Brake force control device

Abstract

Brake force control device mounted on a vehicle, comprising a first actuator unit (200) and a second actuator unit (300) designed to generate braking force, wherein the brake force control device is designed to control the braking force to be generated by the second actuator unit (300) when the travel of an accelerator pedal changes from non-zero to zero and the vehicle is brought into a coasting state, since the travel of a brake pedal is zero, wherein the brake force control device comprises a target jerk calculation unit (101), a first estimation unit (102) and a control unit (104), wherein the target jerk calculation unit (101) is designed to calculate a target jerk which is a jerk generation target value when the braking force is generated in the vehicle, wherein the jerk is negative if a vehicle travel direction is defined as a positive direction, and wherein the first estimating unit (102) is designed to determine whether a given factor is currently occurring or not which increases the braking force generated by the first actuator unit (200), and, if it determines that the given factor is occurring, to estimate an increase in the braking force due to the given factor, and wherein the control unit (104) is designed to determine, based on a calculation result of the target jerk calculation unit (101), that the sum of the negative jerk generated when the second actuator unit (300) generates the braking force and the jerk generated by the first actuator unit (200) when the specified factor does not increase the braking force, will be the target jerk. the brake force control device further a second estimation unit (103) designed to determine whether the specified factor occurs within a specified time period of a given time or not, even if the specified factor does not currently occur in the vehicle, and, if this determines that the specified factor occurs, to estimate an increase in braking force due to the specified factor, and wherein If the specified factor is currently occurring or occurs within the specified time period and the increase in braking force due to the specified factor is greater than a specified value, the control unit (104) corrects the specified negative jerk based on an estimate result of the first estimation unit (102) or the second estimation unit (103) so that an absolute value of the negative jerk becomes smaller, the first actuator unit (200) comprises a gearbox and a lock-up clutch, the specified factor includes an engagement of the bridging clutch, and the first estimation unit (102) and the second estimation unit (103) estimate an increase in braking force due to the engagement of the lock-up clutch based on a difference between a speed of an engine and a lock-up clutch-side speed of the transmission and / or an oil temperature of the lock-up clutch, characterized by the fact that The second estimation unit (103) determines, based on the current speed, current acceleration and current gear change speed of the vehicle, whether the engagement of the lock-up clutch will occur within a predetermined time period of a given time or not.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a braking force control device mounted on a vehicle for controlling a braking force of the vehicle. 2. Description of related technology

[0002] In the field of vehicles, various techniques have been proposed to improve ride comfort and operating feel. For example, JP H10-280990 A discloses fuel-cut control. When fuel-cutting is prohibited during vehicle braking to prevent a catalyst from deteriorating under high-temperature conditions, the fuel-cut control compensates for braking force using an alternator, air conditioner, brake, gearshift, or the like to obtain a desired braking force. JP 2006-297994 A discloses an integrated vehicle control unit. The integrated vehicle control unit distributes specific control targets to a drive system and a control system based on a user's operation path in accordance with a charging ratio.The integrated vehicle control unit also transmits the control targets to a stabilization system prior to distribution to cause the stabilization system to perform a correction process for the purpose of eliminating the need for the stabilization system to synchronize values ​​of the distributed control targets, reducing delay, and improving responsiveness to operation. DE 10 2015 221 156 B4 discloses a brake force control device having the features of the preamble of claim 1. DE 10 2006 030 528 A1, DE 103 16 986 A1, and DE 103 16 066 A1 show further brake force and transmission control devices according to the prior art. SUMMARY OF THE INVENTION

[0003] For appropriate driving comfort and operating feel in a vehicle, it is desirable to provide a user with an appropriate deceleration feeling when, for example, the user stops operating an accelerator pedal and thereby the vehicle changes to a coasting state in which neither the accelerator pedal nor a brake pedal is operated.

[0004] Factors of appropriate deceleration feeling include decreasing negative acceleration when the vehicle's direction of travel is defined as a positive direction (increasing an absolute value of acceleration in a deceleration direction of the vehicle), and decreasing negative jerk when the vehicle's direction of travel is defined as a positive direction (rapidly increasing the absolute value of acceleration in the deceleration direction of the vehicle). Accordingly, the appropriate deceleration feeling can be achieved by decreasing the negative jerk. A jerk j is defined as a third derivative of position x with respect to time t (j = d 3 × / dt 3 ). The jerk J, for example, is in the unit [meters per second per second per second (m / s 3 )]. As is clear from the definition, jerk is the rate of change of acceleration.

[0005] In the coasting state, negative jerk is caused by a decrease in driving force (increase in braking force) generated in an engine or transmission. However, by causing the brake or the like to generate braking force, the negative jerk can be further reduced and the deceleration feeling can be improved as described above.

