JP7741746B2 - vehicle - Google Patents

Description

The present invention relates to a vehicle.

In recent years, efforts to realize a low-carbon or carbon-free society have been gaining momentum as a concrete measure against global climate change. In automobiles and other vehicles, there is also a demand for reduced _CO2 emissions and improved energy efficiency, leading to the trend toward electrification of drive sources. Specifically, vehicles (hereinafter also referred to as "electric vehicles"; for example, electric vehicles) equipped with an electric motor as a drive source for driving the drive wheels and a power source (e.g., a battery) for supplying power to the electric motor have been developed.

Also, vehicles with drive on both the front and rear wheels, known as "four-wheel drive vehicles," have been known for some time. Four-wheel drive vehicles are often used in vehicles that require higher power performance and better off-road performance. However, with growing environmental awareness in recent years, there is also a demand for higher energy efficiency in such four-wheel drive vehicles.

For example, Patent Document 1 below discloses a technology that aims to improve power efficiency and suppress temperature increases in the drive unit by varying the torque distribution map used to control torque distribution between a front-wheel drive motor that is highly efficient in low-speed, high-torque ranges and a rear-wheel drive motor that is highly efficient in high-speed, low-torque ranges, depending on the required torque.

Japanese Patent Application Laid-Open No. 2018-057075

However, conventional technology leaves room for improvement in terms of further improving the energy efficiency of vehicles.

The present invention provides a vehicle that can further improve energy efficiency.

The present invention provides
A battery,
a voltage control unit that outputs a boosted voltage obtained by boosting the output voltage of the battery;
a main drive unit having a main drive motor driven by the power of the boosted voltage output from the voltage control unit, and outputting a main drive force for driving one of the front wheels and the rear wheels;
a secondary drive unit having a secondary drive motor driven by the power of the boosted voltage output from the voltage control unit, and outputting a secondary drive force that drives the other of the front wheels and the rear wheels;
a control unit that controls the voltage control unit, the main drive unit, and the slave drive unit;
A vehicle comprising:
The control unit
the required driving force of the vehicle is distributed between the main driving force and the secondary driving force in accordance with a predetermined distribution ratio, and when the temperature of the main drive unit is equal to or higher than a predetermined value, the main driving force is made smaller and the secondary driving force is made larger than when the temperature is below the predetermined value;
the boost voltage when the temperature is equal to or higher than the predetermined value is set to a second boost voltage that is more suitable for driving the slave drive motor than a first boost voltage that is the boost voltage when the temperature is lower than the predetermined value;
It is a vehicle.

The present invention makes it possible to provide a vehicle that can further improve energy efficiency.

1 is a schematic diagram showing the schematic configuration of a vehicle according to an embodiment of the present invention; FIG. 10 is a diagram illustrating an example of the flow of power and electricity when the main drive unit is in EV driving mode (electric power drive mode). FIG. 10 is a diagram showing an example of the flow of power and electricity when the main drive unit is in series running (electric drive mode). FIG. 2 is a diagram showing an example of the flow of power and electricity when the main drive unit is running on the engine (engine drive mode). FIG. 2 is a block diagram showing an example of a functional configuration of a control unit of the vehicle according to the present embodiment. FIG. 10 is a diagram illustrating an example of a main driving force reduction amount. 4 is a flowchart illustrating an example of processing executed by a control unit of the present embodiment. 4 is a timing chart showing an example of specific control performed in the vehicle of the present embodiment. FIG. 10 is a diagram showing a modified example of the main drive unit.

One embodiment of a vehicle of the present invention will be described below with reference to the accompanying drawings. Note that, below, identical or similar elements will be designated by identical or similar reference numerals, and their description may be omitted or simplified as appropriate.

[vehicle]
As shown in Figure 1, the vehicle V of this embodiment includes a main drive unit DU1 and a secondary drive unit DU2 that are mechanically independent. Here, "mechanically independent" means that the power of one unit is not mechanically transmitted to the other unit by a propeller shaft or the like. In this embodiment, the main drive unit DU1 outputs a main drive force to drive the front wheels FWR, and the secondary drive unit DU2 outputs a secondary drive force to drive the rear wheels RWR.

The vehicle V further includes a battery BAT, a voltage control unit VCU, and a control unit CTR.

The battery BAT has multiple storage cells connected in series and supplies a high voltage of, for example, 100 to 200 V. The storage cells are, for example, lithium-ion batteries or nickel-metal hydride batteries.

The voltage control unit VCU boosts the output voltage from the battery BAT while it remains DC, and outputs the boosted voltage obtained by this boosting to the main drive unit DU1 and the sub drive unit DU2. In other words, in the vehicle V, the boosted voltage generated by a single voltage control unit VCU can be supplied in common to both the main drive unit DU1 and the sub drive unit DU2. The voltage control unit VCU may also step down the input voltage input to (i.e., charging) the battery BAT. The voltage control unit VCU is, for example, a DC-DC converter.

[Main drive unit]
The main drive unit DU1 includes an engine ENG, a generator GEN, a main drive motor MOT1, a first inverter INV1, a second inverter INV2, and a first transmission mechanism T1. The main drive motor MOT1 and the generator GEN are connected to a battery BAT via a voltage control unit VCU, the first inverter INV1, and the second inverter INV2, enabling power supply from the battery BAT and energy regeneration to the battery BAT. In FIG. 1, dotted lines indicate power wiring, and dashed lines indicate control signal wiring.

The first inverter INV1 converts DC voltage into AC voltage and supplies three-phase current to the generator GEN. The first inverter INV1 also converts AC voltage generated by the generator GEN into DC voltage.

The second inverter INV2 converts DC voltage to AC voltage and supplies three-phase current to the main drive motor MOT1. The second inverter INV2 also converts AC voltage generated by the main drive motor MOT1 during braking of the vehicle V into DC voltage.

