Solenoid valve for brake system

Disclosed herein is a solenoid valve for a brake system. According to an embodiment of the present invention, the solenoid valve for a brake system includes a filter member accommodated in an bore of a modulator block having an inlet path and an outlet path, a magnet core coupled to the filter member and having a through hole passing through in a longitudinal direction, a sleeve fixed to a modulator block and having a flange part coupled to an outer side of the magnet core, an armature installed to be movable forward and backward inside the sleeve, a valve seat fixed to the through hole and including a first orifice, a plunger disposed in the through hole so as to open and close the first orifice by moving forward and backward according to an operation of the armature, and a restoring spring pressurizing the plunger toward the armature, and the filter member includes a filter filtering oil, an insertion part in which a second orifice is formed and press-fitted into the through hole, a supporting part provided on an outer side of the insertion part and supporting a lower end of the magnet core, and a check valve forming a bypass flow path between the inlet path and the outlet path. A slot in communication with the inlet path is formed on a lower side of the supporting part so that oil flows into an entrance of the bypass flow path.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2014-0043297, filed on Apr. 11, 2014 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

Embodiments of the present invention relate to a solenoid valve for a brake system, and more particularly, a solenoid valve for a brake system capable of increasing a brake hydraulic pressure supplied to a wheel cylinder during general braking and improving durability thereof by increasing compression strength thereof.

2. Description of the Related Art

Hydraulic brake systems should be installed for braking in vehicles, and recently, various types of systems have been proposed for obtaining more powerful and stable braking forces. As an example of the hydraulic brake systems, there are an anti-lock brake system (ABS) which prevents wheels from slipping during breaking, a brake traction control system (BTCS) which prevents driving wheels from slipping when vehicles are suddenly or rapidly accelerated, and a vehicle attitude control system (e.g., electronic stability control (ESC)) which combines the ABS and the BTCS to control brake hydraulic pressure and maintains a stable state for vehicle driving.

As shown inFIG. 1, a hydraulic brake system includes a master cylinder10configured to generate pressure needed for braking, a plurality of solenoid valves30,40,50and60configured to control hydraulic pressure for braking that is transferred to wheel cylinders20installed on each of wheels FL, FR, RL, and RR of a vehicle, low pressure accumulators70configured to temporarily store oil, pumps80and a motor85configured to forcibly pump the oil temporarily stored in the low pressure accumulators70, orifices90configured to reduce pressure pulses of the oil pumped from the pump80, an electronic control unit (ECU, not shown) configured to electrically control the solenoid valves30,40,50, and60and to drive the pumps80. In addition, the solenoid valves30,40,50, and60, the low pressure accumulators70, the pumps80, and the like are compactly installed in a modulator block100made of an aluminum based material, and the ECU including a coil assembly (not shown) of each of the solenoid valves30,40,50, and60and an ECU housing (not shown) having embedded circuit boards is coupled to the modulator block100.

The hydraulic brake system described above selects a ABS, TCS, or ESC mode according to a driving state of a vehicle to perform an appropriate braking and stable braking operation.

Meanwhile, the plurality of solenoid valves30,40,50, and60provided in a brake system configured to control a braking pressure are divided into a normal open (NO) type solenoid valve which usually maintains in an open state and a normal close (NC) type solenoid valve which usually maintains in a close state. At this time, NO type traction control (TC) valves30first connected to ports of the master cylinder10through flow paths usually maintains in an open state, and when road surface slip occurs due to sudden unintended starting of a vehicle or the like, the traction control (TC) valves30close a flow path to transfer a braking pressure generated by the pump80to wheel cylinders of a vehicle, and thus braking of a vehicle may be performed even when a driver does not step on a brake pedal. The TC valve30transfers hydraulic pressure flowing from the master cylinder10to the wheel cylinders20through the TC valves30passing through the NO type inlet valves50provided on an up stream of each of the wheel cylinders20. That is, the TC valve30usually maintains in an open state, and transfers brake hydraulic pressure generated from the master cylinder10toward the wheel cylinders20during general braking (e.g., a combined break system (CBS)) by a brake pedal.

FIG. 2shows a conventional normal open type solenoid valve (TC valve). The TC valve30includes a magnet core31having a through hole31ain a longitudinal direction in a center thereof and a flow path31bon an circumference thereof, a dome-shaped sleeve32installed on the magnet core31and closing an upper part of the magnet core31, a valve seat33installed in the magnet core31, an armature34and a plunger35installed in the upper part of the magnet core31and the through hole31aand configured to move forward and backward, and a filter member36installed on a lower part of the magnet core31. At this time, a separate bypass flow path36ais formed in the filter member36so that oil flows into an outlet path103through an inlet path102of a modulator block100, and a check valve37is provided in the bypass flow path36a.

The TC valve30is installed in the modulator block100and a flow path of oil flowing through the inlet path102is divided into two flow paths when the oil passes through the TC valve30. That is, oil flowing through the inlet path102located on an side of the TC valve30is filtered by the filter member36, transferred to the outlet path103through the through hole31aand a flow path31bformed on an circumference of the magnet core31, and transferred to the outlet path103through the bypass flow path36aformed in the filter member36. At this time, an amount of oil flowing through the bypass flow path36ahas 80% of a total amount of oil passing through the TC valve30.

