Vehicle control method and vehicle control device

Abstract

To provide a vehicle control method and vehicle control device that stabilize the behavior of a vehicle by suppressing the deviation of a temperature of a tire from the optimal temperature.SOLUTION: A vehicle control device 100 uses a processor 10 to control the distribution of forces generated in front wheels 21 and rear wheels 22 of a vehicle 1. The processor 10 acquires the temperature of the front wheels 21, acquires the temperature of the rear wheels 22, determines whether or not the temperature of the front wheels 21 and the temperature of the rear wheels 22 are the optimal temperature according to the characteristics of the tire, and when at least one of the temperature of the front wheels 21 and the temperature of the rear wheels 22 is not the optimal temperature, reduces the force applied to the wheel with the higher temperature in the front wheels 21 and the rear wheels 22 and increases the force applied to the other wheel.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle control method and a vehicle control device. [Background technology]

[0002] Since the characteristics of the forces generated in the tires of a vehicle change depending on the tire temperature, the vehicle motion control device described in Patent Document 1 controls the running of the vehicle based on the tire temperature of the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-71678 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the vehicle motion control device described in Patent Document 1 does not perform control to suppress deviation of tire temperature from an optimum temperature according to the tire characteristics, so there is a possibility that the vehicle behavior will be unstable if the tire temperature is not at an optimum temperature.

[0005] An object of the present invention is to provide a vehicle control method and a vehicle control device that stabilize the behavior of the vehicle by suppressing deviation of the tire temperature from the optimum temperature. [Means for solving the problem]

[0006] The present invention solves the above problem by reducing the force allocated to the front or rear wheel whichever has the higher temperature and increasing the force allocated to the other wheel when at least one of the front and rear wheel temperatures is not at an appropriate temperature. Effect of the Invention

[0007] According to the present invention, it is possible to suppress deviation of the tire temperature from the optimum temperature, thereby stabilizing the behavior of the vehicle. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a configuration of a vehicle control device according to an embodiment of the present invention; [Diagram 2] 2 is a graph showing the low temperature range, optimum temperature range, and high temperature range of the front and rear wheels of a vehicle, where FIG. 2(a) shows the low temperature range, optimum temperature range, and high temperature range of the front wheels, and FIG. 2(b) shows the low temperature range, optimum temperature range, and high temperature range of the rear wheels. [Diagram 3] 1 is a graph showing the relationship between tire temperature and tire cornering power. [Figure 4] 4 is a flowchart showing the steps of a tire temperature estimation method executed by the tire temperature estimation device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1, the vehicle 1 has a vehicle control device 100 for controlling the distribution of forces (tire forces) generated on the front wheels 21 and rear wheels 22 of the vehicle 1. The forces controlled by the vehicle control device 100 include either or both of longitudinal forces (braking force and driving force) and lateral forces generated on the tires. The vehicle 1 also has a steering angle sensor 31, an acceleration sensor 32, a vehicle speed sensor 33, a driving force sensor 34, a front wheel temperature sensor 35, and a rear wheel temperature sensor 36. The vehicle 1 also has a driving control device 40 for controlling the driving of the vehicle 1.

[0010] The steering angle sensor 31 detects the steering angle of the tires 2 of the vehicle 1 . The acceleration sensor 32 detects longitudinal acceleration (longitudinal G) and lateral acceleration (lateral G) acting on the vehicle 1. The longitudinal direction is the front-rear direction of the vehicle 1, and the lateral direction is the width direction of the vehicle 1. The vehicle speed sensor 33 detects the speed of the vehicle 1 . The driving force sensor 34 detects the magnitude of the driving force input from a driving source such as an engine or an electric motor.

[0011] The front wheel temperature sensor 35 is attached to each of the right front tire 21a and the left front tire 21b, which are a pair of left and right tires that make up the front wheels 21, and detects the temperatures of the right front tire 21a and the left front tire 21b. The rear wheel temperature sensor 36 is attached to each of the right rear tire 22a and the left rear tire 22b, which are a pair of left and right tires that make up the rear wheel 22, and detects the temperatures of the right rear tire 22a and the left rear tire 22b.

[0012] The driving control device 40 controls the driving of the vehicle 1 based on the force distribution of each tire set by the vehicle control device 100. For example, the driving control device 40 controls the operation of the drive mechanism for adjusting the acceleration / deceleration and vehicle speed and the brake operation based on the force distribution of each tire. Note that the drive mechanism is an internal combustion engine in an engine vehicle, a driving motor in an electric vehicle, and an internal combustion engine and a driving motor in a hybrid vehicle.

[0013] The vehicle control device 100 has a processor 10. The processor 10 includes a ROM (Read Only Memory) in which a program is stored, a CPU (Central Processing Unit) that executes the program stored in the ROM, and a RAM (Random Access Memory) that functions as an accessible storage device. The processor 10 has a tire force calculation unit 11, a front wheel temperature acquisition unit 12, a rear wheel temperature acquisition unit 13, a tire condition determination unit 14, and a tire force distribution unit 15. The processor 10 executes the functions of the tire force calculation unit 11, the front wheel temperature acquisition unit 12, the rear wheel temperature acquisition unit 13, the tire condition determination unit 14, and the tire force distribution unit 15 by using the CPU to execute the program stored in the ROM.