The first transmission mechanism T1 includes an input shaft 21, a generator shaft 23, and a countershaft 25 arranged parallel to one another, and a first differential mechanism D1.

The input shaft 21 is arranged coaxially with the crankshaft 12 of the engine ENG. The power of the crankshaft 12 is transmitted to the input shaft 21 via a damper 13. The input shaft 21 is provided with an output gear 32 that forms part of the generator drive gear train, which will be described later.

On the input shaft 21, on the side opposite the engine ENG, is provided an output gear 53, which constitutes part of the engine power transmission gear train. A hydraulic clutch CL is provided between the output gear 32 on the input shaft 21 and the output gear 53 to releasably connect the input shaft 21 and the output gear 53.

The generator shaft 23 is a dual-structure rotating shaft comprising an inner shaft 27 and an outer shaft 29 arranged concentrically around the inner shaft 27. An input gear 34 is provided on the engine ENG side of the inner shaft 27, which meshes with an output gear 32 on the input shaft 21. The output gear 32 on the input shaft 21 and the input gear 34 on the inner shaft 27 form a generator drive gear train that transmits the power of the input shaft 21 to the inner shaft 27.

Furthermore, an outer peripheral shaft 29 is mounted on the outer diameter side of the inner peripheral shaft 27, approximately in the center, so as to be able to rotate relative to it. A generator GEN is attached to the inner peripheral shaft 27 on the side opposite the engine ENG. The generator GEN is composed of a rotor R fixed to the inner peripheral shaft 27 and a stator S fixed to a case (not shown) and positioned opposite the outer diameter side of the rotor R.

The driving force of the input shaft 21 is transmitted to the inner shaft 27 of the generator shaft 23 via the generator drive gear train, and the rotation of the inner shaft 27 rotates the rotor R of the generator GEN. This allows the driving force from the input shaft 21 to be converted into electricity by the generator GEN.

On the engine ENG side of the outer shaft 29, an output gear 52 is provided that meshes with an input gear 54 on the countershaft 25 (described below), and on the side opposite the engine ENG side, a main drive motor MOT1 is attached. The main drive motor MOT1 is composed of a rotor R fixed to the outer shaft 29 and a stator S fixed to a case (not shown) and positioned opposite the outer diameter of the rotor R.

The output gear 52 on the outer shaft 29 and the input gear 54 on the counter shaft 25 form a motor power transmission gear train for transmitting the power of the outer shaft 29 to the counter shaft 25. Therefore, when the outer shaft 29 is rotated by the driving force of the main drive motor MOT1, that rotation is transmitted to the counter shaft 25 via the motor power transmission gear train.

On the countershaft 25, from the engine ENG side, there is provided an output gear 56 that meshes with the ring gear 58 of the first differential mechanism D1, and an input gear 54 that meshes with the output gear 53 on the input shaft 21 and the output gear 52 on the outer shaft 29. The output gear 53 on the input shaft 21 and the input gear 54 on the countershaft 25 form an engine power transmission gear train for transmitting the power of the input shaft 21 to the countershaft 25. In addition, the output gear 56 on the countershaft 25 and the ring gear 58 of the first differential mechanism D1 form a final gear train for transmitting the driving force of the countershaft 25 to the first differential mechanism D1.

The driving force of the main drive motor MOT1, input to the countershaft 25 via the motor power transmission gear train, and the driving force of the engine ENG, input to the countershaft 25 via the engine power transmission gear train, are output as the main driving force of the main drive unit DU1, transmitted to the first differential mechanism D1 via the final gear train, and then transmitted from the first differential mechanism D1 to the front wheels FWR.

The first transmission mechanism T1 of the main drive unit DU1 in this embodiment includes a first transmission mechanism 41 that connects the generator GEN and the engine ENG so that power can be transmitted, and a second transmission mechanism 42 that connects the main drive motor MOT1 and the front wheels FWR so that power can be transmitted. Specifically, the first transmission mechanism 41 is composed of the input shaft 21, output gear 32, input gear 34, and inner shaft 27, while the second transmission mechanism 42 is composed of the outer shaft 29, output gear 52, input gear 54, countershaft 25, output gear 56, and first differential mechanism D1.

The hydraulic clutch CL selectively switches between a state in which the power transmission path between the first transmission mechanism 41 and the second transmission mechanism 42 is connected and a state in which the power transmission path between the first transmission mechanism 41 and the second transmission mechanism 42 is disconnected. That is, by engaging the hydraulic clutch CL, the power transmission path between the first transmission mechanism 41 and the second transmission mechanism 42 is connected (locked up), and by disengaging the hydraulic clutch CL, the power transmission path between the first transmission mechanism 41 and the second transmission mechanism 42 is disconnected. In the first speed change mechanism T1, the input gear 54 meshes with the output gear 53 on the input shaft 21 and the output gear 52 on the outer circumferential shaft 29. Therefore, when the hydraulic clutch CL is engaged, the power transmission path between the first transmission mechanism 41 and the second transmission mechanism 42 is connected, enabling power transmission between the first transmission mechanism 41 and the second transmission mechanism 42. On the other hand, when the hydraulic clutch CL is released, the output gear 53 disengages from the input shaft 21, cutting off the power transmission path between the first transmission mechanism 41 and the second transmission mechanism 42, and disabling power transmission between the first transmission mechanism 41 and the second transmission mechanism 42.

[Follower drive unit]
The slave drive unit DU2 includes a slave drive motor MOT2, a third inverter INV3, and a second transmission mechanism T2. The slave drive motor MOT2 is connected to a battery BAT via a voltage control unit VCU and the third inverter INV3, and is capable of receiving power from the battery BAT and regenerating energy back into the battery BAT. In FIG. 1, dotted lines indicate power wiring, and dashed lines indicate control signal wiring.

The second transmission mechanism T2 includes a motor output shaft 26 and an output shaft 28 arranged parallel to each other, and a second differential mechanism D2.

