Vehicle braking control device

Abstract

To enable the braking force of a vehicle to be adjusted according to the request value of the braking force even if any abnormality occurs in a braking control device.SOLUTION: If a braking control device 50 is diagnosed as functioning normally, a command section 70f transmits a braking force command value to driving sections 60a and 60b, and a command section 70r transmits a braking force command value to driving sections 60c and 60d. Then, the driving sections 60a and 60b drive braking mechanisms 30a and 30b according to the command value transmitted by the command section 70f, and the driving sections 60c and 60d drive braking mechanisms 30c and 30d according to the command value transmitted by the command section 70r. On the other hand, if the braking control device 50 is diagnosed as not functioning normally, at least one of the command sections 70f and 70r executes backup control to compensate for the lack of the braking force of a vehicle 10 with respect to a braking request due to the braking control device 50 not functioning normally.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a braking control device for a vehicle. [Background technology]

[0002] Patent Document 1 describes an example of a brake device that individually adjusts the braking force applied to four wheels of a vehicle. This brake device includes four brake actuators corresponding to the four wheels, respectively, and four actuator control devices corresponding to the four brake actuators, respectively. The brake device also includes a system control device that derives a braking force command value. The system control device has two computers. When the braking force command value is sent from the system control device to an actuator control device, the actuator control device drives its corresponding brake actuator based on the received command value.

[0003] When a vehicle equipped with the brake device is traveling, a malfunction may occur in one of the system control device and each actuator control device. In this case, the actuator control device that is not malfunctioning applies braking force to the wheels by driving the brake actuator corresponding to it. This allows the vehicle to be stopped and the safety of the occupants to be ensured even if a malfunction occurs in one of the control devices. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2010-534590 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, in brake devices with a redundant configuration in which the system control device has multiple computers, it is desirable to be able to adjust the vehicle's braking force in accordance with the driver's intentions even if an abnormality occurs in one of the control devices as described above. However, in the brake device described in Patent Document 1, there is a risk that the vehicle's braking force cannot be adjusted in accordance with the driver's intentions if an abnormality occurs in one of the control devices. [Means for solving the problem]

[0006] The means for solving the above problems and their effects will be described below. A vehicle braking control device that solves the above problem is a vehicle braking control device that is applied to a vehicle having a first braking mechanism that applies braking force to a first wheel and a second braking mechanism that applies braking force to a second wheel, and includes a first drive unit that applies braking force to the first wheel by driving the first braking mechanism in accordance with a first command value that is a command value for braking force to be applied to the first wheel, a second drive unit that applies braking force to the second wheel by driving the second braking mechanism in accordance with a second command value that is a command value for braking force to be applied to the second wheel, a first command unit that derives the first command value and the second command value based on a braking request that is a request for braking force for the vehicle, and is capable of transmitting the first command value to the first drive unit and transmitting the second command value to the second drive unit, and a second command unit that derives the first command value and the second command value based on the braking request, and is capable of transmitting the first command value to the first drive unit. and a second command unit capable of transmitting the second command value to the second drive unit; and a diagnosis unit that diagnoses whether the brake control device is functioning normally, wherein when the diagnosis unit diagnoses that the brake control device is functioning normally, the first command unit transmits the first command value to the first drive unit, the first drive unit drives the first brake mechanism in accordance with the first command value transmitted by the first command unit, the second command unit transmits the second command value to the second drive unit, and the second drive unit drives the second brake mechanism in accordance with the second command value transmitted by the second command unit, and when the diagnosis unit diagnoses that the brake control device is not functioning normally, at least one of the first command unit and the second command unit performs backup control to compensate for a shortage of braking force of the vehicle in response to the braking request caused by the brake control device not functioning normally.

[0007] If some kind of abnormality occurs in the braking control device, it may not be possible to generate a braking force corresponding to the required value of braking force on the vehicle. In this regard, with the above configuration, if it is diagnosed that the braking control device is not functioning normally, backup control is implemented. This makes it possible to suppress a shortage of braking force caused by the braking control device not functioning normally. Therefore, with the above configuration, even if some kind of abnormality occurs in the braking control device, it is possible to adjust the braking force of the vehicle according to the required value of braking force. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with a braking control device according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing communication paths between the first command unit, the second command unit, and the first drive unit and the second drive unit. [Figure 3] FIG. 3 is a table showing the relationship between the pattern of the diagnosis result and the mode of transmission of the command value. [Figure 4] FIG. 4 is a flowchart showing the flow of a series of processes executed when classifying patterns of diagnostic results. [Figure 5] FIG. 5 is a flowchart showing the flow of a series of processes that are executed when a braking request is made under circumstances in which some abnormality has occurred in the braking control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a vehicle braking control device will be described with reference to the drawings. <Vehicle> 1 shows a vehicle 10 equipped with a brake control device 50. In addition to the brake control device 50, the vehicle 10 is equipped with four wheels 20 (20a to 20d), four brake mechanisms 30 (30a to 30d), a brake operating member 40, and a stroke sensor 41.

[0010] <Brake mechanism 30> The braking mechanisms 30 apply braking force to the corresponding wheels 20. Of the four braking mechanisms 30, braking mechanism 30a corresponds to the right front wheel 20a, braking mechanism 30b corresponds to the left front wheel 20b, braking mechanism 30c corresponds to the right rear wheel 20c, and braking mechanism 30d corresponds to the left rear wheel 20d.