[0014] Each component of the processor 10 will be described in detail below. The tire force calculation unit 11 obtains the steering angle of the vehicle 1 from the steering angle sensor 31. The tire force calculation unit 11 also obtains the longitudinal acceleration (longitudinal G) and lateral acceleration (lateral G) applied to the vehicle 1 from the acceleration sensor 32. The tire force calculation unit 11 also obtains the vehicle speed of the vehicle 1 from the vehicle speed sensor 33. The tire force calculation unit 11 also obtains the magnitude of the driving force from the driving force sensor 34. The tire force calculation unit 11 calculates forces (longitudinal force and lateral force) generated in each of the right front tire 21a, the left front tire 21b, the right rear tire 22a, and the left rear tire 22b based on the steering angle of the vehicle 1, the longitudinal acceleration (longitudinal G) and lateral acceleration (lateral G) applied to the vehicle 1, the vehicle speed of the vehicle 1, and the magnitude of the driving force of the vehicle 1.

[0015] The front wheel temperature acquisition unit 12 acquires a front wheel temperature Tf, which is the temperature of the front wheels 21, based on the detection result of the front wheel temperature sensor 35. The front wheel temperature Tf may be the temperature of either the right front tire 21a or the left front tire 21b, or may be the average temperature of the right front tire 21a and the left front tire 21b. The front wheel temperature acquisition unit 12 may also acquire the front wheel temperature Tf by calculating estimated temperatures of the right front tire 21a and the left front tire 21b based on the amounts of heat generated and heat dissipated by the right front tire 21a and the left front tire 21b.

[0016] The rear wheel temperature acquisition unit 13 acquires the rear wheel temperature Tr, which is the temperature of the rear wheel 22, based on the detection result of the rear wheel temperature sensor 36. The rear wheel temperature Tr may be the temperature of either the right rear tire 22a or the left rear tire 22b, or may be the average temperature of the right rear tire 22a and the left rear tire 22b. Similarly to the front wheel temperature acquisition unit 12, the rear wheel temperature acquisition unit 13 may acquire the rear wheel temperature Tr by calculating the estimated temperatures of the right rear tire 22a and the left rear tire 22b based on the amounts of heat generated and heat dissipated by the right rear tire 22a and the left rear tire 22b.

[0017] The tire condition determination unit 14 determines whether the front wheels 21 and the rear wheels 22 are in an optimum temperature state, a high temperature state, or a low temperature state. The optimum temperature state is a state in which the front wheel temperature Tf or the rear wheel temperature Tr is an optimum temperature according to the characteristics of the tires. The optimum temperature of the tires is a tire temperature at which each tire can perform best while the vehicle 1 is running. That is, when the front wheels 21 and the rear wheels 22 are in an optimum temperature state, the behavior of the vehicle 1 is most stable. The optimum temperature is a temperature within a predetermined optimum temperature range according to the characteristics of the tires, but is not limited to this, and may be a predetermined temperature set according to the characteristics of the tires. The high temperature state is a state in which the front wheel temperature Tf or the rear wheel temperature Tr is higher than the predetermined optimum temperature range. That is, the high temperature state is a state in which the front wheel temperature Tf or the rear wheel temperature Tr is higher than the optimum temperature. The low temperature state is a state in which the front wheel temperature Tf or the rear wheel temperature Tr is lower than the predetermined optimum temperature range. That is, the low temperature state is a state in which the front wheel temperature Tf or the rear wheel temperature Tr is lower than the optimum temperature.

[0018] Specifically, as shown in Fig. 2(a), the optimum temperature state of the front wheels 21 is a state in which the front wheel temperature Tf is within an optimum temperature range set according to the characteristics of the front wheels 21, that is, a temperature within a first optimum temperature range RS1. The upper limit temperature of the first optimum temperature range RS1 is a first optimum temperature upper limit temperature Tfs1. The lower limit temperature of the first optimum temperature range RS1 is a first optimum temperature lower limit temperature Tfs2. In other words, when the front wheels 21 are in the optimum temperature state, the front wheel temperature Tf is a temperature that is equal to or higher than the first optimum temperature lower limit temperature Tfs2 and equal to or lower than the first optimum temperature upper limit temperature Tfs1. The high temperature state of the front wheels 21 means a state in which the front wheel temperature Tf is higher than the first optimum temperature range RS1. When the front wheels 21 are in a high temperature state, the front wheel temperature Tf is a temperature within the first high temperature range RH1, that is, a temperature higher than the first optimum upper limit temperature Tfs1. The low temperature state of the front wheels 21 means that the front wheel temperature Tf is lower than the first optimum temperature range RS1. When the front wheels 21 are in the low temperature state, the front wheel temperature Tf is within the first low temperature range RL1, that is, lower than the first optimum lower limit temperature Tfs2.

