Cooling control system for electric vehicles

Abstract

To provide a control device of a four-wheel driving vehicle which can improve energy efficiency, while suppressing lowering of cooling performance of driving force sources.SOLUTION: There is provided a cooling control device of an electric vehicle, which includes a first electric oil pump for supplying oil to a first motor for driving front wheels, and a second electric oil pump for supplying oil to a second motor for driving rear wheels, and can perform switching between a four-wheel drive traveling mode and a two-wheel drive traveling mode using the second motor as a driving force source, the cooling control device driving only the second electric oil pump when the two-wheel drive traveling mode is selected (step S5), and starting to operate the first electric oil pump when it is predicted that the vehicle travels in the four-wheel drive traveling mode (step S7).SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a control device for cooling a motor or the like in a vehicle equipped with an electric motor (motor) as a driving force source, and particularly to a cooling control device that performs cooling with oil.

Background Art

[0002] Patent Document 1 describes a control device for a four-wheel drive vehicle including a front motor that is a driving force source for a pair of front wheels and a rear motor that is a driving force source for a pair of rear wheels and has a lower thermal rating or lower cooling performance than the front motor. When the operation of the rear motor is restricted, this control device maintains the driving force required for the vehicle by increasing the output of the front motor, and when the operation of the front motor is restricted, it reduces the output of the rear motor to ensure running stability by setting the distribution ratio of the torque between the front and rear wheels to a desired distribution ratio.

[0003] Patent Document 2 describes a hybrid vehicle equipped with an engine and a motor as driving force sources and capable of setting an HV running mode in which the engine is driven to run and an EV running mode in which the engine is stopped and the motor is driven to run. Further, this hybrid vehicle is provided in parallel with a mechanical oil pump driven by the power of the engine and an electric oil pump driven by an electric motor. When the viscosity of the refrigerant discharged by these oil pumps is high, only the oil pump with the higher discharge output of either the mechanical oil pump or the electric oil pump is driven, and when the viscosity of the refrigerant is low, only the other oil pump is driven.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] The four-wheel drive vehicle described in Patent Document 1 can independently drive a pair of front wheels and a pair of rear wheels, so it is possible to drive two wheels by driving only one of the drive sources. Furthermore, since it has multiple drive sources, it is thought that in order to ensure the cooling performance of the drive sources when driving four wheels, multiple cooling oil pumps or one large oil pump will be installed. If multiple oil pumps or a large oil pump are installed in this way, driving each oil pump when driving two wheels will result in power or energy loss for driving the oil pumps, which may reduce the overall energy efficiency of the vehicle.

[0006] This invention was made in view of the above technical problems, and aims to provide a control device for a four-wheel drive vehicle that can improve energy efficiency while suppressing a decrease in the cooling performance of the drive force source. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a four-wheel drive driving mode using the first motor and the second motor as the driving force source, comprising: a first motor for driving a first drive wheel, which is one of the front wheels and the rear wheels; a first electric oil pump for supplying oil to the first motor; a second motor for driving a second drive wheel, which is the other of the front wheels and the rear wheels; a second electric oil pump for supplying the oil to the second motor; a first drive unit for transmitting torque from the first motor to the first drive wheel; a second drive unit for transmitting torque from the second motor to the second drive wheel; and a mechanical oil pump operated by the first drive unit to supply the oil to the first drive unit, wherein the first motor and the second motor are the driving force source. A cooling control device for an electric vehicle that can switch between a two-wheel drive mode using the second motor as a driving force source, comprising a controller that controls the first electric oil pump and the second electric oil pump, wherein the controller comprises a pump selection unit that drives only the second electric oil pump among the first electric oil pump and the second electric oil pump when the two-wheel drive mode is selected, a prediction unit that predicts that the vehicle will be driven in the four-wheel drive mode, and a start control unit that starts operating the first electric oil pump when the prediction unit predicts that the vehicle will be driven in the four-wheel drive mode.

[0008] In the present invention, a mode selection unit is provided which is operated by the driver to select the four-wheel drive driving mode, and the prediction unit may predict that the vehicle will be driven in the four-wheel drive driving mode based on whether or not the mode selection unit is operated.

[0009] In the present invention, the controller may increase the amount of oil supplied to the first motor by the first electric oil pump as the temperature of the first motor increases, and may increase the amount of oil supplied to the second motor by the second electric oil pump as the temperature of the second motor increases.

[0010] In the present invention, the four-wheel drive driving mode includes a plurality of driving modes, and the controller may control the amount of oil supplied to the first motor by the first electric oil pump and the amount of oil supplied to the second motor by the second electric oil pump according to the plurality of driving modes.

