Braking control device

Abstract

In the present invention, the intersection of an extension line L2 of a regenerative front-side anti-angle θkfa (anti-nose up angle θaU) and an extension line L3 of a regenerative rear-side anti-angle θkra (anti-squat angle θaS) is defined as a first instantaneous rotation center A, and the intersection of an extension line L4 of a friction front-side anti-angle θmfa (anti-nose dive angle θaD) and an extension line L5 of a friction rear-side anti-angle θmra (anti-tail lift angle θaL) is defined as a second instantaneous rotation center B. A control device 16 sets a regeneration ratio k, a friction ratio m, a front ratio f, and a rear ratio r such that the total sum of a first load movement amount (ΔWA1 + ΔWA3) by an inertia force and an anti-force acting on a spring by regenerative braking forces Fkf, Fkr at the first instantaneous rotation center A, and a second load movement amount (ΔWB1 + ΔWB2) by an inertia force and an anti-force acting on a spring by friction braking forces Fmf, Fmr at the second instantaneous rotation center B approaches a value corresponding to a target pitch angle θpt of a vehicle.

Description

Braking control device

[0001] The present invention relates to a braking control device for a vehicle that performs regenerative cooperative control.

[0002] Conventionally, there has been known a technology relating to a regenerative cooperative control that applies a regenerative braking force and a friction braking force to a wheel of a vehicle using a regenerative braking device and a friction braking device. For example, Patent Document 1 describes a braking control device that increases the friction braking force applied to a wheel so that the friction braking force applied to the wheel becomes greater than the regenerative braking force applied to the wheel when a target vehicle braking force increases.

[0003] Japanese Patent Application Laid-Open No. 2021-115926

[0004] When braking force is applied to a vehicle, pitching motion occurs due to the action of multiple forces. The forces that cause pitching motion in the vehicle may have different instantaneous centers of rotation. However, while the braking control device described in Patent Document 1 attempts to suppress pitching motion while taking into account antiforce during braking, it does not take into account the multiple forces or the instantaneous centers of rotation of those forces. Therefore, it may not be possible to appropriately adjust the pitching motion.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a braking control device that can more appropriately adjust the pitching motion of a vehicle in regenerative cooperative control.

[0006] In order to achieve the above object, the brake control device of the present invention is a brake control device that performs regenerative cooperative control to output a required braking force required for braking the vehicle by coordinating the regenerative braking force and the friction braking force using a regenerative braking device that applies a regenerative braking force to the front wheels and the rear wheels of a vehicle, and a friction braking device that applies a friction braking force to the front wheels and the rear wheels, and the brake control device performs regenerative cooperative control to output a required braking force required for braking the vehicle by coordinating the regenerative braking force and the friction braking force, and the brake control device sets a first instantaneous rotation center at an intersection of an extension line of a regenerative front-side anti-angle that is an anti-nose-up angle of the vehicle and an extension line of a regenerative rear-side anti-angle that is an anti-squat angle of the vehicle, and sets a second instantaneous rotation center at an intersection of an extension line of the friction front-side anti-angle that is an anti-nose-dive angle of the vehicle and an extension line of the friction rear-side anti-angle that is an anti-tail-lift angle of the vehicle. and during execution of the regenerative cooperative control, a first weight movement amount due to the inertial force and antiforce acting on a spring located above a suspension of the vehicle at the first instantaneous center of rotation due to the regenerative braking force, and a second weight movement amount due to the inertial force and antiforce acting on the spring at the second instantaneous center of rotation due to the frictional braking force, are calculated, and a regenerative ratio and a friction ratio, which are the distribution ratios between the regenerative braking force and the frictional braking force, and a front ratio and a rear ratio, which are the distribution ratios between the braking force applied to the front wheels and the braking force applied to the rear wheels, are set so that the sum of the first weight movement amount and the second weight movement amount approaches a value corresponding to the target pitch angle of the vehicle.

[0007] With this configuration, the vehicle pitching motion can be adjusted by taking into account both the first load movement amount acting on the spring at the first instantaneous center of rotation and the second load movement amount acting on the spring at the second instantaneous center of rotation, and making the sum of these amounts approach a value corresponding to the target pitch angle. As a result, the vehicle pitch angle can be more easily maintained at the target pitch angle. Therefore, the brake control device of the present invention can more appropriately adjust the vehicle pitching motion.

[0008] Preferably, the first weight movement amount further includes a weight movement amount acting on the spring at the first instantaneous center of rotation due to a reaction torque of the regenerative braking force. This configuration makes it possible to more accurately calculate the first weight movement amount and more accurately adjust the pitching motion of the vehicle.

[0009] Furthermore, when the friction front-side anti-angle is greater than the regenerative front-side anti-angle, the friction rear-side anti-angle is greater than the regenerative rear-side anti-angle, the regenerative rear-side anti-angle is greater than the regenerative front-side anti-angle, and the friction rear-side anti-angle is greater than the friction front-side anti-angle, if the regeneration ratio decreases due to a fluctuation in an upper limit of the amount of regenerative power generation of the vehicle, it is preferable to increase the front ratio in accordance with the amount of decrease in the regeneration ratio. With this configuration, even if the friction ratio increases due to a decrease in the amount of regenerative power generation, by increasing the front ratio, it is possible to reduce the anti-force on the rear side, which tends to be greater than that on the front side, and appropriately adjust the pitch angle.

