JP2020061883A - Vehicle brake control device - Google Patents

Abstract

To provide a brake control device which can reduce torque fluctuation of a drive shaft during regeneration.SOLUTION: A brake control device includes: a hydraulic brake device which can apply friction brake force on a wheel, an electric motor which generates drive force for rotating a driving wheel through a drive shaft when power is applied, and generates regeneration brake force when rotating by receiving rotation force of the driving wheel through the drive shaft; and control means which controls the hydraulic brake device and the electric motor and makes the hydraulic brake device execute antiskid control when a predetermined condition is established. The control means continues making the electric motor generate the regeneration brake force from a time when the predetermined condition is established until a predetermined time passes when the regeneration brake force is applied on the driving wheel and the predetermined condition is established, and makes the electric motor eliminate the regeneration brake force after the predetermined time passes from the time when the predetermined condition is established.SELECTED DRAWING: Figure 2

Description

  The hybrid vehicle includes an internal combustion engine and an electric motor as a drive source of driving force for driving the vehicle. The internal combustion engine and the electric motor are connected to the drive wheels via a power transmission mechanism and a drive shaft.

  Generally, a hybrid vehicle includes a friction braking device that can apply a friction braking force to each wheel. Further, the electric motor of the hybrid vehicle applies regenerative braking force to the drive wheels while generating power when the rotational force of the drive wheels is transmitted via the power transmission mechanism and the drive shaft. That is, generally, the hybrid vehicle can apply the friction braking force and the regenerative braking force to the drive wheels while selecting the braking force.

  By the way, the friction braking device of the hybrid vehicle can be configured to be capable of executing so-called anti-skid control (hereinafter referred to as ABS control). As is well known, the ABS control is an operation of supplying the friction braking device so that the slip ratio becomes a target slip ratio that is a slip ratio within a predetermined range when the slip ratio of a wheel becomes larger than a predetermined ABS determination threshold value. This is a control for increasing or decreasing the oil pressure of oil.

  Generally, in a hybrid vehicle, when the driver depresses the brake pedal (when the depression amount is less than or equal to a predetermined amount), the operation of the friction braking device is prioritized, and the regenerative braking force is generated in the electric motor. Then, when the slip ratio of the wheels becomes larger than the ABS determination threshold value while the electric motor is generating the regenerative braking force, the electric motor causes the regenerative braking force to disappear and the friction braking device starts the ABS control.

  Here, it is assumed that the hybrid vehicle is traveling on a road having a downward slope shown in FIG. Areas A and C, which are large areas of the road surface of this road, are made of asphalt. However, the narrow area B located between the areas A and C is made of an iron plate extending in the width direction of the road. The dimension of the iron plate in the vehicle traveling direction is short (for example, 50 cm).

  Here, it is assumed that the vehicle travels in the arrow direction X in FIG. When the vehicle travels in the areas A and C constituted by asphalt, the friction coefficient between the driving wheels (tires) of the vehicle and the road surface becomes μH. On the other hand, when the vehicle travels in a region B formed of an iron plate and located between the regions A and C, the friction coefficient between the drive wheels and the road surface is μL, which is smaller than μH. As shown in (a) of FIG. 7, μH and μL change stepwise (stepwise).

  It is assumed that the driver depresses the brake pedal while the vehicle is traveling in the area A and the electric motor generates regenerative braking force. In this case, it is assumed that this state is maintained (the magnitude of the regenerative braking force is substantially constant) and the ABS control is not executed while the vehicle travels in the areas B and C. At this time, a regenerative braking force of a certain magnitude is applied from the electric motor to the drive wheels while the vehicle travels in the areas A to C. That is, as shown by the solid line in (d) of FIG. 7, when the regenerative torque generated in the drive shaft due to the regenerative braking force is DC torque Tdc (DC torque), the vehicle travels in the regions A to C. Moreover, the DC torque Tdc has a substantially constant value. Here, the torque that increases the rotational speed of the drive shaft (that is, the torque that accelerates the vehicle in the traveling direction) is referred to as "positive torque", and the torque that decreases the rotational speed of the drive shaft (that is, the vehicle). The torque for decelerating) is called "negative torque". The DC torque Tdc is a negative torque.

