Drive apparatus for hybrid vehicle

A drive apparatus for a hybrid vehicle is provided with a first motor generator, a power splitting mechanism portion, and a second motor generator. The first motor generator functions mainly as a generator. The power splitting mechanism portion divides the power generated by the engine into power for the first motor generator and power for driven wheels. The second motor generator has an outside diameter that is smaller than the outside diameter of the first motor generator and is arranged on the side of the first motor generator opposite the engine. Further, a speed reducing mechanism portion which has an outside diameter smaller than the outside diameter of the second motor generator and which reduces the rotation speed of the second motor generator is provided on the side of the second motor generator opposite the engine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a drive apparatus for a hybrid vehicle that is preferably used in a hybrid vehicle provided with an engine and an electric motor, which are two types of power sources having different characteristics, and which runs by using the driving power from these two power sources in a combination that is optimal for the conditions.

2. Description of the Related Art

In recent years a hybrid vehicle provided with an engine and an electric motor, which are two types of power sources having different characteristics, has been developed and put into practical use. In this hybrid vehicle, the strengths of each power source are used to compensate for the weaknesses of the other by using the driving power from the type types of power sources in a combination that is optimal for the conditions. As a result, the power performance of the vehicle is able to be sufficiently ensured and the fuel consumption rate and emission performance are able to be largely improved.

Various proposals have been made for the drive apparatus to be used in this type of hybrid vehicle. One proposal includes the use of a first motor generator, a power splitting mechanism portion, and a second motor generator. The first motor generator serves mainly as a generator. The power splitting mechanism portion includes a planetary gear set and divides the power generated by the engine into power for the first motor generator and power for the driven wheels. The second motor generator serves mainly as a motor and generates power to assist in driving the driven wheels. This power is different from the power that is from the engine.

In this drive apparatus, part of the power that has been split by the power splitting mechanism portion is transmitted mechanically to the driven wheel to rotate it, and the rest of the power that has been split is transmitted to the first motor generator. Using the power transmitted to the first motor generator, the first motor generator functions as a generator and generates electricity which is supplied to the second motor generator. Using this electricity, the second motor generator functions as a motor. The power generated by this second motor generator is added to the power that was split by the power splitting mechanism portion and transmitted to the driven wheel, thereby assisting the output of the engine in driving the driven wheel.

Also, as art relating to the layout of each of the component parts in the drive apparatus for a hybrid vehicle, art in which a first motor generator, a second motor generator, and a planetary gear set are arranged in-line is disclosed in Japanese Patent Application Laid-Open Publication No. 6-144020. This arrangement is advantageous in that the build, more particularly the outside diameter, becomes gradually smaller farther away from the engine, thereby enabling the entire apparatus to be made compact.

With the drive apparatus for a hybrid vehicle, it is conceivable to add a speed reducing mechanism portion to reduce the rotation speed and to increase the torque of the second motor generator which serves as the motor. With the drive apparatus disclosed in the aforementioned publication, however, a layout when this speed reducing mechanism portion is added to the planetary gear set as a power splitting mechanism portion is not shown in detail. Therefore, there is a desire for a drive apparatus in which the entire apparatus, including this speed reducing mechanism portion, can be made compact.

SUMMARY OF THE INVENTION

In view of the foregoing circumstance, it is an object of this invention to provide a drive apparatus for a hybrid vehicle in which a speed reducing mechanism portion is able to be mounted while making the entire apparatus compact.

Hereinafter, the method and effects for achieving the foregoing object shall be described.

A drive apparatus for a hybrid vehicle according to a first aspect of the invention to achieve the foregoing object is provided with a first motor generator which functions as one of a motor and a generator; a power splitting mechanism portion that divides power generated by an engine into power for the first motor generator and power for a driven wheel; a second motor generator which is arranged on a side of the first motor generator opposite the engine, which functions as one of a motor and a generator, which generates power to drive the driving wheel, this power being different from the power that is from the engine, and which has an outside diameter that is smaller than an outside diameter of the first motor generator; and a speed reducing mechanism portion which is arranged on a side of the second motor generator opposite the engine, which has an outer diameter that is smaller than an outside diameter of the second motor generator, and which reduces a rotation speed and increases a torque of the second motor generator.

According to the drive apparatus for a hybrid vehicle of the aforementioned construction, the power generated by the engine is divided into two by the power splitting mechanism portion. Part of the power is transmitted mechanically to the driven wheel so as to rotate it and the rest of the power is transmitted to the first motor generator. Using the power transmitted to the first motor generator, the first motor generator functions as a generator and generates electricity which is supplied to the second motor generator. Using this electricity, the second motor generator functions as a motor. The power generated by this second motor generator is added to the power that was split by the power splitting mechanism portion and transmitted to the wheels, thereby assisting the output of the engine in driving the driven wheel.

According to the drive apparatus for a hybrid vehicle, at least both of the motor generators and the speed reducing mechanism portion, from among the component parts, are arranged in the order of the first motor generator, the second motor generator, and the speed reducing mechanism portion from the side near the engine to the side away from the engine. In addition to the outside diameter of the second motor generator being smaller than the outside diameter of the first motor generator, the outside diameter of the speed reducing mechanism portion is also smaller than the outside diameter of the second motor generator. Therefore, by having the outside diameter of the power splitting mechanism portion be smaller than the outside diameter of the first motor generator, the drive apparatus takes on a conical shape in which the outside diameter thereof becomes increasingly small away from the engine. In this way, according to the invention described above, it is possible to incorporate the speed reducing mechanism portion into the drive apparatus while making the entire apparatus compact.

Furthermore, the mountability in the hybrid vehicle of this drive apparatus that has been made compact in this way is excellent. In particular, the shape of the entire drive apparatus for a hybrid vehicle is substantially the same as the shape of a typical automatic transmission with a torque converter and a gear change mechanism. Therefore, by designing the drive apparatus for a hybrid vehicle so that it is substantially the same size as the automatic transmission, the drive apparatus is able to be housed in a floor tunnel that already exists in vehicles for housing the automatic transmission. Therefore, it is possible to arrange the drive apparatus, instead of the automatic transmission, in this floor tunnel.