[0010] Furthermore, in the case where the friction front-side anti-angle is greater than the regenerative front-side anti-angle, the friction rear-side anti-angle is greater than the regenerative rear-side anti-angle, the regenerative rear-side anti-angle is greater than the regenerative front-side anti-angle, the friction rear-side anti-angle is greater than the friction front-side anti-angle, and the pitch angle of the vehicle increases in the positive direction so that the vehicle changes attitude toward the nose dive side, it is preferable to increase at least one of the friction ratio and the rear ratio as the pitch angle of the vehicle increases relative to the target pitch angle, and decrease at least one of the friction ratio and the rear ratio as the pitch angle of the vehicle decreases relative to the target pitch angle. With this configuration, the pitch angle can be appropriately adjusted by appropriately adjusting the magnitude of the anti-force due to frictional braking force, which tends to be greater than the regenerative side, and the anti-force on the rear side, which tends to be greater than the front side.

[0011] Furthermore, it is preferable that when the first load shift amount is larger than the second load shift amount, the distribution ratio is adjusted so that the second load shift amount is larger, and when the second load shift amount is larger than the first load shift amount, the distribution ratio is adjusted so that the first load shift amount is larger. With this configuration, the sum of the first load shift amount and the second load shift amount can be easily maintained constant.

[0012] According to the braking control device of the present invention, it is possible to more appropriately adjust the pitching motion of the vehicle in the regenerative cooperative control.

[0013] FIG. 1 is a schematic configuration diagram showing a vehicle equipped with a brake control device according to an embodiment. FIG. 2 is an explanatory diagram showing an example of time variations in required braking force, regenerative braking force, and friction braking force in regenerative cooperative control. FIG. 3 is an explanatory diagram showing a schematic view of pitching motion when the vehicle is driven. FIG. 4 is an explanatory diagram showing a schematic view of pitching motion when the vehicle is braking. FIG. 5 is an explanatory diagram showing a schematic view of the instantaneous center of rotation of the vehicle. FIG. 6 is a schematic diagram for explaining the amount of load movement due to reaction torque. FIG. 7 is an explanatory diagram plotting an example of pitch angle when the regenerative ratio, friction ratio, front ratio, and rear ratio are changed. FIG. 8 is an explanatory diagram showing an example of time variations in pitch angle when regenerative cooperative control is performed.

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] (Vehicle) FIG. 1 is a schematic diagram showing a vehicle equipped with a brake control device according to an embodiment. The vehicle 1 is a four-wheel-drive electric vehicle that travels by transmitting power from a front motor 10f, which serves as a power source, to left and right front wheels 2f and from a rear motor 10r, which serves as a power source, to left and right rear wheels 2r. The front motor 10f outputs driving power to the left and right front wheels 2f via a transaxle 12f, which includes a transmission and a differential gear. The rear motor 10r outputs driving power to the left and right rear wheels 2r via a transaxle 12r, which also includes a transmission and a differential gear. The vehicle 1 is equipped with a battery 14, which serves as a power source and is configured as a secondary battery such as a lithium-ion battery. Electric power from the battery 14 is supplied to the front motor 10f and the rear motor 10r via a power conversion device such as an inverter (not shown). The front motor 10f and the rear motor 10r are drive-controlled by a control device 16 (brake control device).

[0016] The vehicle 1 is also equipped with a braking device that applies braking force to the front wheels 2f and rear wheels 2r. The braking device includes a regenerative braking device 20 and a friction braking device 30. The regenerative braking device 20 is configured to include a front motor 10f, a rear motor 10r, a battery 14, and a power conversion device such as an inverter (not shown). When the vehicle 1 is decelerating with the accelerator released, the front motor 10f and the rear motor 10r are forcibly driven by the rotational force of the front wheels 2f and the rear wheels 2r to generate regenerative power and apply regenerative braking force to the front wheels 2f and the rear wheels 2r. The regenerative power generated by the front motor 10f and the rear motor 10r is supplied to the battery 14.

[0017] The friction braking device 30 is a disc brake device that applies friction braking force to each of the front wheels 2 f and each of the rear wheels 2 r by the friction force generated by pressing brake pads 34 driven by an actuator (not shown) against disc rotors 32 provided corresponding to each of the front wheels 2 f and each of the rear wheels 2 r. The actuator may be either hydraulic or electric. The friction braking device 30 is driven and controlled by the control device 16.

[0018] The control device 16 is configured to include input / output devices, storage devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc., and performs overall control of the vehicle 1. The control device 16 receives detected quantities and various operational information detected by various sensors (not shown), such as accelerator opening, brake stroke, vehicle speed, and wheel speed. Based on the input detected quantities and operational information, the control device 16 calculates information necessary for controlling the vehicle 1, such as the required driving force and the required braking force required for the vehicle 1 to travel, and controls various devices of the vehicle 1 based on the calculated information. For example, the control device 16 uses the regenerative braking device 20 and the friction braking device 30 to perform regenerative cooperative control, which outputs the required braking force required for braking the vehicle 1 in a coordinated manner using regenerative braking force and friction braking force.

[0019] 2 is an explanatory diagram showing an example of time variations in the required braking force, regenerative braking force, and friction braking force in regenerative cooperative control. The control device 16 calculates the required braking force Fb according to the amount of brake application by the driver, and based on the calculated required braking force Fb, sets the regenerative braking force Fkf to be applied from the front motor 10f to the front wheels 2f, the regenerative braking force Fkr to be applied from the rear motor 10r to the rear wheels 2r, the friction braking forces Fmf to be applied from each friction braking device 30 to the front wheels 2f, and the friction braking forces Fmr to be applied to the rear wheels 2r.

