Vehicle brake control device

Abstract

To securely brake while securing a relatively large amount of power regeneration and preventing rusting.SOLUTION: A vehicle brake control device comprises: brake force control means which performs a brake force control distributing regenerative brake torque of a regenerative brake and friction brake torque of a friction brake by a prescribed brake torque distribution, and uses a different torque distribution before and after a vehicle speed reaches the regeneration limit speed during deceleration; rusting determination means which estimates a friction coefficient of a friction engagement element to determine a rusting state of the friction engagement element; validity determination means which determines validity of the determination result of the rusting state by the rusting determination means on the basis of at least one detection result of vibration of the friction engagement element and sound generated from the friction engagement element; and descaling control means which configures, on the basis of the determination result of the validity determination means, the brake torque distribution in a period of time when the vehicle speed reaches the regeneration limit speed during deceleration.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a braking control device for a vehicle capable of generating braking force by regenerative braking using a motor generator. [Background technology]

[0002] Conventionally, in vehicles such as hybrid vehicles, braking control devices are known that obtain the desired braking force by combining a friction brake, which generates a braking force on the wheels by operating a friction engagement element using hydraulic pressure or the like, and a regenerative brake, which generates a braking force on the wheels by operating a motor generator as a generator.

[0003] In such a vehicle braking control device (vehicle control device), rust on the brake rotor may progress if the proportion of braking force due to regenerative braking increases. Therefore, Patent Document 1 discloses a technology that prohibits regenerative braking when rust on the brake rotor is detected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-143104 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology disclosed in the above-mentioned Patent Document 1 may result in a decrease in the amount of regenerated power.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a vehicle braking control device that can perform reliable braking while preventing rust and ensuring a relatively large amount of power regeneration by controlling the ratio of braking torque between regenerative brakes and friction brakes based on the amount of deviation in deceleration and an estimated value of the friction coefficient of the friction brakes. [Means for solving the problem]

[0007] A vehicle braking control device according to one embodiment of the present invention is a braking control device for a vehicle having a motor generator as a driving source for a power unit, and comprises: a braking force control means that coordinates a regenerative brake using the motor generator and a friction brake using a friction engagement element to control braking force by distributing the regenerative braking torque due to the regenerative brake and the friction braking torque due to the friction brake at a predetermined braking torque distribution, and sets different braking torque distributions before and after the vehicle speed reaches the regenerative limit speed during deceleration; a rust determination means that estimates the friction coefficient of the friction engagement element and determines the rust state of the friction engagement element; a validity determination means that determines the validity of the determination result of the rust state by the rust determination means based on the detection results of at least one of the vibration of the friction engagement element and the sound emitted from the friction engagement element; and a rust removal control means that sets the braking torque distribution for the period until the vehicle speed reaches the regenerative limit speed during deceleration based on the determination result of the validity determination means. Effect of the Invention

[0008] According to the vehicle braking control device of the present invention, it is possible to ensure a relatively large amount of regenerative power, prevent rust, and perform reliable braking. [Brief description of the drawings]

[0009] [Figure 1] Schematic diagram of a hybrid vehicle [Diagram 2] Brake actuator configuration diagram [Diagram 3] FIG. 1 is a diagram for explaining an example of a method for estimating the temperature of a brake pad. [Figure 4] Flowchart showing control during deceleration [Diagram 5] Flowchart showing braking torque distribution control taking into account the presence or absence of rust [Figure 6] An explanatory diagram showing braking torque distribution control taking into account the presence or absence of rust. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. In this embodiment, the occurrence of rust is judged based on an estimated value of the friction coefficient between the pad and rotor taking into account temperature, and the validity of this judgment result is judged based on vibration, scraping noise, etc., and the ratio of the braking torque due to the friction brake to the total braking force during braking (hereinafter referred to as the friction brake ratio) is changed based on this judgment result and the judgment result of the deceleration deviation amount. This makes it possible to prevent rust and ensure reliable braking while securing a relatively large regenerative power.

[0011] Although the present embodiment will be described taking a hybrid vehicle as an example, the present invention can be applied to various vehicles that use both regenerative braking and friction braking.

[0012] A vehicle 1 shown in FIG. 1 is, for example, a hybrid vehicle, and a power unit PU of this vehicle 1 has an engine 2 and a motor generator 4 connected to an output shaft of the engine 2 with an automatic transmission 3 interposed therebetween.

[0013] In this embodiment, the vehicle 1 shown in Fig. 1 is a four-wheel drive vehicle, and the output shaft of the automatic transmission 3 is connected to the left and right front wheels 5fl, 5fr and the left and right rear wheels 5rl, 5rr. Each wheel 5fl, 5fr, 5rl, 5rr (hereinafter collectively referred to as "each wheel 5") is provided with a wheel cylinder 8fl, 8fr, 8rl, 8rr (hereinafter collectively referred to as "each wheel cylinder 8") equipped with a friction engagement element such as a disc brake. In Fig. 1, Dc denotes a center differential device, Df denotes a front differential device, and Dr denotes a rear differential device.

