JP2010018192A - Electric braking device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric braking device capable of allowing the braking force to reach the required value while preventing engine stall caused by the drop of battery voltage. <P>SOLUTION: The gradient guard is set, which applies the guard to the changing gradient of the required braking torque according to the drop of the battery voltage. The guard can thus be applied to the changing gradient of the required braking torque when the battery voltage is dropped. Therefore, the power consumption in an actuator 3 can be reduced when the battery voltage is dropped, and the braking force can reach the required value while preventing engine stall caused by the drop of the battery voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric brake device that electrically controls a brake pressure in accordance with a brake operation amount.

  Conventionally, Patent Document 1 proposes an electric brake device for a vehicle in which braking torque is controlled by an electric motor. In this electric brake device, effective braking control is performed by determining whether braking torque is adjusted based on the amount of brake operation, and supplying a current corresponding to the braking torque to the electric motor.

  However, in the electric brake device disclosed in Patent Document 1, the peak value of the electric power consumption of the electric motor when a braking request for suddenly increasing or decreasing the braking torque is issued when the battery voltage decreases. The battery charge capacity may be exceeded. For example, the electric brake device has an advantage that high responsiveness can be obtained as compared with a normal hydraulic brake device. Therefore, the braking torque for generating the 1G deceleration is generated in a short time, and the electric motor Power consumption increases. When such a situation is reached, there is a problem that the battery voltage further decreases, causing engine stall (hereinafter referred to as engine stall).

On the other hand, Patent Document 2 discloses a technique for limiting a current flowing to an electric motor for driving a device in an automobile in consideration of a battery voltage. Specifically, in Patent Document 2, in the electric power steering apparatus, by limiting the current supplied to the electric motor in accordance with the battery voltage, it is possible to suppress a decrease in the battery voltage and ensure the battery voltage at a predetermined value or more. Like that.
Japanese Patent No. 3740007 JP-A 61-285171

  In the electric brake device that determines whether the braking torque is adjusted based on the brake operation amount as shown in Patent Document 1 and supplies a current corresponding thereto to the electric motor, engine stall may occur when the battery is low. For this reason, also for this electric brake device, as shown in Patent Document 2, by limiting the current supplied according to the battery voltage, it is possible to suppress the decrease in the battery voltage and to suppress the occurrence of the engine stall. It will be possible.

  However, if the current supplied to the electric motor provided in the electric brake device is limited according to the battery voltage, the peak value of power consumption of the electric motor can be reduced, but the requested braking force cannot be reached. there is a possibility.

  The present invention has been made in view of the above points, and an object of the present invention is to make it possible to reach a requested braking force while preventing an engine stall due to a decrease in battery voltage.

  In order to achieve the above object, according to the first aspect of the present invention, the battery voltage detection unit (2c) detects the battery voltage, and the braking torque calculation unit (2b) detects the operation detection unit (2a). A gradient guard for calculating the braking torque corresponding to the manipulated variable and further limiting the gradient of change of the braking torque according to the battery voltage detected by the battery voltage detector (2c) in the gradient setting unit (2d) Set. Further, the required braking torque calculation unit (2b) calculates the braking torque as the required braking torque when the change gradient of the braking torque calculated by the braking torque calculation unit (2b) is equal to or less than the gradient guard, and calculates the braking torque. When the gradient of the braking torque calculated in the part (2b) is larger than the gradient guard, the gradient of the braking torque is set as the gradient guard gradient. The electric motor (14, 54) is driven by the command current corresponding to the required braking torque calculated by the required braking torque calculating unit (2b) by the motor driving unit (2e).

  In this way, a gradient guard that applies a guard to the change gradient of the braking torque is set according to the battery voltage. For this reason, when the battery voltage decreases, it is possible to guard the change gradient of the braking torque. Thus, in the electric brake device, it is possible to reach the requested braking force while preventing the engine stall due to the decrease in the battery voltage.

  The invention according to claim 2 is characterized in that the gradient setting section (2d) sets the gradient of the gradient guard to a different value in accordance with the degree of decrease in the battery voltage.

  Thus, the gradient of the gradient guard can be set to a different value depending on the degree of decrease in the battery voltage. For example, a gradient guard that becomes the first gradient when the battery voltage falls below the first threshold (ThA) is set, and the first when the battery voltage falls below a second threshold (ThB) that is smaller than the first threshold (ThA). A gradient guard that becomes a second gradient smaller than the gradient can be set.

