JP4680802B2 - Brake device for vehicle - Google Patents

Description

  The present invention relates to a brake device in a vehicle in which a damping force of a damper of a suspension device can be changed.

In a BBW (brake-by-wire) type brake device that converts a brake pedal operation by a driver into an electric signal and brakes a wheel with a brake fluid pressure generated by driving an actuator with the electric signal, Patent Document 1 below discloses a variable jumping amount, which is an amount by which a braking force is suddenly raised with respect to an increase in pedaling force.
JP-T-2001-509753

  By the way, in a vehicle that can variably control the damping force of the damper of the suspension device, the damping force of the damper is set high during sports driving to make the suspension device hard, and the damping force of the damper is set low during normal driving. However, if the characteristics of the braking force of the brake device are changed in relation to the control of the damping force of the damper, the brake feeling during sports driving and normal driving can be reduced. It is thought that it can be further increased.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a brake device capable of obtaining braking characteristics suitable for both sports running and normal running.

  In order to achieve the above object, according to the first aspect of the present invention, in the vehicle in which the damping force of the damper of the suspension device can be changed, the braking force is suddenly raised with respect to the increase in the depression force of the brake pedal. A braking device for a vehicle is proposed, wherein a jumping amount, which is a quantity, is changeable, and the jumping amount increases with an increase in damping force of the damper.

  According to the configuration of the first aspect of the present invention, jumping is an amount that suddenly raises the braking force with respect to an increase in the depressing force of the brake pedal at the time of sports driving in which the damping force of the damper is set high to improve the turning performance of the vehicle. Even if the amount is set to a large value and the start-up of the braking force suitable for sports driving is ensured, the damping force of the damper is set high, so that nose diving of the vehicle body at the initial stage of braking can be suppressed. Further, even when the damping force of the damper is set to be low during normal driving for improving the ride comfort of the vehicle, the nose dive of the vehicle body at the initial stage of braking can be suppressed because the jumping amount is set small.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 5 show an embodiment of the present invention. FIG. 1 is a hydraulic system diagram at the time of normal operation of the vehicle brake device, and FIG. 2 is a hydraulic system diagram at the time of abnormality corresponding to FIG. 3 is a front view of the vehicle suspension device, FIG. 4 is an enlarged sectional view of the variable damping force damper, and FIG. 5 is a graph showing the relationship between the damping force of the damper and the jumping amount.

  As shown in FIG. 1, the tandem master cylinder 10 includes first and second output ports 12 a and 12 b that output brake fluid pressure in accordance with a pedaling force that a driver steps on the brake pedal 11. The output port 12a is connected to the disc brake devices 13 and 14 for the left front wheel and the right rear wheel, for example, and the second output port 12b is connected to the disc brake device for the right front wheel and the left rear wheel, for example. In FIG. 1, only one brake system connected to the first output port 12a is shown, and the other brake system connected to the second output port 12b is not shown, but the structure of one and the other brake system is Substantially the same. Hereinafter, one brake system connected to the first output port 12a will be described.

  The first output port 12a of the master cylinder 10 and the wheel cylinder 15 of the disc brake device 13 of the front wheel are connected by liquid passages 17a to 17f, and the liquid passages 17g to 17j branched from the liquid passages 17c and 17d are rear wheels. Are connected to the wheel cylinder 16 of the disc brake device 14.

  A pedal force shut-off valve 18 which is a normally open electromagnetic valve is disposed between the liquid passages 17b and 17c, and a front wheel braking force generating means 19F is disposed between the liquid passages 17d and 17e. The braking force generation means 19F includes a cylinder 20 disposed between the liquid passages 17d and 17e, and a piston 21 slidably fitted into the cylinder 20 is driven by an electric motor 22 via a speed reduction mechanism 23. Thus, the brake fluid pressure can be generated in the fluid chamber 24 formed on the front surface of the piston 21.

