Braking control device

Abstract

To enhance fault-tolerance, while suppressing costs from increasing.SOLUTION: A braking control device 60 comprises a first processing circuit 65 into which outputs signals of a wheel speed sensor 90fr for a right front wheel and of a wheel speed sensor 90rr for a right rear wheel of a plurality of wheel speed sensors are at least inputted to calculate wheel speed of the two right wheels on the basis of the inputted output signals, and a second processing circuit 75 into which output signals of a wheel speed sensor 90fl for a left front wheel and of a wheel speed sensor 90rl for a left rear wheel which are different from the above-described sensors of the plurality of wheel speed sensors are at least inputted to calculate a wheel speed of the two left wheels, on the basis of the inputted output signals.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a brake control device provided in a vehicle. [Background technology]

[0002] Patent Document 1 discloses a sensor device having two electronic control devices. Each of the two electronic control devices includes one calculation unit and two evaluation and control units. That is, the sensor device includes two calculation units and four evaluation and control units. The evaluation and control units are simply called "evaluation units." An output signal of a wheel speed sensor provided on a corresponding wheel is input to each of the multiple evaluation units. Among the multiple evaluation units, the first evaluation unit and the second evaluation unit output a signal corresponding to the output signal of the wheel speed sensor input to the first calculation unit of the two calculation units. Among the multiple evaluation units, the third evaluation unit and the fourth evaluation unit output a signal corresponding to the output signal of the wheel speed sensor input to the second calculation unit of the two calculation units. In addition, the first evaluation unit and the fourth evaluation unit are capable of communicating with each other, and the second evaluation unit and the third evaluation unit are capable of communicating with each other.

[0003] As a result, even if an abnormality occurs in one of the calculation units or the evaluation unit, one of the two calculation units can obtain the wheel speeds of at least three wheels, which increases the fault tolerance of the sensor device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2023-528348 Summary of the Invention [Problem to be solved by the invention]

[0005] The above sensor device can obtain the wheel speeds of two wheels when one of the electronic control devices stops functioning due to a power failure, etc. However, since the above sensor device is configured with two calculation units and four evaluation units, the cost is high relative to the number of wheel speeds that can be obtained. [Means for solving the problem]

[0006] A braking control device for solving the above problem is applied to a vehicle having two front wheels and two rear wheels, with a wheel speed sensor provided on each of the multiple wheels, and is a device that has a control unit that calculates a target braking force, which is a target for the braking force to be generated on the wheels, for each of the multiple wheels based on the wheel speeds obtained from the output signals of the multiple wheel speed sensors, and generates braking forces on the multiple wheels that correspond to the target braking forces. The braking control device includes a first calculation unit which is a part of the plurality of wheel speed sensors, and which receives at least output signals from the wheel speed sensor provided on one of the two front wheels and the wheel speed sensor provided on one of the two rear wheels, and calculates the wheel speed of the one front wheel and the wheel speed of the one rear wheel based on the input output signals; and a second calculation unit which is a sensor other than the part of the plurality of wheel speed sensors, and which receives at least output signals from the wheel speed sensor provided on the other of the two front wheels and the wheel speed sensor provided on the other of the two rear wheels, and calculates the wheel speed of the other front wheel and the wheel speed of the other rear wheel based on the input output signals. Effect of the Invention

[0007] The braking control device has an effect of improving fault tolerance while suppressing an increase in cost. [Brief description of the drawings]

[0008] [Figure 1]FIG. 1 is a schematic diagram showing the configuration of a vehicle equipped with a brake control device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram of the brake control device shown in FIG. [Diagram 3] FIG. 3 is a flowchart showing a series of processes for calculating the wheel speeds of a plurality of wheels and the body speed of the vehicle in the brake control device shown in FIG. [Figure 4] FIG. 4 is a flowchart showing a series of processes when the front / rear braking force distribution control is executed in the braking control device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of the brake control device will be described with reference to Figs. <Overall vehicle configuration> FIG 1 illustrates a vehicle 10 equipped with a brake control device 60. The vehicle 10 has two front wheels FR, FL and two rear wheels RR, RL as wheels. The vehicle 10 has a front wheel axle 11 and a rear wheel axle 21. The front wheel axle 11 is an axle to which the two front wheels FR, FL are connected. The rear wheel axle 21 is an axle to which the two rear wheels RR, RL are connected.

[0010] The front axle 11 is provided with a front wheel differential 13. The front wheel differential 13 is a differential that distributes the driving force output from the power source of the vehicle 10 to a left front wheel FL and a right front wheel FR. The rear axle 21 is provided with a rear wheel differential 23. The rear wheel differential 23 is a differential that distributes the driving force output from the power source of the vehicle 10 to a left rear wheel RL and a right rear wheel RR.

[0011] <Vehicle drive system> The drive system of the vehicle 10 includes a front-wheel drive device 31 and a rear-wheel drive device 35. For example, the front-wheel drive device 31 and the rear-wheel drive device 35 each have a drive motor as a power source of the vehicle 10. The front-wheel drive device 31 is connected to the front-wheel differential device 13 via a front-wheel transmission shaft 32. Thereby, the driving force output from the front-wheel drive device 31 is transmitted to the two front wheels FR, FL via the front-wheel transmission shaft 32 and the front-wheel differential device 13. The rear-wheel drive device 35 is connected to the rear-wheel differential device 23 via a rear-wheel transmission shaft 36. Thereby, the driving force output from the rear-wheel drive device 35 is transmitted to the two rear wheels RR, RL via the rear-wheel transmission shaft 36 and the rear-wheel differential device 23.

[0012] The drive system of the vehicle 10 includes a drive control device 40. The drive control device 40 controls the operations of the front-wheel drive device 31 and the rear-wheel drive device 35. The drive control device 40 has a processing circuit 41. An example of the processing circuit 41 is a computing unit. In this case, the processing circuit 41 has a CPU and a memory. Then, when the CPU reads the control program in the memory, the processing circuit 41 controls the operations of the front-wheel drive device 31 and the rear-wheel drive device 35.

