BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates generally to the AntiLock

Brake System(ABS) of automobile, and more particulary to a valve assembly to prevent the inverse flow of hydraulic pressure and increase the pressure of hydraulic oil and thereby enables more effective antilock braking.

Description of prior art

To achieve a good driving performance of an automobile, effective acceleration and deceleration characteristics, and particulary in views of safety, good braking characteristic must be guranteed. It has been meant that the effecient braking characteristic can be possible by means of strong braking and easy steering performance thereof, so that misoperation and breakdown of a brake system should be prevented, and the brake system be easily fixed when it is out of order.

To meet the above described various requirements, a brake system for the general automobile has assembled to work effectively such as wheel cylinder assembly, brake pedal, booster, hydraulic reservoir, master cylinder, hydraulic pressure flow pipe, hydraulic pressure control valve, and the other parts interconnected with each other. The fact that the temperature of the friction part between the road surface and the tread of tire is rapidly arising when the car suddenly trying to stop its forwarding movement, and that the friction coefficient between the road surface and wheel tread surface

made of organic material (synthetic rubber or natural rubber) is rapidly decreased results to slip the car on the road and for the driver not to control as he wished. The invention to prevent such phenomenon (fading effect or skidding effect) is Antilock Brake System (ABS) , which system makes it possible to unlock and lock intermittently several to many hundred times the wheel when it suddenly met the rapid brake in high speed. The ABS system prevents a wheel locking phenomenon and reducing a braking distance and also makes it possible to control the car especially steering even in the brake pedal pressured.

The general mechanism and pressure flow can be described as follows.

The sensor of ABS system always monitor the rotation speed of wheels and its result signal flows into the ECU unit of car engine. The braking pressure is to be reduced when the deceleration value of an automobile surpasses a predetermined value in the course of braking the automobile. On the contrary, the braking pressure starts to increase its power when the accelaration value is increased so that the wheel be locked to stop the car forwarding.

Referring to Fig.l showes a schematic constructional view of a modulator 1 used in ABS system.

Modulator encloses a flow control valve 2 for increasing or decreasing the oil pressure in accordance with the operations of a spool and a solenoid valve 7, the control valve 2 having at least four parts consisting of a first port 3, a second port 4, a third port 5, and a fourth port 6. When solenoid opening signal from the ECU is received the oil flow of first port 3 and second port 4 is returned to the reservoir through the third and fourth ports 5 and 6 to reduce the

braking pressure, and when the closing operation of solenoid 7 starts the braking pressure increases enough to lock the wheel.

As shown in this usual ABS art, the hydraulic pressure of braking power is transferred to a pedal in car driver foot directly so as to give an unpleasant sense since the pressure from a second conduit 11 and a third conduit 12 is transferred to a master cylinder 13 through a first conduit 10. The intermittent increasing and decreasing of braking pressure are respectively transferred to the driver's foot and vibrate the pedal when ABS system operating in sudden brake. Incidently the impact of the counterflow brake pressure is transferred to a check valve system in the cylinder.Accordingly the endurance of the valve system is to be shortened leading the cause of a loss of the intrinsic function of the ABS system. Furthermore, as the oil pressure transferred through the master cylinder 13 is distributed to the first conduit, there used to be a problem that the brake pressure is reduced by one-third or more than half of that.

SUMMARY OF THE INVENTION

To overcome the above-mentioned disadvantages, the object of present invention is to provide a more effective valve assembly which has at least two cylinder chambers, and by which the countercurrent of brake oil is sensed and cut off effectively. To realize the above object of the present invention, a preffered embodiment of a valve assembly according to the present invention comprises a first valve chamber which has a first port connected to a master cylinder,a second valve chamber which is hydraulically communicated with the first valve chamber and has a second port connected to the ABS, a first check valve which is enclosed in the first valve chamber to open or close an inlet

passage from the first port by a spring and a pilot pressure from the said first port, and a solenoid valve to which is enclosed in the second valve chamber and to which a second check valve is attached to open or close a drain passage to the second port by operation thereof.