[0019] On the other hand, as shown in Fig. 2(b), the optimum temperature state of the rear wheels 22 is a state in which the rear wheel temperature Tr is within an optimum temperature range set according to the characteristics of the rear wheels 22, i.e., a temperature within the second optimum temperature range RS2. The upper limit temperature of the second optimum temperature range RS2 is the second optimum temperature upper limit temperature Trs1. The lower limit temperature of the second optimum temperature range RS2 is the second optimum temperature lower limit temperature Trs2. In other words, when the rear wheels 22 are in the optimum temperature state, the rear wheel temperature Tr is a temperature equal to or higher than the second optimum temperature lower limit temperature Trs2 and equal to or lower than the second optimum temperature upper limit temperature Trs1. The high temperature state of the rear wheels 22 means that the rear wheel temperature Tr is higher than the second optimum temperature range RS2. When the rear wheels 22 are in the high temperature state, the rear wheel temperature Tr is within the second high temperature range RH2, i.e., higher than the second optimum upper limit temperature Trs1. The low temperature state of the rear wheels 22 means that the rear wheel temperature Tr is lower than the second optimum temperature range RS2. When the rear wheels 22 are in the low temperature state, the rear wheel temperature Tr is within the second low temperature range RL2, that is, lower than the second optimum lower limit temperature Trs2.

[0020] FIG. 3 shows an example of the criteria for setting the first optimum temperature range RS1 and the second optimum temperature range RS2. As shown in FIG. 3, the first optimum temperature range RS1 and the second optimum temperature range RS2 are set based on the cornering power (CP) generated in the front wheel 21 and the rear wheel 22, respectively. That is, the first optimum temperature range RS1 and the second optimum temperature range RS2 are temperature ranges including the optimum temperature Tm at which the cornering power (CP) is the highest. The first optimum temperature range RS1 and the second optimum temperature range RS2 may be set based on other tire characteristics as well as the cornering power (CP). In addition, since the first optimum temperature range RS1 and the second optimum temperature range RS2 are set according to the characteristics of the front wheel 21 and the characteristics of the rear wheel 22, the first optimum temperature range RS1 and the second optimum temperature range RS2 are different temperature ranges as shown in FIG. 2. Specifically, the first optimum temperature center temperature Tfs0, which is the center value of the first optimum temperature range RS1, is higher than the second optimum temperature center temperature Trs0, which is the center value of the second optimum temperature range R2. Generally, the maximum temperature Tfmax of the front wheel temperature Tf is higher than the maximum temperature Trmax of the rear wheel temperature Tr, and the temperature change of the front wheels 21 is larger than that of the rear wheels 22, so the width of the first optimum temperature range RS1 is larger than the width of the second optimum temperature range RS2. Note that the first optimum temperature range RS1 and the second optimum temperature range RS2 may be the same temperature range.

[0021] The tire condition determination unit 14 determines that the front wheels 21 are in a high temperature state when the tire temperature of at least one of the pair of left and right tires (right front tire 21a, left front tire 21b) constituting the front wheels 21 is higher than the first optimum temperature range RS1. The tire condition determination unit 14 also determines that the rear wheels 22 are in a high temperature state when the tire temperature of at least one of the pair of left and right tires (right rear tire 22a, left rear tire 22b) constituting the rear wheels 22 is higher than the second optimum temperature range RS2.

[0022] Furthermore, the tire condition determination unit 14 determines that the front wheels 21 are in a low temperature state when the tire temperature of at least one of the pair of left and right tires (right front tire 21a, left front tire 21b) constituting the front wheels 21 is lower than a first optimum temperature range RS1. Furthermore, the tire condition determination unit 14 determines that the rear wheels 22 are in a low temperature state when the tire temperature of at least one of the pair of left and right tires (right rear tire 22a, left rear tire 22b) constituting the rear wheels 22 is lower than a second optimum temperature range RS2.

[0023] 1 controls the forces to be distributed to the front wheels 21 and the rear wheels 22 based on the calculation results of the tire force calculation unit 11 and the determination results of the tire condition determination unit 14. That is, the tire force distribution unit 15 adjusts the distribution of forces (longitudinal forces and lateral forces) generated in each of the right front tire 21a, the left front tire 21b, the right rear tire 22a, and the left rear tire 22b based on the tire conditions (optimum temperature condition, high temperature condition, low temperature condition) of the front wheels 21 and the rear wheels 22. The tire force distribution unit 15 controls the control gains or control intervention thresholds of each of the right front tire 21a, the left front tire 21b, the right rear tire 22a, and the left rear tire 22b, thereby controlling the forces to be distributed to each tire.

[0024] When at least one of the front wheel temperature Tf and the rear wheel temperature Tr is not optimum (when at least one of the front wheels 21 and the rear wheels 22 is not in an optimum temperature state), the tire force distribution unit 15 reduces the force distributed to the one of the front wheels 21 and the rear wheels 22 which has a higher relative temperature to the optimum temperature, i.e., the optimum temperature relative temperature, and increases the force distributed to the other. Note that when at least one of the front wheel temperature Tf and the rear wheel temperature Tr is not optimum, the tire force distribution unit 15 may reduce the force distributed to the one of the front wheels 21 and the rear wheels 22 which has a higher temperature, and increase the force distributed to the other, regardless of the optimum temperature relative temperature.

