Vehicle control devices

Abstract

The vehicle control device disclosed herein comprises: a drive source (2) mounted on a vehicle (1); a differential device (3) for distributing the drive force generated by the drive source (1) to a right drive wheel and a left drive wheel; a speed sensor (7) for detecting the rotational speed of the drive source (2); and a pair of wheel speed sensors (8, 9) for detecting the rotational speeds of the right drive wheel and the left drive wheel. Furthermore, the device comprises a control device (10) that sets an index value having a value obtained by multiplying the rotational speed of the drive source (2) by a predetermined coefficient when at least one of the pair of wheel speed sensors (8, 9) fails, and controls the torque output from the drive source (2) based on the index value.

Description

Technical Field

[0001] The present invention relates to a vehicle control device that performs control to suppress seizure of a differential device. Background Art

[0002] Conventionally, in vehicles where a differential device is disposed between the left and right wheels, techniques have been proposed to prevent seizure caused by an increase in the rotational speed difference. For example, when the rotational speed difference (rotational speed difference) between the left and right wheel axles exceeds a predetermined value, techniques are known to reduce the speed difference by reducing the current supplied to the motor to zero or causing the motor to rotate in the reverse direction. This control can prevent seizure of the differential device (see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 5379541

[0006] Technical problem to be solved by the invention

[0007] Generally speaking, the average of the left and right wheel rotational speeds distributed by the differential is consistent with the rotational speed input to the differential (input speed). Therefore, by measuring at least two of the left and right wheel rotational speeds, as well as the input speed, the differential speed difference can be determined. On the other hand, if the wheel speed sensors measuring the left and right wheel rotational speeds malfunction, determining the exact rotational speed difference may be difficult, making it impossible to prevent seizure. Summary of the Invention

[0008] One of the objectives of the present invention, invented in response to the aforementioned technical problems, is to provide a vehicle control device that can suppress the seizure of a differential device in the event of a wheel speed sensor failure. In addition to this objective, another object of the present invention is to achieve the effects and benefits derived from the various structures described in the "Detailed Description of the Preferred Embodiments" below, which are unattainable with conventional technology.

[0009] Technical means for solving technical problems

[0010] A disclosed vehicle control device includes: a drive source mounted on a vehicle; a differential device that distributes drive force generated by the drive source to right and left drive wheels; a speed sensor that detects the rotational speed of the drive source; and a pair of wheel speed sensors that detect the rotational speeds of the right and left drive wheels. Furthermore, the device includes a control device that, if at least one of the pair of wheel speed sensors fails, sets an index value obtained by multiplying the rotational speed of the drive source by a predetermined coefficient, and controls the torque output from the drive source based on the index value.

[0011] Effects of the Invention

[0012] According to the technique of the present invention, it is possible to suppress seizure of the differential device when a wheel speed sensor fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 FIG. 1 is a schematic diagram of a vehicle to which the vehicle control device according to the embodiment is applied.

[0014] Figure 2 Yes Figure 1 A block diagram of the structure of the control unit (ECU).

[0015] Figure 3 Is used to illustrate Figure 1 A block diagram showing the processing contents of a control device.

[0016] Figure 4A is saved in Figure 1 The present invention is an example of a map of a control device, and is a map that defines the relationship between the rotational speed difference (index value) in the differential device for the front wheels and the torque limit value of the motor for the front wheels.

[0017] Figure 4B is saved in Figure 1 The present invention is an example of a map of a control device, and is a map that defines the relationship between the rotational speed difference (index value) in the differential device for the rear wheels and the torque limit value of the motor for the rear wheels.