[0011] In the present invention, the four-wheel drive driving mode may include at least one of the following driving modes: a track mode which enhances turning performance compared to the two-wheel drive driving mode; a drift mode which improves driving precision; a sport mode which enhances acceleration performance or power performance; and a manual range mode which controls the driving torque of the first motor and the second motor based on the driving characteristics corresponding to the driver's shift operation. [Effects of the Invention]

[0012] According to the present invention, the vehicle is equipped with a first motor that drives a first drive wheel, which is one of the front or rear wheels, and a second motor that drives a second drive wheel, which is the other wheel. When a two-wheel drive mode is set, the second motor is used as the driving force source. That is, since the first motor is not energized, it does not generate heat and does not require cooling. Therefore, by stopping or maintaining the stopped state of the first electric oil pump, which is provided in conjunction with the first motor, the power consumption of the entire electric vehicle can be reduced. In other words, energy efficiency can be improved while suppressing the decrease in the cooling performance of the second motor, which is the driving force source in the two-wheel drive mode. To put it another way, by providing a first electric oil pump that supplies oil only to the first motor, which is stopped when driving in the two-wheel drive mode, the second electric oil pump, which is provided in conjunction with the second motor, only needs to have the function of being able to cool the second motor, and thus the second electric oil pump can be made smaller.

[0013] Furthermore, even when driving in two-wheel drive mode, the first drive wheel rotates, causing the first drive unit to rotate at a speed corresponding to the vehicle speed. In other words, the mechanical oil pump operates. Therefore, oil is supplied to the lubrication points of the first drive unit, which helps to prevent a decrease in the durability of the first drive unit. In other words, since oil is supplied only to the places where it should be supplied, the power loss required to drive the mechanical oil pump can be reduced.

[0014] Furthermore, if it is anticipated that the vehicle will be driven in four-wheel drive mode, the first electric oil pump, which is currently stopped, can be activated to supply oil to the first motor for cooling before it is energized and generates electricity. As a result, the first electric oil pump can be kept running when the vehicle is driven in four-wheel drive mode, thus preventing a decrease in the cooling performance of the first motor. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic block diagram showing the drive system of a four-wheel independent drive vehicle in an embodiment of the present invention. [Figure 2] This is a skeleton diagram showing an example of a rear-wheel drive unit. [Figure 3] This is a skeleton diagram showing an example of a drive unit on the front wheel side. [Figure 4] This diagram schematically shows the required drive torque map used in the D range. [Figure 5] This diagram schematically shows the required drive torque map when the accelerator is open at 50% in D or L range. [Figure 6] This figure shows an example of a shift device that allows the user to select a shift range by operating the shift lever. [Figure 7] This figure shows an example of a shift device that allows the user to select a shift range by operating paddle switches. [Figure 8] This flowchart illustrates an example of control that determines whether or not to switch the shift range. [Figure 9] It is a block diagram illustrating the input / output signals of the controller. [Figure 10] It is a block diagram showing the functional configuration of the controller. [Figure 11] It is a flowchart for explaining an example of control executed in an embodiment of the present invention. [Figure 12] It is a diagram showing an example of a map in which the rotational speed of the oil pump for each driving mode is determined.

Mode for Carrying Out the Invention

[0016] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0017] The electric vehicle targeted in the present invention is a vehicle with a total of four wheels, two front wheels and two rear wheels, and a motor as a driving force source is provided for each of the two front wheels and the two rear wheels, and the two front wheels and the two rear wheels can be driven independently of each other. The two front wheels are connected to the driving force source for the front wheels via an appropriate differential mechanism, and the two rear wheels may be connected to the driving force source for the rear wheels via another appropriate differential mechanism. Furthermore, the electric vehicle targeted in the present invention may be an electric vehicle configured to be provided with a motor as a driving force source corresponding to each of the four front and rear wheels so that the driving torque and regenerative braking torque (regenerative torque) of each of the four wheels can be controlled independently of each other.

[0018] Figure 1 schematically shows an example of a four-wheel independent drive vehicle, which is configured to allow independent control of the driving torque or regenerative braking torque of the front and rear wheels, as well as to allow all four wheels to be driven independently. The electric vehicle shown here (hereinafter simply referred to as "vehicle") Ve has left and right front wheels 1r, 1l and left and right rear wheels 2r, 2l, and drive units Pf, Pr are provided as driving force sources corresponding to the front wheels 1r, 1l and the rear wheels 2r, 2l, respectively. These drive units Pf, Pr are mainly composed of a motor and a gear reduction mechanism (transmission mechanism), respectively.

[0019] Figure 2 shows a skeleton diagram of an example of the drive unit Pr for the rear wheels 2r and 2l. This drive unit Pr consists of a pair of drive systems that independently control the left and right rear wheels 2r and 2l. Since these drive systems are symmetrically configured, they will be described together without specifically referring to them as "right" or "left". In the following explanation, if the subscript (suffix) of the reference symbol is one letter, "f" indicates the front wheel, "l" indicates the left wheel, and "r" indicates the right wheel or rear wheel. If there are two letters, the first letter "f" indicates the front wheel, "r" indicates the rear wheel, the second letter "r" indicates the right wheel, and "l" indicates the left wheel.