[0011] As shown in FIG. 1 , the braking mechanism 30 includes a rotating body 31 that rotates integrally with the wheel 20, a friction material 32 that does not rotate integrally with the wheel 20, and an electric motor 33 that drives the friction material 32. The friction material 32 is displaced toward or away from the rotating body 31 by the driving of the electric motor 33. By bringing the friction material 32 closer to the rotating body 31, a braking force is applied to the wheel 20. When the driving of the electric motor 33 increases the force pressing the friction material 32 against the rotating body 31, the braking force applied to the wheel 20 increases. The braking mechanism 30 is, for example, an electromechanical brake (EMB). In this embodiment, the braking mechanism 30 is a disc brake, but in other embodiments, the braking mechanism 30 may be a drum brake.

[0012] <Brake operating member 40> As shown in Fig. 1, the brake operating member 40 is a member that is operated when the driver requests braking of the vehicle 10. The brake operating member 40 is, for example, a brake pedal. The stroke sensor 41 detects the amount of operation of the brake operating member 40 by the driver. The stroke sensor 41 outputs a detection signal indicating the detected amount of operation to the brake control device 50.

[0013] It should be noted that instead of the stroke sensor 41, an operating force sensor may be provided that detects the operating force input to the brake operating member 40 by the driver, and the detection signal of the operating force sensor may be input to the brake control device 50. Of course, the detection signals of both the stroke sensor 41 and the operating force sensor may be input to the brake control device 50.

[0014] <Brake control device 50> 1, the braking control device 50 includes the same number of drive units 60 (60a to 60d) as the braking mechanism 30, and two command units 70 (70f, 70r). In the braking control device 50, the four drive units 60 and the two command units 70 correspond to CPUs. Note that the command unit 70 may be a dedicated hardware circuit.

[0015] The drive units 60 control the corresponding brake mechanisms 30. That is, of the four drive units 60a, the drive unit 60a controls the brake mechanism 30a of the four brake mechanisms 30. Furthermore, the drive unit 60b controls the brake mechanism 30b, the drive unit 60c controls the brake mechanism 30c, and the drive unit 60d controls the brake mechanism 30d. The drive units 60 are disposed near the corresponding brake mechanisms 30. The corresponding drive units 60 and brake mechanisms 30 may be unitized. For example, the drive unit 60a may be unitized with the brake mechanism 30a.

[0016] The drive unit 60 drives the corresponding brake mechanism 30 in accordance with a command value indicating the magnitude of the braking force to be applied to the wheel 20. In this way, the braking force applied to each of the four wheels 20 is adjusted. For example, the drive unit 60a drives the brake mechanism 30a for the right front wheel in accordance with a command value for the braking force to be applied to the right front wheel 20a. In this way, the braking force applied to the right front wheel 20a is adjusted.

[0017] The two command units 70 are implemented in a command control unit 100. The command control unit 100 is, for example, an ECU. As shown in FIG. 1, the command control unit 100 is a unit separate from the four braking mechanisms 30 in which the four drive units 60 are respectively provided. Within the command control unit 100, the two command units 70 are connected to each other so that they can communicate with each other.

[0018] Of the two command units 70, command unit 70f is connected to four drive units 60 via communication lines. Furthermore, command unit 70r is connected to four drive units 60 via communication lines. For example, the communication line connecting command unit 70f and drive units 60 and the communication line connecting command unit 70r and drive units 60 are partially shared. In other embodiments, the two communication lines may be completely independent. In the former case, each drive unit 60 requires one input / output port to communicate with the two command units 70, and in the latter case, each drive unit 60 requires two input / output ports to communicate with the two command units 70.

[0019] When there is a braking request, the command unit 70f derives a requested braking force as a requested value of the braking force of the vehicle 10. For example, when the driver requests the generation of braking force by operating the brake operating member 40, the command unit 70f derives the requested braking force based on the detection signal output from the stroke sensor 41. Furthermore, when deceleration of the vehicle 10 is requested by another control device, the command unit 70f determines that there is a braking request, and derives a braking force corresponding to the requested deceleration as the requested braking force. Next, the command unit 70f derives command values of braking forces to be applied to the four wheels 20 based on the requested braking force. The command unit 70f can transmit the command values of braking forces to be applied to the four wheels 20 to the four drive units 60, respectively.

[0020] The command values of the braking forces to be applied to the four wheels 20 are braking forces obtained by distributing the required braking force to the four wheels 20. The command values for the four wheels 20 may be the same value or different values. It is preferable that the command unit 70f derives the command values for the four wheels 20 after taking into consideration the conditions of the vehicle 10 and the road surface conditions. Note that, during ABS control, for example, the total value of the command values of the braking forces to be applied to the four wheels 20 may be a value different from the required braking force.

[0021] The command unit 70f has a diagnosis unit 80f (80) that diagnoses whether the four drive units 60 are functioning normally. The diagnosis unit 80f diagnoses whether the four drive units 60 are functioning normally by transmitting and receiving signals to and from the four drive units 60.

[0022] An example of a method for diagnosing whether or not the drive unit 60 is functioning normally will be described below. Here, the case where the diagnosing unit 80f diagnoses whether or not the drive unit 60a is functioning normally will be described as an example.