A drive apparatus for a hybrid vehicle according to another aspect of the invention has an outside shape that becomes increasingly narrow away from the engine, and is further provided with a core case in which to mount both of the motor generators and the power splitting mechanism portion, a case formed separate from the core case, in which to mount the speed reducing mechanism portion, and a joining portion with which to join the case to the core case.

According to this construction, when expanding the use of the drive apparatus to a wide variety of hybrid vehicles, if the specifications, such as those of the gear ratio of the speed reducing mechanism portion, can be conformed to the vehicle, the motor generators and the power splitting mechanism portion and the like can be used as they are as common parts. Here, the case in which the speed reducing mechanism portion is mounted is independent from the core case in which both of the motor generators and the power splitting mechanism portion are mounted, and these cases can be joined to, and separated from, one another. As a result, by preparing a unit part in which the speed reducing mechanism portion is mounted in the case for each type of hybrid vehicle, there only needs to be one type of unit (core unit) in which both of the motor generators and the power splitting mechanism portion are mounted in the core case, regardless of the type of the hybrid vehicle. Then, when assembling a plurality of kinds of the drive apparatuses in an assembly plant or the like, the unit part in which the particular speed reducing mechanism portion that matches the type of drive apparatus is simply selected and attached to the common core unit.

Further, a drive apparatus for a hybrid vehicle according to another aspect of the invention is further provided with a first connecting portion to electrically connect a first cable to the first motor generator, and a second connecting portion to electrically connect a second cable to the second motor generator. In addition, the power splitting mechanism portion is arranged between the first motor generator and the second motor generator and includes a planetary gear set which has a ring gear that has a smaller outside diameter than the outside diameters of the first motor generator and the second motor generator. The first connecting portion and the second connecting portion are provided in a space that exists toward the outside in the radial direction of the ring gear between the first motor generator and the second motor generator.

According to this construction, the power splitting mechanism portion is constructed with a planetary gear set arranged between the two motor generators. In addition, the outside diameter of the ring gear, which determines the outer shape of the entire planetary gear set, is smaller than the outside diameters of both of the motor generators. As a result, a space is created toward the outside in the radial direction of the ring gear between the two motor generators. According to this invention described above, a first connecting portion to electrically connect a first cable to the first motor generator is provided in this space. In addition, a second connecting portion to electrically connect a second cable to the second motor generator is also provided in this space. In this way, by providing both of the connecting portions together in the space between the motor generators, space is able to be used efficiently. As a result, both connecting portions are able to be arranged without losing compactness of the drive apparatus.

A drive apparatus for a hybrid vehicle according to another aspect of the invention is further provided with a drive case in which the first motor generator and the second motor generator are mounted, and which has an outside shape that becomes increasingly narrow away from the engine; a first outlet, which is provided in the drive case and which is formed curved away from the engine, and through which the first cable that is connected to the first motor generator is led out of the drive case; and a second outlet, which is provided in the drive case on a side of the first outlet opposite the engine and which is formed parallel to the first outlet, and through which the second cable that is connected to the second motor generator is led out of the drive case.

According to this construction, the first cable that is connected to the first motor generator is led out of the drive case through the first outlet. Also, the second cable that is connected to the second motor generator is led out of the drive case through the second outlet. Here, the first outlet and the second outlet are both provided in the drive case which becomes increasingly narrow away from the engine. Also, the second outlet is positioned on the side of the first outlet opposite the engine, i.e., in a location having a smaller diameter than the first outlet in the drive case. In addition, both the first outlet and the second outlet are curved away from the engine and parallel to each other. As a result, when the connection mates of both of the cables are provided on the side of the drive apparatus opposite the engine, both of the cables can be led out to the outside of the drive case together without interfering with one another and laid toward the connection mate.

Also, a drive apparatus for a hybrid vehicle according to another aspect of the invention is further provided with a drive case which has an outside shape that becomes increasingly narrow away from the engine and in which the first motor generator and the second motor generator are mounted; a first case which forms part of the drive case and which is provided with a first main portion fixed to the engine and a first housing portion formed within the first main portion, which houses the first motor generator; a second case which forms part of the drive case and which is joined to the first main portion; a first cover which is arranged on the engine side of the first generator within the first main portion and which covers the first motor generator; and a first fastening member that attaches a first flange formed on an outer edge portion of the first cover to the first housing portion.

According to this construction, in this drive apparatus, the drive case in which the motor generator is mounted has an outside shape that becomes increasingly narrow away from the engine. The first case that forms part of the drive case is fixed to the engine at the first main portion which is the outside portion (outer shell) of the first case. The motor generator is housed in the first housing portion formed within the first main portion. Also, the second case that forms part of the drive case, just as does the first case, is joined to the first main portion.

A cover, which covers the motor generator, is arranged within the first main portion. The cover is attached to the first housing portion by a first fastening member at a flange formed on an outer edge portion of the cover. Here, when the cover is not used, the size (outside diameter) in the radial direction of the first case is used as a reference. In this case, the outside diameter of the first case is actually determined only by the thickness of the first main portion. In contrast, when the cover is used, the outside diameter of the first case is determined by a width of the flange on the cover and a gap between the flange and the inside surface of the first main portion, in addition to the aforementioned thickness of the first main portion.

Regarding this point, according to the invention described above, the cover is arranged on the engine side of the motor generator within the first main portion. The outside diameter of the first main portion at this location is comparatively larger than the general outside diameter around the first main portion. In particular, the diameter of the first main portion at a location corresponding to the end portion on the engine side of the first housing portion is definitely larger than the diameter of the first main portion at a location corresponding to the end portion on the side of the first housing portion opposite the engine. The size relationship of the distance between the inside surface of the first housing portion and the inside surface of the first main portion is the same as described above. Therefore, because the distance tends to be larger than the sum of the width of the first flange on the first cover and the gap between the first flange and the first main portion, in this case, even if the first main portion does not extend outward in the radial direction, the first cover can still be arranged within the first main portion and attached to the first housing portion by the first fastening member.