[0013] The front-wheel drive device 31 has a front-wheel motor angle sensor 31a that outputs a signal corresponding to the rotational speed of the output shaft of the drive motor. The output signal of the front-wheel motor angle sensor 31a is input to the drive control device 40. Therefore, the processing circuit 41 calculates the rotational speed of the output shaft of the drive motor and the rotational speed of the front-wheel transmission shaft 32 based on the output signal of the front-wheel motor angle sensor 31a. Then, the processing circuit 41 controls the front-wheel drive device 31 based on such calculation results.

[0014] The rear-wheel drive device 35 has a rear-wheel motor angle sensor 35a that outputs a signal corresponding to the rotational speed of the output shaft of the drive motor. The output signal of the rear-wheel motor angle sensor 35a is input to the drive control device 40. Therefore, the processing circuit 41 calculates the rotational speed of the output shaft of the drive motor and the rotational speed of the rear-wheel transmission shaft 36 based on the output signal of the rear-wheel motor angle sensor 35a. Then, the processing circuit 41 controls the rear-wheel drive device 35 based on such calculation results.

[0015] <Vehicle braking system> The braking system of the vehicle 10 includes a braking device that generates braking forces on the multiple wheels FR, FL, RR, and RL, and a braking control device 60 that controls the operation of the braking device. In this example, the braking system includes multiple electric braking devices 50 provided for each of the wheels FR, FL, RR, and RL as braking devices. Each of the multiple electric braking devices 50 includes a braking motor 51. Each of the multiple electric braking devices 50 generates a braking force on each wheel according to the rotation angle of the braking motor 51.

[0016] The brake control device 60 receives output signals from wheel speed sensors 90fr, 90fl, 90rr, and 90rl provided on the wheels FR, FL, RR, and RL. The brake control device 60 calculates the wheel speeds VWfr, VWfl, VWrr, and VWrl of the wheels FR, FL, RR, and RL based on the output signals from the wheel speed sensors 90fr, 90fl, 90rr, and 90rl. When braking the vehicle 10, the brake control device 60 calculates a target braking force, which is a target of the braking force to be generated in the wheels, for each of the wheels FR, FL, RR, and RL based on the wheel speeds VWfr, VWfl, VWrr, and VWrl of the wheels FR, FL, RR, and RL. Then, the brake control device 60 operates the electric brake devices 50 so that braking forces corresponding to the target braking forces are generated in the wheels FR, FL, RR, and RL.

[0017] <In-vehicle communication system> The vehicle 10 is equipped with a plurality of control devices including a drive control device 40 and a braking control device 60. These control devices are each configured to be able to communicate with each other via an in-vehicle network 100. An example of the in-vehicle network 100 is a CAN bus. CAN is an abbreviation for "Controller Area Network."

[0018] The drive control device 40 transmits various information to the in-vehicle network 100 at predetermined communication intervals. For example, the drive control device 40 transmits at least one of the rotation speed of the output shaft of the drive motor of the front wheel drive device 31 and the rotation speed of the front wheel transmission shaft 32 to the in-vehicle network 100 as information related to the rotation speed of the front wheel transmission shaft 32. Also, for example, the drive control device 40 transmits at least one of the rotation speed of the output shaft of the drive motor of the rear wheel drive device 35 and the rotation speed of the rear wheel transmission shaft 36 to the in-vehicle network 100 as information related to the rotation speed of the rear wheel transmission shaft 36.

[0019] An example of a braking device other than the drive control device 40 and the braking control device 60 is a steering control device that controls the steering angles of the two front wheels FR, FL. The steering control device transmits information related to the steering angle Str of the steering wheel of the vehicle 10 to the in-vehicle network 100 at every predetermined communication period.

[0020] <Brake control device> 2, the braking control device 60 includes a first controller 61 and a second controller 71. The first controller 61 and the second controller 71 correspond to the electronic control devices described in the Background of the Invention section.

[0021] The first controller 61 has a connector 62 to which signal lines of some of the four wheel speed sensors 90fr, 90fl, 90rr, and 90rl are connected, a first ASIC 64, and a first processing circuit 65. In this example, the connector 62 of the first controller 61 is connected to a signal line of the wheel speed sensor 90fr provided on the right front wheel FR and a signal line of the wheel speed sensor 90rr provided on the right rear wheel RR. That is, the first controller 61 receives output signals from some of the multiple wheel speed sensors 90fr, 90fl, 90rr, and 90rl, that is, a wheel speed sensor provided on one of the two front wheels FR and FL, and a wheel speed sensor provided on one of the two rear wheels RR and RL.

[0022] The first ASIC 64 corresponds to the evaluation unit described in the Background section. The first ASIC 64 is composed of an interface 63fr for the wheel speed sensor 90fr and an interface 63rr for the wheel speed sensor 90rr. An output signal of the wheel speed sensor 90fr is input to the first processing circuit 65 via the interface 63fr. An output signal of the wheel speed sensor 90rr is input to the first processing circuit 65 via the interface 63rr.

[0023] The second controller 71 has a connector 72 to which signal lines of some of the four wheel speed sensors 90fr, 90fl, 90rr, and 90rl are connected, a second ASIC 74, and a second processing circuit 75. In this example, the connector 72 of the second controller 71 is connected to a signal line of the wheel speed sensor 90fl provided on the left front wheel FL and a signal line of the wheel speed sensor 90rl provided on the left rear wheel RL. That is, the second controller 71 receives output signals from the wheel speed sensor provided on the other of the two front wheels FR and FL and the wheel speed sensor provided on the other of the two rear wheels RR and RL, which are sensors other than the some of the sensors among the multiple wheel speed sensors 90fr, 90fl, 90rr, and 90rl.

[0024] The second ASIC 74 corresponds to the evaluation unit described in the Background section. The second ASIC 74 is composed of an interface 73fl for the wheel speed sensor 90fl and an interface 73rl for the wheel speed sensor 90rl. An output signal of the wheel speed sensor 90fl is input to the second processing circuit 75 via the interface 73fl. An output signal of the wheel speed sensor 90rl is input to the second processing circuit 75 via the interface 73rl.