  As shown in FIG. 7B, when the vehicle moves from the area A to the area B at time t1, the magnitude of the input given from the road surface to the drive wheels (tires) decreases in a step-like manner. Further, when the vehicle moves from region B to region C at time t2, the magnitude of this input increases in a stepwise manner.

  Then, the angular velocity ωdw of the drive wheel and the angular velocity ωm of the electric motor change as shown in (c) of FIG. 7. That is, since the angular velocity ωdw and the angular velocity ωm are equal to each other when the vehicle travels in the region A, the twist amount of the drive shaft due to the rotational movement of the drive wheel and the electric motor (difference between the angular velocity ωdw and the angular velocity ωm) is almost the same. It is zero. That is, before the time t1, as shown in FIG. 7D, the AC torque Tac (AC torque) due to the rotational movement of the drive wheel and the electric motor is hardly generated on the drive shaft (that is, AC). The torque Tac is almost zero).

  However, when the vehicle enters the area B from the area A at time t1, the angular velocity ωm gradually decreases due to the inertial force acting on the electric motor. On the other hand, the friction coefficient sharply decreases from μH to μL, and the angular velocity ωdw sharply decreases due to friction braking at this time, so that the angular velocity ωdw becomes smaller than the angular velocity ωm. As a result, the drive shaft is twisted in the positive torque direction. Then, while the vehicle travels in the region B, the angular velocity ωdw and the angular velocity ωm become equal to each other at the time t1a. Further, since the angular velocity ωm further decreases due to the regenerative torque generated by the electric motor and the twist of the drive shaft thereafter, the angular velocity ωdw becomes larger than the angular velocity ωm.

  Therefore, as shown in FIG. 7D, the AC torque Tac that is a positive torque is generated on the drive shaft between the time t1 and the time t1a, and the AC torque Tac gradually increases with the passage of time. To do. Then, at time t1a, the angular velocity ωdw and the angular velocity ωm become equal, the torsion of the drive shaft becomes maximum, and the AC torque Tac becomes the maximum value Tacmax1. Further, after time t1a, the magnitude of the angular velocities (ωdw, ωm) is reversed, so that the twist of the drive shaft is eliminated, and the AC torque Tac gradually decreases.

  Then, when the vehicle enters the region C, the friction coefficient increases from μL to μH, so that the angular velocity ωdw rapidly increases. As a result, the angular velocity ωdw becomes larger than the angular velocity ωm. This increases the twist in the negative torque direction. Therefore, as shown in (d) of FIG. 7, the value (absolute value) of the negative torque increases, so that the AC torque Tac further decreases. Then, at the time t3, the value of the AC torque Tac becomes the minimum value Tacmin1.

  By the way, when the value of the total torque generated in the drive shaft due to the rotational movement of the drive wheels and the electric motor and the regenerative torque is Td, the total torque Td = DC torque Tdc + AC torque Tac. Therefore, as shown in (e) of FIG. 7, when the horizontal axis represents time and the vertical axis represents the magnitude of the total torque Td, the shape of the graph representing the total torque Td is that of the DC torque Tdc. It has a shape obtained by adding the graph of the AC torque Tac. The total torque Td has a maximum value Tacmax2 at time t1a and a minimum value Tacmin2 at time t3.

JP 2001-268704 A

  Here, it is assumed that the slip ratio becomes larger than the ABS determination threshold value when the vehicle enters the area A from the area A, and the friction braking device starts the ABS control at the time t1. In this case, the electric motor interrupts the regenerative operation at time t1 to eliminate the regenerative braking force. In this case, when the vehicle enters the area C from the area B, the slip ratio becomes equal to or less than the ABS determination threshold value, and the friction braking device stops the ABS control and the electric motor restarts the regenerative operation, for example, at a predetermined time after the time t3. . Then, as shown in (d) of FIG. 7, the DC torque Tdc changes from a negative value to a magnitude indicated by a two-dot chain line between the time t1 and the predetermined time (after a predetermined time has elapsed from the time t1. (Because it becomes zero), the total torque Td becomes the magnitude shown by the chain double-dashed line as shown in FIG. That is, the maximum value of the total torque Td changes to the maximum value Tacmax2 'which is larger than Tacmax2 and the minimum value changes to the minimum value Tacmin2' which is larger than Tacmin2.