In this way, it is possible to suppress the outside diameter of the first case from becoming larger with the first cover attached, and therefore maintain the original outer shape of the drive case, in which it becomes increasingly narrow away from the engine. This outer shape is similar to the outer shape of an automatic transmission provided with a torque converter and a gear change mechanism, which is housed in a vehicle having a front engine rear drive (i.e., FR) type drive system. As a result, it is possible to arrange the drive apparatus, instead of an automatic transmission, in a floor tunnel that ordinarily houses the automatic transmission, and thus improve mountability of the drive apparatus in the vehicle.

Also, the drive apparatus for a hybrid vehicle is further provided with a second main portion which is provided with the second case and which is joined to the first main portion; a second housing portion which is formed within the second main portion and which houses a second motor generator that functions as one of a motor and a generator; a second cover which is arranged on the engine side of the second motor generator within the second main portion and which covers the second motor generator; and a second fastening member that attaches a second flange formed on an outer edge portion of the second cover to the second housing portion.

According to this construction, in this drive apparatus, the second case that forms part of the drive case, just as does the first case, is joined to the first main portion at the second main portion that is the outside portion (outer shell) of the second case. The second motor generator is housed in the second housing portion formed within the second main portion.

A second cover that covers the second motor generator is formed within the second main portion. This second cover is attached to the second housing portion by second fastening member at a second flange formed on an outer edge portion of the second cover. Here, when the cover is not used, the size (outside diameter) in the radial direction of the second case is used as a reference. In this case, the outside diameter of the second case is actually determined only by the thickness of the second main portion. In contrast, when the cover is used, the outside diameter of the second case is determined by a width of the second flange on the second cover and a gap between the second flange and the inside surface of the second main portion, in addition to the aforementioned thickness of the second main portion.

This drive apparatus for a hybrid vehicle is such that the second cover is arranged on the engine side of the second motor generator within the second main portion. The outside diameter of the second main portion in this location is comparatively larger than the general outside diameter around the second main portion. In particular, the outside diameter of the second main portion in the location corresponding to the end portion on the engine side of the second housing portion is definitely larger than the outside diameter of the second main portion at a location corresponding to the end portion on the side of the second housing portion opposite the engine. The size relationship of the distance between the inside surface of the second housing portion and the inside surface of the second main portion is the same as described above. Therefore, because the distance tends to be larger than the sum of the width of the second flange on the second cover and the gap between second flange and the inside surface of the second main portion, in this case, even if the second main portion does not extend outward in the radial direction, the second cover can still be arranged within the second main portion and attached to the second housing portion by the second fastening member. In this way, it is possible to suppress the outside diameter of the second case from becoming larger with the second cover attached, such that mountability of the drive apparatus in the vehicle is further improved.

In the drive apparatus for a hybrid vehicle, the speed reducing mechanism portion includes a planetary gear set and is arranged on the same axis as the axial center of the first motor generator, the second motor generator, and the power splitting mechanism portion.

According to this construction, the speed reducing mechanism portion can achieve a large reduction ratio because it includes a planetary gear set. Also, the size of the drive system in the radial direction is minimized by arranging the first motor generator, the second motor generator, the power splitting mechanism portion, and the speed reducing mechanism portion, which together make up the drive apparatus, on the same axis.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, a first exemplary embodiment of the invention, in which a hybrid vehicle having a front engine rear drive (i.e., FR) type drive system has been implemented, will be described with reference to the drawings.FIG. 1is a block diagram schematically showing a hybrid vehicle11as seen from below. The hybrid vehicle11shown here is provided with two types of power sources, an engine12and an electric motor, which have different characteristics. The hybrid vehicle11runs by transmitting driving power to driven wheels13from these two power sources in a combination that is optimal for the conditions. In the figure, the front of the hybrid vehicle11is to the left and the rear is to the right.

Between the engine12and the driven wheels13are provided a drive apparatus14, a propeller shaft15, a differential16, and a pair of axle shafts17and the like. The drive apparatus14will be described in detail later. The propeller shaft15is a shaft that transmits output force from the drive apparatus14to the differential16. The differential16is a differential gear that divides power from the propeller shaft15and transmits it to both of the axle shafts17. Each axle shaft17is an axle that transmits the power divided by the differential16to the driven wheels13.

Among these parts, the drive apparatus14and the propeller shaft15are arranged in a floor tunnel19provided in a floor18of the hybrid vehicle11. The portion of the floor tunnel19in which the drive apparatus14is arranged is widest near the engine12and becomes increasingly narrow away from the engine12. In a vehicle having an FR type drive system such as this, the space in the floor tunnel19is used to house the drive apparatus14and the propeller shaft15. This space is narrower than the housing space in a vehicle having a different type of drive system such as a front engine front drive (i.e., FF) type system.

As shown inFIG. 2, a drive case21of the drive apparatus14includes a core case22which is formed of a first case23and a second case24, and a third case25. These cases23through25are arranged in order along an axial line L of a crankshaft47, which is an output shaft of the engine12, toward the side (the right side inFIG. 2) away from the side near the engine12(the left side inFIG. 2).

Referring toFIG. 4, the first case23includes a first main portion23a,which is the outside (outer shell) portion of the first case23, and a first housing portion23bintegrally formed with the inner portion of the first main portion23a. The first main portion23ahas a cylindrical outer shape and is fastened at an end portion thereof on the engine12side to the engine12with a fastening member, not shown, such as a bolt. The diameter (both outside diameter and inside diameter) of the first main portion23ais greatest at the end portion on the engine12side and gradually decreases farther away from the engine12until the mid portion in the axial direction. The diameter of the first main portion23aat the end portion on the driven wheel side is partly and slightly larger than the diameter of the mid portion in the axial direction in order to ensure space to attach a first cable63, to be described later.