[0025] An example of the multiple processing circuits 65, 75 is a calculation unit. In this case, the first processing circuit 65 has a CPU 66, a first memory 67, and a second memory 68. The second processing circuit 75 has a CPU 76, a first memory 77, and a second memory 78. The first memories 67, 77 store various control programs executed by the CPUs 66, 76. The second memories 68, 78 store the calculation results of the CPUs 66, 76.

[0026] The two processing circuits 65, 75 are each configured to be capable of transmitting and receiving various information via the internal line 80. Therefore, the first processing circuit 65 can acquire the calculation results of the CPU 76 in the second processing circuit 75. The second processing circuit 75 can acquire the calculation results of the CPU 66 in the first processing circuit 65. Furthermore, when a failure occurs in the second processing circuit 75, the first processing circuit 65 can recognize that a failure has occurred in the second processing circuit 75. When a failure occurs in the first processing circuit 65, the second processing circuit 75 can recognize that a failure has occurred in the first processing circuit 65.

[0027] 2, either of the two processing circuits 65, 75 can control the operation of the multiple electric braking devices 50. However, when at least the first processing circuit 65 of the two processing circuits 65, 75 is normal, the first processing circuit 65 controls the operation of the multiple electric braking devices 50. On the other hand, when a malfunction occurs in the first processing circuit 65 while the second processing circuit 75 is normal, the second processing circuit 75 controls the operation of the multiple electric braking devices 50.

[0028] <Functional configuration of the first processing circuit and the second processing circuit> The two processing circuits 65, 75 function as a plurality of functional units by the CPUs 66, 76 executing the control programs in the first memories 67, 77. The plurality of functional units include a calculation unit M11, an estimation unit M13, and a control unit M15.

[0029] <Arithmetic section> The calculation unit M11 calculates the wheel speed of the wheel corresponding to the wheel speed sensor based on the output signal of the wheel speed sensor.

[0030] As described above, the output signals of the wheel speed sensor 90fr for the right front wheel FR and the wheel speed sensor 90rr for the right rear wheel RR are input to the first processing circuit 65. On the other hand, the output signals of the wheel speed sensor 90fl for the left front wheel FL and the wheel speed sensor 90rl for the left rear wheel RL are input to the second processing circuit 75.

[0031] Therefore, the calculation unit M11 of the first processing circuit 65 calculates the wheel speed VWfr of the right front wheel FR based on the output signal of the wheel speed sensor 90fr. The calculation unit M11 of the first processing circuit 65 calculates the wheel speed VWrr of the right rear wheel RR based on the output signal of the wheel speed sensor 90rr. On the other hand, the calculation unit M11 of the second processing circuit 75 calculates the wheel speed VWfl of the left front wheel FL based on the output signal of the wheel speed sensor 90fl. The calculation unit M11 of the second processing circuit 75 calculates the wheel speed VWrl of the left rear wheel RL based on the output signal of the wheel speed sensor 90rl. That is, in this embodiment, the calculation unit M11 of the first processing circuit 65 corresponds to the "first calculation unit". The calculation unit M11 of the second processing circuit 75 corresponds to the "second calculation unit".

[0032] When both of the two processing circuits 65, 75 are normal, the calculation unit M11 of the first processing circuit 65 transmits the wheel speeds VWfr and VWrr calculated by itself to the second processing circuit 75 via the internal line 80. The calculation unit M11 of the second processing circuit 75 transmits the wheel speeds VWfl and VWrl calculated by itself to the first processing circuit 65 via the internal line 80.

[0033] Both the calculation unit M11 of the first processing circuit 65 and the calculation unit M11 of the second processing circuit 75 can calculate the vehicle speed VS of the vehicle 10 based on the wheel speeds VWfl, VWfr, VWrl, and VWrr of the multiple wheels FR, FL, RR, and RL. The calculation unit M11 of the first processing circuit 65 and the calculation unit M11 of the second processing circuit 75 may calculate the vehicle speed VS based on the output signals of the wheel speed sensors excluding the output signals of the wheel speed sensors input to the processing circuit in which a malfunction has occurred. In this embodiment, when at least the first processing circuit 65 of the two processing circuits 65 and 75 is normal, the calculation unit M11 of the first processing circuit 65 calculates the vehicle speed VS. On the other hand, when a malfunction has occurred in the first processing circuit 65 under a condition in which the second processing circuit 75 is normal, the calculation unit M11 of the second processing circuit 75 calculates the vehicle speed VS.

[0034] <Estimation part> The estimation unit M13 of the first processing circuit 65 functions when a failure occurs in the second processing circuit 75 under a condition where the first processing circuit 65 is normal. The estimation unit M13 of the first processing circuit 65 estimates the wheel speed of the left front wheel FL based on information on the rotation speed of the front wheel transmission shaft 32 and an output signal of the wheel speed VWfr for the right front wheel FR input to the first processing circuit 65. The wheel speed of the left front wheel FL is one of the wheel speeds to be calculated by the calculation unit M11 of the second processing circuit 75. For example, the estimation unit M13 calculates a wheel speed estimation value VWfle, which is an estimate of the wheel speed of the left front wheel FL, based on the rotation speed Nd1 of the front wheel transmission shaft 32 and the wheel speed VWfr of the right front wheel FR.

[0035] The estimation unit M13 of the first processing circuit 65 estimates the wheel speed of the left rear wheel RL based on information on the rotation speed of the rear wheel transmission shaft 36 and an output signal of the wheel speed VWrr for the right rear wheel RR input to the first processing circuit 65. The wheel speed of the left rear wheel RL is one of the wheel speeds to be calculated by the calculation unit M11 of the second processing circuit 75. For example, the estimation unit M13 calculates a wheel speed estimation value VWrle, which is an estimate of the wheel speed of the left rear wheel RL, based on the rotation speed Nd2 of the rear wheel transmission shaft 36 and the wheel speed VWrr of the right rear wheel RR.