[0023] The diagnosing unit 80f transmits a confirmation signal to the driver 60a. If the driver 60a is functioning normally, the driver 60a transmits a response signal to the diagnosis unit 80f in response to the received confirmation signal. If the diagnosis unit 80f receives a response signal in response to the confirmation signal transmitted to the driver 60a, the diagnosis unit 80f diagnoses that the driver 60a is functioning normally. On the other hand, if the diagnosis unit 80f cannot receive a response signal in response to the confirmation signal transmitted to the driver 60a, the diagnosis unit 80f diagnoses that the driver 60a is not functioning normally.

[0024] The diagnosis unit 80f may not receive the response signal from the driving unit 60a for the following reasons, for example. When an abnormality occurs in the drive unit 60a, such as a malfunction of the drive unit 60a.

[0025] When the communication line connecting the command unit 70f including the diagnostic unit 80f and the drive unit 60a is broken. When noise is superimposed on the signal being sent or received over the communication line.

[0026] If noise is superimposed on the confirmation signal sent from the diagnosing unit 80f to the driving unit 60a, the driving unit 60a may not recognize the received signal as a confirmation signal and may not send a response signal to the diagnosing unit 80f. Also, if noise is superimposed on the response signal sent from the driving unit 60a to the diagnosing unit 80f, the diagnosing unit 80f may not recognize the received signal as a response signal.

[0027] Similarly to the driver 60a, the diagnostic unit 80f also diagnoses whether the other drivers 60b to 60d are functioning normally through transmission and reception of signals between the diagnostic unit 80f and the other drivers 60b to 60d.

[0028] Similar to the command unit 70f, the command unit 70r derives a required braking force when a braking request is made. Subsequently, the command unit 70r derives command values for braking forces to be applied to the four wheels 20 based on the required braking force. The command unit 70r can transmit the command values for braking forces to be applied to the four wheels 20 to the four drive units 60, respectively. Similar to the command unit 70f, the command unit 70r has a diagnosis unit 80r (80) that diagnoses whether the four drive units 60 are functioning normally. The diagnosis unit 80r diagnoses whether the four drive units 60 are functioning normally by transmitting and receiving signals to and from the four drive units 60. The command units 70f and 70r share the diagnosis results of the diagnosis units 80f and 80r with each other by transmitting and receiving information to and from each other.

[0029] The required braking force derived by the command unit 70f is the same value as the required braking force derived by the command unit 70r. Furthermore, both of the two command units 70f, 70r can send command values to the four drive units 60a to 60d. Therefore, even if one of the two command units 70f, 70r is unable to send a braking force command value to any of the four drive units 60a to 60d, the other command unit can send a braking force command value to that drive unit. In this respect, it can be said that the braking control device 50 of this embodiment employs a redundant configuration to protect against the occurrence of an abnormality.

[0030] When the braking control device 50 is functioning normally and a braking request is made, the two command units 70f, 70r transmit braking force command values in the following manner. The command unit 70f transmits braking force command values to the drive units 60a, 60b corresponding to the front wheels 20a, 20b, but does not transmit braking force command values to the drive units 60c, 60d corresponding to the rear wheels 20c, 20d. On the other hand, the command unit 70r transmits braking force command values to the drive units 60c, 60d corresponding to the rear wheels 20c, 20d, but does not transmit braking force command values to the drive units 60a, 60b corresponding to the front wheels 20a, 20b. In this respect, the command unit 70f is a CPU mainly for transmitting braking force command values to the front wheels 20a, 20b, and the command unit 70r is a CPU mainly for transmitting braking force command values to the rear wheels 20c, 20d. In other words, the command unit 70f is a CPU that can send braking force command values to the rear wheels 20c, 20d as a backup, and the command unit 70r is a CPU that can send braking force command values to the front wheels 20a, 20b as a backup. In this embodiment, the manner in which the two command units 70f, 70r send braking force command values varies based on the type of abnormality in the brake control device 50 that is classified based on the diagnosis results of the two diagnosis units 80f, 80r.

[0031] <Relationship between diagnosis results by diagnosis unit 80 and backup control> Next, the relationship between the diagnosis result of the diagnosing unit 80 and the transmission mode of the braking force command value of the command unit 70 will be described with reference to Figures 2 and 3. For ease of understanding, attention is focused on two command units 70 (71, 72) and two drive units 60 (61, 62) in Figures 2 and 3.

[0032] 2, the first command unit 71 corresponds to one of the two command units 70f, 70r, and the second command unit 72 corresponds to the other of the two command units 70f, 70r. When the first command unit 71 corresponds to the command unit 70f, the first drive unit 61 corresponds to the drive unit corresponding to the right front wheel 20a or the left front wheel 20b, and the second drive unit 62 corresponds to the drive unit corresponding to the right rear wheel 20c or the left rear wheel 20d. In the above case, the wheel 20 and the braking mechanism 30 corresponding to the first drive unit 61 correspond to the "first wheel" and the "first braking mechanism," respectively, and the wheel 20 and the braking mechanism 30 corresponding to the second drive unit 62 correspond to the "second wheel" and the "second braking mechanism," respectively.

[0033] The diagnosis results obtained by the diagnosis unit 80 include eight patterns shown in FIG. The first pattern is a case where the first diagnostic unit 81 diagnoses that the first drive unit 61 is functioning normally, and the second diagnostic unit 82 diagnoses that the second drive unit 62 is functioning normally. When the pattern of the diagnostic results is the first pattern, the first command unit 71 transmits a first command value, which is a command value for the braking force to be applied to the first wheel, to the first drive unit 61. Furthermore, the second command unit 72 transmits a second command value, which is a command value for the braking force to be applied to the second wheel, to the second drive unit 62. On the other hand, the first command unit 71 does not transmit the second command value to the second drive unit 62. Similarly, the second command unit 72 does not transmit the first command value to the first drive unit 61.

