Brake control system

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

Technical Field

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

Background Art

[0002] Conventionally, a technique related to regenerative cooperative control for applying regenerative braking force and frictional braking force to vehicle wheels using a regenerative braking device and a frictional braking device has been known. For example, Patent Document 1 describes a braking control device that increases the frictional braking force applied to a wheel so that the frictional braking force applied to the wheel becomes greater than the regenerative braking force applied to the wheel when the target vehicle braking force increases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When braking force is applied to a vehicle, pitching motion occurs due to the action of multiple forces. And the forces that cause pitching motion in the vehicle may have different instantaneous rotation centers for each force. However, although the braking control device described in Patent Document 1 attempts to suppress pitching motion while considering the anti-force during braking, it does not consider multiple forces or the difference in the instantaneous rotation centers of those forces. Therefore, there is a possibility that the pitching motion cannot be appropriately adjusted.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a braking control device capable of more appropriately adjusting the pitching motion of a vehicle in regenerative cooperative control.

Means for Solving the Problems

[0006] To achieve the above objective, the braking control device of the present invention is a braking control device that uses a regenerative braking device that applies regenerative braking force to the front and rear wheels of a vehicle and a friction braking device that applies friction braking force to the front and rear wheels, and performs regenerative coordinated control that outputs the required braking force required for braking the vehicle in coordination with the regenerative braking force and the friction braking force, wherein the intersection of the extension line of the regenerative front anti-angle, which is the anti-nose-up angle of the vehicle, and the extension line of the regenerative rear anti-angle, which is the anti-squat angle, is set as the first instantaneous rotation center, and the intersection of the extension line of the friction front anti-angle, which is the anti-nose-dive angle of the vehicle, and the extension line of the friction rear anti-angle, which is the anti-tail-lift angle, is set as the second instantaneous With the intermediate rotation center, during the execution of the regenerative cooperative control, the first load transfer amount due to the inertial force and anti-force acting on the spring located above the vehicle's suspension due to the regenerative braking force at the first instantaneous rotation center and the second load transfer amount due to the inertial force and anti-force acting on the spring due to the frictional braking force at the second instantaneous rotation center are calculated, and the regenerative ratio and friction ratio, which are the distribution ratios of the regenerative braking force and the frictional braking force, and the front ratio and rear ratio, which are the distribution ratios of 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 load transfer amount and the second load transfer amount approaches a value corresponding to the vehicle's target pitch angle.

[0007] This configuration allows for the consideration of both the first load transfer acting on the spring at the first instantaneous center of rotation and the second load transfer acting on the spring at the second instantaneous center of rotation during the vehicle's pitching motion, and enables the sum of these to approach a value corresponding to the target pitch angle. As a result, it becomes easier to maintain the vehicle's pitch angle at the target pitch angle. Therefore, the braking control device of the present invention allows for more appropriate adjustment of the vehicle's pitching motion.

[0008] Furthermore, it is preferable that the first load transfer amount further includes the load transfer amount acting on the spring at the first instantaneous center of rotation due to the reaction torque of the regenerative braking force. This configuration allows for more accurate calculation of the first load transfer amount and more precise adjustment of the vehicle's pitching motion.

[0009] Furthermore, if the friction front anti-angle is greater than the regenerative front anti-angle, the friction rear anti-angle is greater than the regenerative rear anti-angle, the regenerative rear anti-angle is greater than the regenerative front anti-angle, and the friction rear anti-angle is greater than the friction front anti-angle, it is preferable to increase the front ratio in proportion to the decrease in the regenerative ratio when the regenerative ratio decreases due to a change in the upper limit of the vehicle's regenerative power generation. With this configuration, even if the friction ratio increases due to a decrease in the regenerative power generation, increasing the front ratio reduces the anti-force on the rear side, which tends to be larger than the front side, and allows for appropriate adjustment of the pitch angle.

[0010] Furthermore, assuming that the friction front anti-angle is greater than the regenerative front anti-angle, the friction rear anti-angle is greater than the regenerative rear anti-angle, the regenerative rear anti-angle is greater than the regenerative front anti-angle, the friction rear anti-angle is greater than the friction front anti-angle, and the pitch angle of the vehicle increases in the positive direction as the vehicle's attitude changes towards nose dive, it is preferable to increase at least one of the friction ratio and the rear ratio as the vehicle's pitch angle is greater than the target pitch angle, and to decrease at least one of the friction ratio and the rear ratio as the vehicle's pitch angle is smaller than 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 friction braking force, which tends to be larger than that on the regenerative side, and the anti-force on the rear side, which tends to be larger than that on the front side.