[0018] Figure 5 It means by Figure 1 Flowchart of the control process implemented by the control device. DETAILED DESCRIPTION

[0019] [1.Structure]

[0020] Reference Figures 1 to 5A vehicle 1 to which a vehicle control device as an embodiment is applied will be described. The vehicle 1 is equipped with a motor 2 and a differential device 3. The motor 2 is a driving source of the vehicle 1 that generates driving force for the vehicle 1 using the power stored in the battery 6. The motor 2 is, for example, a three-phase AC synchronous motor and is connected to the battery 6 via an inverter 5. Figure 1 The illustrated vehicle 1 is equipped with a motor 2 for the front wheels (front motor) and a motor 2 for the rear wheels (rear motor), but either motor may be omitted, or a single motor 2 may be used to drive all four wheels.

[0021] The differential device 3 is a device that distributes the driving force generated by the motor 2 to the left and right drive wheels, and is arranged between the left and right wheel axles. A transmission 4 is arranged in the transmission path of the driving force connecting the motor 2 and the differential device 3. The transmission 4 is a device that changes the speed (decelerates or speeds up) of the driving force output from the motor 2, and is built with, for example, multiple gear trains, planetary gear mechanisms, etc. The transmission ratio (i.e., input rotational speed ÷ output rotational speed) as the ratio of the input rotational speed to the output rotational speed of the transmission 4 can be a fixed value or a variable value. The information on the transmission ratio of the transmission 4 is grasped by the control device 10 (ECU) described later.

[0022] Battery 6 is a secondary battery capable of supplying high-voltage direct current of several hundred volts, such as a lithium-ion battery or a nickel-metal hydride battery. Inverter 5 is a power conversion device for converting direct current from battery 6 to alternating current from motor 2, and is located on the power line connecting battery 6 and motor 2. Inverter 5 has a built-in inverter circuit that includes switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). The output (torque) of motor 2 is controlled by controlling the operating state of inverter 5 (on / off time, drive frequency).

[0023] The operating state of the inverter 5 is controlled by the control device 10. The control device 10 is an electronic control device (computer) that controls the torque output from the motor 2 by managing the on / off state of the switching element built into the inverter 5. Figure 2As shown, the control device 10 includes a processor (central processing unit), memory (main memory), storage, and an interface device. These components are interconnected via an internal bus so as to be able to communicate with each other. Furthermore, the control device 10 is connected to the motor speed sensor 7, the right wheel speed sensor 8, and the left vehicle speed sensor 9. Furthermore, the control device 10 is also connected to a vehicle speed sensor and an accelerator position sensor (not shown).

[0024] The motor speed sensor 7 is a speed sensor that detects the motor rotation speed (the rotation speed output from the motor 2). In addition, the right wheel speed sensor 8 is a wheel speed sensor that detects the rotation speed of the drive wheel on the right side of the differential device 3 (the right wheel speed), and the left wheel speed sensor 9 is a wheel speed sensor that detects the rotation speed of the drive wheel on the left side of the differential device 3 (the left wheel speed). Information on various rotation speeds detected by these sensors 7 to 9 is input to the control device 10. In addition, the vehicle speed sensor is a sensor that detects the driving speed (vehicle speed) of the vehicle 1, and the throttle opening sensor is a sensor that detects the amount of accelerator pedal depression (throttle opening). In addition, although Figure 1 The middle sensors 7 to 9 are provided on the front side and the rear side, respectively, but either one may be omitted.

[0025] The magnitude of the torque output from the motor 2 is set according to the vehicle speed and the accelerator opening. On the other hand, depending on the driving state of the vehicle 1, the torque of the motor 2 may be too large. For example, when the difference in the number of rotations of the left and right drive wheels is large, there is a concern that seizure may occur inside the differential device 3. Therefore, the control device 10 sets the torque limit value of the motor 2 and controls the inverter 5 in such a way that the torque actually output from the motor 2 does not exceed the torque limit value. Figure 1 In the illustrated vehicle 1 , the outputs of the front wheel motor 2 and the rear wheel motor 2 are controlled based on torque limit values ​​that are individually set.

