The present invention relates to a power transmission device for a front and rear wheel drive vehicle having an electric type differential portion, and, more particularly, to a technique for improving fuel economy during high-speed traveling and power performance during acceleration traveling.
It is suggested a power transmission device for a front and rear wheel drive vehicle including: (a) an electric type differential portion having a differential state between a rotation speed of a differential input member and a rotation speed of a differential output member controlled by controlling an operational sate of a first rotating machine coupled to a rotating element of a differential mechanism in a power transmittable manner; (b) a second rotating machine disposed for at least one of front and rear wheels in a power transmittable manner; and (c) a front and rear wheel power distribution device having three rotating elements that are an input rotating element, a first output rotating element operatively coupled to a first wheel that is one of the front and rear wheels, and a second output rotating element operatively coupled to a second wheel that is the other of the front and rear wheels, the front and rear wheel power distribution device distributing power to the first output rotating element and the second output rotating element, the power being input from the differential output member to the input rotation element. (See Patent Document 1)
One example is a power transmission device 100 of a hybrid vehicle having a general configuration (schematic) depicted in
As depicted in a collinear diagram of
However, such a conventional power transmission device still has room for improvement because energy circulation occurs during high-speed traveling, resulting in deterioration of energy efficiency (such as fuel economy) and a rotation speed of a differential input member is limited during acceleration traveling, resulting in restriction of the power performance, etc. Specifically describing in terms of the power transmission device 100 of
On the other hand, although not known yet, it is contemplated that an automatic transmission 122 is disposed on the rear wheel side of the power transmission device 100 as in a power transmission device 120 depicted in
The present invention was conceived in view of the situations and it is therefore an object of the present invention to allow a power transmission device for a front and rear wheel drive vehicle having an electric type differential portion to restrict the energy circulation during high-speed traveling for further improvement in energy efficiency or to further alleviate the restriction on the rotation speed of the differential input member during acceleration traveling, thereby acquiring excellent power performance.
The object indicated above can be achieved according to a first aspect of the present invention, which provides a power transmission device for a front and rear wheel drive vehicle including: (a) an electric type differential portion having a differential state between a rotation speed of a differential input member and a rotation speed of a differential output member controlled by controlling an operational sate of a first rotating machine coupled to a rotating element of a differential mechanism in a power transmittable manner; (b) a second rotating machine disposed for at least one of front and rear wheels in a power transmittable manner; and (c) a front and rear wheel power distribution device having three rotating elements that are an input rotating element, a first output rotating element operatively coupled to a first wheel that is one of the front and rear wheels, and a second output rotating element operatively coupled to a second wheel that is the other of the front and rear wheels, the front and rear wheel power distribution device distributing power to the first output rotating element and the second output rotating element, the power being input from the differential output member to the input rotation element, (d) the front and rear wheel power distribution device being configured such that the input rotating element, the first output rotating element, and the second output rotating element are arranged in series from one end to the other end on a collinear diagram capable of representing rotation speeds of the three rotating elements on a straight line, (e) a gear ratio from the first output rotating element to the first wheel being different from a gear ratio from the second output rotating element to the second wheel.
The object indicated above can be achieved according to a second aspect of the present invention, which provides the power transmission device for a front and rear wheel drive vehicle of the first aspect of the invention, wherein the gear ratio from the first output rotating element to the first wheel is smaller than the gear ratio from the second output rotating element to the second wheel.
The object indicated above can be achieved according to a third aspect of the present invention, which provides the power transmission device for a front and rear wheel drive vehicle of the first aspect of the invention, wherein the gear ratio from the first output rotating element to the first wheel is greater than the gear ratio from the second output rotating element to the second wheel.
The object indicated above can be achieved according to a fourth aspect of the present invention, which provides the power transmission device for a front and rear wheel drive vehicle of any one of the first to third aspects of the present invention, including a shifting portion on a power transmission path from the first output rotating element to the first wheel, the shifting portion having a gear ratio selectable from a speed-decreasing gear ratio larger than one to a speed-increasing gear ratio smaller than one, wherein the gear ratio from the first output rotating element to the first wheel is made smaller than the gear ratio from the second output rotating element to the second wheel by selecting the speed-increasing gear ratio during high-speed traveling, and wherein the gear ratio from the first output rotating element to the first wheel is made greater than the gear ratio from the second output rotating element to the second wheel by selecting the speed-decreasing gear ratio during acceleration traveling.
The object indicated above can be achieved according to a fifth aspect of the present invention, which provides the power transmission device for a front and rear wheel drive vehicle of the second or fourth aspect of the invention, comprising a high-speed traveling differential control means that performs power running control to rotationally drive the first rotating machine depending on the rotation speed of the differential output member such that the rotation speed of the differential input member is maintained at a predetermined value during acceleration traveling while performing regenerative control of the second rotating machine to recover electric energy.
