Brake control device

Abstract

This brake control device (1) comprises a first control unit (110) and a second control unit (120). The first control unit (110) and the second control unit (120) are capable of communicating with each other, and are each capable of executing a temperature estimation process for estimating a temperature state quantity, which is a value relating to the temperature of a brake (FR, FL, RR, RL). When the previous stoppage of the first control unit (110) is due to an abnormality, the first control unit (110), in a temperature estimation process executed first after the current start-up of the first control unit (110), acquires a temperature state quantity from the second control unit (120) and estimates a temperature state quantity using the temperature state quantity acquired from the second control unit (120) as an initial value.

Description

Brake control device

[0001] The present disclosure relates to a brake control device.

[0002] Conventionally, as a brake control device, one control unit that estimates the temperature of a brake is known (see Japanese Patent No. 6393184).

[0003] In a configuration where one control unit estimates the temperature of a brake, for example, if the control unit stops due to an unintended abnormality during vehicle travel, there is a possibility that the temperature of the brake after the next activation of the control unit cannot be accurately estimated.

[0004] Even when the control unit stops due to an unintended abnormality, it is desired to accurately estimate the temperature of the brake after the next activation of the control unit.

[0005] In one aspect, the brake control device includes a first control unit and a second control unit. The first control unit and the second control unit are communicable with each other. The first control unit and the second control unit are each capable of executing a temperature estimation process for estimating a temperature state quantity, which is a value related to the temperature of the brake. When the previous stop of the first control unit was due to an abnormality, in the temperature estimation process that the first control unit first executes after the current activation of the first control unit, the first control unit acquires the temperature state quantity from the second control unit and estimates the temperature state quantity using the temperature state quantity acquired from the second control unit as an initial value.

[0006] Even when the control unit stops due to an unintended abnormality, the temperature of the brake after the next activation of the control unit can be accurately estimated.

[0007] This is a diagram showing the configuration of the brake control device. This is a time chart showing the relationship between estimated pad temperature and termination code. This is a table showing the relationship between termination code and termination cause. This is a table showing how to set initial values ​​according to the termination code. This is a flowchart showing the operation of the control unit. This is a time chart showing an example where the first control unit shuts down during its self-holding time and the second control unit terminates normally after the self-holding time has elapsed. This is a time chart showing an example where the first control unit temporarily shuts down and then recovers while the vehicle is running, and the second control unit continues to estimate the pad temperature even after the first control unit has shut down.

[0008] Next, embodiments will be described in detail with reference to the drawings as appropriate. As shown in Figure 1, the brake control device 1 is a device that controls multiple brakes FR, FL, RR, and RL by generating brake fluid pressure in the wheel cylinder H. The brake control device 1 comprises a first unit U1 and a second unit U2, which are provided with oil passages (hydraulic passages) and various components, a first control unit 110 for controlling the various components in the first unit U1, and a second control unit 120 for controlling the various components in the second unit U2.

[0009] The first unit U1 and the second unit U2 are each equipped with a pressure source 3, two shut-off valves 4, and two pressure regulating means 5. The first unit U1 supplies the hydraulic pressure generated by the pressure source 3 to the wheel cylinders H corresponding to the brakes FL and RR of the left front wheel and right rear wheel. The second unit U2 supplies the hydraulic pressure generated by the pressure source 3 to the wheel cylinders H corresponding to the brakes FR and RL of the right front wheel and left rear wheel.

[0010] The first unit U1 and the second unit U2 each have two unit connection ports 13, a suction port 14, and two wheel cylinder ports 15.

[0011] The wheel cylinder port 15 is connected to the corresponding wheel cylinder H via piping. The wheel cylinder port 15 is connected to the shut-off valve 4 and the pressure regulating means 5 via the hydraulic passage 21.

[0012] The unit connection port 13 is connected to the shut-off valve 4 via the hydraulic passage 22. The unit connection port 13 of the first unit U1 is connected to the unit connection port 13 of the second unit U2 via the unit connection piping 19.

[0013] More specifically, the wheel cylinder H corresponding to the left front wheel and the wheel cylinder H corresponding to the right front wheel are connected via hydraulic passages 21 and 22 in the first unit U1, unit connection piping 19, and hydraulic passages 21 and 22 in the second unit U2. Furthermore, the wheel cylinder H corresponding to the left rear wheel and the wheel cylinder H corresponding to the right rear wheel are connected via hydraulic passages 21 and 22 in the first unit U1, unit connection piping 19, and hydraulic passages 21 and 22 in the second unit U2.

