Brake control device

Abstract

The present invention provides a brake control device for an electric vehicle, which realizes the improvement of the regeneration efficiency in the constant speed downhill function. The brake control device comprises: a slope sensor for detecting the road slope; an operating unit capable of switching the constant speed downhill function to be effective; a brake control unit for controlling a first regeneration unit capable of generating regenerative power from the braking torque of the front wheels and a second regeneration unit capable of generating regenerative power from the braking torque of the rear wheels; and a storage unit for storing an efficiency map representing the relationship between the action of the first regeneration unit and the regeneration efficiency, and the relationship between the action of the second regeneration unit and the regeneration efficiency. When the constant speed downhill function is effective, the brake control unit calculates the brake torque distribution of the front and rear wheels based on the detected road slope and the efficiency map so that the comprehensive regeneration efficiency satisfies the first condition (S6), and uses the calculated brake torque distribution to control the first regeneration unit and the second regeneration unit (S8).

Description

Technical Field

[0001] The invention relates to a brake control device for an electric vehicle. Background Art

[0002] Patent Document 1 discloses a technology that controls the regenerative braking torque of the front and rear wheels and the braking force of the hydraulic brakes in a hybrid vehicle having front and rear wheel motors when going downhill, thereby improving the efficiency of energy recovery.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2004-166363 Summary of the invention

[0006] Technical issues

[0007] In recent years, vehicles having a constant speed downhill function that automatically controls the braking force in order to maintain a constant vehicle speed when going downhill have been used. The constant speed downhill function allows the driver to drive the vehicle downhill at a predetermined vehicle speed without performing a brake operation.

[0008] However, even when the constant speed downhill function is enabled, it is less necessary to strictly control the vehicle speed to a pre-specified speed, and a slight speed change is usually allowed. In addition, by using regenerative braking for the constant speed downhill function, the regenerative energy can be used to extend the cruising distance of the electric vehicle.

[0009] An object of the present invention is to provide a brake control device for an electric vehicle that aims to improve the regenerative efficiency in a constant speed downhill function.

[0010] Technical Solution

[0011] The invention of a first aspect is a brake control device, characterized by comprising:

[0012] a slope sensor that detects the slope of the road;

[0013] An operating unit capable of switching the constant speed downhill function to be effective;

[0014] a brake control unit that controls a first regeneration unit capable of generating regenerative power from a brake torque of the front wheels and controls a second regeneration unit capable of generating regenerative power from a brake torque of the rear wheels; and

[0015] a storage unit storing an efficiency map indicating a relationship between an operation of the first regenerating unit and a regeneration efficiency, and a relationship between an operation of the second regenerating unit and a regeneration efficiency,

[0016] When the constant speed downhill function is set to be effective, the braking control unit calculates the braking torque distribution of the front wheels and the rear wheels based on the detected road slope and the efficiency map so that the comprehensive regeneration efficiency satisfies the first condition, and uses the calculated braking torque distribution to control the first regeneration unit and the second regeneration unit.

[0017] The invention of a second aspect is the brake control device according to the first aspect, wherein the brake control unit calculates the brake torque distribution by giving a parameter of a vehicle speed a width.

[0018] The invention of a third aspect is a brake control device according to the first aspect or the second aspect, characterized in that:

[0019] When the road slope changes during the execution of the constant speed descent function, the braking control unit sets the vehicle speed to a parameter that gives the vehicle speed at that moment an amplitude and performs the calculation of the braking torque distribution again, and is able to perform a first control process for controlling the first regeneration unit and the second regeneration unit using the calculated braking torque distribution.

[0020] The invention of a fourth aspect is characterized in that, in the brake control device according to the third aspect,

[0021] When the road gradient changes during the execution of the constant speed downhill function, the brake control unit can select whether to execute the first control process or the second control process for maintaining the vehicle speed.

[0022] The invention of a fifth aspect is the brake control device of the fourth aspect, wherein the brake control unit selects to execute the first control process when the regeneration efficiency of the first control process is higher than the regeneration efficiency of the second control process by a threshold value or more.

[0023] The invention of a sixth aspect is characterized in that, in the brake control device according to the fourth aspect or the fifth aspect,

[0024] The brake control device further includes a setting operation unit capable of performing a setting operation.

[0025] The brake control unit selects whether to execute the first control process or the second control process based on the setting by the setting operation unit.