[0020] Specifically, the control device 16 sets the regeneration ratio k, friction ratio m, front ratio f, and rear ratio r, which are expressed by the following equations (1) to (4), so that the sum of the regenerative braking forces Fkf, Fkr and the friction braking forces Fmf, Fmr satisfies the required braking force Fb. The regeneration ratio k and friction ratio m are distribution ratios between the regenerative braking forces Fkf, Fkr and the friction braking forces Fmf, Fmr, and are set between 0 and 1 so that their sum is 1. The front ratio f and rear ratio r are distribution ratios between the braking forces (Fkf, Fmf) applied to the front wheels 2f and the braking forces (Fkr, Fmr) applied to the rear wheels 2r, and are set between 0 and 1 so that their sum is 1. A specific method for setting the distribution ratios will be described later. However, the regenerative braking forces Fkf, Fkr are set at least within the upper limit of the amount of regenerative power generation, which is set depending on the state of charge (SOC) and temperature of the battery 14. In the example shown in Figure 2, when the driver depresses the brake pedal (time t1), regenerative braking forces Fkf, Fkr are output within the upper limit of the regenerative power generation amount in accordance with the change in the required braking force Fb, and the shortfall of the regenerative braking forces Fkf, Fkr relative to the required braking force Fb is output as friction braking forces Fmf, Fmr.

[0021] k=(Fkf+Fkr) / (Fkf+Fkr+Fmf+Fmr)...(1) m=(Fmf+Fmr) / (Fkf+Fkr+Fmf+Fmr)...(2) f=(Fkf+Fmf) / (Fkf+Fkr+Fmf+Fmr)...(3) r=(Fkr+Fmr) / (Fkf+Fkr+Fmf+Fmr)...(4)

[0022] (Replacement Control) Furthermore, when the vehicle speed of the vehicle 1 falls below a predetermined replacement determination vehicle speed during execution of the regenerative cooperative control (time t2), the control device 16 executes replacement control to replace the regenerative braking forces Fkf and Fkr of the required braking force Fb with frictional braking forces Fmf and Fmr. The predetermined replacement determination vehicle speed can be set to a vehicle speed at which it can be determined that the vehicle is approaching a stop and at which the replacement from the regenerative braking forces Fkf and Fkr to the frictional braking forces Fmf and Fmr can be completed before the vehicle comes to a stop. However, it is preferable to perform the replacement from the regenerative braking forces Fkf and Fkr to the frictional braking forces Fmf and Fmr over a period of time that does not cause slippage in braking. When the replacement control is completed at time t3, the portion of the required braking force Fb that was previously borne by the regenerative braking forces Fkf and Fkr is completely replaced by the frictional braking forces Fmf and Fmr. This enables creep torque to be output from the front motor 10f and rear motor 10r, and after the vehicle 1 stops at time t4, driving force can be quickly output from the front motor 10f and rear motor 10r when the vehicle starts moving again.

[0023] (Vehicle Pitching Movement) Next, the pitching movement of the vehicle 1 will be described. Fig. 3 is an explanatory diagram that schematically shows the pitching movement of the vehicle 1 when it is being driven, and Fig. 4 is an explanatory diagram that schematically shows the pitching movement of the vehicle 1 when it is being braked. Here, in order to explain the general concept of the change in attitude of the vehicle 1 in the pitch direction when it is being driven and when it is being braked, and the accompanying load movement, Fig. 4 shows an example in which only frictional braking forces Fmf and Fmr are applied to the vehicle 1.

[0024] As shown in FIG. 3 , when driving forces Fdf and Fdr are applied to the front wheels 2f and the rear wheels 2r, an inertial force Fi acts on the rear side of the vehicle 1. As a result, a pitch moment Mp acts on the center of gravity G of the vehicle 1, causing the front side to tilt upward, resulting in a posture change known as a squat. Furthermore, as shown in FIG. 4 , when frictional braking forces Fmf and Fmr are applied, an inertial force Fi acts on the front side of the vehicle 1. As a result, a pitch moment Mp acts on the center of gravity G of the vehicle 1, causing the front side to tilt downward, resulting in a posture change known as a nose dive. At this time, the inclination of a line L1 extending in the fore-and-aft direction and passing through the center of gravity G of the vehicle 1 before and after the posture change is the pitch angle θp. In this embodiment, the pitch angle θp increases in the positive direction as the posture of the vehicle 1 changes toward the nose dive side, and decreases in the positive direction (increases in the negative direction) as the posture of the vehicle 1 changes toward the squat side.

[0025] (Anti-angles and anti-forces) Furthermore, anti-forces act on the vehicle 1 according to anti-angles θa that are predetermined as vehicle specifications. The anti-angles θa include an anti-nose-up angle θaU, an anti-squat angle θaS, an anti-nose-dive angle θaD, and an anti-tail-lift angle θaL. Each anti-angle θa is determined by the geometry of the suspensions 18 (front suspensions 18f and rear suspensions 18r) connected to the front wheels 2f and rear wheels 2r of the vehicle 1.

[0026] When the vehicle 1 is driven, an anti-nose-up force FaU, which is a vertical component of the driving force Fdf, acts on the front side of the vehicle 1 in accordance with the anti-nose-up angle θaU, and an anti-squat force FaS, which is a vertical component of the driving force Fdr, acts on the rear side of the vehicle 1 in accordance with the anti-squat angle θaS. Because the anti-nose-up force FaU is a downward force and the anti-squat force FaS is an upward force, changes in the squat posture of the vehicle 1 are suppressed.