[0014] The suction port 14 is connected to the reservoir tank 7 via the suction hose 16. In other words, the first unit U1 and the second unit U2 are connected to the reservoir tank 7 via the suction hose 16. More specifically, the reservoir tank 7 has two liquid chambers, one of which is connected to the first unit U1 and the other to the second unit U2. The reservoir tank 7 is a brake fluid source that stores brake fluid and is a low-pressure section that is open to atmospheric pressure. The suction port 14 is also connected to the pressure source 3 via the hydraulic passage 23.

[0015] The pressure source 3 is connected to each pressure regulating means 5 via a hydraulic passage 24. Each pressure regulating means 5 is connected to the suction port 14 via a hydraulic passage 25.

[0016] The pressure source 3 consists of a pump 31 and a motor 32 that drives the pump 31. The pressure source 3 draws in brake fluid stored in the reservoir tank 7 and discharges the brake fluid to the pressure regulating means 5.

[0017] The pressure regulating means 5 consists of a pressure boosting control valve 51, a pressure reducing control valve 52, a communication valve 53, and pressure sensors 54 and 55. Based on commands from the corresponding control unit (110 or 120), the pressure regulating means 5 regulates the brake fluid supplied from the pressure source 3. That is, it feeds back the pressure detected by the pressure sensors 54 and 55, opening the pressure boosting control valve 51 and closing the pressure reducing control valve 52 when boosting the pressure, and closing the pressure boosting control valve 51 and opening the pressure reducing control valve 52 when reducing the pressure to obtain the desired pressure. The regulated pressure is output to the wheel cylinder H and the shut-off valve 4 by opening the communication valve 53.

[0018] The shut-off valve 4 opens or closes based on a command from the corresponding control unit, either connecting or disconnecting the hydraulic passage 21 and the hydraulic passage 22. The shut-off valve 4 has a so-called normally open structure, and when there is no command (electrical signal) from the control unit and no power is supplied, it is open, meaning that the hydraulic passage 21 and the hydraulic passage 22 are open and in communication.

[0019] The first control unit 110 and the second control unit 120 are, for example, electronic control units (ECUs) equipped with a CPU, RAM, ROM, and input / output circuits, and perform control by performing various calculation processes based on programs and data stored in the ROM. The first control unit 110 and the second control unit 120 determine the target brake pressure based on the signal from the pedal sensor 91 that detects the amount of operation of the brake pedal BP, and control the pressure source 3 and the pressure regulating means 5 based on the target brake pressure.

[0020] Under normal circumstances, the first control unit 110 and the second control unit 120 close their corresponding shut-off valves 4. If the second control unit 120 fails, the first control unit 110 opens each of the shut-off valves 4 in the first unit U1. At this time, the shut-off valves 4 in the second unit U2 are also opened because no command is received from the second control unit 120. As a result, the pressure regulated by the pressure regulating means 5 of the first unit U1 is applied to the wheel cylinders H corresponding to the left front wheel and right rear wheel, and also to the wheel cylinders H corresponding to the right front wheel and left rear wheel via the unit connection piping 19 and the second unit U2. If the first control unit 110 fails, the second control unit 120 can apply pressure to the wheel cylinders H corresponding to all four wheels by opening each of the shut-off valves 4 in the second unit U2.

[0021] The first control unit 110 and the second control unit 120 are able to communicate with each other. The first control unit 110 and the second control unit 120 are each capable of performing a temperature estimation process to estimate a temperature state quantity, which is a value related to the temperature of the brakes. In this embodiment, the temperature state quantity is the temperature of the brake pads. In the following description, the temperature of the brake pads will also be referred to as "pad temperature".

[0022] The first control unit 110 and the second control unit 120 each estimate the pad temperature of each of the multiple brakes corresponding to the four wheels. The temperature estimation process performed for each brake is the same.

[0023] The functions and configuration of the first control unit 110 for performing temperature estimation processing are described below. Note that the functions and configuration of the second control unit 120 for performing temperature estimation processing are the same as those of the first control unit 110, and therefore their description is omitted.

[0024] As shown in Figure 2, the first control unit 110 starts estimating the pad temperature after the ignition switch IGN is turned ON and the power to the first control unit 110 is turned ON (time t1), and when the vehicle starts moving (time t2). In the following description, the estimated pad temperature will also be referred to as the "estimated pad temperature." The start of vehicle movement can be determined, for example, based on a signal from a wheel speed sensor.