[0026] [Effects of the invention]

[0027] According to the present invention, when the constant speed downhill function is enabled, the brake torque distribution of the regenerative braking of the front wheels and the regenerative braking of the rear wheels is calculated according to the efficiency map and the road slope, and the first regeneration unit and the second regeneration unit are controlled based on the calculated brake torque distribution. Therefore, the regeneration efficiency can be improved when the constant speed downhill function is executed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a block diagram showing the configuration of an electric vehicle according to an embodiment of the present invention.

[0029] Figure 2 is a diagram showing an example of a regenerative braking efficiency map. Figure 2 (a) is the efficiency map of the front wheel, Figure 2 (b) is the efficiency map of the rear wheel, Figure 2 (c) is the efficiency map of the front and rear wheels.

[0030] Figure 3 This is a flowchart showing an example of a constant speed downhill process executed by the brake control unit.

[0031] Figure 4 This is an explanatory diagram showing an example of transition of the running state of an electric vehicle using the constant speed downhill function.

[0032] Explanation of symbols

[0033] 1 Electric Vehicles

[0034] 2a Front wheel

[0035] 2b Rear wheel

[0036] 3a First travel motor (first regeneration unit)

[0037] 3b Second travel motor (second regeneration unit)

[0038] 4a, 4b Converter

[0039] 5. Batteries

[0040] 10 Driving Operation

[0041] 15 Functional operation section

[0042] 16 First function switch (operating part)

[0043] 17 ECO switch

[0044] 18 Speed ​​setting switch

[0045] 19 Setting operation section

[0046] 21 Vehicle speed sensor

[0047] 22 Slope sensor

[0048] 30 Vehicle Control Unit

[0049] 31 Brake control unit

[0050] 32 Storage

[0051] 33 Efficiency Mapping

[0052] 50 Braking mechanism

[0053] 52 Braking unit

[0054] 53. Drive unit DETAILED DESCRIPTION

[0055] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 It is a block diagram showing the configuration of an electric vehicle according to an embodiment of the present invention. Figure 2 is a diagram showing an example of a regenerative braking efficiency map. Figure 2 (a) is the efficiency map of the front wheel, Figure 2 (b) is the efficiency map of the rear wheel, Figure 2 (c) is the efficiency map of the front and rear wheels.

[0056] The electric vehicle 1 of this embodiment includes: a front wheel 2a and a rear wheel 2b; a first travel motor 3a that drives the front wheel 2a; a second travel motor 3b that drives the rear wheel 2b; an inverter 4a that drives the first travel motor 3a; an inverter 4b that drives the second travel motor 3b; a battery 5 that supplies power for driving to the inverters 4a and 4b; a braking mechanism 50 that generates braking force on the front wheel 2a, the rear wheel 2b, or both; a slope sensor 22 that detects the slope of the road; and a vehicle speed sensor 21 that detects the vehicle speed.

[0057] The electric vehicle 1 further includes: a driving operation unit 10 including a brake pedal 11, an accelerator pedal 12, and a steering wheel 13; a function operation unit 15 for switching between effectiveness and ineffectiveness of various functions; and a vehicle control unit 30 for controlling the electric vehicle 1. The vehicle control unit 30 includes: a brake control unit 31 for performing regenerative control of the first travel motor 3a and the second travel motor 3b and controlling the brake mechanism 50; and a storage unit 32 for storing various control data. The storage unit 32 includes an efficiency map 33, which indicates the relationship between the operation (wheel speed and regenerative braking torque) of the first travel motor 3a and the regenerative efficiency, and the relationship between the operation (wheel speed and regenerative braking torque) of the second travel motor 3b and the regenerative efficiency.

[0058] exist Figure 1In the embodiment, the combination of the brake control unit 31, the storage unit 32, the sensors (vehicle speed sensor 21, slope sensor 22, etc.) and the function operation unit 15 is equivalent to an example of the brake control device of the present invention. The first travel motor 3a is equivalent to an example of the first regeneration unit of the present invention, and the second travel motor 3b is equivalent to an example of the second regeneration unit of the present invention.

[0059] The first travel motor 3a and the inverter 4a can perform power operation and regeneration operation, and generate driving force by power operation and braking force by regeneration operation. The driving force and braking force are transmitted to the front wheel 2a. The first travel motor 3a is an electric motor, and during regeneration operation, the regenerated power is transmitted to the battery 5 via the inverter 4a. Figure 2 As shown in (a), the regenerative efficiency of the first travel motor 3a varies, for example, between 60% and 80% depending on the wheel speed of the front wheel 2a and the regenerative braking torque. The regenerative efficiency indicates the ratio of the regenerative energy to the braking energy.