The object indicated above can be achieved according to a fifth aspect of the present invention, which provides the power transmission device for a front and rear wheel drive vehicle of the third or fourth aspect of the invention, including an acceleration traveling differential control means that performs regenerative control of the first rotating machine during acceleration traveling to recover electric energy while limiting the rotation speed of the first rotating machine during the regenerative control in accordance with a predetermined regenerative condition.
This power transmission device of a front and rear wheel drive vehicle is configured such that an input rotation element, a first output rotation element, and a second output rotation element are arranged in series from one end to the other end on a collinear diagram capable of representing the rotation speeds of the three rotation elements of the front and rear wheel power distribution device on a straight line. Therefore, if the gear ratio from the first output rotation element to the first wheel is different from the gear ratio from the second output rotation element to the second wheel due to the presence/absence of the automatic transmission and a difference between the final reduction ratios of the first and second wheels, the rotation speed of the input rotation element located at the end of the collinear diagram among the three rotation elements is maximized or minimized. Therefore, if the gear ratios are determined such that the rotation speed of the input rotation element is reduced during high-sped traveling, specifically, if the gear ratio on the first wheel side is set smaller than the gear ratio on the second wheel side, a change in the rotation is suppressed in the power running rotation direction of the first rotating machine coupled to the electric type differential portion correspondingly to the reduction of the rotation speed of the input rotation element. Therefore, the energy circulation becomes difficult to occur or the rotation speed in the power running rotation direction is lowered and an energy loss due to the energy circulation is reduced, and the energy efficiency is improved. If the gear ratios are determined such that the rotation speed of the input rotation element is increased during acceleration traveling at startup, etc., specifically, if the gear ratio on the first wheel side is set greater than the gear ratio on the second wheel side, the rotation speed of the differential input member is allowed to increase correspondingly to the increase in the rotation speed of the input rotation element and, therefore, the rotation speed of the drive power source such as the engine coupled to the differential input member can be increased to improve the power performance (power).
In the second aspect of the invention, the gear ratio from the first output rotating element to the first wheel is smaller than the gear ratio from the second output rotating element to the second wheel, the rotation speed of the input rotation element, and, further, the rotation speed of the differential output member of the electric type differential portion are reduced. Therefore, for instance, in the case of the fifth aspect of the invention in which a high-speed traveling differential control means performs power running control to rotationally drive the first rotating machine depending on the rotation speed of the differential output member such that the rotation speed of the differential input member is maintained at a predetermined value during acceleration traveling while performing regenerative control of the second rotating machine to recover electric energy, a change in the rotation is suppressed in the power running rotation direction of the first rotating machine coupled to the electric type differential portion correspondingly to the reduction of the rotation speed of the differential output member. Therefore, the energy circulation becomes difficult to occur or an energy loss due to the energy circulation is reduced, and the energy efficiency is improved. Even if the high-speed traveling differential control means of the fifth aspect of the invention is not included and the first rotating machine is always subjected to the regenerative control without changing the rotation in the power running rotation direction while traveling, the vehicle speed can be increased while suppressing increase in the rotation of the differential input member correspondingly to the reduction of the rotation speed of the differential output member, and the maximum vehicle speed can be raised while avoiding the deterioration of the energy efficiency due to the energy circulation.
In the third aspect of the invention, the gear ratio from the first output rotating element to the first wheel is greater than the gear ratio from the second output rotating element to the second wheel, the rotation speed of the input rotation element, and, further, the rotation speed of the differential output member of the electric type differential portion are increased. Therefore, for instance, in the case of the sixth aspect of the invention in which an acceleration traveling differential control means performs regenerative control of the first rotating machine during acceleration traveling to recover electric energy while limiting the rotation speed of the first rotating machine during the regenerative control in accordance with a predetermined regenerative condition, the restriction on increase in the rotation speed of the differential input member due to the rotation speed limitation of the first rotating machine is alleviated correspondingly to the increase of the rotation speed of the differential output member and the rotation speed of the drive power source such as the engine coupled to the differential input member can be increased to acquire excellent power performance. Even if the acceleration traveling differential control means of the sixth aspect of the invention is not included and the rotation speed of the first rotating machine is not limited at the time of the regenerative control thereof, the rotation speed of the differential input member is allowed to increase correspondingly to the increase in the rotation speed of the differential output member and, therefore, the rotation speed of the drive power source such as the engine coupled to the differential input member can be increased to improve the power performance.
In the fourth aspect of the invention, the power transmission device for a front and rear wheel drive vehicle includes a shifting portion on a power transmission path from the first output rotating element to the first wheel, the shifting portion having a gear ratio selectable from a speed-decreasing gear ratio larger than one to a speed-increasing gear ratio smaller than one, wherein the gear ratio from the first output rotating element to the first wheel is made smaller than the gear ratio from the second output rotating element to the second wheel by selecting the speed-increasing gear ratio during high-speed traveling, and wherein the gear ratio from the first output rotating element to the first wheel is made greater than the gear ratio from the second output rotating element to the second wheel by selecting the speed-decreasing gear ratio during acceleration traveling, during the high-speed traveling, as well as in the second aspect of the invention, a change in the rotation is suppressed in the power running rotation direction of the first rotating machine correspondingly to the reduction of the rotation speed of the differential output member, and, therefore, the energy efficiency is improved, while, during the acceleration traveling, as well as in the third aspect of the invention, the increase in the rotation speed of the differential input member correspondingly to the increase of the rotation speed of the differential output member is allowed and the rotation speed of the drive power source such as the engine coupled to the differential input member can be increased to acquire excellent power performance.