[0026] Figure 3 This is a block diagram for explaining the processing content of setting the torque limit value. The torque limit value is set using different methods when the wheel speed sensors 8 and 9 are faulty and when they are not faulty. For example, when a pair of left and right wheel speed sensors 8 and 9 provided in the same differential device 3 are not faulty, the torque limit value is set based on the difference in rotational speed of the left and right drive wheels. On the other hand, when at least one of the pair of left and right wheel speed sensors 8 and 9 provided in the same differential device 3 is faulty, the torque limit value is set based on the motor rotational speed. The former setting method is different from the Figure 3 The processing contents shown in the lower middle section correspond to the latter setting method. Figure 3The processing contents shown in the upper middle section correspond to the processing contents shown in the upper middle section. The presence or absence of a failure in the wheel speed sensors 8 and 9 may be determined based on the signals transmitted from the wheel speed sensors 8 and 9, or the determination result of a failure determination device (not shown) may be used.

[0027] Here, a setting method when at least one of the pair of wheel speed sensors 8 and 9 fails will be described in detail. Figure 3 The divider 11 shown in the figure calculates the value of the motor rotational speed divided by the transmission ratio of the transmission 4 (the value multiplied by the inverse of the transmission ratio of the transmission 4). The value calculated here is equivalent to the rotational speed output from the transmission 4, in other words, the rotational speed input to the differential device 3. The value calculated by the divider 11 is input to the multiplier 13 after the sign is removed by the absolute value operator 12. The multiplier 13 calculates the index value obtained by multiplying the input value by a specified coefficient. The value of the coefficient is set to a value close to 2 (for example, in the range of 1.9 to 2.1), for example. The value of the coefficient is preferably set to a value greater than 2 (for example, in the range of 2.0 to 2.1), and more preferably set to 2. The value calculated by the multiplier 13 is input to the multiplier 14.

[0028] Multiplier 14 calculates the product of the value calculated by multiplier 13 and the output of fault determiner 15. Fault determiner 15 outputs 1 if at least one of the pair of wheel speed sensors 8 and 9 is faulty, and outputs 0 if neither of the pair of wheel speed sensors 8 and 9 is faulty. Therefore, if neither of the pair of wheel speed sensors 8 and 9 is faulty, the output of multiplier 14 is 0, regardless of the magnitude of the output of multiplier 13. Only if at least one of the pair of wheel speed sensors 8 and 9 is faulty does multiplier 14 output the output of multiplier 13 directly. Thus, if at least one of the pair of wheel speed sensors 8 and 9 is faulty, multiplier 14 functions by setting an index value having a value obtained by multiplying the motor rotational speed by a predetermined coefficient. The value calculated by multiplier 14 is transmitted to adder 20.

[0029] Next, a setting method when both of the pair of wheel speed sensors 8 and 9 are not faulty will be described in detail. Figure 3 Subtractor 17, shown in FIG, calculates the value obtained by subtracting the right wheel speed from the left wheel speed (the sum of the inverses of the left and right wheel speeds). This calculated value corresponds to the left and right rotational speed difference in differential device 3. The value calculated by subtractor 17 is sign-removed by absolute value calculator 18 and then input to multiplier 19. Multiplier 19 outputs the product of the output of absolute value calculator 18 and the output of subtractor 16. Reducer 16 outputs a value obtained by inverting the output of fault determiner 15.

[0030] For example, subtractor 16 outputs 1 when fault determiner 15 outputs 0, and outputs 0 when fault determiner 15 outputs 1. Therefore, if at least one of the pair of wheel speed sensors 8 and 9 is faulty, the output of multiplier 19 is 0, regardless of the magnitude of the output of absolute value calculator 18. Only when both wheel speed sensors 8 and 9 are not faulty does the output of absolute value calculator 18 directly output from multiplier 19. Thus, when the pair of wheel speed sensors 8 and 9 are not faulty, multiplier 19 functions to calculate the difference in rotational speed between the left and right drive wheels. The value calculated by multiplier 19 is transmitted to adder 20.