[0011] Furthermore, if the first load transfer is greater than the second load transfer, it is preferable to adjust the distribution ratio so that the second load transfer increases, and if the second load transfer is greater than the first load transfer, it is preferable to adjust the distribution ratio so that the first load transfer increases. With this configuration, the sum of the first load transfer and the second load transfer can be easily kept constant. [Effects of the Invention]

[0012] According to the braking control device of the present invention, the pitching motion of the vehicle can be adjusted more appropriately in regenerative braking coordinated control. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing a vehicle equipped with a braking control device according to an embodiment. [Figure 2] This is an explanatory diagram showing an example of the time evolution of required braking force, regenerative braking force, and friction braking force in regenerative braking coordinated control. [Figure 3] This is a schematic diagram illustrating the pitching motion of a vehicle during operation. [Figure 4] This is a schematic diagram illustrating the pitching motion of a vehicle during braking. [Figure 5] This is an explanatory diagram illustrating the instantaneous center of rotation of a vehicle. [Figure 6] This is a schematic diagram illustrating the amount of load transfer due to reaction torque. [Figure 7] This is an explanatory diagram plotting an example of the pitch angle when the regeneration ratio, friction ratio, front ratio, and rear ratio are changed. [Figure 8] This is an explanatory diagram showing an example of the time change of the pitch angle when regenerative coordinated control is performed. [Modes for carrying out the invention]

[0014] An embodiment of the present invention will be described below with reference to the drawings.

[0015] (vehicle) FIG. 1 is a schematic configuration diagram showing a vehicle equipped with a braking control device according to an embodiment. The vehicle 1 is a four-wheel drive electric vehicle that transmits the power from the front motor 10f as a driving power source to the left and right front wheels 2f and transmits the power from the rear motor 10r as a driving power source to the left and right rear wheels 2r to run. The front motor 10f outputs a driving force to the left and right front wheels 2f via a transaxle 12f including a transmission and a differential gear. The rear motor 10r outputs a driving force to the left and right rear wheels 2r via a transaxle 12r including a transmission and a differential gear. The vehicle 1 is equipped with a battery 14 as a power source configured as a secondary battery such as a lithium-ion battery, and the 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 driven and controlled by a control device 16 (braking control device).

[0016] Further, the vehicle 1 is equipped with a braking device that applies a braking force to the front wheels 2f and the rear wheels 2r. The braking device includes a regenerative braking device 20 and a friction braking device 30. The regenerative braking device 20 includes the front motor 10f and the rear motor 10r, the battery 14, and a power conversion device such as an inverter not shown. The front motor 10f and the rear motor 10r are forcedly driven by the rotational forces of the front wheels 2f and the rear wheels 2r during decelerated running with the accelerator off of the vehicle 1 to generate regenerative power, and apply a 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 a friction braking force to each of the front wheels 2f and each of the rear wheels 2r by the frictional force generated by pressing a brake pad 34 driven by an actuator not shown against a disc rotor 32 provided corresponding to each of the front wheels 2f and each of the rear wheels 2r. 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 composed of an input / output device, a storage device (such as ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc., and performs comprehensive control of the vehicle 1. The control device 16 inputs detection amounts detected by various sensors (not shown) such as accelerator opening, brake stroke, vehicle speed, and wheel speed, and various operation information. Based on the various input detection amounts and various operation 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 running of the vehicle 1, and controls various devices of the vehicle 1 based on the calculated information. For example, the control device 16 executes regenerative cooperative control that outputs the required braking force required for braking the vehicle 1 by cooperating the regenerative braking force and the frictional braking force using the regenerative braking device 20 and the frictional braking device 30.