10, 200, 202: power transmission device 12, 250: electric type differential portion 14, 210, 220, 230, 240: front and rear wheel power distribution device 16: differential planetary gear device (differential mechanism) 18: differential input shaft (differential input member) 22: differential output member 30: automatic transmission (shifting portion) 34: real wheels (first wheels) 44: front wheels (second wheels) 80: electronic control device 92: high-speed traveling differential control means 94: acceleration traveling differential control means MG1: first motor generator (first rotating machine) MG2: second motor generator (second rotating machine)
Although the present invention is preferably applied to a hybrid front and rear wheel drive vehicle having a differential input member of an electric type differential portion to which an internal combustion engine such as a gasoline engine or a diesel engine is coupled as a main drive force source, the main drive force source may be employed as a drive force source other than an internal combustion engine, such as an electric motor or a motor generator.
Although the electric type differential portion includes, for example, a single pinion or double pinion type single planetary gear device as a differential mechanism, various forms are available such as a configuration using a plurality of planetary gear devices or using a bevel gear type differential device. Although this electric type differential portion is configured such that the rotating element coupled to the differential input member is located in the middle on a collinear diagram capable of representing with a straight line the rotation speeds of three rotating elements of the differential mechanism coupled respectively to, for example, the first rotating machine, the differential input member, and the differential output member, the present invention is also applicable to the configuration with the rotating element coupled to the differential output member located in the middle.
The form of control is differentiated in the high-speed traveling differential control means and the acceleration traveling differential control means depending on the coupling form of the electric type differential portion. If the rotating element coupled to the differential input member is configured to be located in the middle on the collinear diagram, the high-speed traveling differential control means performs the power running control to rotate the first rotating machine in a rotation direction opposite to the differential output member depending on the rotation speed of the differential output member, and the acceleration traveling differential control means performs the regenerative control of the first rotating machine to recover electric energy when the first rotating machine is rotationally driven in the same rotation direction as the differential input member. If the rotating element coupled to the differential output member is configured to be located in the middle, the high-speed traveling differential control means performs the power running control to rotate the first rotating machine in the same rotation direction as the differential output member depending on the rotation speed of the differential output member, and the acceleration traveling differential control means performs the regenerative control of the first rotating machine to recover electric energy when the first rotating machine is rotationally driven in the rotation direction opposite to the differential input member.
Although the rotating machines of the first rotating machine and the second rotating machine are rotating electric machines and may preferably be implemented by using motor generators capable of selectively acquire functions of an electric motor and an electric generator, an electric motor or an electric generator may be used depending on the form of the differential control and, for example, an electric generator can be employed as the first rotating machine if the differential control is performed to recover electric energy through the regenerative control of the first rotating machine during acceleration traveling and to limit the rotation speed of the first rotating machine during the regenerative control in accordance with a predetermined regenerative condition as in the sixth aspect of the present invention. The first rotating machine or the second rotating machine can be made up by using both an electric motor and an electric generator.
Although the second rotating machine may be integrally coupled to the power transmission path to the front and rear wheels, various forms may be available such as coupling via an interrupting device such as a clutch or coupling via a transmission that increases or decreases speed. The second rotating machine can be disposed for both the front and rear wheels or can be disposed for both the left and right wheels. The second rotating machine may be coupled at least to the front wheels or the rear wheels in a power transmittable manner and may not necessarily be coupled to the power transmission path from the front and rear wheel power distribution device to the front and rear wheels.
Although the front and rear wheel power distribution device includes, for example, a single pinion or double pinion type single planetary gear device as a differential mechanism as is the case with the electric type differential portion, various forms are available such as a configuration using a plurality of planetary gear devices or using a bevel gear type differential device. If the differential mechanism is a single pinion type planetary gear device, the carrier located in the middle on the collinear diagram is the first output rotating element, and the sun gear and the ring gear correspond to one and the other of the input rotating element and the second output rotating element. If the differential mechanism is a double pinion type planetary gear device, the ring gear located in the middle on the collinear diagram is the first output rotating element, and the sun gear and the carrier correspond to one and the other of the input rotating element and the second output rotating element.
Although the input rotating element and the differential output member of the front and rear wheel power distribution device may integrally be coupled, various forms may be available such as coupling via an interrupting device such as a clutch or coupling via a transmission that increases or decreases speed. The first output rotating element and the second output rotating element may be coupled at least to one or the other of the front and rear wheels regardless of which element is on the front wheel side or the rear wheel side.