[0020] The drive unit Pr for the rear wheels 2r and 2l has motors Mrr and Mrl mounted with their rotational axis oriented in the longitudinal direction of the vehicle Ve. Drive gears 3rr and 3rl are attached to the rotor shafts of these motors, and these drive gears 3rr and 3rl mesh with counter-driven gears 4rr and 4rl. The counter-driven gears 4rr and 4rl have a larger diameter than the drive gears 3rr and 3rl, and therefore these gear pairs constitute a reduction mechanism. Counter-drive gears 5rr and 5rl, which are bevel gears, are mounted on the same axis as the counter-driven gears 4rr and 4rl so as to rotate together. These counter-drive gears 5rr and 5rl mesh with driven gears 7rr and 7rl, which are bevel gears integrated with the drive shafts 6rr and 6rl connected to the rear wheels 2r and 2l. By making the driven gears 7rr and 7rl have a larger diameter than the counter-drive gears 5rr and 5rl, these gear pairs can be used as a reduction mechanism.

[0021] These rear wheels 2r and 2l correspond to the "second drive wheels" in the embodiment of the present invention, their motors Mrr and Mrl correspond to the "second motors" in the embodiment of the present invention, and the part that transmits torque from these motors Mrr and Mrl to the rear wheels 2r and 2l corresponds to the "second drive unit" in the embodiment of the present invention.

[0022] These motors Mrr, Mrl, reduction gears, and bevel gears are housed in a liquid-tight state inside the casing 8. Electric oil pumps OPrr, OPrl are provided to supply oil for cooling and lubrication to the motors Mrr, Mrl inside the casing 8. The oil pumps on the rear wheel 2r, 2l sides may be a single oil pump that supplies oil 10r to both the left and right motors Mrr, Mrl collectively. These oil pumps OPrr, OPrl are located outside the casing 8 at appropriate locations on the vehicle Ve, and are configured to draw oil 10r from an oil reservoir 9r and supply it to the motors Mrr, Mrl via cooling oil passages 11rr, 11rl that penetrate the casing 8.

[0023] Although not specifically shown in the diagram, the casing 8 is configured to recirculate oil 10r from inside to the oil reservoir 9r. An oil cooler may also be provided in the middle of the cooling oil passages 11rr and 11rl. These oil pumps OPrr and OPrl correspond to the "second electric oil pump" in the embodiment of the present invention.

[0024] Figure 3 shows a skeleton diagram of an example of the drive unit Pf on the front wheel 1r, 1l side. Since this drive unit Pf has a symmetrical configuration, it will be described together without specifically designating it as "right" or "left". Motors Mfr and Mfl are mounted with their rotational axis oriented in the width direction (lateral direction) of the vehicle Ve, and drive gears 12fr and 12fl are attached to their rotor shafts, and these drive gears 12fr and 12fl mesh with idler gears 13r and 13l. Counter shafts 14r and 14l are provided parallel to the rotational axis of these idler gears 13r and 13l, and the idler gears 13r and 13l mesh with counter driven gears 15fr and 15fl attached to these counter shafts 14r and 14l.

[0025] The counter-driven gears 15fr and 15fl are larger in diameter than the drive gears 12fr and 12fl attached to the motors Mfr and Mrl, and these gear pairs constitute a reduction mechanism. The counter-drive gears 16fr and 16fl are attached to the counter shafts 14r and 14l, and these counter-drive gears 16fr and 16fl mesh with the driven gears 18fr and 18fl, which are integrated with the drive shafts 17fr and 17fl connected to the front wheels 1r and 1l. The driven gears 18fr and 18fl are larger in diameter than the counter-drive gears 16fr and 16fl, and these gear pairs constitute a reduction mechanism.

[0026] These front wheels 1r and 1l correspond to the "first drive wheels" in the embodiments of the present invention, their motors Mfr and Mfl correspond to the "first motors" in the embodiments of the present invention, and the part that transmits torque from these motors Mfr and Mfl to the front wheels 1r and 1l corresponds to the "first drive unit" in the embodiments of the present invention.

[0027] The motors Mfr and Mfl on the front wheels 1r and 1l are configured to be cooled by oil 10f, similar to the motors Mrr and Mrl on the rear wheels 2r and 2l. Specifically, electric oil pumps OPfr and OPfl are provided corresponding to the motors Mfr and Mfl on the front wheels 1r and 1l, and these oil pumps OPfr and OPfl are configured to draw oil 10f from the oil reservoir 9f and supply the oil 10f to the motors Mfr and Mfl via the cooling oil passages 19fr and 19fl.