In the slave drive unit DU2, a third drive gear 62 is attached to one end of the motor output shaft 26 of the slave drive motor MOT2 so that they rotate together. A third driven gear 64 meshing with the third drive gear 62 and an output gear 66 are attached to the output shaft 28, which extends parallel to the motor output shaft 26 of the slave drive motor MOT2, so that they rotate together. Therefore, the driving force of the slave drive motor MOT2 is transmitted to the output shaft 28 via the third drive gear 62 and the third driven gear 64. The driving force transmitted to the output shaft 28 is then transmitted from the output gear 66 to the rear wheels RWR via the second differential mechanism D2. Conversely, the driving force from the rear wheels RWR is transmitted to the slave drive motor MOT2 via the second differential mechanism D2, the output gear 66, the output shaft 28, the third driven gear 64, the third drive gear 62, and the motor output shaft 26.

[Main drive unit drive mode]
Next, the drive modes of main drive unit DU1 will be described with reference to Figures 2 to 4. Figures 2 to 4 are simplified versions of the configuration related to main drive unit DU1 in Figure 1, with the flow of power indicated by dotted arrows and the flow of power indicated by thick solid arrows.

The drive modes of the main drive unit DU1 include an electric drive mode in which the drive force of the main drive motor MOT1 is output as the main drive force, and an engine drive mode in which the drive force of the engine ENG is output as the main drive force. In the electric drive mode, the hydraulic clutch CL is disengaged and the drive force of the main drive motor MOT1 is output as the main drive force. The electric drive mode includes EV driving and series driving, which will be described later. In the engine drive mode, the hydraulic clutch CL is engaged and the drive force of the engine ENG is output as the main drive force. The engine drive mode includes engine driving, which will be described later.

<EV driving (electric power mode)>
As shown in Figure 2, in EV driving, the engine ENG is put into a non-operating state, and the main drive motor MOT1 is driven by power supplied from the battery BAT. That is, by driving the main drive motor MOT1 with power supplied from the battery BAT, the outer circumferential shaft 29 of the generator shaft 23 is rotated by the driving force of the main drive motor MOT1, and this rotation is transmitted to the countershaft 25 via the motor power transmission gear train. The driving force of the main drive motor MOT1 transmitted in this manner is output as main driving force via the final gear train and the first differential mechanism D1, and is transmitted to the front wheels FWR. This enables EV driving.

<Series driving (electric drive mode)>
As shown in FIG. 3 , in series running, the engine ENG is operated, and the main drive motor MOT1 is driven by electric power generated by the generator GEN. That is, the driving force of the engine ENG is input from the input shaft 21 to the inner shaft 27 via the generator drive gear train, causing the inner shaft 27 to rotate. This rotates the rotor R of the generator GEN, which is fixed to the inner shaft 27, causing the generator GEN to generate electricity. The electric power generated by the generator GEN is supplied to the main drive motor MOT1, which drives the main drive motor MOT1. The driving force of the main drive motor MOT1 rotates the outer shaft 29 of the generator shaft 23, and this rotation is transmitted to the countershaft 25 via the motor power transmission gear train. The driving force of the main drive motor MOT1 transmitted in this manner is output as main driving force via the final gear train and the first differential mechanism D1 and transmitted to the front wheels FWR. This enables so-called series running, in which all of the driving force of the engine ENG is converted into electricity by the generator GEN.

<Engine driving (engine drive mode)>
As shown in FIG. 4 , during engine running, the hydraulic clutch CL is engaged, and the driving force of the engine ENG is output as the main driving force and transmitted to the front wheels FWR. That is, by engaging the hydraulic clutch CL, the driving force of the input shaft 21 is transmitted to the countershaft 25 via the engine power transmission gear train, and then to the front wheels FWR via the final gear train and the first differential mechanism D1. This enables engine running. Here, the input shaft 21 and the inner shaft 27 are constantly connected via the generator drive gear train, so that the rotor R of the generator GEN rotates as the inner shaft 27 rotates. Therefore, the generator GEN can generate electricity, which rotates the main drive motor MOT1. This generated electricity can then be used to output the driving force of the engine ENG and the driving force of the main drive motor MOT1 as the main driving force, enabling so-called parallel running.

[Control unit]
The control unit CTR is a device (computer) that controls the entire vehicle V. The control unit CTR is realized by, for example, an ECU (Electronic Control Unit) that includes a processor that performs various calculations, a storage device having a non-transitory storage medium that stores various information, an input/output device that controls input and output of data between the inside and outside of the control unit CTR, etc. Note that the control unit CTR may be realized by one ECU, or may be realized by multiple ECUs working together.

As shown in FIG. 5, the control unit CTR controls the input/output of the main drive unit DU1 and the secondary drive unit DU2 by controlling the voltage control unit VCU, the first inverter INV1, the second inverter INV2, the third inverter INV3, the engine ENG, the hydraulic clutch CL of the main drive unit DU1, etc., while referring to the detection values of various sensors, such as a vehicle speed sensor 81 that detects the vehicle speed VP, which is the traveling speed of the vehicle V, an accelerator pedal position sensor 83 that detects the accelerator pedal position AP, and a main drive unit temperature sensor 85 that detects the main drive unit temperature TFr, which is the temperature of the main drive unit DU1.

The main drive unit temperature TFr may be the temperature of the main drive motor MOT1, the temperature of the refrigerant that cools the engine ENG (for example, the coolant called "LLC"), or the temperature of the oil that lubricates the first transmission mechanism T1 of the main drive unit DU1 (for example, the oil called "ATF").

The control unit CTR includes a driving force control unit 71 and a boost voltage control unit 73 as functional units realized, for example, by a processor executing a program pre-stored in a storage device of the control unit CTR or by an input/output device of the control unit CTR.

