing oil passage163to the bypass oil passage45. Lubricating oil is reduced in pressure by the pressure regulating valve41to a predetermined pressure and is supplied to the first distributing oil passage163. Lubricating oil is allowed to be supplied to the bypass oil passage45without being reduced in pressure. The path of supplying lubricating oil that is discharged from the EOP21is switched from the second distributing oil passage164to the bypass oil passage46. Lubricating oil is reduced in pressure by the pressure regulating valve42to a predetermined pressure and is supplied to the second distributing oil passage164. Lubricating oil is allowed to be supplied to the bypass oil passage46without being reduced in pressure. That is, the solenoid valves45v,46vconstitute a switching unit.

For example, the ECU1is configured to drive one or both of the solenoid valves45v,46vat the time when it is determined that there is a possibility of occurrence of electrolytic corrosion by executing the control process (control method) shown in the flowchart ofFIG. 8. Thus, by supplying lubricating oil that is discharged from the operating MOP11via the bypass oil passage45or the operating EOP21via the bypass oil passage46, it is possible to increase the supply of lubricating oil to the radial bearings197,198, and the like, where there is a possibility of occurrence of electrolytic corrosion. That is, the first distributing oil passage163and the second distributing oil passage164constitute a first oil passage, and the bypass oil passages45,46constitute a second oil passage.

More specifically, as in the case of the above-described embodiment, the ECU1acquires the current value (first energization condition) and carrier frequency (second energization condition) of electric power supplied as the operation status of each of the rotary electric machines111,112(step S11). When the current value exceeds the set current threshold (step S12), and when the carrier frequency exceeds the set carrier threshold (step S13), the ECU1determines that there is a possibility of occurrence of electrolytic corrosion and increments the counter by 1 (step S14).

After that, when the number of counts of the counter exceeds the set threshold (step S15), the ECU1according to the present embodiment opens the bypass oil passage45by driving the solenoid valve45vfor the operating MOP11or the bypass oil passage46by driving the solenoid valve46vfor the operating EOP21, thus executing the electrolytic corrosion preventative process for increasing the supply of lubricating oil to the radial bearings197,198, and the like, where there is a possibility of occurrence of electrolytic corrosion (step S16-2).

Thus, as in the case of the above-described embodiment, the insulating property on the radial bearings197,198, and the like, is improved to such an extent that it is possible to prevent occurrence of electrolytic corrosion due to a spark, or the like.

Subsequently, the ECU1starts up the timer and starts measuring an elapsed time from when the supply of lubricating oil is increased (step S17). When the measured time of the timer exceeds the set elapsed time threshold (step S18), the ECU1closes the bypass oil passage45by stopping the driving of the solenoid valve45vor closing the bypass oil passage46by stopping the driving of the solenoid valve46v,thus returning the supply of lubricating oil from the MOP11or the EOP21to the supply of lubricating oil before the supply of lubricating oil is increased, that is, the time when it is determined that there is no possibility of occurrence of electrolytic corrosion (in a steady state) (step S19-2), and then resets the counter and the timer (step S20), after which the ECU1once ends the control process.

In this way, the ECU1according to the present embodiment, as in the case of the above-described embodiment, is able to supply the increased amount of lubricating oil while the hydraulic pressure of lubricating oil that is discharged from the MOP11or the EOP21remains unchanged when the ECU1determines that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, of at least one of the rotary electric machines111,112. As a result, the electrical insulating property of lubricating oil on the radial bearings197,198, and the like, is ensured, so cost is reduced and the quality of rotation is ensured.

Third Embodiment

Next,FIG. 9is a flowchart that illustrates a rotary electric machine system according to a third embodiment of the disclosure. The case where the configuration of the present embodiment is substantially similar to the configuration of the above-described first embodiment will be described as an example; however, the configuration of the present embodiment is not limited to this configuration. Of course, the configuration of the present embodiment may be applied to the second embodiment. As shown inFIG. 9, the ECU1executes processes similar to step S11to step S13in parallel with step S18according to the above-described first embodiment in which the ECU1repeatedly determines whether the elapsed time from when the supply of lubricating oil is increased, which is measured by the timer, exceeds the set elapsed time threshold. When the ECU1does not determine that there is a possibility of occurrence of electrolytic corrosion, the ECU1interrupts the process of increasing the supply of lubricating oil and restricts the supply of lubricating oil.

Specifically, the ECU1executes control process (control method) similar to that of the above-described first embodiment, acquires the current value (first energization condition) and carrier frequency (second energization condition) of electric power supplied as the operation status of each of the rotary electric machines111,112(step S11). When the current value exceeds the set current threshold (step S12) and when the carrier frequency exceeds the set carrier threshold (step S13), the ECU1determines that there is a possibility of occurrence of electrolytic corrosion and increments the counter by 1 (step S14).

