JP2019098839A - Brake system - Google Patents

Abstract

To reduce vibration of a vehicle body due to irregularity of a road surface.SOLUTION: A brake system concerning a vehicle of which a wheel 14 is fitted to a vehicle body 12 via s spring. This brake system has: a corner brake 30 which is brake means for braking the wheel under unsprung, and which is low load brake means of which a maximum braking amount is relatively small; a high load brake 34 which is brake means for braking a power transmission device provided on a spring, and which is high load brake means of which a maximum braking amount is relatively large; an a brake ECU 44 which is a control device which calculates a braking amount required during travel of the vehicle, and distributes the calculated braking amount to the low load brake means and the high load brake means.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a braking system for a vehicle in which the wheels are attached to the vehicle body via a spring.

  The vehicle has a braking device (brake) for its deceleration and stop. Here, the vehicle is required to have various decelerations, such as low load such as engine braking (regenerative braking) and high load such as sudden braking for collision avoidance.

  Here, for heavy load braking, it has been proposed to provide a large deceleration brake other than the normal brake.

  For example, in Patent Document 1, a material having a high coefficient of friction is pressed against a road surface with an explosive etc. in an emergency to realize deceleration 2G.

  Moreover, in patent document 2, it is made to be able to take out deceleration 4G by driving an anchor on a road surface.

  Furthermore, in patent document 3, in order to prevent fade of the hydraulic brake, a 4-wheel hydraulic brake is used as a main braking, a regenerative brake, a 4-wheel electric brake and an engine brake are prepared as auxiliary braking, and the auxiliary braking is main braking It has been shown to support.

  Further, in a normal vehicle, by connecting the vehicle body and the wheel via a suspension system including a spring, it is difficult to transmit the vibration of the wheel due to the unevenness of the road surface to the vehicle body, and the ride quality is improved. And disk brakes and drum brakes used in many vehicles perform braking by friction with the rotating wheels. These brakes are unsprung brakes because braking is performed on the wheel side. On the other hand, engine braking and regenerative braking by a motor are sprung brakes because braking is performed on the vehicle side. When the unsprung brake is equipped, the unsprung weight increases, the energy of the unsprung vibration due to the unevenness of the road surface increases, and the vibration is easily transmitted to the sprung. Therefore, it is conceivable to reduce the unsprung weight.

Patent No. 5125835 gazette JP, 2016-175580, A Patent No. 5368954

  In Patent Documents 1 and 2, an emergency braking device is mounted in addition to a normal brake so that the deceleration can be increased to 2G to 4G. Therefore, the mass of the whole vehicle increases and the adverse effect on the fuel efficiency is large. Also, although the emergency braking device is mounted on the sprung, the configuration of the unsprung brake has not changed, and the unsprung weight has not been reduced. Although it is necessary to reduce the unsprung weight to improve the push-up due to the unevenness of the road surface, such an effect has not been obtained. In addition, once the emergency braking device is used, there is a problem that it can not be reused unless it takes time to perform recovery work.

  In patent document 3, in order to prevent the fade of the hydraulic brake which is the main braking means, a regenerative brake, an electric brake of four wheels, and an engine brake are prepared as an auxiliary braking means, and this is coordinated and controlled. The weight of the hydraulic and electric brakes located is still large. For this reason, although it is possible to prevent the fade of the hydraulic brake under long-time downhill conditions, the unsprung weight is not lightened, and it is not possible to improve the ride comfort.

  The present invention is a braking system for a vehicle in which the wheels are attached to the vehicle body via a spring, the braking means for braking the wheels under the spring, the low load braking means having a relatively small maximum braking amount, and the spring A braking means for braking the power transmission mechanism provided on the upper side, the high load braking means having a relatively large maximum braking amount, and the braking amount necessary for traveling the vehicle being calculated, and the calculated braking amount being the low load braking means And a controller for distributing to the high load braking means.

  Also, the high load braking means may include a friction type brake.