[0025] The optimum temperature relative temperature is a relative temperature to a predetermined reference temperature set for the first optimum temperature range RS1 or the second optimum temperature range RS2. For example, the reference temperature for the first optimum temperature range RS1 is the first optimum temperature center temperature Tfs0, and the reference temperature for the second optimum temperature range RS2 is the second optimum temperature center temperature Trs0. The reference temperature may be an optimum temperature Tm at which the cornering power (CP) is highest in each of the first optimum temperature range RS1 and the second optimum temperature range RS2. When the front wheels 21 and / or the rear wheels 22 are in a high temperature state, the reference temperature for the first optimum temperature range RS1 may be the first optimum temperature upper limit temperature Tfs1, and the reference temperature for the second optimum temperature range RS2 may be the second optimum temperature upper limit temperature Trs1. Furthermore, when the front wheels 21 and / or the rear wheels 22 are in a low temperature state, the reference temperature of the first optimum temperature range RS1 may be the first optimum temperature lower limit temperature Tfs2, and the reference temperature of the second optimum temperature range RS2 may be the second optimum temperature lower limit temperature Trs2. That is, when the front wheels 21 and / or the rear wheels 22 are in a high temperature state, the higher the optimum temperature relative temperature, the greater the deviation of the tire temperature from the optimum temperature ranges (first optimum temperature range RS1 and second optimum temperature range RS2). Furthermore, when the front wheels 21 and / or the rear wheels 22 are in a low temperature state, the lower the optimum temperature relative temperature, the greater the deviation of the tire temperature from the optimum temperature ranges (first optimum temperature range RS1 and second optimum temperature range RS2). When the tire temperature is higher than the reference temperature, the optimum relative temperature is a positive value, and when the tire temperature is lower than the reference temperature, the optimum relative temperature is a negative value. The optimum relative temperature also functions as a condition coefficient for determining the condition of the tire.

[0026] More specifically, when the tire force distribution unit 15 determines that one of the front wheels 21 and the rear wheels 22 is in a high temperature state and the other is not in a high temperature state, it reduces the force distributed to the one in the high temperature state and increases the force distributed to the other. When the tire force distribution unit 15 determines that one of the front wheels 21 and the rear wheels 22 is in a low temperature state and the other is not in a low temperature state, it increases the force distributed to the one in the low temperature state and decreases the force distributed to the other. When the tire force distribution unit 15 determines that one of the front wheels 21 and the rear wheels 22 is in a high temperature state and the other is in a low temperature state, it reduces the force distributed to the one in the high temperature state and increases the force distributed to the one in the low temperature state. When both the front wheels 21 and the rear wheels 22 are in a high temperature state, the tire force distribution unit 15 reduces the force distributed to the one of the front wheels 21 and the rear wheels 22 with the higher optimum relative temperature and increases the force distributed to the other. Similarly, when both the front wheel 21 and the rear wheel 22 are in a low temperature state, the tire force distribution unit 15 reduces the force distributed to the wheel 21 or the rear wheel 22 having the higher optimum relative temperature, and increases the force distributed to the other wheel.

[0027] Furthermore, when the tire temperature of at least one of the pair of left and right tires constituting the front wheel 21 or rear wheel 22 that reduces the force is higher than the optimum temperature range (first optimum temperature range RS1 or second optimum temperature range RS2), the tire force distribution unit 15 increases the amount of force reduction of the tire with the higher tire temperature out of the pair of left and right tires, more than the amount of force reduction of the other tire. When the vehicle 1 is turning and only the temperature of the tire on the outer side of the turning out of the pair of left and right tires is higher than the optimum temperature range, the tire force distribution unit 15 controls the distribution of the force generated in each tire so that the control amount (moment force) is larger than when the pair of left and right tires are at the same temperature. In this way, the vehicle control device 100 can reduce the load on the tire with the higher temperature and improve the turning behavior of the vehicle 1.

[0028] Furthermore, when the tire temperature of at least one of the pair of left and right tires constituting the front wheel 21 or rear wheel 22 that increases the force is lower than the optimum temperature range (first optimum temperature range RS1 or second optimum temperature range RS2), the tire force distribution unit 15 increases the amount of force increase of the tire with the lower tire temperature more than the amount of force increase of the other tire. When the vehicle 1 is turning and only the temperature of the tire on the outside of the pair of left and right tires is lower than the optimum temperature range, the tire force distribution unit 15 controls the distribution of the force generated in each tire so that the control amount (moment force) is smaller than when the pair of left and right tires are at the same temperature. This allows the vehicle control device 100 to reduce the load on the tire with the higher temperature.

[0029] Furthermore, when the front wheels 21 and the rear wheels 22 are in an optimum temperature state, the tire force distribution unit 15 does not change the distribution of force between the front wheels 21 and the rear wheels 22, but controls the force generated in each tire so that the front wheels 21 and the rear wheels 22 maintain an optimum temperature state.

[0030] The tire force distribution unit 15 outputs a control command including control information related to the distribution of force to each tire to the driving control device 40. That is, the tire force distribution unit 15 controls the distribution of force generated in each tire (right-side front tire 21a, left-side front tire 21b, right-side rear tire 22a, left-side rear tire 22b) of the front wheels 21 and rear wheels 22 of the vehicle 1 via the driving control device 40. Specifically, the tire force distribution unit 15 controls the force generated in a tire in a high temperature state so as to reduce the amount of work done by the tire and suppress the amount of heat generated. On the other hand, the tire force distribution unit 15 controls the force generated in a tire in a low temperature state so as to generate a large force within a range that does not exceed the grip limit (friction circle) of the tire and increase the amount of heat generated.