[0014] The control system that controls the running of the vehicle 1 includes a hybrid control unit (HEV_CU) 10, an engine control unit (ECU) 11, a transmission control unit (TCU) 12, a power control unit (PCU) 13 incorporating an inverter 13a, and a brake control unit (BCU) 14. These control units 10 to 14 are connected to each other so as to be able to communicate with each other via a CAN (Controller Area Network) or the like.

[0015] Various sensors are connected to the input side of the HEV_CU 10, such as an accelerator sensor 15 serving as an accelerator operation detection means for detecting the state of operation of the accelerator pedal 15a by the driver, and a brake sensor 16 serving as a brake operation detection means for detecting the state of braking operation of the brake pedal 16a by the driver.

[0016] The accelerator sensor 15 is capable of detecting, for example, the operation speed of the accelerator pedal 15a, and whether the accelerator pedal 15a is fully open or fully closed, etc. The brake sensor 16 is capable of detecting, for example, the operation speed of the brake pedal 16a, and whether the brake pedal 16a is fully open or fully closed, etc.

[0017] The HEV_CU 10 calculates torque required for the engine 2 and the motor generator 4 based on signals from various sensors, for example, and performs overall drive control of the engine 2 and the motor generator 4.

[0018] The HEV_CU 10 also controls switching of the driving mode through control of various clutches (not shown) provided in the automatic transmission 3. The HEV_CU 10 can switch the driving mode to any one of an EG mode in which the vehicle runs solely on the engine 2, an HEV mode in which the vehicle runs jointly on the engine 2 and the motor generator 4, and an EV mode in which the vehicle runs solely on the motor generator 4.

[0019] Furthermore, the HEV_CU 10, which serves as a braking force control means, is capable of performing braking force control, etc., by engine braking using the engine 2, regenerative braking by the motor generator 4, friction braking by operation of each wheel cylinder 8, or a combination of these.

[0020] In this braking force control, the HEV_CU 10 acquires a target deceleration. That is, for example, during coasting, the HEV_CU 10 calculates a target deceleration based on a signal (accelerator opening degree, etc.) from the accelerator sensor 15. Also, for example, when the HEV_CU 10 detects the driver's depression of the brake pedal based on a signal from the brake sensor 16, the HEV_CU 10 calculates a target deceleration based on signals from first and second brake fluid pressure sensors 59a, 59b, etc., which will be described later. Furthermore, in the vehicle 1 equipped with a driving support device (not shown), the HEV_CU 10 acquires a target deceleration for automatic brake control, etc., calculated by the driving support device.

[0021] Then, the HEV_CU10 calculates the necessary braking torque from the acquired target deceleration, for example. Furthermore, the HEV_CU10 calculates each distribution value (engine braking torque, regenerative braking torque, and friction braking torque) for distributing the calculated necessary braking torque to the engine brake, the regenerative brake, and the friction brake according to the running state of the host vehicle 1, and outputs a control signal based on each calculated distribution value to each control unit 11 to 14.

[0022] Further, sensors 9fl, 9fr, 9rl, 9rr (hereinafter collectively referred to as "each sensor 9") for detecting sounds and vibrations generated near the wheel cylinders 8fl, 8fr, 8rl, 8rr are provided, for example, on each wheel 5fl, 5fr, 5rl, 5rr. The results of the detection of sounds and vibrations by each sensor 9 are supplied to the HEV_CU 10. Further, the vehicle 1 is provided with a temperature sensor 19 for measuring the outside air temperature, and the temperature sensor 19 outputs the result of the temperature detection to the HEV_CU 10.

[0023] The ECU 11 receives control information such as required torque from the HEV_CU 10, as well as detection information from various sensors (not shown) such as a crank angle sensor provided in the engine 2. Based on this input information, the ECU 11 drives the engine 2 by controlling the fuel injection amount, ignition timing, and various devices such as an electronically controlled throttle valve.

[0024] The TCU 12 receives control information from the HEV_CU 10, as well as detection information from various sensors (not shown), such as a shift position sensor provided on a shift lever and a vehicle speed sensor. Based on this input information, the TCU 12 performs hydraulic control applied to each element of the automatic transmission 3, such as a clutch, to control the gear ratio of the automatic transmission 3.

[0025] During braking, the TCU 12 cooperates with the ECU 11 to perform a predetermined gear shift control, thereby generating a braking force (engine braking torque) by engine braking.

[0026] The PCU 13 receives control information such as required torque from the HEV_CU 10, and also acquires from the inverter 13a the current value, voltage value, and various sensor signals flowing through the motor generator 4. The PCU 13 then drives the motor generator 4 by converting DC power from the battery 7 into AC power through control over the inverter 13a.

[0027] Furthermore, during deceleration, the PCU 13 controls the inverter 13a to cause the motor generator 4 to function as a generator, converting AC power regenerated by the motor generator 4 into DC power and charging the battery 7. When the motor generator 4 functions as a generator, a regenerative braking force is applied to each wheel 5 by the regenerative brake. Note that this regenerative braking force is applied to the driving wheels, but since the vehicle 1 of this embodiment is a four-wheel drive vehicle, a regenerative braking force (regenerative braking torque) is applied to all of the wheels 5.