  And the control device distributes the calculated braking amount among the regenerative braking means, the low load braking means, and the high load braking means. Good.

  In addition, the control device may use the low load braking means and not use the high load braking means when the estimated braking amount is 0.2 G or less.

  Further, the attitude control of the vehicle may be performed by controlling the regenerative braking means and the low load braking means.

  In the present invention, since the high load braking means is provided on the spring, the load of the low load braking means under the spring can be reduced, and the vibration of the vehicle body due to the unevenness of the road surface can be reduced.

It is a figure which shows the area | region map of the deceleration and vehicle speed in use of a general brake. It is a figure which shows the area | region map (a friction type corner brake is dominant) of deceleration and a vehicle speed. It is a figure which shows the area | region map of the deceleration and vehicle speed at the time of introduction of a high load brake, and the role change of a friction type corner brake. It is a figure which shows the area | region map of the deceleration and vehicle speed at the time of making a corner brake into a regenerative type in FIG. It is a mimetic diagram showing an outline of composition of a braking system concerning an embodiment. It is a figure showing an example of composition of braking ECU. It is a flow chart which shows operation in braking ECU. It is a figure which shows the time change (corner brake main part, conditions Z) of a braking amount and distribution. It is a figure which shows the time change (Regenerative braking main body, conditions A, B) of a braking amount and distribution. It is a figure which shows the time change (high load brake intervention, condition C) of braking amount and distribution. It is a figure which shows the time change (high load brake main body, condition D) of a braking amount and distribution. It is a figure which shows the example of a friction type corner brake. It is a figure showing an example of regeneration type corner brake (face gear specification). It is a figure which shows the example (parallel axis specification) of a regenerative type corner brake. It is a figure which shows the example (a friction mechanism addition is shown in FIG. 14) of a regenerative type corner brake. It is a figure which shows arrangement | positioning (a top view) (when there is a power transmission mechanism) of a high load brake. It is a figure which shows arrangement | positioning (a top view) (when there is no power transmission mechanism) of a high load brake. It is a figure which shows the structural example of a high load brake. It is a figure which shows the vehicle attitude control by multiple brake cooperation. It is a figure which shows a calculation model. It is a figure which shows the example and evaluation index of a vibration response. It is a figure which shows the setting conditions of a brake weight. It is a figure which shows the evaluation result (vehicle body up-and-down vibration) of vibration response. It is a figure which shows the evaluation result (tire wheel Fr (front wheel) up-and-down vibration) of a vibration response.

  Hereinafter, embodiments of the present invention will be described based on the drawings. The present invention is not limited to the embodiments described herein.

"Analysis of braking in electric vehicles etc."
There is a vehicle mounted with a drive motor, such as an electric car, and in such a vehicle, the regenerative function of the drive motor is used to brake the vehicle. The types of brakes used mainly for the deceleration and speed in such a vehicle are shown in FIG. Thus, most of the normal braking is occupied by regenerative braking. That is, most of the low G (deceleration) region and the low speed region braking in the medium G region mainly use regenerative braking (for example, A, B, and C in FIG. 1).

  On the other hand, high load braking in the emergency (for example, D in FIG. 1) is required to stop safely, so a structure that can withstand the strictest conditions of high G and high speed is required, and a heavy weight brake is used It will be. Therefore, as shown in FIG. 2, the friction type corner brake becomes dominant, which makes it difficult to reduce the weight of the unsprung brake.

"Overview of the embodiment"
In this embodiment, as shown in FIG. 3, high load braking means which is less frequently used is newly provided, and separation and coordination of low load braking and high load braking can be achieved, thereby enabling weight reduction of the entire braking device. Do. Furthermore, by placing the separated high-load braking means on the upper side (spring) of the suspension system, the unsprung weight is greatly reduced, and the vibration of the vehicle body is reduced against the vibration input due to the unevenness of the road surface, which is comfortable. Improve.