[0006] However, when gear shifting by the transmission or the like increases the braking force while the brake generates negative jerk, the negative acceleration and negative jerk generated in the vehicle decrease beyond a reasonable range, which may rather deteriorate the ride comfort and operating feel.

[0007] The invention has been made in view of the above-mentioned problem, and it is an object of the invention to provide a braking force control device capable of achieving appropriate driving comfort and operating feeling while the vehicle is in a coasting state.

[0008] To solve the problem, the present invention provides a brake force control device having the features of claim 1. Advantageous further developments are set forth in the subclaims.

[0009] The invention can provide the braking force control device capable of achieving appropriate ride comfort and operating feeling for a vehicle in a coasting state. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features, advantages and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like reference numerals designate like elements and wherein: Fig. 1 is a block diagram showing a braking force control device according to an embodiment of the invention; Fig. 2 shows a process according to the embodiment of the invention; Fig. 3 shows an example of a map of a target jerk according to the embodiment of the invention; Fig. 4 shows an example of the target jerk map according to the embodiment of the invention; Fig. 5 shows an example of the target jerk map according to the embodiment of the invention; Fig. 6 shows an example of the characteristics of a braking force increase according to the embodiment of the invention; Fig. 7 shows another example of the characteristics of the braking force increase according to the embodiment of the invention; Fig. 8 shows an example of the characteristics of the braking force increase according to the embodiment of the invention; Fig. 9 shows an example of the characteristics of the braking force increase according to the embodiment of the invention; Fig. 10 shows an example of control characteristics of a transmission according to the embodiment of the invention; and Fig. 11 shows an example of a controller according to the embodiment of the invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0011] The braking force control device according to the invention controls a jerk generated in a brake or the like to achieve a deceleration feeling presumed to be expected by a user in a coasting state of a vehicle, thereby achieving appropriate ride comfort and operating feel of the vehicle. In the invention, when a braking force increases due to gear shifting of a transmission or the like in the coasting state, the jerk generated in the brake or the like is reduced to reduce fluctuation in a deceleration feeling and prevent ride comfort and operating feel from deteriorating. Embodiment

[0012] An embodiment of the invention will be described in detail below with reference to the drawings. Parameters such as speed, acceleration, driving force, and jerk are expressed by signed values ​​that are positive in the direction in which a vehicle is traveling. Where a negative driving force is referred to as braking force, the braking force is expressed as an absolute value. Design

[0013] Fig. 1 shows the configuration of a braking force control device 100 and peripheral devices according to an embodiment of the invention. The braking force control device 100 is mounted on a vehicle. A first actuator unit 200 includes, for example, an engine and a transmission. A second actuator unit 300 includes, for example, a brake. Although the first actuator unit 200 may generate braking force relatively consistently in a coasting state, the braking force may increase independently of the control of the braking force control device 100 due to a predetermined factor caused by control of other control systems of the vehicle, such as gear changes in the transmission. The second actuator unit 300 includes one or more predetermined actuators for generating the braking force.To provide an appropriate deceleration feeling for a user in the coasting state, the braking force control device 100 may control the second actuator unit 300 to generate braking force to offset the braking force generated by the first actuator unit 200. The first actuator unit 200 and the second actuator unit 300 may each comprise any type and any number of actuators, as long as the actuators have the characteristics described above.

[0014] The first actuator unit 200 and the second actuator unit 300 each include a control unit configured to perform various processes with respect to the actuators included in each of the actuator units. A total sum of the driving force generated by the respective actuators included in the first actuator unit 200 and the second actuator unit 300 serves as the total driving force for driving the vehicle. The acceleration and jerk of the vehicle both fluctuate in accordance with the sum of the braking force generated by the respective actuators and a sum of change rates of the braking force. When the respective actuators generate braking force, the actuators contribute to the acceleration and jerk of the vehicle. This contribution is expressed as the actuators that generate the acceleration and jerk of the vehicle.When the vehicle travels along an uphill road or a downhill road, a signed gravity component along the direction of travel is further added to the total driving force.

[0015] The braking force control device 100 includes a target jerk calculation unit 101, a first estimation unit 102, a second estimation unit 103, and a control unit 104.

[0016] In order to generate braking force in the coasting state, the target jerk calculation unit 101 calculates a target jerk as a jerk generation target value, which is negative when the traveling direction of the vehicle is defined as a positive direction.

[0017] The first estimation unit 102 determines whether or not a predetermined factor that increases the braking force generated by the first actuator unit 200 is currently occurring. If it determines that the predetermined factor is occurring, the first estimation unit 102 estimates an increase in the braking force.