  The invention according to claim 3 is characterized in that the gradient setting section (2d) sets the gradient of the gradient guard to different values for the front wheels (FL, FR) and the rear wheels (RL, RR). Thus, the gradient of the gradient guard can be set to different values for the front wheels (FL, FR) and the rear wheels (RL, RR).

  For example, as described in claim 4, in the gradient setting unit (2d), the gradient of the gradient guard is set so that the front wheel (FL, FR) has a larger value than the rear wheel (RL, RR). It is preferable.

  In this way, the required braking torque can be increased on the front wheels (FL, FR) side where higher braking force is required than on the rear wheels (RL, RR) side while setting the gradient guard. . For this reason, power consumption can be reduced compared with the case where both front wheels (FL, FR) and rear wheels (RL, RR) generate braking torque corresponding to the operation amount of the brake operation member (1). . Therefore, in the electric brake device, it is possible to obtain a high braking force with high responsiveness on the front wheels (FL, FR) side which requires a higher braking force while preventing an engine stall due to a decrease in battery voltage. Can do.

  In the fifth aspect of the invention, the motor drive unit (2e) is configured such that the front wheel (FL, FR) electric motor (15, 54) is based on the required braking torque calculated by the required braking torque calculation unit (2b). This is characterized by being driven faster than the electric motors (15, 54) of the rear wheels (RL, RR).

  Thus, for example, after generating a desired required braking torque on the front wheels (FL, FR) and then generating a desired required braking torque on the rear wheels (RL, RR), the front wheels (FL, FR) The generation timing of the braking torque of the rear wheels (RL, RR) can also be shifted. As a result, it is possible to obtain a high braking force with high responsiveness preferentially on the front wheels (FL, FR) side, and it is possible to further reduce power consumption.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
FIG. 1 shows a schematic block configuration of a vehicle to which the electric brake device according to the present embodiment is applied. Moreover, the block structure which extracted the electric brake device in FIG. 1 is shown in FIG. Hereinafter, the configuration of the electric brake device will be described based on these drawings.

  As shown in FIGS. 1 and 2, the electric brake device according to the present embodiment includes a brake pedal 1 corresponding to a brake operation member, an electronic control unit (hereinafter referred to as ECU) 2, and wheels FL, FR, RL, An electric brake actuator 3 for generating a braking force for the RR is provided.

  In this electric brake device, the current is supplied from the battery 4 to the actuator 3 so that the actuator 3 is driven to generate a braking force for each of the wheels FL to RR. At this time, if the power consumption of the actuator 3 is large when the battery voltage is lowered, the charging capacity from the alternator 6 to the battery 4 is exceeded even if the alternator 6 generates power based on the driving of the engine 5 and the battery 4 is charged. there is a possibility. In such a case, the battery voltage falls below the drive lower limit voltage of the engine ECU 7 or the voltage required for ignition of the igniter 8 and causes engine stall. For this reason, in this embodiment, the engine brake is prevented by detecting the voltage of the battery 4 (battery voltage) with the electric brake device and controlling the actuator 3 based on the battery voltage.

  The brake pedal 1 is provided with a pedal operation sensor 1a that outputs a detection signal corresponding to an operation amount of the brake pedal 1, for example, a pedaling force or a stroke amount. A detection signal from the pedal operation sensor 1a is sent to the ECU 2.

  The ECU 2 inputs the detection signal of the pedal operation sensor 1a and the battery voltage, and performs various calculations based on the detection signal and the battery voltage. For example, an instruction current corresponding to a required braking torque to be generated by driving the actuator 3, that is, a braking torque desired to be generated for each wheel FL to RR is obtained, and an instruction current of that magnitude is provided for each wheel FL to RR. The supplied actuator 3 is supplied. Specifically, the ECU 2 includes a pedal operation detection unit 2a, a required braking torque calculation unit 2b, a battery voltage detection unit 2c, an adjustment gradient setting unit (gradient setting unit) 2d, and a motor drive unit 2e.

  The pedal operation detection unit 2a receives a detection signal from the pedal operation sensor 1a to detect an operation amount of the brake pedal 1, for example, a pedaling force or a stroke amount.