  Therefore, if the difference between the maximum value Tacmax2 and the minimum value Tacmin2 is D1 and the difference between the maximum value Tacmax2 'and the minimum value Tacmin2' is D2, the difference D2 becomes substantially the same as the difference D1. Therefore, when the difference D1 is large, the difference D2 also becomes large.

  The total torque Td generated in the drive shaft is transmitted to the internal combustion engine via the power transmission mechanism. Therefore, when the difference D2 is large, the internal combustion engine may vibrate greatly due to the force resulting from the total torque Td, and a large abnormal noise may be generated.

  Further, for example, when the electric motor restarts the regenerative operation at time t2a in FIG. 7 (that is, when the DC torque Tdc becomes zero between the time t1 and the time t2a), the DC torque Tdc is as shown by the alternate long and short dash line. Changes to. Therefore, the magnitude of the total torque Td after the time t2a becomes the magnitude indicated by the alternate long and short dash line. That is, the minimum value of the total torque Td is Tacmin2 ″ which is larger than Tacmin2 and smaller than Tacmin2 ′. That is, in this case, when the difference between the maximum value Tacmax2 'and the minimum value Tacmin2' 'is D2A, the difference D2A is larger than the difference D1 (D2). That is, in this case, the internal torque of the internal combustion engine is greatly vibrated by the force resulting from the total torque Td, and a large noise is generated.

  The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is when the friction coefficient between the road surface on which the vehicle is traveling and the drive wheels changes stepwise, and when the vehicle enters from a road surface having a high friction coefficient to a road surface having a low friction coefficient. Another object of the present invention is to provide a vehicle braking control device capable of reducing the difference between the maximum value and the minimum value of the torque generated in the drive shaft when the regenerative operation by the electric motor is interrupted.

The vehicle braking control device of the present invention,
A hydraulic braking device (25) capable of exerting frictional braking force on wheels,
When electric power is supplied, a drive force for rotating the drive wheels (11FL, 11FR) is generated via the drive shafts (12FL, 12FR) and is rotated by receiving the rotational force of the drive wheels via the drive shaft. An electric motor (16) that generates regenerative braking force when
Control means (22) for controlling the hydraulic braking device and the electric motor and for causing the hydraulic braking device to perform anti-skid control when a predetermined condition is satisfied;
Equipped with
The control means,
When the predetermined condition is satisfied when the regenerative braking force is applied to the drive wheels, the electric motor is caused to generate the regenerative braking force until a predetermined time (T) elapses from the time when the predetermined condition is satisfied. The electric motor is configured to cause the regenerative braking force to disappear when the predetermined time elapses from the time when the predetermined condition is satisfied.

  According to the present invention, the anti-skid control is executed when the predetermined condition is satisfied while the regenerative braking force is applied to the drive wheels. Further, the electric motor continues to generate the regenerative braking force (regenerative torque) until a predetermined time elapses from the time when the predetermined condition is satisfied. Then, when a predetermined time elapses from the time when the predetermined condition is satisfied, the electric motor causes the regenerative braking force to disappear. Therefore, the difference between the maximum value and the minimum value of the torque generated in the drive shaft becomes smaller than in the case where the electric motor immediately loses the regenerative braking force (regenerative torque) at the time when the predetermined condition is satisfied.

  In the above description, in order to facilitate understanding of the present invention, the names and / or reference numerals used in the embodiments are attached in parentheses to the configurations of the invention corresponding to the embodiments described later. However, each constituent element of the present invention is not limited to the embodiment defined by the reference numerals.

1 is a schematic overall view of a vehicle including a vehicle braking control device according to an embodiment of the present invention. 6 is a graph showing the magnitudes of AC torque, DC torque, and total torque generated in the drive shaft according to the embodiment of the present invention. It is a graph which shows the transfer function of the electric power transmission system of the embodiment of the present invention. 3 is a graph showing a Laplace-transformed value of a function representing a force (step input) transmitted from the road surface to the driving wheels when the vehicle of the embodiment of the present invention moves from the area A to the area B of the road surface. 7 is a graph showing changes in AC torque when the vehicle moves from area A to area B. 3 is a flowchart showing a process executed by a vehicle control ECU. 6 is a graph showing various values when the vehicle travels in areas A to C of the road surface.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, the vehicle 10 of the present embodiment includes two front wheels 11FL and 11FR and two rear wheels 11RL and 11RR. The left and right front wheels 11FL and 11FR are connected to the outer ends of the left and right drive shafts 12FL and 12FR, respectively. Further, the left and right rear wheels 11RL and 11RR are rotatably supported by the vehicle body via suspensions (not shown).