  In addition, as shown in FIG. 4, a corner brake specialized for low load braking is provided with a small regenerative function to improve fuel consumption (power consumption).

"overall structure"
FIG. 5 is a schematic view showing the overall configuration of the braking system according to the present embodiment. In this example, the drive system may use regenerative braking by a drive motor such as a battery electric vehicle (BEV), a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), a fuel cell electric vehicle (FCEV), etc. It is preferable to mount it on a capable vehicle.

  The vehicle 10 has a vehicle body 12 to which four wheels 14 (front wheels 14f, rear wheels 14r) are attached via a suspension (not shown) as a shock absorber including a spring. Here, the vehicle body 12 side of the shock absorber is referred to as sprung and the wheel 14 side as unsprung.

  A power unit 20 including a drive motor is mounted on the vehicle 10, and the driving force from the power unit 20 is transmitted to the drive shaft 22. In this example, the output from one power unit 20 is transmitted to the drive shafts 22 for the left and right two front wheels, so the power unit 20 and the drive shaft 22 are connected via a differential gear as a power transmission mechanism. The drive shafts 22 for the two front wheels are connected to the corresponding two wheels (front wheels) 14 so that the rotation of the drive shaft 22 is transmitted to the wheels (front wheels) 14 and the vehicle 10 travels.

  Further, in this example, the sub power unit 24 is provided on the rear wheel side, and the driving force from this is transmitted to the wheel (rear wheel) 14 through the two drive shafts 22 for the rear wheel. Thus, the vehicle 10 is four-wheel drive.

  Then, each wheel 14 is provided with a corner brake 30 as a low load braking means with a small maximum braking amount. The corner brake 30 brakes the corresponding wheel 14 and is fixed to a non-rotation side pivotally supporting a wheel on the wheel 14 side of the suspension device, and brakes the wheel 14 on the rotation side. Thus, the corner brake 30 is an unsprung member. In the wheel (rear wheel) 14, an electric parking brake (EPB) 32 is also an unsprung member. Although the EPB 32 is basically used in a stopped state, it can also be used for preventing a reverse on a slope or for automatic parking.

  Further, each drive shaft 22 is provided with a high load brake 34 as a high load braking means having a large maximum braking amount. That is, they are disposed at appropriate positions between the drive shaft 22 and the power unit 20 or the sub power unit 24 extended from the wheel hub of the wheel 14 through the joint. The high load brake 34 exerts a large decelerating force, and a brake with a large friction sliding area or the like is employed. The high load brake 34 is a member on the vehicle body 12 side of the suspension system and is a sprung member. The power unit 20 and the sub power unit 24 are regenerative braking means, and these are braking means on a spring.

  A control device for controlling various mounted devices is mounted on the vehicle 10, and the command unit 40 receives signals from various sensors mounted on the vehicle 10, and manages necessary operation control of the vehicle Do. The drive ECU (electronic control unit) 42 controls the outputs of the power unit 20 and the sub power unit 24 in accordance with the required torque calculated from the signal of the accelerator sensor supplied via the command unit 40 or the like. Further, the braking ECU 44 calculates the necessary braking amount in accordance with various signals from the command unit 40, and determines the sharing of regeneration in the corner brake 30, the EPB 32, the high load brake 34, the power unit 20, and the sub power unit 24, Control these braking amounts.

  FIG. 6 shows a specific configuration example of the braking ECU 44. As shown in FIG. The sensors include a wheel speed sensor 60, front and rear G sensors 62, gyro sensors 64, left and right G sensors 66, and weather information sensor 68. The vehicle speed estimation unit 70 estimates the vehicle speed based on the signals of the wheel speed sensors 60. The slope gradient estimation unit 72 calculates the road gradient based on the signal from 62, and the road surface μ estimation unit 74 calculates the friction of the road surface based on the signal from the weather information sensor 68. Further, the vehicle attitude estimation unit 76 estimates the vehicle attitude based on signals from the gyro sensor 64 and the left and right G sensor 66.