  The required braking torque calculation unit 2b calculates a braking torque corresponding to the operation amount of the brake pedal 1 detected by the pedal operation detection unit 2a, and the braking torque gradient set by the acceleration / deceleration gradient setting unit 2d as will be described later. Based on the guard, the braking torque gradient is limited to obtain the required braking torque. That is, the gradient guard sets an upper limit for the change gradient of the braking torque adjustment corresponding to the operation amount of the brake pedal 1, and the upper limit value of the braking torque corresponding to this gradient guard (hereinafter referred to as gradient guard value). Is greater than the required braking torque, the gradient guard value is set.

  The battery voltage detection unit 2c detects the battery voltage by inputting the battery voltage, that is, the potential of the positive terminal of the battery 4 or a potential obtained by dividing it by a voltage dividing resistor or the like. Here, the battery voltage is detected by inputting the battery voltage or a potential obtained by dividing the battery voltage. However, since the battery voltage is originally detected in the engine ECU 7, the detected value is directly input. The battery voltage can also be detected.

  The increasing / decreasing gradient setting unit 2d sets an increasing / decreasing gradient guard for braking torque based on the battery voltage detected by the battery voltage detecting unit 2c. That is, if the required braking torque is suddenly adjusted in a situation where the battery voltage is low, the charging capacity from the alternator 6 to the battery 4 may be exceeded as described above, and engine stall may occur. For this reason, the lower limit gradient calculation unit 2d detects that the battery voltage is decreasing, and sets the gradient guard according to the decrease degree.

  The motor driving unit 2e generates a command current corresponding to the required braking torque, that is, a required braking torque, based on the required braking torque calculated based on the operation amount of the brake pedal 1 and the gradient guard value in the required braking torque calculating unit 2b. The current value to be supplied to the actuator 3 is calculated and supplied to the actuator 3.

  As shown in FIG. 1, the actuator 3 is provided on each of the four wheels FL to RR, but in FIG. 2, one provided on one of the four wheels is representatively illustrated. . The actuator 3 of the present embodiment is an electric disc brake, and a pair of brake pads 11 and 12 disposed so as to sandwich the disc rotor 10 on both sides of the disc rotor 10 and the disc rotor 10 rotating together with the wheels FL to RR. And a caliper 13 that holds the pair of brake pads 11 and 12 across the disk rotor 10.

  In the caliper 13, an electric motor 14 that is rotated according to the current supplied from the motor drive unit 2 e, a speed reducer unit 15 that decelerates the rotation of the rotating shaft of the electric motor 14, and a speed reduced by the speed reducer unit 15 A linear motion conversion unit 16 that converts a force into an axial force to linearly move a piston (not shown) is disposed. Then, the linear motion conversion unit 16 converts the rotational force in the electric motor 14 and the speed reducer unit 15 into the linear motion force, thereby causing the piston to linearly move. When the piston is linearly moved toward the disk rotor 10, the disk rotor 10 is sandwiched between the brake pads 11 and 12, and a frictional force that stops the rotation of the disk rotor 10 is applied. As a result, the rotation of the wheels FL to RR rotating together with the disc rotor 10 is also stopped, and the braking force is obtained by the frictional force generated between the tire attached to the wheels FL to RR and the road surface. . On the contrary, when the piston is linearly moved away from the disk rotor 10, the brake pads 11 and 12 are separated from the disk rotor 10 and the generated braking force is released.

  The detailed structure of the actuator 3 is well known in Japanese Patent Application Laid-Open No. 2005-67401 and the like, and thus the description thereof is omitted.

  In the electric brake device described above, the required braking torque output process is performed. The required braking torque output process will be described with reference to the flowchart of the required braking torque output process shown in FIG. Note that the required braking torque output processing shown in FIG. 3 is performed by each of the elements 2a to 2e constituting the ECU 2 described above, and is executed at predetermined control cycles when an ignition switch (not shown) is turned on.

  First, as shown in FIG. 3, in step 100, a braking torque is calculated. This process is performed by detecting an operation amount of the brake pedal 1 based on a detection signal from the pedal operation sensor 1a and calculating a braking torque corresponding to the detected operation amount.

  Next, it progresses to step 105 and detects a battery voltage. This process is performed based on the battery voltage or a potential obtained by dividing the battery voltage.