[0036] On the other hand, the estimation unit M13 of the second processing circuit 75 functions when a failure occurs in the first processing circuit 65 under a condition where the second processing circuit 75 is normal. The estimation unit M13 of the second processing circuit 75 estimates the wheel speed of the right front wheel FR based on information on the rotation speed of the front wheel transmission shaft 32 and an output signal of the wheel speed VWfl for the left front wheel FL input to the second processing circuit 75. The wheel speed of the right front wheel FR is one of the wheel speeds to be calculated by the calculation unit M11 of the first processing circuit 65. For example, the estimation unit M13 calculates a wheel speed estimation value VWfre, which is an estimate of the wheel speed of the right front wheel FR, based on the rotation speed Nd1 of the front wheel transmission shaft 32 and the wheel speed VWfl of the left front wheel FL.

[0037] The estimation unit M13 of the second processing circuit 75 estimates the wheel speed of the right rear wheel RR based on information about the rotation speed of the rear wheel transmission shaft 36 and an output signal of the wheel speed VWrl for the left rear wheel RL input to the second processing circuit 75. The wheel speed of the right rear wheel RR is one of the wheel speeds to be calculated by the calculation unit M11 of the first processing circuit 65. For example, the estimation unit M13 calculates a wheel speed estimation value VWrre, which is an estimate of the wheel speed of the right rear wheel RR, based on the rotation speed Nd2 of the rear wheel transmission shaft 36 and the wheel speed VWrl of the left rear wheel RL.

[0038] As described above, the right front wheel FR and the left front wheel FL are connected to the front wheel transmission shaft 32 via the front wheel differential 13. Therefore, the rotation speed of the right front wheel FR is the average value of the rotation speed of the front wheel transmission shaft 32 and the rotation speed of the left front wheel FL. The rotation speed of the left front wheel FL is the average value of the rotation speed of the front wheel transmission shaft 32 and the rotation speed of the right front wheel FR. Therefore, if the rotation speed (wheel speed) of one of the right front wheel FR and the left front wheel FL and the rotation speed Nd1 of the front wheel transmission shaft 32 are known, the rotation speed (wheel speed) of the other of the right front wheel FR and the left front wheel FL can be estimated.

[0039] The right rear wheel RR and the left rear wheel RL are connected to the rear wheel transmission shaft 36 via the rear wheel differential 23. Therefore, the rotation speed of the right rear wheel RR is the average value of the rotation speed of the rear wheel transmission shaft 36 and the rotation speed of the left rear wheel RL. The rotation speed of the left rear wheel RL is the average value of the rotation speed of the rear wheel transmission shaft 36 and the rotation speed of the right rear wheel RR. Therefore, if the rotation speed (wheel speed) of one of the right rear wheels RR and the left rear wheel RL and the rotation speed Nd2 of the rear wheel transmission shaft 36 are known, the rotation speed (wheel speed) of the other of the right rear wheels RR and the left rear wheels RL can be estimated.

[0040] <Control Unit> The control unit M15 calculates target braking forces for the multiple wheels FR, FL, RR, and RL. Then, the control unit M15 controls the operation of the multiple electric braking devices 50 based on the multiple target braking forces.

[0041] The control unit M15 executes various types of braking control. The various types of braking control include, for example, front / rear braking force distribution control, antilock brake control, and traction control. The front / rear braking force distribution control is a control that adjusts the distribution between the front wheel braking force, which is the braking force generated on the front wheels FR, FL, and the rear wheel braking force, which is the braking force generated on the rear wheels RR, RL. Specifically, the front / rear braking force distribution control is a control that increases the front wheel braking force while maintaining the rear wheel braking force after the vehicle braking force has increased to a certain level. The vehicle braking force is the sum of the front wheel braking force and the rear wheel braking force.

[0042] A description will be given of the front / rear braking force distribution control when both of the two processing circuits 65, 75 are normal. In this case, the control unit M15 of the first processing circuit 65 functions, while the control unit M15 of the second processing circuit 75 stops.

[0043] The control unit M15 of the first processing circuit 65 calculates a target braking force for the front wheels FR, FL based on a required braking force, which is a required value of the braking force for the vehicle 10, the current vehicle braking force, and the wheel speeds VWfr, VWfl of the front wheels FR, FL. The control unit M15 calculates a target braking force for the rear wheels RR, RL based on the required braking force, the current vehicle braking force, and the wheel speeds VWrr, VWrl of the rear wheels RR, RL.

[0044] The control unit M15 of the first processing circuit 65 then operates the electric braking device 50 for the right front wheel FR and the electric braking device 50 for the left front wheel FL based on the target braking forces for the front wheels FR, FL. The control unit M15 then operates the electric braking device 50 for the right rear wheel RR and the electric braking device 50 for the left rear wheel RL based on the target braking forces for the rear wheels RR, RL.

[0045] A description will be given of the front / rear braking force distribution control in the case where the first processing circuit 65 is normal while a malfunction occurs in the second processing circuit 75. In this case, the control section M15 of the first processing circuit 65 functions.

[0046] The control unit M15 of the first processing circuit 65 calculates the target braking forces for the front wheels FR, FL based on the required braking force, the current vehicle braking force, and the wheel speed VWfr of the right front wheel FR. The control unit M15 calculates the target braking forces for the rear wheels RR, RL based on the required braking force, the current vehicle braking force, and the wheel speed VWrr of the right rear wheel RR. Then, the control unit M15 of the first processing circuit 65 operates the electric braking device 50 for the right front wheel FR and the electric braking device 50 for the left front wheel FL based on the target braking forces for the front wheels FR, FL. The control unit M15 operates the electric braking device 50 for the right rear wheel RR and the electric braking device 50 for the left rear wheel RL based on the target braking forces for the rear wheels RR, RL.

[0047] A description will be given of the front / rear braking force distribution control in the case where the second processing circuit 75 is normal while a malfunction occurs in the first processing circuit 65. In this case, the control section M15 of the second processing circuit 75 functions.