[0018] The second estimation unit 103 determines whether the predetermined factor that increases the braking force generated by the first actuator unit 200 will occur within a predetermined period of time from the present time, i.e., in the near future, even though the predetermined factor does not currently occur. If it determines that the predetermined factor will occur in the near future, the second estimation unit 103 estimates an increase in the braking force.

[0019] The control unit 104 determines a negative jerk to be generated by the second actuator unit 300 based on a calculation result of the target jerk calculation unit 101. In the case where the predetermined factor is currently occurring and the case where the predetermined factor may occur within a predetermined period of time from the present time even though it is not currently occurring, and the increase in braking force is greater than a predetermined value, the control unit 104 corrects the determined negative jerk so that an absolute value of the negative jerk becomes smaller based on an estimation result of the first estimation unit 102 or the second estimation unit 103. The control unit 104 instructs the second actuator unit 300 to generate the thus calculated negative jerk. The control unit 104 also executes and controls other various types of processes of the braking force control device 100. process

[0020] Fig. 2 is a flowchart illustrating an example of a process executed by the braking force control device 100. Referring to Fig. 2 describes an example of acceleration control by the braking force control device 100. The process is executed in the state where the vehicle is powered on to enable driving by user operation.

[0021] (Step S101): The control unit 104 continuously acquires the amount of accelerator pedal operation by a user, which is detected by an accelerator pedal sensor included in the vehicle, and the amount of brake pedal operation by the user, which is detected by the brake pedal sensor. Based on the acquired accelerator pedal and brake pedal operation amounts, the control unit 104 detects a transition from the state where the user is operating the accelerator pedal (the operation amount is not zero) to the state where the user is not operating the accelerator pedal (the operation amount is zero) and the user is not operating the brake pedal (the operation amount is zero). As a result, the control unit 104 detects that the vehicle is in a coasting state. If the control unit 104 detects the coasting state, the process proceeds to step S102.If the control unit 104 does not detect the coasting state, the control unit 104 repeats step S101 and waits for the vehicle to enter the coasting state. In this step, the control unit 104 typically detects the coasting state established when the accelerator pedal operation is released as described above. However, the control unit 104 may also detect the coasting state established when the brake pedal operation is released.

[0022] (Step S102): The target jerk calculation unit 101 calculates a target jerk, which is a target value of the negative jerk to be generated in the vehicle in the coasting state. It is assumed that the target jerk is capable of providing the user with an appropriate deceleration feeling when the coasting state is established. The target jerk is calculated by a predetermined method. The target jerk calculation unit 101 may calculate the target jerk by obtaining the information necessary for calculating the target jerk from sensors or other devices, or may obtain the target jerk calculated by other devices.

[0023] Examples of the target jerk calculation method are described. In each example, a map is used in which a target acceleration is predetermined for each vehicle speed. Fig. 3, Fig. 4 and Fig. 5 shows schematically the characteristic maps for the respective examples.

[0024] In a Fig. In the example shown in Figure 3, the target jerk becomes smaller as the vehicle speed increases. Specific values ​​can be determined based on an evaluation conducted through an experiment or the like.

[0025] In a Fig. In the example shown in Figure 4, drive modes that reflect user-specified driving characteristics and the vehicle's speed are taken into account. If the drive mode is an Eco mode, which requires low-fuel consumption driving, the target jerk is set to be greater than the target jerk at the same speed in a normal mode, which is a different drive mode than the Eco mode. For example, the Fig. 3 can be used in normal mode. The map shown in Fig. 4 shown map in the Eco mode can be obtained by multiplying the value of the target jerk according to the Fig. 3 with a positive coefficient α less than 1. Similarly, when the drive mode is a sport mode that prescribes sporty driving, the target jerk may be set smaller than that in the normal mode at the same speed.

[0026] In a Fig. In the example shown in Figure 5, a road surface gradient is taken into account in addition to the vehicle speed. If the road surface is a downhill road, the target jerk is set smaller than that for a flat road at the same speed. For example, the Fig. 3 can be used for the case of the flat road and the map for the sloping road, which is shown in Fig. 5 can be calculated by multiplying the value of the target jerk according to the Fig. 3 with a coefficient β greater than 1.

[0027] If the road surface is an uphill road, the target jerk is set larger than that of the flat road at the same speed. For example, in Fig. 3 can be used in the case of the flat road and the map in the case of the ascending road can be obtained by multiplying the value of the target jerk according to the map in Fig. 3 with a coefficient γ less than 1.