The driving force control unit 71 controls the main driving force output from the main driving unit DU1 and the secondary driving force output from the secondary driving unit DU2. Specifically, the driving force control unit 71 first derives the required driving force Freq required for the vehicle V to travel based on the vehicle speed VP obtained from the vehicle speed sensor 81 and the accelerator pedal opening AP obtained from the accelerator pedal opening sensor 83, for example.

The driving force control unit 71 then allocates the derived required driving force Freq to the main driving force and the secondary driving force according to a predetermined allocation ratio. In this embodiment, a base driving force allocation map (not shown) that defines the relationship between the required driving force Freq, vehicle speed VP, and the allocation ratio between the main driving force and the secondary driving force is pre-stored in the control unit CTR. The driving force control unit 71 references this base driving force allocation map to obtain the allocation ratio that corresponds to the current vehicle speed VP and required driving force Freq.

For example, suppose the distribution ratio obtained corresponding to the current vehicle speed VP and required driving force Freq is "primary driving force: secondary driving force = 9:1." In this case, the driving force control unit 71 sets the primary driving force target value FcarFr, which is the target value for the primary driving force, to "required driving force Freq x 0.9," and sets the secondary driving force target value FcarRr, which is the target value for the secondary driving force, to "required driving force Freq x 0.1." The driving force control unit 71 then controls the primary driving force output from primary driving unit DU1 to the primary driving force target value FcarFr, and controls the secondary driving force output from secondary driving unit DU2 to the secondary driving force target value FcarRr.

The distribution ratio between the main driving force and the secondary driving force may be set so that the distribution ratio of one of the main driving force and the secondary driving force is zero (in other words, the distribution ratio of the other is 100%), for example, "main driving force: secondary driving force = 10:0".

The driving force control unit 71 can also correct the main driving force target value FcarFr and the secondary driving force target value FcarRr according to the main driving unit temperature TFr. Specifically, when the main driving unit temperature TFr is equal to or greater than a predetermined value Tth, the driving force control unit 71 corrects the main driving force target value FcarFr and the secondary driving force target value FcarRr so that the main driving force is smaller and the secondary driving force is larger than when the main driving unit temperature TFr is below the predetermined value Tth. Here, the predetermined value Tth is determined by the manufacturer of the vehicle V, etc., taking into account the heat resistance performance of the main driving unit DU1, and is set in advance in the control unit CTR.

In this way, when the main drive unit temperature TFr is equal to or higher than the predetermined value Tth, the main drive force is reduced and the secondary drive force is increased, thereby reducing the load on the main drive unit DU1 while ensuring the required drive force Freq by the sum of the main drive force and the secondary drive force. This prevents hesitation caused by an inability to ensure the required drive force Freq, while also preventing a rise in temperature in the main drive unit DU1 and protecting the main drive unit DU1. Note that an example of a specific correction amount (e.g., the main drive force reduction amount, described below) by the drive force control unit 71 will be described later, so a description thereof will be omitted here.

In this embodiment, the main drive unit DU1 is the primary drive source for the vehicle V, and the secondary drive unit DU2 is positioned as an auxiliary drive source. More specifically, a relatively large motor is used as the main drive motor MOT1, while a motor smaller than the main drive motor MOT1 is used as the secondary drive motor MOT2. When the main drive unit temperature TFr is below a predetermined value Tth (hereinafter also referred to as "normal"), the distribution ratio of the main drive force to the requested drive force Freq is set to 50% or more. This ensures the power performance and rough-road driving performance of the vehicle V, while also enabling the vehicle V to be made smaller, lighter, and at lower manufacturing costs than if a larger motor were also used for the secondary drive motor MOT2.

The boost voltage control unit 73 controls the boost voltage output from the voltage control unit VCU. Specifically, the boost voltage control unit 73 is configured to be able to change the boost voltage output from the voltage control unit VCU between a first boost voltage suitable for driving the main drive motor MOT1 and a second boost voltage suitable for driving the secondary drive motor MOT2. Note that the voltages that can be used as the first boost voltage and the second boost voltage are determined, for example, by the manufacturer of the vehicle V, taking into account the respective physical dimensions of the main drive motor MOT1 and the secondary drive motor MOT2, and are set in advance in the control unit CTR.

The boost voltage control unit 73 sets the boost voltage of the voltage control unit VCU to the first boost voltage during normal operation, in other words, when the main drive unit temperature TFr is below the predetermined value Tth. For example, the first boost voltage is a voltage that can reduce losses in the main drive motor MOT1 more than the second boost voltage. Therefore, by setting the first boost voltage as the boost voltage during normal operation, when the vehicle V is driven primarily using the main driving force output from the main drive unit DU1, the main drive motor MOT1 can be driven more efficiently than when the second boost voltage is used as the boost voltage during normal operation, making it possible to drive the vehicle V while suppressing power consumption and heat generation by the main drive motor MOT1.

On the other hand, the boost voltage control unit 73 sets the boost voltage of the voltage control unit VCU to the second boost voltage during abnormal times, in other words, when the main drive unit temperature TFr is equal to or higher than the predetermined value Tth. For example, the second boost voltage is a voltage that can reduce losses in the slave drive motor MOT2 more than the first boost voltage. Therefore, by setting the boost voltage during abnormal times, which increases the slave drive force output from the slave drive unit DU2, to the second boost voltage, the slave drive motor MOT2 can be driven more efficiently than when the boost voltage during abnormal times is the first boost voltage, making it possible to run the vehicle V while suppressing power consumption and heat generation by the slave drive motor MOT2.

The second boost voltage may also be a voltage that allows the secondary drive motor MOT2 to output a greater driving force for the current vehicle speed VP than the first boost voltage. This makes it easier to ensure the required driving force Freq by the sum of the primary and secondary driving forces, even if the primary driving force is reduced when the primary drive unit temperature TFr reaches or exceeds the predetermined value Tth.