[0031] An example of a method for controlling the distribution of forces generated on each tire in each specific control scenario will be described below. First, a method of controlling the distribution of force to each tire when the driving control device 40 executes turning brake assist control will be described. This control is for improving the line tracing ability of the vehicle 1 and preventing the traveling trajectory of the vehicle 1 from expanding outward when the vehicle 1 turns a corner. The driving control device 40 calculates a target vehicle speed based on the steering angle and vehicle speed of the vehicle 1, calculates a target deceleration from the target vehicle speed and the actual vehicle speed, and applies brakes to the four wheels (tires 21a, 21b of the front wheels 21 and tires 22a, 22b of the rear wheels 22) to add braking force. At this time, if at least one of the front wheel temperature Tf of the front wheels 21 and the rear wheel temperature Tr of the rear wheels 22 is not at an appropriate temperature, the tire force distribution unit 15 reduces the braking force distributed to the one of the front wheels 21 and the rear wheels 22 that has a higher temperature and increases the braking force distributed to the other wheel. Specifically, the tire force distribution unit 15 sets the control gain of the wheel having a higher temperature, either the front wheel 21 or the rear wheel 22, lower than the control gain of the other wheel. This prevents the front wheel temperature Tf and the rear wheel temperature Tr from deviating from the optimum temperature, increases the grip limit, and prevents understeer when the vehicle 1 enters a corner.

[0032] Next, a method of controlling the distribution of force to each tire when the driving control device 40 executes the turning inside wheel brake control will be described. This control applies the brakes to the tire on the inside of the turning to add braking force when the vehicle 1 turns a corner, thereby improving the line tracing ability of the vehicle 1 by reducing the change in steering characteristics due to the turning acceleration. At this time, when at least one of the front wheel temperature Tf of the front wheels 21 and the rear wheel temperature Tr of the rear wheels 22 is not at the optimum temperature, the tire force distribution unit 15 controls the control gains of the front wheels 21 and the rear wheels 22 to reduce the braking force distributed to the front wheel 21 or the rear wheel 22, whichever has a higher temperature relative to the optimum temperature, and to increase the braking force distributed to the other wheel. This suppresses the deviation of the front wheel temperature Tf and the rear wheel temperature Tr from the optimum temperature, and also suppresses factors that cause a sudden change in tire temperature, such as slippage or drifting of the tire on the inside of the turning, thereby stabilizing the behavior of the vehicle 1.

[0033] Next, a method of controlling the distribution of force to each tire when the driving control device 40 executes the turning assist control will be described. This control applies braking force by alternately applying the brakes to the left and right tires when the vehicle 1 makes a detour to avoid an obstacle or changes lanes. This improves the initial response of the yaw rate and suppresses roll-in, thereby improving the roll damping of the vehicle 1. At this time, when at least one of the front wheel temperature Tf of the front wheels 21 and the rear wheel temperature Tr of the rear wheels 22 is not at the optimum temperature, the tire force distribution unit 15 controls the control gains of the front wheels 21 and the rear wheels 22 to reduce the braking force distributed to the front wheel 21 or the rear wheel 22, which has a higher temperature relative to the optimum temperature, and to increase the braking force distributed to the other wheel. This suppresses the deviation of the front wheel temperature Tf and the rear wheel temperature Tr from the optimum temperature, and the transient characteristics between understeer and oversteer return to the optimum temperature state, stabilizing the behavior of the vehicle 1.

[0034] Next, a method of controlling the distribution of force to each tire when the driving control device 40 executes yaw rate feedback control will be described. This control is a feedback control that applies braking force to the tires by applying brakes to eliminate the deviation between the target yaw rate and the actual yaw rate, thereby generating a moment force. At this time, when at least one of the front wheel temperature Tf of the front wheels 21 and the rear wheel temperature Tr of the rear wheels 22 is not at an optimum temperature, the tire force distribution unit 15 controls the control intervention threshold of the yaw rate deviation to reduce the braking force distributed to the front wheel 21 or the rear wheel 22, whichever has a higher temperature relative to the optimum temperature, and to increase the braking force distributed to the other wheel. This suppresses the deviation of the front wheel temperature Tf and the rear wheel temperature Tr from the optimum temperature, and stabilizes the behavior of the vehicle 1.

[0035] Next, a method of controlling the distribution of force to each tire when the driving control device 40 executes the front / rear driving force distribution control will be described. This control determines the ratio of driving forces of the front wheels 21 and the rear wheels 22 so that the yaw rate of the vehicle 1 is in an ideal state. At this time, when at least one of the front wheel temperature Tf of the front wheels 21 and the rear wheel temperature Tr of the rear wheels 22 is not at an optimum temperature, the tire force distribution unit 15 controls the control gains of the front wheels 21 and the rear wheels 22 to reduce the driving force distributed to the front wheel 21 or the rear wheel 22, whichever has a higher temperature relative to the optimum temperature, and to increase the driving force distributed to the other wheel. This suppresses the deviation of the front wheel temperature Tf and the rear wheel temperature Tr from the optimum temperature, and stabilizes the behavior of the vehicle 1. That is, the tire force distribution unit 15 increases the driving force for tires in a low temperature state so as to actively increase the amount of work. On the other hand, the tire force distribution unit 15 reduces the driving force for tires in a high temperature state so as to suppress factors that cause a sudden change in tire temperature, such as slipping and drifting.

