JP7322434B2 - left and right wheel drive - Google Patents

Description

The present invention relates to a left and right wheel drive device for driving left and right wheels of a vehicle.

2. Description of the Related Art Conventionally, there has been known a vehicle driving device for driving left and right wheels of a vehicle with an electric motor, in which an oil pump for cooling the electric motor is driven by the electric motor. That is, a mechanical oil pump (mechanical pump) is interposed in the power transmission path of the electric motor, and the electric motor is cooled by cooling oil discharged from the oil pump. The driving force input to such an oil pump increases as the rotation speed of the electric motor increases, and acts to increase the discharge amount of cooling oil. Therefore, it is possible to ensure cooling performance according to the running speed of the vehicle (see Patent Document 1).

Patent No. 5478595

In existing technology, when two electric motors are mounted on a vehicle, one of the electric motors drives the oil pump. On the other hand, since the operation of the oil pump causes a driving loss, the loads and rotation speeds of the two electric motors become unbalanced, and the driving force of each of the left and right wheels may become unstable. In particular, in a left and right wheel drive device equipped with a gear mechanism (differential mechanism or planetary gear mechanism) that amplifies the torque difference between two electric motors and transmits it to each of the left and right wheels, the same torque is generated by the two electric motors. Even so, a steady torque difference occurs between the left and right wheels.

One of the purposes of the present invention is to reduce the unintended torque difference between the left and right wheels in the left and right wheel drive system, which was invented in view of the above problems. In addition to this purpose, it is also possible to achieve actions and effects derived from each configuration shown in the "Mode for Carrying out the Invention" described later and which cannot be obtained with conventional techniques. can be positioned as a goal.

(1) The disclosed left and right wheel drive device includes a first motor and a second motor that drive the left and right wheels of a vehicle, and a torque difference between the first motor and the second motor that is amplified and transmitted to each of the left and right wheels. It is a left and right wheel drive device comprising a gear mechanism for driving. The apparatus includes a mechanical pump connected to a power transmission path between the first motor and the gear mechanism for discharging coolant supplied to the first motor and the second motor.

A calculation unit is provided for calculating a torque loss resulting from the operation of the pump and a torque addition value of the first motor for compensating for the loss torque, based on the rotation speed of the first motor. Further, a control unit is provided for controlling the first motor so as to generate a torque obtained by adding the torque addition value to the required torque of the first motor.

(2) A first refrigerant passage that introduces the refrigerant discharged from the pump to the first motor, and a second refrigerant passage that introduces the refrigerant discharged from the pump to the second motor. preferable. Moreover, it is preferable that the first refrigerant passage has a larger cross-sectional area than the second refrigerant passage.

(3) a first valve interposed in the first refrigerant passage and controlling the flow rate of the refrigerant supplied to the first motor; and a first valve interposed in the second refrigerant passage and supplied to the second motor. and a second valve for controlling the flow rate of the refrigerant. Further, it is preferable that the control unit controls opening degrees of the first valve and the second valve according to a turning state of the vehicle.

(4) The control unit increases the flow rate of the refrigerant supplied to one of the first motor and the second motor that transmits more driving force to the outer turning wheel than to the inner turning wheel, and increases the flow rate of the refrigerant supplied to the other motor. It is preferable to control the opening degrees of the first valve and the second valve so that the flow rate of the refrigerant applied is reduced.

(5) The control unit increases the flow rate of the refrigerant supplied to one of the first motor and the second motor that transmits more driving force to the inner turning wheel than to the outer turning wheel, and supplies the refrigerant to the other motor. It is preferable to control the opening degrees of the first valve and the second valve so that the flow rate of the refrigerant applied is reduced.

In other words, the control unit increases the flow rate of the refrigerant supplied to one of the first motor and the second motor that outputs a larger motor torque (or motor driving force), It is preferable to control the opening degrees of the first valve and the second valve so that the flow rate of the supplied refrigerant is reduced.

By adding the torque loss resulting from the operation of the pump to the required torque of the first motor, it is possible to reduce the unintended torque difference between the left and right wheels.