[0031] The adder 20 calculates the sum of the output of the multiplier 14 and the output of the multiplier 19. The output of the multiplier 14 is 0 when the pair of wheel speed sensors 8 and 9 are not faulty, and the output of the multiplier 19 is 0 when the pair of wheel speed sensors 8 and 9 are faulty. Therefore, the adder 20 functions by directly receiving the value of the output of the multiplier 14 or 19 that is not 0 and transmitting this information to the downstream side. The value output from the adder 20 is input to the limit value setter 21. The limit value setter 21 outputs a limit value corresponding to the value (index value or rotational speed difference) transmitted from the adder 20. The limit value setter 21 pre-stores at least a mapping or formula that specifies the correspondence between the index value set by the multiplier 14 and the torque limit value.

[0032] Figure 4A This is a graph illustrating the relationship between the torque limit value and the index value in the front wheel motor 2. The solid line in the graph represents the torque limit value, and the dotted line represents the torque that can be generated by the differential device 3 for the front wheel. The dotted line curve shows that the torque on the vertical axis and the index value on the horizontal axis are almost inversely proportional. In addition, Figure 4B This is a graph illustrating the relationship between the torque limit value and the index value in the rear wheel motor 2. The solid line in the graph represents the torque limit value, and the dotted line represents the torque that can be generated in the rear wheel differential device 3.

[0033] The rear-wheel motor 2 and differential device 3 are provided separately from the front-wheel motor 2 and differential device 3 and do not necessarily have the same characteristics as the front-wheel motor 2 and differential device 2. Therefore, the torque limit value of the rear-wheel motor 2 can be set separately from the torque limit value of the front-wheel motor 2. Figure 4B The shapes of the solid and dashed curves in the Figure 4A The shapes of the solid and dashed curves in are consistent. In addition, Figure 4B The maximum value of the torque limit value T2 in Figure 4A The maximum value T1 of the torque limit value in is different. Similarly, Figure 4B The maximum value of the index value R2 in Figure 4AThe maximum value R1 of the indicator value in is different.

[0034] exist Figure 4A 、 Figure 4B In any of the figures, the curve of the torque limit value represented by the solid line is set at least below (to the left) compared to the curve of the dotted line. Therefore, when the rotational speed difference is input to the limit value setter 21, by setting the torque limit value corresponding to the rotational speed difference, the situation of excessive torque being output from the motor 2 is prevented, and the occurrence of seizure at the differential device 3 is suppressed. In addition, when the index value is input to the limit value setter 21, the index value has a value equivalent to a rotational speed that is almost twice the rotational speed of the motor 2. On the other hand, it is known that the maximum rotational speed difference that can be generated in the differential device 3 is twice the input rotational speed. That is, the index value mentioned here has a value equivalent to the maximum rotational speed difference that can be generated in the differential device 3. Therefore, by using the index value instead of the rotational speed difference to set the torque limit value, the situation of excessive torque being output from the motor 2 is prevented, and the occurrence of seizure at the differential device 3 is reliably suppressed.

[0035] [2. Flowchart]

[0036] Figure 5 1 is a flowchart showing the flow of control performed by the control device 10 .

[0037] In step A1, information on the motor rotation speed detected by the motor speed sensor 7 and information on the left and right wheel speeds detected by the pair of left and right wheel speed sensors 8 and 9 are input to the control device 10. In addition, when the gear ratio of the transmission 4 is variable, information related to the value is also input to the control device 10. Next, in step A2, it is determined whether at least one of the pair of wheel speed sensors 8 and 9 is faulty. Figure 1 As shown, when a pair of left and right wheel speed sensors 8 and 9 are provided on the front wheel side and the rear wheel side, respectively, the front wheel side and the rear wheel side are distinguished and the presence or absence of a failure is determined independently of each other.