  The inner ends of the left and right drive shafts 12FL and 12FR are connected to the differential gear 13. The output shaft of the second electric motor 16 and the power split mechanism 17 are connected to the differential gear 13 via a reduction mechanism 15. The power split mechanism 17 is a planetary gear mechanism. Further, the output shaft of the first electric motor 18 is connected to the power split mechanism 17.

  The vehicle 10 includes a storage battery 19 and a boost converter and an inverter, both of which are not shown. The storage battery 19 is a rechargeable secondary battery (for example, a lithium ion battery). The DC power output from the storage battery 19 is voltage-converted (boosted) by the boost converter. The DC power whose voltage has been converted is converted into AC power by the inverter and supplied to the second electric motor 16 and the first electric motor 18. The second electric motor 16 and the first electric motor 18 to which electric power is supplied can operate as an electric motor.

  On the other hand, when the second electric motor 16 and / or the first electric motor 18 operate as a generator, the AC power generated by these is converted into DC power by the inverter. Further, the converted DC power is subjected to voltage conversion (step down) by the step-up converter and supplied to the storage battery 19.

  Further, a crankshaft of an internal combustion engine 20 is connected to the power split mechanism 17 so that torque can be transmitted.

  The first electric motor 18 is mainly used as a generator. The first electric motor 18 cranks the internal combustion engine 20 when the internal combustion engine 20 is started. The second electric motor 16 is mainly used as an electric motor, and can generate torque for rotating the left and right front wheels 11FL and 11FR, which are drive wheels. That is, the vehicle 10 is a hybrid vehicle including the second electric motor 16 and the internal combustion engine 20 as drive sources for the left and right front wheels 11FL and 11FR that are drive wheels.

  The vehicle 10 includes a vehicle control ECU 22. Vehicle control ECU 22 includes a plurality of ECUs for controlling vehicle 10. That is, the vehicle control ECU 22 has, for example, an ECU for controlling the internal combustion engine 20, an ECU for controlling the second electric motor 16 and the first electric motor 18, and an ECU for controlling a brake actuator 25 described later. There is. The ECU is an abbreviation for an electric control unit, and is an electronic control circuit having a microcomputer including a CPU, a ROM, a RAM, an interface and the like as a main component. The CPU realizes various functions described later by executing the instructions stored in the memory (ROM). Each ECU is connected via a CAN (Controller Area Network) so that various control information and request signals can be mutually transmitted and received.

  The vehicle control ECU 22 selects the second electric motor 16 and / or the internal combustion engine 20 as a drive source, for example, based on the vehicle speed of the vehicle 10. When the electric power of the storage battery 19 is supplied to the second electric motor 16 under the control of the vehicle control ECU 22, the driving force of the second electric motor 16 is passed through the reduction mechanism 15, the differential 13 and the drive shafts 12FL, 12FR to the left and right front wheels 11FL, 11FR. Be transmitted to. Further, when the internal combustion engine 20 is operated under the control of the vehicle control ECU 22, the driving force of the internal combustion engine 20 is passed through the power split mechanism 17, the reduction mechanism 15, the differential 13 and the drive shafts 12FL, 12FR to the left and right front wheels 11FL, 11FR. Be transmitted to.

  Further, the vehicle 10 includes four wheel speed sensors 24FL, 24FR, 24RL, 24RR and a brake actuator 25. The wheel speed sensors 24FL, 24FR, 24RL, 24RR and the brake actuator 25 are connected to the vehicle control ECU 22.

  Each wheel speed sensor 24FL, 24FR, 24RL, 24RR outputs a pulse signal according to the rotation speed (wheel speed) of the corresponding wheel 11FL, 11FR, 11RL, 11RR every time a predetermined time has elapsed. The vehicle control ECU 22 detects the rotation speeds of the wheels 11FL, 11FR, 11RL, 11RR based on this pulse signal every time a predetermined time elapses. Further, the vehicle control ECU 22 calculates the average value of the rotation speeds of the wheels 11FL, 11FR, 11RL, 11RR each time a predetermined time has elapsed, and acquires this average value as the vehicle speed of the vehicle 10.