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

[0020] Specifically, the control device 16 sets the regenerative ratio k, friction ratio m, front ratio f, and rear ratio r, expressed by the following equations (1) to (4), so that the sum of the regenerative braking forces Fkf, Fkr and friction braking forces Fmf, Fmr satisfies the required braking force Fb. The regenerative ratio k and friction ratio m are the distribution ratios of the regenerative braking forces Fkf, Fkr and the friction braking forces Fmf, Fmr, and are set between a value of 0 and a value of 1 so that their sum is a value of 1. The front ratio f and rear ratio r are the distribution ratios of the braking force applied to the front wheels 2f (Fkf, Fmf) and the braking force applied to the rear wheels 2r (Fkr, Fmr), and are set between a value of 0 and a value of 1 so that their sum is a value of 1. The specific method for setting the above distribution ratios will be described later. However, the regenerative braking forces Fkf and Fkr are set within the range of the upper limit of the regenerative power generation amount, which is set according to the charge level (SOC: state of charge) and temperature of the battery 14. In the example shown in Figure 2, when the driver presses the brake pedal (time t1), regenerative braking forces Fkf and 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 difference between the regenerative braking forces Fkf and Fkr and the required braking force Fb is output as friction braking forces Fmf and 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] (Substitution control) Furthermore, when the vehicle speed of vehicle 1 falls below a predetermined substitution determination speed (time t2) during the execution of regenerative cooperative control, the control device 16 performs substitution control to substitute the portion of the requested braking force Fb that was previously handled by regenerative braking forces Fkf and Fkr with friction braking forces Fmf and Fmr. The predetermined substitution determination speed should be set to a speed at which it can be determined that the vehicle is approaching a stop, and at which the substitution from regenerative braking forces Fkf and Fkr to friction braking forces Fmf and Fmr can be completed before the vehicle comes to a stop. However, it is preferable that the substitution from regenerative braking forces Fkf and Fkr to friction braking forces Fmf and Fmr be performed over a period of time that does not cause slippage in braking. When the substitution control is completed at time t3, the portion of the requested braking force Fb that was previously handled by regenerative braking forces Fkf and Fkr is entirely replaced by friction braking forces Fmf and Fmr. This allows the front motor 10f and rear motor 10r to output creep torque, enabling them to quickly output driving force when the vehicle 1 comes to a stop at time t4 and restarts.

[0023] (Vehicle pitching motion) Next, the pitching motion of vehicle 1 will be explained. Figure 3 is a schematic diagram illustrating the pitching motion of vehicle 1 during driving, and Figure 4 is a schematic diagram illustrating the pitching motion of vehicle 1 during braking. Here, in order to explain the general concept of the change in the pitch direction of vehicle 1 and the resulting load transfer during driving and braking, Figure 4 shows an example in which only frictional braking forces Fmf and Fmr are applied to vehicle 1.

[0024] As shown in Figure 3, when driving forces Fdf and Fdr are applied to the front wheels 2f and rear wheels 2r, an inertial force Fi acts on the rear 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 to tilt upward, resulting in a so-called squat posture change. Also, as shown in Figure 4, when frictional braking forces Fmf and Fmr are applied, an inertial force Fi acts on the front 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 to tilt downward, resulting in a so-called nose dive posture change. At this time, the inclination of the straight line L1 extending in the longitudinal direction 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 is assumed to increase in the positive direction as the vehicle 1 changes posture toward nose dive, and to decrease in the positive direction (increase in the negative direction) as the vehicle 1 changes posture toward squat.

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

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

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

[0028] (Load transfer) As described above, when a squat posture change occurs, the front suspension 18f extends and the rear suspension 18r contracts in vehicle 1. On the other hand, when a nose dive posture change occurs, the front suspension 18f contracts and the rear suspension 18r extends in vehicle 1. The force corresponding to this extension and contraction is the load transfer amount ΔW acting on the inboard portion of vehicle 1 located above the suspension 18 when pitching motion occurs. In this embodiment, the load transfer amount ΔW during regenerative cooperative control is calculated by the method described below, and the regenerative braking force Fkf, Fkr and frictional braking force Fmf, Fmr in 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 vehicle 1 located above the suspension 18 is referred to as the "sprung mass," and the outboard portion located below the suspension 18 is referred to as the "unsprung mass."

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

[0030] (Calculation of load transfer) Next, we will explain the method for calculating the load transfer amount ΔW on the spring of vehicle 1 based on the first instantaneous rotation center A and the second instantaneous rotation center B. During regenerative braking of vehicle 1, the load transfer amount acting on the spring of vehicle 1 with the first instantaneous rotation center A as the pivot point is the load transfer amount ΔWA1 due to inertial force, the load transfer amount ΔWA2 due to reaction torque (see Figure 6), and the load transfer amount ΔWA3 due to anti-force. Furthermore, during frictional braking of vehicle 1, the load transfer amount acting on the spring of vehicle 1 with the second instantaneous rotation center B as the pivot point is the load transfer amount ΔWB1 due to inertial force and the load transfer amount ΔWB2 due to anti-force.