[0028] The BCU 14 receives control information from the HEV_CU 10, as well as detection information from various sensors such as wheel speed sensors 17fl, 17fr, 17rl, and 17rr (hereinafter collectively referred to as "wheel speed sensors 17") that detect the wheel speeds of the wheels 5, and a longitudinal acceleration sensor 18. Based on this input information, the BCU 14 controls the drive of each wheel cylinder 8 through brake fluid pressure control for the brake actuator 6, thereby generating a frictional braking force (frictional braking torque) on each wheel 5.

[0029] Here, the brake actuator 6 is mainly constituted by a brake fluid pressure circuit 42 connected to a brake fluid pressure generating section 41, for example, as shown in FIG.

[0030] The brake fluid pressure generating unit 41 has a master cylinder 44, a reservoir tank 45 attached to the master cylinder 44, and a brake booster 46 interposed between the brake pedal 16a and the master cylinder 44. A pressure medium (oil) is stored in the reservoir tank 45. The brake pedal 16a is connected to the brake booster 46 via an operating rod 48.

[0031] A master cylinder 44 of the brake fluid pressure generating unit 41 is connected via a brake fluid pressure circuit 42 to wheel cylinders 8fl, 8fr, 8rl, and 8rr provided on the wheels 5fl, 5fr, 5rl, and 5rr of the vehicle.

[0032] The brake hydraulic circuit 42 is composed of two hydraulic lines, a first hydraulic circuit 52 and a second hydraulic circuit 53. The brake hydraulic circuit 42 according to this embodiment is of a cross piping (X piping) type in which the first hydraulic circuit 52 and the second hydraulic circuit 53 are arranged diagonally across the vehicle 1. That is, in the brake hydraulic circuit 42 according to this embodiment, the first hydraulic circuit 52 is connected to the wheel cylinders 8fl, 8rr of the left front wheel and the right rear wheel arranged in one diagonal direction of the vehicle 1, and the second hydraulic circuit 53 is connected to the wheel cylinders 8fr, 8rl of the right front wheel and the left rear wheel arranged in the other diagonal direction of the vehicle 1.

[0033] In addition, since the first hydraulic circuit 52 and the second hydraulic circuit 53 have the same configuration, the same reference numerals are appropriately used to simplify the explanation below. In addition, in explaining the configuration of the brake hydraulic circuits 52, 53 below, for convenience, the master cylinder 44 side will be described as the upstream side and the wheel cylinders 8fl, 8fr, 8rl, 8rr side will be described as the downstream side based on the flow from the master cylinder 44 to the wheel cylinders 8fl, 8fr, 8rl, 8rr side of the brake caliper.

[0034] The master cylinder 44 is provided with first and second supply / discharge ports 44a, 44b, and the upstream of a first fluid passage L1 constituting each of the hydraulic circuits 52, 53 is connected to each of the supply / discharge ports 44a, 44b. The downstream of the first fluid passage L1 is connected to the middle of a second fluid passage L2. The upstream side of the second fluid passage L2 is connected to a low-pressure accumulator 54 serving as a pressure accumulation means.

[0035] The downstream side of the second fluid path L2 is branched and connected to a third fluid path L3 and a fourth fluid path L4. Furthermore, the downstream side of each of the fluid paths L3 and L4 is connected to wheel cylinders 8fl and 8rr (8fr and 8rl) that operate brake calipers provided on the wheels 5fl and 5rr (5fr and 5rl) to generate braking force (friction braking force) on the wheels 5fl and 5rr (5fr and 5rl).

[0036] Meanwhile, the upstream of the fifth and sixth fluid paths L5 and L6 are connected to the middle of the third and fourth fluid paths L3 and L4. The downstream of these fifth and sixth fluid paths L5 and L6 is connected to a seventh fluid path, and the downstream of this seventh fluid path L7 is connected to the low-pressure accumulator 54.

[0037] A gate-in valve 55 is provided in the first hydraulic line L1, and a hydraulic pump 56 is provided in the second hydraulic line L2 downstream of the first hydraulic line L1. The hydraulic pumps 56 of the first and second hydraulic circuits 52, 53 are connected to a common electric motor 57.

[0038] The drive shaft of each hydraulic pump 56, 56 is connected to a motor 57 so that the hydraulic pressure pulsations generated by each hydraulic pump 56, 56 are in opposite phase to each other. The motor 57 is driven and controlled based on a control signal (brake hydraulic pressure command value) input from the BCU 14. In this case, the motor 57 is basically driven at high speed when braking from high speed driving requiring a large braking force (brake hydraulic pressure), and is driven at low speed when braking from low speed driving requiring not so large braking force (brake hydraulic pressure).

