JP5176307B2 - Vehicle regenerative / friction cooperative braking control system - Google Patents

Description

  The present invention relates to a braking control device for a vehicle such as an automobile, and more particularly to a braking control device that performs regenerative / friction cooperative control using a combination of friction braking and regenerative braking.

  In a vehicle such as an automobile equipped with an electric motor as a driving device, that is, in a braking system of a hybrid vehicle or an electric vehicle, kinetic energy of the vehicle is combined with friction braking for braking rotation of a wheel due to friction between a brake shoe and a brake pad. Regenerative braking that brakes the vehicle by recovering the vehicle as electrical energy by a generator (or generator motor) is employed. The electrical energy recovered by regenerative braking is used as energy for operating the electric motor that drives the vehicle, so it is more advantageous than friction braking from the viewpoint of vehicle energy efficiency, but only the energy recovery efficiency. In consideration of this, it may not always be possible to achieve vehicle braking adapted to the braking operation of the vehicle driver or automatic control of vehicle motion. Therefore, in order to control the braking system in consideration of both the braking required by the driver's braking operation or vehicle motion and the efficiency of recovery of vehicle kinetic energy by regenerative braking, Various types of “regenerative / friction cooperative control” have been proposed in which braking is controlled in coordination. For example, in Patent Documents 1 and 2, regenerative braking is prioritized during normal braking, and friction braking is uncomfortable with the driver's braking operation feeling during braking when a predetermined condition is satisfied. It is disclosed to carry out without giving. Further, in Patent Document 3, in a braking system that uses both a regenerative braking device and a hydraulic braking device, it is based on the knowledge that the braking effectiveness of the hydraulic braking device depends on the temperature of the brake pad. Thus, it has been proposed to change the distribution between the regenerative braking amount and the hydraulic braking amount based on the estimated temperature of the brake pad.

As described above, when considering the energy efficiency of the vehicle, regenerative braking is used preferentially or as much as possible in braking the vehicle, and friction braking achieves the required change or magnitude of the braking force in regenerative braking. It is preferably used for the purpose of not being able to do so or not impairing the driver's braking feeling. Therefore, in braking regenerative / friction cooperative control, friction braking is preferably used as a supplement to regenerative braking. In principle, when the change and magnitude of the required braking force or braking amount (kinetic energy of the vehicle or wheels absorbed by the braking device per unit time) can be achieved only by regenerative braking, regenerative braking is only possible. Friction braking is used when realization of the required braking force or braking amount cannot be applied by regenerative braking or when adaptation is difficult. The amount of regenerative braking that can be used (the vehicle or wheel kinetic energy that is electrically absorbed from the generator to the battery per unit time) or the maximum regenerative braking force depends on the movement of the driver or vehicle during one braking. Even if there is no change in the braking force required by the automatic control device, the amount of friction braking (the kinetic energy of the vehicle or wheel absorbed by the friction per unit time) can vary depending on the battery charge level, temperature, vehicle speed, etc. Alternatively, the friction braking force is controlled so as to fluctuate in accordance with the change in the regenerative braking amount or the regenerative braking force.
JP-A-7-250402 JP 2000-156901 A JP2005-14692

  By the way, in general, in a friction element or brake pad employed in a friction braking device, a so-called “build-up phenomenon”, that is, a change in the amount of friction braking or friction braking during one braking. A phenomenon is known in which the coefficient of friction changes depending on the usage history. When the friction coefficient changes, the friction braking amount, that is, the absorption amount per unit time of the kinetic energy of the vehicle or the wheel due to friction changes, and therefore, even if the control command given to the friction braking device does not change, the friction braking is performed. The braking force generated by the device will vary from moment to moment. In particular, in a braking system that performs regenerative / friction braking coordinated control, the friction braking amount or the friction braking force changes to the regenerative braking amount or the regenerative braking force even if the braking force required for the vehicle does not change. It is controlled to change accordingly. Therefore, the frequency of friction braking amount or friction braking force or the frequency of starting and stopping the friction braking device increases, and the history of changes in the amount of friction braking during the execution of friction braking varies. The braking force generated in the vehicle may become unstable due to a change in the friction coefficient due to the influence of the phenomenon. Such unstable fluctuations in braking force also cause deterioration in braking feeling, for example, when transitioning from regenerative braking to friction braking (when “regenerative braking and friction braking are switched”). .