The first housing portion23bhas a substantially cylindrical shape with one end closed, in which the inside diameter is substantially the same at any given location. The end portion of the first housing portion23bon the engine side does not extend as far (toward the driven wheels13side) as the end portion of the first main portion23aon the engine side. Also, the end portion of the first housing portion23bon the driven wheel side does not extend as far (toward the engine12side) as the end portion of the first main portion23aon the driven wheel side. The end portion of the first housing portion23bis constructed with a first support wall31formed substantially orthogonal with respect to the axial line L at the end portion of the first housing portion23bon the driven wheel side.

As shown inFIGS. 5 and 6, a second case24includes a second main portion24awhich forms the outside (outer shell) portion of the second case24and a second housing portion24bintegrally formed with the inner portion of the second main portion24a. The second main portion24ahas a substantially cylindrical external shape and is fastened at an end portion thereof on the engine side to the first main portion23awith a fastening member, not shown, such as a bolt. The diameter (both outside diameter and inside diameter) of the second main portion24ais greatest at the end portion on the side of the engine12and gradually decreases farther away from the engine12until the mid portion in the axial direction.

The second housing portion24bhas a substantially cylindrical shape with one end closed, and has a slightly smaller diameter than the first housing portion23bdescribed above. The inside diameter of the second housing portion24bis substantially the same in any given location. The end portion of the second housing portion24bon the engine side does not extend as far (toward the driven wheel13side) as the end portion of the second main portion24aon the engine side. Also, the end portion of the second housing portion24bon the driven wheel side is in substantially the same position with respect to the axial line L as the end portion of the second main portion24aon the driven wheel side. The end portion of the second housing portion24bis constructed with a second support wall38formed substantially orthogonal with respect to the axial line L at the end portion of the second housing portion24bon the driven wheel side.

Referring toFIG. 6, the third case25has a conical shape in which the diameter (both outside diameter and inside diameter) becomes increasingly smaller farther away from the engine12. The third case25is fastened at an end portion thereof on the engine side to the second case24by a fastening member26such as a bolt.

The drive case21formed of the first through the third cases23through25in this way has an outer shape in that becomes increasingly narrow away from the engine12. This outer shape is similar to the outer shape of a typical automatic transmission provided with a fluid type torque converter and a gear change mechanism, which is housed in a vehicle having a FR type drive system.

Referring back toFIG. 2, a first motor generator (hereinafter referred to as “MG”), a power splitting mechanism portion27, a second motor generator (hereinafter referred to as “MG”) and a speed reducing mechanism portion28are arranged in-line on the axial line L in the drive case21in that order from the side near the engine12to the side away from the engine12(i.e., toward the driven wheels13side). The MG1and the MG2are both constructed of an electric motor, such as an alternating current synchronized motor, that can switch to function as either a generator or an electric motor depending on the conditions. During normal running of the vehicle, however, the MG1mainly serves as a generator that generates electricity by the power from the engine12. Further, the MG2mainly serves as a motor that generates power to assist the engine12. Phrased differently, when the MG2functions as a motor, it provides power that is used to assist the power of the engine12as necessary, and thus serves as an auxiliary power source to the engine12to increase the driving force of the vehicle. Of course, the MG1and MG2may, instead of both being able to function as both a generator and a motor, each have only one of those functions.

Next, the MG1and MG2will be described. Referring toFIG. 4, a first cover29is arranged substantially orthogonal to the axial line L and on the engine12side of the first housing portion23bin the first case23. The first cover29is large enough to close off the open end of the first housing portion23bon the engine side. A first flange29ais formed on the outer edge portion of the first cover29, and this first flange29aof the first cover29overlaps with the end portion of the first housing portion23bon the engine side. Then, a first bolt30which is a first fastening member, of a plurality of bolts (only one bolt is shown inFIG. 4) as first attaching means is inserted from the engine12side through the first flange29aand screwed into the first housing portion23b. In this way, with the first cover29fastened to the first case23, a closed space is formed by the first housing portion23band the first cover29for housing the MG1and the like.

Here, in order to form a through hole for the first bolt30and ensure a predetermined strength, the first flange29amust be of a certain width (i.e., have a certain thickness in the radial direction) w1. Also, in order to tighten and loosen the first bolt30, there must be a certain amount of space between the inside surface of the first flange29aand the inside surface of the first main portion23a. For the sake of convenience in this description, this space or gap will be hereinafter be referred to as “gap g1”. Regarding this, according to this exemplary embodiment, a distance D1between the inside surface of the end portion on the driven wheel side of the first housing portion23band the corresponding inside surface of the first main portion23ais shorter than the sum of the width w1and the gap g1. However, the distance D1between the inside surface of the end portion on the engine side of the first housing portion23band the corresponding inside surface of the first main portion23ais larger than the sum of the width w1and the gap g1. This is because while the inside diameter of the first housing portion23bis substantially constant at any given location, the diameter of the first main portion23abecomes smaller farther away from the engine12. Then, with the first cover29fastened to the first case23, a gap is formed between the inside surface of the first flange29aand the inside surface of the first main portion23a.

The MG1is provided with a first stator32and a first rotor33. The first stator32is arranged near the inside surface of the first housing portion23band is fastened to the first support wall31by a fastening member34such as a bolt. Also, the first rotor33is rotatably supported with respect to both the center portion of the first cover29and the center portion of the first support wall31by a bearing35. Then, the first rotor33rotates by energizing a stator coil36of the first stator32in the MG1 mounted in the first case23, as described above.