1 is a schematic diagram for explaining the configuration of a left and right wheel drive device as an embodiment; FIG. FIG. 4 is a nomographic chart showing the relationship between the number of revolutions of a motor and the number of revolutions of left and right wheels. 4 is a graph showing the relationship between motor rotation speed and torque loss. 4 is a flowchart for explaining a motor control procedure; 4 is a flowchart for explaining an example of a valve control procedure; 4 is a flowchart for explaining an example of a valve control procedure;

[1. composition]
Hereinafter, a left and right wheel drive device as an embodiment will be described with reference to the drawings. This device is applied to the AYC device 15 of the vehicle shown in FIG. This AYC device 15 is a vehicle differential device having an AYC (active yaw control) function, and is interposed between the left and right wheels. The AYC function mainly controls the ratio of driving force (driving torque) shared between the left and right drive wheels to adjust the magnitude of the yaw moment, thereby stabilizing the yaw direction of the vehicle. The AYC device 15 of the present embodiment has not only the AYC function, but also the function of transmitting rotational force to the left and right wheels to drive the vehicle, and the function of passively absorbing the difference in the number of revolutions between the left and right wheels that occurs when the vehicle turns. have both.

Inside the AYC device 15, a first motor 1, a second motor 2, and a pump 3 are built. The first motor 1 is arranged on the right side of the vehicle and the second motor 2 is arranged on the left side. These first motor 1 and second motor 2 are AC motors driven by battery power (not shown), and preferably have substantially the same output characteristics. The torque of the left and right drive wheels is variable, and the torque difference between the first motor 1 and the second motor 2 is amplified and transmitted to each of the left and right wheels.

In this embodiment, each of the first motor 1 and the second motor 2 has a right shaft 13 connected to the right wheel and a left shaft 14 connected to the left wheel via a gear mechanism 8 (differential mechanism, planetary gear mechanism, etc.). connected to The first motor 1, the right shaft 13, the left shaft 14, and the second motor 2 are capable of mutually transmitting rotational force. The first motor 1 transmits more driving force to the right shaft 13 than the left shaft 14 , and the second motor 2 transmits more driving force to the left shaft 14 than to the right shaft 13 .

As shown in FIG. 2, the rotational speeds are linearly arranged in the order of "first motor 1, right shaft 13, left shaft 14, second motor 2" on the nomographic chart. Therefore, the rotation speed difference between the left and right drive wheels is proportional to the rotation speed difference between the first motor 1 and the second motor 2 . Further, when the rotation speeds of the first motor 1 and the second motor 2 are the same, the rotation speeds of the left and right drive wheels are also the same. If the loads on the left and right drive wheels are the same, the torque magnitude relationship between the first motor 1 and the second motor 2 is directly reflected in the torque magnitude relationship between the left and right drive wheels.

Next, cooling structures for the first motor 1 and the second motor 2 will be described. As shown in FIG. 1, the first motor 1 is interposed in the first cooling oil passage 4 (first refrigerant passage), and the second motor 2 is interposed in the second cooling oil passage 5 (second refrigerant passage). be. These cooling oil passages 4 and 5 are refrigerant passages through which cooling oil that cools and lubricates the first motor 1 and the second motor 2 circulates. In FIG. 1 , the cooling oil circulates counterclockwise inside the first cooling oil passage 4 and circulates clockwise inside the second cooling oil passage 5 . In addition, sections of the first cooling oil passage 4 and the second cooling oil passage 5 through which the return oil from the first motor 1 and the second motor 2 flow are merged into one.

A pump 3 is interposed in the confluence section of the first cooling oil passage 4 and the second cooling oil passage 5 . The pump 3 is a mechanical pumping device (mechanical pump) that discharges cooling oil (refrigerant) supplied to each of the first motor 1 and the second motor 2 . This pump 3 is connected to the power transmission path between at least the first motor 1 and the gear mechanism 8 . Preferably, the pump 3 is connected to the rotary shaft of the first motor 1 via a reduction gear (not shown). When the pump 3 is connected to the rotation shaft of the motor 1, the number of revolutions of the pump 3 is the same as that of the first motor 1, as shown in the alignment chart of FIG. When the pump 3 is connected to the rotation shaft of the motor 1 through a reduction gear, the rotation speed of the pump 3 is proportional to the rotation speed of the first motor 1, as indicated by the dashed line in FIG. can take the value of