Subsequently, when the number of counts of the counter exceeds the set threshold (step S15), the ECU1executes the electrolytic corrosion preventative process for increasing the supply of lubricating oil from the EOP21(step S16-1).

Subsequently, after the ECU1starts up the timer and starts measuring the elapsed time from when the supply of lubricating oil is increased (step S17), the ECU1determines whether the elapsed time from when the supply of lubricating oil, which is measured by the timer, exceeds the set elapsed time threshold (step S18-1).

After that, the ECU1according to the present embodiment, as well as step S11to step S13, acquires the first energization condition and second energization condition of electric power that is supplied to each of the rotary electric machines111,112(step S18-2), determines whether the current value continuously exceeds the set current threshold (step S18-3), and further determines whether the carrier frequency also continuously exceeds the set carrier threshold (step S18-4).

After the ECU1determines in these step S18-2to step S18-4that both of the energization conditions exceed the corresponding thresholds, the ECU1returns to step S18-1and repeats a similar process. When the ECU1determines that the measured elapsed time from when the supply of lubricating oil is increased exceeds the set elapsed time threshold, the ECU1proceeds to step S19-1in the above-described embodiment, ends the electrolytic corrosion preventative process, and returns the EOP21to a driving state before the supply of lubricating oil is increased.

After the ECU1determines in step S18-2to step S18-4that both of the energization conditions do not exceed the corresponding thresholds, the ECU1determines that there is a low possibility of occurrence of electrolytic corrosion (step S18-5), and interrupts the electrolytic corrosion preventative process and returns the EOP21to a driving state before the supply of lubricating oil is increased (step S19-3).

Subsequently, the ECU1, for example, resets the counter function utilized as the counter and the timer in preparation to start the next electrolytic corrosion preventative process (step S20), and then once ends the control process.

Thus, after it is determined that there is a low possibility of occurrence of electrolytic corrosion, it is possible to immediately stop the increased supply of lubricating oil, so it is possible to eliminate deterioration of fuel efficiency resulting from an unnecessarily increased amount of lubricating oil.

In this way, in addition to the operation and advantageous effects obtained from the above-described embodiments, when it is not determined that there is a possibility of occurrence of electrolytic corrosion in the radial bearings197,198, and the like, of each of the rotary electric machines111,112, the ECU1according to the present embodiment is able to avoid unnecessary continuation of the electrolytic corrosion preventative process for increasing the supply of lubricating oil. As a result, it is possible to prevent useless deterioration of fuel efficiency through electric power consumption, and the like, caused by the driving of the EOP21.

In an alternative embodiment to the above-described embodiments, it is determined whether there is a possibility of occurrence of electrolytic corrosion by comparing each of the current energization condition and frequency energization condition with the corresponding fixed current threshold and carrier threshold in the above-described embodiments; however, a method of determining whether there is a possibility of occurrence of electrolytic corrosion is not limited to this method.

For example, in a first alternative embodiment, as indicated by the continuous line inFIG. 10, a determination curve map that uses the current threshold and the carrier threshold as parameters may be prestored in the memory2. The ECU1may acquire the energization current value and the energization carrier frequency, and may determine whether there is a possibility of occurrence of electrolytic corrosion on the basis of whether the energization conditions exceed the determination curve in the map. As indicated by the dashed lines inFIG. 10, a plurality of types of determination curves may be stored in the memory2so as to be selectable in accordance with the strictness of determination.

In a second alternative embodiment, although not shown in the drawing, instead of comparing the energization current value corresponding to the output torque that is required from at least one of the rotary electric machines111,112with the current threshold, a torque threshold is stored in the memory2such that the output torque is directly usable. The ECU1is able to determine whether there is a possibility of occurrence of electrolytic corrosion on the basis of whether the acquired output torque exceeds the torque threshold.

In a third alternative embodiment, although not shown in the drawing, instead of comparing the energization carrier frequency corresponding to the rotation speed that is required from at least one of the rotary electric machines111,112with the carrier threshold, a speed threshold is stored in the memory2such that the rotation speed is directly usable. The ECU1is able to determine whether there is a possibility of occurrence of electrolytic corrosion on the basis of whether the acquired rotation speed exceeds the speed threshold.

The embodiments of the disclosure are described; however, it is obvious to persons skilled in the art that the embodiments may be modified without departing from the scope of the disclosure. All of such modifications and equivalents thereof are intended to be included in the appended claims.