  Similarly, a rear wheel braking force generating means 19R is disposed between the liquid passages 17h and 17i. The braking force generating means 19R includes a cylinder 20 disposed between the liquid passages 17h and 17i, and a piston 21 slidably fitted into the cylinder 20 is driven by an electric motor 22 via a speed reduction mechanism 23. Thus, the brake fluid pressure can be generated in the fluid chamber 24 formed on the front surface of the piston 21.

  A stroke simulator 25 connected to the downstream end of the liquid passages 17k to 17n branched from the liquid passages 17a and 17b is a cylinder 26 slidably fitted with a piston 28 biased by a spring 27. A liquid chamber 29 formed on the side opposite to the spring 27 of the piston 28 communicates with the liquid path 17n. A reaction force permission valve 30 that is a normally closed electromagnetic valve is disposed between the liquid passages 17m and 17n. Further, liquid passages 17o and 17p branched from between the liquid passages 17g and 17h communicate with the reservoir 31 of the master cylinder 10, and an atmospheric valve 32 which is a normally closed electromagnetic valve is disposed between the liquid passages 17o and 17p. .

  The BBW electronic control unit Ub (see FIG. 3) that controls the operation of the pedal force cutoff valve 18, the reaction force permission valve 30, the atmospheric valve 32, and the electric motors 22 and 22 of the braking force generation means 19F and 19R includes a master cylinder 10. The hydraulic pressure sensor Sa for detecting the generated hydraulic pressure, the hydraulic pressure sensor Sb for detecting the brake hydraulic pressure transmitted to the front disc brake device 13, and the brake hydraulic pressure transmitted to the rear disc brake device 14. Is connected to the hydraulic pressure sensor Sc.

  As shown in FIG. 3, the suspension device S that suspends the wheels W of a four-wheeled vehicle includes a suspension arm 43 that supports a knuckle 42 in a vertically movable manner on a vehicle body 41, and a variable damping that connects the suspension arm 43 and the vehicle body 41. A force damper 44 and a coil spring 45 connecting the suspension arm 43 and the vehicle body 41 are provided. The variable damping force damper electronic control unit Ud that controls the damping force of the damper 44 includes a signal from the sprung acceleration sensor Sd that detects the sprung acceleration and a damper displacement sensor Se that detects the displacement (stroke) of the damper 44. , A signal from the steering angle sensor Sf that detects the steering angle of the vehicle, a signal from the lateral acceleration sensor Sg that detects the lateral acceleration of the vehicle, and a signal from the longitudinal acceleration sensor Sh that detects the longitudinal acceleration of the vehicle And a signal from a vehicle speed sensor Si for detecting the vehicle speed.

  As shown in FIG. 4, the damper 44 includes a cylinder 51 whose lower end is connected to the suspension arm 43, a piston 52 that is slidably fitted to the cylinder 51, and an upper wall of the cylinder 51 that extends upward from the piston 52. And a free piston 54 slidably fitted to the lower part of the cylinder 51, and is partitioned by the piston 52 inside the cylinder 51. An upper first fluid chamber 55 and a lower second fluid chamber 56 are partitioned, and a gas chamber 57 in which a compressed gas is sealed in a lower portion of the free piston 54 is partitioned.

  A plurality of fluid passages 52a are formed in the piston 52 so that the upper and lower surfaces thereof communicate with each other, and the first and second fluid chambers 55 and 56 communicate with each other through the fluid passages 52a. The magnetorheological fluid enclosed in the first and second fluid chambers 55 and 56 and the fluid passage 52a is a dispersion of magnetic particles such as iron powder in a viscous fluid such as oil. By aligning the magnetic fine particles along the magnetic field lines, it is difficult for the viscous fluid to flow, and the apparent viscosity increases. A coil 58 is provided inside the piston 52, and energization to the coil 58 is controlled by the variable damping force damper electronic control unit Ud. When the coil 58 is energized, a magnetic flux is generated as indicated by an arrow, and the viscosity of the magnetorheological fluid changes due to the magnetic flux passing through the fluid passages 52a.