[0039] In addition, the first fluid line L1 on the upstream side of the gate-in valve 55 and the second fluid line L2 on the downstream side of the hydraulic pump 56 are bypass-connected via an eighth fluid line L8, and a bypass valve 58 is provided in the eighth fluid line L8. Furthermore, a first brake fluid detection sensor 59a (a second brake fluid detection sensor 59b) is provided downstream of the eighth fluid line L8 in the second fluid line L2. The brake fluid detection sensor 59a (59b) is, for example, a fluid pressure sensor that detects the hydraulic pressure of the brake fluid acting on the second fluid line L2. Furthermore, pressure-increasing valves 60 and 61 are provided in the third and fourth fluid lines L3 and L4, and pressure-reducing valves 62 and 63 are provided in the fifth and sixth fluid lines L5 and L6.

[0040] Each of these valves 55, 58, 60 to 63 is, for example, an electromagnetic solenoid valve, and is switched in accordance with a drive signal from the BCU 14. For example, the bypass valve 58 and the pressurizing valves 60 and 61 are configured as normally open electromagnetic solenoid valves, and the gate-in valve 55 and the decompressing valves 62 and 63 are configured as normally closed electromagnetic solenoid valves.

[0041] For the brake actuator 6, the BCU 14 performs various braking controls through control of the electric motor 57 and the valves 55, 58, 60 to 63, and the like.

[0042] That is, the BCU 14 basically stops the electric motor 57, closes the gate-in valve 55, and opens the bypass valve 58. As a result, the brake fluid pressure generated in the master cylinder 44 in accordance with the amount of depression of the brake pedal 16a by the driver is supplied directly to each wheel cylinder 8.

[0043] Also, for example, in the vehicle 1 equipped with a driving assistance device (not shown), when a target deceleration for automatic brake control or the like is set by the driving assistance device, the BCU 14 drives the electric motor 57. Furthermore, the BCU 14 opens the gate-in valve 55 and closes the bypass valve 58. As a result, the pressure medium pressurized in the master cylinder 44 or the pressure medium supplied directly from the reservoir tank 45 is pressurized to a predetermined brake hydraulic pressure via the hydraulic pump 56, and then supplied from the second hydraulic path L2 to the third and fourth hydraulic paths L3 and L4.

[0044] Furthermore, the BCU 14 drives and controls the pressurizing valves 60, 61 and the depressurizing valves 62, 63 as necessary, and performs distribution control and depressurization control of the brake fluid pressure supplied to each wheel cylinder 8. This realizes ABS (Anti-lock Brake System) control, anti-skid control, etc.

[0045] (Distribution of braking torque) In this embodiment, by appropriately setting the friction brake ratio, it is possible to secure a relatively large regenerative power while reliably preventing rust. The friction coefficient between the brake pads and the rotor is affected by rust that occurs on the brake rotor. Therefore, the occurrence state of rust can be estimated from the friction coefficient between the brake pads and the rotor. Then, the HEV_CU10 sets the friction brake ratio based on the friction coefficient between the brake pads and the rotor.

[0046] However, when the vehicle speed decreases and falls below a certain speed, the braking force by the regenerative brake drops significantly. At vehicle speeds below this speed (hereinafter referred to as the regenerative limit speed (e.g., about 10 to 15 km / h)) at which the braking force by the regenerative brake drops significantly, it is necessary to obtain braking force by switching from the regenerative brake to the friction brake. It is also possible to brake the vehicle to a stop using the motor without using the friction brake, but in vehicles that employ such braking, it is necessary to energize the motor to generate a torque on the braking side in order to stop the vehicle, which increases power consumption and fuel consumption.

[0047] Before estimating the friction coefficient between the brake pads and the rotor (hereinafter simply referred to as the friction coefficient), the HEV_CU10, acting as a rust removal control means, determines whether or not to perform rust removal control based on the difference between the target deceleration and the actual deceleration (hereinafter referred to as the deceleration deviation amount) obtained when switching from braking using a combination of regenerative braking and friction braking to braking using the friction brakes.

[0048] If the deceleration deviation amount is smaller than a predetermined threshold, the HEV_CU10 determines that rust removal is not necessary and does not change the friction brake ratio from the start of deceleration to switching. On the other hand, if the deceleration deviation amount is equal to or greater than the predetermined threshold, the HEV_CU10 determines that rust removal may be necessary. Note that the HEV_CU10 may set the predetermined threshold based on whether or not the driver feels uneasy or uncomfortable, and may also set different thresholds for when the deceleration increases and when it decreases.

[0049] In this embodiment, when the HEV_CU10 determines that rust removal may be necessary based on the deceleration deviation amount, it obtains the friction coefficient between the brake pad and the rotor to determine the presence or absence of rust. For example, the HEV_CU10 calculates the friction coefficient after re-sizing. After re-sizing, the friction brake ratio becomes 100%, and the friction coefficient can be relatively easily estimated from the deceleration caused by the friction brake, that is, the relationship between the brake fluid pressure and the deceleration. The HEV_CU10 may estimate the friction coefficient using the difference between the actual deceleration at the time of re-sizing and the actual deceleration after re-sizing. Also, the HEV_CU10 may estimate the friction coefficient by obtaining the change in deceleration caused by the friction brake before re-sizing based on the torque distribution.