  Subsequently, in step 110, it is determined whether or not the battery voltage is equal to or lower than a predetermined first threshold value ThA. Here, the first threshold ThA is a threshold for determining that the battery voltage is decreasing. If the battery voltage is equal to or lower than the first threshold ThA, it indicates that the battery voltage is decreasing. Yes. For this reason, if an affirmative determination is made here, the routine proceeds to step 115. If a negative determination is made, the battery voltage has not dropped, and there is no need to set a gradient guard, so the process ends.

  In step 115, it is determined whether or not the battery voltage is equal to or lower than the second threshold value ThB. Here, the second threshold ThB is a threshold used for examining the degree of decrease in the battery voltage. The second threshold value ThB is set to a value smaller than the first threshold value ThA described above. If the second threshold value ThB is larger than the second threshold value ThB, the degree of decrease in the battery voltage is not so large. It is determined that the degree of decrease is large. For this reason, if a negative determination is made in this step, the routine proceeds to step 120 and the gradient guard 1, that is, the first gradient that is relatively steep, is set. A second gradient is set which is a moderate gentle gradient.

  When the gradient guard 1 is set in step 120, the process proceeds to step 130, and it is determined whether or not the gradient of the braking torque is equal to or greater than the gradient guard 1. That is, if the braking torque gradient is large, engine stall may occur, and it is not preferable to output the braking torque calculated in step 100 as the required braking torque as it is. For this reason, the gradient of the braking torque is compared with that of the gradient guard 1. Note that the gradient of the braking torque is obtained, for example, by calculating the difference between the braking torque calculated in the current control cycle in step 100 and the braking torque calculated in the previous control cycle. Here, if an affirmative determination is made, the process proceeds to step 135, and if a negative determination is made, the process proceeds to step 140.

  In step 135, if the braking torque calculated in step 100 is directly output as the required braking torque, an engine stall may occur. Therefore, the gradient guard value corresponding to the set gradient guard 1, that is, in the previous control cycle, may occur. A value obtained by adding or subtracting the braking torque according to the first gradient to the calculated braking torque is calculated. This gradient guard value is the upper limit value (or lower limit value) of the braking torque at the current control cycle. Then, this gradient guard value is output as a required braking torque.

  Further, in step 140, it is considered that the engine stall does not occur even if the braking torque calculated in step 100 is output as it is, and therefore the braking torque calculated in step 100 is output as the required braking torque.

  On the other hand, even when the gradient guard 2 is set in step 125, it is determined in step 145 whether the gradient of the braking torque is equal to or greater than the gradient guard 2. That is, if the gradient of the required braking torque is large, engine stall may occur. Therefore, it is not preferable to output the braking torque calculated in step 100 as the required braking torque as it is. For this reason, the gradient of the braking torque is compared with that of the gradient guard 2. If an affirmative determination is made here, the process proceeds to step 150, and if a negative determination is made, the process proceeds to step 155.

  In step 150, if the braking torque calculated in step 100 is directly output as the required braking torque, an engine stall may occur. Therefore, the gradient guard value corresponding to the set gradient guard 2, that is, in the previous control cycle, is assumed. A value obtained by adding or subtracting the braking torque according to the second gradient to the calculated required braking torque is calculated. This gradient guard value is the upper limit (or lower limit) of the required braking torque at the current control cycle. Then, this gradient guard value is output as a required braking torque.

  Further, in step 155, it is considered that the engine stall does not occur even if the braking torque calculated in step 100 is output as the required braking torque as it is, so the braking torque calculated in step 100 is output as the required braking torque.

  When the required braking torque is calculated in this way, the motor drive unit 2e calculates the corresponding command current. Then, when the command current flows through the actuator 3, the electric motor 14 is rotated, and the rotation is decelerated by the speed reducer unit 15, and then converted by the linear motion conversion unit 16 into a force in a straight direction. As a result, the piston in the linear motion converting portion 16 is caused to linearly move.

  Thus, when the brake pedal 1 is depressed, the disc rotor 10 is sandwiched between the brake pads 11 and 12, and a braking force is generated. On the contrary, when the depression of the brake pedal 1 is released, the brake pads 11 and 12 are separated from the disk rotor 10 and the generated braking force is released.

  As described above, the required braking torque output process shown in FIG. 3 is performed by the elements 2a to 2e constituting the ECU 2. Specifically, step 100 is performed by the pedal operation detection unit 2a and the required braking torque calculation unit 2b in the ECU 2, step 105 is performed by the battery voltage detection unit 2c, and steps 115 to 125 are the lower limit gradient calculation. Step 130 to Step 155 are performed by the required braking torque calculation unit 2b.