[0028] The target jerk can also be calculated based on both the drive mode and the road surface gradient. For example, the Fig. 3 can be used in the case of the flat road and the normal mode, and a map in the case of the downhill road and the Eco mode can be obtained by multiplying the value of the target jerk according to the value shown in Fig. 3 can be prepared with the coefficient α and the coefficient β. Similarly, a map for the uphill road and the Eco mode can be prepared by multiplying the value of the target jerk according to the map shown in Fig. 3, with the coefficient α and the coefficient γ.

[0029] To calculate the target jerk, various types of information output from various sensors and an electronic control unit (ECU) included in the vehicle are used. In the above examples, the calculation method of the target jerk, which uses the speed of the vehicle and further uses information indicating the drive mode specified by the user or the gradient of the road surface, is not particularly limited. A basic map can be prepared as described above, and the target jerk can be calculated by multiplying the target jerk by various coefficients in accordance with the state of the vehicle or its periphery, or by using maps prepared individually for respective states in advance.Alternatively, if the presence of another vehicle at a given distance in front of the vehicle is detected by, for example, a camera and radar, the information indicating the presence can be obtained to set the target jerk smaller than in the case without the presence of another vehicle at the same speed.

[0030] (Step S103): The control unit 104 determines whether or not to cause the second actuator unit 300 to generate jerk. First, the control unit 104 obtains from the first actuator unit 200 a negative jerk j1 that the first actuator unit 200 can currently generate. For example, if the first actuator unit 200 includes an engine and a transmission, the control unit of the first actuator unit 200 may calculate the jerk j1 based on, for example, an engine throttle opening (zero in the coasting state) and a current gear stage of the transmission. The jerk j1 is the assumed jerk when the operating state of the first actuator unit 200, such as the gear stage, is maintained unchanged from the current state.

[0031] Next, the control unit 104 compares the jerk j1 with the target jerk J calculated in step S102 to determine whether or not to cause the second actuator unit 300 to generate a negative jerk. If the jerk j1 is equal to or less than the target jerk J, the first actuator unit 200 generates sufficient negative jerk. Accordingly, the control unit 104 determines to prohibit the second actuator unit 300 from generating the negative jerk.

[0032] Then, the process proceeds to step S101, where the control unit 104 waits until the coasting state restarts.

[0033] If jerk j1 is greater than target jerk J, the negative jerk to be generated by first actuator unit 200 is less than the target jerk. Accordingly, control unit 104 determines to cause second actuator unit 300 to generate negative jerk. The process proceeds to step S104.

[0034] (Step S104): The control unit 104 determines whether or not a predetermined factor that increases the braking force generated by the first actuator unit 200 is currently occurring. For example, when the first actuator unit 200 includes a transmission, examples of the predetermined factor may include gear shifts under the control of other control systems and a reduction in output torque caused by engagement of a lock-up clutch included in the transmission. For example, the control unit 104 may obtain information indicating whether or not such a predetermined factor is currently occurring from the control unit of the first actuator unit 200 and may use the information for the determination. If the control unit 104 determines that the predetermined factor is currently occurring, the process proceeds to step S105. If the control unit 104 determines that the predetermined factor is not occurring, the process proceeds to step S110.

[0035] (Step S105): The control unit 104 estimates an increment D of the braking force generated by the first actuator unit 200. Examples of an estimation method are described below.

[0036] If the first actuator unit 200 comprises a transmission and the predetermined factor comprises gear changes of the transmission, the increase D of the braking force can be calculated, for example, based on a gear ratio or an oil temperature of the transmission. Fig. 6 schematically shows a map indicating the relationship between the gear ratio of the transmission and the increase in braking force. The map indicates that as the current gear ratio is higher, the temporary increase in braking force in a transient gear shift state is greater. Referring to such a map, the control unit 104 can estimate the increase D corresponding to the gear ratio at a current gear stage. Fig. Figure 7 schematically shows a map indicating the relationship between the transmission oil temperature and the increase in braking force. The map indicates that when the current transmission oil temperature is higher, the temporary increase in braking force in the gear shift transition state is smaller. Control unit 104 can estimate the increase D corresponding to the current transmission oil temperature by referring to such a map.

[0037] If the first actuator unit 200 includes a lock-up clutch and the predetermined factor includes engagement of the lock-up clutch, the increase D of the braking force may be calculated, for example, based on a difference between the speed of the engine and the lock-up clutch-side speed of the transmission and the oil temperature of the lock-up clutch. Fig. Figure 8 schematically shows a map showing the relationship between transmission speed and the increase in braking force. The lock-up clutch is typically included in the transmission. The lock-up clutch is released at the beginning of a gear shift. Then, the lock-up clutch-side speed of the transmission increases due to a gear shift, so that the engine-side speed becomes lower than the lock-up clutch-side speed of the transmission. When the engine-side speed increases to a predetermined allowable range from this state, the lock-up clutch engages again. The map shows that as a speed difference at the engagement time is larger, a temporary increase in braking force at the engagement time is larger.The control unit 104 may estimate the increase D corresponding to the estimated speed difference at the time of intervention by referring to such a map. Fig. 9 schematically shows a map indicating the relationship between the lock-up clutch oil temperature and the increase in braking force. The map indicates that as the current lock-up clutch oil temperature is higher, the temporary increase in braking force at the time of engagement is smaller. Control unit 104 can estimate the increase D corresponding to the current lock-up clutch oil temperature by referring to such a map.