[0027] On the other hand, when the vehicle 1 is braking, an anti-nose-dive force FaD, which is a vertical component of the frictional braking force Fmf, acts on the front side of the vehicle 1 in accordance with the anti-nose-dive angle θaD, and an anti-tail-lift force FaL, which is a vertical component of the frictional braking force Fmr, acts on the rear side of the vehicle 1 in accordance with the anti-tail-lift angle θaL. Because the anti-nose-dive force FaD is an upward force and the anti-tail-lift force FaL is a downward force, changes in the nose-up attitude of the vehicle 1 are suppressed.

[0028] (Weight Transfer) When a squat posture change occurs as described above, the front suspension 18f of the vehicle 1 extends and the rear suspension 18r contracts. On the other hand, when a nose dive posture change occurs, the front suspension 18f of the vehicle 1 contracts and the rear suspension 18r extends. A force corresponding to this amount of expansion and contraction becomes the load transfer amount ΔW acting on the inboard portion of the vehicle 1 located above the suspension 18 when a pitching motion occurs. In this embodiment, the load transfer amount ΔW during regenerative cooperative control is calculated using the method described below, and the regenerative braking forces Fkf, Fkr and friction braking forces Fmf, Fmr during regenerative cooperative control are set based on the relationship between the load transfer amount ΔW and the pitch angle θp. In the following description, the inboard portion of the vehicle 1 above the suspension 18 is referred to as the "sprung portion," and the outboard portion of the vehicle 1 located below the suspension 18 is referred to as the "unsprung portion."

[0029] (Instantaneous Rotation Center) Here, the pitching motion of the vehicle 1 on the springs during regenerative cooperative control can be considered to be behavior caused by a pitch moment acting on the center of gravity G, with the instantaneous rotation center (pitching instantaneous center) of each force acting on the vehicle 1 as a fulcrum. FIG. 5 is an explanatory diagram schematically showing the instantaneous rotation center of the vehicle 1. As shown in the figure, the regenerative braking forces Fkf and Fkr are forces output from the front motor 10f and the rear motor 10r, which are provided on the springs. Therefore, in this embodiment, the intersection of an extension line L2 extending along the anti-nose-up angle θaU and an extension line L3 extending along the anti-squat angle θaS is set as the first instantaneous rotation center A of the pitching motion when the regenerative braking forces Fkf and Fkr are acting. On the other hand, the frictional braking forces Fmf and Fmr are forces output from the frictional braking device 30 provided under the springs. Therefore, in this embodiment, the intersection of an extension line L4 extending along the anti-nose dive angle θaD and an extension line L5 extending along the anti-tail lift angle θaL is set as the second instantaneous center of rotation B of the pitching motion when the frictional braking forces Fmf and Fmr act.

[0030] (Calculation of Load Movement Amount) Next, a method for calculating the load movement amount ΔW on the springs of the vehicle 1 based on the first instantaneous center of rotation A and the second instantaneous center of rotation B will be described. During regenerative braking of the vehicle 1, the following load movements occur on the springs of the vehicle 1 with the first instantaneous center of rotation A as the fulcrum: a load movement amount ΔWA1 due to inertial force, a load movement amount ΔWA2 due to reaction torque (see FIG. 6 ), and a load movement amount ΔWA3 due to antiforce. Furthermore, during frictional braking of the vehicle 1, the following load movements occur on the springs of the vehicle 1 with the second instantaneous center of rotation B as the fulcrum: a load movement amount ΔWB1 due to inertial force, and a load movement amount ΔWB2 due to antiforce.

[0031] (Load movement amount due to inertial force during regenerative braking) The load movement amount ΔWA1 due to inertial force generated when regenerative braking forces Fkf and Fkr are applied to vehicle 1 is calculated according to the following equation (5). In equation (5), "M" is the weight of vehicle 1, and "Gx" is the longitudinal deceleration acting on vehicle 1 (longitudinal acceleration with the deceleration side being positive). Also, "L" is the wheelbase, which is the distance between front wheel 2f and rear wheel 2r, "hg" is the height of center of gravity G, and "ha" is the height of first instantaneous center of rotation A.

[0032] ΔWA1=MGx(hg-ha) / L...(5)

[0033] (Load Transfer Due to Reaction Torque During Regenerative Braking) FIG. 6 is a schematic diagram illustrating a load transfer amount ΔWA2 due to reaction torque. When regenerative braking forces Fkf and Fkr are applied to the vehicle 1, a reaction torque Fc is generated that tends to rotate the differential case 5 of the differential gear, which is mounted on the sprung body frame 1a, in the opposite direction without passing through the suspension 18. The vehicle 1 is configured so that this reaction torque Fc is transmitted from the differential case 5 to the body frame 1a as a braking torque without passing through the suspension 18. As a result, a load transfer amount ΔWA2 is generated on the sprung body of the vehicle 1 due to the reaction torque Fc in a direction that lifts the front side and pushes down the rear side. The load transfer amount ΔWA2 is calculated according to the following equation (6). In equation (6), "Rt" is the radius of the front wheels 2f and the rear wheels 2r.