[0060] The second travel motor 3b and the inverter 4b can perform power operation and regeneration operation, generating driving force by power operation and generating braking force by regeneration operation. The driving force and braking force are transmitted to the rear wheel 2b. The second travel motor 3b is an electric motor, and during regeneration operation, the regenerated power is transmitted to the battery 5 via the inverter 4b. Figure 2 As shown in (b), the regenerative efficiency of the second travel motor 3b varies, for example, between 60% and 80% depending on the wheel speed of the rear wheel 2b and the regenerative braking torque. The specifications of the first travel motor 3a and the second travel motor 3b may be different. In this case, the efficiency map 33 of the regenerative efficiency of the first travel motor 3a and the efficiency map 33 of the regenerative efficiency of the second travel motor 3b are different.

[0061] The efficiency map 33 stored in the storage unit 32 may be Figure 2 (a) Figure 2 The two independent mapping data of the front wheel 2a and the rear wheel 2b shown in (b) are as follows. Figure 2 As shown in (c), the efficiency map 33 may also be mapping data indicating the relationship between the braking torque distribution (the regenerative braking torque of the front wheel 2a and the regenerative braking torque of the rear wheel 2b), the wheel speed, and the comprehensive regenerative efficiency. The braking torque distribution refers to the combination of the regenerative braking torque of the front wheel 2a and the regenerative braking torque of the rear wheel 2b. Figure 2 The mapping data of (c) can be based on Figure 2 (a) Figure 2 It is obtained by using the mapping data of (b).

[0062] The battery 5 is, for example, a lithium ion secondary battery or a nickel-metal hydride secondary battery. The electric vehicle 1 may be an HEV (Hybrid Electric Vehicle) having an internal combustion engine, and in this case, the battery 5 may be a lead storage battery.

[0063] The brake mechanism 50 includes a brake unit 52 such as a caliper brake or a drum brake that applies a braking force to the front wheel 2a, the rear wheel 2b, or both, and a master cylinder 51 and a hydraulic circuit that transmits the operation of the brake pedal 11 to the brake unit 52. A drive unit 53 that adjusts the hydraulic pressure under the control of the brake control unit 31 is provided in the hydraulic circuit.

[0064] The function operation unit 15 includes: a first function switch (equivalent to the operation unit of the present invention) 16 for switching between the effectiveness and ineffectiveness of the constant speed downhill function; an ECO switch 17 for switching between the effectiveness and ineffectiveness of the ECO mode; a vehicle speed setting switch 18 for setting the vehicle speed of the constant speed downhill function; and a setting operation unit 19 for performing option settings, etc. The function operation unit 15 is configured to be operable by the driver. A display element that enables the driver to visually confirm the selection status of each switch by using a lamp or an output of a display panel can be provided on the instrument panel, etc.

[0065] The constant speed downhill function is a function for automatically controlling the braking force in a manner to maintain the set vehicle speed without operating the brake pedal 11 when going downhill. The set vehicle speed may be a vehicle speed pre-set by the driver or user via the vehicle speed setting switch 18 within a predetermined range, a default vehicle speed, or a vehicle speed determined based on the vehicle speed at the time when the function is switched to be effective. However, the vehicle speed controlled by the constant speed downhill function is limited to a low-medium speed (e.g., 5km / h to 40km / h).

[0066] The ECO mode switched by the ECO switch 17 is a mode that gives priority to improving energy efficiency. The control of the constant speed downhill function when the ECO mode is invalid is different from that when the ECO mode is valid. For example, in the constant speed downhill function when the ECO mode is invalid, the constant speed downhill control is mainly based on the control of the brake mechanism 50. In the constant speed downhill function when the ECO mode is valid, the constant speed downhill control is mainly based on the regenerative braking.

[0067] The vehicle control unit 30 receives detection signals from the vehicle speed sensor 21 and the slope sensor 22, and operation signals from the driving operation unit 10, and controls the converters 4a, 4b and the brake mechanism 50 based on these signals. The brake control unit 31 in the vehicle control unit 30 is responsible for the regenerative operation of the converters 4a, 4b and the drive control of the brake mechanism 50. The vehicle control unit 30 can be composed of one ECU (Electronic Control Unit) or a plurality of ECUs that communicate with each other and work in collaboration. The control program is executed by the CPU (Central Processing Unit) of the ECU, so that normal driving control is achieved by using the vehicle control unit 30. The control program includes a program for the constant speed downhill processing executed by the brake control unit 31.