[0034] The first driver 61 drives the first braking mechanism in accordance with the first command value transmitted by the first command unit 71. The second driver 62 drives the second braking mechanism in accordance with the second command value transmitted by the second command unit 72. Note that in the first pattern, the diagnosis result of the second driver 62 by the first diagnostic unit 81 and the diagnosis result of the first driver 61 by the second diagnostic unit 82 do not affect the manner in which the first command unit 71 and the second command unit 72 transmit their command values.

[0035] The second pattern is a case where the first diagnostic unit 81 diagnoses that both the first driver 61 and the second driver 62 are functioning normally, and the second diagnostic unit 82 diagnoses that the second driver 62 is not functioning normally. When the pattern of the diagnostic result is the second pattern, it can be inferred that an abnormality has occurred in the communication between the second command unit 72 and the second driver 62, even though the second driver 62 itself is normal. When the pattern of the diagnostic result is the second pattern, the first command unit 71 transmits a first command value to the first driver 61 and transmits a second command value to the second driver 62. On the other hand, the second command unit 72 does not transmit the first command value to the first driver 61. Similarly, the second command unit 72 does not transmit the second command value to the second driver 62.

[0036] The first driver 61 drives the first braking mechanism in accordance with the first command value transmitted by the first command unit 71. The second driver 62 drives the second braking mechanism in accordance with the second command value transmitted by the first command unit 71. In the second pattern, the diagnosis result of the first driver 61 by the second diagnostic unit 82 does not affect the manner in which the first command unit 71 and the second command unit 72 transmit command values.

[0037] The third pattern is a case where the first diagnostic unit 81 diagnoses that the first drive unit 61 is functioning normally, and both the first diagnostic unit 81 and the second diagnostic unit 82 diagnose that the second drive unit 62 is not functioning normally. When the diagnostic result pattern corresponds to the third pattern, it can be inferred that an abnormality has occurred in the second drive unit 62. When the diagnostic result pattern corresponds to the third pattern, the first command unit 71 increases the first command value according to the magnitude of the second command value. In other words, the first command unit 71 corrects the first command value by increasing it according to the magnitude of the second command value. In this case, the amount of correction to increase the first command value may be the same as the second command value derived by the first command unit 71, or may be the product of the second command value and a predetermined ratio. Note that the predetermined ratio is preferably a positive value less than 1. Then, the first command unit 71 transmits the corrected first command value to the first drive unit 61. In this case, the first command unit 71 does not transmit the second command value to the second drive unit 62. Furthermore, the second command unit 72 does not transmit the first command value to the first driving unit 61. Similarly, the second command unit 72 does not transmit the second command value to the second driving unit 62.

[0038] The first driver 61 then drives the first braking mechanism in accordance with the first command value transmitted by the first command unit 71. In this case, the first wheel is applied with the braking force that would be distributed to the second wheel in addition to the braking force distributed to the first wheel. On the other hand, since the second command value is not transmitted to the second driver 62, the second braking mechanism is not driven. As a result, no braking force is applied to the second wheel. Note that in the third pattern, the diagnosis result of the first driver 61 by the second diagnostic unit 82 does not affect the manner in which the first command unit 71 and the second command unit 72 transmit command values.

[0039] The fourth pattern is a case where the first diagnostic unit 81 diagnoses that the first drive unit 61 is not functioning normally, but the second drive unit 62 is functioning normally. The fourth pattern is a case where the second diagnostic unit 82 diagnoses that the first drive unit 61 is functioning normally, but the second drive unit 62 is functioning normally. When the pattern of the diagnostic result is the fourth pattern, it can be inferred that an abnormality has occurred in the communication between the first command unit 71 and the first drive unit 61, even though the first drive unit 61 itself is functioning normally. It can also be inferred that an abnormality has occurred in the communication between the second command unit 72 and the second drive unit 62, even though the second drive unit 62 itself is functioning normally. When the pattern of the diagnostic result is the fourth pattern, the first command unit 71 transmits a second command value to the second drive unit 62, and the second command unit 72 transmits a first command value to the first drive unit 61. On the other hand, the first command unit 71 does not transmit a first command value to the first drive unit 61. Similarly, the second command unit 72 does not transmit a second command value to the second drive unit 62.

[0040] The first driver 61 drives the first braking mechanism in accordance with the first command value transmitted by the second command unit 72. The second driver 62 drives the second braking mechanism in accordance with the second command value transmitted by the first command unit 71.

[0041] The fifth pattern is when the first diagnostic unit 81 diagnoses that the first drive unit 61 is not functioning normally and the second drive unit 62 is functioning normally. The fifth pattern is when the second diagnostic unit 82 diagnoses that both the first drive unit 61 and the second drive unit 62 are not functioning normally. When the diagnostic result pattern corresponds to the fifth pattern, it is possible to predict that an abnormality has occurred in the first drive unit 61. It is also possible to predict that an abnormality has occurred in the communication between the second command unit 72 and the second drive unit 62, even though the second drive unit 62 itself is functioning normally. When the diagnostic result pattern corresponds to the fifth pattern, the first command unit 71 increases the second command value in accordance with the magnitude of the first command value. In other words, the first command unit 71 increases the second command value in accordance with the magnitude of the first command value. The amount of increase in the second command value in this case may be the same as the first command value derived by the first command unit 71, or may be the product of the first command value and a predetermined ratio. It is preferable that the predetermined ratio is a positive value less than 1. Then, the first command unit 71 transmits the corrected second command value to the second drive unit 62. In this case, the first command unit 71 does not transmit the first command value to the first drive unit 61. Furthermore, the second command unit 72 does not transmit the first command value to the first drive unit 61. Similarly, the second command unit 72 does not transmit the second command value to the second drive unit 62.