  However, in the conventional regenerative / friction cooperative control, there has been no example dealing with the friction brake pad buildup phenomenon as described above. Patent Document 3 discloses control for changing the distribution between the regenerative braking amount and the hydraulic braking amount depending on the temperature of the brake pad, but the friction coefficient changes depending on the history of changes in the friction braking amount. It does not solve the problem that the friction braking amount changes due to the build-up phenomenon. Further, in this document, since the regenerative / friction distribution ratio is changed, if the same control is executed when regenerative braking should be operated at the maximum limit value, energy efficiency is reduced. Become.

  According to the present invention, in the regenerative / friction braking cooperative control as described above, the influence of the friction element or the brake pad build-up phenomenon on the friction braking amount and the braking force generated in the vehicle is reduced, and the braking feeling is improved. An improved braking control device is provided.

  The braking control device of the present invention performs a braking control device that performs cooperative control of regenerative braking and friction braking in a vehicle having a regenerative braking device and a friction braking device, that is, so-called “regenerative / friction cooperative control”. And a means for determining a control amount of the friction braking device based on a target friction braking amount calculated from a required braking force and a regenerative execution amount in the regenerative braking device, and an operation of the friction braking device. Is started, the control amount of the friction braking device is corrected so that the target friction braking amount matches the braking amount realized by the friction braking device based on the braking energy absorbed by the friction braking from the start of the operation. Means.

  According to the above-described braking control device of the present invention, first, the required braking force (the braking system required for the entire braking system including the regenerative braking device and the friction braking device by the driver's braking operation or the automatic control of the vehicle motion, etc. The control amount of the friction braking device is determined on the basis of the target friction braking amount calculated from the power) and the regenerative execution amount (the kinetic energy of the vehicle or wheels collected in the regenerative braking device). However, as described above, the amount of friction braking actually generated in the friction braking device depends on the magnitude of the friction braking amount after the start of friction braking and the history of changes due to the effect of the build-up phenomenon. Therefore, in the present invention, the target friction braking amount and the braking amount realized by the friction braking device coincide with each other with reference to the braking energy absorbed by friction braking from the start of operation of the friction braking device. Thus, the control amount of the friction braking device is corrected. The target friction braking amount corresponds to the friction braking amount that should be achieved at present, which is determined from the required braking force and the regeneration execution amount, and the braking amount realized by the friction braking device is the friction force that is actually achieved. Since it is the braking amount, by making the target friction braking amount and the braking amount realized by the friction braking device coincide with each other, the variation of the friction braking force due to the build-up phenomenon is compensated, and the planned braking force, That is, the required braking force is achieved. In the above description, “braking energy” refers to energy converted from kinetic energy of the vehicle into electrical energy or thermal energy by braking, and “braking energy absorbed by friction braking” refers to a friction braking device. The energy absorbed from the kinetic energy of the vehicle by friction braking by means of.

  The braking energy absorbed by friction braking is considered to correspond to the amount of change in internal energy accumulated in the friction element of the friction braking device from the start of operation of the friction braking device, or the amount of change in temperature of the friction element. Therefore, the amount of change in the temperature of the friction element can be used as an index of braking energy absorbed by friction braking. Therefore, in the above-described configuration of the present invention, the control amount of the friction braking device may be corrected based on the amount of change in the temperature of the friction element from the start of operation of the friction braking device. Further, as described above, the build-up phenomenon appears as a change in the friction coefficient of the friction element of the friction braking device depending on the magnitude and change of the friction braking amount after the start of friction braking. Therefore, in the above-described configuration, the correction of the control amount of the friction braking device is absorbed by the friction braking, considering the change of the friction coefficient as a function of the braking energy absorbed by the friction braking from the start of the operation of the friction braking device. A change in the coefficient of friction may be compensated based on the amount of change in braking energy or temperature of the friction element. As a result, the amount of friction braking to be actually achieved matches the amount of friction braking currently achieved, or the difference between them is reduced, and the fluctuation of the braking force due to the build-up phenomenon generated in the friction braking device is reduced. It will be reduced or compensated.