[0068] <Constant speed downhill handling>

[0069] Figure 3 This is a flowchart showing an example of a constant speed downhill process executed by the brake control unit.

[0070] The constant speed downhill process is started by switching the first function switch 16 to valid. If the constant speed downhill process is started, the brake control unit 31 first confirms whether the road currently being traveled is a downhill road based on the output of the slope sensor 22 (step S1), and then determines whether the current vehicle speed is the speed allowed by the constant speed downhill function (for example, below 40 km / h) (step S2). If the judgment results of steps S1 and S2 are that it is not a downhill road or exceeds the allowed speed, the brake control unit 31 switches the first function switch 16 to invalid (step S3) and ends the constant speed downhill process. On the other hand, if it is a downhill road and the speed is allowed, the brake control unit 31 advances the process downward.

[0071] If the vehicle is pushed downward, the brake control unit 31 obtains the set speed of the constant speed downhill function (step S4). Before the first function switch 16 is switched to be effective, if the driver performs a setting operation for the vehicle speed of the constant speed downhill function, the brake control unit 31 reads the set vehicle speed in step S4. In addition, when the vehicle speed when the first function switch 16 is effective is set as the set speed, the brake control unit 31 obtains the current vehicle speed as the set vehicle speed in step S4.

[0072] Next, the brake control unit 31 determines whether the ECO mode is selected according to the operation of the ECO switch 17 (step S5). As a result, if the ECO mode is not selected, the brake control unit 31 transfers the processing to the normal constant speed downhill control (step S20), but if the ECO mode is selected, the processing enters the constant speed downhill control that prioritizes regeneration efficiency (steps S6 to S16).

[0073] Although detailed description is omitted for the processing of the normal constant speed downhill control in step S20, the brake control unit 31 controls the brake mechanism 50 to maintain the vehicle speed at the set speed. In the normal constant speed downhill control, the brake control unit 31 may be configured to simultaneously use the regenerative control if the chargeable power of the battery 5 is large (if the charging rate is low), and not to perform the regenerative control or to reduce the ratio of the regenerative control if the chargeable power of the battery 5 is small.

[0074] If the control is transferred to the constant speed downhill control with priority on the regeneration efficiency, first, the brake control unit 31 calculates the brake torque distribution that satisfies the predetermined condition (equivalent to the first condition of the present invention) for improving the regeneration efficiency based on the efficiency map 33 and the output of the slope sensor 22 (step S6). As the predetermined condition for improving the regeneration efficiency, for example, a condition that the regeneration efficiency becomes the highest, or a condition that is within a range from the highest regeneration efficiency to several percent, etc. can be used.

[0075] In the calculation of step S6, the brake control unit 31 does not fix the vehicle speed at the set speed, but processes the vehicle speed into a parameter having a predetermined amplitude at the set speed. For example, the brake control unit 31 sets the vehicle speed to a parameter v1 (v1 = 15 ± 2 [km / h]) having a predetermined amplitude (e.g., ± 2 [km / h]) at the set speed (e.g., 15 [km / h]). Next, the brake control unit 31 calculates the total braking torque Trbtot that maintains the vehicle speed constant based on the road slope, the vehicle speed, and the known vehicle weight, and sets the regenerative braking torque Trbfr of the front wheel 2a and the regenerative braking torque Trbrr of the rear wheel 2b to parameters that satisfy Trbtot = Trbfr + Trbrr. Then, the brake control unit 31 searches the range represented by the above-mentioned vehicle speed parameter v1 and the parameters Trbfr and Trbrr of the regenerative braking torque of the front wheel 2a and the rear wheel 2b in the efficiency map 33, and obtains the mapping position with the highest comprehensive regeneration efficiency. When the map position is obtained, the vehicle speed and the braking torque distribution (the regenerative braking torque of the front wheels 2a and the regenerative braking torque of the rear wheels 2b) corresponding thereto are uniquely obtained.

[0076] When the vehicle speed and the braking torque distribution are calculated, the brake control unit 31 sets these calculation results as target values ​​to be controlled (step S7 ), and then proceeds to the loop process of the constant speed downhill control (steps S8 to S11 ).