[0042] The second driving unit 62 then drives the second braking mechanism in accordance with the second command value transmitted by the first command unit 71. In this case, the braking force that would be distributed to the first wheel is applied to the second wheel in addition to the braking force that would be distributed to the second wheel. On the other hand, since the first command value is not transmitted to the first driving unit 61, the first braking mechanism is not driven. As a result, no braking force is applied to the first wheel.

[0043] The sixth pattern is a case where the first diagnostic unit 81 diagnoses that the first drive unit 61 is not functioning normally, and the second diagnostic unit 82 diagnoses that both the first drive unit 61 and the second drive unit 62 are functioning normally. When the pattern of the diagnostic result is the sixth pattern, the first command unit 71 does not send the first command value to the first drive unit 61. Similarly, the first command unit 71 does not send the second command value to the second drive unit 62. On the other hand, the second command unit 72 sends the first command value to the first drive unit 61 and sends the second command value to the second drive unit 62.

[0044] The first driving unit 61 drives the first braking mechanism in accordance with the first command value transmitted by the second command unit 72. The second driving unit 62 drives the second braking mechanism in accordance with the second command value transmitted by the second command unit 72.

[0045] The seventh pattern is a case where both the first diagnostic unit 81 and the second diagnostic unit 82 diagnose that the first drive unit 61 is not functioning normally, and the second diagnostic unit 82 diagnoses that the second drive unit 62 is functioning normally. When the pattern of the diagnostic results is the seventh pattern, the second command unit 72 increases the second command value according to the magnitude of the first command value. Then, the second command unit 72 transmits the corrected second command value to the second drive unit 62. In this case, the second command unit 72 does not transmit the first command value to the first drive unit 61. Furthermore, the first command unit 71 does not transmit the first command value to the first drive unit 61. Similarly, the first command unit 71 does not transmit the second command value to the second drive unit 62.

[0046] The second driving unit 62 then drives the second braking mechanism in accordance with the second command value transmitted by the second command unit 72. In this case, the braking force that would be distributed to the first wheel is applied to the second wheel in addition to the braking force that is distributed to the second wheel. On the other hand, since the first command value is not transmitted to the first driving unit 61, the first braking mechanism is not driven. As a result, no braking force is applied to the first wheel.

[0047] The eighth pattern is a case where the first diagnostic unit 81 diagnoses that neither the first drive unit 61 nor the second drive unit 62 is functioning normally. Alternatively, the second diagnostic unit 82 diagnoses that the first drive unit 61 is functioning normally, but the second drive unit 62 is functioning normally. When the pattern of the diagnostic result is the eighth pattern, the second command unit 72 increases the first command value in accordance with the magnitude of the second command value. The second command unit 72 then transmits the corrected first command value to the first drive unit 61. In this case, the second command unit 72 does not transmit the second command value to the second drive unit 62. Furthermore, the first command unit 71 does not transmit the first command value to the first drive unit 61. Similarly, the first command unit 71 does not transmit the second command value to the second drive unit 62.

[0048] The first driving unit 61 then drives the first braking mechanism in accordance with the first command value transmitted by the second command unit 72. In this case, the first wheel is applied with the braking force that would be distributed to the second wheel in addition to the braking force distributed to the first wheel. On the other hand, since the second command value is not transmitted to the second driving unit 62, the second braking mechanism is not driven. As a result, no braking force is applied to the second wheel.

[0049] As explained above, if the pattern of the diagnostic results is not the first pattern, it can be determined that the braking control device 50 is not functioning normally. In such a case, the first command unit 71 and the second command unit 72 compensate for the lack of required braking force that occurs when the braking control device 50 is not functioning normally. In the following explanation, the process performed by at least one of the first command unit 71 and the second command unit 72 to compensate for the lack of required braking force in this way will be referred to as "backup control."

[0050] <Processing flow for classifying diagnostic result patterns> 4, a description will be given of the flow of processing executed by the first command unit 71 for each predetermined control cycle when a braking request is not input to the braking control device 50. A process similar to this series of processes is also executed by the second command unit 72. In the description using FIG. 4, one of the two command units 70f, 70r corresponds to the first command unit 71, and the other command unit corresponds to the second command unit 72.

[0051] In the series of processes, in the first step S11, the first command unit 71 diagnoses whether or not the drive unit 60 is functioning normally for each drive unit 60. Then, in step S12, the first command unit 71 communicates with the second command unit 72 to obtain the diagnosis results of the four drive units 60 by the second diagnostic unit 82 of the second command unit 72.

[0052] The second command unit 72 also diagnoses whether or not each drive unit 60 is functioning normally for each drive unit 60. The second command unit 72 communicates with the first command unit 71 to obtain the results of diagnosis of the four drive units 60 by the first diagnostic unit 81 of the first command unit 71.