[0034] ΔWA2=MGx・Rt / L…(6)

[0035] (Antiforce During Regenerative Braking) During regenerative braking of the vehicle 1, as shown in FIG. 5, an antiforce is generated in accordance with the regenerative braking forces Fkf and Fkr. The antiforce generated during regenerative braking is a force on the front side opposite to the anti-nose-up force FaU (FIG. 3) during driving, and a force on the rear side opposite to the anti-squat force FaS (FIG. 3). Therefore, in the following description of regenerative braking, the anti-nose-up angle θaU will be referred to as the "regenerative front-side anti-angle θkfa," and the antiforce generated by the regenerative braking force Fkf will be referred to as the "regenerative front-side anti-force Fkfa." Furthermore, the anti-squat angle θaS will be referred to as the "regenerative rear-side anti-angle θkra," and the antiforce generated by the regenerative braking force Fkr will be referred to as the "regenerative rear-side anti-force Fkra." The regenerative front antiforce Fkfa and the regenerative rear antiforce Fkra are calculated by the following equations (7) and (8): The sum of the regenerative front antiforce Fkfa and the regenerative rear antiforce Fkra is the load shift amount ΔWA3.

[0036] Fkfa=Fkf・tan(θkfa)…(7) Fkra=Fkr・tan(θkra)…(8)

[0037] (Load Movement Due to Inertial Force Caused by Frictional Braking) The load movement amount ΔWB1 due to inertial force generated when frictional braking forces Fmf and Fmr are applied to the vehicle 1 can be calculated according to the following equation (9): "hb" in equation (9) is the height of the second instantaneous center of rotation B.

[0038] ΔWB1=MGx(hg-hb) / L...(9)

[0039] (Antiforce Due to Frictional Braking Force) Furthermore, as shown in FIG. 5, during frictional braking of the vehicle 1, antiforces corresponding to the frictional braking forces Fmf and Fmr are generated. The antiforces generated during frictional braking are an anti-nose dive force FaD and an anti-tail lift force FaL ( FIG. 4 ). In the following description of frictional braking, the anti-nose dive angle θaD will be referred to as the "friction front-side anti-angle θmfa," and the antiforce generated by the frictional braking force Fmf will be referred to as the "friction front-side antiforce Fmfa." Furthermore, the anti-tail lift angle θaL will be referred to as the "friction rear-side anti-angle θmra," and the antiforce generated by the frictional braking force Fmr will be referred to as the "friction rear-side antiforce Fmra." The friction front-side antiforce Fmfa and the friction rear-side antiforce Fmra are calculated using the following equations (10) and (11). The sum of the front friction antiforce Fmfa and the rear friction antiforce Fmra is the load movement amount ΔWB2.

[0040] Fmfa=Fmf・tan(θfma)…(10) Fmra=Fmr・tan(θmra)…(11)

[0041] (Sum of Load Transfer Amounts on the Springs) By adding up the first load transfer amount, which is the sum of the above load transfer amounts ΔWA1, ΔWA2, and ΔWA3, and the second load transfer amount, which is the sum of the load transfer amounts ΔWB1 and ΔWB2, while taking into account the regeneration ratio k and the friction ratio m, the load transfer amount ΔW on the springs is calculated as shown in the following equation (12). Note that "MGx," which is the longitudinal force acting on the vehicle 1 in equation (12), can be calculated as the sum of the regenerative braking forces Fkf and Fkr and the friction braking forces Fmf and Fmr. Furthermore, for "tan(θ)" in equation (12), if the absolute value of the pitch angle θp is sufficiently small, each anti-angle θa may be used as an approximate value.

[0042] ΔW=kΔWA1+kΔWA2+ΔWA3+mΔWB1+ΔWB2=kMGx(hg-ha) / L+kMGx・Rt / L-Fkf・tan (θkfa)-Fkr・tan(θkra)+mMGx(hg-hb) / L-Fmf・tan(θfma)-Fmr・tan(θmra) ...(12)

[0043] (Calculation of Pitch Angle) The pitch angle θp is calculated by the following equation (13). In equation (13), "Kpf" is the spring constant of the front suspension 18f, and "Kpr" is the spring constant of the rear suspension 18r. Since "Kpf", "Kpr", and "L" in equation (13) are constants determined by the vehicle specifications, the pitch angle θp changes depending on the load movement amount ΔW calculated by equation (12).

[0044] θp=ΔW / (2(Kpf+Kpr)・L)...(13)

[0045] (Example of Calculation Results of Pitch Angle θp) Next, an example of the calculation results of the pitch angle θp calculated using the above equations (12) and (13) will be described. Table 1 shows an example of the anti angle θa of the vehicle 1. In the vehicle 1 of this embodiment, the regenerative rear-side anti angle θkra is larger than the regenerative front-side anti angle θkfa, and the friction rear-side anti angle θmra is larger than the friction front-side anti angle θmfa. Furthermore, the friction front-side anti angle θmfa is larger than the regenerative front-side anti angle θkfa, and the friction rear-side anti angle θmra is larger than the regenerative rear-side anti angle θkra. Furthermore, the friction rear-side anti angle θmra is the largest of all the anti angles θa, and the difference between the friction rear-side anti angle θmra and the remaining anti angles θa is set to be larger than the difference between the remaining anti angles θa. In other words, in the vehicle 1, the friction rear-side anti force Fmra acts greatest.