[0028] Although not specifically shown in the diagram, the oil used to cool the motors Mfr and Mfl is configured to recirculate into the oil reservoir 9r. An oil cooler may also be provided in the middle of the cooling oil passages 19fr and 19fl. The oil pumps on the front wheels 1r and 1l may be a single oil pump that supplies oil 10f to both the left and right motors Mfr and Mfl at once, similar to the oil pumps on the rear wheels 2r and 2l described above. These oil pumps OPfr and OPfl correspond to the "first electric oil pump" in the embodiment of the present invention.

[0029] An oil pump OPm is provided to pump up oil for lubrication. This oil pump OPm is a mechanical pump and, in the example shown in Figure 3, is connected to the countershaft 14l on the left front wheel 1l side. Therefore, this oil pump OPm is driven when the vehicle Ve is running, and is configured to pump oil 10f from the oil reservoir 9f and to supply oil 10f to predetermined lubrication points such as gears and bearings provided in the drive unit Pf on the front wheel 1r,1l side.

[0030] A power storage device (Bat) 20 is provided to exchange power with each of the motors Mfr, Mfl, Mrr, Mrl and the oil pumps OPfr, OPfl, OPrr, OPrl. This power storage device 20 is mainly composed of secondary batteries such as lithium-ion batteries and solid-state batteries. Each of the motors Mfr, Mfl, Mrr, Mrl is, for example, a permanent magnet type synchronous motor, and these motors Mfr, Mfl, Mrr, Mrl are connected to the power storage device 20 via power controllers PCfr, PCfl, PCrr, PCrl, which are mainly inverters. Therefore, the output torque and braking torque of each motor Mfr, Mfl, Mrr, Mrl during energy regeneration are controlled independently of each other. Note that the power controllers PCfr, PCfl, PCrr, PCrl only need to have independent functions and may be configured as a single unit.

[0031] As described above, the vehicle Ve can independently control the output torque of each motor Mfr, Mfl, Mrr, and Mrl. Therefore, for example, it can switch between a two-wheel drive mode in which motors Mrr and Mrl are controlled as the driving force source and power to motors Mfr and Mfl is turned off, and a four-wheel drive mode in which each motor Mfr, Mfl, Mrr, and Mrl are controlled as the driving force source. Furthermore, when driving in four-wheel drive mode, the ratio of the output torque of the front and rear motors can be appropriately changed based on the driving characteristics required by the driver.

[0032] A mode selection switch (mode selection unit) 21 is provided on the vehicle Ve for the driver to select a driving characteristic (driving mode). Specifically, the driving modes are control modes that control the drive torque based on predetermined criteria, and include a track mode that improves cornering performance by controlling the drive torque and regenerative torque (braking torque) of each motor Mfr, Mfl, Mrr, Mrl; a drift mode that improves agility and driving precision during cornering by individually controlling the torque of each of the four wheels to eliminate understeer or control to optimal traction; and a manual sport mode that improves acceleration performance or power performance by controlling the gear ratio to secure a large drive torque up to high vehicle speeds. Since these driving modes control the balance of torque between the front and rear wheels or output a large drive torque, they correspond to a four-wheel drive driving mode that drives all motors Mfr, Mfl, Mrr, Mrl.

[0033] The system is configured to allow the user to select one of these driving modes using the mode selection switch 21, or to deselect a mode and select the normal mode. The mode selection switch 21 may be provided in multiple locations corresponding to different driving modes, or it may be configured to use a single mode selection switch that cycles through the selected driving modes based on the number of times it is operated.

[0034] Furthermore, the vehicle Ve shown in Figure 1 is configured to allow the driver to set a manual range mode that changes the drive characteristics, which are the relationship between accelerator pedal input and required drive torque, according to the driver's shift operation. This manual range mode is configured to allow the driver to select from four shift ranges, for example, D range, 3 range, 2 range, and L range (or 1 range).

[0035] Figure 4 shows an example of a drive torque map for determining the required drive torque when the D range is selected. In Figure 4, the horizontal axis represents vehicle speed, and the vertical axis represents the required drive torque, with each accelerator opening shown as a curve. In other words, the larger the accelerator opening, the larger the required drive torque, and the higher the vehicle speed, the smaller the required drive torque. Thus, a drive torque map for determining the required drive torque according to the accelerator opening and vehicle speed is defined for each selected shift range.

[0036] Furthermore, Figure 5 shows the required drive torque set when the accelerator opening is 50%, in order to illustrate the difference in required drive torque for each shift range. In Figure 5, the horizontal axis represents vehicle speed and the vertical axis represents required drive torque. Each curve, from bottom to top in Figure 5, shows the required drive torque set when the D range, 3 range, 2 range, and L range are selected. In other words, the drive torque map corresponding to each shift range is defined so that the required drive torque increases as the shift range changes from the D range to the L range.

[0037] The above-mentioned shift range selection may be configured to be performed by operating a shift lever located on the floor or center console, or by operating a shift switch such as a paddle switch located on the instrument panel, steering wheel, or steering column.