Although the shifting portion is disposed on the power transmission path from the first output rotating element to the first wheel in the fourth aspect of the present invention, the shifting portion may be disposed on the power transmission path from the second output rotating element to the second wheel or may be disposed on both of the paths. The shifting portion may be a stepped transmission such as a planetary gear type or a parallel shaft type and may be a stepless (continuously variable) transmission such as a belt type. In the implementation of the second and third aspects of the present invention, such shifting portion is not necessarily needed and different gear ratios can be achieved, for example, by changing the final reduction ratio (differential ratio) of the front-side left and right wheel power distribution device or the rear-side left and right wheel power distribution device. The shifting portion may not necessarily have gear ratios selectable from the speed-decreasing gear ratio greater than one to the speed-increasing gear ratio smaller than one, and only the speed-decreasing gear ratios or the speed-increasing gear ratios may be selectable.
Although the second rotating machine is disposed on the power transmission path between, for example, the first output rotating element and the shifting portion in a power transmittable manner if the shifting portion is disposed on the power transmission path from the first output rotating element to the first wheel as in the fourth aspect of the present invention, the second rotating machine can be disposed on the power transmission path between the shifting portion and the first wheel or can be disposed on the power transmission path on the second wheel side.
Although the first to fourth aspects of the present invention are preferably applied when including the high-speed traveling differential control means of the fifth aspect of the present invention, which performs the differential control causing energy circulation or the acceleration traveling differential control means of the sixth aspect of the present invention, which limits the rotation speed during the regenerative control of the first rotating machine, the first to fourth aspects are applicable if the high-speed traveling differential control means or the acceleration traveling differential control means is not included. Even in such a case, the effects can be acquired such that when the gear ratio on the first wheel side is made smaller than that on the second wheel side and the rotation speed of the differential output member is reduced, the maximum vehicle speed can be increased while avoiding the deterioration of energy efficiency due to energy circulation and that when the gear ratio on the first wheel side is made greater than that on the second wheel side and the rotation speed of the differential output member is increased, the rotation speed of the drive force source such as an engine coupled to the differential input member can be increased to improve the power performance during acceleration, etc.
Embodiments of the present invention will now be described in detail with reference to the drawings.
In the differential state of the electric type differential portion 12 configured as described above, a differential action is achieved by enabling the rotation of the three rotating elements, i.e., the sun gear SS, the carrier SCA, and the ring gear SR relative to each other in the differential planetary gear device 16 and, therefore, the output of the engine 20 is distributed to the first motor generator MG1 and the differential output member 22. When a portion of the distributed output of the engine 20 rotationally drives the first motor generator MG1, electric energy is generated through the regenerative control (generation control) of the first motor generator MG1; the electric energy is used for the power running control of the second motor generator MG2 disposed on the power transmission path on the rear wheel side; and excess electric energy is used to charge an electric storage device 64 (see
The front and rear wheel power distribution device 14 is made up mainly of a single pinion type distribution planetary gear device 24 acting as a differential mechanism, and a ring gear CR of the distribution planetary gear device 24 is an input rotating element and is integrally coupled to the differential output member 22. A carrier CCA is integrally coupled to a rear-wheel output shaft 26 and a sun gear CS is integrally coupled to a front-wheel output gear 28. The rear-wheel output shaft 26 is operatively coupled to left and right rear wheels 34 via an automatic transmission 30 and a rear-side left and right wheel power distribution device 32, and a second motor generator MG2 is coupled to the power transmission path between the automatic transmission 30 and the carrier CCA in a power transmittable manner. The second motor generator MG2 can selectively fulfill functions of both an electric motor and an electric generator and, however, is used mainly as an electric motor in this embodiment to rotationally drive the rear wheels 34 for the motor traveling and to add an assist torque during the traveling using the engine 20 as a drive power source. The front-wheel output gear 28 is operatively coupled to left and right front wheels 44 via a counter gear 36, a driven gear 38, a transmission shaft 40, and a front-side left and right wheel power distribution device 42. Since the electric type differential portion 12, the front and rear wheel power distribution device 14, the first motor generator MG1, and the second motor generator MG2 are configured substantially symmetrically relative to the shaft center thereof, the lower half is not depicted in the schematic of
Therefore, the front and rear wheel drive vehicle of this embodiment is a four-wheel-drive vehicle based on an FR (front-engine rear-drive) vehicle and the planetary gear type front and rear wheel power distribution device 14 is disposed between the electric type differential portion 12 and the second motor generator MG2 so as to transmit the power from the electric type differential portion 12 to the front wheels 44.