  In addition to the vehicle speed from the vehicle speed estimation unit 70, the slope from the slope gradient estimation unit 72, the road surface μ from the road surface μ estimation unit 74, and the vehicle attitude from the vehicle attitude estimation unit 76, a map from GPS (global positioning system) 80 The target deceleration estimation unit 90 is supplied with ambient information such as position information, brake operation information from the brake operation detection unit 82, inter-vehicle distance from the ambient information detection unit 84, approaching speed (relative speed) and the like.

  The target deceleration estimation unit 90 calculates a target deceleration based on the various information supplied. Basically, the deceleration is determined according to the amount of brake operation, but the collision risk is determined from the distance between the vehicle and the relative speed, etc., and the braking amount according to the collision risk is also calculated. The road slope, the road surface μ and the like are used to correct the braking amount based on the braking condition of the brake, and the vehicle posture is used to control the vehicle posture by adjusting the braking amounts of the four wheels.

  The calculated target deceleration is supplied to the braking load determination unit 92. The braking load determination unit 92 determines that the high load brake 34 is to be driven when the supplied target deceleration exceeds the set threshold. Further, the determination result of the braking load determining unit 92 and the target deceleration are supplied to the braking distribution setting unit 94, and the braking distribution setting unit 94 determines the distribution of the high load brake 34, the regenerative brake 36, the EPB 32, and the corner brake 30. , Output the instruction. The regenerative brake 36 is a braking force generated by regeneration in the power unit 20 and the sub power unit 24.

  Furthermore, when it is determined in the ABS (anti-lock brake system) operation determination unit 96 that braking for preventing slip is necessary, the corner brake 30 is controlled in the same manner as normal ABS. Furthermore, when attitude control is required, the ESC (side slip prevention device) operation determination unit 98 individually controls the corner brakes 30 to control the vehicle attitude.

  The process at the time of braking in the braking ECU 44 will be described based on the flowchart of FIG. 7. First, it is determined whether there is a braking request (S11). If this determination is NO, the process about damping | braking is unnecessary and this determination is repeated.

  Here, the braking request includes an operation by a driver's braking operation and an automatic braking request determined from signals from various sensors. That is, even if the brake operation detection unit 82 does not perform the brake operation, a request for automatic braking is issued when it is determined that it is necessary from the peripheral information such as the inter-vehicle distance and the approaching speed.

  When a braking request is issued, the vehicle speed, the slope gradient, the road surface μ, the state of the vehicle attitude, etc. are acquired (S12), and the target deceleration (required braking amount) is calculated based on the acquired information.

  Next, in order to obtain the calculated required braking amount, it is judged whether or not the low load braking means can cope with it (S13). If the determination in S13 is NO, the high load brake 34 is required, and a command to operate the high load brake 34 is issued (S14). Here, at this time, the regenerative brake 36 and the corner brake 30 are also used in coordination. Furthermore, it is determined whether ABS or ESC is necessary (S15), and if it is determined that it is necessary, an operation command for one or both of ABS and ESC is output (S16). Therefore, large deceleration by the high load brake 34, slip prevention control (ABS), and attitude control (ESC) are performed (S16). The ABS and the ESC are performed by controlling the corner brake 30.

  On the other hand, if the determination in S13 is YES and the required braking amount is within the range of normal braking (low load braking is possible for braking), an instruction of normal braking (corner brake 30 and regenerative brake 36) is issued. Further, it is determined whether the operation of the ABS or the ESC is necessary (S18), and if it is determined that the ABS or the ESC is required, a command to operate the required one of the ABS and the ESC is issued (S19). Then, optimization of the regenerative brake 36 and the corner brake 30 is simultaneously performed, and a command of these operations is generated (S20). In S20, the EPB 32 is also cooperatively controlled as needed. The process ends at S16 and S20, but this loop is repeated until the vehicle is stopped at an arbitrary sampling interval.