In an alternative preferred embodiment it compries a first valve chamber which has a first sleeve and a second sleeve each having different diameter and encloses a spool having a centrally penetrated orifice and supported by a spring to space somewhat from a drain passage, the spool enclosing a check valve to open or to close the drain passage by the spring and apilot pressure from a first port;and a second valve chamber which has a third sleeve and a fourth sleeve each having different diameter and encloses a spool being in contact with a check valve supported by a spring, the first vlave chamber and a second valve chamber being hydraulically communicated with each other.

In another embodiment, the present invention provides valve assembly comprising a upper sleeve which has a stopper containing a hemispherically-shaped seating portion, the stopper having an enclosed check valve supported by a spring and having a passage connecting a center of said seating portion with a side of the stopper;a middle sleeve having smaller diameter than said upper sleeve; a lower sleeve which has greater diameter than said meddle sleeve and is provided a bottom thereof with a port connected to the ABS;sn upwardly and downwardly movable spool which is enclosed in said three sleeves and has a penetreated orifice; and a check valve which is provided outwardly of a drain passage to the drain port connected by a spring and being in contact with a lug located on lower end of said spool.

BRIEF DESCRIPTION OF THE DRAWINGS

Object, and other features and advantages of the present invention will become apparent through the following description with reference to the accompanying drawings, in which: Fig.l is a constructional view of a conventional ABS system;

Fig.2 is a cross-sectional view of electronic control valve system according to a first embodiment of the present invention; Fig.3 is a cross-sectional view of a mechanical control valve system according to a second embodiment of the present invention; and

Fig.4 is a cross-sectional view of a control valve system having a single valve according to a third embodiment of the present invention.

BRIEF DESCRIPTION OF THE INVENTION

In the first embodiment of the present invention as shown in Fig.2, a first port 15 connected to a master cylinder is connected to the side of a first valve chamber 16, and a second port 17 as connected to the top side of a second valve chamber 19 having a solenoid valve 18 to which a second check valve is attached. In the first valve chamber 16, a check valve 22 which maintains an inlet passage 21 to be opened always by a spring 20 is supported. In the second valve chamber 19, a solenoid valve 18 which maintains a drain passage 23 to be opened always, is enclosed. The check valve

22, the shape of which is shown as ball type in the drawings as an example for the description, may have various shapes including a cone, a plate and other suitable type if necessary.

When the solenoid valve 18 is operated in accordance with the signal of the hydraulic sensor, the above-mentioned

control valve assembly cuts off an outlet passage 23 so as not to transfer countercurrent pressure incurred in the ABS toward the master cylinder. Check valve 22 in the first valve chamber 16 prevents excessive pressure from being transferred toward the wheel cylinder, because the excessive pressure pushes a spool 25 supported by a spring 20 to block the inlet passage 21 when the excessive pressure is transferred from the master cylinder through a pilot passage 24. Namely, by the alternative opening and closing of the inlet passage 21 and the drain pasage 23, the inverse pressure in the ABS system is blocked effectively while the excessive pressure over the necessary value also is blocked not to be transferred.

The above mentioned assembly has a limitation that the solenoid valve 18 is operated only when the input signal by the hydraulic sensor is received, and this can be serious problem if misoperation is occured.

Referring to Fig.2 illustrating the second embodiment of present invention, a first port 15 interconnected toward the master cylinder and a second port 17 interconnected toward the ABS system are located respectively in two separated valve chambers, and the assembly has a mechanical structure in which a spool is enclosed.

In a first valve chamber 25, a first sleeve 26 and second vlave 27 having different diameters are provided, and a spool

29 having an orifice 28 at center portion is supported such that it is spaced from a drain passage 31 with a predetermined distance by a spring 30.

In a second valve chamber 32, a third sleeve 33 and a fourth sleeve 34 having different diameters are provided, and a spool 36 having orifice 35 formed at center thereof is supported by spring 37, the lower edge of the spool 36 being

in contact with a check valve 39.

Hereinafter described the operation of the control valve assembly as mentioned above.

