Braking system of an automobile having a variably exhausting pump unit

Disclosed is a braking system of an automobile, which can produce and store an electric power by means of the energy generated when the automobile is braked, thereby increasing efficiency in energy use, and simultaneously which can perform an anti-lock braking function and a traction control function. In the braking system, a master cylinder generates a hydraulic pressure when the brake pedal is pressed. A variably exhausting pump unit performs a pumping operation by the hydraulic pressure from the master cylinder. A control section senses a traveling state of the automobile and controls so that a proper braking force is applied to a wheel of the automobile. A flow control valve providing the variably exhausting pump unit with the braking force. A generating section generates electricity by means of a bypassed hydraulic pressure according to the order of the control section.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a braking system of an automobile, and 
more particularly to a braking system having a variably exhausting pump 
unit which enables the braking system not only to perform a braking 
function but to utilize the energy of hydraulic pressure which is 
generated during the braking and which may be lost without the unit. 
2. The Prior Arts 
It is well-known in the art that a brake is a system for stopping or 
decelerating an automobile being driven. The brake system performs the 
braking function in such a manner that it transforms the kinetic energy of 
a traveling automobile into a heat energy by means of a mechanical 
friction apparatus and radiates the frictional heat into the atmosphere. 
Recently, the automobile is generally equipped with various systems for 
improving its traveling stability, such as an anti-lock braking system 
(ABS) and a traction control system (TCS). The ABS is a system for 
ensuring a strong and stable braking capability by properly controling the 
hydraulic pressure of the brake when the automobile is braked on slippery 
or uneven ground. The TCS is a system for preventing the driving wheels 
from slipping when the automobile is rapidly accelerated to start on 
slippery ground by applying proper braking pressure to the driving wheels 
even when the brake pedal is not stepped on. 
FIG. 1 shows a schematic hydraulic circuit diagram of a conventional 
braking system. As shown, the conventional braking system includes a brake 
pedal 10 arranged under a driver's seat and connected to a master cylinder 
11 which transfers an external force applied to the brake pedal 10. A 
brake booster 12 is arranged between the brake pedal 10 and the master 
cylinder 11 to boost the braking power. One end of a first fluid path 20 
is connected to the master cylinder 11, while a first solenoid valve 30 
for controling the flow of fluid is disposed at the other end of the first 
fluid path 20. The first solenoid valve 30 is connected to a second fluid 
path 21 which extends up to a braking section 70 and is connected through 
a second solenoid valve 31 to a third fluid path 22 branching off from the 
first fluid path 20. A pump 41 driven by a motor 40, a check valve 50, and 
a tank 90 are provided between the third fluid path 22 and the second 
solenoid valve 31. A speed sensor 81 for sensing the braked state of a 
wheel 60 is provided in the braking section 70, and the conventional 
braking system further includes an electronic control unit (ECU) 80 which 
controls the first solenoid valve 30, the second solenoid valve 31, and 
the motor 40, according to signals from the speed sensor 81. 
In operating the conventional braking system as described above, when a 
driver steps on the brake pedal 10, the master cylinder 11 generates a 
hydraulic pressure, which is transferred through the first solenoid valve 
30 to the braking section 70 The hydraulic pressure enables a piston 
installed in a caliper 62 to push a pad toward a disc 61, thereby 
performing the braking function (see FIG. 2). In this case, the fluid or 
oil supplied from the master cylinder 11 through the first fluid path 20 
to the third fluid path 22 is interrupted by the check valve 50, and the 
second solenoid valve 31 also is blocked off. Therefore, the oil is not 
supplied through the second fluid path 21. 
While the braking force is being applied to the wheel 60, the speed sensor 
81 disposed at one side of the wheel 60 senses if the wheel 60 slips. When 
a slip of the wheel 60 is sensed by the speed sensor 81, the ECU 80 closes 
the first solenoid valve 30 to interrupt the supply of oil into the 
braking section 70, opening the second solenoid valve 31 to make the oil 
having been supplied in the braking section 70 be retrieved into the tank 
90 through the second fluid path 21 and the second solenoid valve 31, 
thereby decreasing the braking force applied to the wheel 60. 
The decrease of braking force by the above process eliminates the slip of 
the wheel 60, and then the speed sensor 81 again senses the elimination of 
slip of the wheel 60 and reports it to the ECU 80. According to the 
signals from the speed sensor 81, the ECU 80 opens the first solenoid 
valve 30, closes the second solenoid valve 31, and at the same time orders 
the operation of the motor 40. Then, the pump 41 pumps the oil in the tank 
90 to supply the braking section 70 through the third fluid path 22 and 
the first solenoid valve 30, thereby performing the braking operation. By 
repeating the process as above, the ABS performs its function. The 
reference numeral 100 not described above designates the differential 
gear. 