[0031] (Load transfer due to inertial force during regenerative braking) The load transfer amount ΔWA1 due to inertial force 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 (longitudinal acceleration with deceleration side as positive) acting on vehicle 1. Also, "L" is the wheelbase, which is the distance between the front wheels 2f and the rear wheels 2r, "hg" is the height of the center of gravity G, and "ha" is the height of the first instantaneous center of rotation A.

[0032] ΔWA1 = MGx(hg-ha) / L …(5)

[0033] (Load transfer due to reaction torque during regenerative braking) Figure 6 is a schematic diagram illustrating the load transfer amount ΔWA2 due to reaction torque. When regenerative braking forces Fkf and Fkr are applied to vehicle 1, a reaction torque Fc is generated that attempts to rotate the differential case 5 of the differential gear mounted on the vehicle frame 1a on the springs in the opposite direction, without going through the suspension 18. Vehicle 1 is configured such that this reaction torque Fc is transmitted from the differential case 5 to the vehicle frame 1a as a braking torque, without going through the suspension 18. As a result, a load transfer amount ΔWA2 is generated on the springs of vehicle 1, caused by the reaction torque Fc, in a direction in which the front side is lifted and the rear side is pushed down. The load transfer amount ΔWA2 is calculated according to the following equation (6). In equation (6), "Rt" is the radius of the front wheel 2f and the rear wheel 2r.

[0034] ΔWA2 = MGx·Rt / L…(6)

[0035] (Anti-force during regenerative braking) During regenerative braking of vehicle 1, an anti-force is generated corresponding to the regenerative braking forces Fkf and Fkr, as shown in Figure 5. The anti-force generated during regenerative braking is a force in the opposite direction to the anti-nose-up force FaU (Figure 3) at the front and a force in the opposite direction to the anti-squat force FaS (Figure 3) at the rear. Therefore, in the following explanation of regenerative braking, the anti-nose-up angle θaU will be referred to as the "regenerative front anti-angle θkfa," and the anti-force generated by the regenerative braking force Fkf will be referred to as the "regenerative front anti-force Fkfa." Similarly, the anti-squat angle θaS will be referred to as the "regenerative rear anti-angle θkra," and the anti-force generated by the regenerative braking force Fkr will be referred to as the "regenerative rear anti-force Fkra." The regenerative front anti-force Fkfa and the regenerative rear anti-force Fkra are calculated using the following equations (7) and (8). The sum of the regenerative front antiforce Fkfa and the regenerative rear antiforce Fkra equals the load transfer amount ΔWA3.

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

[0037] (Load transfer due to inertial force caused by frictional braking) The load transfer amount ΔWB1 due to the inertial force generated when frictional braking forces Fmf and Fmr are applied to vehicle 1 can be calculated according to the following equation (9). In equation (9), "hb" is the height of the second instantaneous center of rotation B.

[0038] ΔWB1 = MGx(hg-hb) / L …(9)

[0039] (Anti-force due to frictional braking force) Furthermore, as shown in Figure 5, when vehicle 1 is braked by friction, an anti-force is generated corresponding to the friction braking forces Fmf and Fmr. The anti-force generated during friction braking is the anti-nose dive force FaD and the anti-tail lift force FaL (Figure 4). In the following explanation of friction braking, the anti-nose dive angle θaD will be referred to as the "friction front anti-angle θmfa," and the anti-force generated by the friction braking force Fmf will be referred to as the "friction front anti-force Fmfa." Similarly, the anti-tail lift angle θaL will be referred to as the "friction rear anti-angle θmra," and the anti-force generated by the friction braking force Fmr will be referred to as the "friction rear anti-force Fmra." The friction front anti-force Fmfa and the friction rear anti-force Fmra are calculated by the following equations (10) and (11). The sum of these friction front anti-force Fmfa and friction rear anti-force Fmra is the load transfer amount ΔWB2.

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

[0041] (Total amount of load transfer on the spring) The first load transfer, which is the sum of the above load transfer amounts ΔWA1, ΔWA2, and ΔWA3, and the second load transfer, which is the sum of the load transfer amounts ΔWB1 and ΔWB2, are added together while considering the regeneration ratio k and the friction ratio m, and the load transfer amount ΔW on the spring is calculated as shown in equation (12). In equation (12), "MGx", which is the longitudinal force acting on vehicle 1, can be calculated as the sum of the regenerative braking forces Fkf and Fkr and the friction braking forces Fmf and Fmr. Also, in equation (12), if the absolute value of the pitch angle θp is sufficiently small, the anti-angle θa may be used as an approximate value for "tan(θ)".