[0038] Figure 6 shows an example of the configuration of a shift device 22 that selects a shift range by operating a shift lever. The shift device 22 shown in Figure 6 has a configuration similar to existing shift devices used in vehicles equipped with conventional automatic transmissions (multi-speed transmissions), and is configured to select D position, N position, R position, and P position by moving the shift lever 22b at the shift gate 22a shown on the left side of Figure 6. Furthermore, the shift device 22 is configured to select manual range mode by moving the shift lever 22b from the D position to the shift gate 22c shown on the right side of Figure 6. The movement of the shift lever 22b to the shift gate 22c shown on the right side of Figure 6 is detected by a neutral position detection switch 23 provided on the shift gate 22c.

[0039] In manual range mode, moving the shift lever 22b to the up (+) side at the shift gate 22c shifts the gear by one step to a range where the required drive torque decreases. In other words, a range switch equivalent to an upshift in a conventional transmission is performed. On the other hand, moving the shift lever 22b to the down (-) side shifts the gear by one step to a range where the required drive torque increases. In other words, a range switch equivalent to a downshift in a conventional transmission is performed.

[0040] Figure 7 shows an example of the configuration of a shift device 22 that selects a shift range by operating paddle switches. In the example shown in Figure 7, a paddle switch 25 is provided on the steering wheel 24, similar to existing paddle switches used in vehicles equipped with conventional automatic transmissions (multi-speed transmissions). When manual range mode is selected by the shift device 22, etc., operating the paddle switch (UP switch) 25a once (turning it ON) shifts the gear by one step to a range in the direction of decreasing required drive torque. In other words, a range switch equivalent to an upshift in a conventional transmission is performed. Also, when manual range mode is selected by the shift device 22, etc., operating the paddle switch (DOWN switch) 25b shown in Figure 7 once (turning it ON) shifts the gear by one step to a range in the direction of increasing required drive torque. In other words, a range switch equivalent to a downshift in a conventional transmission is performed.

[0041] The above-mentioned change in the shift range is configured such that, similar to vehicles equipped with conventional automatic transmissions, the controller 26, described later, determines whether or not to switch the shift range based on signals input from the shift device 22 to the controller 26. An example of the control that determines whether or not to switch the shift range will be briefly explained with reference to the flowchart shown in Figure 8. In the control example shown in Figure 8, first, it is determined whether or not manual range mode is selected by the shift device 22, that is, whether or not manual operation is performed (step S1), and if manual operation is performed, a switch signal is received due to the operation of the shift lever 22b or paddle switch 25 (step S2).

[0042] Next, the system selects a desired shift range by operating the shift lever 22b or paddle switch 25, and retrieves a drive torque map corresponding to the selected desired shift range (step S3). Then, by referring to the retrieved drive torque map, the system calculates the desired drive torque from the current vehicle speed and accelerator opening, and determines whether the calculated desired drive torque is greater than or equal to the sum of the maximum torques of all motors Mfr, Mfl, Mrr, and Mrl, and whether the desired drive torque can be output at the current vehicle speed (step S4). If the desired drive torque can be output, the system switches the shift range (step S5), and if the desired drive torque cannot be output, the system rejects the shift range switch (step S6). If no manual operation is performed, the system terminates this routine.

[0043] Therefore, in manual range mode, if the shift range can be switched according to the driver's shift operation, for example, if the shift is changed from D range to L range in a very short time, the required drive torque will increase sharply. Also, since manual range mode is usually selected when a relatively large drive torque is required, the accelerator opening may increase after switching to manual range mode, which may increase the required drive torque. For this reason, when manual range mode is selected, the vehicle is configured to drive all motors Mfr, Mfl, Mrr, and Mrl. In other words, manual range mode is equivalent to four-wheel drive mode.

[0044] A controller 26 is provided for controlling each motor Mfr, Mfl, Mrr, Mrl and each electric oil pump OPrl, OPrr, OPfl, OPfr based on the aforementioned driving mode and shift range. The controller 26 is mainly composed of a microcomputer and is configured to perform calculations according to a predetermined program using input data and pre-stored data, and to output the results of these calculations as control command signals to the aforementioned motors Mfr, Mfl, Mrr, Mrl and electric oil pumps OPrl, OPrr, OPfl, OPfr.

[0045] Figure 9 shows examples of input and output signals for performing this type of control. Examples of input signals include vehicle speed signal, accelerator opening signal, shift position signal, driving mode selection switch signal, shift up (+) signal, shift down (-) signal, neutral position detection switch signal, track mode signal, and drift mode signal. Examples of output command signals include the torque of motor Mrl for the left rear wheel 2l, the torque of motor Mrr for the right rear wheel 2r, the control signal for oil pump OPrl for the left rear wheel 2l, the control signal for oil pump OPrr for the right rear wheel 2r, the torque of motor Mfl for the left front wheel 1l, the torque of motor Mfr for the right front wheel 1r, the control signal for oil pump OPfl for the left front wheel 1l, and the control signal for oil pump OPfr for the right front wheel 1r.