[0050] Furthermore, in this embodiment, the temperature of the brake pads is estimated to improve the accuracy of estimating the friction coefficient. The friction coefficient between the brake pads and the rotor is affected by temperature. The friction coefficient calculated based on the deceleration caused by friction braking is calculated based on a predetermined temperature. In this embodiment, an accurate friction coefficient is calculated by estimating the actual temperature of the brake pads. That is, in this embodiment, the HEV_CU10, which serves as a rust determination means, corrects the friction coefficient calculated based on the deceleration caused by friction braking with the estimated result of the brake pad temperature, and determines the presence or absence of rust based on the corrected friction coefficient obtained as a result of the correction.

[0051] FIG. 3 is a chart for explaining an example of a method for estimating the temperature of the brake pad.

[0052] In the example of FIG. 3, HEV_CU10 estimates the temperature from (i) to (vii) and estimates the brake pad temperature by subtracting the sum of the estimated values ​​of (v) to (vii) from the sum of the estimated values ​​of (i) to (iv).

[0053] That is, (i) the temperature of the brake pad is estimated by measuring the outside air temperature using a temperature sensor (not shown) and using the experimentally obtained change characteristic of the pad temperature due to the change in the ambient temperature. (ii) the braking force due to the friction brake is detected and the temperature of the brake pad is estimated based on the relationship between the energy change at the initial speed, deceleration, final speed, etc. and the pad temperature rise characteristic. (iii) the increase in the outside air temperature is measured and the temperature of the brake pad is estimated by using the experimentally obtained change characteristic of the pad temperature due to the change in the ambient temperature. (iv) the brake drag resistance x driving time is calculated and the temperature increase of the brake pad due to the brake drag is estimated. Note that the brake drag can be calculated from the deceleration during meandering driving with the accelerator off. (v) the decrease in the outside air temperature is measured and using the experimentally obtained change characteristic of the pad temperature due to the change in the ambient temperature. (vi) the temperature of the brake pad is estimated by the product of the cooling coefficient experimentally calculated by the acceleration and speed and the driving time (cooling coefficient x driving time) during driving without braking (including braking only with regeneration). (vii) The brake pad temperature is estimated by multiplying the cooling coefficient when the vehicle is stopped by the driving time.

[0054] The HEV_CU10 corrects the friction coefficient of the brake pad, which is calculated based on the deceleration caused by the friction brake, using the estimated brake pad temperature. The HEV_CU10 uses the corrected friction coefficient to determine whether or not there is rust. For example, the HEV_CU10 determines whether or not the corrected friction coefficient is within an expected range (predetermined threshold range) that takes into account variations, and determines that there is no rust if the value is within the predetermined threshold range, and determines that there is a possibility that there is rust if the value exceeds the predetermined threshold range.

[0055] For example, a characteristic map of pad temperature-friction coefficient may be prepared by experimentally determining the relationship between pad temperature and friction coefficient, and HEV_CU10 may determine whether the corrected friction coefficient exceeds a predetermined threshold range by comparing the characteristic map with the corrected friction coefficient.

[0056] Furthermore, in this embodiment, even if the HEV_CU10 as a validity determining means determines that rust exists because the corrected friction coefficient using the brake pad temperature is a value that exceeds a predetermined threshold range, the validity of the determination is further evaluated to improve the accuracy of the determination of the presence or absence of rust. This prevents a reduction in regenerative power caused by unnecessary execution of control to increase the friction brake ratio for rust removal.

[0057] That is, in this embodiment, the HEV_CU10 detects sounds and vibrations generated near each of the wheel cylinders 8fl, 8fr, 8rl, and 8rr using the output of each sensor 9, and judges the validity of the judgment of the presence or absence of rust based on the detection result. For example, when rust occurs on the brake pads, it is considered that vibrations and scraping sounds different from those generated in a normal state without rust are generated during friction braking. Therefore, the characteristics of the vibrations and scraping sounds when rust occurs, such as the frequency of the scraping sounds, the vibration magnitude, or the vibration frequency, are experimentally obtained. The HEV_CU10 may judge the validity of the judgment of the presence or absence of rust by comparing the characteristics of the vibrations and scraping sounds acquired by each sensor 9 after the replacement with the characteristics when rust occurs. In addition, the HEV_CU10 may judge the validity of the judgment of the presence or absence of rust using the output of various sensors other than each sensor 9, such as an acceleration pickup (not shown) that detects vibrations generated in a judder connected to the brake pedal. If the degree of coincidence, which indicates the degree of similarity between the characteristics of vibration and scraping sounds acquired by each sensor 9 and the characteristics when rust has occurred, is equal to or greater than a predetermined threshold, HEV_CU10 determines that the determination of the presence of rust is valid, and if the degree of coincidence is less than the predetermined threshold, it may determine that the determination of the presence of rust is invalid and that no rust has occurred.

[0058] The HEV_CU10 as a rust removal control means sets the friction brake ratio before switching based on the result of the rust presence / absence determination. That is, the HEV_CU10 sets the friction brake ratio at the time of the next braking to be larger than the friction brake ratio of the initial setting of the braking torque distribution calculated from the target deceleration based on the result of the rust presence determination.