[0053] In step S13, the first command unit 71 classifies the pattern of the diagnostic result based on the diagnostic result of the first diagnostic unit 81 and the diagnostic result of the second diagnostic unit 82. For example, the first command unit 71 classifies the pattern of the diagnostic result by referring to a table such as that shown in FIG. 3. If the pattern of the diagnostic result is the first pattern, the first diagnostic unit 81 of the first command unit 71 can determine that the braking control device 50 is functioning normally. On the other hand, if the pattern of the diagnostic result is a pattern other than the first pattern, the first diagnostic unit 81 of the first command unit 71 can determine that the braking control device 50 is not functioning normally. Thereafter, the first command unit 71 temporarily ends the series of processes.

[0054] The second diagnostic unit 82 of the second command unit 72 also classifies the patterns of the diagnostic results in the same way as the first diagnostic unit 81. The results of classification by the second diagnostic unit 82 are the same as the results of classification by the first diagnostic unit 81.

[0055] <Processing flow when implementing backup control> Referring to Fig. 5, the flow of processing executed by the first command unit 71 when a braking request is made to the braking control device 50 will be described. The series of processing shown in Fig. 5 is processing that is started when a braking request is made under a situation where some abnormality has occurred in the braking control device 50. Processing similar to this series of processing is also executed by the second command unit 72. In the description using Fig. 5, one of the two command units 70f, 70r corresponds to the first command unit 71, and the other command unit corresponds to the second command unit 72.

[0056] In the series of processes, in the first step S21, the first command unit 71 derives a required braking force. Subsequently, in step S22, the first command unit 71 derives command values for braking forces to be applied to the four wheels 20 based on the required braking force. That is, the first command unit 71 derives a first command value and a second command value. Here, the first command unit 71 derives each command value on the assumption that the braking control device 50 is functioning normally.

[0057] Then, in step S23, the first command unit 71 performs backup control. The first command unit 71 performs backup control according to the pattern of the diagnostic results classified through the execution of the series of processes shown in Fig. 4. For example, if the pattern of the diagnostic results is the second pattern, the first command unit 71 transmits a first command value to the first drive unit 61 and transmits a second command value to the second drive unit 62. If the pattern of the diagnostic results is the fifth pattern, the first command unit 71 increases the second command value according to the magnitude of the first command value and transmits the increased and corrected second command value to the second drive unit 62.

[0058] When backup control is performed in this manner, the first command unit 71 shifts the processing to step S24. In step S24, the first command unit 71 determines whether the required braking force is 0 (zero). That is, the first command unit 71 determines whether the braking request has disappeared. If the required braking force is greater than 0 (zero) (S24: NO), it can be determined that the braking request still exists, and so the first command unit 71 shifts the processing to step S21. On the other hand, if the required braking force is 0 (zero) (S24: YES), it can be determined that the braking request has disappeared, and so the first command unit 71 ends the series of processing.

[0059] <Actions and Effects of the Present Embodiment> If the braking control device 50 is not functioning normally, it may not be possible to apply a braking force equal to the requested braking force to the vehicle 10. In this regard, if the braking control device 50 is diagnosed as not functioning normally, the braking control device 50 performs backup control.

[0060] For example, if an abnormality occurs in communication between the command unit 70f and the drive unit 60a, the command unit 70f will be unable to send a braking force command value to the drive unit 60a, and therefore braking force will not be applied to the right front wheel 20a. In this case, as backup control, the command unit 70r sends a braking force command value to the drive unit 60a. Therefore, the drive unit 60a can drive the braking mechanism 30a based on the command value sent by the command unit 70r. Therefore, even if an abnormality occurs in communication between the command unit 70f and the drive unit 60a, braking force can be applied to the right front wheel 20a.

[0061] Furthermore, if an abnormality occurs in the drive unit 60a, even if the drive unit 60a can receive the command value transmitted by the command unit 70f, it will be unable to drive the brake mechanism 30a. In this case, as backup control, the transmission of the command value to the drive unit 60a is stopped, and the command value transmitted to another drive unit other than the drive unit 60a, for example, the drive unit 60c, is increased. Specifically, the command value to the drive unit 60c is increased according to the magnitude of the command value to the drive unit 60a. The increased command value is then transmitted to the drive unit 60c. The brake mechanism 30c is then driven according to the increased command value. As a result, the braking force applied to the right rear wheel 20c is increased. Therefore, even if braking force cannot be applied to the right front wheel 20a, it is possible to prevent a discrepancy between the actual braking force of the vehicle 10 and the required braking force.

[0062] As described above, when the braking control device 50 is not functioning normally, backup control is performed to prevent a lack of braking force caused by the braking control device 50 not functioning normally. Therefore, even if some abnormality occurs in the braking control device 50, it is possible to adjust the braking force of the vehicle 10 in accordance with the intention of the braking request.

[0063] In this embodiment, the following effects can be further obtained. (1) In the braking control device 50, the diagnostic section 80 that diagnoses whether the drive section 60 is functioning normally is provided in the command control unit 100. Therefore, the drive section 60 can be realized by a simple CPU that only controls the braking mechanism 30 in accordance with the received command value of the braking force.