Power for driving the pump 3 is mainly covered by the first motor 1 . As shown in FIG. 3, the relationship between the drive loss torque on the axle derived from the operation of the pump 3 and the rotation speed of the first motor 1 is such that the torque loss increases as the motor rotation speed increases, and the increase The relationship is such that the gradient decreases. Thus, the magnitude of the torque loss caused by driving the pump 3 can be calculated based on the rotation speed of the first motor 1 .

A first valve 6 is interposed in the first cooling oil passage 4 , and a second valve 7 is interposed in the second cooling oil passage 5 . Each valve 6, 7 is arranged near the point where the two cooling oil passages 4, 5 diverge from the confluence section. The first valve 6 is a flow control valve that controls the flow rate of cooling oil supplied to the first motor 1, and the second valve 7 is a flow control valve that controls the flow rate of cooling oil supplied to the second motor 2. valve.

The cross-sectional area of the first cooling oil passage 4 is preferably set to a larger value than the cross-sectional area of the second cooling oil passage 5 . As a result, the first motor 1 is cooled more easily than the second motor 2, and a torque difference resulting from a temperature difference between the motors 1 and 2 is less likely to occur. On the other hand, the flow rate of cooling oil in each of the cooling oil passages 4 and 5 can be controlled by adjusting the opening degrees of the first valve 6 and the second valve 7 . Therefore, the cross-sectional area of the first cooling oil passage 4 may be the same as the cross-sectional area of the second cooling oil passage 5 . In a configuration in which the first valve 6 and the second valve 7 are omitted, the cross-sectional area of the first cooling oil passage 4 should be set larger than the cross-sectional area of the second cooling oil passage 5 .

The operating state of each motor 1 , 2 and each valve 6 , 7 is controlled by a control device 10 . The control device 10 is an electronic control device (computer) that performs control to reduce an unintended torque difference between the left and right wheels. The controller 10 incorporates a processor (central processing unit), a memory (main memory), a storage device (storage), an interface device, etc., and these are connected via an internal bus. Further, an accelerator opening sensor 16, a vehicle speed sensor 17, and a steering angle sensor 18 are connected to the control device 10. FIG.

The accelerator opening sensor 16 is a sensor that detects the depression amount of the accelerator pedal (accelerator opening). A vehicle speed sensor 17 is a sensor that detects the traveling speed (vehicle speed) of the vehicle, and a steering angle sensor 18 is a sensor that detects the steering angle of the steering wheel. The information detected by these sensors 16 to 18 is used to calculate the magnitude of torque and output (that is, required torque, required output, etc.) required for each of the first motor 1 and second motor 2. be done.

If an electronic control unit (AYC-ECU) for controlling the AYC function is installed in the vehicle, the total torque of the left and right drive wheels, the torque difference, the rotation of each motor 1, 2 from this electronic control unit It is also possible to grasp the required torque of each motor 1 and 2 by acquiring information such as the number, current value, voltage value, and frequency. In this case, the sensors 16-18 can be omitted.

Inside the control device 10, as shown in FIG. 1, a calculation unit 11 and a control unit 12 are provided. These elements are shown by classifying the functions of the control device 10 for convenience, and are provided as software executed using the hardware resources of the control device 10 . Each element may be described as an independent program, or may be described as a composite program having multiple functions.

The calculation unit 11 calculates, based on the number of revolutions of the first motor 1, a torque loss (axle driving loss torque) resulting from the operation of the pump 3 and a torque addition value for compensating for this loss. The torque loss can be calculated based on the motor rotation speed of the first motor 1 using a map and formulas such as those shown in FIG. Further, the torque addition value is a value obtained by dividing the torque loss by the reduction gear ratio in the power transmission path from the first motor 1 to the right shaft 13 .