[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 will change according to the load transfer amount ΔW calculated by equation (12).

[0044] θp=ΔW / (2(Kpf+Kpr)·L) …(13)

[0045] (Example of calculation result for pitch angle θp) Next, we will explain an example of the calculation result of the pitch angle θp calculated by the above equations (12) and (13). Table 1 shows an example of the anti-angle θa of vehicle 1. In vehicle 1 of this embodiment, the regenerative rear anti-angle θkra is greater than the regenerative front anti-angle θkfa, and the friction rear anti-angle θmra is greater than the friction front anti-angle θmfa. Also, the friction front anti-angle θmfa is greater than the regenerative front anti-angle θkfa, and the friction rear anti-angle θmra is greater than the regenerative rear anti-angle θkra. Furthermore, the friction rear anti-angle θmra is the largest among all anti-angles θa, and the friction rear anti-angle θmra is set to have a large difference from the remaining anti-angles θa compared to the differences between the remaining anti-angles θa. In other words, in vehicle 1, the friction rear anti-force Fmra acts most strongly.

[0046] [Table 1]

[0047] Figure 7 is an explanatory diagram plotting an example of the pitch angle θp when the regenerative braking ratio k, friction ratio m, front ratio f, and rear ratio r are changed. The pitch angle θp values ​​shown in the shaded area of ​​Figure 7 were 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. In Figure 7, it is assumed that the height hg of the center of gravity G, the height ha of the first instantaneous rotation center A, and the height hg of the second instantaneous rotation center B do not change when vehicle 1 is braking. In this case, the variables in equation (12) are only the regenerative braking forces Fkf, Fkr and the friction braking forces Fmf, Fmr, and the pitch angle θp can be treated as a value that changes according to the regenerative braking forces Fkf, Fkr and the friction braking forces Fmf, Fmr. Furthermore, if the heights hg, ha, and hb vary depending on the posture of vehicle 1, these values ​​can be obtained using a sensor (not shown) that detects the vehicle's 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 larger than the regenerative front anti-angle θkfa, and the friction rear anti-angle θmra is larger than the regenerative rear anti-angle θkra. In other words, increasing the friction ratio m tends to increase the friction side anti-force (Fmfa, Fmra) relatively, and the pitch angle θp tends to decrease. On the other hand, increasing the regeneration ratio k does not tend to increase the regenerative side anti-force (Fkfa, Fkra) relatively, and the pitch angle θp does not tend to decrease.

[0049] Furthermore, in vehicle 1, the larger the front ratio f, the larger the pitch angle θp, and the larger the rear ratio r, the smaller the pitch angle θp. This is because the regenerative rear anti-force angle θkra is larger than the regenerative front anti-force angle θkfa, and the friction rear anti-force angle θmra is larger than the friction front anti-force angle θmfa. In other words, increasing the rear ratio r tends to increase the rear anti-force (Fkra, Fmra) relatively, and the pitch angle θp tends to decrease. On the other hand, increasing the front ratio f does not tend to increase the front anti-force (Fkfa, Fmfa) relatively, and the pitch angle θp does not tend to decrease.

[0050] Figure 8 is an explanatory diagram showing an example of the time change of the pitch angle θp when regenerative cooperative control is performed. The pitch angle θp shown in Figure 8 is the result of analysis when the behavior of regenerative braking forces Fkf, Fkr and friction braking forces Fmf, Fmr in vehicle 1 is as shown in Figure 2, and the front ratio f and rear ratio r are changed between values ​​from 0 to 1. As shown in the figure, although the pitch angle θp changes in accordance with the change in the required braking force Fb shown in Figure 2, the tendency for the pitch angle θp to increase as the front ratio f increases and the pitch angle θp to decrease as the rear ratio r increases remains unchanged. Also, as shown in the change of the pitch angle θp between time t2 and time t3, for example, it can be seen that when the substitution 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 trend 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, regardless of the magnitude of the required braking force Fb, the contribution of the load transfer amounts ΔWA3 and ΔWB2 of the anti-force to the trend of change in the pitch angle θp is greater than the contribution of the other load transfer amounts ΔWA1, ΔWA2, and ΔWB1 to the trend of change in the pitch angle θp.