As shown inFIGS. 5 and 6, a second cover37is arranged substantially orthogonal to the axial line L and on the engine12side of the second housing portion24bwithin the second case24. This second cover37is large enough to close off the open end of the second housing portion24bon the engine side. On the outer edge portion of the second cover37is formed a second flange37a, which overlaps with the end portion of the second housing portion24bon the engine side. Then, a second bolt40which is a second fastening member, of a plurality of bolts (only one bolt is shown inFIG. 5) as second attaching means is inserted through the second flange37afrom the engine12side and screwed into the second housing portion24b. In this way, with the second cover37fastened to the second case24, a closed space is formed for housing the MG2and the like by the second housing portion24band the second cover37.

Here, in order to form a through hole for the second bolt40and ensure a predetermined strength, the second flange37amust be of a certain width (i.e., have a certain thickness in the radial direction) w2. Also, in order to tighten and loosen the second bolt40, there must be a certain amount of space between the inside surface of the second flange37aand the inside surface of the second main portion24a. For the sake of convenience in this description, this space or gap will be hereinafter be referred to as “gap g2”. Regarding this, according to this exemplary embodiment, a distance D2between the inside surface of the end portion on the driven wheel side of the second housing portion24band the corresponding inside surface of the second main portion24ais smaller than the sum of the width w2and the gap g2. However, the distance D2between the inside surface of the second housing portion24bof the end portion on the engine side and the corresponding inside surface of the second main portion24ais larger than the sum of the width w2and the gap g2. This is because while the inside diameter of the second housing portion24bis substantially constant at any given location, the diameter of the second main portion24abecomes increasingly smaller away from the engine12. Then, with the second cover37fastened to the second case24, a gap is formed between the inside surface of the second flange37aand the inside surface of the second main portion24a.

The MG2is provided with a second stator39and a second rotor41. The second stator39has a slightly smaller outside diameter, and is longer, than the first stator32of the MG1. The second stator39is arranged near the inside surface of the second housing portion24band is fastened to the second support wall38by a fastening member42such as a bolt. Also, the second rotor41has a slightly smaller outside diameter, and is longer, than the first rotor33of the MG1. The second rotor41is rotatably supported with respect to both the center portion of the second cover37and the center portion of the second support wall38by a bearing43. Then, the second rotor41rotates by energizing a stator coil44of the second stator39in the MG2mounted in the second case24, as described above.

As shown inFIG. 2, an input shaft45is inserted through the center portion of first cover29, the first rotor33, and the first support wall31so as to be rotatable relative to each of these. This input shaft45is coupled via a transmission damper46to a crankshaft47which serves as the output shaft of the engine12. Similarly, a middle shaft48is inserted through the axial center portion of the second cover37, the second rotor41, and the second support wall38so as to be rotatable relative to each of these. Meanwhile, an output shaft49that has a larger diameter than the input shaft45and the middle shaft48is inserted into the third case25. This output shaft49is rotatably supported in the third case25by a bearing51and the like. The output shaft49is linked to the driven wheels13via the propeller shaft15, the differential16, and the axle shafts17, and the like. The middle shaft48is coupled to the output shaft49directly, to be described later.

The power splitting mechanism portion27is a mechanism for appropriately splitting the power from the engine12into vehicle driving force for directly driving the driven wheels13and generator driving force for operating the MG1to generate electricity. The power splitting mechanism portion27is disposed in the core case22, in a space between the MG1and the MG2. As shown inFIG. 5, the power splitting mechanism portion27includes a planetary gear set in which a sun gear52, a ring gear53, and a planetary carrier54having the same axial center are rotatably interlocked together. The sun gear52is interlocked, so as to be able to integrally rotate, with the first rotor33of the MG1on the input shaft45. The ring gear53has a smaller diameter than the outside diameter of the first stator32of the MG1and second stator39of the MG2, and is mounted to the end portion on the engine12side of the middle shaft48. The planetary carrier54is attached so as to be able to integrally rotate with the input shaft45. A pinion gear55is rotatably supported by the planetary carrier54. The pinion gear55is positioned between the sun gear52and the ring gear53and is rotatably meshed with both of the sun gear52and the ring gear53.

Then, with the power splitting mechanism portion27constructed in this way, power generated by the engine12and transmitted to the input shaft45is then transmitted to the first rotor33of the MG1via the planetary carrier54, the pinion gear55, and the sun gear52. Further, the power transmitted to the input shaft45is then transmitted to the ring gear53(i.e., the middle shaft48) via the planetary carrier54and the pinion gear55.

In the power splitting mechanism portion27described above, the outside diameter of the ring gear53is smaller than the outside diameter of the MG1and the MG2. Therefore, a space S1and a space S2of a predetermined size are created between the MG1and the MG2in the core case22, toward the outside in the radial direction of the ring gear53of the power splitting mechanism portion27.

As shown inFIG. 6, the speed reducing mechanism portion28includes a planetary gear set in which a sun gear56, a ring gear57, and a planetary carrier58having the same axial center are rotatably interlocked together, which is similar to the power splitting mechanism portion27. The entire structure is then arranged within the third case25. The sun gear56is interlocked so as to be able to integrally rotate with the second rotor41of the MG2. The ring gear57is interlocked so as to be able to integrally rotate with the middle shaft48and the output shaft49. The planetary carrier58is fixed to the second support wall38of the second case24. On the planetary carrier58, a pinion gear59is rotatably supported. This pinion gear59is positioned between, and is meshed so as to be able to rotate (freely) with, the sun gear56and the ring gear57. Then, with the speed reducing mechanism portion28constructed in this way, rotation of the second rotor41of the MG2is transmitted to the output shaft49via the sun gear56, the pinion gear59, and the ring gear57. Speed reduction is accomplished by this transmission process. The rotation with increased torque due to this speed reduction is applied to the output shaft49to assist the driving force of the engine12.

As shown inFIG. 2, the MG1and the MG2are both connected to a high voltage battery62via an inverter61. The inverter61and the high voltage battery62are disposed farther to the rear in the forward-backward direction of the vehicle than the drive apparatus14. The inverter61is an apparatus that controls the current while converting the high voltage direct current from the high voltage battery62to alternating current for the MG1and the MG2.