Now, with reference to Figure 6, we will explain an example of the driving force that the slave drive motor MOT2 can output when supplied with power at the first boost voltage, and the driving force that the slave drive motor MOT2 can output when supplied with power at the second boost voltage. In Figure 6, the vertical axis represents driving force [N], and the horizontal axis represents vehicle speed [km/h].

The driving force characteristic 601 shown in Figure 6 represents the driving force that the slave drive motor MOT2 can output at each vehicle speed when power of the first boost voltage is supplied. As shown by the driving force characteristic 601, when power of the first boost voltage is supplied to the slave drive motor MOT2 when the vehicle speed VP is va [km/h], for example, the slave drive motor MOT2 can output a driving force of up to f1 [N].

The driving force characteristic 602 shown in Figure 6 represents the driving force that the slave drive motor MOT2 can output in response to each vehicle speed when power of the second boost voltage is supplied. As shown by the driving force characteristic 602, for example, when power of the second boost voltage is supplied to the slave drive motor MOT2 when the vehicle speed VP is va [km/h], the slave drive motor MOT2 can output a driving force of up to f2 [N].

The driving force control unit 71 described above takes into account the driving force characteristics 601, 602 of the secondary drive motor MOT2, and, for example, when the vehicle speed VP is va [km/h] and the main drive unit temperature TFr exceeds a predetermined value Tth, reduces the main driving force by the difference between f2 [N] and f1 [N].

More specifically, in this case, the driving force control unit 71 first derives the difference between f2 [N] and f1 [N] (hereinafter referred to as "Δf"; see the arrow indicated by reference numeral 603 in Figure 6) as the amount of reduction in the main driving force. The driving force control unit 71 then corrects the main driving force target value FcarFr so that the corrected main driving force target value FcarFr is smaller by Δf than the uncorrected main driving force target value FcarFr. This makes it possible to reduce the main driving force by the Δf amount derived as the amount of reduction in the main driving force. At this time, the driving force control unit 71 also corrects the secondary driving force target value FcarRr so that the difference between the requested driving force Freq and the corrected main driving force target value FcarFr becomes the corrected secondary driving force target value FcarRr.

In this way, the main driving force is reduced by the difference between the driving force that the slave drive motor MOT2 can output for the current vehicle speed VP when power is supplied at the first boost voltage and the driving force that the slave drive motor MOT2 can output for the current vehicle speed VP when power is supplied at the second boost voltage. This makes it possible to reduce the main driving force while ensuring the required driving force Freq by the sum of the main driving force and the slave driving force.

[Example of processing executed by the control unit]
Next, an example of processing executed by the control unit CTR will be described with reference to Fig. 7. The control unit CTR repeatedly executes the series of processing shown in Fig. 7 at a predetermined cycle, for example, while the vehicle V is running (for example, while the ignition power is on).

As shown in FIG. 7, the control unit CTR first derives the required driving force Freq based on the current vehicle speed VP and accelerator pedal opening AP (step S1). Next, the control unit CTR references the base driving force distribution map to obtain the distribution ratio corresponding to the current vehicle speed VP and the required driving force Freq (step S2). The control unit CTR then derives the main driving force target value FcarFr and the secondary driving force target value FcarRr, which distribute the required driving force Freq derived by the processing of step S1 between the main driving force and the secondary driving force according to the distribution ratio obtained by the processing of step S2 (step S3).

Next, the control unit CTR determines whether the main drive unit temperature TFr is equal to or greater than a predetermined value Tth (step S4). If the control unit CTR determines that the main drive unit temperature TFr is less than the predetermined value Tth (step S4: No), the control unit CTR proceeds directly to the processing of step S7. Note that when the main drive unit temperature TFr is determined to be less than the predetermined value Tth in this way (i.e., during normal operation), the boost voltage of the voltage control unit VCU is set to the first boost voltage.

On the other hand, if it is determined that the main drive unit temperature TFr is equal to or higher than the predetermined value Tth (step S4: Yes), the control unit CTR corrects the main drive force target value FcarFr and the secondary drive force target value FcarRr so that the main drive force is small and the secondary drive force is large, as described above (step S5), and changes the boost voltage of the voltage control unit VCU to the second boost voltage (step S6).

Then, the control unit CTR controls the main driving force output from the main driving unit DU1 to match the main driving force target value FcarFr, and controls the secondary driving force output from the secondary driving unit DU2 to match the secondary driving force target value FcarRr (step S7), thereby completing the series of processes shown in Figure 7.

[Example of specific control performed in a vehicle]
Next, an example of specific control performed in vehicle V will be described with reference to FIG. 8. FIG. 8(a) shows the temporal change in the distribution ratio of the main driving force to the requested driving force Freq. FIG. 8(b) shows the temporal change in the main driving unit temperature TFr. FIG. 8(c) shows the temporal change in the boost voltage of voltage control unit VCU. FIG. 8(d) shows the temporal change in the main driving force output from main driving unit DU1. FIG. 8(e) shows the temporal change in the secondary driving force output from secondary driving unit DU2.

In Figure 8, the period Tm1 up to time ta is the period during which the main drive unit temperature TFr is below the predetermined value Tth. As described above, during this period Tm1 (i.e., normal operation), the vehicle V is controlled so that the distribution ratio of the main drive force to the requested drive force Freq is 50% or more, and the main drive force is equal to or greater than the secondary drive force. When the vehicle V is driven primarily by the main drive force in this way, the control unit CTR sets the boost voltage of the voltage control unit VCU to the first boost voltage. This allows the main drive motor MOT1 to be driven efficiently, enabling the vehicle V to be driven.

On the other hand, during period Tm2, which occurs after time ta when the main drive unit temperature TFr reaches the predetermined value Tth, the main drive force is controlled to be smaller (see arrow 801 in Figure 8) and the secondary drive force is controlled to be larger (see arrow 802 in Figure 8) than during period Tm1. As a result, during period Tm2, the allocation ratio of the main drive force to the requested drive force Freq is lower than during period Tm1 (see arrow 803 in Figure 8).