[0025] At time t2, the first control unit 110 first sets an initial value for the estimated pad temperature. The setting of the initial value will be described in detail later.

[0026] After time t2, the first control unit 110 calculates the estimated pad temperature based on the initial value, the amount of heat applied to the brake pad, the amount of heat dissipated from the brake pad, and the amount of heat transferred from the brake pad to other components. For example, a detailed calculation method can be found in the method disclosed in Japanese Patent Publication No. 6393184.

[0027] When the ignition switch IGN is turned OFF (time t3), the first control unit 110 maintains the power ON for a predetermined self-holding time. The first control unit 110 continues to calculate the estimated pad temperature even after the ignition switch IGN is turned OFF.

[0028] As shown by the dashed line in the figure, if the estimated pad temperature falls below the cooling threshold TH during the self-holding time (time t4), the first control unit 110 terminates the calculation of the estimated pad temperature. As shown by the solid line in the figure, if the estimated pad temperature does not fall below the cooling threshold TH during the self-holding time, the first control unit 110 terminates the calculation of the estimated pad temperature and turns off the power after the self-holding time has elapsed following the turning off of the ignition switch IGN (time t5).

[0029] The first control unit 110 has a first memory M1 and a second memory M2. The first memory M1 is, for example, a non-volatile memory. The second memory M2 is, for example, RAM.

[0030] As shown in Figure 3, the first control unit 110 has a function to store a numerical value from 1 to 4 in the first memory M1 as an exit code Ea indicating the reason for the termination (stopping) of the first control unit 110. The first control unit 110 has a function to set the exit code Ea to 0 if it is unable to read the exit code Ea from the first memory M1.

[0031] If "1" is stored as the termination code Ea, it indicates that the first control unit 110 has terminated due to an unintended shutdown while the vehicle is in motion. If "2" is stored as the termination code Ea, it indicates that the first control unit 110 has terminated due to an unintended shutdown during the self-holding time.

[0032] If "3" is stored as the termination code Ea, it indicates that the first control unit 110 has terminated normally after the self-holding time has elapsed. If "4" is stored as the termination code Ea, it indicates that the first control unit 110 has terminated normally after the estimated pad temperature fell below the cooling threshold TH during the self-holding time.

[0033] In other words, if the exit code Ea is 1 or 2, it indicates that the first control unit 110 terminated due to an abnormality in the previous operation. If the exit code Ea is 3 or 4, it indicates that the first control unit 110 terminated normally in the previous operation.

[0034] As shown in Figure 2, when the vehicle starts moving (time t2), the first control unit 110 reads the exit code Ea from the first memory M1 to set the initial value of the estimated pad temperature. Here, "R" in the figure indicates reading and "W" indicates writing.

[0035] The first control unit 110 stores the termination code Ea read from the first memory M1 at the start of vehicle operation in the second memory M2. For example, as shown in the figure, if the termination code Ea read from the first memory M1 at the start of vehicle operation is "3", the first control unit 110 stores the termination code Ea (=3) in the second memory M2. This ensures that the previous termination cause is retained for the duration of the current power-on. If the first control unit 110 fails to read from the first memory M1 at the start of vehicle operation, it sets the termination code Ea to 0 and stores the set termination code Ea in the second memory M2.

[0036] Furthermore, when the vehicle starts running, the first control unit 110 reads the termination code Ea from the first memory M1 to the second memory M2, and then changes the termination code Ea in the first memory M1 to "1" (time t2). As a result, while the vehicle is running, the termination code Ea in the first memory M1 will be "1", so if an unintended shutdown occurs while the vehicle is running, the power to the first control unit 110 will be turned OFF with the termination code Ea stored in the first memory M1 set to "1".

[0037] When the ignition switch IGN is turned OFF (time t3), the first control unit 110 changes the exit code Ea in the first memory M1 to "2". As a result, during the self-holding time, the exit code Ea in the first memory M1 will be "2", so if an unintended shutdown occurs during the self-holding time, the power to the first control unit 110 will be turned OFF with the exit code Ea stored in the first memory M1 set to "2". Also, when the ignition switch IGN is turned OFF, the first control unit 110 writes the estimated pad temperature at that time to the first memory M1.