  The brake actuator 25 is a hydraulic control actuator. The brake actuator 25 is a hydraulic pressure between a master cylinder that pressurizes hydraulic oil by a pedaling force of a brake pedal (not shown) and a friction brake device including a well-known wheel cylinder provided on each wheel 11FL, 11FR, 11RL, 11RR. It is arranged in a circuit (neither is shown). The brake actuator 25 adjusts the hydraulic pressure of the hydraulic oil supplied to the wheel cylinders.

  Further, the vehicle control ECU 22 calculates the slip ratio of the vehicle 10 = (vehicle speed-wheel speed) / wheel speed based on the wheel speed and the vehicle speed each time a predetermined time has elapsed. Further, a threshold value for ABS determination is recorded in the ROM of the vehicle control ECU 22.

  The vehicle control ECU 22 and the brake actuator 25 can execute ABS control. That is, when the vehicle control ECU 22 determines that the brake pedal is stepped on the basis of information from a brake pedal sensor (not shown), it is determined whether the calculated slip ratio is larger than the ABS determination threshold value. Perform the judgment operation. Then, if it is determined to be large, the vehicle control ECU 22 controls the brake actuator 25 to adjust the hydraulic pressure of the hydraulic oil. Then, the friction braking force is adjusted for each wheel 11FL, 11FR, 11RL, 11RR corresponding to each friction brake device so that the slip ratio becomes a target slip ratio which is a slip ratio within a predetermined range. Give.

  Further, when the rotational force of the left and right front wheels 11FL, 11FR is transmitted to the second electric motor 16 via the drive shafts 12FL, 12FR, the differential 13, and the speed reduction mechanism 15 when the second electric motor 16 is not functioning as an electric motor, The two electric motor 16 operates as a generator. At this time, the braking torque (regenerative torque) generated by the second electric motor 16 is transmitted as a regenerative braking force to the left and right front wheels 11FL and 11FR via the reduction mechanism 15, the differential 13 and the drive shafts 12FL and 12FR. When the electric power generated by the second electric motor 16 can be stored in the storage battery 19, the vehicle control ECU 22 determines that the brake pedal is depressed based on the information from the brake pedal sensor and the depression amount is equal to or less than a predetermined amount. In that case, the regenerative braking force (regenerative torque) is generated in the second electric motor 16 with priority over the operation of the friction brake device, except when the ABS control is executed.

  Next, the operation of the vehicle 10 when traveling in the directions X in the directions A to C of the road shown in FIG. 7 will be described. When the vehicle 10 travels in the area A, the vehicle 10 travels only by the driving force of the second electric motor 16. Then, the brake pedal is depressed while the vehicle 10 is traveling in the area A, and the driver continues to depress the brake pedal while the vehicle 10 is traveling in the areas A to C. Then, while the vehicle 10 is traveling in the area A, the second electric motor 16 stops its operation as an electric motor and starts a regenerative operation instead.

  Here, while the vehicle 10 passes through the region B and travels in the region C, the second electric motor 16 continues to exert regenerative braking force of substantially the same magnitude as when the second electric motor 16 travels in the region A, and It is assumed that the vehicle control ECU 22 and the brake actuator 25 do not execute ABS control (ABS determination operation) in A to C. In this case, the AC torque Tac generated on the drive shafts 12FL and 12FR has substantially the same shape as the AC torque Tac shown in FIG. 7D, as shown in FIG. Further, the DC torque Tdc generated on the drive shafts 12FL and 12FR in this case is substantially equal to the DC torque Tdc shown by the solid line in FIG. 7D, as shown by the solid line in FIG. It has the same shape. That is, the shape of the total torque Td generated in the drive shafts 12FL and 12FR in this case is the DC torque Tdc shown by the solid line in (e) of FIG. 7 as shown by the solid line in (c) of FIG. The shape is substantially the same.

  Next, it is assumed that the vehicle control ECU 22 repeatedly executes the ABS determination operation at predetermined time intervals while the brake pedal is being depressed. In this case, at time t1 when the vehicle 10 enters the region B from the region A, the vehicle control ECU 22 determines that the slip ratio has become larger than the ABS determination threshold value and starts the ABS control (however, the slip ratio is the target slip). The rate is, for example, after time t2a).