[0059] (action) Next, the operation of the embodiment configured as above will be described with reference to Fig. 4 to Fig. 6. Fig. 4 is a flow chart showing the control during deceleration, Fig. 5 is a flow chart showing the braking torque distribution control taking into account the presence or absence of rust, and Fig. 6 is an explanatory diagram showing the braking torque distribution control taking into account the presence or absence of rust.

[0060] In step S1 of Fig. 4, the HEV_CU10 checks whether or not a deceleration request has been made. That is, for example, when the HEV_CU10 detects that the accelerator pedal 15a is released based on a signal from the accelerator sensor 15, the HEV_CU10 determines that a deceleration request due to coasting has been made. Alternatively, for example, when the HEV_CU10 detects that the brake pedal 16a is depressed based on a signal from the brake sensor 16, the HEV_CU10 determines that a deceleration request has been made. Alternatively, for example, when the HEV_CU10 receives a target deceleration from a driving support device (not shown), the HEV_CU10 determines that a deceleration request has been made.

[0061] Then, in step S1, if it is determined that there is no deceleration request, the HEV_CU 10 exits the routine.

[0062] On the other hand, when the process proceeds from step S1 to step S2, the HEV_CU10 acquires a target deceleration. That is, for example, during coasting, the HEV_CU10 calculates a target deceleration based on a signal (accelerator opening degree, etc.) from the accelerator sensor 15, the vehicle speed, etc. Also, for example, when the HEV_CU10 detects depression of the brake pedal by the driver based on a signal from the brake sensor 16, the HEV_CU10 calculates a target deceleration based on signals from the first and second brake fluid pressure sensors 59a, 59b, etc. Furthermore, in the vehicle 1 equipped with a driving support device (not shown), the target deceleration for automatic brake control, etc., calculated by the driving support device is acquired.

[0063] In the next step S3, the HEV_CU10 calculates the necessary braking torque based on the current target deceleration. Then, the HEV_CU10 calculates each braking torque distribution value for distributing the calculated necessary braking torque to the regenerative brake, the engine brake, and the friction brake according to the running state of the host vehicle 1, etc. The upper part of FIG. 6 shows the braking torque distribution of the regenerative braking torque (white part) and the friction braking torque (shaded part) in this case before the switching in the initial setting. In the example of FIG. 6, the ratio of the regenerative braking torque to the friction braking torque is about 4:1, and the ratio of the regenerative braking torque is sufficiently large, and a relatively large regenerative power can be obtained. In this embodiment, the HEV_CU10 changes the friction brake ratio and the friction braking torque after the switching according to the flow of FIG. 5 described later.

[0064] In the next step S4, the HEV_CU 10 outputs the calculated braking torque distribution value to the corresponding control unit as control information.

[0065] That is, for example, when a braking torque distribution value for a regenerative brake is calculated, the HEV_CU 10 outputs the braking torque distribution value as control information to the PCU 13. As a result, magnetic field control for regenerative power generation in the motor generator 4 is performed, and a regenerative braking force according to the braking torque distribution value is generated.

[0066] Furthermore, for example, when a braking torque distribution value for engine braking is calculated, the HEV_CU 10 outputs the braking torque distribution value as control information to the ECU 11 and the TCU 12. As a result, the output torque of the engine 2 and the gear ratio of the automatic transmission 3 are controlled, and an engine braking force according to the braking torque distribution value is generated.

[0067] Furthermore, for example, when a braking torque distribution value for a friction brake is calculated, the HEV_CU 10 outputs the braking torque distribution value as control information to the BCU 14. This causes brake fluid pressure control in the brake actuator 6 to generate a friction brake force according to the braking torque distribution value.

[0068] In the next step S5, the HEV_CU 10 judges whether the regeneration limit speed has been reached, and if not, the routine ends. If the regeneration limit speed has been reached, the HEV_CU 10 switches from the combined use of the regeneration brake and the friction brake to the use of the friction brake (step S6).

[0069] The upper part of Fig. 6 shows the braking torque distribution of the regenerative braking torque (white part) and the friction braking torque (shaded part) in this case after the switching in the initial setting. As shown in Fig. 6, after the switching, the ratio of the friction braking torque becomes 100%, and the braking force by the friction brake is used until the vehicle 1 stops.

[0070] After this re-allocation, the HEV_CU10 determines whether or not to change the friction brake ratio and the friction braking torque after the re-allocation, according to the flow in Fig. 5. In step S11 in Fig. 5, the HEV_CU10 determines whether or not the re-allocation has been performed. When the re-allocation has been performed, the HEV_CU10 calculates a deceleration deviation amount in the next step S12. For example, the HEV_CU10 calculates the difference between the target deceleration and the actual deceleration as the deceleration deviation amount.