[0046] In the aforementioned vehicle Ve, when the two-wheel drive mode is selected, motors Mrr and Mrl are driven, and power to motors Mfr and Mfl is cut off. Therefore, in order to reduce the power consumption of vehicle Ve, the oil pump OPrl for the left rear wheel 2l and the oil pump OPrr for the right rear wheel 2r are activated, while the oil pump OPfl for the left front wheel 1l and the oil pump OPfr for the right front wheel 1r are stopped. On the other hand, when the four-wheel drive mode is selected, each motor Mfr, Mfl, Mrr, and Mrl are driven. Therefore, in order to cool each motor Mfr, Mfl, Mrr, and Mrl, the electric oil pumps OPrl, OPrr, OPfl, and OPfr are activated. Accordingly, the controller 26 is configured to start activating the oil pump OPfl for the left front wheel 1l and the oil pump OPfr for the right front wheel 1r when a switch to four-wheel drive mode is predicted while the vehicle is driving in two-wheel drive mode.

[0047] Figure 10 shows an example of a functional configuration for controlling each of the electric oil pumps OPrl, OPrr, OPfl, and OPfr in the controller 26. In the example shown in Figure 10, it is composed of a pump selection unit 27, a prediction unit 28, and a start control unit 29. The pump selection unit 27 is configured to select the oil pump OPrl for the left rear wheel 2l and the oil pump OPrr for the right rear wheel 2r as the electric oil pumps to be driven when the two-wheel drive driving mode is selected. The prediction unit 28 is configured to predict whether the vehicle will be driving in four-wheel drive mode based on the on / off signal of the mode selection switch 21 and the switch signal of the shift device 22. Furthermore, the start control unit 29 is configured to start operating the stopped electric oil pumps (oil pump OPfl for the left front wheel 1l and oil pump OPfr for the right front wheel 1r) when it is predicted that the vehicle will be driving in four-wheel drive mode.

[0048] An example of control by this controller 26 will be explained with reference to the flowchart shown in Figure 11. In the control example shown in Figure 11, input data is first acquired in step S1. The input data acquired here includes accelerator opening, vehicle speed, motor temperature, oil temperature, shift range, and driving mode. Next, it is determined whether the four-wheel drive driving mode is selected or set. Specifically, it is determined whether the aforementioned track mode is selected or set (step S2), whether the drift mode is selected or set (step S3), or whether the manual sport mode is selected or set (step S4). Steps S2 to S4 can be determined based on the signals input to the controller 26 from the mode selection switch 21. Note that the order of these determinations is not particularly limited and may be as appropriate.

[0049] Furthermore, as mentioned above, it is preferable to drive in four-wheel drive mode. Therefore, in addition to steps S2 to S4 above, it may be determined whether or not manual range mode is selected or set.

[0050] The aforementioned track mode, drift mode, and manual sport mode are driving modes selected in special environments such as circuit driving. Therefore, under normal circumstances, none of the above driving modes are selected, and the result of the judgment in step S2 or step S4 is "no". In that case, the normal mode, which is two-wheel drive driving mode, is required, or the two-wheel drive driving mode is set and the vehicle is driving, so only the oil pumps OPrr and OPrl, which are provided in accordance with the rear wheels 2r and 2l, are driven to actively supply oil to the motors Mrr and Mrl for the rear wheels 2r and 2l to promote their cooling (step S5). That is, the oil pumps OPfr and OPfl, which are provided in accordance with the front wheels 1r and 1l, are stopped or kept in a stopped state. In that state, drive control is performed using the drive torque of the left and right rear wheels 2r and 2l (step S6). After that, the system returns.

[0051] Here, "using the drive torque of the left and right rear wheels 2r and 2l" means that the drive torque of each rear wheel 2r and 2l is controlled by motors Mrr and Mrl, which are provided corresponding to each rear wheel 2r and 2l.

[0052] When the two-wheel drive mode is set, the motors Mfr and Mfl are not energized, so they do not generate heat and do not require cooling. Therefore, by stopping or maintaining the stopped state of the oil pumps OPfr and OPfl, which are provided for the front wheels 1r and 1l, the overall power consumption of the vehicle Ve can be reduced. In other words, energy efficiency can be improved while suppressing the decrease in cooling performance of the motors Mrr and Mrl, which are the driving force source in the two-wheel drive mode. To put it another way, by providing an electric oil pump that supplies oil only to the motors Mfr and Mfl, which are stopped when driving in two-wheel drive mode, the oil pumps OPrr and OPrl, which are provided for the rear wheels 2r and 2l, only need to have the function of cooling the motors Mrr and Mrl, and thus the oil pumps OPrr and OPrl can be made smaller.