[0038] If the estimated pad temperature falls below the cooling threshold TH during the self-holding time (time t4), the first control unit 110 changes the exit code Ea of the first memory M1 to "4" and writes the estimated pad temperature at that time to the first memory M1. If the self-holding time elapses without the estimated pad temperature falling below the cooling threshold TH (time t5), the first control unit 110 changes the exit code Ea of the first memory M1 to "3" and writes the estimated pad temperature at that time to the first memory M1.

[0039] Next, the method for setting the initial values ​​used for estimating the pad temperature will be explained. When the first control unit 110 starts estimating the pad temperature, it reads the exit code Ea from the first memory M1. As shown in Figure 4, if the read exit code Ea is either 1 or 2, or if the exit code Ea cannot be read and is set to 0, the first control unit 110 obtains the exit code Eb held in the second memory M2 of the second control unit 120 via communication and sets the initial values ​​based on the exit codes Ea and Eb. If the read exit code Ea is 3 or greater, the first control unit 110 sets the initial values ​​based only on the exit code Ea.

[0040] If the exit code Ea is 0 and the exit code Eb is less than 3, the first control unit 110 sets a predetermined value pre-stored in the first memory M1 as the initial value. Here, the predetermined value can be set to, for example, a higher temperature at which a fade phenomenon may occur.

[0041] If the exit code Ea is 0 and the exit code Eb is 3 or greater, the first control unit 110 obtains the estimated pad temperature calculated by the second control unit 120 from the second control unit 120 and sets the obtained estimated pad temperature as the initial value. In other words, if the first control unit 110 is unable to read the exit code Ea from the first memory M1 (Ea = 0), and assuming that the second control unit 120 terminated successfully last time (Eb ≥ 3), in the temperature estimation process that is first executed after the first control unit 110 is started, the first control unit 110 obtains the estimated pad temperature from the second control unit 120 and uses the estimated pad temperature obtained from the second control unit 120 as the initial value to estimate the pad temperature.

[0042] In this embodiment, the pad temperature obtained by the first control unit 110 from the second control unit 120 is the highest pad temperature among the pad temperatures calculated for each of the multiple brakes. Alternatively, the first control unit 110 may obtain the pad temperatures for all four wheels from the second control unit 120 and use the pad temperature corresponding to a predetermined wheel as the initial value for that wheel.

[0043] When the end code Ea is 1 and the end code Eb is less than 3, the first control unit 110 sets a predetermined value stored in the first memory M1 in advance as an initial value. That is, when the previous stop of the first control unit 110 was due to an abnormality that occurred before the ignition switch IGN was turned off and the previous stop of the second control unit 120 was due to an abnormality, in the temperature estimation process that is first executed after the current activation of the first control unit 110, the pad temperature is estimated using the predetermined value as the initial value.

[0044] When the end code Ea is 1 and the end code Eb is 3 or more, the first control unit 110 acquires the estimated pad temperature being calculated by the second control unit 120 from the second control unit 120, and sets the acquired estimated pad temperature as the initial value. That is, when the previous stop of the first control unit 110 was due to an abnormality (Ea = 1), on the condition that the second control unit 120 ended normally last time (Eb≥3), in the temperature estimation process that is first executed after the current activation of the first control unit 110, the estimated pad temperature is acquired from the second control unit 120, and the estimated pad temperature is estimated using the estimated pad temperature acquired from the second control unit 120 as the initial value.

[0045] When the end code Ea is 2 and the end code Eb is less than 3, the first control unit 110 reads the estimated pad temperature stored in the first memory M1, and sets the read estimated pad temperature as the initial value. That is, when the previous stop of the first control unit 110 was due to an abnormality that occurred after the ignition switch IGN was turned off and before the elapse of a predetermined self-holding time, and the previous stop of the second control unit 120 was due to an abnormality, in the temperature estimation process that is first executed after the current activation of the first control unit 110, the pad temperature is estimated using the estimated pad temperature stored in the first control unit 110 as the initial value. Here, the estimated pad temperature stored in the first memory M1 when the end code Ea is 2 is the estimated pad temperature calculated when the previous ignition switch IGN was turned off.