A first cable63is used to electrically connect the MG1to the inverter61. Further, a second cable64is used to electrically connect the MG2to the inverter61. For the first cable63and the second cable64, a cable capable of withstanding high voltage is used. Further, the space S1in the core case22is used to connect the first cable63with the MG1and the second cable64with the MG2.

More specifically, as shown inFIG. 5, a first connecting portion65is provided on the first support wall31. Here, this first connecting portion65is formed with a protruding portion that protrudes from an upper portion of the first support wall31toward the MG2side. Then, the stator coil36of the MG1and a first connecting terminal68of the first cable63are electrically connected at the first connecting portion65. Similarly, a second connecting portion66is provided on the second cover37. Here, this second connecting portion66is formed with a protruding portion that protrudes from an upper portion of the second cover37toward the MG1side. Then, the stator coil44of the MG2and a second connecting terminal71of the second cable64are electrically connected at the second connecting portion66.

As shown inFIGS. 3 and 5, a first outlet67is mounted to the core case22on the driven wheels13side of the MG1. Then, the first connecting terminal68is fed through the first outlet67and led out of the core case22. Also, a second outlet69, similar to the first outlet67, is mounted to the core case22on the driven wheels13side of the first outlet67. Then, the second connecting terminal71is fed through the second outlet69and led out of the core case22. The first outlet67and the second outlet69are formed curved away from the engine12and parallel to each other.

Further, as shown inFIG. 2, an oil pump72is provided to supply oil to sliding parts, e.g., between the input shaft45and the first rotor33, and between the middle shaft48and the second rotor41, and the like, in the drive case21. From among the spaces between the MG1and the MG2in the core case22, this oil pump72is provided in the space S2below the power splitting mechanism portion27, and is attached to the lower portion of the second cover37. Also, an oil sump73is provided on the lower portion of the second case24, and an oil strainer74that filters oil drawn in from the oil pump72is disposed within this oil sump73.

The drive apparatus14of the construction described above operates as described below, for example, according to the running conditions of the hybrid vehicle11.

<During Take off and Low Speed Running>

In a region where the rotation of the driven wheels13is slow and there is a high load on the engine, such that the engine efficiently is low, such as during take off and when running at low speeds, the engine12stops operating and power is supplied to the MG2from the high voltage battery62. The second rotor41of the MG2rotates and that rotation is transmitted to the output shaft49via the sun gear56, the pinion gear59, and the ring gear57of the speed reducing mechanism portion28. The rotation of the output shaft49is then transmitted to the driven wheels13through the propeller shaft15and the like. In this way, the driven wheels13are driven by only the power from the MG1. At this time, the first rotor33in the MG1is idling.

During normal running, the engine12is operated and power therefrom is transmitted to the driven wheels13after being split into two paths by the power splitting mechanism portion27. One of the paths transmits the power input to the input shaft45to the pinion gear55and the ring gear53. The power transmitted along this path is transmitted to the output shaft49via the middle shaft48. The other path transmits power to the generator to drive it so as to generate electricity. More specifically, this path transmits the power input to the input shaft45to the first rotor33of the MG1via the pinion gear55and the sun gear52. The first rotor33is rotated and power is generated by the MG1by this power transmission. The generated electric power is supplied to the MG2, which is then used as an auxiliary power source to the engine12. That is, the second rotor41of the MG2is rotated and that rotation is then transmitted to the output shaft49after being decelerated by the speed reducing mechanism portion28. Then, the driven wheels13are driven by the power transmitted through both of these paths and ultimately output from the output shaft49.

Operation when running under a high load is the same as during normal running except that electric power is also supplied to the MG2by the high voltage battery62. As a result, the assist power provided by the MG2is further increased.

When decelerating and braking, the MG2is driven by rotation of the driven wheels13. In this case, the MG2functions as a generator, regenerating electricity. Kinetic energy from decelerating the vehicle is converted into electrical energy and recovered (i.e., stored) in the high voltage battery62.

The following effects are obtained from the exemplary embodiment described in detail above.

(1) In the drive apparatus14, the MG1, the power splitting mechanism portion27, the MG2, and the speed reducing mechanism portion28are arranged in-line in that order from the side near the engine12to the side away from the engine12. Furthermore, the outside diameter of the MG2is made smaller than the outside diameter of the MG1, the outside diameter of the power splitting mechanism portion27is made smaller than the outside diameter of the MG1and the MG2, and the outside diameter of the speed reducing mechanism portion28is made smaller than the outside diameter of the MG2. As a result, the outside diameter of the drive apparatus14becomes increasingly smaller away from the engine12. Also, the drive apparatus14has a conical shape and is compact. In this way, according to this exemplary embodiment, the speed reducing mechanism portion28is able to be incorporated into the drive apparatus14while the apparatus on the whole is able to be made compact.

Furthermore, the mountability in the hybrid vehicle11of this drive apparatus14that has been made compact in this way is excellent. In particular, the foregoing shape is substantially the same as the shape of a typical automatic transmission with a fluid type torque converter and a gear change mechanism, which is mounted in a conventional vehicle having an FR type drive system. Therefore, by designing the drive apparatus14so it that is substantially the same size as the automatic transmission, the drive apparatus14is able to be housed in the floor tunnel19that already exists in vehicles for housing an automatic transmission. Therefore, it is possible to arrange the drive apparatus14, instead of the automatic transmission, in this floor tunnel19. Phrased differently, the automatic transmission, as well as the drive apparatus14, are able to be housed in an identical floor18that includes the floor tunnel19, so the same floor18can be used. Therefore, it is not necessary to newly design a floor tunnel to house the drive apparatus14in addition to the existing floor tunnel that houses the automatic transmission.