[0053] Furthermore, even when driving in two-wheel drive mode, the front wheels 1r and 1l rotate, causing each rotating component of the drive unit Pf to rotate at a speed corresponding to the vehicle speed. In other words, the mechanical oil pump OPm operates. Therefore, oil is supplied to the lubrication points of the drive unit Pf, thus preventing a decrease in the durability of the drive unit Pf. In other words, since oil is supplied only to the points where it should be supplied, power loss required to drive the oil pump can be reduced.

[0054] On the other hand, if the result of the judgment in step S2 or step S4 is "yes", it is required to drive in four-wheel drive mode or to switch from two-wheel drive mode to four-wheel drive mode. In this case, the oil pumps OPfr, OPfl, OPrr, and OPrl, which are provided corresponding to each of the four front and rear wheels, are driven to actively supply oil to the motors Mfr, Mfl, Mrr, and Mrl to promote their cooling (step S7). In this state, drive control is performed using the drive torque of the four front and rear wheels (step S8). After that, the system returns to its original state.

[0055] Here, "drive control using the drive torque of the four front and rear wheels" refers to a control method that drives the vehicle Ve by individually controlling the motors Mfr, Mfl, Mrr, and Mrl, which are provided in correspondence with each of the front and rear wheels 1r, 1l, 2r, and 2l, and individually controlling the drive torque of each wheel 1r, 1l, 2r, and 2l. The torque distribution ratio between the front and rear wheels and the torque distribution ratio between the left and right wheels are appropriately controlled according to various requirements such as the required drive torque, the gradient angle of the road, and the turning radius.

[0056] The aforementioned track mode, drift mode, or manual sport mode are typically set in special situations such as circuit driving. When the vehicle is stopped in normal mode, the mode selection switch 21 is operated, and then the vehicle is driven by operating the accelerator according to the selected driving mode. In other words, it is required to drive the motors Mfr and Mfl after switching the driving mode. Therefore, in the control example described above, the operation of the mode selection switch 21 is used as a means to predict that the vehicle will be driven in four-wheel drive mode.

[0057] Furthermore, when the mode selection switch 21 is operated as described above and it is predicted that the vehicle will be driven in one of the following driving modes: track mode, drift mode, or manual sport mode, the stopped oil pumps OPfr and OPfl are activated, thereby supplying oil to the motors Mfr and Mfl before they are energized and generate heat, thus allowing them to be cooled. As a result, when driving in four-wheel drive mode, the oil pumps OPfr and OPfl can be kept running, which helps to prevent a decrease in the cooling performance of the motors Mfr and Mfl.

[0058] As described above, when operating each oil pump OPfr, OPfl, OPrr, and OPrl, it is preferable to set the rotational speed of each oil pump OPfr, OPfl, OPrr, and OPrl, that is, the amount of oil supplied to motors Mfr, Mfl, Mrr, and Mrl, according to the temperature of each motor Mfr, Mfl, Mrr, and Mrl. Specifically, it is preferable to set the rotational speed of oil pump OPfr higher the higher the temperature of motor Mfr, the higher the temperature of motor Mfl, the higher the rotational speed of oil pump OPfl, the higher the temperature of motor Mrr, the higher the rotational speed of oil pump OPrr, and the higher the temperature of motor Mrl, the higher the rotational speed of oil pump OPrl.

[0059] By controlling the rotation speed of the oil pumps OPfr, OPfl, OPrr, and OPrl according to the temperature of the motors Mfr, Mfl, Mrr, and Mrl, it is possible to cool the motors Mfr, Mfl, Mrr, and Mrl without excess or deficiency, while also reducing power consumption.

[0060] Furthermore, the required drive torque tends to increase in the order of Track Mode, Drift Mode, Manual Sport Mode, and Manual Range Mode. Therefore, it is preferable to set the rotational speeds of the oil pumps OPfr, OPfl, OPrr, and OPrl to be higher in the order of Track Mode, Drift Mode, Manual Sport Mode, and Manual Range Mode. In other words, it is preferable to store in the controller 26 a map shown in Figure 12 that defines the rotational speeds of the oil pumps OPfr, OPfl, OPrr, and OPrl using the selected driving mode and motor temperature as parameters, and to operate each oil pump OPfr, OPfl, OPrr, and OPrl by referring to that map when driving in four-wheel drive mode.

[0061] By controlling the rotation speed of the oil pumps OPfr, OPfl, OPrr, and OPrl according to the selected driving mode, the motors Mfr, Mfl, Mrr, and Mrl can be cooled appropriately, and power consumption can be reduced.

[0062] In the embodiment of the present invention, the electric vehicle uses the rear wheels 2r and 2l as drive wheels in two-wheel drive mode, but the front wheels 1r and 1l may also be used as drive wheels. In that case, a mechanical oil pump is provided in the drive unit Pr, and the oil pumps OPrr and OPrl should be stopped when in two-wheel drive mode.