FIG. 2 schematically shows an entire construction of a disc brake employed 
in the conventional braking system, referring to which the operation of 
the disc brake will be described hereinbelow. 
When a driver steps on the brake pedal 10, the hydraulic pressure generated 
by the master cylinder 11 is transferred through an introduction port 121 
to a cylinder 120. This hydraulic pressure makes a piston 130 compress an 
inner pad 140 against a disc 160 in an instant, and at the same time the 
hydraulic pressure remaining in the cylinder 120 makes caliper 110 move 
rightward by means of a sliding member (not shown), so as to compress an 
outer pad 150 against the disc 160, thereby performing the braking 
function. When the brake pedal 10 is released, the piston 130 is restored 
to its original position due to the elastic force of a seal within groove 
131. Then, the disc 160, the inner pad 140, and the outer pad 150 are 
spaced again at a predetermined distance. 
However, in the conventional braking system described above, the heat 
energy produced by the friction between the disc and the pads in the 
course of braking the car is discharged untouched into the atmosphere to 
disappear, which is not an efficient use of energy. Further, the 
frictional heat shortens the life of the elements in the braking system. 
Moreover, the conventional braking system is also problematic in that its 
construction is very complicated because it requires individual systems 
for performing an anti-lock braking function and a traction control 
function, respectively. 
SUMMARY OF THE INVENTION 
The present invention overcomes the above described problems of the prior 
art, and accordingly it is an object of the present invention to provide a 
braking system of automobile, which can produce and store an electric 
power by means of the energy generated when the automobile is braked, 
thereby increasing efficiency in energy use, and simultaneously which can 
perform an anti-lock braking function and a traction control function. 
To achieve the above object, the present invention provides a braking 
system of an automobile having a variably exhausting pump unit, the 
braking system comprising: 
a brake pedal arranged in a driver's seat; 
a master cylinder for generating a hydraulic pressure when a force applied 
to the brake pedal is received; 
a variably exhausting pump unit for performing a pumping operation by the 
master cylinder; and 
a control section for sensing a traveling state of the automobile and 
controling so that a proper braking force is applied to a wheel of the 
automobile.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, a preferred embodiment of the present invention will be 
described in detail with reference to the accompanying drawings, and like 
elements will be numbered the same in the following description. 
FIG. 3 is a schematic hydraulic circuit diagram of a braking system having 
a variably exhausting pump unit according to the present invention, and 
FIG. 4 is a sectional view of the variably exhausting pump unit in FIG. 3, 
showing its operation when the automobile travels under normal conditions. 
As shown in FIGS. 3 and 4, the braking system according to the present 
invention includes a master cylinder 202, a variably exhausting pump unit 
300, a control section 220, a flow control valve 240, and a generating 
section 230. The master cylinder 202 generates a hydraulic pressure when a 
force applied to a brake pedal 201 is transferred thereto. The variably 
exhausting pump unit 300 brakes a wheel 210 with pumping oil at high 
pressure. The control section 220 senses the traveling state of the 
automobile and applies a proper braking force to the wheel 210. The flow 
control valve 240 makes a reverse torque be produced in the variably 
exhausting pump unit 300. The generating section 230 generates electricity 
by means of the hydraulic pressure applied when the automobile is braked. 
The hydraulic pressure generated at the master cylinder 202 and transferred 
through the first fluid path 251 makes a swash plate 306 be slanted, and 
the rotation of the slanted swash plate 306 enables the variably 
exhausting pump unit 300 to exhaust at high pressure the fluid introduced 
from a tank 260. In this case, the high pressure of this exhausted fluid 
is maintained between the flow control valve 240 and a solenoid valve 221, 
and then it applies a reverse torque to the variably exhausting pump unit 
300, which reverse torque functions as a braking force for the wheel 210. 
The control section 220 includes an electronic control unit (ECU) 222 for 
giving orders based on slip signals of the wheel transferred from a ring 
sensor 316 and a sensor 317 installed in the variably exhausting pump unit 
300, and a normal close-type solenoid valve 221 which is opened and closed 
corresponding to the orders from the ECU 222. 
The flow control valve 240 has a piston 243 elastically supported by a 
spring 244 and is connected to a second fluid path 252 branched off from 
the first fluid path 251. An introduction port 241 and an exhaust port 242 
are defined in the flow control valve 240. The introduction port 241 is 
connected to a third fluid path 253 connected to the solenoid valve 221, 
and the exhaust port 242 is connected to a fourth fluid path 254 from 
which a bypass tube 256 connected to the solenoid valve 221 is branched 
off. 