  When the damper 44 contracts and the piston 52 moves downward relative to the cylinder 51, the volume of the first fluid chamber 55 increases and the volume of the second fluid chamber 56 decreases. Passes through the fluid passage 52a of the piston 52 and flows into the first fluid chamber 55. Conversely, when the damper 44 extends and the piston 52 moves upward relative to the cylinder 51, the volume of the second fluid chamber 56 increases. Since the volume of the first fluid chamber 55 is reduced, the magnetorheological fluid in the first fluid chamber 55 passes through the fluid passage 52a ... of the piston 52 and flows into the second fluid chamber 56. At that time, the fluid passage 52a The damper 44 generates a damping force due to the viscous resistance of the magnetorheological fluid passing through.

  At this time, when the coil 58 is energized to generate a magnetic field, the apparent viscosity of the magnetorheological fluid existing in the fluid passage 52a of the piston 52 increases, making it difficult to pass through the fluid passage 52a. Damping force increases. The amount of increase in the damping force can be arbitrarily controlled by the magnitude of the current supplied to the coil 58.

  When a shocking compressive load is applied to the damper 44 to reduce the volume of the second fluid chamber 56, the free piston 54 descends while the gas chamber 57 is contracted to absorb the impact. When a shocking tensile load is applied to the damper 44 and the volume of the second fluid chamber 56 increases, the free piston 54 rises while the gas chamber 57 is expanded to absorb the impact. Further, when the piston 52 is lowered and the volume of the piston rod 53 accommodated in the cylinder 51 is increased, the free piston 54 is lowered so as to absorb the increase in the volume.

  Thus, the variable damping force damper electronic control unit Ud has the sprung acceleration detected by the sprung acceleration sensor Sd, the damper displacement detected by the damper displacement sensor Se, the steering angle detected by the steering angle sensor Sf, and the lateral acceleration sensor Sg. Based on the detected lateral acceleration, the longitudinal acceleration detected by the longitudinal acceleration sensor Sh, and the vehicle speed detected by the vehicle speed sensor Si, the damping force of a total of four dampers 44 of each wheel W is controlled individually, thereby Ride comfort control, such as skyhook control that suppresses vehicle swaying when climbing over unevenness of the vehicle and enhances ride comfort, and steering stability control that suppresses rolling during turning of the vehicle and pitching during sudden acceleration and deceleration of the vehicle Are selectively executed according to the driving state of the vehicle.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  In the normal state shown in FIG. 1, the pedal force shut-off valve 18, the reaction force permission valve 30 and the atmospheric valve 32 are energized by a command from the BBW electronic control unit Ub, the pedal force shut-off valve 18 is closed, and the master cylinder 10 and the disc The communication between the brake devices 13 and 14 is cut off, the reaction force permission valve 30 is opened, the master cylinder 10 and the stroke simulator 25 are communicated, and the atmospheric valve 32 is opened. In this state, when the driver depresses the brake pedal 11 and the master cylinder 10 generates brake fluid pressure, the fluid pressure sensor Sa detects the brake fluid pressure in the fluid passage 17k closed by the pedal force shut-off valve 18. The BBW electronic control unit Ub operates the braking force generating means 19F and 19R for the front wheels and the rear wheels so as to generate a hydraulic pressure corresponding to the brake hydraulic pressure detected by the hydraulic pressure sensor Sa in the hydraulic passages 17f and 17j.

  As a result, the driving force of the electric motor 22 of the braking force generating means 19F for the front wheels is transmitted to the piston 21 via the speed reduction mechanism 23, and the brake fluid pressure generated in the fluid chamber 24 of the cylinder 20 is transmitted via the fluid passages 17e and 17f. Thus, the front wheel is braked by being transmitted to the wheel cylinder 15 of the disc brake device 13. At this time, the brake fluid pressure of the fluid passage 17f is detected by the fluid pressure sensor Sb, and the brake fluid pressure of the electric motor 22 is adjusted so that the brake fluid pressure becomes a value corresponding to the brake fluid pressure detected by the fluid pressure sensor Sa of the fluid passage 17k. The operation is feedback controlled.