  As described above, the gradient guard that applies the guard to the change gradient of the braking torque according to the decrease in the battery voltage is set. For this reason, the gradient guard changes as follows according to the battery voltage, and the power consumption in the actuator 3 changes. 4A and 4B are graphs showing the relationship between the change in braking torque with respect to the battery voltage and the power consumption of the actuator 3, respectively.

  As shown in FIG. 4 (a), if the braking torque corresponding to the operation amount of the brake pedal 1 is shown as a broken line in the figure, the instantaneous actuator 3 as shown in FIG. 4 (b). As shown by the broken line in the figure, the power consumption becomes extremely large. For this reason, there is a possibility that engine stall occurs when the battery voltage is lowered.

  On the other hand, when the battery voltage is lower than the first threshold ThA, a gradient guard is set. If the battery voltage is equal to or lower than the first threshold ThA and greater than the second threshold ThB, the gradient guard 1 and the battery voltage are set. Is equal to or less than the second threshold ThB, the gradient guard 2 is set. For this reason, if the braking torque corresponding to the operation amount of the brake pedal 1 is large when the battery is low, the gradient guard is set, and the change gradient of the required braking torque is limited according to the degree of the decrease in the battery voltage. As a result, when the gradient guard 1 is set as shown by the thin lines in FIGS. 4A and 4B, compared to the case where the gradient according to the braking torque corresponding to the operation amount of the brake pedal 1 is set. It becomes possible to reduce power consumption. Further, when the gradient guard 2 is set as shown by a bold line, it is possible to further reduce power consumption. Even when the change gradient of the braking torque is limited in this way, the braking torque that is finally generated is the same as the braking torque corresponding to the amount of operation of the brake pedal 1, and thus the requested braking force is generated. Is also possible.

  Therefore, in the electric brake device, it is possible to reach the requested braking force while preventing the engine stall due to the decrease in the battery voltage.

(Second Embodiment)
A second embodiment of the present invention will be described. In this embodiment, the gradient guard shown in the first embodiment is set to a different value for each of the front wheels FL, FR and the rear wheels RL, RR, and the other parts are the same as those in the first embodiment. Only parts different from the first embodiment will be described.

  FIG. 5 is a flowchart of a required braking torque output process executed by the electric brake device of the present embodiment.

  As shown in this figure, the process is basically the same as the required braking torque output process executed by the electric brake device of the first embodiment shown in FIG. 3, but the battery voltage is larger than the second threshold ThB and the first When the threshold value is ThA or less, the difference is that in step 120A, a front wheel (Fr) gradient guard 1 and a rear wheel (Rr) gradient guard 1 are set instead of step 120 in FIG. When the battery voltage is equal to or lower than the second threshold ThB, the front wheel (Fr) gradient guard 2 and the rear wheel (Rr) gradient guard 2 are set in step 125A instead of step 125 in FIG. The point is also different.

  In this way, the gradient guards 1 and 2 can be set separately for the front wheels and the rear wheels, like the front wheel gradient guards 1 and 2 and the rear wheel gradient guards 1 and 2. When the front wheel gradient guards 1 and 2 and the rear wheel gradient guards 1 and 2 are divided as described above, in step 130 and step 145, whether the braking torque gradient is equal to or greater than the gradient guards 1 and 2. When determining whether or not, a comparison is made for each wheel FL to RR. Thereby, the required braking torque according to the gradient guards 1 and 2 which are different with respect to each of the front wheels FL and FR and the rear wheels RL and RR can be obtained.

  FIGS. 6A and 6B are graphs showing the relationship between the change in the required braking torque with respect to the battery voltage and the power consumption of the actuator 3, respectively.

  As shown in FIG. 6A, the gradient guard 1 is divided into a front wheel gradient guard 1 and a rear wheel gradient guard 1, and the front wheel gradient guard 1 has a larger gradient than the rear wheel gradient guard 1. I am doing so. The gradient guard 2 is also divided into a front wheel gradient guard 2 and a rear wheel gradient guard 2 so that the front wheel gradient guard 2 has a larger gradient than the rear wheel gradient guard 2. Accordingly, the required braking torque can be increased on the front wheels FL and FR sides where higher braking force is required than on the rear wheels RL and RR sides while setting the gradient guards 1 and 2.