[0046] When the end code Ea is 2 and the end code Eb is 3 or more, the first control unit 110 acquires the estimated pad temperature being calculated by the second control unit 120 from the second control unit 120, and sets the acquired estimated pad temperature as the initial value. That is, when the previous stop of the first control unit 110 was due to an abnormality (Ea = 2), and on the condition that the second control unit 120 ended normally last time (Eb ≧ 3), in the temperature estimation process that the first control unit 110 first executes after starting this time, the first control unit 110 acquires the estimated pad temperature from the second control unit 120, and estimates the estimated pad temperature using the estimated pad temperature acquired from the second control unit 120 as the initial value.

[0047] When the end code Ea is 3 or 4, that is, when the first control unit 110 ends normally, the first control unit 110 reads the estimated pad temperature stored in the first memory M1, and sets the read estimated pad temperature as the initial value. Here, the estimated pad temperature stored in the first memory M1 when the end code Ea is 3 is the estimated pad temperature calculated when the previous self-holding time elapsed. Also, the estimated pad temperature stored in the first memory M1 when the end code Ea is 4 is the estimated pad temperature when the previous estimated pad temperature became equal to or lower than the cooling threshold value TH.

[0048] Next, an example of the initial value setting process by the first control unit 110 will be described with reference to FIG. 5. When the running of the vehicle is started, the first control unit 110 executes the process shown in FIG. 5.

[0049] In the process shown in FIG. 5, the first control unit 110 determines whether the initial value has been set (S1). If it is determined in step S1 that the initial value has been set (Yes), the first control unit 110 ends this process.

[0050] If it is determined in step S1 that no initial value has been set (No), the first control unit 110 determines whether its own exit code Ea is 3 or greater (S2). If it is determined in step S2 that Ea ≥ 3 (Yes), the first control unit 110 reads the estimated pad temperature stored in its first memory M1 and sets the read estimated pad temperature as the initial value (S6).

[0051] If it is determined in step S2 that Ea ≥ 3 (No), the first control unit 110 determines whether the exit code Eb of the second control unit 120 is 3 or greater (S3). If it is determined in step S3 that Eb ≥ 3 (Yes), the first control unit 110 obtains the estimated pad temperature calculated by the second control unit 120 and sets the obtained estimated pad temperature as the initial value (S7).

[0052] If it is determined in step S3 that Eb ≥ 3 (No), the first control unit 110 determines whether its own exit code Ea is 2 (S4). If it is determined in step S4 that Ea = 2 (Yes), the first control unit 110 sets the estimated pad temperature stored in its first memory M1 as the initial value (S8).

[0053] If step S4 determines that Ea is not 2 (No), the first control unit 110 sets a predetermined value stored in its first memory M1 as the initial value (S5). After steps S5 to S8, the first control unit 110 terminates this process.

[0054] The second control unit 120 can perform the same processing as shown in Figure 5. In the processing performed by the second control unit 120, Ea and Eb in Figure 5 should be swapped.

[0055] Next, a specific example of the operation of the first control unit 110 will be described. The specific example shown in Figure 6 is an example in which the first control unit 110 terminates due to an unintended shutdown during its self-holding time, and the second control unit 120 terminates normally after the self-holding time has elapsed.

[0056] During the self-holding period (times t11 to t13), the first memory M1 of the first control unit 110 stores the termination code Ea (=2) and the estimated pad temperature Tp1 that were written when the ignition switch IGN was turned OFF (time t11). Therefore, if the first control unit 110 terminates due to an unintended shutdown during the self-holding period (time t12), the termination code Ea (=2) and the estimated pad temperature Tp1 are retained in the first memory M1.

[0057] On the other hand, when the second control unit 120 terminates normally due to the elapsed self-holding time (time t13), the first memory M1 of the second control unit 120 stores the termination code Eb (=3) and the estimated pad temperature Tp2. Here, the estimated pad temperature Tp2 has dropped to a temperature lower than the estimated pad temperature Tp1 when the ignition switch IGN is OFF.

[0058] Subsequently, when the ignition switch IGN is turned ON (time t21) and the vehicle starts moving (time t22), the first control unit 110 and the second control unit 120 each begin estimating the pad temperature.

[0059] The first control unit 110 reads the exit code Ea (=2) from its first memory M1 into the second memory M2 and stores it there. Similarly, the second control unit 120 reads the exit code Eb (=3) from its first memory M1 into the second memory M2 and stores it there.

[0060] Since the exit code Eb read by the second control unit 120 is "3", the second control unit 120 determines Yes in step S2 and sets the estimated pad temperature Tp2 read from its first memory M1 as the initial value (S6). After that, the second control unit 120 starts calculating the estimated pad temperature based on the initial value.