The front-wheel output gear 28 and the driven gear 38 have the same number of teeth and are rotatable at a constant speed in the same direction; the final reduction ratio (differential ratio) it on the rear wheel 34 side is equivalent to the final reduction ratio (differential ratio) if on the front wheel 44 side; and in the case of a gear ratio γT=1 in the automatic transmission 30, the gear ratios γr and γf from the front and rear wheel power distribution device 14 to the rear wheel 34 and the front wheel 44 are equivalent to each other. As a result, during straight traveling, the carrier CCA and the sun gear CS are rotated at the same rotation speed and the front and rear wheel power distribution device 14 is substantially integrally rotated and, if a difference in rotation speed is generated between the front and rear wheels at the time of turning etc., the carrier CCA and the sun gear CS are allowed to differentially rotated. On the other hand, at the time of the speed-increasing gear ratio when the gear ratio γT of the automatic transmission 30 is smaller than one, since the gear ratio γr from the front and rear wheel power distribution device 14 to the rear wheel 34 becomes smaller than the gear ratio γf to the front wheel 44, the carrier CCA on the rear wheel 34 side is rotated slower relative to the sun gear CS on the front wheel 44 side as depicted in
The automatic transmission 30 corresponds to a shifting portion and is a stepped transmission having the gear ratio γT selectable from a speed-decreasing gear ratio greater than one to a speed-increasing gear ratio smaller than one.
The second planetary gear device 52 includes a second sun gear S2, a second carrier CA2 that supports a planetary gear in a rotatable and revolvable manner, and a second ring gear R2 engaging with the second sun gear S2 via the planetary gear, and the third planetary gear device 54 includes a third sun gear S3, a third carrier CA3 that supports a planetary gear in a rotatable and revolvable manner, and a third ring gear R3 engaging with the third sun gear S3 via the planetary gear. The second ring gear R2 is selectively coupled to the first ring gear R1 via a clutch C1. The second sun gear S2 and the third sun gear S3 are integrally coupled to each other, selectively coupled to the first ring gear R1 via a clutch C2, and selectively coupled to the case 56 via a brake B1 to stop rotation. The third carrier CA3 is selectively coupled to the case 56 via a brake B2 to stop rotation. The second carrier CA2 and the third ring gear R3 are integrally coupled to each other and are integrally coupled to an AT output shaft 58 to output rotation after shifting gears. Since the automatic transmission 30 is also configured substantially symmetrically relative to the shaft center, the lower half is not depicted in the schematic of
The clutches C0, C1, C2, and the brakes B0, B1, B2 (hereinafter, simply, clutches C and brakes B if not particularly distinguished) are hydraulic friction engagement devices and are made up of a wet multi-plate type with a hydraulic actuator pressing a plurality of friction plates overlapped with each other or as a band brake with a hydraulic actuator fastening one end of one or two bands wrapped around an outer peripheral surface of a rotating drum, or the like, integrally coupling members on the both sides of the devices interposed therebetween. These clutches C and brakes B are selectively engaged and released as depicted in an operation table of
Although a stepless transmission is generally made up of the electric type differential portion 12 functioning as a stepless transmission, and the automatic transmission 30 in the power transmission device 10 configured as described above, the electric type differential portion 12 and the automatic transmission 30 can form the state equivalent to a stepped transmission by performing control such that the gear ratio γS of the electric type differential portion 12 is kept constant. Specifically, when the electric type differential portion 12 functions as a stepless transmission and the automatic transmission 30 in series with the electric type differential portion 12 functions as a stepped transmission, the rotation speeds of the differential output member 22 and the rear-wheel output shaft 26 are varied in a stepless manner for at least one gear stage G of the automatic transmission 30, and a stepless gear ratio width is acquired in the gear stage G. A total gear ratio of the power transmission device 10 is acquired for each gear stage by performing control such that the gear ratio γS of the electric type differential portion 12 is kept constant and by selectively performing engagement operation of the clutches C and the brakes B to establish any one of the first speed gear stage “1st” to the O/D gear stage “O/D”. For example, if the rotation speed NMG1 of the first motor generator MG1 is controlled such that the gear ratio γS of the electric type differential portion 12 is fixed to “1”, a total gear ratio of the electric type differential portion 12 and the automatic transmission 30 is the same as the gear ratio γT of each gear stage of the first speed gear stage “1st” to the O/D gear stage “O/D” of the automatic transmission 30.
The electronic control device 80 is supplied, from sensors, switches, etc., as depicted in
The electronic control device 80 outputs control signals to an engine output control device 60 (see
The “M” position is disposed, for example, at the same position as the “D” position in the longitudinal direction of a vehicle adjacently along the width direction of the vehicle and when the shift lever 66 is operated to the “M” position, any one of four shift ranges from D-range to L-range is selected depending on the operation of the shift lever 66. Specifically, the “M” position is provided with an upshift position “+” and a downshift position “−” along the longitudinal direction of a vehicle and each time the shift lever 66 is operated to the upshift position “+” or the downshift position “−”, the shift range goes up or down one by one. The four shift ranges from D-range to L-range are shift ranges of a plurality of types having different gear ratios on the high-speed side (the side of smaller gear ratios) in a variation range where the automatic transmission control of the power transmission device 10 is available; specifically, the high-speed-side gear stages available for the shifting of the automatic transmission 30 is reduced one by one; and although the highest speed gear stage is the O/D gear stage “O/D” in the D-range, the highest speed gear stage is set to the third speed gear stage “3rd” in a 3-range, to the second speed gear stage “2nd” in a 2-range, and to the first speed gear stage “1st” in an L-range. The shift lever 66 is automatically returned to the “M” position from the upshift position “+” and the downshift position “−” by a biasing means such as a spring.