  In the regenerative / friction cooperative control that preferentially executes regenerative braking as described above, the driver's braking feeling deteriorates due to the build-up phenomenon, as described above. This is conspicuous in the so-called “replacement” in which the regenerative braking is terminated and the state is changed to the state of only friction braking from the state where the regenerative braking is executed by the braking device. Therefore, in the braking control device of the present invention, when the reduction of the regeneration execution amount for the stop processing of the regenerative braking device is started, the braking absorbed by the friction braking from the start of the operation of the friction braking device. The control amount of the friction braking device may be corrected based on the energy. However, actually, the driver's braking feeling deteriorates due to the build-up phenomenon also occurs when a change in the friction braking amount is instructed in accordance with a change in the regeneration execution amount by the regenerative braking device. Therefore, the control amount of the friction braking device may be corrected based on braking energy absorbed by friction braking since the operation of the friction braking device before the operation of the regenerative braking device was started.

  The build-up phenomenon of the friction element is a phenomenon that occurs during one friction braking. Once the friction braking is stopped, the history of the friction braking amount until then is the build-up phenomenon during the next friction braking. Is considered to have little effect. Accordingly, in the above braking control, when the friction braking is stopped, the energy amount absorbed by the friction braking until then is used to correct the control amount of the friction braking device when the friction braking device is operated next time. In this case, it does not have to be considered.

  As described above, according to the present invention, in a vehicle braking system in which regenerative / friction cooperative braking control is performed, deterioration of braking feeling due to a build-up phenomenon in a friction element of a friction braking device is suppressed. In the braking control according to the present invention, the regenerative execution amount is not corrected. Therefore, the advantage of the regenerative / friction cooperative control that preferentially executes the regenerative braking to improve the energy efficiency is not impaired. The braking control device of the present invention can be advantageously used particularly in a braking system of a hybrid vehicle or an electric vehicle.

  The build-up phenomenon occurs even in a braking system in which braking is performed only by friction braking. In this case, the friction braking device remains activated during a single braking operation. Even if the phenomenon occurs, the generated braking force does not change suddenly. If there is an excess or deficiency in the generated braking force with respect to the required acceleration / deceleration or vehicle speed, those values are smoothly and smoothly corrected when calculating the required braking force or the control amount to the braking device from the required acceleration / deceleration. Therefore, it is considered that the build-up phenomenon does not immediately lead to deterioration of the braking feeling. In contrast, when regenerative braking and friction braking are used in combination, particularly when regenerative braking is preferentially used and friction braking is used as a supplement to the regenerative braking, friction braking is: It may be used halfway or intermittently during a single braking operation. In that case, the history of friction braking use varies, and this creates a difference in the degree of build-up phenomenon, making it difficult to control the braking force, and causing unstable fluctuations in the generated braking force as described above. And deterioration of braking feeling can occur. According to the present invention, the friction braking amount is adjusted for each friction braking operation by adjusting the control amount to the friction braking device with reference to the braking energy absorbed by the friction braking from the start of the friction braking as the change history of the friction braking amount. As described above, the deterioration of the braking feeling when the friction braking is used as a supplement to the regenerative braking is suppressed.

  Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention.

Configuration of Device FIG. 1 (A), in which the drive system and a brake system of the hybrid vehicle in which the preferred embodiment of the brake control device is mounted of the present invention shown schematically. Referring to the figure, an output shaft (crankshaft) 12 of an internal combustion engine 10 schematically shown as a four-cylinder engine is a first motor generator via a driving force distribution device 14 formed of a planetary gear device or the like. The motor (MG1) 16 and the second motor generator (MG2) 18 are connected so as to differentially transmit rotational power. Transmission of the rotational driving force of the left and right wheels 30 and 32 is performed by a gear 20 that is coaxially provided on the rotation shaft of the second motor generator (MG2) 18 of the internal combustion engine 10 and a gear 22 that meshes with the gear 22. This is done through the moving gear device 24 and the left and right axles 26 and 28. The electric circuits of the motor generators MG1 and MG2 are connected to a battery (B) 36 via an inverter (I) 34.