[0048] The control unit M15 of the second processing circuit 75 calculates the target braking force for the front wheels FR, FL based on the required braking force, the current vehicle braking force, and the wheel speed VWfl of the left front wheel FL. The control unit M15 calculates the target braking force for the rear wheels RR, RL based on the required braking force, the current vehicle braking force, and the wheel speed VWrl of the left rear wheel RL. Then, the control unit M15 of the second processing circuit 75 operates the electric braking device 50 for the right front wheel FR and the electric braking device 50 for the left front wheel FL based on the target braking force for the front wheels FR, FL. The control unit M15 operates the electric braking device 50 for the right rear wheel RR and the electric braking device 50 for the left rear wheel RL based on the target braking force for the rear wheels RR, RL.

[0049] <Wheel speed calculation processing> 3, a wheel speed calculation process, which is a series of processes performed by the brake control device 60 to calculate the wheel speeds of the wheels FR, FL, RR, RL and the body speed of the vehicle 10, will be described. The first processing circuit 65 and the second processing circuit 75 repeatedly execute the wheel speed calculation process for each predetermined control cycle.

[0050] In step S11, the processing circuits 65, 75 acquire other information via the in-vehicle network 100. For example, the processing circuits 65, 75 acquire the rotation speed Nd1 of the front wheel transmission shaft 32, the rotation speed Nd2 of the rear wheel transmission shaft 36, and the steering angle Str of the steering wheel as other information. In addition, for example, the processing circuits 65, 75 acquire the wheel speed VW calculated by the other processing circuit. The other party from the perspective of the first processing circuit 65 is the second processing circuit 75. The other party from the perspective of the second processing circuit 75 is the first processing circuit 65.

[0051] In the next step S13, the processing circuits 65 and 75 calculate the wheel speed VW of the wheels that they are responsible for. The wheels that the first processing circuit 65 is responsible for are the two right wheels FR and RR. Therefore, the first processing circuit 65 calculates the wheel speed VWfr of the right front wheel FR based on the output signal of the wheel speed sensor 90fr. The first processing circuit 65 calculates the wheel speed VWrr of the right rear wheel RR based on the output signal of the wheel speed sensor 90rr. On the other hand, the wheels that the second processing circuit 75 is responsible for are the two left wheels FL and RL. Therefore, the second processing circuit 75 calculates the wheel speed VWfl of the left front wheel FL based on the output signal of the wheel speed sensor 90fl. The second processing circuit 75 calculates the wheel speed VWrl of the left rear wheel RL based on the output signal of the wheel speed sensor 90rl.

[0052] In the next step S15, the processing circuits 65 and 75 judge whether a malfunction has occurred in the processing circuit of the other party. Specifically, the first processing circuit 65 judges whether a malfunction has occurred in the second processing circuit 75. Similarly, the second processing circuit 75 judges whether a malfunction has occurred in the first processing circuit 65. If a malfunction has occurred in the second processing circuit 75, the second processing circuit 75 may not have calculated the wheel speeds VWfl and VWrl of the two left wheels FL and RL. That is, the first processing circuit 65 may not be able to obtain the wheel speeds VWfl and VWrl of the two left wheels FL and RL from the second processing circuit 75. If a malfunction has occurred in the first processing circuit 65, the first processing circuit 65 may not have calculated the wheel speeds VWfr and VWrr of the two right wheels FR and RR. That is, the second processing circuit 75 may not be able to obtain the wheel speeds VWfr and VWrr of the two right wheels FR and RR from the first processing circuit 65.

[0053] Therefore, if the processing circuits 65, 75 determine that a malfunction has occurred in the processing circuit of the other party (S15: YES), the processing proceeds to step S19. On the other hand, if the processing circuits 65, 75 determine that a malfunction has not occurred in the processing circuit of the other party (S15: NO), the processing proceeds to step S17.

[0054] In step S17, the processing circuit 65, 75 judges whether or not it has priority. If the processing circuit 65, 75 judges that it has priority (S17: YES), it shifts the process to step S21. On the other hand, if the processing circuit 65, 75 judges that it does not have priority (S17: NO), it temporarily ends the wheel speed calculation process.

[0055] In this embodiment, when at least the first processing circuit 65 of the two processing circuits 65 and 75 is normal, the first processing circuit 65 has priority. When a failure occurs in the first processing circuit 65 under a condition where the second processing circuit 75 is normal, the second processing circuit 75 has priority.

[0056] In step S19, the processing circuits 65 and 75 estimate the wheel speed VW of the wheel handled by the other party. Specifically, the first processing circuit 65 calculates the wheel speed estimate VWfle of the left front wheel FL based on the rotation speed Nd1 of the front wheel transmission shaft 32 and the wheel speed VWfr of the right front wheel FR. The first processing circuit 65 calculates the wheel speed estimate VWrle of the left rear wheel RL based on the rotation speed Nd2 of the rear wheel transmission shaft 36 and the wheel speed VWrr of the right rear wheel RR. On the other hand, the second processing circuit 75 calculates the wheel speed estimate VWfre of the right front wheel FR based on the rotation speed Nd1 of the front wheel transmission shaft 32 and the wheel speed VWfl of the left front wheel FL. The second processing circuit 75 calculates the wheel speed estimate VWrre of the right rear wheel RR based on the rotation speed Nd2 of the rear wheel transmission shaft 36 and the wheel speed VWrl of the left rear wheel RL. Thereafter, the processing circuits 65, 75 transfer the processing to step S21.