[0046]

[0047] FIG. 7 is an explanatory diagram plotting an example of pitch angle θp when the regeneration ratio k, friction ratio m, front ratio f, and rear ratio r are changed. The values ​​of pitch angle θp shown in the shaded area in FIG. 7 are calculated based on equations (12) and (13) using the vehicle specifications shown in Table 1, assuming that the deceleration and required braking force Fb (= Fkf + Fkr + Fmf + Fmr) are constant. FIG. 7 assumes that the height hg of the center of gravity G, the height ha of the first instantaneous center of rotation A, and the height hg of the second instantaneous center of rotation B do not change during braking of the vehicle 1. In this case, the variables in equation (12) are only the regenerative braking forces Fkf, Fkr, and the frictional braking forces Fmf, Fmr, and the pitch angle θp can be treated as a value that changes depending on the regenerative braking forces Fkf, Fkr, and the frictional braking forces Fmf, Fmr. If the heights hg, ha, and hb vary depending on the attitude of the vehicle 1, these values ​​may be obtained by a sensor (not shown) that detects the vehicle body position.

[0048] As shown in the figure, in vehicle 1, the pitch angle θp increases as the regeneration ratio k increases, and the pitch angle θp decreases as the friction ratio m increases. This is because the friction front anti-angle θmfa is greater than the regeneration front anti-angle θkfa, and the friction rear anti-angle θmra is greater than the regeneration rear anti-angle θkra. In other words, when the friction ratio m increases, the friction side anti-forces (Fmfa, Fmra) tend to become relatively large, and the pitch angle θp tends to become small. On the other hand, even when the regeneration ratio k increases, the regeneration side anti-forces (Fkfa, Fkra) do not tend to become relatively large, and the pitch angle θp tends to become small.

[0049] Furthermore, in vehicle 1, the pitch angle θp increases as the front ratio f increases, and the pitch angle θp decreases as the rear ratio r increases. This is because the regenerative rear-side anti-angle θkra is greater than the regenerative front-side anti-angle θkfa, and the friction rear-side anti-angle θmra is greater than the friction front-side anti-angle θmfa. In other words, when the rear ratio r increases, the rear-side anti-forces (Fkra, Fmra) tend to become relatively large, and the pitch angle θp tends to become small. On the other hand, even when the front ratio f increases, the front-side anti-forces (Fkfa, Fmfa) tend not to become relatively large, and the pitch angle θp tends not to become small.

[0050] FIG. 8 is an explanatory diagram showing an example of how the pitch angle θp changes over time when regenerative cooperative control is performed. The pitch angle θp shown in FIG. 8 is an analysis result obtained by using the example shown in FIG. 2 for the behavior of the regenerative braking forces Fkf, Fkr and the friction braking forces Fmf, Fmr in vehicle 1, and varying the front ratio f and rear ratio r between 0 and 1. As shown in the figure, although the pitch angle θp changes in response to changes in the required braking force Fb shown in FIG. 2, the tendency remains that the pitch angle θp increases as the front ratio f increases and decreases as the rear ratio r increases. Furthermore, as shown in the change in the pitch angle θp between time t2 and time t3, for example, when the switching control is started and the friction ratio m increases, the pitch angle θp tends to decrease.

[0051] As described above, in vehicle 1, the pitch angle θp increases as either the front ratio f or the regeneration ratio k increases, and the pitch angle θp decreases as either the rear ratio r or the friction ratio m increases. Furthermore, the tendency of change in the pitch angle θp in vehicle 1 remains the same even when the required braking force Fb changes, as shown in Figure 8. In other words, vehicle 1 has vehicle specifications such that the contribution of the antiforce load shift amounts ΔWA3 and ΔWB2 to the tendency of change in the pitch angle θp is greater than the contribution of the other load shift amounts ΔWA1, ΔWA2, and ΔWB1 to the tendency of change in the pitch angle θp, regardless of the magnitude of the required braking force Fb.

[0052] (Pitch Angle Adjustment in Regenerative Cooperative Control) Next, adjustment of the pitch angle θp in regenerative cooperative control will be described. In regenerative cooperative control, the control device 16 sets the front ratio f, rear ratio r, regenerative ratio k, and friction ratio m so that the load shift amount ΔW calculated by equation (12) approaches a value corresponding to the target pitch angle θpt ( FIG. 7 ). The target pitch angle θpt is set to 0 degrees, for example. The current pitch angle θp may be detected by a pitch angle detection sensor (not shown).

[0053] Specifically, as shown in FIG. 7 , the control device 16 increases at least one of the rear ratio r and the friction ratio m as the pitch angle θp (e.g., see "θp1" and "θp2") increases relative to the target pitch angle θpt. For example, increasing the rear ratio r increases the rear-side antiforce (Fkra, Fmra) and decreases the pitch angle θp (θp1). In addition, increasing the friction ratio m increases the friction-side antiforce (Fmfa, Fmra) and decreases the pitch angle θp (θp2).

[0054] On the other hand, the control device 16 reduces at least one of the rear ratio r and the friction ratio m as the pitch angle θp (see, for example, "θp3" and "θp4") becomes smaller relative to the target pitch angle θpt. For example, if the rear ratio r is reduced, the rear-side antiforce (Fkra, Fmra) becomes smaller and the pitch angle θp (θp3) becomes larger. Also, if the friction ratio m is increased, the friction-side antiforce (Fmfa, Fmra) becomes smaller and the pitch angle θp (θp4) becomes larger. As a result, as shown by the solid line in FIG. 7, it becomes easier to maintain the pitch angle θp near 0 degrees, which is the target pitch angle θpt.