  The braking of the left and right wheels 30 and 32 is performed by friction braking force selectively generated in a friction braking device (only the wheel cylinders 40 and 42 are shown) provided in each wheel, the internal combustion engine 10, Depending on the operating state of the motor generators MG1 and MG2, the regenerative braking force selectively generated via the respective drive systems (therefore, the motor generators MG1 and MG2 become regenerative braking devices) is used. The wheel cylinders 40 and 42 are controlled by the electronic control unit 38 according to the master cylinder pressure of the master cylinder operated in response to the depression of the brake pedal 46 by the driver or in various vehicle motion control. In response to the required deceleration or braking force, a brake pressure is applied from a hydraulic circuit 44 including an oil reservoir, an oil pump, various valves and the like (not shown). The friction braking force generated at the wheels 30 and 32 is such that the brake pressure extends the wheel cylinder, whereby a brake pad (friction element) (not shown) is pressed against the brake shoe inside the wheel. Generated by. On the other hand, the regenerative braking force is a power generation in which the motor generators MG1 and MG2 absorb the rotational energy of the respective rotating shafts in response to the depression of the brake pedal 46 or the vehicle motion control command under the control of the electronic control unit 38. Generated by setting inverter 34 to operate with the machine.

  The electronic control unit 38 may include a microcomputer and drive circuit having a CPU, a ROM, a RAM, and an input / output port device which are connected to each other by a bidirectional common bus. The electronic control unit 38 is supplied with signals for giving information on their operating states from the internal combustion engine 10, the motor generator MG1 that mainly operates as a generator, the battery 36, and the brake pedal 46, and also the vehicle speed and other vehicles. Various signals I relating to the operating state are input. The characteristic configuration and operation of the braking control device of the present invention are realized by the electronic control device 38.

  FIG. 1B shows the configuration of the electronic control device 38 according to the braking control of the present invention in the form of a block diagram. The electronic control unit 38 includes a hybrid system calculator and a brake system calculator as part of its functional configuration. The hybrid system computing unit calculates a regenerative execution amount that can be currently executed based on information on the battery charge level, the battery temperature, and the vehicle speed, and further predicts a maximum regenerative braking force that is converted into a unit of force. On the other hand, the brake system calculator first calculates a required braking force to be generated in the entire braking system of the vehicle based on the brake pedal operation information or a control command from any vehicle motion control (note that the required control force is The power may be obtained as calculated by another braking force control device or the like. Then, from the values of the required braking force and the maximum regenerative braking force, the target regenerative braking force according to a predetermined scheme, the control command to the inverter 34 corresponding thereto, and the friction braking device are realized. A target friction braking force obtained by converting the power target friction braking amount into a unit of force and a target brake pressure (control amount of the friction braking device) to be supplied to the wheel cylinder corresponding to the target friction braking force are determined. Then, as shown in the figure, corresponding control commands are sent to the hydraulic circuit 44 and the inverter 34, respectively, to adjust each braking force.

  When determining the brake pressure from the target friction braking force, the braking control device of the present invention further builds up the friction element during friction braking, that is, friction braking, as will be described in detail below. In order to compensate for the variation of the friction coefficient of the friction element depending on the history of the change in the amount, the target brake pressure actually applied to the wheel cylinder according to the braking energy absorbed by the friction braking from the start of the friction braking operation. Size correction is performed. In order to perform such correction, the brake system calculator stores a map or conversion table that gives a correction coefficient as a function of braking energy absorbed by friction braking from the start of friction braking operation. The correction coefficient value can be derived. Further, the braking energy may be obtained by calculating or estimating the friction braking amount based on the brake pressure applied to the wheel cylinder and the vehicle body speed or the wheel speed by any method for those skilled in the art. . Alternatively, since the braking energy absorbed by friction braking is considered to correspond to the increment of internal energy accumulated in the friction element, the amount of change in the temperature of the friction element may be referred to as an index. The temperature of the friction element may be measured by providing an appropriate temperature sensor for the friction element. In that case, the detected temperature value of the friction element is further input to the brake system calculator.

Correction of control amount of friction braking device FIG. 2A shows a case where the temperature difference of the pad is adopted as an index of braking energy absorbed by friction braking during friction braking for a typical brake pad (friction element). The change in the coefficient of friction is shown. As understood from the figure, the friction coefficient of the brake pad fluctuates with the braking energy absorbed by the friction braking during the friction braking (build-up phenomenon). In the braking control device of the present invention, the target friction is compensated for such a variation in the friction coefficient so that the target friction braking amount determined based on the required braking force and the regenerative braking amount is achieved on the wheel. By multiplying the target brake pressure (control amount of the friction braking device) calculated from the braking force by using a predetermined reference value of the friction coefficient of the brake pad by a correction coefficient as illustrated in FIG. The target brake pressure is corrected. As shown in the figure, the correction coefficient changes in a phase opposite to the change of the friction coefficient with respect to the braking energy absorbed by the friction braking or the temperature change of the pad, thereby compensating for the fluctuation of the friction coefficient.