[0077] In the loop processing, first, the brake control unit 31 controls the converters 4a and 4b based on the value of the vehicle speed sensor 21 to generate regenerative braking torques for the front wheels 2a and the rear wheels 2b in a manner that makes the vehicle speed, the regenerative braking torque of the front wheels 2a, and the regenerative braking torque of the rear wheels 2b consistent with the respective target values ​​(step S8).

[0078] Next, the brake control unit 31 determines whether the release condition of the constant speed downhill function is met (step S9). The release condition refers to the end of the downhill road slope or the execution of the release operation. The release operation refers to, for example, the operation of the brake pedal 11, the operation of the accelerator pedal, or the operation of switching the first function switch 16 to invalid. If the release condition is met, the brake control unit 31 switches the first function switch 16 to invalid (step S3) and ends the constant speed downhill processing. On the other hand, if the release condition is not met, the brake control unit 31 advances the processing downward.

[0079] If the vehicle is moving downward, the brake control unit 31 checks the state of the battery 5 and determines whether the chargeable power of the battery 5 is below the threshold value (step S10). If the result of the determination is yes, the brake control unit 31 transfers the process to the normal constant speed downhill control (step S20) because the regenerative energy cannot be accumulated. On the other hand, if the result of the determination in step S10 is no, the brake control unit 31 causes the process to move downward.

[0080] If the vehicle is moving downward, the brake control unit 31 determines whether the road slope has changed based on the output of the slope sensor 22 (step S11). It should be noted that in step S11, the brake control unit 31 may determine that a slight change (for example, a change below a threshold value such as 2 degrees or less) is no change. If the result of the determination is that the road slope has not changed, the brake control unit 31 returns the process to step S8 and continues the loop process of steps S8 to S11. On the other hand, if the road slope has changed, the brake control unit 31 temporarily exits the loop process.

[0081] If the road gradient changes and the loop process is temporarily exited, the brake control unit 31 calculates the brake torque distribution again using two methods (steps S12 and S13).

[0082] In the calculation process A of step S12, the brake control unit 31 sets the vehicle speed to a parameter having a range at the current speed, and calculates the brake torque distribution to improve the regeneration efficiency based on the output of the slope sensor 22 and the efficiency map 33. If the recalculation of step S12 is compared with the calculation of step S6, the value of the total brake torque Trbtot for maintaining the vehicle speed constant is different due to the change in the slope. In addition, the vehicle speed parameter v2 is changed to a value (16.5±2[km / h]) having a predetermined range (for example, ±2[km / h]) at the current vehicle speed (the vehicle speed of the calculation result of step S8 (for example, 16.5[km / h])). In step S12, the brake control unit 31 searches the range of the above parameters in the efficiency map 33, and finds the mapping position where the comprehensive regeneration efficiency is the highest. In addition, the brake control unit 31 obtains the vehicle speed (for example, 14.5[km / h]) and the brake torque distribution as the calculation result according to the mapping position.

[0083] In the calculation process B of step S13, the brake control unit 31 fixes the vehicle speed at the current speed and sets only the brake torque distribution as a variable parameter to calculate the brake torque distribution that improves the regeneration efficiency. The calculation of step S13 is the same as the calculation of step S12, except that the vehicle speed has no amplitude and is set to a fixed value. The calculation result of step S13 is to find the brake torque distribution that improves the regeneration efficiency when the vehicle speed is fixed.

[0084] If the calculation process A of step S12 and the calculation process B of step S13 are performed, the brake control unit 31 calculates how much the comprehensive regeneration efficiency of the result of the calculation process A is improved compared with the comprehensive regeneration efficiency of the result of the calculation process B, and determines whether the improvement in the regeneration efficiency is greater than a preset second threshold value (step S14). And, if the judgment result of step S14 is yes, the brake control unit 31 sets the result of the calculation process A as the target value to be controlled (step S15). On the other hand, if the judgment result of step S14 is no, the brake control unit 31 sets the result of the calculation process B as the target value to be controlled (step S16).