[0063] Furthermore, the vehicle Ve may be equipped with mechanical oil pumps in the drive unit Pf and drive unit Pr, in which case the drive wheels during two-wheel drive mode may be appropriately switched between the front wheels 1r,1l and the rear wheels 2r,2l depending on the driving environment. When switching the drive wheels in two-wheel drive mode in this way, it is sufficient to stop the oil pumps OPrr,OPrl (OPfr,OPfl) provided in a drive unit Pr(Pf) that is different from the drive unit Pf(Pr) connected to the drive wheels.

[0064] Furthermore, although the example shown in Figure 2 does not show the oil pump that supplies oil to the lubrication points of the drive unit Pr, the drive unit Pr may be configured to be lubricated as appropriate by providing a mechanical oil pump or the like. Moreover, in the above-mentioned vehicle Ve, whether in two-wheel drive mode or four-wheel drive mode, the rear wheels 2r and 2l function as drive wheels, so the oil pumps OPrr and OPrl may be configured to supply oil to the lubrication points of the drive unit Pr.

[0065] Furthermore, in the control example described above, the system predicts that the vehicle will drive in four-wheel drive mode based on the signal input from the mode selection switch 21 to the controller 26. However, if, for example, the rate of change of the accelerator opening during two-wheel drive driving changes at a predetermined rate, and it is predicted that the required drive torque will increase to a level that cannot be satisfied by the torque of motors Mrr and Mrl alone, the system may also predict that the vehicle will drive in four-wheel drive mode. In other words, the system may predict that the vehicle will drive in four-wheel drive mode based on signals other than those from the mode selection switch 21. [Explanation of Symbols]

[0066] 1r,1l front wheel 2r,2l rear wheel 10f, 10r oil 21 Mode Selection Switch 22 Shift device 22b Shift lever 23. Neutral position detection switch 25 Paddle Switches 26 Controllers 27 Pump Selection Section 28 Prediction Section 29 Startup Control Unit Mfr, Mfl, Mrr, Mrl motor OPfr, OPfl, OPrr, OPrl (electric) oil pump OPm (Mechanical) Oil Pump Pr, Pf drive unit Vehicle

Claims

1. A cooling control device for an electric vehicle comprising: a first motor that drives a first drive wheel, which is one of the front wheels or the rear wheels; a first electric oil pump that supplies oil to the first motor; a second motor that drives a second drive wheel, which is the other of the front wheels or the rear wheels; a second electric oil pump that supplies the oil to the second motor; a first drive unit that transmits torque from the first motor to the first drive wheel; a second drive unit that transmits torque from the second motor to the second drive wheel; and a mechanical oil pump that is operated by the first drive unit to supply the oil to the first drive unit, wherein the device is switchable between a four-wheel drive driving mode using the first motor and the second motor as the driving force source and a two-wheel drive driving mode using the second motor as the driving force source, The system includes a controller that controls the first electric oil pump and the second electric oil pump, The aforementioned controller, When the two-wheel drive driving mode is selected, a pump selection unit drives only the second electric oil pump among the first electric oil pump and the second electric oil pump, A prediction unit that predicts that the vehicle will be driven in the aforementioned four-wheel drive driving mode, The system includes a starting control unit that starts operating the first electric oil pump when the prediction unit predicts that the vehicle will be driven in the four-wheel drive mode. A cooling control device for electric vehicles, characterized by the following features.

2. A cooling control device for an electric vehicle according to claim 1, The system includes a mode selection unit operated by the driver to select the aforementioned four-wheel drive driving mode, The prediction unit predicts that the vehicle will be driven in four-wheel drive mode based on whether or not the mode selection unit has been operated. A cooling control device for electric vehicles, characterized by the following features.

3. A cooling control device for an electric vehicle according to claim 1, The aforementioned controller, The higher the temperature of the first motor, the more the amount of oil supplied to the first motor by the first electric oil pump increases, and the higher the temperature of the second motor, the more the amount of oil supplied to the second motor by the second electric oil pump increases. A cooling control device for electric vehicles, characterized by the following features.

4. A cooling control device for an electric vehicle according to claim 1, The aforementioned four-wheel drive driving mode includes multiple driving modes, The aforementioned controller, The amount of oil supplied to the first motor by the first electric oil pump and the amount of oil supplied to the second motor by the second electric oil pump are controlled according to the plurality of driving modes. A cooling control device for electric vehicles, characterized by the following features.

5. A cooling control device for an electric vehicle according to any one of claims 1 to 4, The four-wheel drive driving mode includes at least one of the following driving modes: a track mode that enhances cornering performance compared to the two-wheel drive driving mode; a drift mode that improves driving precision; a sport mode that enhances acceleration performance or power performance; and a manual range mode that controls the drive torque of the first motor and the second motor based on the drive characteristics corresponding to the driver's shift operation. A cooling control device for electric vehicles, characterized by the following features.

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