  Even in such a case, as shown in FIG. 6B, the braking torque corresponding to the amount of operation of the brake pedal 1 is generated in both the front wheels FL, FR and the rear wheels RL, RR. Thus, power consumption in the actuator 3 can be reduced. Therefore, in the electric brake device, it is possible to obtain a high braking force with good responsiveness on the front wheels FL and FR side that require a higher braking force while preventing an engine stall due to a decrease in battery voltage. .

(Third embodiment)
A third embodiment of the present invention will be described. In the present embodiment as well, the gradient guard is set to a different value for each of the front wheels FL and FR and the rear wheels RL and RR as in the second embodiment, and the generation timing of the braking torque for the front wheels FL and FR and the rear wheels RL and RR Since the other parts are the same as those of the second embodiment, only the parts different from the second embodiment will be described.

  FIG. 7 is a flowchart of requested braking torque output processing executed by the electric brake device of the present embodiment.

  As shown in this figure, this is basically the same as the required braking torque output process executed by the electric brake device of the second embodiment shown in FIG. The processing after setting the gradient guards 1 and 2 is different from that of the second embodiment.

  Specifically, after the front wheel gradient guard 1 and the rear wheel gradient guard 1 are set as the gradient guard 1 in step 120A, if the braking torque is greater than or equal to the gradient guard 1 in step 130, the process proceeds to step 165. Here, as the gradient guard 1 to be compared with the braking torque, the larger one of the gradient guard 1 for the front wheels and the gradient guard 1 for the rear wheels is used.

  In step 165, the braking torque is adjusted according to the gradient of the front wheel gradient guard 1 with respect to the set gradient guard value corresponding to the front wheel gradient guard 1, that is, the required braking torque calculated in the previous control cycle. The calculated value is calculated. This gradient guard value is the upper limit (or lower limit) of the required braking torque at the current control cycle. The gradient guard value is output as a required braking torque for the front wheels FL and FR.

  Subsequently, the routine proceeds to step 170, where it is determined whether the braking torque generated on the front wheels FL, FR has reached the required braking torque, and if the determination is affirmative, the routine proceeds to step 175. And the gradient guard value corresponding to the set rear wheel gradient guard 1, that is, the value obtained by adjusting the braking torque according to the gradient of the rear wheel gradient guard 1 with respect to the required braking torque calculated in the previous control cycle. Is calculated. This gradient guard value is the upper limit (or lower limit) of the required braking torque at the current control cycle. Then, this gradient guard value is output as the required braking torque for the rear wheels RL and RR.

  On the other hand, after the front wheel gradient guard 2 and the rear wheel gradient guard 2 are set as the gradient guard 2 in step 125A, if the braking torque is greater than or equal to the gradient guard 2 in step 145, the process proceeds to step 180. Here, as the gradient guard 2 to be compared with the braking torque, the one having the larger gradient of the front wheel gradient guard 2 and the rear wheel gradient guard 2 is used.

  Then, in step 180, the braking torque is adjusted according to the gradient of the front wheel gradient guard 2 with respect to the set gradient guard value corresponding to the front wheel gradient guard 2, that is, the required braking torque calculated in the previous control cycle. The calculated value is calculated. This gradient guard value is the upper limit (or lower limit) of the required braking torque at the current control cycle. The gradient guard value is output as a required braking torque for the front wheels FL and FR.

  Subsequently, the routine proceeds to step 185, where it is determined whether or not the braking torque generated on the front wheels FL, FR has reached the required braking torque. If the determination is affirmative, the routine proceeds to step 190. And the gradient guard value corresponding to the set rear wheel gradient guard 2, that is, the value obtained by adding or subtracting the braking torque according to the gradient of the rear wheel gradient guard 2 with respect to the required braking torque calculated in the previous control cycle. Is calculated. This gradient guard value is the upper limit (or lower limit) of the required braking torque at the current control cycle. Then, this gradient guard value is output as the required braking torque for the rear wheels RL and RR.

  FIGS. 8A and 8B are graphs showing the relationship between the change in the required braking torque with respect to the battery voltage and the power consumption of the actuator 3, respectively.