[0055] Also, assume that the upper limit of the regenerative power generation fluctuates (decreases) depending on, for example, the state of charge or temperature of the battery 14, decreasing the regenerative power generation ratio k. If the regenerative power generation ratio k must be reduced, the friction ratio m must be increased to satisfy the required braking force Fb. Therefore, the larger the friction ratio m, the larger the friction-side antiforce (Fmfa, Fmra) and the smaller the pitch angle θp (e.g., θp4). Therefore, when the regenerative power generation ratio k decreases due to a decrease in the upper limit of the regenerative power generation, the control device 16 adjusts the front ratio f to be larger. This reduces the friction-side antiforce (Fmfa, Fmra) and increases the pitch angle θp4. As a result, the pitch angle θp is more likely to be maintained near 0 degrees, which is the target pitch angle θpt.

[0056] As described above, in this embodiment, the first instantaneous center of rotation A is the intersection of the extension line L2 of the regenerative front-side anti-angle θkfa, which is the anti-nose-up angle θaU, and the extension line L3 of the regenerative rear-side anti-angle θkra, which is the anti-squat angle θaS, and the second instantaneous center of rotation B is the intersection of the extension line L4 of the friction front-side anti-angle θmfa, which is the anti-nose-dive angle θaD of the vehicle, and the extension line L5 of the friction rear-side anti-angle θmra, which is the anti-tail-lift angle θaL. Then, during execution of the regenerative cooperative control, the control device 16 (brake control device) calculates a first load movement amount (ΔWA1 + ΔWA3) due to the inertial force and antiforce acting on the springs located above the suspension 18 of the vehicle 1 at the first instantaneous center of rotation A due to the regenerative braking forces Fkf, Fkr, and a second load movement amount (ΔWB1 + ΔWB2) due to the inertial force and antiforce acting on the springs at the second instantaneous center of rotation B due to the frictional braking forces Fmf, Fmr, and sets the regenerative ratio k, friction ratio m, front ratio f, and rear ratio r so that the sum of the first load movement amount and the second load movement amount approaches a value corresponding to the target pitch angle θpt of the vehicle.

[0057] With this configuration, it is possible to take into account both the first load movement amount (ΔWA1 + ΔWA3) acting on the springs at the first instantaneous center of rotation A and the second load movement amount (ΔWB1 + ΔWB2) acting on the springs at the second instantaneous center of rotation B during the pitching motion of the vehicle 1, and to bring their sum closer to a value corresponding to the target pitch angle θpt. As a result, it becomes easier to maintain the pitch angle θp of the vehicle 1 at the target pitch angle θpt. Therefore, the control device 16 of the embodiment makes it possible to more appropriately adjust the pitching motion of the vehicle 1.

[0058] Furthermore, the first weight movement amount includes a load movement amount ΔWA2 that is caused by the reaction torque Fc of the regenerative braking forces Fkf and Fkr and acts on the spring at the first instantaneous center of rotation A. With this configuration, it is possible to more accurately calculate the first weight movement amount (ΔWA1+ΔWA2+ΔWA3) and more accurately adjust the pitching motion of the vehicle.

[0059] Furthermore, the control device 16 increases the front ratio f in accordance with the amount of decrease in the regeneration ratio k when the regeneration ratio k decreases due to a change in the upper limit of the amount of regenerative power generation of the vehicle 1. With this configuration, even if the friction ratio m increases due to a decrease in the amount of regenerative power generation, the antiforce on the rear side, which tends to be larger than that on the front side, can be reduced by increasing the front ratio f, and the pitch angle θp can be appropriately adjusted.

[0060] Furthermore, the control device 16 increases at least one of the friction ratio m and the rear ratio r as the pitch angle θp of the vehicle 1 increases relative to the target pitch angle θpt, and decreases at least one of the friction ratio m and the rear ratio r as the pitch angle θp decreases relative to the target pitch angle θpt. With this configuration, it is possible to appropriately adjust the magnitude of the antiforce due to the frictional braking force, which tends to be larger than the regenerative side, and the antiforce on the rear side, which tends to be larger than the front side, and thereby appropriately adjust the pitch angle θp.

[0061] Furthermore, when the first weight shift amount, which is the sum of the weight shift amounts ΔWA1, ΔWA2, and ΔWA3 in the above equation (12), is greater than the second weight shift amount, which is the sum of the weight shift amounts ΔWB1 and ΔWB2, the control device 16 may adjust the regeneration ratio k, the friction ratio m, the front ratio f, and the rear ratio r so as to increase the second weight shift amount, and when the second weight shift amount is greater than the first weight shift amount, the control device 16 may adjust the regeneration ratio k, the friction ratio m, the front ratio f, and the rear ratio r so as to increase the first weight shift amount. With this configuration, the sum of the first weight shift amount and the second weight shift amount calculated by equation (12) can be easily maintained constant.

[0062] Although the description of the embodiment has been completed, aspects of the present invention are not limited to this embodiment. For example, in this embodiment, the first weight shift amount includes the load shift amount ΔWA2 due to the reaction torque. However, since the load shift amount ΔWA2 tends to be smaller than the load shift amount ΔWA1 and the load shift amount ΔWA3, it may be omitted from the first weight shift amount.