The control unit 12 has a function of controlling the operating states of the first motor 1 and the second motor 2 based on at least the torque addition value calculated by the calculation unit 11 . Here, the first motor 1 is controlled so as to generate torque having a magnitude obtained by adding the torque addition value to the required torque of the first motor 1 . On the other hand, the second motor 2 is controlled so as to generate the required torque of the second motor 2 . Control states of the first motor 1 and the second motor 2 are illustrated below.

As shown in Table 1, in this embodiment, the first motor 1 compensates for the torque loss resulting from the operation of the pump 3 . For example, when the required torque of the second motor 2 is the predetermined value A during straight running, the required torque of the first motor 1 is also set to the predetermined value A in the conventional example. As a result, an axle torque difference is produced by multiplying the on-axle drive loss torque by a torque difference amplification factor (reduction gear ratio in the power transmission path from the pump 3 to the right shaft 13). On the other hand, in this embodiment, in order to make the drive torque difference between the left and right wheels (axle torque difference) 0, a torque equivalent to the sum of the predetermined value A and the torque addition value (axle drive loss torque/reduction gear ratio) is generated by the first motor 1. This reduces at least the unintended torque difference between the left and right wheels. Further, the driving torque difference (axle torque difference) between the left and right wheels becomes zero when the vehicle is traveling straight ahead.

The control unit 12 also has a function of controlling the opening degrees of the first valve 6 and the second valve 7 according to the running state of the vehicle. The opening degrees of the first valve 6 and the second valve 7 are determined by the flow rate of the cooling oil supplied to the one of the first motor 1 and the second motor 2 that transmits more driving force to the turning outer wheel than to the turning inner wheel. controlled to increase. For example, when the vehicle turns to the right, the degree of opening of the second valve 7 is controlled in the opening direction so that the flow rate on the side of the second motor 2 increases. At this time, the opening degree of the first valve 6 is controlled in the closing direction. Preferably, the opening degrees of the first valve 6 and the second valve 7 are controlled so that the flow rate of cooling oil supplied to the first motor 1 is greater than the flow rate of cooling oil supplied to the second motor 2. be done.

Conversely, when the vehicle is left-turning, the opening of the first valve 6 is controlled in the opening direction, and the opening of the second valve 7 is controlled in the closing direction. Preferably, the opening degrees of the first valve 6 and the second valve 7 are controlled so that the flow rate of cooling oil supplied to the first motor 1 is less than the flow rate of cooling oil supplied to the second motor 2. be done. These controls make it difficult for the motors 1 and 2 to generate a torque difference due to the amount of heat generated or the difference in temperature.

When the vehicle is traveling straight ahead, the output of the first motor 1 is slightly larger than the output of the second motor 2. It is conceivable to increase the amount of hydraulic oil slightly larger than that required. However, if the difference in heat value and temperature resulting from the difference in output between the first motor 1 and the second motor 2 is sufficiently small, the first valve 6 and the second valve 7 may be controlled.

[2. flowchart]
FIG. 4 is a flowchart for explaining the control procedure of the motors 1 and 2 by the control device 10. As shown in FIG. This flow is repeatedly executed at predetermined intervals while the motors 1 and 2 are in operation. The calculation unit 11 calculates a loss torque (axle driving loss torque) resulting from the operation of the pump 3 based on the rotation speed of the first motor 1 (step A1).

Further, a torque addition value is calculated by dividing the torque loss by the reduction gear ratio in the power transmission path from the first motor 1 to the right shaft 13 (step A2). After that, the control unit 12 controls the first motor 1 and the second motor 2 so that the torque loss is compensated. At this time, the output of the second motor 2 is controlled as usual so as to generate the required torque. On the other hand, the output of the first motor 1 is controlled so as to generate a torque obtained by adding the torque addition value to the required torque (step A3).

FIG. 5 is a flow chart for explaining the procedure for controlling the valves 6 and 7 by the control device 10. As shown in FIG. This flow is also repeatedly executed at predetermined intervals while the motors 1 and 2 are in operation. Here, the operation states of the valves 6 and 7 are classified into three types [when turning left, when turning right, and when the vehicle is traveling straight or when stopped] according to the turning state of the vehicle. The turning state of the vehicle can be determined based on, for example, the steering angle of the steering wheel and the slip state of the left and right wheels (steps B1 and B2).