  As shown in FIG. 8A, not only the gradient guards 1 and 2 are divided into the front wheel gradient guards 1 and 2 and the rear wheel gradient guards 1 and 2, but also the desired braking required for the front wheels FL and FR. After the torque is generated, a desired required braking torque is also generated on the rear wheels RL and RR. As a result, the required braking torque can be obtained earlier on the front wheels FL and FR side, which require more responsiveness, than on the rear wheels RL and RR sides.

  Further, as shown in FIG. 8 (b), the power consumption in the actuator 3 is further suppressed as compared with the case where the braking torque is simultaneously raised for both the front wheels FL, FR and the rear wheels RL, RR. Is possible.

  Thus, after the desired required braking torque is generated on the front wheels FL and FR, the desired required braking torque is also generated on the rear wheels RL and RR, and the braking of the front wheels FL and FR and the rear wheels RL and RR is performed. The generation timing of torque can also be shifted. Accordingly, it is possible to obtain a high braking force with high responsiveness preferentially on the front wheels FL and FR sides, and it is possible to further reduce power consumption in the actuator 3.

(Fourth embodiment)
In each of the above embodiments, the case where the present invention is applied to the one that drives the electric motor 14 provided in the actuator 3 as shown in FIG. 1 has been described. The present invention can also be applied to an electric brake device having a structure that pressurizes (C).

  FIG. 9 is a diagram showing an overall configuration of the electric brake device according to the present embodiment. As shown in this figure, the electric brake device according to the present embodiment includes a brake pedal 51, a pedal operation sensor 51a, and a stroke simulator 52 that are operated in response to a driver's braking request. The stroke simulator 52 includes a piston 52a that is depressed by the brake pedal 51, a cylinder 52b in which the piston 52a slides, and a spring 52c that is disposed in the cylinder 52b. The brake pedal 51 and the piston 52a are connected. When the brake pedal 51 is depressed, a reaction force and a stroke corresponding to the pedal operation amount are applied to the brake pedal 51 by the spring force from the spring 52c. It is like that.

  In addition, the electric brake device includes an M / C 53, an electric motor 54 and a gear mechanism 55, an ABS actuator 56, and W / Cs 57a to 57d corresponding to the respective wheels as a configuration separated from the brake pedal 51. .

  The M / C 53 is divided into a primary chamber 53b and a secondary chamber 53c by a master piston 53a, and the primary chamber 53b is connected to the first piping system and the secondary chamber 53c is connected to the second piping system. Then, as the piston rod 53d moves in the axial direction, the master piston 53a is moved to increase the brake fluid pressure (hereinafter referred to as M / C pressure) in each of the chambers 53b and 53c. The hydraulic pressure (hereinafter referred to as W / C pressure) is increased. Further, the M / C 53 is provided with a master reservoir 53e, and each of the rooms 53b and 53c is connected to the master reservoir 53e.

  The electric motor 54 generates a rotational driving force (output) corresponding to a detection signal from the pedal operation sensor 51a. The gear mechanism 55 is configured by a ball screw, a rack and pinion, and the like, and converts the rotational driving force of the electric motor 54 into a straight motion. When the piston rod 53d is driven by the gear mechanism 55 and the rotational driving force of the electric motor 54 is converted into a linear motion by the gear mechanism 55, the piston rod 53d is driven according to the converted force. . That is, an M / C pressure corresponding to the rotational driving force of the electric motor 54 is generated, and a W / C pressure corresponding to the M / C pressure is generated. The gear mechanism 55 may be provided with a reduction gear and a speed increase gear in order to adjust the required motor torque and the required axial force.

  The ABS actuator 56 has a general configuration similar to that of the prior art, and is configured so that the W / C pressure increase, maintenance, and pressure reduction generated in each W / C 57a to 57d can be controlled independently for each wheel. Has been. Since the ABS actuator 56 has a conventionally well-known general structure, a detailed structure is omitted.

  Further, the electric brake device is provided with an ECU 58 for driving the electric motor 54 and the ABS actuator 56. A detection signal or the like from the pedal operation sensor 51a is input to the ECU 58. The ECU 58 performs various calculations based on the input signals, and outputs drive signals to the electric motor 54 and the ABS actuator 56 based on the operation amount of the brake pedal 51 determined by the calculations.

  In this way, a device that drives the electric motor 54 based on the operation amount of the brake pedal 51, generates the M / C pressure in the M / C 53, and generates the W / C pressure based thereon, that is, the electric motor. The above embodiments can also be applied to an electric brake device that generates a W / C pressure via a mechanism that generates a brake fluid pressure by a driving force of 54.