(2) When expanding the use of the drive apparatus14to a wide variety of hybrid vehicles11, if the specifications, such as those of the gear ratio of the speed reducing mechanism portion28, can be conformed to the vehicle, the MG1, the MG2, and the power splitting mechanism portion27and the like can be used as they are as common parts. Here, the third case25in which the speed reducing mechanism portion28is mounted is independent from the core case22in which the MG1, the MG2, and the power splitting mechanism portion27are mounted. These cases22and25can be joined to, and separated from, one another. As a result, by preparing a unit part in which the speed reducing mechanism portion28is mounted in the third case25for each type of hybrid vehicle11, there only needs to be one type of unit (core unit) in which the MG1, the MG2, and the power splitting mechanism portion27are mounted in the core case22, regardless of the type of the hybrid vehicle11. Then, when assembling a plurality of kinds of the drive apparatuses14in an assembly plant or the like, the unit part in which the particular speed reducing mechanism portion28that matches the type of drive apparatus14is simply selected and attached to the common core unit. As a result, the work of changing to a different speed reducing mechanism portion28with a different gear ratio becomes easier.

(3) Because the power splitting mechanism portion27includes a planetary gear set, and the ring gear53, which determines the overall size of that gear set, has a smaller outside diameter than the MG1and the MG2, the space S1and the space S2are created toward the outside in the radial direction of the ring gear53between the MG1and the MG2. Of these spaces, the space S1is used as a space in which to house the first connecting portion65for electrically connecting the first cable63to the stator coil36of the MG1. In addition, the space S1is also used as a space to house the second connecting portion66for electrically connecting the second cable64to the stator coil44of the MG1. By having both the first connecting portion65and the second connecting portion66in the space S1between the MG1and the MG2in this way, space can be used efficiently. Further, the space S2is used to house the oil pump72, so space is used efficiently as well. Therefore, by using these spaces S1and S2, the connecting portions65and66and the oil pump72can be housed without losing the compactness of the drive apparatus14.

(4) The first connecting terminal68which is connected to the stator coil36of the MG1is led out of the drive case21through the first outlet67. The second connecting terminal71which is connected to the MG2is also led out of the drive case21through the second outlet69. Here, the first outlet67and the second outlet69are both provided in the drive case21which becomes increasingly narrow away from the engine12. Also, the second outlet69is positioned on the side of the first outlet67opposite the engine12, i.e., in a location having a smaller outside diameter than the first outlet67in the drive case21. In addition, both the first outlet67and the second outlet69are curved away from the engine12and parallel to each other. As a result, in this exemplary embodiment in which the inverter61, which is the connection mate of both of the cables63and64, is arranged behind the drive apparatus14in the forward-backward direction of the vehicle, both the cables63and64can be led out of the drive case21together without interfering with one another and laid toward the inverter61.

(5) It is also conceivable to provide a transmitting mechanism on the outside of the MG2for transmitting rotation of the ring gear53of the power splitting mechanism portion27to the output shaft49. In this case, for example, a shaft other than the input shaft45and the output shaft49is provided parallel to these shafts, and a rotation transmitting part such as a gear or the like is provided on each shaft. The shaft in this case corresponds to a counter shaft used in a manual transmission. As a result, rotation from the input shaft45is able to be transmitted to the output shaft49via the shaft (i.e., counter shaft), the gears or the like. On the other hand, because gears are used, there is a drawback of noise and vibration being generated when the gears mesh.

In contrast, according to this exemplary embodiment, the middle shaft48for transmitting rotation of the ring gear53to the output shaft49is integrally provided with the ring gear53. Then this middle shaft48is inserted through the second rotor41of the MG2and coupled to the ring gear57of the output shaft49. This obviates the need for the aforementioned counter shaft. Because noise and vibration resulting from the meshing of gears is not generated, the noise and vibration characteristics are improved.

(6) The torque after speed reduction by the speed reducing mechanism portion28is larger than before speed reduction. Therefore, the parts that transmit the increased torque must be very strong. According to this exemplary embodiment, the output shaft49is larger in diameter than the input shaft45and the middle shaft48in order to meet this requirement.

Here, if the speed reducing mechanism portion28was arranged on the engine12side of the MG2, the output shaft49, which is large in diameter, would be inserted through the MG2, thus requiring that the diameter of the MG2be larger, which would increase the overall size of the drive apparatus14. In contrast, according to this exemplary embodiment, the speed reducing mechanism portion28is arranged on the driven wheels13side of the MG2, as described above. As a result, the shaft (i.e., the middle shaft48) that is inserted through the MG2does not have to be of a large diameter, so an increase in size of the MG2and the drive apparatus14is able to be avoided.

(7) Because the outside diameter of the MG2is smaller than the outside diameter of the MG1, a space is created beneath the MG2. The oil sump73is incorporated into this space. As a result, an increase in size of the drive apparatus14due to the incorporation of the oil sump73is able to be kept to a minimum. In other words, the oil sump73is able to be provided without sacrificing the mountability of the drive apparatus14.

(8) The first support wall31and the first cover29of the first case23rotatably support the first rotor33, as well as form a closed space for housing the MG1and the like. Also, the second support wall38and the second cover37of the second case24rotatably support the second rotor41, as well as form a closed space for housing the MG2and the like. It is therefore possible to suppress foreign matter from getting into the first housing portion23band the second housing portion24band causing poor operation with respect to rotation and the like of the first rotor33and the second rotor41. As a result, the MG1and the MG2are able to maintain their functions as a motor or generator well, and are thus able to be highly reliable.

(9) The first cover29is arranged on the engine12side (i.e., on the end portion on the engine side of the first housing portion23b) of the MG1inside the first main portion23a. The diameter of the first main portion23ain this location is comparatively larger than the general outside diameter around the first main portion23a. In particular, the diameter of the first main portion23ain this location is definitely larger than the diameter of the first main portion23aat a location corresponding to the end portion on the driven wheel side of the first housing portion23b. The size relationship of the distance D1between the inside surface of the first housing portion23band the inside surface of the first main portion23ais the same as described above. Therefore, because the distance D1is larger than the sum of the width w1of the first flange29aand the gap g1between first flange29aand the first main portion23a, even if the first main portion23adoes not extend outward in the radial direction, the first cover29can still be arranged within the first main portion23aand fastened to the first housing portion23bby the first bolt30.