[0038] To estimate the gain D, the control unit 104 may correctly obtain information, including a current gear stage, speed, and each oil temperature of the transmission, from the control unit of the first actuator unit 200. As the above-mentioned maps, those prepared in advance through experiments or the like may be used. The control unit 104 may combine the above estimation methods. More specifically, the control unit 104 may estimate the gain D based on a map defining a gain corresponding to two or more combinations of the gear stage, speed, and each oil temperature. The estimation methods of the gain D are not limited to these. Appropriate estimation methods may be adopted in accordance with the types and characteristics of the actuators of the first actuator unit 200.

[0039] (Step S106): The control unit 104 compares the increase D of the braking force estimated at step S105 with predetermined threshold values ​​d1(>0), d2(>d1). If the increase D is equal to or less than the threshold value d1, the process proceeds to step S107. If the increase D is greater than the threshold value d1 and equal to or less than the threshold value d2, the process proceeds to step S108. If the increase D is greater than the threshold value d2, the process proceeds to step S109.

[0040] (Step S107): The control unit 104 determines a negative jerk to be generated by the second actuator unit 300. In this step, for example, a jerk j2 to be generated by the second actuator unit 300 may be set to a difference (J - j1) between the target jerk J calculated in step S102 and the jerk j1 that can currently be generated by the first actuator unit 200, the jerk j1 being obtained in step S103. The control unit 104 instructs the second actuator unit 300 to generate the jerk j2 (= J - j1). The control unit 104 may calculate the value of a driving force that gradually decreases based on the jerk j2 and may sequentially display the value to the second actuator unit 300. The control unit of the second actuator unit 300 may cause the actuator to generate the displayed driving force. Alternatively, the control unit 104 of the second actuator unit 300 may indicate the jerk j2.The control unit of the second actuator unit 300 may calculate the driving force that gradually decreases based on the indicated jerk j2 and may cause the actuator to generate the indicated jerk j2. In this step, when an increase in the braking force due to the predetermined factor does not occur in the first actuator unit 200, a sum of the negative jerk j1 generated by the first actuator unit 200 and the negative jerk j2 generated by the second actuator unit 300 becomes equal to the target jerk J. This step is performed when an increase in the braking force generated by the first actuator unit 200 does not occur, or when the level of the increase is relatively small even if the increase occurs. Accordingly, the negative jerk and the negative acceleration generated in the vehicle fall within an appropriate range.Then, the process proceeds to step S101, where the control unit 104 waits until the coasting state restarts.

[0041] (Step S108): The control unit 104 determines a negative jerk to be generated by the second actuator unit 300. In this step, the jerk j2 to be generated by the second actuator unit 300 can be obtained, for example, by multiplying a value calculated as in step S107 by a positive coefficient δ less than one. The control unit 104 instructs the second actuator unit 300 to generate the jerk j2 (= δ × (J - j1). Thus, in this step, the negative jerk j2 generated by the second actuator unit 300 is corrected so that an absolute value of the negative jerk j2 becomes smaller (lower) than the negative jerk j2 obtained in step S107. This step is executed when the degree of increase in the braking force generated by the first actuator unit 200 is relatively average.When the correction is performed, the negative acceleration or jerk generated in the vehicle is less likely to become smaller than a reasonable range, and deterioration of ride comfort or operating feel can be limited. Then, the process proceeds to step S101, where the control unit 104 waits until the coasting state restarts.

[0042] (Step S109): The control unit 104 prohibits the second actuator unit 300 from generating negative jerk regardless of the determination of step S103. This step is executed when the degree of increase in the braking force generated by the first actuator unit 200 is relatively large. Since the second actuator unit 300 is prohibited from generating negative jerk, the negative acceleration or negative jerk generated in the vehicle is less likely to become smaller than the appropriate range, and deterioration of ride comfort or operating feel can be limited. Then, the process proceeds to step S101, where the control unit 104 waits until the coasting state restarts.

[0043] (Step S110): The control unit 104 determines whether or not the predetermined factor occurs within a predetermined period of time from the current time. Examples of the determination method are described below.