  Then, the vehicle control ECU 22 causes the second electric motor 16 to continue the regenerative operation until the predetermined time T elapses from the time t1, and causes the second electric motor 16 to interrupt the regenerative operation after the predetermined time T elapses. In this case, after the lapse of the predetermined time T, the DC torque Tdc has a shape indicated by a two-dot chain line in FIG. 2B (that is, the DC torque Tdc becomes zero after a lapse of the predetermined time T). . The predetermined time T is recorded in the ROM of the vehicle control ECU 22. Further, for example, when the vehicle control ECU 22 determines that the slip ratio has become equal to or less than the ABS determination threshold value and the brake pedal is depressed at a predetermined time after the time t3, the ABS control is interrupted, and instead. The second electric motor 16 restarts the regenerative operation.

  Here, it is assumed that the time when the predetermined time T has passed is time t1a. Then, the graph shape of the total torque Td between the time t1 and the time t1a becomes the same as that when the ABS control is not executed. That is, the maximum value of the total torque Td is Tacmax2. On the other hand, the graph shape of the total torque Td between the time t1a and the time t3 is the shape shown by the chain double-dashed line. That is, the minimum value Tacmin2-a of the total torque Td generated at the time t3 becomes larger than the minimum value Tacmin2. Therefore, if the difference between the maximum value Tacmax2 and the minimum value Tacmin2 of the total torque Td is D1 and the difference between the maximum value Tacmax2 and the minimum value Tacmin2-a is D3, the difference D3 is smaller than the difference D1. Further, this difference D3 is smaller than the difference D2 in FIG. That is, when the second electric motor 16 is allowed to continue the regenerative operation until the predetermined time T elapses from the time t1, the maximum value of the total torque Td becomes larger than that when the second electric motor 16 immediately interrupts the regenerative operation at the time t1. The difference from the minimum value becomes smaller. Therefore, the possibility that the internal combustion engine 20 vibrates greatly due to the force resulting from the total torque Td and a large noise is generated is reduced.

  Even if the time when the predetermined time T has elapsed from the time t1 does not match the time t1a, if the predetermined time T is longer (larger) than zero, as described below, the maximum value of the total torque Td Is smaller than the difference D1 (D2).

  For example, it is assumed that the time when the predetermined time T has passed from the time t1 is the time t1b before the time t1a shown in FIG. In this case, the maximum value of the total torque Td is Tacmax2-a which is larger than the maximum value Tacmax2. On the other hand, the minimum value of the total torque Td is Tacmin2-a. If the difference between the maximum value Tacmax2 and the maximum value Tacmax2-a is Δb1 and the difference between the minimum value Tacmin2 and the minimum value Tacmin2-a is Δb2, then Δb1 <Δb2. That is, when the difference between the maximum value Tacmax2-a and the minimum value Tacmin2-a is D4, the difference D4 is smaller than the difference D1 (D2).

  Further, for example, it is assumed that the time when the predetermined time T has passed from the time t1 is the time t1c after the time t1a shown in FIG. In this case, the maximum value of the total torque Td is Tacmax2. On the other hand, the minimum value of the total torque Td is Tacmin2-b which is smaller than Tacmin2-a and larger than Tacmin2-a. Then, assuming that the difference between the maximum value Tacmax2 and the minimum value Tacmin2-b is D5, the difference D5 is smaller than the difference D1 (D2).

  However, the difference D3 when the time when the predetermined time T has passed is the time t1a is smaller than the difference D4 and the difference D5. That is, when the time when the predetermined time T has passed is the time t1a, the difference between the maximum value and the minimum value of the total torque Td becomes the minimum. Therefore, when the length of the predetermined time T is set so that the maximum value of the total torque Td (AC torque Tac) is generated at the time t1a, the vibration and the abnormal noise of the internal combustion engine 20 due to the force caused by the total torque Td are minimized. Become. However, the vehicle 10 (vehicle control ECU 22) cannot detect (calculate) the magnitude of the total torque Td generated in the drive shafts 12FL and 12FR in real time. However, by the following method, it is possible to estimate (calculate) the predetermined time T having the length at which the total torque Td has the maximum value at the time t1a with a certain degree of accuracy.