  Similarly, the driving force of the electric motor 22 of the braking force generating means 19R for the rear wheels is transmitted to the piston 21 via the speed reduction mechanism 23, and the brake fluid pressure generated in the fluid chamber 24 of the cylinder 20 passes through the fluid passages 17i and 17j. To the wheel cylinder 16 of the disc brake device 14 to brake the rear wheel. At this time, the brake fluid pressure in the fluid passage 17j is detected by the fluid pressure sensor Sc, and the electric motor 22 is adjusted so that the brake fluid pressure becomes a value corresponding to the brake fluid pressure detected by the fluid pressure sensor Sa in the fluid passage 17k. The operation is feedback controlled.

  When the piston 21 in the cylinder 20 is slightly advanced by the electric motor 22, the communication between the liquid chamber 24 and the liquid path 17d (or the liquid path 17h) is cut off, so that the brake hydraulic pressure generated by the cylinder 20 is reduced. There is no risk of escape to the reservoir 31 via the atmospheric valve 32 provided between 17o and 17p.

  By the way, in the normal state described above, the pedal force shut-off valve 18 is kept closed unless an abnormal state such as a power failure occurs. Conventionally, the brake pads of the disc brake devices 13 and 14 are worn and the cylinders are worn. Even if the volume of the fluid passages 17e and 17f or the fluid passages 17i and 17j between the discs 20 and 20 and the disc brake devices 13 and 14 is increased, the corresponding brake fluid cannot be replenished from the reservoir 31, and the wheel cylinder There is a possibility that a problem that the drag of 15, 16 cannot be reduced occurs.

  However, when the pistons 21 and 21 are retracted in the cylinders 20 and 20, the fluid chambers 24 and 24 communicate with the reservoir 31 through the open air valve 32, and therefore, due to wear of the brake pads of the disc brake devices 13 and 14. Insufficient brake fluid can be replenished from the reservoir 31, and dragging of the wheel cylinders 15 and 16 when the braking force is released can be reduced.

  Further, when the driver depresses the brake pedal 11 and the master cylinder 10 generates the brake fluid pressure at the normal time, the brake fluid pressure is transmitted to the fluid chamber 29 of the stroke simulator 25 and the piston 28 resists the elastic force of the spring 27. Thus, a reaction force against the depression of the brake pedal 11 can be generated. As a result, although the disc brake devices 13 and 14 are actually operated by the driving force of the electric motors 22 and 22, the disc brake devices 13 and 14 are operated by the driver's stepping force. The operation feeling can be obtained.

  On the other hand, when the power supply is lost due to battery disconnection or the like, the pedal force shut-off valve 18 is opened as shown in FIG. 2 so that the master cylinder 10 and the disc brake devices 13 and 14 communicate with each other. The valve 30 is closed and communication between the master cylinder 10 and the stroke simulator 25 is cut off. The air valve 32 is closed and communication between the master cylinder 10 and the reservoir 31 is cut off. As a result, the brake fluid pressure generated by the master cylinder 10 when the driver depresses the brake pedal 11 is applied to the wheel cylinder 15 of the disc brake device 13 of the front wheel via the opened pedal force cutoff valve 18 and the braking force generating means 19F. It is transmitted to the wheel cylinder 16 of the disc brake device 14 for the rear wheel via the pedaling force cutoff valve 18 and the braking force generating means 19R that are opened, and the front wheel and the rear wheel are braked.

  At the same time, since the communication between the stroke simulator 25 and the master cylinder 10 is blocked by closing the reaction force permission valve 30, the stroke simulator 25 stops its function. As a result, it is possible to prevent the stroke of the brake pedal 11 from increasing unnecessarily and giving the driver an uncomfortable feeling, and the brake hydraulic pressure generated by the master cylinder 10 is not absorbed by the stroke simulator 25 and the wheel. It is transmitted to the cylinders 15 and 16, and the braking force can be generated with high responsiveness.