[0044] A description will be given of the method for determining whether or not a gear shift of the transmission, which is the predetermined factor, occurs within a predetermined period of time in the case where the first actuator unit 200 includes the transmission. The control unit 104 may refer to a map indicating the characteristics of a transmission control of the transmission performed by another control system. Fig. 10 shows an example of the characteristic map. Fig. According to the map shown in Figure 10, the gear stage of the transmission is determined based on the vehicle speed and the throttle opening. During vehicle acceleration, when the vehicle speed increases to the speed corresponding to a current throttle opening in a speed change line shown by a solid line in the map, an upshift begins. During vehicle deceleration, when the vehicle speed decreases to the speed corresponding to a current throttle opening in a speed change line shown by a dotted line in the map, a downshift begins. Since the vehicle is in a coasting state, the throttle opening is zero. Therefore, the vehicle speed is maintained or basically decreases.The control unit 104 obtains a current gear ratio of the transmission and determines the speed at which a downshift from the zero-throttle-opening gear ratio begins. As a result, the control unit 104 can determine the speed at which a next gear change operation in the transmission begins. At the speed shown in . Fig. In the example shown in Figure 10, if the current gear stage is a third gear, the control unit 104 determines a speed V 32 corresponding to the zero throttle opening in a speed change line of a downshift from a third gear to a second gear as the speed at which the next gear change operation in the transmission begins.

[0045] The control unit 104 determines a current vehicle speed v and an acceleration a. The speed v can be determined by correctly obtaining the speed from a speed sensor included in the vehicle or other devices. The acceleration a can be determined, for example, by obtaining the vehicle speed v at a plurality of times and calculating a temporal rate of change thereof. Alternatively, the control unit 104 can obtain the acceleration from another device, such as an acceleration sensor included in the vehicle. The control unit 104 can determine the speed at which a next gear change operation in the transmission begins based on the current gear ratio as described above.Alternatively, after the speed v is determined, the speed at which a next gear change operation in the transmission begins can be determined based on the speed v and the above-mentioned map.

[0046] The control unit 104 predicts a time t1 until a next gear change in the transmission begins from a current time. Assuming that the acceleration a of the vehicle is constant, the control unit 104 predicts a time t1 until a next gear change in the transmission begins from a current time based on the current speed v, a speed V at which a next gear change in the transmission begins, and the acceleration a according to an expression (1) below: T1=(v−V) / |a|

[0047] If the predetermined time t1 is equal to or less than a predetermined time period, the control unit 104 may determine that the predetermined factor occurs within a predetermined time period of a present time. If the predetermined time t1 is greater than the predetermined time period, the control unit 104 may determine that the predetermined factor does not occur within a predetermined time period of a present time.

[0048] The method for determining whether or not lock-up clutch engagement occurs within a predetermined time period as the predetermined factor in the case where the first actuator unit 200 includes the lock-up clutch is the same as the method disclosed above. Since lock-up clutch engagement normally occurs with a gear shift of the transmission, a time t2 until the next lock-up clutch engagement occurs can be calculated as in the case of time t1. However, the lock-up clutch engagement occurs precisely at the time when the difference between the engine speed and the lock-up clutch-side speed of the transmission falls within an allowable range after a gear shift of the transmission.Accordingly, a time t2 may be a value obtained by adding a predetermined value to the time t1 or calculated using a map indicating engagement characteristics of the lock-up clutch, instead of the one shown in . Fig. 10. If the predetermined time t2 is equal to or less than a predetermined time period, the control unit 104 may determine that the predetermined factor occurs within a predetermined time period from a present time. If the predetermined time t2 is greater than the predetermined time period, the control unit 104 may determine that the predetermined factor does not occur within a predetermined time period from a present time.

[0049] If the control unit 104 determines through the above-mentioned method that the predetermined factor occurs within a predetermined time period from a present time, the process proceeds to step S111. If the control unit 104 determines that the predetermined factor does not occur within the predetermined time period, the process proceeds to step S107. The predetermined time period may preferably be set to a time period equal to the time period during which the coasting state is assumed to continue. The predetermined time period may be predetermined or may be changed in accordance with the user's driving characteristics.

[0050] (Step S111): The control unit 104 estimates an increment D' of the braking force generated by the first actuator unit 200. A method similar to that described in step S105 can be used as the estimation method.