"Pattern of braking"
FIG. 8 shows a change in the amount of braking with respect to time when the braking load is small and sufficient braking can be performed only by the corner brake 30 as in Z of FIG. After reaching the required braking amount in a short time, it changes at a constant deceleration, and when decelerating near the stop, the friction function of the EPB 32 operates and stops gently, and stops and parks using the lock pin if necessary. Enter the state.

  FIG. 9 shows a change in the amount of braking when using the regenerative brake 36 utilizing the power unit 20 (24) as shown in A and B of FIG. The position in the braking map of deceleration and vehicle speed at the initial stage of braking is determined to be mainly the regenerative brake 36, and coordinated control with the corner brake 30 is performed so that the braking amount by the regenerative brake 36 becomes as large as possible. Here, in the drawing, the distribution of the regenerative brake 36 and the corner brake 30 remains constant from the start to the end of the braking, but the constant ratio is not limited. In addition, if the regenerative type is used for the corner brake 30, the one with high regeneration efficiency by speed is selected and changed, and control is performed so as to suppress the discomfort of switching of the braking amount distribution.

  FIG. 10 corresponds to the boundary area where the high load brake 34 is activated in the braking map, as shown in C of FIG. In this case, the regenerative brake 36 acts as a main body, and the high load brake operates to compensate for the shortage of the braking amount applied to the corner brake 30.

  In FIG. 11, as shown in D of FIG. 4, the high load brake 34 is actuated because the high load brake 34 is the main region in the braking map. Here, control is performed such that the high load brake 34 is increased to the required braking amount after the braking amounts of the corner brake 30 and the regenerative brake 36 have risen.

  Here, if more urgentness is required at the upper right of the braking map, control may be performed to maximize the rising time of the high load brake 34 from the braking start time.

"Configuration of corner brake"
FIG. 12 shows an embodiment of a friction type corner brake 30. As shown in FIG. Inside the tire wheel 14a of the wheel 14 (vehicle side), a donut-like friction disc 110 is provided. The friction disc 110 has a radius as large as possible. As a result, the radial position at which the friction material (brake pad) is pressed against the friction disc 110 can be made as large as possible, and the design maximum value of the pressure can be lowered. Therefore, downsizing of the caliper 112 for pressing the brake pad against the friction disc 110 and thinning of the friction disc 110 can be achieved. Therefore, the unsprung corner brake 30 can be lightened. As a drive system of the pressing piston in the caliper 112, a conventional hydraulic system or an electromechanical system can be adopted, and this drive mechanism can be incorporated in the space in the tire wheel 14a.

  FIG. 13 is a configuration example of the regenerative corner brake 30. As shown in FIG. A disk 120 provided with a face gear instead of the friction disk 110 of FIG. 12 is attached, the pinion gear 122 is disposed at an appropriate position not interfering with surrounding parts, and rotation of the pinion shaft is performed with a high reduction ratio To generate electric power by the regenerative load device (generator) 124 and charge the secondary battery mounted on the vehicle 10. The regenerative load device 124 is not particularly limited, but an SR motor (switched reluctance motor) having an iron core with a salient pole on the rotor side can be used inexpensively and generally. The command value of the excitation current is determined from the rotational speed of the pinion shaft and the necessary braking torque, and the energization timing is controlled to realize the required torque. In the figure, the rotation axis of the regenerative load device 124 passes through the rotation axis of the tire and is positioned outside the tire wheel, but the rotation axis of the pinion does not intersect with the rotation axis of the tire even if disposed inside the tire wheel. Also good. The regenerative load device 124 is fixed to a suspension (suspension device) component such as a knuckle.

  FIG. 14 shows an example in which a gear 122a such as a flat tooth or a helical tooth is formed on the inner periphery of the disk 120 attached to the tire wheel 14a. The pinion shaft of the regenerative load device 124 is disposed parallel to the rotation axis of the wheel 14. Here, power transmission is performed by meshing of gears, but power may be transmitted by bringing a surface-processed roller having a large coefficient of friction into contact.