[0036] Next, a method of controlling the distribution of force to each tire when the driving control device 40 executes the driving torque suppression control will be described. This control is a control that limits the driving force request so as not to exceed the friction circle of each tire, suppresses unnecessary slip due to exceeding the friction circle, and suppresses the lateral force reduction and acceleration reduction of each tire. This allows the driver of the vehicle 1 to drive the vehicle 1 safely even on a road surface with a low friction coefficient (low μ road surface) without particularly paying attention to the accelerator. At this time, when at least one of the front wheel temperature Tf of the front wheels 21 and the rear wheel temperature Tr of the rear wheels 22 is not at the optimum temperature, the tire force distribution unit 15 controls the control gains of the front wheels 21 and the rear wheels 22 to reduce the driving force distributed to the front wheel 21 or the rear wheel 22, which has a higher temperature relative to the optimum temperature, and increases the driving force distributed to the other wheel. This suppresses the deviation of the front wheel temperature Tf and the rear wheel temperature Tr from the optimum temperature, and can suppress factors that cause a sudden change in tire temperature (for example, slip).

[0037] The procedure of the vehicle control method executed by the vehicle control device 100 will be described with reference to FIG. First, in step S1, the front wheel temperature acquisition unit 12 acquires the front wheel temperature Tf. In addition, in step S2, the rear wheel temperature acquisition unit 13 acquires the rear wheel temperature Tr. The process of step S1 may be executed after the process of step S2, or the process of step S1 and the process of step S2 may be executed simultaneously.

[0038] Next, in step S3, the tire condition determination unit 14 determines whether or not both the front wheels 21 and the rear wheels 22 are in an appropriate temperature state. If both the front wheels 21 and the rear wheels 22 are in an appropriate temperature state, the process ends.

[0039] On the other hand, if it is determined in step S3 that "either one or both of the front wheels 21 and the rear wheels 22 are not in an optimum temperature state," then in step S4, the tire condition determination unit 14 determines whether or not the optimum relative temperature of the front wheels 21 (temperature relative to the optimum temperature) is higher than the optimum relative temperature of the rear wheels 22. Note that a case in which the optimum relative temperature of the front wheels 21 is higher than the optimum relative temperature of the rear wheels 22 refers to a case in which the front wheels 21 are in a high temperature state and the rear wheels 22 are not in a high temperature state, or a case in which the rear wheels 22 are in a low temperature state and the front wheels 21 are not in a low temperature state.

[0040] Then, if it is determined in step S4 that "the optimum relative temperature of the front wheels 21 is higher than the optimum relative temperature of the rear wheels 22," in step S5, the tire force distribution unit 15 reduces the force distributed to the front wheels 21 and increases the force distributed to the rear wheels 22.

[0041] On the other hand, if it is determined in step S4 that "the optimum relative temperature of the front wheels 21 is not higher than the optimum relative temperature of the rear wheels 22," then in step S6, the tire condition determination unit 14 determines whether or not the optimum relative temperature of the rear wheels 22 is higher than the optimum relative temperature of the front wheels 21. Note that a case in which the optimum relative temperature of the rear wheels 22 is higher than the optimum relative temperature of the front wheels 21 occurs when the rear wheels 22 are in a high temperature state and the front wheels 21 are not in a high temperature state, or when the front wheels 21 are in a low temperature state and the rear wheels 22 are not in a low temperature state.

[0042] If it is determined in step S6 that "the optimum relative temperature of the rear wheels 22 is not higher than the optimum relative temperature of the front wheels 21", that is, if the optimum relative temperature of the rear wheels 22 and the optimum relative temperature of the front wheels 21 are the same temperature, the process ends.

[0043] On the other hand, if it is determined in step S6 that "the optimum relative temperature of the rear wheels 22 is higher than the optimum relative temperature of the front wheels 21," in step S7, the tire force distribution unit 15 reduces the force distributed to the rear wheels 22 and increases the force distributed to the front wheels 21.

[0044] In the flowchart of FIG. 4, the process of step S4 may be executed after the process of step S6.

[0045] As described above, the vehicle control device 100 according to this embodiment determines whether the temperature of the front wheels 21 (front wheel temperature Tf) and the temperature of the rear wheels 22 (rear wheel temperature Tr) are appropriate temperatures according to the characteristics of the tires, and when at least one of the temperatures of the front wheels 21 and the rear wheels 22 is not appropriate, the vehicle control device 100 reduces the force allocated to the one of the front wheels 21 and the rear wheels 22 that has a higher temperature and increases the force allocated to the other. As a result, the vehicle control device 100 increases the workload of the one of the front wheels 21 and the rear wheels 22 that has a lower temperature, thereby increasing the amount of heat generated, and raising the tire temperature. In addition, the vehicle control device 100 reduces the workload of the one of the front wheels 21 and the rear wheels 22 that has a higher temperature, thereby suppressing the amount of heat generated, and lowering the tire temperature. As a result, the vehicle control device 100 can suppress deviation of the tire temperature from the appropriate temperature and stabilize the behavior of the vehicle 1.