In this case, the stepped transmission control means 82 outputs to the hydraulic control circuit 70 a command (a shift output command, a hydraulic pressure command) for engaging and releasing the hydraulic friction engagement devices (the clutches C and the brakes B) involved in the shift of the automatic transmission 30, i.e., a command for executing the clutch-to-clutch shift by releasing the release-side friction engagement devices involved in the shift of the automatic transmission 30 and by engaging the engagement-side friction engagement devices so as to establish a predetermined gear stage in accordance with the engagement table depicted in
On the other hand, the hybrid control means 90 drives the engine 20 to operate in an efficient operation range, controls the drive force distribution between the engine 20 and the second motor generator MG2, and changes a reaction force due to the electric generation by the first motor generator MG1 to the optimum state to control the gear ratio γS of the electric type differential portion 12 acting as an electric stepless transmission. Therefore, for a traveling vehicle speed V at a time point, a target (request) output of a vehicle is calculated from the accelerator opening degree Acc that is an output request amount of a driver and the vehicle speed V, and a necessary total target output is calculated from the target output and a charge request value of the vehicle. A target engine output is then calculated such that the total target output is acquired in consideration of a transmission loss, loads of accessories, an assist torque of the second motor generator MG2, etc., to control the engine 20 while an amount of the electric generation of the first motor generator MG1 is controlled so as to achieve the engine rotation speed NE and the engine torque TE enabling acquisition of the target engine output.
The electric type differential portion 12 is driven to function as an electric stepless transmission to match the engine rotation speed NE determined for operating the engine 20 in an efficient operation range with the rotation speed of the differential output member 22 determined from the vehicle speed V and the shift stages of the automatic transmission 30, i.e., the rotation speed of the ring gear SR. Therefore, the hybrid control means 90 determines a target value of the total gear ratio of the power transmission device 10 depending on the vehicle speed V and controls the gear ratio γS of the electric type differential portion 12 in consideration of the gear stages of the automatic transmission 30 to acquire the target value such that the engine 20 is operated along an optimal fuel consumption curve, based on the optimal fuel consumption curve (fuel consumption map, relationship) of the engine 20 represented by a broken line of FIG. 7 empirically obtained and stored in advance so as to satisfy both the drivability and the fuel consumption property during travelling with stepless transmission in the two-dimensional coordinates made up of the engine rotation speed NE and the output torque (engine torque) TE of the engine 20.
In this case, the hybrid control means 90 supplies the electric energy generated by the first motor generator MG1 to the electric storage device 64 and the second motor generator MG2 via the inverter 62 and, as a result, a main portion of the power of the engine 20 is mechanically transmitted to the differential output member 22 while a portion of the power of the engine 20 is consumed for the electric generation of the first motor generator MG1 and converted into electric energy. The electric energy is supplied through the inverter 62 to the second motor generator MG2 and the second motor generator MG2 is driven to add the torque thereof to the rear-wheel output shaft 26. The equipments related to the electric energy from the generation to the consumption by the second motor generator MG2 make up an electric path from the conversion of a portion of the power of the engine 20 into an electric energy to the conversion of the electric energy into a mechanical energy. During normal steady traveling, as depicted in a solid line of
The hybrid control means 90 controls the first motor generator rotation speed NMG1 with the electric CVT function of the electric type differential portion 12 such that the engine rotation speed NE is maintained substantially constant or controlled at an arbitrary rotation speed regardless of whether a vehicle is stopped or traveling.
The hybrid control means 90 functionally includes an engine output control means that outputs commands separately or in combination to the engine output control device 60 to control opening/closing of the electronic throttle valve with the throttle actuator for throttle control, to control a fuel injection amount and an injection timing of the fuel injection device for the fuel injection control, and to control the timing of the ignition by the ignition device such as an igniter for the ignition timing control, executing the output control of the engine 20 to generate necessary engine output. For example, the throttle actuator is basically driven based on the accelerator operation amount Acc in accordance with a preliminarily stored relationship not depicted to execute the throttle control such that the throttle valve opening degree θTH is increased as the accelerator operation amount Acc increases.