  That is, here, the integrated body including the second electric motor 16, the reduction mechanism 15, the differential 13, the drive shafts 12FL and 12FR, and the front wheels 11FL and 11FR is referred to as an electric power transmission system EPM.

By the way, as described above, when the force resulting from the rotational motion of the drive wheels and the second electric motor 16 applied to the drive shafts 12FL and 12FR is “input”, the AC torque Tac appearing on the drive shafts 12FL and 12FR is “input”. "Output" due to. Therefore, the function representing the "input" is Laplace-transformed as Fi (s), the function representing the "output" is Laplace-transformed as Fe (s), and the function representing the electric power transmission system EPM is Laplace-transformed. If the transfer function (based on the inertia of the second electric motor 16, the inertia of the front wheels 11FL and 11FR, and the rigidity of the drive shafts 12FL and 12FR) is H (s),
Fe (s) = Fi (s) · H (s) ... Equation (1)
Becomes

  FIG. 3 is a graph showing the transfer function H (s). The resonance frequency of this transfer function H (s) is 15.8 Hz. In other words, one cycle (resonance cycle) of the transfer function H (s) is 63.2 ms (millisecond). Then, as is apparent from FIG. 3, the maximum value P of the transfer function H (s) occurs at a time of about 1/2 of one cycle. In other words, the maximum value P of the transfer function H (s) occurs in about 31 ms (≈63.2 / 2). It should be noted that these values can be obtained by calculation when the electric power transmission system EPM is designed.

  The “input” at time t1 (and the time around it) can be regarded as substantially step input as shown in FIG. Therefore, the graph representing Fi (s) in the time zone from the time t1 to the passage of a minute time has the shape shown in FIG. That is, the value (dB) of Fi (s) in this time zone is substantially constant (NA) except when the frequency is extremely high. Therefore, the value obtained by substantially multiplying the transfer function H (s) by NA becomes Fe (s) in this time zone. In other words, the shape of the graph representing Fe (s) in this time zone is substantially determined by the shape of the graph representing the transfer function H (s). That is, the shape of the graph representing Fe (s) in this time zone is similar to the shape of the graph representing the transfer function H (s) shown in FIG. Therefore, the maximum value of Fe (s) occurs in about 1/2 time of one cycle. In other words, the maximum value of Fe (s) occurs at about 31 ms. Therefore, the AC torque Tac when the vehicle 10 enters the area B from the area A (in other words, the “output” obtained by performing the inverse Laplace conversion of Fe (s)) has the graph shape shown in FIG. That is, it can be estimated that the maximum value (Tacmax) of the AC torque Tac in this case appears at a time point approximately 31 ms after the time when the “input” is applied. That is, in the present embodiment, when the predetermined time T is set to "31 ms" which is 1/2 of the resonance period of the electric power transmission system EPM, the vibration and the abnormal noise of the internal combustion engine 20 due to the force resulting from the total torque Td are minimized. Become.

  The graph of FIG. 5 represents “AC torque Tac when the vehicle 10 enters the area A from the area B”, while the graph of FIG. 2A shows “AC torque Tac of the vehicle 10 enters the area B from the area A”. Further, the AC torque Tac "when the vehicle further enters the area C from the area B is shown. Therefore, there is a difference in the shape of the graph after the time when the maximum value of the both occurs (time t1a in FIG. 2). However, as long as the time when the maximum value occurs is before the time t2, no matter what timing the vehicle 10 enters from the area B to the area C, the time zone of FIG. The graph shape of (a) and the graph shape of FIG. 5 are the same as each other. When the time when the vehicle enters the area C from the area B changes (for example, from the time t2), the shape after the time t1a in the graph of FIG. 2 changes.

  Further, even when the predetermined time T is set to 1/2 of the resonance cycle of the electric power transmission system EPM in this way, the elapsed time, which is the time when the predetermined time T has passed from the time t1, is slightly different from the time t1a. It may shift. However, the smaller the deviation amount between the elapsed time and the time t1a, the smaller the difference between the maximum value and the minimum value of the total torque Td.