In this way, it is possible to suppress the outside diameter of the first case23from becoming larger with the first cover29attached, and therefore maintain the original outer shape of the drive case21, in which it becomes increasingly narrow away from the engine12. This outer shape is similar to the outer shape of an automatic transmission provided with a torque converter and a gear change mechanism, which is housed in a vehicle having a FR type drive system. As a result, it is possible to arrange the drive apparatus14, instead of the automatic transmission, in the floor tunnel19, and improve mountability of the drive apparatus14in the vehicle.

(10) The diameter of the first main portion23aincreases closer to the engine12. Therefore, even in the first main portion23a, a sufficiently wide space is created around the first cover29, and particularly around the first flange29a, arranged near the engine12. This space facilitates the operation of loosening and tightening the first bolt30when detaching and attaching the first cover29.

(11) The second cover37is arranged on the engine12side (i.e., on the end portion on the engine side of the second housing portion24b) of the MG2within the second main portion24a. The diameter of the second main portion24ain this location is comparatively larger than the general outside diameter around the second main portion24a. In particular, the diameter of the second main portion24ain this location is definitely larger than the diameter of the second main portion24aat a location corresponding to the end portion on the driven wheel side of the second housing portion24b. The size relationship of the distance D2between the inside surface of the second housing portion24band the inside surface of the second main portion24ais the same as described above. Therefore, because the distance D2is larger than the sum of the width w2of the second flange37aand the gap g2between second flange37aand the second main portion24a, even if the second main portion24adoes not extend outward in the radial direction, the second cover37can be arranged within the second main portion24aand fastened to the second housing portion24bby the second bolt40. In this way, it is possible to suppress the outside diameter of the second case24from becoming larger with the second cover37attached, and therefore maintain the original outer shape of the drive case21, in which it becomes increasingly narrow away from the engine12. Accordingly, together with the effect of (2) above, mountability of the drive apparatus14in the vehicle is further improved.

(12) The diameter of the second main portion24aincreases closer to the engine12. Therefore, even in the second main portion24a, a sufficiently wide space is created around the second cover37, and particularly around the second flange37a,arranged near the engine12. This space facilitates the operation of loosening and tightening the second bolt40when detaching and attaching the second cover37.

This invention can be implemented with other exemplary embodiments described as follows.The MG1and the MG2may each also be able to perform both a regenerative operation and a powering operation, or either one of the two. Accordingly, a VR type (variable reluctance type) synchronous motor, a vernier motor, a direct current motor, an induction motor, a superconducting motor, a step motor, or the like may also be used instead of an alternating current synchronous motor of the type used in the foregoing exemplary embodiment.The drive apparatus according to the invention is not limited to a FR type driving system, but may also be applied to a hybrid vehicle having another type of driving system such as a front engine front drive (FF) driving system.In the foregoing exemplary embodiment, the planetary carrier58of the speed reducing mechanism portion28is fixed. Alternatively, however, the ring gear57may be fixed to the third case25or the like.The second flange37amay be formed over the entire circumference of the outer edge portion of the second cover37, or only on a portion thereof.

The technical ideas that can be understood from these exemplary embodiments, as well as their effects, shall now be described.

(A) In the drive apparatus for a hybrid vehicle, the power splitting mechanism portion includes the planetary gear set which has a ring gear with an outer diameter smaller than the motor generator and which is arranged between the motor generators. The oil pump to supply oil to sliding parts is provided in a space that is outward in the radial direction from the ring gear between the motor generators.

According to the foregoing construction, the oil pump is able to be incorporated without losing the compactness of the drive apparatus by efficiently using the space between the two motor generators.

(B) In the drive apparatus for a hybrid vehicle according to aforementioned (A), the oil sump is further provided beneath the second motor generator.

According to this construction, an increase in size of the drive apparatus due to the arrangement of the oil sump is able to be kept to a minimum.

(C) In the drive apparatus for a hybrid vehicle, the first fastening member includes a first bolt that is inserted through the first flange and screwed into the first housing portion.

(D) In the drive apparatus for a hybrid vehicle, the first fastening member includes a first bolt that is inserted through the first flange and screwed into the first housing means.

According to (C) and (D), the first cover can be reliably fastened to the end portion on the engine side of the first housing portion by the first bolt.

(E) In the drive apparatus for a hybrid vehicle, the second fastening member includes the second bolt that is inserted through the second flange and screwed into the second housing portion.

(F) In the drive apparatus for a hybrid vehicle according, the second fastening member includes the second bolt that is inserted through the second flange and screwed into the second housing means.

According to (E) and (F), the second cover can be reliably fastened to the end portion on the engine side of the second housing portion by the second bolt.

(G) In the drive apparatus for a hybrid vehicle according aforementioned (C) to (F), the first housing portion has a cylindrical shape and is provided with a support wall on the end portion on the side opposite the engine. That support wall is on the side of the motor generator opposite the engine and closes off that end portion.

According to this construction, the support wall and the first cover close off both end portions of the first housing portion so as to suppress foreign matter from getting into the first housing portion and causing poor operation of the first motor generator.

(H) In the drive apparatus for a hybrid vehicle according the aforementioned (D) or (F), the second housing portion has a cylindrical shape and is provided with second support wall on the end portion on the side opposite the engine. That second support wall is on the side of the second motor generator opposite the engine and closes off that end portion.

According to this construction, the second support wall and the second cover close off both end portions of the second housing portion so as to suppress foreign matter from getting into the second housing portion and causing poor operation of the second motor generator.