[0046] In addition, the optimum temperature is a temperature within a predetermined optimum temperature range according to the characteristics of the tire. This allows the vehicle control device 100 to appropriately determine whether each tire is at an optimum temperature.

[0047] Furthermore, when the vehicle control device 100 determines that one of the front wheels 21 and the rear wheels 22 is in a high temperature state and the other is not, it reduces the force allocated to the one in a high temperature state and increases the force allocated to the other. In this way, the vehicle control device 100 reduces the workload of the tire in a high temperature state, suppresses the amount of heat generated, and lowers the tire temperature. Therefore, the tire in a high temperature state approaches an optimum temperature state, so tire performance such as cornering power improves and the behavior of the vehicle 1 becomes stable.

[0048] Furthermore, when the vehicle control device 100 determines that one of the front wheels 21 and the rear wheels 22 is in a low temperature state and the other is not, it increases the force allocated to the one in a low temperature state and decreases the force allocated to the other. As a result, the vehicle control device 100 increases the workload of the tires in a low temperature state, increases the amount of heat generated, and raises the tire temperature. Therefore, the tires in a low temperature state approach an optimum temperature state, improving tire performance such as cornering power, and stabilizing the behavior of the vehicle 1.

[0049] Furthermore, when the vehicle control device 100 determines that one of the front wheels 21 and the rear wheels 22 is in a high temperature state and the other is in a low temperature state, it reduces the force allocated to the one in the high temperature state and increases the force allocated to the one in the low temperature state. As a result, the vehicle control device 100 reduces the workload of the tire in the high temperature state to suppress the amount of heat generated, thereby lowering the tire temperature. Furthermore, the vehicle control device 100 increases the workload of the tire in the low temperature state to increase the amount of heat generated, thereby raising the tire temperature. Thus, the tires in the high temperature state and the tires in the low temperature state approach the optimum temperature state, improving tire performance such as cornering power, and stabilizing the behavior of the vehicle 1.

[0050] Furthermore, when the tire temperature of at least one of the pair of left and right tires constituting the front wheels 21 or the rear wheels 22 is higher than the optimum temperature, the vehicle control device 100 determines that the front wheels 21 or the rear wheels 22 are in a high temperature state. This allows the vehicle control device 100 to control the distribution of force generated in each tire so as to bring the tire in a high temperature state of the pair of left and right tires of the front wheels 21 or the rear wheels 22 closer to an optimum temperature state.

[0051] Furthermore, when the tire temperature of at least one of the pair of left and right tires constituting the front wheels 21 or the rear wheels 22 is lower than the optimum temperature, the vehicle control device 100 determines that the front wheels 21 or the rear wheels 22 are in a low temperature state. This allows the vehicle control device 100 to control the distribution of force generated in each tire so that the tire in the low temperature state of the pair of left and right tires of the front wheels 21 or the rear wheels 22 approaches an optimum temperature state.

[0052] Furthermore, when the tire temperature of at least one of the pair of left and right tires constituting the front wheels 21 or rear wheels 22 that are to be subjected to force reduction is higher than the optimum temperature, the vehicle control device 100 makes the amount of force reduction of the tire with the higher tire temperature of the pair of left and right tires larger than the amount of force reduction of the other tire. This allows the vehicle control device 100 to bring the tire in a high temperature state of the pair of left and right tires of the front wheels 21 or rear wheels 22 closer to an optimum temperature state, thereby stabilizing the behavior of the vehicle 1.

[0053] Furthermore, when the tire temperature of at least one of the pair of left and right tires constituting the front wheels 21 or rear wheels 22 that increase the force is lower than the optimum temperature, the vehicle control device 100 increases the force of the tire with the lower tire temperature by a larger amount than the other tire. This allows the vehicle control device 100 to bring the tire with a low temperature, of the pair of left and right tires of the front wheels 21 or rear wheels 22, closer to the optimum temperature, and stabilizes the behavior of the vehicle 1.

[0054] The vehicle control device 100 also determines whether the front wheels 21 are in an optimum temperature state, which is a temperature within a first optimum temperature range RS1 set according to the characteristics of the front wheels 21, and determines whether the rear wheels 22 are in an optimum temperature state, which is a temperature within a second optimum temperature range RS2 set according to the characteristics of the rear wheels 22. If at least one of the front wheels 21 and the rear wheels 22 is not in an optimum temperature state, the vehicle control device 100 compares the relative temperature of the front wheels 21 with respect to a predetermined reference temperature of the first optimum temperature range RS1 with the relative temperature of the rear wheels 23 with respect to a predetermined reference temperature of the second optimum temperature range RS2, and reduces the force allocated to the front wheel 21 or the rear wheel 22 with the higher relative temperature, and increases the force allocated to the other wheel. In this way, the vehicle control device 100 determines whether the front wheels 21 and the rear wheels 22 are each in the optimum temperature range, based on the different optimum temperature ranges for the front wheels 21 and the rear wheels 22. Therefore, the vehicle control device 100 determines the condition of the tires based on the tire characteristics of each of the front wheels 21 and rear wheels 22, and brings each tire closer to an optimum temperature state based on each tire characteristic, thereby stabilizing the behavior of the vehicle 1. [Explanation of symbols]