[0051] (Step S112): The control unit 104 compares the increase D' in the braking force estimated at step S111 with predetermined limit values ​​d1' (> 0), d2' (> d1'). If the increase D' is equal to or less than the limit value d1', the process proceeds to step S107. If the increase D' is greater than the limit value d1' and equal to or less than the limit value d2', the process proceeds to step S108. If the increase D' is greater than the limit value d2', the process proceeds to step S109. The limit values ​​d1', d2' may be equal to or different from the limit values ​​d1, d2, respectively. For example, the limit values ​​d1', d2' may be set such that d1' > d1, d2' > d2. The second estimation unit 103 determines, based on prediction, whether or not the predetermined factor occurs within a predetermined period of time from a present time.Accordingly, the determination is less accurate than the determination by the first estimation unit 102, which relates to whether or not the predetermined factor currently occurs. Setting d1' > d1, d2' > d2 can reduce an insufficient deceleration feeling when a predetermination by the second estimation unit 103 does not occur, and can limit deterioration of ride comfort or operating feel.

[0052] If the accelerator pedal sensor and the brake pedal sensor detect a user operation of the accelerator pedal or a brake pedal operation during execution of the process from steps S102 to S112, respectively, the control unit 104 interrupts the process, and the process proceeds to step S101. Other control systems, in addition to the present process, perform conventional general acceleration or deceleration control corresponding to the detected operation of the accelerator pedal or brake pedal.

[0053] The time period for which the second actuator unit 300 generates the negative jerk j2 ends when the coasting state of the vehicle ends. In addition, the time period may end when, for example, the vehicle speed decreases to a predetermined positive speed or zero in the case where the coasting state is relatively long. The predetermined positive speed may be set by a method using a map based on the vehicle speed or the like, such as the above-described method used for calculating the target jerk. Alternatively, the time period of maintaining generation of the negative jerk may be a predetermined predetermined time period or may be variably set using a method similar to the above-described method for calculating the target jerk.

[0054] Examples of control based on the above process are described. Fig. Figure 11 shows diagrams in which a horizontal axis represents time, a vertical axis represents an operating travel of the accelerator pedal, and a thick solid line represents the acceleration of the vehicle. The diagrams showing the relationship between acceleration and time in Fig. 11, the top diagram shows the case where step S107 is executed without an increase in the braking force of the first actuator unit 200 occurring due to the predetermined factor. The second diagram from the top shows the case where step S108 is executed with the increase in the braking force of the first actuator unit 200 occurring due to the predetermined factor. The third diagram from the top shows the case where step S109 is executed with the increase in the braking force of the first actuator unit 200 occurring due to the predetermined factor.

[0055] In the diagrams of Fig. 11, dash-dotted lines further indicate an acceleration corresponding to the braking force generated by the first actuator unit 200. For comparison, thick dotted lines indicate the acceleration at the time of executing step S107, although an increase in the braking force of the first actuator unit 200 occurs due to the predetermined factor.

[0056] Until time T1, the user operates the accelerator pedal, so that a conventional control is executed that corresponds to the operating travel of the accelerator pedal, thereby generating positive acceleration.

[0057] At time T1, when the user completes an accelerator pedal operation, the vehicle switches to a coasting state in which both the accelerator pedal operation and the brake pedal operation are not performed. After time T1, the braking force is generated by the first actuator unit 200 in all of the three diagrams showing the relationship between acceleration and time in Fig. 11. In the case of the top diagram and the second diagram from the top in the diagrams showing the relationship between acceleration and time in Fig. 11, braking force is further generated by the second actuator unit 300. With the braking force, the acceleration of the vehicle gradually decreases.

[0058] In the case of the second diagram from the top and the third diagram from the top in the diagrams showing the relationship between acceleration and time in Fig. 11, an increase in braking force occurs due to the predetermined factor at time T2 and therefore the braking force generated by the first actuator unit 200 increases. The second diagram from the top and the third diagram from the top both show the case where the predetermined factor occurs at time T1 and an increase in braking force actually occurs at time T2, and the case where an occurrence of the predetermined factor is predicted at time T1 and the predetermined factor actually occurs at time T2 or an increase in braking force occurs almost at the same time as the prediction. In the case of the third diagram from the top, in the diagrams showing the relationship between acceleration and time in Fig. 11, the magnitude of the negative jerk (slope) generated by the second actuator unit 300 is further reduced than that in the case of the second diagram from the top in the diagrams showing the relationship between acceleration and time. In the case of the third diagram from the top in the diagrams showing the relationship between acceleration and time, the second actuator unit 300 does not generate the jerk. Accordingly, in the case shown in Fig. In the example shown in Figure 11, among three graphs showing the relationship between acceleration and time, the vehicle's acceleration exhibits an identical negative acceleration a1 at time T3. This indicates that regardless of the presence or degree of change in the braking force by the first actuator unit 200, the time required to achieve the same acceleration is the same. As a result, the user can be provided with a consistent deceleration sensation.