  Next, a specific process performed by the vehicle control ECU 22 will be described with reference to the flowchart of FIG. When the ignition switch (not shown) is operated to switch the position of the ignition switch of the vehicle 10 from the off position to the on position, the vehicle control ECU 22 repeatedly executes the routine shown in the flowchart every predetermined time.

  First, the vehicle control ECU 22 determines in step S1001 whether or not the brake pedal is depressed based on the information from the brake pedal sensor.

  When it is determined No in step S1001, the vehicle control ECU 22 once ends the processing of this routine.

  On the other hand, if it is determined Yes in step S1001, the vehicle control ECU 22 proceeds to step S1002 and executes the ABS determination operation. That is, the vehicle control ECU 22 determines whether the slip ratio is larger than the ABS determination threshold value.

  When it is determined No in step S1002, the vehicle control ECU 22 once ends the processing of this routine.

  On the other hand, if it is determined Yes in step S1002, the vehicle control ECU 22 proceeds to step S1003. For example, at time t1 in FIG. 2 when the vehicle 10 enters the area B from the area A, the vehicle control ECU 22 determines Yes in step S1002. The vehicle control ECU 22 that has proceeded to step S1003 sends a signal to the brake actuator 25 to execute ABS control.

  The vehicle control ECU 22 that has completed the process of step S1003 proceeds to step S1004, and determines whether or not the second electric motor 16 is executing the regenerative operation.

  Since it is determined as Yes in step S1001, except when the predetermined regenerative operation prohibition condition is satisfied (for example, when the storage battery 19 has already stored the amount of electric power corresponding to the storage capacity), 2 The electric motor 16 is performing the regenerative operation. That is, except when the regenerative operation prohibition condition is satisfied, the vehicle control ECU 22 determines Yes in step S1004, and proceeds to step S1005. The vehicle control ECU 22 that has proceeded to step S1005 starts measuring time (elapsed time).

  On the other hand, when the regenerative operation prohibition condition is satisfied, the vehicle control ECU 22 makes a negative determination in step S1004 and temporarily ends the processing of this routine.

  The vehicle control ECU 22 that has completed the processing of step S1005 proceeds to step S1006, and determines whether or not a predetermined time T has elapsed from the start of time measurement.

  When it is determined No in step S1006, the vehicle control ECU 22 executes the process of step S1006 again.

  On the other hand, if it is determined Yes in step S1006, the vehicle control ECU 22 proceeds to step S1007 and sends a regenerative operation stop signal to the second electric motor 16.

  The vehicle control ECU 22 that has completed the processing of step S1007 once terminates the processing of this routine.

  Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, the present invention can be applied to a vehicle including an electric motor (however, an in-wheel motor type vehicle is excluded). Therefore, the vehicle 10 may be an electric vehicle (EV vehicle) or a fuel cell vehicle (FC vehicle).

  The vehicle 10 may include only one electric motor that is a drive source of driving wheels.

  10 ... Vehicle, 11FL, 11FR ... Front wheel, 11RL, 11RR ... Rear wheel, 12FL, 12FR, 13 ... Differential gear, 15 ... Reduction mechanism, 16 ... Second electric motor, 17 ... Power split mechanism, 18 ... First electric motor, 20 ... Internal combustion engine, 22 ... Vehicle control ECU, 24FL, 24FR, 24RL, 24RR ... Wheel speed sensor, 25 ... Brake actuator , EPM ... Electric power transmission system, T ... Predetermined time, Tdc ... DC torque, Tac ... AC torque, Td ... Total torque.

Claims (1)

A hydraulic braking device capable of exerting friction braking force on wheels,
An electric motor that, when supplied with electric power, generates a driving force for rotating the drive wheels via the drive shaft and receives a rotational force of the drive wheels via the drive shaft to generate a regenerative braking force. When,
Control means for controlling the hydraulic braking device and the electric motor and for causing the hydraulic braking device to perform anti-skid control when a predetermined condition is satisfied;
Equipped with
The control means,
When the predetermined condition is satisfied when the regenerative braking force is applied to the drive wheels, the electric motor continues to generate the regenerative braking force until a predetermined time elapses from the time when the predetermined condition is satisfied, and , Is configured to cause the electric motor to lose the regenerative braking force when the predetermined time has elapsed from the time when the predetermined condition is satisfied,
Vehicle braking control device.

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