(Other embodiments)
In the above embodiment, as an electric brake device, a structure that directly generates a braking force by driving the electric motor 14 as in the first to third embodiments, and an electric motor 54 as in the fourth embodiment. An example of the structure in which the brake fluid pressure is generated in the hydraulic circuit by driving and thereby the braking force is generated is shown. However, these are merely examples, and the present invention can be applied to any structure as long as the braking force is generated directly through the electric motors 14 and 54 or via the hydraulic circuit. Can do.

1 is a diagram showing a schematic block configuration of a vehicle to which an electric brake device according to a first embodiment of the present invention is applied. It is a figure which shows the block structure which extracted the electric brake device in FIG. It is a flowchart of a required braking torque output process. (A), (b) is the graph which showed the relationship of the change of the request | requirement braking torque with respect to a battery voltage, and the power consumption of the actuator 3, respectively. It is a flowchart of the required braking torque output process which the electric brake device of 2nd Embodiment of this invention performs. (A), (b) is the graph which showed the relationship of the change of the request | requirement braking torque with respect to a battery voltage, and the power consumption of the actuator 3, respectively. It is a flowchart of the required braking torque output process which the electric brake device of 3rd Embodiment of this invention performs. (A), (b) is the graph which showed the relationship of the change of the request | requirement braking torque with respect to a battery voltage, and the power consumption of the actuator 3, respectively. It is the figure which showed the whole structure of the electric brake device concerning 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,51 ... Brake pedal, 1a, 51a ... Pedal operation sensor, 2 ... ECU, 2a ... Pedal operation detection part, 2b ... Request brake torque calculation part, 2c ... Battery voltage detection part, 2d ... Lower limit gradient calculation part, 2d ... Adjustable gradient setting unit, 2e ... motor drive unit, 3 ... actuator, 4 ... battery, 5 ... engine, 6 ... alternator, 7 ... engine ECU, 10 ... disc rotor, 11, 12 ... brake pad, 13 ... caliper, 14 ... Electric motor, 15 ... reducer, 16 ... linear motion converter, 52 ... stroke simulator, 53 ... M / C, 54 ... electric motor, 55 ... gear mechanism, 56 ... ABS actuator

Claims (5)

In the electric brake device that drives the electric motor (14, 54) by the command current and generates a braking force on the vehicle by pressing the friction material (11, 12) of each wheel against the friction target material (10),
An operation detection unit (2a) for detecting an operation amount of the brake operation member (1, 51);
A battery voltage detector (2c) for detecting the battery voltage;
A braking torque calculator (2b) for calculating a braking torque corresponding to the operation amount detected by the operation detector (2a);
A gradient setting unit (2d) for setting a gradient guard for limiting the gradient of change in the braking torque according to the battery voltage detected by the battery voltage detection unit (2c);
When the change gradient of the braking torque calculated by the braking torque calculation unit (2b) is equal to or less than the gradient guard, the braking torque is calculated as a required braking torque, and is calculated by the braking torque calculation unit (2b). A required braking torque calculation unit (2b) for calculating a required braking torque with the gradient of the braking torque as a gradient of the gradient guard when the gradient of the braking torque is larger than the gradient guard;
A motor drive unit (2e) that drives the electric motor (14, 54) with an instruction current corresponding to the required brake torque calculated by the required brake torque calculation unit (2b). Electric brake device.   2. The electric brake device according to claim 1, wherein the gradient setting unit (2 d) sets the gradient of the gradient guard to a different value according to the degree of decrease in the battery voltage.   3. The electric motor according to claim 1, wherein the gradient setting unit (2 d) sets the gradient of the gradient guard to different values for the front wheels (FL, FR) and the rear wheels (RL, RR). Brake device.   The gradient setting unit (2d) sets the gradient of the gradient guard so that the front wheel (FL, FR) has a larger value than the rear wheel (RL, RR). 3. The electric brake device according to 3.   The motor drive unit (2e) moves the electric motors (15, 54) of the front wheels (FL, FR) based on the required braking torque calculated by the required braking torque calculation unit (2b). The electric brake device according to any one of claims 1 to 4, wherein the electric brake device is driven earlier than the electric motors (15, 54) of the rear wheels (RL, RR).

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