The generating section 230 includes an accumulator 231 connected to the 
fourth fluid path 254, a pump 232 operated by a hydraulic pressure 
transferred from the accumulator 231, a generator 233 for generating 
electricity by means of the driving force of the pump 232, and a battery 
234 for storing the electricity. The pump 232 is connected through a fifth 
fluid path 255 to the tank 260, so that the fluid having been used for 
driving the pump 232 is introduced into the tank 260. 
Hereinafter, the construction of a variably exhausting pump unit employed 
in the braking system as above will be described in detail with reference 
to FIG. 4. 
The variably exhausting pump unit 300 includes a rotation shaft 302 
extending through the middle of a body 301, one end of which is connected 
to a differential gear 211, and the other end of which is connected to a 
driving shaft 200 cooperating with the wheel 210 (see FIG. 3). The 
rotation shaft 302 is supported by a bearing 303, and a plurality of 
hydraulic cylinders 304 and hydraulic pistons 305 are fixed to the outer 
peripheral surface of the rotation shaft 302. Further, the swash plate 306 
for supporting the hydraulic piston 305 movably in the longitudinal 
direction is fixed to the rotation shaft 302 by a shaft pin 307. 
At the exterior of the body 301, there are provided a lever cylinder 310 
connected to the master cylinder 202 (see FIG. 3), a lever piston 311 
arranged in the lever cylinder 310, and a first spring 312 for applying an 
elastic force to the lever piston 311 against the hydraulic pressure 
transferred to the lever cylinder 310. Further, one end of the lever 
piston 311 is connected to a lever 313 which is in contact with a rear 
surface 306b of the swash plate 306. The lever 313 applies an external 
force to the swash plate 306 by the operation of the lever piston 311, to 
thereby make the swash plate 306 be slanted about the shaft pin 307. In 
addition, a second spring 314 is inserted between the body 301 and a front 
surface 306a of the swash plate 306 so as to oppose the external force by 
the lever 313, and a stopper 315 for limiting the movement of the swash 
plate 306 by the elastic force of the second spring 314 is disposed in 
front of the rear surface 306b of the swash plate 306. 
The ring sensor 316 and the sensor 317 for sensing a slide of the wheel are 
disposed respectively at the exterior of the hydraulic cylinder 304 and 
the variably exhausting pump unit 300. They transmits electric signals to 
the ECU 222 corresponding to the slide of the wheel. 
Meanwhile, a stepped motor 318 driven according to the electric signal of 
the ECU 222 is arranged at the exterior of the body 301, and the shaft of 
the stepped motor 318 is connected to a cam 319 which is in sliding 
contact with an end of the swash plate 306. 
Referring to FIGS. 3 and 4, the operation of the braking system constructed 
as above according to the present invention will be described hereinafter. 
When the automobile travels under a normal condition, that is, in a state 
where the brake pedal 201 is not stepped on, the rotation shaft 302 
connected to the differential gear 211 rotates according to the driving of 
the automobile, and accordingly the swash plate 306 assembled with the 
rotation shaft 302 by the shaft pin 307 also rotates. In this case, the 
rear surface 306b of the swash plate 306 comes into a close contact with 
the stopper 315 by the elastic force of the second spring 314, so that the 
swash plate 306 crosses the rotation shaft 302 at a right angle. In other 
words, the swash plate 306 rotates without being slanted, and hence the 
hydraulic piston 305 fixed to the swash plate 306 performs no operation in 
the hydraulic cylinder 304. Therefore, the rotation shaft 302 rotates 
without resistance to transfer the driving force of the automobile to the 
wheel 210. 
FIG. 5 is a sectional view for showing the operation of the variably 
exhausting pump unit when the automobile is braked. 
When the brake pedal 201 is stepped on for braking operation, the hydraulic 
pressure generated in the master cylinder 202 is transferred through the 
first fluid path 251 to the lever cylinder 310 so as to operate the lever 
piston 311. Then, the lever 313 connected to the lever piston 311 applies 
a force larger than the elastic force of the second spring 314 to the 
swash plate 306, so as to make the swash plate 306 be slanted 
counterclockwise about the shaft pin 307. 
When this slanted swash plate 306 rotates together with the rotation shaft 
302, the hydraulic piston 305 performs a linear alternating movement in 
the hydraulic cylinder 304, so that the oil introduced in the hydraulic 
cylinder 304 through an introduction path 308 is exhausted into the third 
fluid path 253 through an exhaust path 309. In this case, the flow control 
valve 240 is closed by the hydraulic pressure transferred through the 
second fluid path 252 from the master cylinder 202 and the solenoid valve 
221 also is closed, and thereby the third fluid path 253 is blocked off, 
so that the hydraulic pressure transferred to the third fluid path 253 
gradually increases. This increase of the hydraulic pressure in the closed 
third fluid path 253 produces a reverse torque preventing the rotation of 
the rotation shaft 302, which results in the braking force to the wheel 
210. 