[0071] In step S13, the HEV_CU10 judges whether the deceleration deviation is equal to or greater than a threshold value. If the deceleration deviation is smaller than a predetermined threshold value, the HEV_CU10 judges that rust removal from the brake rotor is not necessary, and returns the process to step S11. That is, in this case, the friction brake torque and friction brake ratio after switching are not changed. Therefore, the next time deceleration is performed from a speed higher than the regeneration limit speed, braking torque distribution is performed based on the target deceleration without considering rust (step S3 in FIG. 4). In this case, braking is performed with the same braking torque distribution as the initial setting in the upper part of FIG. 6.

[0072] On the other hand, if the deceleration deviation amount is equal to or greater than the predetermined threshold value (YES in step S13), the HEV_CU10 determines that rust removal may be necessary, and calculates the friction coefficient between the pad and the rotor, taking temperature into consideration. That is, in the next step S14, the HEV_CU10 calculates the friction coefficient between the pad and the rotor based on the brake fluid pressure and the deceleration, and estimates the pad temperature in step S15. The HEV_CU10 corrects the friction coefficient calculated from the deceleration caused by friction braking based on the estimated pad temperature (step S16). In this way, the accuracy of calculating the friction coefficient between the pad and the rotor is improved, and the accuracy of determining the state of rust based on the friction coefficient is also improved.

[0073] In step S17, the HEV_CU10 judges the presence or absence of rust by comparing the friction coefficient between the pad and rotor (corrected friction coefficient) corrected by the estimated actual temperature with an expected range including variation (predetermined threshold range). For example, the HEV_CU10 may use a characteristic map of pad temperature characteristics-friction coefficient, and judge that no rust has occurred if the difference between the friction coefficient obtained from the characteristics of the map and the corrected friction coefficient is equal to or less than a predetermined threshold (i.e., within the expected range), and may judge that rust has occurred if the difference is greater than the predetermined threshold (i.e., outside the expected range).

[0074] If the corrected friction coefficient is within the threshold range, the HEV_CU10 determines that rust has not occurred, and shifts the process from step S17 to step S18. That is, in this case, since there is no rust, it is not necessary to increase the friction brake ratio to remove the rust, but since the deceleration deviation amount is relatively large, the HEV_CU10 changes the friction braking torque after switching to reduce the deceleration deviation amount (step S18). Therefore, the next time deceleration is performed from a speed higher than the regeneration limit speed, the friction braking torque after switching is changed.

[0075] In this case, as shown in the middle part of Fig. 6 before switching without rust, there is no need to remove rust before switching, so braking is performed with the same braking torque distribution as in the initial setting. This allows sufficient regenerative power to be obtained. After switching, the friction braking torque is increased (shaded area) to reduce the amount of deceleration deviation from the previous braking. Note that while Fig. 6 shows an example in which the friction braking torque is increased, there are also cases in which the friction braking torque is decreased.

[0076] On the other hand, when it is determined in step S17 of Fig. 5 that the corrected friction coefficient exceeds the threshold range (YES determination), the HEV_CU10 determines the validity of the determination result that rust is present. That is, in step S21, the HEV_CU10 obtains the detection results of vibration and rubbing noise from each sensor 9, and obtains a degree of agreement indicating the degree of similarity between the characteristics of the vibration and rubbing noise and the characteristics when rust is present. The HEV_CU10 determines whether the obtained degree of agreement is equal to or greater than a predetermined threshold (step S22).

[0077] If the degree of coincidence is smaller than a predetermined threshold, the HEV_CU10 determines that the rust determination based on the value of the corrected friction coefficient is invalid, and proceeds to step S18. That is, in this case, the friction braking torque after the replacement is changed to reduce the deceleration deviation amount. Note that, before the replacement, the same torque distribution as the initial setting shown in the middle of FIG. 6 for the case without rust is adopted.

[0078] On the other hand, if the degree of agreement is equal to or greater than the predetermined threshold, the HEV_CU10 determines that the rust determination based on the value of the corrected friction coefficient is valid, and proceeds to step S23. In step S23, the HEV_CU10 performs a setting to increase the friction brake ratio. Therefore, the next time the vehicle is decelerated from a speed higher than the regeneration limit speed, the braking torque distribution is performed with the ratio of friction braking torque increased, taking into account the rust state (step S3 in FIG. 4). In this case, the braking torque is also set in consideration of the deceleration deviation amount.

[0079] The lower part of Fig. 6 shows the braking torque distribution before switching with rust in this case, which is regenerative braking torque (white part) and friction braking torque (shaded part). Before switching, the friction brake ratio is relatively large, and in the example of Fig. 6, the ratio of regenerative braking torque to friction braking torque is approximately 1:1. By increasing the friction brake ratio, effective rust removal is performed by the braking force of the friction brake in the relatively high vehicle speed range up to the regenerative limit speed. After switching, the friction braking torque is increased (hatched part) to reduce the deceleration deviation.

[0080] In addition, if, as a result of increasing the friction brake ratio, the judgment in step S13, S17 or S22 is that rust removal is not necessary, or that the judgment that there is no rust or that there is rust is inappropriate, the braking torque distribution will be returned to the initial setting at the time of the next deceleration.