[0038] If it is determined in step A2 that at least one of the wheel speed sensors 8 and 9 is faulty, the process proceeds to step A3, where an index value is set based on the motor rotational speed. The index value is calculated, for example, by multiplying the absolute value of the value obtained by dividing the motor rotational speed by the gear ratio of the transmission 4 by a predetermined coefficient. Next, in step A4, the index value is used as Figure 4A 、 Figure 4B The argument of the map shown in FIG. 1 is used to obtain a torque limit value corresponding to the index value. Subsequently, in step A5, the operating state of inverter 5 is controlled so that the torque of motor 2 does not exceed the torque limit value. In this way, even if wheel speed sensors 8 and 9 fail, the torque of motor 2 is appropriately limited, thereby suppressing the occurrence of seizure in differential device 3.

[0039] If it is determined in step A2 that the wheel speed sensors 8 and 9 are not faulty, the process proceeds to step A6 to calculate the actual rotational speed difference. The rotational speed difference is calculated as the absolute value of the value obtained by subtracting the right wheel speed from the left wheel speed. Next, in step A7, the rotational speed difference is used as the Figure 4A 、 Figure 4B The argument of the map shown in FIG. 1 is used to obtain a torque limit value corresponding to the rotational speed difference. Subsequently, in step A5, the operating state of inverter 5 is controlled so that the torque of motor 2 does not exceed the torque limit value. In this way, assuming that wheel speed sensors 8 and 9 are not faulty, the rotational speed difference value can be calculated with high accuracy. Consequently, the torque of motor 2 is appropriately limited, and the occurrence of seizure in differential device 3 is suppressed.

[0040] [3. Function and effect]

[0041] (1) The vehicle control device described above is provided with: a motor 2 mounted on a vehicle 1; a differential device 3 that distributes the driving force generated by the motor 2 to the left and right drive wheels; a motor speed sensor 7 that detects the rotational speed of the motor 2; and a pair of wheel speed sensors 8 and 9 that detect the rotational speeds of the left and right drive wheels. Furthermore, the vehicle control device described above is provided with a control device 10 that, if at least one of the pair of wheel speed sensors 8 and 9 fails, sets an index value obtained by multiplying the rotational speed of the motor 2 by a predetermined coefficient, and controls the torque output from the motor 2 based on the index value. This configuration allows the torque of the motor 2 to be limited without using information obtained by the wheel speed sensors 8 and 9, thereby preventing seizure of the differential device 3 in the event of a failure of the wheel speed sensors 8 and 9.

[0042] (2) In the vehicle control device described above, the index value set when at least one of the pair of wheel speed sensors 8 and 9 fails is set, for example, to a value at least twice the rotational speed of the input differential device 3. This allows the index value to be set to at least a value corresponding to (or greater than) the maximum rotational speed difference that can be generated in the differential device 3. Consequently, the occurrence of seizure in the differential device 3 can be reliably suppressed.

[0043] (3) Figure 3 As shown, by setting the specified coefficient to 2, the index value is set to a value twice the value obtained by dividing the motor rotational speed by the transmission ratio. This setting allows the index value to correspond to the maximum rotational speed difference that can be generated in the differential device 3, and can most effectively and reliably suppress the occurrence of seizures in the differential device 3. Furthermore, considering the existence of control errors, calculation errors, etc., the technical significance of setting the specified coefficient value slightly deviating from 2 can also be recognized.

[0044] (4) In the above-mentioned vehicle control device, if Figure 4A 、 Figure 4B As shown, a map defining the relationship between the index value and the torque limit value is used. This map controls the torque output from the motor 2 so that it does not exceed the torque limit value corresponding to the index value, making it easy to prevent excessive torque from being input into the differential device 3. Furthermore, by mapping the relationship between the index value and the torque limit value, the torque limit value can be quickly and easily acquired, reducing the computational burden. This can thus prevent the occurrence of seizures caused by, for example, control delays in the motor 2.

[0045] (5) In the above-mentioned vehicle control device, when the pair of wheel speed sensors 8 and 9 are not faulty, the rotational speed difference between the left and right drive wheels is calculated. In addition, the torque limit value is obtained by substituting the rotational speed difference into the map instead of the index value. With such a control structure, as Figure 4A 、 Figure 4B As shown, only a single map is required for each motor 2, and no new control map needs to be added. Therefore, control resources can be saved, and the occurrence of seizure can be effectively suppressed.