For example, from time ta, the control unit CTR controls the main driving force to gradually decrease and the secondary driving force to gradually increase so that the distribution ratio of the main driving force to the requested driving force Freq gradually decreases. This makes it possible to change the distribution ratio of the main driving force to the requested driving force Freq while suppressing the occurrence of unpleasant vibrations, etc.

In this way, after time ta when the main drive unit temperature TFr reaches the predetermined value Tth, the load on the main drive unit DU1 is reduced by reducing the main drive force, making it possible to suppress the rise in the main drive unit temperature TFr (see arrow 804 in Figure 8). Furthermore, from time ta, the control unit CTR sets the boost voltage of the voltage control unit VCU to the second boost voltage. This makes it possible to efficiently drive the secondary drive motor MOT2 and run the vehicle V.

In addition, when the main drive unit temperature TFr drops to a certain level after time ta (for example, when it falls below a predetermined threshold), the control unit CTR may again cause the vehicle V to travel mainly using the main drive force, as in period Tm1.

As described above, according to this embodiment, when the slave drive force is increased as a result of the main drive unit temperature TFr reaching or exceeding the predetermined value Tth, the boost voltage of the voltage control unit VCU is set to a second boost voltage suitable for driving the slave drive motor MOT2. This makes it possible to drive the slave drive motor MOT2 more efficiently and run the vehicle V, even when the main drive unit temperature TFr is reaching or exceeding the predetermined value Tth, compared to when the boost voltage of the voltage control unit VCU is maintained at the first boost voltage. This therefore improves the energy efficiency of the vehicle V.

Although one embodiment of the present invention has been described above with reference to the drawings, it goes without saying that the present invention is not limited to such an example. It is clear that a person skilled in the art could conceive of various modifications or alterations within the scope of the claims, and it is understood that these naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiment may be combined in any manner as long as they do not deviate from the spirit of the invention.

For example, in the above-described embodiment, when the main drive unit temperature TFr is equal to or greater than the predetermined value Tth, the main drive force is reduced and the secondary drive force is increased compared to when the main drive unit temperature TFr is less than the predetermined value Tth. However, this is not limited to this. Similarly, for example, when the temperature of the secondary drive unit DU2 is equal to or greater than the predetermined value, the main drive force may be increased and the secondary drive force may be reduced compared to when the temperature of the secondary drive unit DU2 is less than the predetermined value. Furthermore, when the control unit CTR reduces the main drive force in response to the main drive unit temperature TFr being equal to or greater than the predetermined value Tth, the control unit CTR may change the boost voltage of the voltage control unit VCU to the second boost voltage, while when the control unit CTR increases the main drive force in response to the temperature of the secondary drive unit DU2 being equal to or greater than the predetermined value, the control unit CTR may maintain the boost voltage of the voltage control unit VCU at the first boost voltage.

In addition, in the above-described embodiment, the main drive unit DU1 drives the front wheels FWR and the secondary drive unit DU2 drives the rear wheels RWR, but it is also possible for the main drive unit DU1 to drive the rear wheels RWR and the secondary drive unit DU2 to drive the front wheels FWR.

Furthermore, in the above-described embodiment, the main drive unit DU1 is the main drive source for the vehicle V, and the secondary drive unit DU2 is the auxiliary drive source. However, the main drive unit DU1 may be the auxiliary drive source, and the secondary drive unit DU2 may be the main drive source for the vehicle V. In other words, a relatively large motor may be used as the secondary drive motor MOT2, while a motor smaller in size than the secondary drive motor MOT2 may be used as the main drive motor MOT1.

In addition, in the above-described embodiment, the main drive unit DU1 is a so-called "coaxial" hybrid mechanism, but this is not limited to this. For example, the main drive unit DU1 may be a so-called "parallel-axis" hybrid mechanism. Below, with reference to Figure 9, an example of a case in which the main drive unit DU1 is a parallel-axis hybrid mechanism will be described. Note that the following description will focus on differences from the above-described embodiment, and explanations and illustrations of parts common to the above-described embodiment will be omitted as appropriate.

[Modification of the main drive unit]
As shown in Fig. 9, the main drive unit DU1 of this modified example includes an engine ENG, a generator GEN, a main drive motor MOT1, a first transmission mechanism T1, and a case 11 that houses the generator GEN, main drive motor MOT1, and first transmission mechanism T1. The main drive motor MOT1 and generator GEN are connected to a battery BAT via a voltage control unit VCU, a first inverter INV1, and a second inverter INV2, all of which are not shown in Fig. 9, and are capable of receiving power from the battery BAT and regenerating energy into the battery BAT.

[First transmission mechanism]
The case 11 is provided with, from the engine ENG side along the axial direction, a transmission housing chamber 11a that houses the first transmission mechanism T1, and a motor housing chamber 11b that houses the main drive motor MOT1 and the generator GEN.

The transmission housing 11a houses an input shaft 210, a generator shaft 230, a motor shaft 250, and a counter shaft 270, which are arranged parallel to one another, as well as a differential mechanism D (e.g., a first differential mechanism D1).

The input shaft 210 is arranged coaxially with the crankshaft 12 of the engine ENG. The driving force of the crankshaft 12 is transmitted to the input shaft 210 via a damper (not shown). The input shaft 210 is provided with a generator drive gear 320 that constitutes the generator gear train Gg.

On the input shaft 210, a low-speed drive gear 340 that forms a low-speed engine gear train GLo via a first clutch CL1 is provided on the engine side relative to the generator drive gear 320, and a high-speed drive gear 360 that forms a high-speed engine gear train GHi is provided on the opposite side from the engine side (hereinafter referred to as the motor side). The first clutch CL1 is a hydraulic clutch that releasably connects the input shaft 210 and the low-speed drive gear 340, and is a so-called multi-plate friction clutch.