[0064] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0065] As described above, the command unit 70f transmits a confirmation signal to the drive units 60a and 60b. If the drive units 60a and 60b receive the confirmation signal, it can be determined that the command unit 70f is functioning normally. On the other hand, if the drive units 60a and 60b do not receive the confirmation signal, it can be determined that the command unit 70f is not functioning normally. Therefore, the drive units 60a and 60b may diagnose whether the command unit 70f is functioning normally based on whether they receive the confirmation signal. If the drive units 60a and 60b diagnose that the command unit 70f is not functioning normally, the drive units 60a and 60b may request the command unit 70r to send a command value and drive the braking mechanisms 30a and 30b according to the command value transmitted by the command unit 70r. This allows the braking mechanisms 30a and 30b to be driven even if an abnormality occurs in the command unit 70f. In this case, it can be said that the drive units 60a and 60b have part of the function of a "diagnostic unit." If the drivers 60a, 60b have received a confirmation signal from the command unit 70f, the drivers 60a, 60b may be configured not to accept command values from the command unit 70r. In this way, even if an abnormality occurs in the command unit 70r and an abnormal command value is sent to the drivers 60a, 60b, the drivers 60a, 60b can drive the braking mechanisms 30a, 30b in accordance with the command value from the command unit 70f, which is normal.

[0066] As described above, the command unit 70r transmits a confirmation signal to the drive units 60c and 60d. If the drive units 60c and 60d receive the confirmation signal, it can be determined that the command unit 70r is functioning normally. On the other hand, if the drive units 60c and 60d do not receive the confirmation signal, it can be determined that the command unit 70r is not functioning normally. Therefore, the drive units 60c and 60d may diagnose whether the command unit 70r is functioning normally based on whether they receive the confirmation signal. If the drive units 60c and 60d diagnose that the command unit 70r is not functioning normally, the drive units 60c and 60d may request the command unit 70f to send a command value and drive the braking mechanisms 30c and 30d according to the command value transmitted by the command unit 70f. This allows the braking mechanisms 30c and 30d to be driven even if an abnormality occurs in the command unit 70r. In this case, it can be said that the drive units 60c and 60d have part of the function of a "diagnostic unit." If the drivers 60c, 60d have received a confirmation signal from the command unit 70r, the drivers 60c, 60d may be configured not to accept command values from the command unit 70f. In this way, even if an abnormality occurs in the command unit 70f and an abnormal command value is sent to the drivers 60c, 60d, the drivers 60c, 60d can drive the braking mechanisms 30c, 30d in accordance with the command value from the command unit 70r, which is normal.

[0067] The diagnosis unit 80 may be implemented in a control unit separate from the command unit 70. Also, the command units 70f and 70r may be implemented in separate control units. Furthermore, the command units 70f and 70r and the drive units 60a to 60d may be implemented in the same control unit.

[0068] As explained with reference to Figures 2 and 3, when considering the relationship between two drive units 60 and two command units 70, there is only one type of backup control that can be taken for one diagnostic result pattern. In contrast, when considering the relationship between two command units 70 and four drive units 60, there are multiple types of backup control that can be taken for one diagnostic result pattern. As an example, the following will briefly explain the backup controls that can be implemented by command units 70f and 70r when two diagnostic units 80 diagnose that the drive unit 60a corresponding to the right front wheel 20a is not functioning normally.

[0069] First, as a backup control, the command unit 70r increases the braking force command value for the drive unit 60c in accordance with the magnitude of the braking force command value for the drive unit 60a. In this case, the braking force that would be applied to the right front wheel 20a is applied to the right rear wheel 20c.

[0070] Second, as a backup control, the command unit 70r increases the braking force command value for the drive units 60c, 60d in accordance with the magnitude of the braking force command value for the drive unit 60a. In this case, the braking force that would be applied to the right front wheel 20a is distributed and applied to the right rear wheel 20c and the left rear wheel 20d.

[0071] Third, as backup control, command unit 70f increases the braking force command value for drive unit 60b in accordance with the magnitude of the braking force command value for drive unit 60a. Furthermore, as backup control, command unit 70r increases the braking force command values for drive units 60c and 60d in accordance with the magnitude of the braking force command value for drive unit 60a. In this case, the braking force that would be applied to right front wheel 20a is distributed and applied to left front wheel 20b, right rear wheel 20c, and left rear wheel 20d.

[0072] Fourth, as backup control, the command unit 70r increases the braking force command value for the drive unit 60c in accordance with the magnitude of the braking force command value for the drive unit 60a. Furthermore, as backup control, the command unit 70r increases the braking force command value for the drive unit 60d in accordance with the magnitude of the braking force command value for the drive unit 60b. In this case, the braking force that should be applied to the right front wheel 20a is applied to the right rear wheel 20c, and the braking force that should be applied to the left front wheel 20b is applied to the left rear wheel 20d. In this way, backup control may limit the driving of the brake mechanism 30b by the drive unit 60b that is paired with the drive unit 60a diagnosed as not functioning normally.

[0073] In the above embodiment, the first command unit 71 and the second command unit 72 determine the transmission mode of the braking force command value based on the pattern of the diagnosis result. Thereafter, the first command unit 71 and the second command unit 72 change the magnitude of the braking force command value to be transmitted in accordance with fluctuations in the required braking force, without changing the drive unit 60 to which the braking force command value is transmitted. In contrast, the first command unit 71 and the second command unit 72 may also determine whether the pattern of the diagnosis result changes when changing the magnitude of the braking force command value to be transmitted in accordance with fluctuations in the required braking force. Then, the first command unit 71 and the second command unit 72 may change the transmission mode of the command value when the pattern of the diagnosis result changes. In other words, the first command unit 71 and the second command unit 72 may perform the processes of steps S11 to S13 between steps S22 and S23 in the flowcharts shown in FIGS. 4 and 5.