[0046] [4. Modifications]

[0047] The above embodiments are merely illustrative and are not intended to exclude various modifications or technical applications not explicitly described in the present embodiments. The various structures of the present embodiment can be modified and implemented in various ways without departing from the main purpose. Furthermore, they can be selected or combined as needed.

[0048] For example, although the motor 2 is used as the driving source of the vehicle 1 in the above-mentioned embodiment, the above-mentioned vehicle control device can also be applied to a hybrid vehicle that uses the motor 2 and an engine (an internal combustion engine such as a gasoline engine or a diesel engine). In addition, the above-mentioned vehicle control device can also be applied to a vehicle that uses only the engine as the driving source of the vehicle 1. Alternatively, the above-mentioned vehicle control device can also be applied to a vehicle that uses an electric generator (a device that has both the functions of an electric motor and a generator) instead of the motor 2 as the driving source. By setting at least an index value having a value obtained by multiplying the rotational speed of the driving source by a prescribed coefficient, and controlling the torque output from the driving source based on the index value, the same effect as the above-mentioned embodiment can be achieved.

[0049] This application is based on Japanese application (Japanese Patent Application No. 2020-095235) filed on June 1, 2020, the contents of which are incorporated herein by reference.

[0050] Industrial Application Possibilities

[0051] According to the vehicle control device of the present invention, it is possible to suppress seizure of the differential device when a wheel speed sensor fails.

[0052] Explanation of symbols

[0053] 1 vehicle

[0054] 2 motors (drive sources)

[0055] 3 Differential

[0056] 4 Transmission

[0057] 5 Inverter

[0058] 6 Batteries

[0059] 7 Motor speed sensor (speed sensor)

[0060] 8 Right wheel speed sensor (wheel speed sensor)

[0061] 9 Left wheel speed sensor (wheel speed sensor)

[0062] 10 Control unit (electronic control unit)

[0063] 11 divider

[0064] 12 Absolute value operator

[0065] 13 Multiplier

[0066] 14 Multiplier

[0067] 15 Fault Determinator

[0068] 16 Subtractor

[0069] 17 Subtractor

[0070] 18 Absolute value operator

[0071] 19 Multiplier

[0072] 20 Adder

[0073] 21 Limit value setter

Claims

1. A vehicle control device, characterized in that: have: a driving source, the driving source being mounted on the vehicle; a differential device that distributes the driving force generated by the driving source to a right driving wheel and a left driving wheel; a speed sensor that detects a rotational speed of the drive source; a pair of wheel speed sensors that detect rotational speeds of the right drive wheel and the left drive wheel; as well as a control device that, if at least one of the pair of wheel speed sensors fails, sets an index value having a value obtained by multiplying a value obtained by dividing the rotational speed of the drive source by a transmission ratio from the drive source to the differential device by a predetermined coefficient, calculates a rotational speed difference between the right drive wheel and the left drive wheel, and controls the torque output from the drive source based on the index value or the rotational speed difference, if the pair of wheel speed sensors are not failed. The predetermined coefficient is set within the range of 1.9 to 2.

1. The control device includes a map defining a relationship between the index value, the rotational speed difference, and a torque limit value, and controls the torque output from the drive source so as not to exceed the torque limit value having a magnitude corresponding to the index value or the rotational speed difference. The control device acquires the torque limit value using the same map when at least one of the pair of wheel speed sensors fails and when the pair of wheel speed sensors does not fail.

2. The vehicle control device according to claim 1, wherein: The predetermined coefficient has a value of 2 or greater, so that the index value is set to a value equal to or greater than twice a value obtained by dividing the rotational speed of the drive source by the transmission ratio from the drive source to the differential device.

3. The vehicle control device according to claim 1, wherein: The predetermined coefficient is 2, so that the index value is set to a value twice the value obtained by dividing the rotation speed of the drive source by the transmission ratio from the drive source to the differential device.

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