[0061] Since the exit code Ea read by the first control unit 110 is "2", the first control unit 110 determines No in step S2 and determines whether the exit code Eb of the second memory M2 of the second control unit 120 is 3 or greater (S3). Since the exit code Eb of the second memory M2 of the second control unit 120 is "3", the first control unit 110 determines Yes in step S3 and sets the estimated pad temperature calculated by the second control unit 120 as the initial value (S7). Specifically, the first control unit 110 sets the largest estimated pad temperature among the multiple estimated pad temperatures calculated by the second control unit 120 as the initial value. After that, the first control unit 110 starts calculating the estimated pad temperature based on the initial value.

[0062] This allows the first control unit 110, which terminated due to an abnormality last time, to calculate an estimated pad temperature equivalent to that of the second control unit 120, which terminated normally last time.

[0063] The specific example shown in Figure 7 is an example in which the first control unit 110 temporarily shuts down due to an unintended shutdown while the vehicle is in motion, then resumes operation, and the second control unit 120 continues to estimate the pad temperature even after the first control unit 110 has shut down. As a premise for the specific example in Figure 7, it is assumed that the first control unit 110 and the second control unit 120 have shut down normally in the previous operation (for details, Ea = 3, Eb = 3).

[0064] When the ignition switch IGN is turned ON (time t31) and the vehicle starts moving (time t32), the first control unit 110 and the second control unit 120 each start estimating the pad temperature.

[0065] The first control unit 110 reads the exit code Ea (=3) from its first memory M1 into the second memory M2 and stores it there. Similarly, the second control unit 120 reads the exit code Eb (=3) from its first memory M1 into the second memory M2 and stores it there.

[0066] Since both exit codes Ea and Eb are "3", the first control unit 110 and the second control unit 120 set the estimated pad temperature stored in the first memory M1 as the initial value in step S6 and calculate the pad temperature. Also, when the vehicle starts running, the first control unit 110 and the second control unit 120 each change the exit codes Ea and Eb in their own first memory M1 from "3" to "1".

[0067] While the vehicle is in motion, the first memory M1 of the first control unit 110 stores the exit code Ea (=1). Therefore, if the first control unit 110 shuts down unexpectedly while the vehicle is in motion (time t33), the exit code Ea (=1) is retained in the first memory M1. Subsequently, when the power to the first control unit 110 is restored (time t34), the first control unit 110 reads the exit code Ea (=1) from its own first memory M1.

[0068] Since the read exit code Ea is "1", the first control unit 110 determines No in step S2 and obtains the exit code Eb (=3) of the second memory M2 from the second control unit 120. Since the exit code Eb of the second memory M2 in the second control unit 120 is "3", the first control unit 110 determines Yes in step S3 and sets the estimated pad temperature Tp5 calculated by the second control unit 120 as the initial value (S7). Specifically, the first control unit 110 sets the largest estimated pad temperature among the multiple estimated pad temperatures calculated by the second control unit 120 as the initial value.

[0069] This allows the first control unit 110, which has temporarily shut down while the vehicle is in motion, to calculate an estimated pad temperature equivalent to that of the second control unit 120, which is operating normally.

[0070] As described above, the following effects can be obtained according to this embodiment. If the previous shutdown of the first control unit 110 was due to an abnormality, the first control unit 110 will use the pad temperature obtained from the second control unit 120 as an initial value to estimate the pad temperature. Therefore, even if the first control unit 110 is shut down due to an unintended abnormality, it will be able to accurately estimate the pad temperature after the first control unit 110 is started up again.

[0071] If the previous shutdown of the first control unit 110 occurred after the estimated pad temperature had fallen below the cooling threshold TH, that is, if it was not due to an abnormality, the pad temperature will be estimated using the pad temperature it has stored as an initial value, allowing for a rapid estimation of the pad temperature.

[0072] If the previous shutdown of the first control unit 110 was caused by the elapsed time since the ignition switch IGN was turned OFF exceeding a predetermined self-holding time, that is, if it was not due to an abnormality, the pad temperature will be estimated using the pad temperature stored in the unit as the initial value, thus enabling rapid estimation of the pad temperature.