[0057] In step S21, the processing circuits 65, 75 calculate the vehicle body speed VS of the vehicle 10. When both the two processing circuits 65, 75 are normal, the first processing circuit 65 calculates the vehicle body speed VS based on the wheel speeds VWfl, VWfr, VWrl, VWrr of the multiple wheels FR, FL, RR, RL. When a malfunction occurs in the second processing circuit 75 under a condition where the first processing circuit 65 is normal, the first processing circuit 65 calculates the vehicle body speed VS based on the wheel speeds VWfr, VWrr of the right wheels FR, RR and the wheel speed estimated values ​​VWfle, VWrle of the left wheels FL, RL. When a malfunction occurs in the first processing circuit 65 while the second processing circuit 75 is normal, the second processing circuit 75 calculates the vehicle body speed VS based on the wheel speeds VWfl, VWrl of the left wheels FL, RL and the wheel speed estimates VWfre, VWrre of the right wheels FR, RR. After that, the processing circuits 65, 75 temporarily end the wheel speed calculation process.

[0058] In this embodiment, the first processing circuit 65 executes the processes of steps S13 and S21 by functioning as the calculation unit M11 (first calculation unit). The second processing circuit 75 executes the processes of steps S13 and S21 by functioning as the calculation unit M11 (second calculation unit). The first processing circuit 65 executes the process of step S19 by functioning as the estimation unit M13. The second processing circuit 75 executes the process of step S19 by functioning as the estimation unit M13.

[0059] <Braking control processing> With reference to Fig. 4, a braking control process, which is a series of processes when front / rear braking force distribution control, which is an example of braking control, is executed by the braking control device 60, will be described. Of the two processing circuits 65, 75, the processing circuit having the above-mentioned priority executes the braking control process. At this time, if the execution conditions for the front / rear braking force distribution control are satisfied, the processing circuit repeatedly executes the braking control process for each predetermined control cycle.

[0060] In step S31, the processing circuits 65, 75 judge whether or not a malfunction has occurred on the other side. The processing content of step S31 is the same as the processing content of step S15. If the processing circuits 65, 75 judge that a malfunction has occurred on the other side (S31: YES), the processing circuit shifts the processing to step S37. On the other hand, if the processing circuits 65, 75 judge that a malfunction has not occurred on the other side (S31: NO), the processing circuit shifts the processing to step S33.

[0061] In step S33, the processing circuits 65, 75 calculate the average of the wheel speeds VWfr, VWfl of the front wheels FR, FL as the average front wheel speed value VWFAv. The processing circuits 65, 75 calculate the average of the wheel speeds VWrr, VWrl of the rear wheels RR, RL as the average rear wheel speed value VWRAv.

[0062] In the next step S35, the processing circuits 65, 75 set the front wheel speed VWFa to the front wheel speed average value VWFAv, the processing circuits 65, 75 set the rear wheel speed VWRa to the rear wheel speed average value VWRAv, and the processing circuits 65, 75 proceed to step S39.

[0063] In step S37, the processing circuits 65, 75 set the front wheel speed VWFa and the rear wheel speed VWRa. For example, when the first processing circuit 65 has priority, the first processing circuit 65 sets the wheel speed VWfr of the right front wheel FR as the front wheel speed VWFa. Also, the first processing circuit 65 sets the wheel speed VWrr of the right rear wheel RR as the rear wheel speed VWRa. On the other hand, when the second processing circuit 75 has priority, the second processing circuit 75 sets the wheel speed VWfl of the left front wheel FL as the front wheel speed VWFa. Also, the second processing circuit 75 sets the wheel speed VWrl of the left rear wheel RL as the rear wheel speed VWRa. Then, the processing circuits 65, 75 move the process to step S39.

[0064] In step S39, the processing circuits 65, 75 execute the front / rear braking force distribution control based on the front wheel speed VWFa and the rear wheel speed VWRa, and then the processing circuits 65, 75 temporarily end the braking control process.

[0065] In this embodiment, when the first processing circuit 65 has priority, the first processing circuit 65 executes each process of steps S31 to S39 by functioning as the control unit M15. When the second processing circuit 75 has priority, the second processing circuit 75 executes each process of steps S31 to S39 by functioning as the control unit M15.

[0066] <Actions and Effects of the Present Embodiment> (1) The brake control device 60 includes a first processing circuit 65 and a second processing circuit 75. The first processing circuit 65 receives at least the output signals of the wheel speed sensors 90fr, 90fl, 90rr, 90rl of the two right wheels FR, RR, which are part of the multiple wheel speed sensors 90fr, 90fl, 90rr, 90rl. The first processing circuit 65 calculates the wheel speeds VWfr, VWrr of the two right wheels FR, RR based on the input output signals. The second processing circuit 75 receives at least the output signals of the wheel speed sensors 90fl, 90rl of the two left wheels FL, RL, which are part of the multiple wheel speed sensors 90fr, 90fl, 90rr, 90rl. The second processing circuit 75 calculates the wheel speeds VWfl, VWrl of the two left wheels FL, RL based on the input output signals.

[0067] In the braking control device 60, even if a failure occurs in only one of the two processing circuits 65, 75, the other processing circuit can calculate the wheel speed of one of the left and right front wheels FR, FL and the wheel speed of one of the left and right rear wheels RR, RL. Therefore, the braking control device 60 can control the front wheel braking force using the wheel speed VW that has been calculated of the two front wheels FR, FL. Similarly, the braking control device 60 can control the front wheel braking force using the wheel speed VW that has been calculated of the two rear wheels RR, RL. Therefore, the braking control device 60 can increase the fault tolerance while suppressing an increase in cost.

[0068] In the braking control device 60, the signal lines of two of the four wheel speed sensors 90fr, 90fl, 90rr, and 90rl are connected to the first controller 61, and the signal lines of the remaining two wheel speed sensors are connected to the second controller 71. Therefore, even if a malfunction occurs in only one of the two controllers 61 and 71, the other controller can calculate the wheel speed of one of the left and right front wheels FR and FL, and the wheel speed of one of the left and right rear wheels RR and RL. Each of the two controllers 61 and 71 includes one processor and one ASIC. Therefore, since the braking control device 60 is configured to include two processors and two ASICs, it is possible to increase the fault tolerance while suppressing an increase in cost.