  FIG. 3A shows a generated braking force, a braking pressure, and a correction amount of a braking pressure (correction) when a certain required braking force is generated by coordinating regenerative braking and friction braking with the braking control device of the present invention. It shows an example of the change over time of the difference in target brake pressure before and after correction calculation by a coefficient. Referring to the upper and middle stages of FIG. 3 (A), when the generation of a certain required braking force is instructed, the braking pressure is first increased during a predetermined period (from t1) to t1. Only friction braking is performed. When the time reaches t1, regenerative braking starts to be activated, and at the same time, switching from friction braking to regenerative braking that reduces friction braking is performed. In the illustrated example, since the magnitude of the required braking force is achieved only by regenerative braking, when the regenerative braking force reaches the required braking force (time t2), the friction braking is temporarily stopped and only the regenerative braking is activated. Become. However, when the vehicle speed is reduced to a predetermined value or less by braking (time point t3), the regenerative braking force is gradually reduced and controlled to stop, and at the same time, the friction braking operation is started again, and the switching from regenerative braking to friction braking is executed. Is done.

  During the series of braking operations, it is desirable that the generated braking force be equal to the required braking force when either regenerative braking or friction braking is operating. However, as shown by the dotted line in the figure, during the period in which friction braking is being performed, the friction coefficient of the brake pad varies due to the build-up phenomenon during the friction braking operation, and the amount of friction braking varies. As a result, the braking force generated in the vehicle does not match the required braking force. Therefore, the control amount corrected by multiplying the control amount of the friction braking device directly obtained from the target friction braking force by the correction coefficient as illustrated in FIG. The brake pressure is corrected as shown in the lower part of FIG. 3A so that the braking force matches the required braking force.

  In the example of FIG. 3 (A), the correction of the brake pressure may be performed only after switching to friction braking is performed after only regenerative braking is activated. The important thing is that when only regenerative braking is executed, friction braking is temporarily stopped. Therefore, in the calculation of the correction coefficient, the accumulated amount of braking energy before the friction braking is stopped is not taken into consideration. That's what it means.

  FIG. 3B shows another example of the time change of the generated braking force, the brake pressure, and the correction amount of the brake pressure when a certain required braking force is generated by the braking control device of the present invention. . If the required braking force is not achieved even when the regenerative braking is performed to the maximum extent possible as described in the upper and middle stages of the figure, the friction braking is performed with the required braking force and the regenerative braking even during the regenerative braking operation. It is operated in a manner that compensates for the difference from the braking force. In the case of this example, since the friction braking is continuously operated from the start of the braking, the braking energy absorbed by the friction braking from the start of the operation is continuously increased, and the amount of correction of the brake pressure is changed correspondingly (( FIG. 3 (B) bottom). Even in the control mode in which the correction of the brake pressure is performed only after switching from regenerative braking to friction braking, the correction coefficient is determined by the energy accumulated in the brake pad after the start of friction braking. Therefore, in such a control mode, when the friction braking is not stopped after the start of the regenerative braking, the correction amount is a value determined in consideration of all accumulated energy from before the start of the regenerative braking to after the stop. (FIG. 3 (B) lower dashed line).

Operation Figure 4 of the device is a representation of a control process of correction to compensate for at buildup phenomenon braking system computing unit of the brake control apparatus of the present invention in the form of a flow chart. The control process of FIG. 4 is repeated at a predetermined cycle during the driving of the vehicle. Various parameters necessary for control are read in a timely manner. In the following description, the regenerative execution amount (regenerative braking amount) and the friction braking amount are the regenerative braking force and the friction braking force obtained by dividing the respective amounts by the vehicle speed or the wheel speed and converting them into units of force. However, it should be understood by those skilled in the art that the same explanation can be made using the regeneration execution amount and the friction braking amount.