  Thus, even if the power supply fails and the pedal force shut-off valve 18, the reaction force permission valve 30, the atmospheric valve 32, and the braking force generating means 19F and 19R become inoperable, the driver steps on the brake pedal 11 to operate the master cylinder. The front and rear wheel cylinders 15 and 16 can be operated without any trouble by the brake fluid pressure generated by the vehicle 10, and thereby the vehicle can be stopped more safely by braking the front and rear wheels in the event of an abnormality. In addition, when normal, the left and right front wheels and the left and right rear wheel braking forces can be individually controlled.

  The BBW electronic control unit Ub that controls the above-described BBW brake device and the above-described variable damping force damper electronic control unit Ud that controls the damper 44 are connected to each other, and are associated with the damping force of the damper 44. The jumping amount of the BBW brake device is controlled.

  As shown in FIG. 5, when the brake pedal 11 is depressed, no braking force is generated until the pedaling force reaches a predetermined value, and a certain amount of braking force is generated at the moment when the pedaling force reaches the predetermined value. This constant amount of braking force is defined as the jumping amount. As the pedal effort further increases from the predetermined value, the braking force increases linearly in accordance with the increase.

  As apparent from FIG. 5 and Table 1, in this embodiment, the smaller the damping force of the damper 44 is set (that is, the softer the suspension device S) and the smaller the vehicle speed is, the smaller the jumping amount is set. Further, the jumping amount is set larger as the damping force of the damper 44 is set larger (that is, the suspension device S is harder) and the vehicle speed is larger.

  The jumping amount of the braking force generated in the wheel cylinders 15 and 16 can be arbitrarily set by changing the operation timing and the operation amount of the braking force generation means 19F and 19R of the BBW type brake device that operates in response to the depression of the brake pedal 11. Can be controlled.

  When the damping force of the damper 44 is large and the vehicle speed is high, it is during sports driving that emphasizes the turning performance of the vehicle. During this sports driving, the jumping amount when the brake pedal 11 is depressed is set to be larger. The responsiveness of power becomes high and the brake feeling becomes good. In general, when the jumping amount is set large, the braking force suddenly rises as the brake pedal 11 is depressed, so that the phenomenon that the front part of the vehicle body sinks and the rear part rises (nose dive) is likely to occur. Since the damping force of the damper 44 is set to be high (the characteristic of the suspension device S is hard) during sports running, an increase in the nose dive can be suppressed.

  Further, when the damping force of the damper 44 is small and the vehicle speed is low, it is during normal traveling that emphasizes the ride comfort of the vehicle, and during this normal traveling, the jumping amount when the brake pedal 11 is depressed is set to be small. The braking force rises smoothly and the brake feeling becomes good. During this normal running, the damping force of the damper 44 is set low (the characteristics of the suspension device S are soft). However, since the jumping amount is set small, there is no possibility that the nose dive will increase.

  As described above, since the jumping amount is changed in association with the damping force of the damper 44, an unpleasant nose dive is generated at the start of braking even if the braking force is set to be appropriate for each of sports running and normal running. Can be prevented.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the BBW brake device is exemplified, but a brake device having an arbitrary structure can be adopted as long as the jumping amount can be changed.

  Further, in the embodiment, the variable damping force damper 44 using the magnetorheological fluid is exemplified, but a damper having an arbitrary structure can be adopted as long as the damping force can be changed.

Hydraulic system diagram when the brake system for vehicles is normal Hydraulic system diagram at the time of abnormality corresponding to FIG. Front view of vehicle suspension system Expanded sectional view of variable damping force damper Graph showing the relationship between damper damping force and jumping amount

Explanation of symbols

11 Brake pedal 44 Damper S Suspension device

Claims (1)

In a vehicle in which the damping force of the damper (44) of the suspension device (S) can be changed,
The jumping amount, which is an amount for suddenly raising the braking force with respect to an increase in the pedal force of the brake pedal (11), can be changed, and the jumping amount increases with an increase in the damping force of the damper (44). Brake device for a vehicle characterized by the above.

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