[0069] In addition, when the vehicle 10 enters a low friction road surface while traveling, a sudden change occurs in the wheel speeds VWrr, VWrl of the front wheels FR, FL before the wheel speeds VWfr, VWfl of the rear wheels RR, RL. Therefore, if a malfunction occurs in only one of the two processing circuits 65, 75, the braking force can be controlled using the wheel speeds VWfr, VWfl of the rear wheels RR, RL that have not undergone a sudden change and that have been calculated. Therefore, the braking control device 60 can suppress a decrease in control accuracy during a malfunction.

[0070] (2) In the braking control device 60, of the four wheel speed sensors 90fr, 90fl, 90rr, and 90rl, the signal lines of two of the wheel speed sensors are connected to the first controller 61, and the signal lines of the remaining two wheel speed sensors are connected to the second controller 71. This allows the first controller 61 and the second controller 71 to use connectors with the same number of pins. Therefore, in the braking control device 60, it is not necessary to use connectors with different numbers of pins for the first controller 61 and the second controller 71, and this can suppress an increase in costs.

[0071] (3) Consider a comparative example in which the signal lines of the wheel speed sensor 90fr of the right front wheel FR and the wheel speed sensor 90rl of the left rear wheel RL are connected to the first controller 61, and the signal lines of the wheel speed sensor 90fl of the left front wheel FL and the wheel speed sensor 90rr of the right rear wheel RR are connected to the second controller 71. In this comparative example, the first processing circuit 65 calculates the wheel speeds VWfr, VWrl of the right front wheel FR and the left rear wheel RL, while the second processing circuit 75 calculates the wheel speeds VWfl, VWrr of the left front wheel FL and the right rear wheel RR.

[0072] In the above comparative example, if a malfunction occurs in one of the two processing circuits 65, 75, the other processing circuit executes the front / rear braking force distribution control during vehicle braking. When the front / rear braking force distribution control is executed, a difference in wheel speed between the front and rear wheels may occur due to the difference between the front wheel braking force and the rear wheel braking force. Furthermore, when the vehicle 10 turns while the front / rear braking force distribution control is being executed, a difference in wheel speed between the right and left wheels occurs due to the turning.

[0073] Therefore, assuming that the other processing circuit that is not malfunctioning is the first processing circuit 65, the first processing circuit 65 cannot determine whether the wheel speed difference occurring between the right front wheel FR and the left rear wheel RL is occurring as a result of cornering or as a result of the execution of front / rear braking force distribution control.

[0074] In this regard, in the braking control device 60, the signal lines of the wheel speed sensors 90fr, 90rr of the two right wheels FR, RR are connected to the first controller 61. Also, the signal lines of the wheel speed sensors 90fl, 90rl of the two left wheels FL, RL are connected to the second controller 71. Then, the first processing circuit 65 calculates the wheel speeds VWfr, VWrr of the two right wheels FR, RR, while the second processing circuit 75 calculates the wheel speeds VWfl, VWrl of the two left wheels FL, RL.

[0075] In a situation where a malfunction occurs in one of the two processing circuits 65, 75, the other processing circuit that is not malfunctioning executes the front / rear braking force distribution control. For example, assuming that the other processing circuit that is not malfunctioning is the first processing circuit 65, the first processing circuit 65 executes the front / rear braking force distribution control using the wheel speed VWfr of the right front wheel FR and the wheel speed VWrr of the right rear wheel RR. In this case, when a wheel speed difference occurs between the right front wheel FR and the right rear wheel RR, the first processing circuit 65 can recognize that a wheel speed difference occurs with the execution of the front / rear braking force distribution control.

[0076] Also, for example, assuming that the other processing circuit that is not malfunctioning is the second processing circuit 75, the second processing circuit 75 executes front / rear braking force distribution control using the wheel speed VWfl of the left front wheel FL and the wheel speed VWrl of the left rear wheel RL. In this case, when a wheel speed difference occurs between the left front wheel FL and the left rear wheel RL, the second processing circuit 75 can recognize that a wheel speed difference occurs with the execution of the front / rear braking force distribution control.

[0077] Therefore, in the braking control device 60, when a malfunction occurs in one of the two processing circuits 65, 75 and the other processing circuit executes front / rear braking force distribution control, the distribution of the front wheel braking force and the rear wheel braking force can be appropriately controlled even while the vehicle is turning.

[0078] (4) In a situation where a malfunction occurs in one of the two processing circuits 65, 75, the other processing circuit that is not malfunctioning can estimate the wheel speed of the wheel that is to be calculated by the other processing circuit by using the rotation speeds Nd1, Nd2 of the transmission shafts 32, 36. In other words, in the braking control device 60, even in a situation where a malfunction occurs in one of the two processing circuits 65, 75, the wheel speeds of the four wheels FR, FL, RR, and RL can be derived.

[0079] As a result, the braking control device 60 can accurately calculate the vehicle speed VS even in a situation where a failure occurs in one of the two processing circuits 65, 75. Furthermore, the braking control device 60 can suppress a decrease in the accuracy of the braking control that uses the vehicle speed VS.

[0080] (5) The braking control device 60 can obtain the steering angle Str of the steering wheel via the in-vehicle network 100. This allows the braking control device 60 to determine whether the wheel speed VW is changing because the vehicle 10 is turning, or whether the wheel speed VW is changing due to some other factor. Factors other than turning include, for example, changes in road surface conditions (road surface μ, road surface gradient, etc.).

[0081] Furthermore, the braking control device 60 can estimate the degree of turning of the vehicle 10 based on the steering angle Str. Therefore, the braking control device 60 can correct the wheel speed VW according to the degree of turning of the vehicle 10 that can be estimated from the steering angle Str. Then, by calculating the vehicle body speed VS using the wheel speed VW corrected in this way, it is possible to suppress a decrease in the calculation accuracy of the vehicle body speed VS associated with the turning of the vehicle 10.

[0082] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0083] The braking control device 60 may be configured to include a third controller in addition to the first controller 61 and the second controller 71. In this case, the third controller may function as the control unit M15.