The generator shaft 230 is provided with a generator driven gear 400 that meshes with the generator drive gear 320. The generator drive gear 320 of the input shaft 210 and the generator driven gear 400 of the generator shaft 230 form a generator gear train Gg that transmits the rotation of the input shaft 210 to the generator shaft 230. A generator GEN is disposed on the motor side of the generator shaft 230. The generator GEN comprises a rotor R fixed to the generator shaft 230 and a stator S fixed to the case 11 and positioned opposite the outer diameter side of the rotor R.

The rotation of the input shaft 210 is transmitted to the generator shaft 230 via the generator gear train Gg, and the rotation of the generator shaft 230 rotates the rotor R of the generator GEN. As a result, when the engine ENG is running, the power of the engine ENG input from the input shaft 210 can be converted into electric power by the generator GEN.

The motor shaft 250 is provided with a motor drive gear 520 that constitutes the motor gear train Gm. The main drive motor MOT1 is disposed on the motor shaft 250, closer to the motor than the motor drive gear 520. The main drive motor MOT1 is comprised of a rotor R fixed to the motor shaft 250 and a stator S fixed to the case 11 and positioned opposite the outer diameter side of the rotor R.

On the countershaft 270, in order from the engine side, are provided a low-speed driven gear 600 that meshes with the low-speed drive gear 340, an output gear 620 that meshes with the ring gear 700 of the differential mechanism D, a high-speed driven gear 640 that meshes with the high-speed drive gear 360 of the input shaft 210 via the second clutch CL2, and a motor driven gear 660 that meshes with the motor drive gear 520 of the motor shaft 250. The second clutch CL2 is a hydraulic clutch that releasably connects the countershaft 270 and the high-speed driven gear 640, and is a so-called multi-plate friction clutch.

The low-speed drive gear 340 of the input shaft 210 and the low-speed driven gear 600 of the countershaft 270 form a low-speed engine gear train GLo for transmitting the rotation of the input shaft 210 to the countershaft 270. The high-speed drive gear 360 of the input shaft 210 and the high-speed driven gear 640 of the countershaft 270 form a high-speed engine gear train GHi for transmitting the rotation of the input shaft 210 to the countershaft 270. The low-speed engine gear train GLo, which includes the low-speed drive gear 340 and the low-speed driven gear 600, has a larger reduction ratio than the high-speed engine gear train GHi, which includes the high-speed drive gear 360 and the high-speed driven gear 640.

Therefore, by engaging the first clutch CL1 and disengaging the second clutch CL2 when the engine ENG is running, the driving force of the engine ENG is transmitted to the countershaft 270 via the low-speed engine gear train GLo at a large reduction ratio. On the other hand, by disengaging the first clutch CL1 and engaging the second clutch CL2 when the engine ENG is running, the driving force of the engine ENG is transmitted to the countershaft 270 via the high-speed engine gear train GHi at a small reduction ratio. Note that the first clutch CL1 and second clutch CL2 are never engaged at the same time.

The motor drive gear 520 of the motor shaft 250 and the motor driven gear 660 of the counter shaft 270 form a motor gear train Gm for transmitting the rotation of the motor shaft 250 to the counter shaft 270. When the rotor R of the main drive motor MOT1 rotates, the rotation of the motor shaft 250 is transmitted to the counter shaft 270 via the motor gear train Gm. As a result, when the main drive motor MOT1 is driven, the driving force of the main drive motor MOT1 is transmitted to the counter shaft 270 via the motor gear train Gm.

Furthermore, the output gear 620 of the countershaft 270 and the ring gear 700 of the differential mechanism D constitute a final gear train Gf for transmitting the rotation of the countershaft 270 to the differential mechanism D. Therefore, the driving force of the main drive motor MOT1 input to the countershaft 270 via the motor gear train Gm, the driving force of the engine ENG input to the countershaft 270 via the low-speed engine gear train GLo, and the driving force of the engine ENG input to the countershaft 270 via the high-speed engine gear train GHi are transmitted to the differential mechanism D via the final gear train Gf and from the differential mechanism D to the axles DS. As a result, the driving force required for the vehicle V to travel is output via a pair of drive wheels DW (e.g., front wheels FWR) provided at both ends of the axles DS.

The main drive unit DU1 configured in this manner has a power transmission path that transmits the driving force of the main drive motor MOT1 to the axles DS (i.e., the drive wheels DW), a low-speed power transmission path that transmits the driving force of the engine ENG to the axles DS, and a high-speed power transmission path that transmits the driving force of the engine ENG to the axles DS.

Therefore, a vehicle V equipped with a main drive unit DU1 configured in this manner can operate in either an electric drive mode (EV driving or series driving) in which the driving force of the main drive motor MOT1 is output as the main driving force, or an engine drive mode in which the driving force of the engine ENG is output as the main driving force. The engine drive modes include low-speed engine driving in which the first clutch CL1 is engaged and the second clutch CL2 is disengaged, thereby transmitting the driving force of the engine ENG to the drive wheels DW via the low-speed power transmission path, and high-speed engine driving in which the first clutch CL1 is disengaged and the second clutch CL2 is engaged, thereby transmitting the driving force of the engine ENG to the drive wheels DW via the high-speed power transmission path.

It is also possible to omit one of the low-speed and high-speed power transmission paths in the main drive unit DU1, and in engine drive mode, the driving force of the engine ENG is transmitted to the drive wheels DW via the other power transmission path that is not omitted.

In addition, in the above-described embodiment, an example of applying the present invention to a vehicle V that is a hybrid electric vehicle has been described, but the present invention is not limited to this. The present invention can also be applied to hybrid electric vehicles such as battery electric vehicles and fuel cell electric vehicles.