In the meantime, when the wheel 210 slips due to an exceeding braking force 
applied to the wheel 210 or due to change of conditions of the ground, the 
ring sensor 316 and the sensor 317 sense the slip and transmits a 
corresponding electric signal to the ECU 222. Accordingly, the ECU 222 
opens the normal close type solenoid valve 221, so that the hydraulic 
pressure in the third fluid path 253 is bypassed through the open solenoid 
valve and bypass tube 221 and 256 to the fourth fluid path 254 and then 
transferred to the generating section 230. In result, the reverse torque 
for preventing the rotation of the rotation shaft 302 decreases, and the 
braking force to the wheel 210 decreases accordingly. 
As described above, when the hydraulic pressure in the third fluid path 253 
is discharged and hence the braking force decreases due to the opening of 
the solenoid valve 221, and if the ECU 222 determines that a proper 
braking force is not being applied to the wheel 210, the ECU 222 closes 
again the solenoid valve 221 to generate the reverse torque for preventing 
the rotation of the rotation shaft 302 to thereby apply again the braking 
force to the wheel 210. Repetition of the above process enables the 
anti-lock braking. 
When the hydraulic pressure in the third fluid path 253 is larger than that 
applied to the piston 243 of the flow control valve 240, the piston 243 of 
the flow control valve 240 is lowered down, so that the fluid in the third 
fluid path 253 flows through the introduction port 241 and the exhaust 
port 242 into the fourth fluid path 254. In this case, if the brake pedal 
201 is pressed further, that is, if further force is applied to the brake 
pedal 201, the piston 243 elevates to block up the introduction port 241, 
thereby generating the repetitive braking force as described above. 
When the external force having been applied to the brake pedal 201 is 
released so that the hydraulic pressure of the master cylinder 202 is 
released, the rear surface 306b of the swash plate 306 comes into close 
contact with the stopper 315 due to the elastic force of the second spring 
314, and thereby the swash plate 306 crosses the rotation shaft 302 at a 
right angle. Therefore, the hydraulic piston 305 fixed to the swash plate 
306 performs no operation in the hydraulic cylinder 304, and accordingly 
the rotation shaft 302 rotates without resistance to transfer the driving 
force of the automobile to the wheel 210. 
FIG. 6 is a sectional view showing the operation of the variably exhausting 
pump unit when the automobile performs the traction control function. 
When the ring sensor 316 and the sensor 317 sense slide of a wheel which 
may happen in case the automobile starts or accelerates on a slippery 
ground, they transmit a corresponding electric signal to the ECU 222. 
According to the signal, the ECU 222 operates the stepped motor 318 
disposed at an exterior of the body 301 to thereby rotate the cam 319, so 
that the swash plate 306 comes to be slanted counterclockwise about the 
shaft pin 307. When the slanted swash plate 306 rotates together with the 
rotation shaft 302, the hydraulic piston 305 performs a linear alternating 
movement in the hydraulic cylinder 304, SO that the oil introduced in the 
hydraulic cylinder 304 through the introduction path 308 is exhausted into 
the third fluid path 253 through the exhaust path 309. In this case, the 
third fluid path 253 is blocked off by the closed flow control valve and 
solenoid valves 240 and 221, so that the hydraulic pressure transferred to 
the third fluid path 253 gradually increases. This increase of the 
hydraulic pressure in the closed third fluid path 253 a produces a reverse 
torque preventing the rotation of the rotation shaft 302, which results in 
the braking force to the wheel 210. Through the above process, the 
traction control is performed. 
In the course of the repetitive braking operation as above, when the fluid 
under high pressure is introduced through the fourth fluid path 254 into 
the accumulator 231, the accumulator 231 absorbs the high hydraulic 
pressure while transferring a predetermined hydraulic pressure to the pump 
232 to thereby operate the pump 232. The pump 232 enables the generator 
233 to generate electricity and store it in the battery 234 SO that it can 
be used when necessary. 
The braking system according to the present invention employs a variably 
exhausting pump unit, as described above. Therefore, the braking system 
according to the present invention is very advantageous in that the energy 
generated in braking the automobile is not naturally exhausted but 
retrieved to be used for generating and storing electricity, which result 
in high efficiency in using energy. 
Furthermore, the braking system can perform the anti-lock braking function 
and the traction control function by controling the hydraulic pressure of 
the pump unit. Therefore, the braking system according to the present 
invention has a further advantage that it does not require a brake booster 
and a disc brake device, which means its construction can be simplified 
and its size and weight can be reduced. Further to the above, the 
operational noise of the system can be greatly reduced. 
While the present invention has been particularly shown and described with 
reference to the particular embodiment thereof, it will be understood by 
those skilled in the art that various changes in form and details may be 
effected therein without departing from the spirit and scope of the 
invention as defined by the appended claims.