  When the control is started, first, it is determined whether or not there is a braking request (step 10), and when there is a braking request, based on the control instruction from the brake pedal operation information or the motion control of any vehicle, A required braking force to be generated in the entire braking system of the vehicle is calculated (step 20). As already described, the required braking force may be obtained by a value calculated by another control device. Next, values of the target regenerative braking force and the target friction braking force are calculated from the values of the required braking force and the maximum regenerative braking force given from the hybrid system computing unit (step 30).

In calculating the values of the target regenerative braking force and the target friction braking force, friction braking is used as a supplement to regenerative braking. Therefore, first, the target regenerative braking force is set according to a predetermined scheme, and the target friction braking force is ,
Target friction braking force = required braking force−target regenerative braking force. In the initial stage of braking, since regenerative braking is not executed, the target regenerative braking force is set to 0.
Target friction braking force = required braking force. When the control cycle is repeated and a predetermined condition is satisfied, the target regenerative braking force> 0,
When the required braking force ≤ maximum regenerative braking force,
Since the target regenerative braking force = required braking force is set, the target friction braking force = 0, and in this case, the operation of the friction braking device is stopped. Further, when a predetermined condition is established during regenerative braking, for example, when the vehicle speed becomes a predetermined value or less, the regenerative braking is gradually reduced to be stopped,
In order to satisfy the required braking force = regenerative braking force + target friction braking force, the operation is started if the friction braking device is stopped, or the target friction braking force is increased if the friction braking device is already operating. Become. Thus, when the target friction braking force is calculated, the target brake pressure is calculated using a predetermined reference value of the friction coefficient of the brake pad (step 40).

Thus, when the target friction braking force or the target brake pressure is not 0 (step 50), the braking energy absorbed by the friction braking from the start of the friction braking is estimated (step 60). The braking energy absorbed by the friction braking from the start of the friction braking may be estimated by various methods such as integrating the amount of friction braking estimated from the vehicle speed and the friction force generated by the friction braking device, for example. However, for example, when the difference in brake pad temperature is used as an index of braking energy, the difference between the brake pad temperature at the start of friction braking and the current brake pad temperature is calculated. The brake pad temperature at the start of friction braking should always record the latest brake pad temperature Ts in the cycle when there is no braking request or when the target friction braking force or target brake pressure = 0. (Step 15 or 55 described later). When the target friction braking force or the target brake pressure is no longer 0, in step 60, the temperature Ts recorded in step 15 or 55 of the immediately preceding cycle is referred to as the brake pad temperature at the start of friction braking. Is done. Thus, when the difference between the braking energy absorbed by the friction braking or the temperature of the brake pad from the start of the friction braking is calculated, the correction coefficient is obtained from the map illustrated in FIG. 2B (step 70). The target brake pressure is
Target brake pressure (after correction) = Target brake pressure (before correction) x (Correction coefficient)
(Step 80), and a control command is sent to the hydraulic circuit to generate a corrected target brake pressure in the wheel cylinder (step 90).

  If there is no braking request in step 10, the braking device is not operated, but the latest brake pad temperature Ts is acquired and stored for each cycle in order to correct the target brake pressure. Good (step 15). Further, in step 50, when the target friction braking force or the target brake pressure = 0, the friction braking is not executed. Therefore, only the regenerative braking is operated, but for the correction of the target brake pressure, The latest brake pad temperature Ts may be acquired and stored for each cycle (step 55). When the estimated value of the friction braking amount is integrated to calculate the braking energy absorbed by the friction braking, the integrated value is reset in steps 15 and 55.

  In the above control processing, when the control amount correction to the friction braking device is performed only at the time of switching from regenerative braking to friction braking, after step 60, regenerative braking stop processing, that is, regenerative braking is performed. A step 65 for determining whether or not the execution of the gradual reduction process is started may be inserted (indicated by a broken line in FIG. 4). If the regenerative braking gradual reduction process is not after the start of execution, steps 70 and 80 are bypassed, and a control command for achieving the target brake pressure without sending the above correction is sent to the hydraulic circuit. On the other hand, if the regenerative braking gradually decreasing process is started, the target brake pressure is corrected and sent as a control command as described above. It should be understood that if not after the start of the regenerative braking stop process, unless the target friction braking force or the target brake pressure becomes zero, the brake pad temperature Ts at the start of friction braking for calculating the correction coefficient is calculated. Therefore, when the target brake pressure is corrected after the start of the regenerative braking stop process, the friction braking amount accumulated from the start of the renewal braking or friction braking is not reset. That is, the correction coefficient is determined based on the absorbed braking energy.