[0063] In this embodiment, the regenerative rear-side anti-angle θkra is greater than the regenerative front-side anti-angle θkfa, the friction rear-side anti-angle θmra is greater than the friction front-side anti-angle θmfa, the friction front-side anti-angle θmfa is greater than the regenerative front-side anti-angle θkfa, and the friction rear-side anti-angle θmra is greater than the regenerative rear-side anti-angle θkra. However, the value of each anti-angle θa may be changed appropriately depending on the vehicle model. Even in this case, the values ​​of the front ratio f, rear ratio r, regenerative ratio k, and friction ratio m may be adjusted depending on the ease with which the pitch angle θp changes due to each anti-force so that the load transfer amount ΔW calculated by the above equation (12) approaches a value corresponding to the target pitch angle θpt.

[0064] The present invention may also be applied to a vehicle in which the contribution of the other load shift amounts ΔWA1, ΔWA2, and ΔWB1 to the change trend of the pitch angle θp may be greater than the contribution of the antiforce load shift amounts ΔWA3 and ΔWB2 to the change trend of the pitch angle θp. Even in this case, the values ​​of the front ratio f, rear ratio r, regeneration ratio k, and friction ratio m may be adjusted so that the load shift amount ΔW calculated by the above equation (12) approaches the value corresponding to the target pitch angle θpt.

[0065] 1 Vehicle 1a Body frame 2f Front wheels 2r Rear wheels 10f Front motor 10r Rear motor 16 Control device (brake control device) 18 Suspension 18f Front suspension 18r Rear suspension 20 Regenerative braking device 30 Friction braking device A First instantaneous center of rotation B Second instantaneous center of rotation f Front ratio Fb Required braking force Fc Reaction torque Fdf, Fdr Driving force Fi Inertia force Fkf, Fkr Regenerative braking force Fkfa Regenerative front antiforce Fkra Regenerative rear antiforce Fmf, Fmr Friction braking force Fmfa Friction front antiforce Fmra Friction rear antiforce G Center of gravity k Regenerative ratio L1 Straight line L2, L3, L4, L5 Extension line m Friction ratio r Rear ratio ΔW, ΔWA1, ΔWA2, ΔWA3, ΔWB1, ΔWB2 Load transfer amount θa Anti-angle θkfa Regenerative front-side anti-angle (anti-nose-up angle) θkra Regenerative rear-side anti-angle (anti-squat angle) θmfa Friction front-side anti-angle (anti-nose-dive angle) θmra Friction rear-side anti-angle (anti-tail-lift angle) θp, θp1, θp2, θp3, θp4 Pitch angle θpt Target pitch angle

Claims

1. A braking control device that uses a regenerative braking device that applies a regenerative braking force to the front and rear wheels of a vehicle, and a friction braking device that applies a friction braking force to the front and rear wheels, and performs regenerative cooperative control to output a required braking force required for braking the vehicle by coordinating the regenerative braking force and the friction braking force, wherein a first instantaneous center of rotation is an intersection point between an extension line of a regenerative front side anti-angle that is the anti-nose-up angle of the vehicle and an extension line of a regenerative rear side anti-angle that is the anti-squat angle, and a second instantaneous center of rotation is an intersection point between an extension line of a friction front side anti-angle that is the anti-nose-dive angle of the vehicle and an extension line of a friction rear side anti-angle that is the anti-tail-lift angle, and a brake control device that, during execution of the regenerative cooperative control, calculates a first load movement amount due to the inertial force and antiforce acting on a spring located above a suspension of the vehicle at the first instantaneous center of rotation due to the regenerative braking force, and a second load movement amount due to the inertial force and antiforce acting on the spring at the second instantaneous center of rotation due to the frictional braking force, and sets a regenerative ratio and a friction ratio which are the distribution ratios between the regenerative braking force and the frictional braking force, and a front ratio and a rear ratio which are the distribution ratios between the braking force applied to the front wheels and the braking force applied to the rear wheels, so that the sum of the first load movement amount and the second load movement amount approaches a value corresponding to a target pitch angle of the vehicle.

2. The brake control device according to claim 1, further comprising a load shift acting on the spring at the first instantaneous center of rotation due to a reaction torque of the regenerative braking force.

3. A braking control device as described in claim 1 or 2, wherein: when the friction front side anti-angle is greater than the regenerative front side anti-angle, the friction rear side anti-angle is greater than the regenerative rear side anti-angle, the regenerative rear side anti-angle is greater than the regenerative front side anti-angle, and the friction rear side anti-angle is greater than the friction front side anti-angle, when the regenerative ratio becomes smaller due to a fluctuation in an upper limit value of the regenerative power generation of the vehicle, the front ratio is increased in accordance with the amount of decrease in the regenerative ratio.

4. A brake control device as claimed in claim 1 or 2, wherein, when the friction front side anti-angle is greater than the regenerative front side anti-angle, the friction rear side anti-angle is greater than the regenerative rear side anti-angle, the regenerative rear side anti-angle is greater than the regenerative front side anti-angle, the friction rear side anti-angle is greater than the friction front side anti-angle, and the pitch angle of the vehicle increases in the positive direction so that the attitude of the vehicle changes towards the nose dive side, the larger the pitch angle of the vehicle is relative to the target pitch angle, the larger at least one of the friction ratio and the rear ratio is increased, and the smaller the pitch angle of the vehicle is relative to the target pitch angle, the smaller at least one of the friction ratio and the rear ratio is decreased.

5. A braking control device as described in claim 1 or claim 2, wherein when the first load movement amount is greater than the second load movement amount, the distribution ratio is adjusted so that the second load movement amount is greater, and when the second load movement amount is greater than the first load movement amount, the distribution ratio is adjusted so that the first load movement amount is greater.

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