During left turning, the opening degrees of the first valve 6 and the second valve 7 are controlled so that the flow rate of cooling oil supplied to the first motor 1 is greater than the flow rate of cooling oil supplied to the second motor 2. (step B3). On the other hand, when turning to the right, the first valve 6 and the second valve 7 are opened so that the flow rate of cooling oil supplied to the second motor 2 is greater than the flow rate of cooling oil supplied to the first motor 1. degree is controlled (step B4). If neither the left turn nor the right turn is made, the flow rate of the cooling oil supplied to the first motor 1 is set to be larger than the flow rate of the cooling oil supplied to the second motor 2, as in step B3. Then, the opening degrees of the first valve 6 and the second valve 7 are controlled (step B5). Such control makes it difficult for a torque difference due to the amount of heat generated or temperature difference between the motors 1 and 2 to occur.

FIG. 6 shows a modification in which the determination conditions in steps B1 and B2 of FIG. 5 are changed. Here, instead of determining the turning direction of the vehicle, the magnitude relationship between the torque output from the first motor 1 (right motor torque) and the torque output from the second motor 2 (left motor torque) is determined. be. At step C1, it is determined whether the left motor torque is smaller than the right motor torque. Conversely, in step C2, it is determined whether the left motor torque is greater than the right motor torque.

For example, even when the vehicle is turning left, the left motor torque may become larger than the right motor torque due to slippage. In such a case, the condition of step C2 is satisfied, and the first valve 6 and the The degree of opening of the second valve 7 is controlled (step C4).

Conversely, the left motor torque may be smaller than the right motor torque during right turning of the vehicle. In such a case, the condition of step C1 is satisfied, and the first valve 6 and The degree of opening of the second valve 7 is controlled (step C3). When the left and right motor torques are the same, the flow rate of cooling oil supplied to the first motor 1 is set to be greater than the flow rate of cooling oil supplied to the second motor 2, as in the control of FIG. Then, the opening degrees of the first valve 6 and the second valve 7 are controlled (step C5). Such control makes it difficult for a torque difference due to the amount of heat generated or temperature difference between the motors 1 and 2 to occur.

[3. effect]
(1) In the above-described embodiment, the torque loss and the torque addition value are calculated based on the rotation speed of the first motor 1, and the torque obtained by adding the torque addition value to the required torque of the first motor 1 is generated. , the first motor 1 is controlled. Thus, by adding the torque loss resulting from the operation of the pump 3 to the required torque of the first motor 1, it is possible to reduce the unintended torque difference between the left and right wheels. Also, when the driving torques of the left and right wheels are the same, the theoretical torque difference can be zero.

(2) By making the cross-sectional area of the first cooling oil passage 4 larger than the cross-sectional area of the second cooling oil passage 5, the flow resistance of the first cooling oil passage 4 can be reduced, and the pump 3 is connected. The first motor 1 being cooled can be made easier to cool than the second motor 2. Therefore, the torque difference resulting from the temperature difference between the motors 1 and 2 can be reduced.

It should be noted that the large cross-sectional area of the first cooling oil passage 4 means that it is advantageous in terms of improving the cooling performance during left turning rather than during right turning. In general, there is not much difference in the frequency of occurrence of right turns and left turns. There is a tendency for the amount of heat generated by the right motor, which transmits a large amount of driving force to the right wheel, which is the turning outer wheel, to increase. Therefore, in countries such as Japan, Australia, the United Kingdom, Southeast Asia, and India, where the left-hand traffic road network is prevalent, by increasing the cross-sectional area of the first cooling oil passage 4, the left and right motors 1, 2 can be efficiently cooled.

(3) By interposing a first valve 6 and a second valve 7 in the first cooling oil passage 4 and the second cooling oil passage 5, and controlling the valve opening according to the running state of the vehicle, each motor 1 , 2, and the left and right motors 1, 2 can be efficiently cooled. Moreover, even if the cross-sectional areas of the first cooling oil passage 4 and the second cooling oil passage 5 are the same, the flow rate of the cooling oil flowing through each of the cooling oil passages 4 and 5 can be freely adjusted.