  Thus, the control amount to the friction braking device is corrected by using the correction coefficient obtained as a function of the absorbed braking energy from the start of friction braking, thereby compensating for the variation of the friction coefficient. Therefore, the friction braking force actually generated by the friction device is corrected to match the target friction braking force, and the friction braking amount actually realized on the wheel is controlled to match the target friction braking amount. Since the braking amount of the entire vehicle is adapted to the required braking force and the unexpected variation of the friction braking amount is suppressed, the unstable variation of the braking force is suppressed.

  While the present invention has been described in detail with respect to one embodiment thereof, it will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention.

FIG. 1A is a schematic diagram of a vehicle on which a preferred embodiment of the braking control device according to the present invention is mounted, and FIG. 1B is an electronic control that realizes the preferred embodiment of the braking control device according to the present invention. It is a control block diagram of an apparatus. FIG. 2A is a diagram showing a relationship between a friction coefficient of a brake pad of a friction braking device provided on a wheel and braking energy absorbed by friction during friction braking (increase in temperature of the brake pad). FIG. 2B is a map of the correction coefficient for the target brake pressure obtained as a function of the brake pad temperature difference. It should be noted that correction is not necessary in the region where the pad temperature increment is small (region not illustrated in the figure), and thus correction may not be performed (that is, correction coefficient = 1). FIG. 3 shows the generated braking force, the brake pressure, and the correction amount of the brake pressure when the regenerative braking and the friction braking are coordinated to generate a certain required braking force (the difference between the target brake pressure before and after the correction calculation by the correction coefficient). It is a figure which shows the example of the time change of (). (A) is an example in which a period in which only regenerative braking is activated occurs, and (B) is an example in which friction braking is continued even during a period in which regenerative braking is activated. FIG. 4 shows the regenerative / friction braking cooperative control process in the braking control apparatus according to the present invention in the form of a flowchart.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 12 ... Output shaft (crankshaft) of an internal combustion engine
14 ... Driving force distribution device 16 ... First motor generator (MG1)
18 ... Second motor generator (MG2)
20, 22 ... Gear 24 ... Differential gear device 26, 28 ... Axle 30, 32 ... Wheel 34 ... Inverter 36 ... Battery 38 ... Electronic control device 40, 42 ... Friction braking device (wheel cylinder)
44 ... Hydraulic circuit 46 ... Brake pedal

Claims (5)

A braking control device that performs cooperative control of regenerative braking and friction braking in a vehicle having a regenerative braking device and a friction braking device, and is calculated from a required braking force and a regenerative execution amount in the regenerative braking device. Means for determining a control amount of the friction braking device based on a target friction braking amount, and when the operation of the friction braking device is started, the braking absorbed by the friction braking in the current operation from the start of the operation The target friction braking amount and the braking amount realized by the friction braking device coincide with each other by compensating for the variation of the braking amount realized by the friction braking device due to the change in the friction coefficient of the friction element based on energy. Means for correcting the control amount of the friction braking device.   The braking control device according to claim 1, wherein when the reduction of the regeneration execution amount for the stop processing of the regenerative braking device is started, the braking is absorbed by friction braking from the start of the operation of the friction braking device. A device for correcting a control amount of the friction braking device based on braking energy.   The braking control device according to claim 1, wherein the control amount of the friction braking device is based on braking energy absorbed by friction braking since the friction braking device was started before the regenerative braking device was started. A device characterized by correcting the above.   The braking control device according to claim 1, wherein the braking energy absorbed by the friction braking is represented by a change amount of the temperature of the friction element from the start of operation of the friction braking device, and the control amount of the friction braking device is The correction is performed based on the amount of change in temperature of the friction element from the start of operation of the friction braking device. 2. The braking control device according to claim 1, wherein the correction of the control amount of the friction braking device compensates for a change in a friction coefficient that is a function of braking energy absorbed by the friction braking from the start of operation of the friction braking device. A device characterized by being made.

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