[0059] On the other hand, when there is a change in the braking force by the first actuator unit 200 and the jerk to be generated by the second actuator is not limited, the time required until the same acceleration is reached becomes shorter or the negative acceleration a2, a3 at time T3 becomes smaller than the acceleration a1, as shown by the thick dotted lines in the second and third diagrams from the top in the diagrams showing the relationship between acceleration and time in Fig. 11. As a result, the perceived delay provided to the user becomes too great. Effects

[0060] In the invention, jerk is controlled to achieve a deceleration feeling that is assumed to be expected by the user during the vehicle's coasting state, thereby achieving appropriate ride comfort and operating feel of a vehicle. Specifically, when braking force increases due to gear shifting of the transmission or the like, the jerk generated by the brake or the like is reduced to reduce fluctuation in the deceleration feeling and limit the deterioration of ride comfort and operating feel.

[0061] Although an embodiment of the invention has been described above, the invention can be regarded as a control method of braking force which is carried out by one or more computers included in a braking force control device, a braking force control program, a computer-readable non-volatile recording medium storing the braking force control program, and a vehicle or the like on which a braking force control system is mounted in addition to the braking force control device.

[0062] The invention is useful for the brake force control device mounted on a vehicle or the like.

[0063] A braking force control device includes: a target jerk calculation unit; a first estimation unit configured to estimate an increase in braking force when a predetermined factor currently occurs that increases a braking force to be generated by the first actuator unit; a second estimation unit configured to estimate the increase in braking force when the predetermined factor occurs within a predetermined period of time; and a control unit configured to determine a negative jerk generated when the second actuator unit generates the braking force, such that a sum of the negative jerk and the jerk generated by the first actuator unit without the predetermined factor becomes the target jerk. When the increase in braking force due to the predetermined factor is greater than a predetermined value, the control unit corrects the determined negative jerk so that an absolute value of the negative jerk becomes smaller.

Claims

[1] A braking force control device mounted on a vehicle, comprising a first actuator unit (200) and a second actuator unit (300) configured to generate braking force, wherein the braking force control device is configured to control the braking force to be generated by the second actuator unit (300) when an operating travel of an accelerator pedal changes from non-zero to zero and the vehicle is placed in a coasting state because an operating travel of a brake pedal is zero, wherein the braking force control device comprises a target jerk calculation unit (101), a first estimation unit (102) and a control unit (104), wherein the target jerk calculation unit (101) is designed to calculate a target jerk which is a jerk generation target value when the braking force is generated in the vehicle, the jerk being negative when a vehicle traveling direction is defined as a positive direction, and wherein the first estimation unit (102) is designed to determine whether or not a predetermined factor is currently occurring which increases the braking force generated by the first actuator unit (200), and, if it determines that the predetermined factor is occurring, to estimate an increase in the braking force due to the predetermined factor, and wherein the control unit (104) is designed to determine, based on a calculation result of the target jerk calculation unit (101), that a sum of the negative jerk generated when the second actuator unit (300) generates the braking force and the jerk generated by the first actuator unit (200) when the predetermined factor does not increase the braking force becomes the target jerk, wherein the brake force control device further a second estimation unit (103) configured to determine whether or not the predetermined factor occurs within a predetermined period of time from a present time, even if the predetermined factor does not currently occur in the vehicle, and, if it determines that the predetermined factor occurs, to estimate an increase in the braking force due to the predetermined factor, and wherein if the predetermined factor currently occurs or occurs within the predetermined period of time and the increase in braking force due to the predetermined factor is greater than a predetermined value, the control unit (104) corrects the determined negative jerk on the basis of an estimation result of the first estimation unit (102) or the second estimation unit (103) so that an absolute value of the negative jerk becomes smaller, the first actuator unit (200) comprises a gearbox and a lock-up clutch, the specified factor includes engagement of the lock-up clutch, and the first estimation unit (102) and the second estimation unit (103) estimate an increase in braking force due to the engagement of the lock-up clutch based on a difference between a speed of an engine and a lock-up clutch-side speed of the transmission and / or an oil temperature of the lock-up clutch, characterized by , that the second estimation unit (103) determines whether or not the engagement of the lock-up clutch occurs within a predetermined period of time from a present time based on the current speed, the current acceleration and the current gear change speed of the vehicle. [2] Brake force control device according to claim 1, wherein the specified factor includes a gear change by the transmission, and the first estimation unit (102) and the second estimation unit (103) estimate an increase in braking force due to the gear change by the transmission based on a current gear ratio of the transmission and / or an oil temperature of the transmission. [3] A braking force control device according to claim 2, wherein the second estimation unit (103) determines whether or not a gear change of the transmission occurs within a predetermined period of time from a present time based on current speed, current acceleration and current gear change speed of the vehicle.

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