[0073] If the previous shutdown of the second control unit 120 was due to an abnormality, the first control unit 110 estimates the pad temperature based on the pad temperature it has stored or a predetermined value, without obtaining the pad temperature from the second control unit 120, thus enabling rapid estimation of the pad temperature. Furthermore, if the previous shutdown of the first control unit 110 was due to an abnormality that occurred after the ignition switch IGN was turned OFF but before a predetermined self-holding time had elapsed, the pad temperature stored in the first control unit 110 will be lower than the pad temperature during driving due to the time elapsed since driving. In such cases, the first control unit 110 estimates the pad temperature based on the pad temperature it has stored, so it can estimate the pad temperature without significantly reducing the accuracy of the pad temperature estimation.

[0074] If the previous shutdown of the first control unit 110 was due to an abnormality that occurred before the ignition switch IGN was turned OFF, the pad temperature stored in the first control unit 110 may be a relatively high value, such as the pad temperature during driving. In such cases, the first control unit 110 estimates the pad temperature based on a predetermined value it has stored, so safety can be ensured by setting the predetermined value to a high value for safety reasons.

[0075] Since the pad temperature acquired by the first control unit 110 from the second control unit 120 is the highest pad temperature among the pad temperatures calculated for each of the multiple brakes, the communication load can be reduced compared to, for example, a configuration in which the first control unit acquires the pad temperature for each of the multiple brakes from the second control unit.

[0076] The above-described embodiment can be modified and implemented in various forms, as illustrated below. The brake is not limited to a brake operated by a brake pedal, but may also be an electric parking brake operated by a parking switch, for example. Furthermore, the brake control device is not limited to a configuration having an oil passage (hydraulic passage), but may also be an electric brake device that generates braking force by driving an electric motor during normal driving, for example.

[0077] The temperature state variable is not limited to the pad temperature; for example, it may be the temperature of a component of the brake system whose temperature rises in response to the braking force.

[0078] The elements described in the above embodiments and modifications may be implemented in any combination.

[0079] This disclosure can be summarized as follows: A brake control device according to a first aspect of this disclosure comprises a first control unit and a second control unit. The first control unit and the second control unit are able to communicate with each other. The first control unit and the second control unit are each capable of performing a temperature estimation process to estimate a temperature state quantity, which is a value related to the temperature of the brake. If the previous stop of the first control unit was due to an abnormality, the first control unit obtains a temperature state quantity from the second control unit in the temperature estimation process that is first performed after the start of the first control unit, and estimates the temperature state quantity using the temperature state quantity obtained from the second control unit as an initial value.

[0080] According to the first embodiment, if the previous shutdown of the first control unit was due to an abnormality, the first control unit estimates the temperature state quantity using the temperature state quantity obtained from the second control unit as an initial value. Therefore, even if the first control unit is shut down due to an unintended abnormality, it is possible to accurately estimate the temperature state quantity after the first control unit is started up again.

[0081] Furthermore, in a second aspect of the present disclosure, the first control unit performs the following processing in the first aspect. If the previous shutdown of the first control unit occurred after the temperature state quantity fell below a cooling threshold, the first control unit estimates the temperature state quantity using the temperature state quantity stored in the first control unit as an initial value in the temperature estimation process that is first executed after the startup of the first control unit.

[0082] According to the second embodiment, if the previous shutdown of the first control unit occurred after the temperature state quantity fell below the cooling threshold, that is, if it was not due to an abnormality, the temperature state quantity is estimated using the temperature state quantity stored by the unit itself as an initial value, so that the temperature state quantity can be estimated quickly.

[0083] Furthermore, in a third aspect of the present disclosure, in any of the above aspects, the first control unit performs the following processing: If the previous shutdown of the first control unit was caused by the elapsed time since the ignition switch was turned OFF being equal to or greater than a predetermined self-holding time, the first control unit estimates the temperature state quantity using the temperature state quantity stored in the first control unit as an initial value in the temperature estimation processing that is first executed after the startup of the first control unit.

[0084] According to the third embodiment, if the previous shutdown of the first control unit was caused by the elapsed time since the ignition switch was turned OFF exceeding a predetermined self-holding time, that is, if it was not due to an abnormality, the temperature state quantity is estimated using the temperature state quantity stored by the unit itself as an initial value, so that the temperature state quantity can be estimated quickly.