This specification and other documents describe at least the following. The components and other elements corresponding to those in the above-mentioned embodiments are shown in parentheses, but are not limited to these.

(1) a battery (battery BAT);
a voltage control unit (voltage control unit VCU) that outputs a boosted voltage obtained by boosting the output voltage of the battery;
a main drive unit (main drive unit DU1) having a main drive motor (main drive motor MOT1) driven by the power of the boosted voltage output from the voltage control unit, and outputting a main drive force to drive one of a front wheel (front wheel FWR) and a rear wheel (rear wheel RWR);
a slave drive unit (slave drive unit DU2) that has a slave drive motor (slave drive motor MOT2) driven by the power of the boosted voltage output from the voltage control unit and outputs a slave drive force that drives the other of the front wheels and the rear wheels;
a control unit (control unit CTR) that controls the voltage control unit, the main drive unit, and the slave drive unit;
A vehicle (vehicle V) comprising:
The control unit
the required driving force of the vehicle is distributed between the main driving force and the secondary driving force in accordance with a predetermined distribution ratio, and when the temperature of the main drive unit is equal to or higher than a predetermined value, the main driving force is made smaller and the secondary driving force is made larger than when the temperature is below the predetermined value;
the boost voltage when the temperature is equal to or higher than the predetermined value is set to a second boost voltage that is more suitable for driving the slave drive motor than a first boost voltage that is the boost voltage when the temperature is lower than the predetermined value;
vehicle.

According to (1), when the secondary drive force is increased as a result of the temperature of the main drive unit reaching or exceeding a predetermined value, the boost voltage of the voltage control unit is set to a second boost voltage suitable for driving the secondary drive motor. This makes it possible to drive the secondary drive motor more efficiently and run the vehicle compared to when the boost voltage of the voltage control unit is maintained at the first boost voltage even when the temperature of the main drive unit is reaching or exceeding a predetermined value. This therefore improves the energy efficiency of the vehicle.

(2) The vehicle according to (1),
The second boost voltage is a voltage that increases the driving force that the slave drive motor can output at the current vehicle speed compared to the first boost voltage.
vehicle.

According to (2), the second boost voltage is a voltage that increases the driving force that the secondary drive motor can output at the current vehicle speed compared to the first boost voltage. Therefore, even if the primary driving force is reduced when the temperature of the primary drive unit exceeds a predetermined value, it is easy to ensure the vehicle's required driving force by the sum of the primary driving force and the secondary driving force.

(3) The vehicle according to (1) or (2),
the second boosted voltage is a voltage that can reduce loss in the slave drive motor more than the first boosted voltage;
vehicle.

According to (3), the second boost voltage is a voltage that can reduce losses in the slave drive motor more than the first boost voltage, so when the slave drive force is increased as the temperature of the main drive unit reaches or exceeds a predetermined value, it becomes possible to drive the slave drive motor efficiently.

(4) A vehicle according to any one of (1) to (3),
the first boosted voltage is a voltage more suitable for driving the main drive motor than the second boosted voltage;
vehicle.

According to (4), the first boost voltage is a voltage more suitable for driving the main drive motor than the second boost voltage, making it possible to drive the main drive motor efficiently when the temperature of the main drive unit is below a predetermined value.

(5) A vehicle according to any one of (1) to (4),
The control unit
When the temperature reaches or exceeds the predetermined value, the main driving force is reduced by a difference (Δf) between a driving force (f1) that the slave driving motor can output at the current vehicle speed when power of the first boosted voltage is supplied and a driving force (f2) that the slave driving motor can output at the current vehicle speed when power of the second boosted voltage is supplied.
vehicle.

(5) According to this, the main driving force can be reduced while ensuring the vehicle's required driving force.

BAT Battery CTR Control unit DU1 Main drive unit DU2 Sub drive unit FWR Front wheels RWR Rear wheels MOT1 Main drive motor (main drive motor)
MOT2 Slave drive motor (motor for slave drive)
VCU Voltage control unit V Vehicle

Claims (5)

A battery,
a voltage control unit that outputs a boosted voltage obtained by boosting the output voltage of the battery;
a main drive unit having a main drive motor driven by the power of the boosted voltage output from the voltage control unit, and outputting a main drive force for driving one of the front wheels and the rear wheels;
a secondary drive unit having a secondary drive motor driven by the power of the boosted voltage output from the voltage control unit, and outputting a secondary drive force that drives the other of the front wheels and the rear wheels;
a control unit that controls the voltage control unit, the main drive unit, and the slave drive unit;
A vehicle comprising:
The control unit
the required driving force of the vehicle is distributed between the main driving force and the secondary driving force in accordance with a predetermined distribution ratio, and when the temperature of the main drive unit is equal to or higher than a predetermined value, the main driving force is made smaller and the secondary driving force is made larger than when the temperature is below the predetermined value;
the boost voltage when the temperature is equal to or higher than the predetermined value is set to a second boost voltage that is more suitable for driving the slave drive motor than a first boost voltage that is the boost voltage when the temperature is lower than the predetermined value;
vehicle. 2. The vehicle according to claim 1,
The second boost voltage is a voltage that increases the driving force that the slave drive motor can output at the current vehicle speed compared to the first boost voltage.
vehicle. 3. A vehicle according to claim 1 or 2,
the second boosted voltage is a voltage that can reduce loss in the slave drive motor more than the first boosted voltage;
vehicle. A vehicle according to any one of claims 1 to 3,
the first boosted voltage is a voltage more suitable for driving the main drive motor than the second boosted voltage;
vehicle. A vehicle according to any one of claims 1 to 4,
The control unit
When the temperature reaches or exceeds the predetermined value, the main driving force is reduced by the difference between the driving force that the slave drive motor can output at the current vehicle speed when power of the first boosted voltage is supplied and the driving force that the slave drive motor can output at the current vehicle speed when power of the second boosted voltage is supplied.
vehicle.