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

[0053] Specifically, as shown in Figure 7, the control device 16 increases at least one of the rear ratio r and the friction ratio m as the pitch angle θp (see, for example, “θp1” and “θp2”) becomes larger than the target pitch angle θpt. For example, increasing the rear ratio r increases the rear antiforce (Fkra, Fmra) and decreases the pitch angle θp(θp1). Also, increasing the friction ratio m increases the friction 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 than the target pitch angle θpt. For example, reducing the rear ratio r reduces the rear antiforce (Fkra, Fmra) and increases the pitch angle θp (θp3). Also, increasing the friction ratio m reduces the friction antiforce (Fmfa, Fmra) and increases the pitch angle θp (θp4). As a result, as shown by the solid line in Figure 7, it becomes easier to maintain the pitch angle θp near 0 degrees, which is the target pitch angle θpt.

[0055] Furthermore, consider a case where the upper limit of regenerative power generation fluctuates (decreases) depending on factors such as the charge level and temperature of the battery 14, causing the regeneration ratio k to decrease. In such a case, where the regeneration ratio k must be reduced, the friction ratio m must be increased in order to satisfy the required braking force Fb. Consequently, simply increasing the friction ratio m increases the anti-force on the friction side (Fmfa, Fmra), and tends to reduce the pitch angle θp (for example, "θp4"). Therefore, when the regeneration ratio k decreases due to a decrease in the upper limit of regenerative power generation, the control device 16 adjusts to increase the front ratio f. This reduces the anti-force on the friction side (Fmfa, Fmra) and increases the pitch angle θp4. As a result, it becomes easier to maintain the pitch angle θp near 0 degrees, which is the target pitch angle θpt.

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

[0057] This configuration allows for the consideration of both the first load transfer amount (ΔWA1 + ΔWA3) acting on the spring at the first instantaneous rotation center A and the second load transfer amount (ΔWB1 + ΔWB2) acting on the spring at the second instantaneous rotation center B during the pitching motion of the vehicle 1, and the sum of these can be brought 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 this embodiment allows for more appropriate adjustment of the pitching motion of the vehicle 1.

[0058] Furthermore, the first load transfer amount includes the load transfer amount ΔWA2 acting on the spring at the first instantaneous center of rotation A, due to the reaction torque Fc of the regenerative braking forces Fkf and Fkr. This configuration allows for more accurate calculation of the first load transfer amount (ΔWA1 + ΔWA2 + ΔWA3) and more precise adjustment of the vehicle's pitching motion.

[0059] Furthermore, when the regeneration ratio k decreases due to a change in the upper limit of the regenerative power generation amount of the vehicle 1, the control device 16 increases the front ratio f in proportion to the decrease in the regeneration ratio k. With this configuration, even if the friction ratio m increases due to a decrease in the amount of regenerative power generation, increasing the front ratio f reduces the anti-force on the rear side, which tends to be larger than that on the front side, and allows for appropriate adjustment of the pitch angle θp.

[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 is larger than 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 is smaller than the target pitch angle θpt. With this configuration, the pitch angle θp can be appropriately adjusted by appropriately adjusting the magnitude of the anti-force due to friction braking force, which tends to be larger than that on the regenerative side, and the anti-force on the rear side, which tends to be larger than that on the front side.

[0061] Furthermore, the control device 16 may adjust the regeneration ratio k, friction ratio m, front ratio f, and rear ratio r so that the second load transfer amount increases when the first load transfer amount, which is the sum of the load transfer amounts ΔWA1, ΔWA2, and ΔWA3 in equation (12), is greater than the second load transfer amount, which is the sum of the load transfer amounts ΔWB1 and ΔWB2. If the second load transfer amount is greater than the first load transfer amount, the control device 16 may adjust the regeneration ratio k, friction ratio m, front ratio f, and rear ratio r so that the first load transfer amount increases. With this configuration, the sum of the first load transfer amount and the second load transfer amount calculated in equation (12) can be easily kept constant.

[0062] This concludes the description of the embodiments, but the embodiments of the present invention are not limited to these embodiments. For example, in this embodiment, the first load transfer amount includes the load transfer amount ΔWA2 due to the reaction torque. However, since the load transfer amount ΔWA2 tends to be a small value compared to the load transfer amounts ΔWA1 and ΔWA3, it may be omitted from the first load transfer amount.