  In FIG. 15, the friction material pressing portion 126 is provided in addition to the regenerative load device 124 of FIG. The friction material pressing portion 126 presses the friction material 126 a against the disc 120 from the inside of the vehicle. In particular, the friction material 126a is pressed against the pressing portion 120a of the disc 120 by driving the motor with the electric power obtained by the regeneration of the regenerative load device 124 or the like, and braking is performed. Thereby, a larger decelerating force can be obtained. Moreover, it is not necessary to charge a distant secondary battery, and the range of the braking force control can be expanded, and in particular, the braking force in the vicinity of the stop can be secured. Note that power may be stored in the capacitor and power until stopping may be secured.

"Configuration of high load brake"
The high load brake 34 may be sprung on the drive shaft 22 extending from the tire wheel hub to make the unsprung more light.

  16 (a), (b) and (c) are arrangement examples of the high load brake 34 when there is a power transmission mechanism (left and right split device: differential gear) 130. FIG.

  In (a), the high load brake 34 is provided on the drive shaft between the wheel hub and the power transmission mechanism 130. In (b), the high load brake 34 is provided inside the power transmission mechanism 130. In (c), the high load brake 34 is disposed between the power transmission mechanism 130 and the power unit 20 (24).

  The high load brake 34 is generally constituted by a combination of dry friction materials, but when disposed inside the power transmission mechanism 130 as shown in FIG. Wet friction materials are also useful because they can utilize water.

  FIG. 17 shows the case where the power transmission mechanism 130 is not in the vicinity of the wheel 14, and a short shaft (rotational shaft) 132 is provided, and the high load brake 34 is installed on the shaft 132. The rear side of the FF car and the front side of the RR car correspond. In addition, since the high load brake 34 can not be used in combination with the drive shaft, it is preferable to apply it only when it is necessary to distribute the braking force.

  The high load brake 34 can discharge the battery in a short time by offsetting the driving force. For this reason, when there are many downhill roads in the future traveling route, the battery is discharged in advance by using the high load brake 34, whereby regenerative braking can be effectively used on the downhill road.

"Example of construction of high load brake"
A structural example of the high load brake 34 is shown in FIG. The rotation shaft 140 in FIG. 18 corresponds to the drive shaft 22 or the like that transmits power to the tire wheels in FIGS. 16 and 17.

  The high load brake 34 is configured as a multiple disc clutch of the transmission AT or a multiple disc clutch for shifting of a race vehicle.

  On the rotation side, there are provided a rotation-side guide body 142 and an axially slidable donut-shaped friction plate 144 which is slidable in the axial direction. On the other hand, on the fixed side, a donut-shaped friction plate 148 axially slidable with the fixed side guide body 146, a pressure plate 150 for pressing the friction plates 144 and 148 in the axial direction, and the pressure plate 150 in the axial direction It is comprised from the return spring 152 pulled back.

  In FIG. 18, the upper side represents the non-braking state, and the lower side represents the braking state. That is, when the high load brake 34 is used, the pressing plate 150 is pressed to the right from the left side in the drawing, and the donut shaped friction plates 144 and 148 on the fixed side and the rotation side are rubbed to generate a braking force. Since the braking force can be defined by the pressing force and temperature dependent μ if the friction plates 144 and 148 are determined, sensing them and adjusting the pressing force to control the decelerating torque of the high load brake 34 Can.

  The number, size, and material of the friction plates 144 and 148 are selected and installed in accordance with the required range of braking force. The friction plates 144 and 148 may be selected from a composite of cast iron and a resin matrix, stainless steel and sintered material, carbon and ceramic / carbon, cobalt-based thermal spray material and cemented carbide powder mixed material.