[0081] In this embodiment, when the deceleration deviation is smaller than the threshold value, the friction braking torque is not increased. The friction coefficient between the brake pad and the rotor, which is calculated by estimating the actual temperature, is corrected, and the presence or absence of rust is judged based on this corrected friction coefficient, and the validity of the result of the rust judgment is judged based on vibration and scraping noise. This improves the accuracy of the rust judgment, and enables the control to increase the friction braking torque to remove rust when necessary. In this way, rust can be prevented and reliable braking can be achieved while securing a relatively large regenerative power.

[0082] In the above-described embodiment, the HEV_CU10, ECU11, TCU12, PCU13, and BCU14 are configured with a well-known microcomputer equipped with a CPU, RAM, ROM, non-volatile storage unit, and peripheral devices thereof, and the ROM stores programs to be executed by the CPU and fixed data such as data tables in advance. Note that all or part of the functions of the processor may be configured with a logic circuit or an analog circuit, and the processing of various programs may be realized by an electronic circuit such as an FPGA.

[0083] The invention described in the above embodiment is not limited to those embodiments, and various modifications can be made in the implementation stage without departing from the gist of the invention.

[0084] For example, if some of the constituent elements shown in each form are deleted, and the stated problem can be solved and the stated effect can be obtained, the configuration from which these constituent elements are deleted can be extracted as an invention. [Explanation of symbols]

[0085] 1 … Vehicle (own vehicle) 2 … Engine 3. Automatic transmission 4 … Motor generator 5(5fl,5fr,5rl,5rr) … Wheels 6 … Brake actuator 7 … Battery 8 (8fl, 8fr, 8rl, 8rr) ... Wheel cylinder 9 (9fl, 9fr, 9rl, 9rr) ... Sensor 10 … Hybrid control unit (HEV_CU) 11 … Engine control unit (ECU) 12 … Transmission control unit (TCU) 13 ... Power Control Oil Niche (PCU) 13a … Inverter 14 … Brake control unit (BCU) 15 ... Accelerator sensor 15a ... accelerator pedal 16 ... Brake sensor 16a ... Brake pedal 17 (17fl, 17fr, 17rl, 17rr) ... Wheel speed sensor 18 ... Front and rear acceleration sensor 19 ... Temperature sensor 41 ... Brake fluid pressure generating section 42 ... Brake hydraulic circuit 44 ... Master cylinder 44a, 44b … Supply and exhaust ports 45 ... Reservoir tank 46 ... Brake booster 48 ... Operating rod 52,53 … Brake hydraulic circuit 54 ... Low pressure accumulator 55 … Gate-in valve 56 ... Hydraulic pump 57 … Electric motor 58 … Bypass valve 59a, 59b ... Brake fluid pressure sensor 60,61 … Pressure valve 62,63 … Pressure reducing valve

Claims

1. A braking control device for a vehicle having a motor generator as a drive source of a power unit, a braking force control means for controlling a braking force by coordinating a regenerative brake using the motor generator and a friction brake using a friction engagement element to distribute a regenerative braking torque by the regenerative brake and a friction braking torque by the friction brake at a predetermined braking torque distribution, and for setting different braking torque distributions before and after the speed of the vehicle reaches a regenerative limit speed during deceleration; a rust determining means for determining a rust state of the friction engagement element by estimating a friction coefficient of the friction engagement element; a validity determining means for determining the validity of a result of the determination of the state of rust by the rust determining means based on at least one of a detection result of vibration of the frictional engagement element and a sound emitted from the frictional engagement element; A vehicle braking control device characterized by comprising: a rust removal control means that sets the braking torque distribution during deceleration until the vehicle speed reaches the regenerative limit speed based on the judgment result of the validity judgment means.

2. The vehicle braking control device described in claim 1, characterized in that the rust removal control means determines the need for rust removal based on a deceleration deviation amount, which is the difference between a target deceleration and an actual deceleration, and changes the setting of the braking torque distribution if necessary based on the judgment result of the validity judgment means.

3. The rust determination means includes: a friction estimation means for estimating a friction coefficient of the friction engagement element based on a deceleration of the vehicle at a speed equal to or lower than the regeneration limit speed; a temperature estimating means for estimating a temperature of the friction engagement element; a correction means for correcting the friction coefficient estimated by the friction estimation means based on the temperature estimated by the temperature estimation means, 2. The vehicle brake control device according to claim 1, wherein the state of rust in the friction engagement elements is determined based on the magnitude of the corrected friction coefficient corrected by the correcting means.

4. The vehicle braking control device described in claim 1, characterized in that when the validity determination means determines that the rust presence determination result by the rust determination means is invalid, the rust removal control means changes the friction braking torque during the period after the vehicle speed reaches the regenerative limit speed during deceleration in accordance with a deceleration deviation amount, which is the difference between a target deceleration and an actual deceleration.

5. The vehicle braking control device described in claim 1, characterized in that when the validity determination means determines that the rust presence determination result by the rust determination means is valid, the rust removal control means increases the distribution of the friction braking torque during deceleration until the vehicle speed reaches the regenerative limit speed.

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