[0085] That is, through steps S12 to S16, when the road slope changes, if the comprehensive regeneration efficiency is greatly improved, the constant speed downhill control of the first control process that allows the change of the vehicle speed and gives priority to improving the regeneration efficiency is executed. On the other hand, if the comprehensive regeneration efficiency does not change greatly, the constant speed downhill control of the second control process that gives priority to maintaining the vehicle speed is executed. It should be noted that the first control process and the second control process are not only selected based on the amount of improvement in the regeneration efficiency, but can also be configured such that, for example, the user such as the driver can select to execute only the first control process, only the second control process, or a selection based on the amount of improvement in the regeneration efficiency according to the option setting performed using the setting operation unit 19.

[0086] If a new target value is set in step S15 or step S16, the brake control unit 31 returns to the loop process of the constant speed downhill control (steps S8 to S11). In this loop process, the brake control unit 31 performs regenerative control in a manner that realizes the vehicle speed and brake torque distribution of the newly set target value.

[0087] In the loop process of steps S8 to S11 , when the downhill slope is completed or the constant speed downhill slope control is released by the operation of the brake pedal 11 or the accelerator pedal 12 , the constant speed downhill slope control is completed via the process of step S3 .

[0088] Figure 4 1 is an explanatory diagram showing an example of transition of the running state of the electric vehicle 1 using the constant speed hill descent function. Figure 4 An example of a travel in which the electric vehicle 1 starts descending a slope with the constant speed descending function enabled and the road gradient changes during the descent is shown.

[0089] If the control process giving priority to regeneration efficiency is executed in the constant speed downhill process, Figure 4 As shown in the downhill condition J1, at the beginning of the downhill, there is a situation where the vehicle speed slightly deviates from the set speed V0 and the electric vehicle 1 runs. However, the vehicle speed is not fixed, and accordingly, the braking torque distribution that can further improve the regeneration efficiency can be calculated. Moreover, when the road slope changes, such as Figure 4 As shown in the downhill condition J2, there is a situation where the electric vehicle 1 is driven with a slight change in vehicle speed from the speed V1 before the slope change. However, the vehicle speed is not fixed, and accordingly, the braking torque distribution that can further improve the regeneration efficiency can be calculated. In addition, by improving the regeneration efficiency, the battery charging rate can be increased, thereby extending the cruising distance of the electric vehicle 1.

[0090] As described above, the electric vehicle 1 and its brake control device according to the present embodiment are provided with: a slope sensor 22; a first travel motor 3a capable of generating a regenerative braking torque at the front wheel 2a; a second travel motor 3b capable of generating a regenerative braking torque at the rear wheel 2b; a brake control unit 31 capable of controlling the regenerative operation; and a storage unit 32 storing the efficiency map 33 of the regenerative braking. Furthermore, when the constant speed downhill function is set to be effective, the brake control unit 31 calculates the brake torque distribution of the front wheel 2a and the rear wheel 2b (using the brake torque distribution of the regenerative braking) that improves the comprehensive regenerative efficiency based on the road slope and the efficiency map, and controls the regenerative braking based on the calculation result. Therefore, when the constant speed downhill function is executed, the regenerative efficiency can be improved and the cruising distance of the electric vehicle 1 can be extended.

[0091] Moreover, according to the electric vehicle 1 and its brake control device of the present embodiment, in the constant speed downhill control with priority on regeneration efficiency, the brake control unit 31 makes the parameter of the vehicle speed have an amplitude and performs the calculation of the brake torque distribution (step S6). Therefore, the vehicle speed sometimes deviates slightly from the speed set for the constant speed downhill function, and on the other hand, correspondingly, the distribution of the regenerative braking torque of the front wheel 2a and the rear wheel 2b with high regeneration efficiency can be achieved. As a result, the regeneration efficiency when executing the constant speed downhill function can be improved, and the cruising range of the electric vehicle 1 can be extended.

[0092] Moreover, according to the electric vehicle 1 and its brake control device of the present embodiment, when the road slope changes during the constant speed downhill function, the brake control unit 31 performs the calculation of the brake torque distribution with an amplitude at the current vehicle speed as a parameter of the vehicle speed (step S12). Therefore, when the road slope changes during the constant speed downhill function, the vehicle speed sometimes changes slightly. On the other hand, correspondingly, the distribution of the regenerative braking torque of the front wheel 2a and the rear wheel 2b with high regeneration efficiency can be achieved in accordance with the change in the road slope. Thus, even when the road slope changes during the constant speed downhill function, the regeneration efficiency can be improved, and the cruising range of the electric vehicle 1 can be extended.