The hybrid control means 90 can achieve the motor traveling with the electric CVT function (differential action) of the electric type differential portion 12 regardless of whether the engine 20 is stopped or in the idle state. For example, the engine 20 is stopped or put into the idle state and the motor traveling is performed by using only the second motor generator MG2 as a drive force source in a relatively lower output torque zone, i.e., a lower engine torque zone generally considered as having poor engine efficiency as compared to a higher torque zone, or in a relatively lower vehicle speed zone of the vehicle speed V, i.e., a lower load zone. For example, in
The hybrid control means 90 can perform so-called torque assist for complementing the power of the engine 20, even during engine traveling using the engine 20 as the drive force source, by supplying the electric energy from the first motor generator MG1 and/or the electric energy from the electric storage device 64 through the electric path described above to the second motor generator MG2 and by driving the second motor generator MG2 to apply a torque to the rear wheels 34. For example, at the time of acceleration traveling when the accelerator pedal is deeply depressed or on a climbing road, the second motor generator MG2 is subjected to the power running control to perform the torque assist. Although the engine traveling area for performing the engine traveling is located on the outside of the solid line A in
The hybrid control means 90 can allow the first motor generator MG1 to freely rotate, i.e., idle in the no-load state to achieve the state in which the electric type differential portion 12 is unable to transmit a torque i.e., the state equivalent to the state with the power transmission path interrupted in the electric type differential portion 12, and in which the output from the electric type differential portion 12 is not generated. Therefore, the hybrid control means 90 can put the first motor generator MG1 into the no-load state to put the electric type differential portion 12 into the neutral state (neutral state) with the power transmission path electrically interrupted.
The hybrid control means 90 has a function as a regenerative control means that operates the second motor generator MG2 as an electric generator through the regenerative control thereof when the second motor generator MG2 is rotationally driven by a kinetic energy of a vehicle, i.e., a reverse drive force input from the rear wheels 34 and that charges the electric storage device 64 through the inverter 62 with the electric energy to improve the fuel consumption during the inertia traveling (during coasting) when the acceleration is turned off and at the time of braking by the foot brake or the like. This regenerative control is controlled to achieve a regenerative amount determined based on an electric charge amount SOC of the electric storage device 64 and the braking force distribution of a braking force from a hydraulics brake for acquiring a braking force corresponding to a brake pedal operation amount.
As depicted in the functional block line diagram of
Concerning this case, in the front and rear wheel power distribution device 14 of this embodiment, the ring gear CR of the single pinion type distribution planetary gear device 24 is coupled as an input rotation element to the differential output member 22, and the carrier CCA is coupled to the rear-wheel output shaft 26 for output to the rear wheel side disposed with the automatic transmission 30. Therefore, if the gear stage of the automatic transmission 30 is the O/D gear stage “O/D” having the gear ratio γT<1 and the gear ratio γr from the front and rear wheel power distribution device 14 to the rear wheel 34 becomes smaller than the gear ratio γf to the front wheel 44, the carrier CCA on the rear wheel 34 side rotates slower relative to the sun gear CS on the front wheel 44 side as depicted in
A solid line of
In
The acceleration traveling differential control means 94 executes the acceleration traveling differential control to perform the regenerative control of the first motor generator MG1 to recover electric energy during acceleration traveling and to limit the rotation speed NMG1 of the first motor generator MG1 at the time of the regenerative control in accordance with a predetermined regenerative condition. The regenerative condition is prescribed so as to avoid overcharge of the electric storage device 64 if the electric energy acquired by the first motor generator MG1 is greater than the electric energy consumed by the second motor generator MG2, for example, or prescribed considering an allowable maximum charge amount (power) of the electric storage device 64 itself, etc., and an allowable maximum rotation speed NMG1max is set in advance based on the electric charge amount SOC of the electric storage device 64, etc. If the rotation speed NMG1 of the first motor generator MG1 is limited by the allowable maximum rotation speed NMG1max in this way, the engine rotation speed NE is limited depending on the vehicle speed V, i.e., the rotation speed of the differential output member 22 and desired output may not be acquired.
In this case, in the front and rear wheel power distribution device 14 of this embodiment, the ring gear CR of the single pinion type distribution planetary gear device 24 is coupled as an input rotation element to the differential output member 22, and the carrier CCA is coupled to the rear-wheel output shaft 26 for output to the rear wheel side disposed with the automatic transmission 30. Therefore, if the gear stage of the automatic transmission 30 is the first speed gear stage “1st” or the second speed gear stage “2nd” having the gear ratio γT>1 and the gear ratio γr from the front and rear wheel power distribution device 14 to the rear wheel 34 becomes greater than the gear ratio γf to the front wheel 44, the carrier CCA on the rear wheel 34 side rotates faster relative to the sun gear CS on the front wheel 44 side as depicted in
A solid line of
The power transmission device 10 of a front and rear wheel drive vehicle of this embodiment is configured such that an input rotation element, a first output rotation element, and a second output rotation element are arranged in series from one end to the other end on a collinear diagram capable of representing the rotation speeds of the three rotation elements (CS, CCA, CR) of the front and rear wheel power distribution device 14 on a straight line. Specifically, the ring gear CR of the single pinion type distribution planetary gear device 24 is the input rotation element and is coupled to the differential output member 22; the carrier CCA is the first output rotation element and is coupled to the rear-wheel output shaft 26; and the sun gear CS is the second output rotation element and is coupled to the front-wheel output gear 28. Therefore, if the gear ratio γr from the first output rotation element, i.e., the carrier CCA to the rear wheel 34 is different from the gear ratio γf from the second output rotation element, i.e., the sun gear CS to the front wheel 44 due to the presence/absence of the automatic transmission 30 and a difference between the final reduction ratios if, it of the front and rear wheels, the rotation speed of the input rotation element located at the end among the three rotation elements (CS, CCA, CR), i.e., the ring gear CR is maximized or minimized.