  When the cooling system of the power transmission mechanism can be used as shown in FIG. 16 (b), the friction material itself may be touched with the liquid like AT, but a heat generating material is installed on the fixed side and from the casing side. You may cool it.

  The pressing method of the pressing plate 150 may be ON / OFF control by magnetizing / demagnetizing, but if it is desired to control the braking torque continuously, a cam or screw mechanism is used or a hydraulic chamber is provided. The pressure and the displacement of the pressing plate 150 may be controlled.

"Control of braking attitude"
FIG. 19 shows an example of controlling the attitude of the vehicle, such as ABS and ESC. (A) is a case where a clockwise yaw moment is created to stabilize the vehicle posture when a counterclockwise yaw movement starts to occur. Here, a large braking force is generated by the regenerative brake 36 and the high load brake 34 (thick arrow), a small braking force is generated by the corner brake 30 (thin arrow), and the braking force of the left and right wheels by the corner brake 30 of the front and rear wheels Control the yaw moment.

  (B) is the same as the state of (a), but in the regenerative corner brake 30, an inverter is provided to enable drive control as well. In this case, a yaw moment can be more positively applied to stabilize the vehicle posture by applying a driving force in the traveling direction (left fine arrow) to the left side in the drawing.

  Furthermore, conventionally, the rotation speed (speed) of the wheel 14 was sensed to control the braking torque by the brake, but if the driving component of the corner brake 30 is used, the braking torque by the regenerative brake 36 and the high load brake 34 Can be controlled, and speed control can be performed by the driving force of the corner brake to suppress the locking of the wheel (dangerous behavior).

"Estimate of effect"
The effect of the ride quality improvement according to the present embodiment is estimated. The target model is shown in FIG. The vehicle body 12 is supported by the front and rear two wheels 14 via a suspension and a shock absorber. The weight mub, the bounce vertical movement Xub, the inertia Iub, and the pitching rotation θub are used for the vehicle body 12. For the high load brake 34, weights mf and mr, up and down movement Xf and Xr, and distances from the center of gravity are Lf and Lr. Also. Suspension and shock absorber spring constants ksf, ksr, damping coefficients csf, csr, weights of wheels 14 mtf, mtr, spring constants ktf, ktr, damping coefficients ctf, ctr, distance from the center of gravity of the two wheels 14 to Ltf, Let it be Ltr. The subscript f indicates the front (front) and r indicates the rear (rear).

  Then, in this model, the vehicle body 12 performs movements of bounce Xub and pitching θub, and the response of the front wheel and the response of the vehicle body are evaluated when the front wheel receives displacement input in the vertical direction due to the unevenness of the road surface.

  In the evaluation, as shown in FIG. 21, the ratio (Dot, Dob) of the fluctuation value of the displacement response of the front wheel (unsprung portion) mtf and the displacement response of the vehicle center of gravity position mub to the input amplitude Din of the road surface protrusion Use Dot / Din, Dob / Din). The smaller the ratio of response to input, the better the performance.

  FIG. 22 shows the setting conditions of the brake weight to be compared side by side. The diameter of the circle corresponds to the weight ratio of the brake, and the two left and right wheels are compared. Under normal conditions, the weight of the corner brake 30 under the Fr spring is 24 kg, the brake weight under the Rr spring is 12 kg, and there is no high load brake 34 on the spring. The regenerative brake 36 is considered to be the common power unit 20 and sub power unit 24, and includes the weight of the vehicle body 12. Conditions C1, C2, C3 and C3a are cases where the unsprung corner brake 30 is lightened and the high load brake 34 is disposed on the sprung. C1 arranges the high load brake 34 only on the Fr side, C2 arranges the high load brake 34 only on the Rr side, and C3 places the high load brake 34 on both the Fr side and the Rr side. is there. The sum of the corner brake 30 and the high load brake 34 is about 17% lighter than the normal in C1, C2, and C3, and C3a is the same as in the normal.