[0084] The vehicle to which the braking control device is applied may not be a vehicle that has a rear-wheel drive device 35, so long as it has a front-wheel drive device 31. In this case, the vehicle is provided with a front wheel differential device 13. Therefore, when the wheel speed of one of the two front wheels FR, FL cannot be calculated, the braking control device can estimate the wheel speed of the one front wheel based on the wheel speed of the other front wheel and the rotation speed Nd1 of the front wheel transmission shaft 32.

[0085] The vehicle to which the braking control device is applied may not be a vehicle that has a front-wheel drive device 31, so long as it has a rear-wheel drive device 35. In this case, the vehicle is provided with a rear-wheel differential device 23. Therefore, when the wheel speed of one of the two rear wheels RR, RL cannot be calculated, the braking control device can estimate the wheel speed of the one rear wheel based on the wheel speed of the other rear wheel and the rotation speed Nd2 of the rear wheel transmission shaft 36.

[0086] The two processing circuits 65 and 75 do not have to function as the estimation unit M13. When a malfunction occurs in the second processing circuit 75, the first processing circuit 65 may also use the wheel speed estimates VWfle, VWrle of the two left wheels FL, RL to execute front / rear braking force distribution control.

[0087] The first processing circuit 65 may receive output signals from other wheel speed sensors among the multiple wheel speed sensors 90fr, 90fl, 90rr, and 90rl, as long as at least the output signals from the wheel speed sensors 90fr and 90rr are input.

[0088] The second processing circuit 75 may receive output signals from other wheel speed sensors among the multiple wheel speed sensors 90fr, 90fl, 90rr, and 90rl, as long as output signals from at least the wheel speed sensors 90fl and 90rl are input.

[0089] The first processing circuit 65 may receive output signals from a wheel speed sensor 90fr for the right front wheel FR and a wheel speed sensor 90rl for the left rear wheel RL, while the second processing circuit 75 may receive output signals from a wheel speed sensor 90fl for the left front wheel FL and a wheel speed sensor 90rr for the right rear wheel RR.

[0090] When both of the two processing circuits 65, 75 are normal, the second processing circuit 75 may have priority. The processing circuitry 65, 75 may be comprised of one or more processors operating according to a computer program. The processor includes a CPU and memory, such as RAM and ROM, that stores program code or instructions configured to cause the CPU to perform operations. The memory, i.e., storage medium, includes any available medium that can be accessed by a general purpose or special purpose computer.

[0091] <Other technical ideas> Next, the technical ideas that can be understood from the above embodiment and modified examples will be described. (Additional Note 1) In the event that a malfunction occurs in one of the first calculation unit and the second calculation unit, it is preferable that the other calculation unit that is not malfunctioning calculates a body speed of the vehicle based on the wheel speed of the wheel that it has calculated itself and the wheel speed of the wheel that has been estimated by the estimation unit.

[0092] The term "at least one" used herein means "one or more" of the desired options. As an example, the term "at least one" used herein means "only one option" or "both of two options" if the number of options is two. As another example, the term "at least one" used herein means "only one option" or "any combination of two or more options" if the number of options is three or more. [Explanation of symbols]

[0093] 10…Vehicle 11...Front axle 13...Front wheel differential 21...Rear axle 23...Rear wheel differential 31...Front wheel drive 32…Front wheel transmission shaft 35…Rear wheel drive 36…Rear wheel transmission shaft 60...Brake control device 61,71…Controller 62,72…Connector 64,74…ASIC 65,75...Processing circuit 90fr, 90fl, 90rr, 90rl...Wheel speed sensor M11...Arithmetic section M13…Estimated section M15…Control section FR,RL…Front wheel RR,RL…Rear wheel

Claims

1. The present invention is applied to a vehicle having two front wheels and two rear wheels as wheels, and a wheel speed sensor is provided on each of the plurality of wheels, A brake control device including a control unit that calculates a target braking force, which is a target of a braking force to be generated on each of the wheels, for each of the plurality of wheels based on wheel speeds obtained from output signals of the plurality of wheel speed sensors, and generates braking forces corresponding to the target braking forces on the plurality of wheels, a first calculation unit which receives at least output signals from the wheel speed sensor provided on one of the two front wheels and the wheel speed sensor provided on one of the two rear wheels, the first calculation unit being a part of the plurality of wheel speed sensors, and calculates a wheel speed of the one front wheel and a wheel speed of the one rear wheel based on the input output signals; a second calculation unit to which at least output signals of the wheel speed sensor provided on the other of the two front wheels and the wheel speed sensor provided on the other of the two rear wheels, which are sensors other than the some of the plurality of wheel speed sensors, are input, and which calculates the wheel speed of the other front wheel and the wheel speed of the other rear wheel based on the input output signals. A braking control device comprising:

2. At least an output signal of the wheel speed sensor provided on a right front wheel of the two front wheels and an output signal of the wheel speed sensor provided on a right rear wheel of the two rear wheels are input to the first calculation unit, At least an output signal of the wheel speed sensor provided on a left front wheel of the two front wheels and an output signal of the wheel speed sensor provided on a left rear wheel of the two rear wheels are input to the second calculation unit, When a malfunction occurs in one of the first calculation unit and the second calculation unit, the control unit performs front / rear braking force distribution control to adjust the distribution of the braking force generated on the front wheels and the braking force generated on the rear wheels based on the output signal of the wheel speed sensor input to the other calculation unit that is not malfunctioning.

2. The braking control device according to claim 1.

3. The vehicle includes an axle to which at least one of the two front wheels or the two rear wheels is coupled, and a differential device provided on the axle, The differential device is configured to distribute a driving force output from a power source of the vehicle to the two wheels connected to the axles, and an estimation unit that, when a malfunction occurs in one of the first calculation unit and the second calculation unit, estimates the wheel speed of the wheel that is to be calculated by the one calculation unit based on an output signal of the wheel speed sensor input to the other calculation unit that is not malfunctioning and information about a rotation speed of a transmission shaft that transmits the driving force output from the power source to the differential device. The brake control device according to claim 1 or 2.

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