(4) The valve opening degrees of the first valve 6 and the second valve 7 are set so that the flow rate of the cooling oil supplied to the motors 1 and 2, which transmit more driving force to the outer turning wheel than to the inner turning wheel, increases. controlled by In this way, by increasing the amount of cooling oil to the motors 1 and 2 on the turning outer wheel side, where the temperature tends to rise, the temperature difference between the motors 1 and 2 can be reduced, and the drive torque difference can be reduced. . Therefore, an unintended torque difference between the left and right wheels can be reduced, and torque stability can be enhanced.

(5) Further, the driving torque of the left and right motors 1 and 2 is not always greater on the turning outer wheel side than on the turning inner wheel side. For example, if a slip occurs during turning, the driving torque on the inner turning wheel side may increase and the driving torque on the outer turning wheel side may decrease. may also temporarily increase. In such a case, the temperature difference between the motors 1 and 2 can be reduced by increasing the flow rate of cooling oil supplied to one of the motors 1 and 2 that transmits more driving force to the inner turning wheel than to the outer turning wheel. can reduce the driving torque difference. Therefore, an unintended torque difference between the left and right wheels can be reduced, and torque stability can be enhanced.

[4. Modification]
The above embodiment is merely an example, and there is no intention to exclude various modifications and application of techniques not explicitly described in this embodiment. Each configuration of this embodiment can be modified in various ways without departing from the gist thereof. Also, they can be selected or combined as needed. In the above-described embodiments, the cooling device has been described using cooling oil as a coolant, but the type of coolant is irrelevant. For example, cooling water may be used instead of cooling oil.

1 First Motor 2 Second Motor 3 Pump 4 First Cooling Oil Passage 5 Second Cooling Oil Passage 6 First Valve 7 Second Valve 8 Gear Mechanism 10 Controller 11 Calculator 12 Controller 15 AYC Device

Claims (5)

A left and right wheel drive device comprising a first motor and a second motor for driving left and right wheels of a vehicle, and a gear mechanism for amplifying a torque difference between the first motor and the second motor and transmitting the torque difference to each of the left and right wheels. in
a mechanical pump that is connected to a power transmission path between the first motor and the gear mechanism and that discharges coolant supplied to the first motor and the second motor;
a calculation unit that calculates a torque loss resulting from the operation of the pump and a torque addition value of the first motor for compensating for the loss torque, based on the rotation speed of the first motor;
and a control unit that controls the first motor so as to generate a torque obtained by adding the torque addition value to the required torque of the first motor. a first refrigerant passage that introduces the refrigerant discharged from the pump to the first motor;
a second refrigerant passage that introduces the refrigerant discharged from the pump to the second motor;
2. The left and right wheel drive system according to claim 1, wherein said first coolant passage has a cross-sectional area larger than that of said second coolant passage. a first refrigerant passage that introduces the refrigerant discharged from the pump to the first motor;
a second refrigerant passage that introduces the refrigerant discharged from the pump to the second motor;
a first valve interposed in the first refrigerant passage and controlling the flow rate of the refrigerant supplied to the first motor;
a second valve that is interposed in the second refrigerant passage and controls the flow rate of the refrigerant supplied to the second motor;
3. The left and right wheel drive system according to claim 1, wherein said control unit controls opening degrees of said first valve and said second valve according to a turning state of said vehicle. The control unit increases the flow rate of the refrigerant supplied to one of the first motor and the second motor that transmits more driving force to the outer turning wheel than to the inner turning wheel, and increases the flow rate of the refrigerant supplied to the other motor. 4. The left and right wheel drive system according to claim 3, wherein the opening degrees of said first valve and said second valve are controlled so as to reduce the flow rate of coolant. The control unit increases the flow rate of the refrigerant supplied to one of the first motor and the second motor that transmits more driving force to the inner turning wheel than to the outer turning wheel, and increases the flow rate of the refrigerant supplied to the other motor. 4. The left and right wheel drive system according to claim 3, wherein the opening degrees of said first valve and said second valve are controlled so as to reduce the flow rate of coolant.

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