[0074] When the first command unit 71 cannot receive from the second command unit 72 the diagnosis result of the drive unit 60 made by the second command unit 72, the first command unit 71 may determine that an abnormality has occurred in the second command unit 72. In this case, it is preferable that the first command unit 71 executes backup control similar to the second or fifth pattern shown in FIG.

[0075] The braking mechanism 30 may include a wheel cylinder that presses the friction material 32 against the rotating body 31 more strongly as the hydraulic pressure increases. In this case, the electric motor 33 may adjust the hydraulic pressure in the wheel cylinder to adjust the force with which the friction material 32 is pressed against the rotating body 31.

[0076] The diagnostic unit 80 may have an abnormality detection sensor that detects abnormalities in the drive unit 60, the command unit 70, and the communication lines. In this case, the diagnostic unit 80 may diagnose whether the drive unit 60, the command unit 70, and the communication lines are functioning normally based on the detection results of the abnormality detection sensor.

[0077] The number of wheels 20 in the vehicle 10 does not have to be four. For example, the number of wheels 20 may be two or six. The driving unit 60 is not limited to a unit equipped with a CPU and ROM and executing software processing. For example, it may be equipped with a dedicated hardware circuit that performs hardware processing on at least a portion of the software processing performed in each of the above embodiments. An example of a dedicated hardware circuit is an ASIC. ASIC is an abbreviation for "Application Specific Integrated Circuit." In other words, the driving unit 60 may have any of the following configurations (a) to (c):

[0078] (a) The apparatus comprises a processing device that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (b) It comprises a processing device and a program storage device that execute part of the above processing in accordance with a program, and a dedicated hardware circuit that executes the remaining processing.

[0079] (c) A dedicated hardware circuit is provided for executing all of the above processes. Here, there may be a plurality of software execution devices including a processing device and a program storage device, and a plurality of dedicated hardware circuits.

[0080] The command unit 70 may have any one of the configurations (a) to (c). [Explanation of symbols]

[0081] 10...Vehicle 20(20a~20d)…Wheel 30(30a~30d)…braking mechanism 50...Brake control device 60 (60a to 60d)...Drive unit 61...First drive unit 62...Second drive unit 70(70f,70r)...Command section 71...1st Command Department 72...Second Command Department 80(80f,80r)...Diagnostic Department 81...First Diagnostic Department 82...Second Diagnostic Department 100...Command control unit

Claims

1. A vehicle braking control device applied to a vehicle including a first braking mechanism that applies a braking force to a first wheel and a second braking mechanism that applies a braking force to a second wheel, a first driving unit that applies a braking force to the first wheel by driving the first braking mechanism in accordance with a first command value that is a command value of a braking force to be applied to the first wheel; a second driving unit that applies a braking force to the second wheel by driving the second braking mechanism in accordance with a second command value that is a command value of a braking force to be applied to the second wheel; a first command unit that derives the first command value and the second command value based on a braking request that is a request for braking force for the vehicle, and is capable of transmitting the first command value to the first drive unit and the second command value to the second drive unit; a second command unit that derives the first command value and the second command value based on the braking request, and is capable of transmitting the first command value to the first drive unit and the second command value to the second drive unit; a diagnosis unit that diagnoses whether the braking control device is functioning normally, When the diagnosing unit diagnoses that the braking control device is functioning normally, the first command unit transmits the first command value to the first drive unit; the first driving unit drives the first braking mechanism in accordance with the first command value transmitted by the first command unit; the second command unit transmits the second command value to the second drive unit; the second driving unit is configured to drive the second braking mechanism in accordance with the second command value transmitted by the second command unit, If the diagnosis unit diagnoses that the braking control device is not functioning normally, At least one of the first command unit and the second command unit performs backup control to compensate for a lack of braking force of the vehicle in response to the braking request due to the brake control device not functioning normally. Vehicle braking control device.

2. When the diagnosing unit diagnoses that the first driving unit is not functioning normally, the second command unit transmits, as the backup control, the second command value increased in accordance with the magnitude of the first command value to the second driving unit. The vehicle brake control device according to claim 1.

3. The diagnostic unit a first diagnostic unit provided in the first command unit, which diagnoses whether the first drive unit is functioning normally and diagnoses whether the second drive unit is functioning normally; a second diagnostic unit provided in the second command unit, which diagnoses whether the first drive unit is functioning normally and diagnoses whether the second drive unit is functioning normally, When the first diagnostic unit diagnoses that the first driving unit is functioning normally, the second command unit does not transmit the first command value to the first driving unit, When the first diagnostic unit diagnoses that the first driving unit is not functioning normally and the second diagnostic unit diagnoses that the first driving unit is functioning normally, the second command unit transmits the first command value to the first driving unit as the backup control.

3. A vehicle brake control device according to claim 1 or 2.

4. When the diagnosis unit diagnoses that the first command unit is functioning normally, The first driving unit does not accept the first command value transmitted by the second command unit, and drives the first braking mechanism in accordance with the first command value transmitted by the first command unit. The vehicle braking control device according to any one of claims 1 to 3.

5. the first command unit and the second command unit are implemented in a command control unit, The first drive unit and the second drive unit are mounted in a unit different from the command control unit. The vehicle braking control device according to any one of claims 1 to 4.

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