Therefore, if the gear ratios γr and γf are determined such that the rotation speed of the ring gear CR, i.e., the input rotation element is reduced during high-sped traveling, specifically, if the gear ratio γr on the rear wheel side is set smaller than the gear ratio γf on the front wheel side, the rotation speed of the ring gear CR is reduced as well as that of the differential output member 22 (ring gear SR) of the electric type differential portion 12 as depicted in
If the gear ratios γr and γf are determined such that the rotation speed of the ring gear CR, i.e., the input rotation element is increased during acceleration traveling at startup, etc., specifically, if the gear ratio γr on the rear wheel side is set greater than the gear ratio γf on the front wheel side, the rotation speed of the ring gear CR is increased as well as that of the differential output member 22 (ring gear SR) of the electric type differential portion 12 as depicted in
In this embodiment, the power transmission path from the front and rear wheel power distribution device 14 to the rear wheel 34 is disposed with the automatic transmission 30 having the gear ratio selectable from a speed-decreasing gear ratio larger than one to a speed-increasing gear ratio smaller than one; if the O/D gear stage “O/D” having the speed-increasing gear ratio is selected during high-speed traveling, the gear ratio γr on the rear wheel side is set smaller than the gear ratio γf on the front wheel side to reduce the rotation speed of the differential output member 22, i.e., the ring gear SR of the electric type differential portion 12; and, on the other hand, if the first speed gear stage “1st” or the second speed gear stage “2nd” having the speed-decreasing gear ratio is selected during acceleration traveling, the gear ratio γr on the rear wheel side is set greater than the gear ratio γf on the front wheel side to increase the rotation speed of the differential output member 22, i.e., the ring gear SR of the electric type differential portion 12. Although the differential control by the high-speed traveling differential control means 92 is performed as needed during high-speed travelling, since the rotation speed of the differential output member 22, i.e., the ring gear SR of the electric type differential portion 12 is reduced, a change in rotation of the first motor generator MG1 in the inverse rotation direction is suppressed and the energy circulation becomes difficult to occur or an energy loss due to the energy circulation is reduced, and the energy efficiency is improved. Although the differential control by the acceleration traveling differential control means 94 is performed as need during acceleration travelling, since the rotation speed of the differential output member 22, i.e., the ring gear SR of the electric type differential portion 12 is increased, the restriction on increase in the rotation speed of the differential input shaft 18 due to the rotation speed limitation of the first motor generator MG1 is alleviated and the rotation speed NE of the engine 20 coupled to the differential input shaft 18 can be increased to acquire excellent power performance (power).
Other embodiments of the present invention will then be described. In the following embodiments, the portions common to the embodiment described above are denoted by the same reference numerals and will not be described in detail.
The power transmission device 202 of
In a front and rear wheel power distribution device 220 of
In a front and rear wheel power distribution device 240 of
Although the single pinion type differential planetary gear device 16 is used as a differential mechanism of the electric type differential portion 12 or 250 in the embodiments, a double pinion type differential planetary gear device can also be employed.
Although the embodiments of the present invention have been described in detail with reference to the drawings, these embodiments are merely exemplary embodiments and the present invention may be implemented in variously modified or altered forms based on the knowledge of those skilled in the art.
Since the power transmission device of a front and rear wheel drive vehicle of the present invention is configured such that an input rotation element, a first output rotation element, and a second output rotation element are arranged in series from one end to the other end on a collinear diagram capable of representing the rotation speeds of the three rotation elements of the front and rear wheel power distribution device on a straight line, if a gear ratio from the first output rotation element to a first axle is different from a gear ratio from the second output rotation element to a second axle due to the presence/absence of the automatic transmission and a difference between the final reduction ratios of the front and rear wheel, the rotation speed is maximized or minimized in the input rotation element located at the end among the three rotation elements. Therefore, if the gear ratios are determined such that the rotation speed of the input rotation element is reduced during high-sped traveling, a change in the rotation is suppressed in the power running rotation direction of the first rotating machine coupled to the electric type differential portion correspondingly to the reduction of the rotation speed of the input rotating element, and the energy circulation becomes difficult to occur, and the energy efficiency is improved, while if the gear ratios are determined such that the rotation speed of the input rotation element is increased during acceleration traveling, a rotation speed of a differential input member is allowed to increase correspondingly to the increase in the rotation speed of the input rotation element and the rotation speed of a drive force source such as an engine coupled to the differential input member can be increased to acquired excellent power performance, which is preferably applied to various front and rear wheel drive vehicles requiring excellent energy efficiency and power performance.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2008/072289 | 12/9/2008 | WO | 00 | 6/8/2011 |