When the excessive pressure is applied from the master cylinder, the extra pressure remaining at the drain passage 31 is entered through the orifice 28 into the space defined by the first sleeve 26 to move the spool 29 downwardly. When the force for moving the spool 29 is greater than the elastic force of the spring 30, the spool 29 is lowered as shown by an arrow A in Fig.3 to block the drain passage 31 (as shown by dotted line) such that it is prevented for the force exceeding actuating force of the brake to be transferred toward the wheel cylinder and smooth operation of the ABS at wheel cylinder (i.e., repeated operation of locking and unlocking) is ensured. When the excesseve inverse pressure is transferred from the ABS through the second port in, the pressure is transferred again to the third sleeve 33 to move the spool 36, as indicated by arrow B. Whereby the passage 33a is blocked by the restoring force of a supporting spring 38 to prevent the pressure from being transferred.

Therefore, because pressure transfer is efficiently controlled without electronic equipment such as pressure sensor and solenoid valve, the possibility of failure or misoperation can be eliminated.

According to the third embodiment of the present invention, there is provided a control valve assembly which has compact design as compared with just above-mentioned control valve assembly and has one valve chamber which reserve the entire functions of assembly. Rererring to Fig.4, there is illustrated a cross-sectional view of the third embodiment of the present invention.

In a valve body 40, an upper sleeve 42 and a lower sleeve 43 each having diameter greater than a middle sleeve 41 are provided. Included in three sleeves 41,42,43 is upwardly and downwardly movable spool 45 supported by a spring 44 and having centrally penetrated orifice 46, check valve 49 is supported by a spring 48 is located outwardly of drain passage 47 and contact with a lug 45a on the lower end of the spool 45. In the upper sleeve 42, a stopper 51 having a hemispheically-shaped seating portion 50 of somewhat greater diameter than that of the upper end of the spool 45 is provided. At the center of the stopper 51, a passage 56 and a check valve 56 supported by a spring 54 is positioned. Port 52 connected with the master cylinder is formed on a side of the upper sleeve 42, and the lower communicated with the ABS. If desired, high pressure gas such as nitrogen and helium can be supplied instead of a spring 44 to uniformly place the spool 45. Surface area of spool 45 is smaller adjacent the upper sleeve 42 than lower sleeve 42 for varying oil pressure receiving area.

The middle sleeve 57 is a portion having a spring wich supports the spool 45, being upwardly and downwardly moving portion which is separated from the lower sleeve 43 about spool.

The operation of above-mentioned control valve assembly will be described herein below.

Firstly, when excessive pressure is applied to the port 52 by way of master cylinder, the pressure entered into the upper sleeve 42 is transferred to the lower sleeve 43 through the orifice 46. Then, since surface area of the top end of spool 45 in the upper sleeve is smaller than surface area of the lower end of spool 45 in the lower sleeve, there is induced a pressure difference, the spool 45 is upwardlly moved as

indicated by means of the check valve 49 and at the same time the top end is safely received in the hemispherically shaped seating portion 50 to block the inlet of orifice 46 by the check valve 55, Accordingly, if the brake is intensively operated, excessive pressure (i.e., pressure exceeding the braking pressure) is automatically blocked, thereby optimizing the operating effect of brake.

Secondly, when inverse pressure is transferred from te drain port 53 being communicated with ABS, the spool 45 is upwardly moved to block the drain passage 47 prevented for the inverse pressure toi be transferrd into the master cylinder, there be a effect in which the repelling power transferred to the brake pedal can be eliminated.

Thirdly, once the driver releases the brake pedal to reduce pressure of the master cylindr, the check valve 55 is opened, pressure of lower sleeve 43 is then removed through the orifice 46, snd the spool 45 is downwardly moved as indicated by the arrow to open the check valve 49, removing the pressure of drain port 53 and the clamping force of brake.

As mentioned above, the control valve assembly of the present invention has an adavantage in which the abrasion and deformation of piston cup is prevented, as the impact force applied to the piston cup in the master cylinder is removed by blocking the inverse pressure.

Also, as repelling force intermittently transferred to the brake pedal in an the operation of ABS is disappeared, the ailment given previously to the drive removed. Furthermore, as the inverse pressure transferred toward the master cylinder is totally transferred to the wheel cylinder, the assembly has a further advantage in which the operation of brake is effectively performed with lower pressure.