[0093] Furthermore, according to the electric vehicle 1 and the brake control device thereof of the present embodiment, when the road slope changes during the constant speed downhill function, the first control process (steps S12, S15, S8) for allowing the vehicle speed to change and the second control process (steps S13, S16, S8) for maintaining the vehicle speed constant are selectively executed. Therefore, the constant speed downhill function can be realized, which is suitable for the situation where it is good to maintain the vehicle speed constant and the situation where the vehicle speed should be allowed to change slightly to achieve the improvement of the regeneration efficiency.

[0094] Moreover, according to the electric vehicle 1 and its brake control device of the present embodiment, when the road slope changes in the constant speed downhill function, the brake control unit 31 calculates how much the regeneration efficiency of the first control process that allows the vehicle speed to change is improved compared to the regeneration efficiency of the second control process that maintains the vehicle speed constant. Then, the brake control unit 31 determines whether the increase in the regeneration efficiency is above the second threshold (step S14). When the increase in the regeneration efficiency is above the second threshold, the first control process (steps S15 and S8) is executed. On the other hand, when the increase in the regeneration efficiency is less than the second threshold, the brake control unit 31 executes the second control process (steps S16 and S8). Therefore, if the regeneration efficiency changes significantly, the speed change in the constant speed downhill function is allowed, and the regeneration efficiency can be improved first. On the other hand, if the regeneration efficiency does not change significantly, the vehicle speed can be maintained first.

[0095] Furthermore, according to the electric vehicle 1 and the brake control device thereof of the present embodiment, the user can select the control process when the road slope changes during the constant speed downhill function by setting the options using the setting operation unit 19. Therefore, the control process corresponding to the user's request can be selected for the change of the road slope during the constant speed downhill function.

[0096] The above is a description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. For example, in the above embodiments, an example is shown in which the parameters of the vehicle speed have an amplitude and the braking torque distribution for improving the regeneration efficiency is obtained when the constant speed downhill control starts and when the road slope changes. However, the time when the parameters of the vehicle speed have an amplitude and the braking torque distribution for improving the regeneration efficiency is obtained can be various times such as only when the constant speed downhill control starts, only when the road slope changes, or a time corresponding to other conditions in the constant speed downhill control. In addition, the details shown in the embodiments, such as the size of the variation amplitude given to the parameters of the vehicle speed when calculating the braking torque distribution, can be appropriately changed within the scope of the main purpose of the invention.

Claims

1. A brake control device, characterized in that: have: a slope sensor that detects the slope of the road; An operating unit capable of switching the constant speed downhill function to be effective; a brake control unit that controls a first regeneration unit capable of generating regenerative power from a brake torque of the front wheels and controls a second regeneration unit capable of generating regenerative power from a brake torque of the rear wheels; as well as a storage unit storing an efficiency map indicating a relationship between an operation of the first regenerating unit and a regeneration efficiency, and a relationship between an operation of the second regenerating unit and a regeneration efficiency, The brake control unit calculates the brake torque distribution of the front wheels and the rear wheels based on the detected road slope and the efficiency map so that the comprehensive regeneration efficiency satisfies a predetermined first condition for improving the regeneration efficiency when the constant speed downhill function is enabled, and controls the first regeneration unit and the second regeneration unit using the calculated brake torque distribution. When the road slope changes during the execution of the constant speed downhill function, the brake control unit sets the vehicle speed to a parameter that makes the vehicle speed at that moment have a magnitude and performs the calculation of the brake torque distribution again, and can perform a first control process of controlling the first regeneration unit and the second regeneration unit using the calculated brake torque distribution, When the road gradient changes during the execution of the constant speed downhill function, the brake control unit can select whether to execute the first control process or the second control process for maintaining the vehicle speed.

2. The brake control device according to claim 1, characterized in that: The brake control unit calculates the brake torque distribution by giving a parameter of a vehicle speed a range.

3. The brake control device according to claim 1, characterized in that: The brake control unit selects and executes the first control process when the regeneration efficiency of the first control process is higher than the regeneration efficiency of the second control process by a threshold value or more.

4. The brake control device according to claim 2, characterized in that: The brake control unit selects and executes the first control process when the regeneration efficiency of the first control process is higher than the regeneration efficiency of the second control process by a threshold value or more.

5. The brake control device according to any one of claims 1 to 4, characterized in that: The brake control device further includes a setting operation unit capable of performing a setting operation. The brake control unit selects whether to execute the first control process or the second control process based on the setting by the setting operation unit.

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