  The amplitude reduction effect is shown in FIG. 23 and FIG. FIG. 23 shows the vertical movement of the vehicle body, and FIG. 24 shows the vertical movement of the front wheel. The vertical axis is normalized so that the normal is 1 in the vibration amplitude ratio. It can be confirmed that vibration is reduced more than normal under any condition in which the unsprung corner brake 30 is lightened and the high load brake 34 is disposed on the sprung. When there is an input on the front wheel, it can be seen that vibration can be reduced if the weight on the front wheel side is larger than when the weight on the rear wheel side is large, and that vibration will be reduced if the total weight is small. .

<Effect of the embodiment>
According to the present embodiment, the high G dedicated high load braking means (high load brake 34), which is less frequently used, is disposed on the spring, whereby the low load braking means (corner brake 30) mounted on the corner wheels Can be significantly reduced, so that the followability to the road surface of the wheel can be improved with respect to the vibration input due to the unevenness of the road surface, and the sway of the vehicle body can be reduced and the comfort can be improved.

  Since the unsprung mass inertia can be made smaller than that of the conventional vehicle, even if the wheel 14 is forced to vibrate by displacement due to the unevenness of the road surface, the vibration input to the sprung mass (car body) can be suppressed small, about several Hz It is possible to suppress the shaking of the car body. In addition, since the unsprung mass inertia can be reduced, vibration damping can be quickened without changing the suspension characteristics, and it is possible to follow the unevenness of the road surface by suppressing the feeling of rattling of the tire wheel. Furthermore, since the polar inertia moment around the rotation axis is reduced, acceleration / deceleration control of the wheel is facilitated, which can contribute to improvement of the passenger's comfort.

DESCRIPTION OF SYMBOLS 10 vehicles, 12 vehicle bodies, 14 wheels, 14a tire wheels, 20 power units, 22 drive shafts, 24 sub power units, 30 corner brakes, 32 electric parking brakes, 34 high load brakes, 36 regenerative brakes, 40 heads, 60 wheel speed sensors , 62 front and rear G sensor, 64 gyro sensor, 66 left and right G sensor, 68 weather information sensor, 70 vehicle speed estimation unit, 72 slope gradient estimation unit, 74 road surface μ estimation unit, 76 vehicle attitude estimation unit, 82 brake operation detection unit, 84 Ambient information detection unit, 90 target deceleration estimation unit, 92 braking load determination unit, 94 braking distribution setting unit, 96 ABS operation determination unit, 98 ESC operation determination unit, 110 friction disk, 112 caliper, 120 disk, 120a pressing unit, 122 pinion gear, 122a gear, 124 Regeneration type load device, 126 friction material pressing part, 126a friction material, 130 power transmission mechanism, 132 shaft, 140 rotation shaft, 142 rotation side guide body, 144, 148 friction plate, 146 fixed side guide body, 150 pressure plate, 152 Return spring.

Claims (5)

A braking system for a vehicle in which the wheels are attached to the vehicle body via a spring,
A braking means for braking the wheel under a spring, the low load braking means having a relatively small maximum braking amount;
A braking means for braking a power transmission mechanism provided on a spring, the high load braking means having a relatively large maximum braking amount,
A control device that calculates a braking amount necessary for traveling the vehicle and distributes the calculated braking amount to the low load braking means and the high load braking means;
Have
Braking system. The braking system according to claim 1, wherein
High load braking means include friction brakes,
Braking system. The braking system according to claim 1 or 2,
further,
Regenerative braking means using a drive motor provided on the spring;
Have
The control device distributes the calculated braking amount to the regenerative braking means, the low load braking means, and the high load braking means.
Braking system. The braking system according to any one of claims 1 to 3, wherein
The controller uses the low load braking means and does not use the high load braking means when the estimated braking amount is 0.2 G or less.
Braking system. The braking system according to claim 3 or 4, wherein
By controlling the regenerative braking means and the low load braking means, attitude control of the vehicle is performed.
Braking system.