[0055] 100...Vehicle control device 1. Vehicle 10…Processor 12...Front wheel temperature acquisition section 13...Rear wheel temperature acquisition section 14…Tire condition determination unit 15…Tire force distribution section 21…Front wheel 22…Rear wheel RS1…First optimum temperature range RS2: Second optimum temperature range Tf…Front wheel temperature Tr…Rear wheel temperature

Claims

1. A vehicle control method for controlling distribution of forces including either or both of longitudinal forces and lateral forces generated on front and rear wheels of a vehicle using a processor, comprising: The processor, Obtaining the temperature of the front wheels; Obtaining the temperature of the rear wheel; determining whether the temperature of the front wheels and the temperature of the rear wheels are appropriate temperatures according to tire characteristics, A vehicle control method, comprising: when at least one of the temperature of the front wheels and the temperature of the rear wheels is not at the optimum temperature, reducing the force distributed to the one of the front wheels and the rear wheels which has a higher temperature, and increasing the force distributed to the other of the front wheels and the rear wheels.

2. The vehicle control method according to claim 1 , wherein the optimum temperature is within a predetermined optimum temperature range according to characteristics of the tire.

3. The processor, determining whether the front wheels and the rear wheels are in a high temperature state, that is, a temperature higher than the appropriate temperature; When it is determined that one of the front wheels and the rear wheels is in a high temperature state and the other is not in a high temperature state, The vehicle control method according to claim 1 , further comprising: decreasing the force allocated to the side having a higher temperature and increasing the force allocated to the other side.

4. The processor, determining whether the front wheels and the rear wheels are in a low temperature state, that is, a temperature lower than the optimum temperature; When it is determined that one of the front wheels and the rear wheels is in a low temperature state and the other is not in a low temperature state, The vehicle control method according to claim 1 , further comprising increasing the force allocated to the side having a lower temperature and decreasing the force allocated to the other side.

5. The processor, determining whether the front wheels and the rear wheels are in a high temperature state, that is, a temperature higher than the appropriate temperature; determining whether the front wheels and the rear wheels are in a low temperature state, that is, a temperature lower than the optimum temperature; When it is determined that one of the front wheels and the rear wheels is in a high temperature state and the other is in a low temperature state, The method of claim 1 , further comprising: decreasing the force allocated to a higher temperature condition and increasing the force allocated to a lower temperature condition.

6. The processor, 5. The vehicle control method according to claim 2, further comprising the step of determining that the front wheels or the rear wheels are in a high temperature state when the tire temperature of at least one of the pair of left and right tires constituting the front wheels or the rear wheels is higher than the optimum temperature.

7. The processor, 5. The vehicle control method according to claim 3, further comprising the step of determining that the front wheels or the rear wheels are in a low temperature state when the tire temperature of at least one of the pair of left and right tires constituting the front wheels or the rear wheels is lower than the optimum temperature.

8. The processor, 2. The vehicle control method according to claim 1, wherein, when a tire temperature of at least one of the pair of left and right tires constituting the front wheel or the rear wheel that reduces the force is higher than the optimum temperature, an amount of reduction in the force of the tire with the higher tire temperature of the pair of left and right tires is made larger than the amount of reduction in the other tire.

9. The processor, 2. The vehicle control method according to claim 1, wherein, when the tire temperature of at least one of the pair of left and right tires constituting the front wheel or the rear wheel that increases the force is lower than the optimum temperature, an increase in the force of the tire with the lower tire temperature of the pair of left and right tires is made larger than the increase in the other tire.

10. The processor, determining whether the front wheels are in an optimum temperature state, that is, a temperature within a first optimum temperature range that is set in accordance with a characteristic of the front wheels; determining whether the rear wheels are in an optimum temperature state, that is, a temperature within a second optimum temperature range that is set in accordance with a characteristic of the rear wheels; When at least one of the front wheels and the rear wheels is not at an optimum temperature, a relative temperature of the temperature of the front wheels with respect to a predetermined reference temperature of the first optimum temperature range is compared with a relative temperature of the temperature of the rear wheels with respect to a predetermined reference temperature of the second optimum temperature range; 2. The vehicle control method according to claim 1, wherein the force distributed to one of the front wheels and the rear wheels, which has a higher relative temperature, is reduced, and the force distributed to the other of the front wheels and the rear wheels is increased.

11. A vehicle control device that controls a distribution of forces including either or both of a longitudinal force and a lateral force generated on a front wheel and a rear wheel of a vehicle, a front wheel temperature acquisition unit for acquiring the temperature of the front wheel; a rear wheel temperature acquisition unit for acquiring the temperature of the rear wheel; a tire condition determination unit that determines whether or not the temperature of the front wheels and the temperature of the rear wheels are appropriate temperatures according to the characteristics of the tires; and a tire force distribution unit that, when at least one of a temperature of the front wheels and a temperature of the rear wheels is not at the optimum temperature, reduces the force distributed to one of the front wheels and the rear wheels, which has a higher temperature, and increases the force distributed to the other of the front wheels and the rear wheels.

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