[0085] Furthermore, in a fourth aspect of the present disclosure, in any of the above aspects, the first control unit performs the following processing: If the previous shutdown of the first control unit was due to an abnormality that occurred after the ignition switch was turned OFF but before a predetermined self-holding time had elapsed, and the previous shutdown of the second control unit was due to an abnormality, the first control unit estimates the temperature state quantity using the temperature state quantity stored in the first control unit as an initial value in the temperature estimation process that is first executed after the current startup of the first control unit. If the previous shutdown of the first control unit was due to an abnormality that occurred before the ignition switch was turned OFF, and the previous shutdown of the second control unit was due to an abnormality, the first control unit estimates the temperature state quantity using a predetermined value as an initial value in the temperature estimation process that is first executed after the current startup of the first control unit.

[0086] According to the fourth embodiment, if the previous shutdown of the second control unit was due to an abnormality, the first control unit does not acquire the temperature state quantity from the second control unit, but instead estimates the temperature state quantity based on the temperature state quantity it has stored or a predetermined value, thereby enabling rapid estimation of the temperature state quantity. Furthermore, if the previous shutdown of the first control unit was due to an abnormality that occurred after the ignition switch was turned OFF but before a predetermined self-holding time had elapsed, the temperature state quantity stored in the first control unit will be lower than the temperature state quantity at the time of driving due to the passage of time since driving. In such cases, the first control unit estimates the temperature state quantity based on the temperature state quantity it has stored, so it can estimate the temperature state quantity without significantly reducing the accuracy of the temperature state quantity estimation.

[0087] If the previous shutdown of the first control unit was due to an abnormality that occurred before the ignition switch was turned OFF, the temperature state value stored in the first control unit may be a relatively high value, such as the temperature state value during driving. In such cases, the first control unit estimates the temperature state value based on a predetermined value it has stored, so safety can be ensured by setting the predetermined value to a high value for safety reasons.

[0088] Furthermore, in a fifth aspect of the present disclosure, in any of the above aspects, the first control unit and the second control unit perform the following processing: The first control unit and the second control unit are each capable of calculating the temperature state quantity for each of the multiple brakes, and the temperature state quantity obtained by the first control unit from the second control unit is the highest temperature state quantity among the temperature state quantities calculated for each of the multiple brakes.

[0089] According to the fifth embodiment, for example, compared to a configuration in which the first control unit acquires temperature state quantities corresponding to each of the multiple brakes from the second control unit, the communication load can be reduced.

Claims

1. A brake control device comprising a first control unit and a second control unit that can communicate with each other, wherein the first control unit and the second control unit are each capable of performing a temperature estimation process to estimate a temperature state quantity which is a value relating to the temperature of the brake, and the first control unit, if the previous stop of the first control unit was due to an abnormality, obtains a temperature state quantity from the second control unit in the temperature estimation process that is first performed after the start of the first control unit, and uses the temperature state quantity obtained from the second control unit as an initial value to estimate the temperature state quantity.

2. The brake control device according to claim 1, characterized in that, if the previous shutdown of the first control unit occurred after the temperature state quantity fell below a cooling threshold, the first control unit uses the temperature state quantity stored in the first control unit as an initial value to estimate the temperature state quantity in the temperature estimation process that is first executed after the startup of the first control unit this time.

3. The brake control device according to claim 1, characterized in that, if the previous shutdown of the first control unit was caused by the elapsed time since the ignition switch was turned OFF exceeding a predetermined self-holding time, the first control unit uses the temperature state quantity stored in the first control unit as an initial value to estimate the temperature state quantity in the temperature estimation process that is first executed after the startup of the first control unit this time.

4. The brake control device according to claim 1, characterized in that, if the previous stop of the first control unit was due to an abnormality that occurred after the ignition switch was turned OFF but before a predetermined self-holding time had elapsed, and the previous stop of the second control unit was due to an abnormality, the first control unit estimates the temperature state quantity using the temperature state quantity stored in the first control unit as an initial value in the temperature estimation process that is first executed after the current startup of the first control unit, and if the previous stop of the first control unit was due to an abnormality that occurred before the ignition switch was turned OFF, and the previous stop of the second control unit was due to an abnormality, the first control unit estimates the temperature state quantity using a predetermined value as an initial value in the temperature estimation process that is first executed after the current startup of the first control unit.

5. The brake control device according to claim 1, characterized in that the first control unit and the second control unit are each capable of calculating the temperature state quantity for each of the multiple brakes, and the temperature state quantity obtained by the first control unit from the second control unit is the highest temperature state quantity among the temperature state quantities calculated for each of the multiple brakes.

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