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

[0064] Furthermore, the present invention may also be applied to vehicles in which the contribution of other load transfer amounts ΔWA1, ΔWA2, and ΔWB1 to the trend of change in pitch angle θp is greater than the contribution of the anti-force load transfer amounts ΔWA3 and ΔWB2 to the trend of change. Even in that case, the values ​​of the front ratio f, rear ratio r, regeneration ratio k, and friction ratio m should be adjusted so that the load transfer amount ΔW calculated by the above formula (12) approaches the value corresponding to the target pitch angle θpt. [Explanation of symbols]

[0065] 1 vehicle 1a Vehicle frame 2nd Front Wheel 2r rear wheel 10f Front Motor 10r Rear Motor 16 Control device (braking control device) 18 Suspension 18f Front Suspension 18r Rear Suspension 20 Regenerative braking device 30 Friction braking device A: Center of rotation at the first moment B. Center of rotation at the second instant. 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 Side Antiforce Fkra Regenerative Rear Antiforce Fmf, Fmr Friction braking force Fmfa Friction Front Side Antiforce Fmra Friction Rear Antiforce G center of gravity k Regeneration 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 anti-angle (anti-nose-up angle) θkra regenerative rear anti-squat angle (anti-squat angle) θmfa Friction front anti-angle (anti-nose dive angle) θmra Friction rear anti-angle (anti-tail lift angle) θp, θp1, θp2, θp3, θp4 pitch angle θpt Target pitch angle

Claims

1. A braking control device that performs regenerative coordinated control, using a regenerative braking device that applies regenerative braking force to the front and rear wheels of a vehicle, and a friction braking device that applies friction braking force to the front and rear wheels, to output the required braking force required for braking the vehicle by coordinating the regenerative braking force and the friction braking force, The intersection of the extension of the regenerative front anti-angle, which is the anti-nose-up angle of the aforementioned vehicle, and the extension of the regenerative rear anti-angle, which is the anti-squat angle, is defined as the first instantaneous center of rotation. The intersection of the extension of the friction front anti-angle, which is the anti-nose dive angle of the aforementioned vehicle, and the extension of the friction rear anti-angle, which is the anti-tail lift angle, is defined as the second instantaneous center of rotation. During the execution of the regenerative cooperative control, the first load transfer amount due to the inertial force and anti-force acting on the spring located above the vehicle's suspension due to the regenerative braking force at the first instantaneous rotation center and the second load transfer amount due to the inertial force and anti-force acting on the spring due to the frictional braking force at the second instantaneous rotation center are calculated. A braking control device that sets the regenerative ratio and friction ratio, which are the distribution ratios of the regenerative braking force and the friction braking force, and the front ratio and rear ratio, which are the distribution ratios of 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 transfer and the second load transfer approaches a value corresponding to the target pitch angle of the vehicle.

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

3. The aforementioned friction front-side anti-angle is greater than the aforementioned regenerative front-side anti-angle. The frictional rear anti-angle is greater than the regenerative rear anti-angle. The aforementioned regenerative rear anti-angle is greater than the aforementioned regenerative front anti-angle, If the friction rear anti-angle is greater than the friction front anti-angle, When the regeneration ratio decreases due to a change in the upper limit of the regenerative power generation amount of the vehicle, the front ratio is increased in proportion to the decrease in the regeneration ratio. A braking control device according to claim 1 or claim 2.

4. The aforementioned friction front-side anti-angle is greater than the aforementioned regenerative front-side anti-angle. The frictional rear anti-angle is greater than the regenerative rear anti-angle. The aforementioned regenerative rear anti-angle is greater than the aforementioned regenerative front anti-angle, The aforementioned friction rear anti-angle is greater than the aforementioned friction front anti-angle. Assuming that the pitch angle of the vehicle increases in the positive direction as the vehicle's attitude changes towards nose dive, The greater the pitch angle of the vehicle relative to the target pitch angle, the greater the friction ratio and the rear ratio, and the smaller the pitch angle of the vehicle relative to the target pitch angle, the smaller the friction ratio and the rear ratio, the smaller the rear ratio. A braking control device according to claim 1 or claim 2.

5. The braking control device according to claim 1 or claim 2, wherein if the first load transfer amount is greater than the second load transfer amount, the distribution ratio is adjusted so that the second load transfer amount increases, and if the second load transfer amount is greater than the first load transfer amount, the distribution ratio is adjusted so that the first load transfer amount increases.

Images