Meanwhile, as shown inFIG. 1, according to hydraulic pressure generated from the master cylinder10is transferred to two wheel cylinders20through one TC valve30, a TC valve30structure is improved and provided so as to secure a sufficient amount of oil during general braking (CBS). For example, as shown inFIG. 2, a structure in which a lower part of the magnet core31coupled to the filter member36is coupled to the filter member36with an interval is used so that a rate of an amount of oil flowing into the bypass flow path36ais increased. Although an amount of oil transferred to the wheel cylinders20may be increased by the structure during general braking, a coupling force of the magnet core31and the filter member is decreased, and thus there are problems in that compression strength and durability thereof are degraded.

In addition, according to trends miniaturizing products, since overall heights of solenoid valves are decreased and areas passing through bypass flow paths36aare decreased, a sufficient amount of oil is not supplied compared to existing systems, and there is problem in that the performance of valves and brake systems is degraded.

SUMMARY

A solenoid valve for a brake system in accordance with an embodiment of the present invention may improve an assembly structure of a magnet core and a filter member so as to improve compression strength and durability, and also increase brake hydraulic pressure supplied to a wheel cylinder during general braking.

In accordance with one aspect of the present invention, a solenoid valve for a brake system includes a filter member accommodated in an bore of a modulator block having an inlet path and an outlet path, a magnet core coupled to the filter member and in which a through hole passing through in a longitudinal direction is formed, a sleeve fixed to a modulator block and in which a flange part coupled to an outer side of the magnet core is provided, an armature installed to be moveable forward and backward inside the sleeve, a valve seat fixed to the through hole and including a first orifice, a plunger disposed in the through hole so as to open and close the first orifice by moving forward and backward according to an operation of the armature, and a restoring spring pressurizing the plunger toward the armature. The filter member includes a filter filtering oil, an insertion part in which a second orifice is formed and press-fitted into the through hole, a supporting part provided on an outer side of the insertion part and supporting a lower end of the magnet core, and a check valve forming a bypass flow path between the inlet path and the outlet path, and a slot in communication with the inlet path is formed on a lower side of the supporting part so that oil flows into an entrance of the bypass flow path.

Oil flowing into the inlet path by the supporting part may be divided into and supplied to a radial direction flow path of the magnet core and the slot.

The check valve may include an opening/closing ball installed in the bypass flow path to be moveable forward and backward, and configured to open the bypass flow path when a brake operation is performed, and close the bypass flow path when a brake operation is completed.

The filter member may include a circumference part surrounding an outer side of the magnet core, and the filter may include a first filter provided on the circumference part opposite the inlet path and a second filter provided on the circumference part opposite the outlet path.

The insertion part may include a connection flow path communicating the through hole with the outlet path through the second orifice.

In addition, a step may be provided on an outer peripheral of the plunger to support an one end of the restoring spring, and a step-shaped spring supporting step may be provided in a through hole of the magnet core to support the other end of the restoring springe.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments are provided in order to fully explain the spirit and scope of the present invention for those skilled in the art. Thus, the present invention should not be construed as limited to the embodiments set forth herein and may be accomplished in other various embodiments. Parts irrelevant to description are omitted in the drawings in order to clearly explain the present invention. A size of the elements in the drawings may be exaggerated in order to facilitate understanding.

FIG. 3is cross-sectional view illustrating a solenoid valve for a brake system in accordance with an exemplary embodiment of the present invention.FIG. 4is a partially exploded cross-sectional view illustrating a flow state of hydraulic pressure of the solenoid valve for the brake system in accordance with the exemplary embodiment of the present invention during general braking.

Referring toFIGS. 3 and 4, a solenoid valve for a brake system110includes a filter member120accommodated in a bore101of a modulator block100, a magnet core140coupled to the filter member120, a valve seat150and a plunger160installed in the magnet core140, a sleeve170coupled to an outer side of the magnet core140, an armature180installed in the sleeve170, and an excitation coil assembly190installed on an outer side of the sleeve170.

The magnet core140includes a through hole141configured to pass through in a longitudinal direction, and is in a cylindrical shape having a flow path142in a radial direction to communicate with the through hole141. The valve seat150including a first orifice151is press-fitted and fixed inside the through hole141of the magnet core140.

The filter member120is installed to be inserted into the bore101of the modulator block100in a state coupled to the magnet core140. The filter member120includes a circumference part121surrounding a lower outer side of the magnet core140, and an insertion part125disposed on a lower end of the magnet core140and integrally formed with the circumference part121to press-fit into the through hole141. An inside of the circumference part121accommodates the lower end of the magnet core140, and an outer side of the circumference part121is supported by an inner side of the bore101of the modulator block100. A connection flow path126connected to the through hole141of the magnet core140is formed on a center of the insertion part125, and a second orifice127configured to rectify an oil flow is formed inside the connection flow path126.

In addition, a separate bypass flow path123is formed an outer side of the connection flow path126in the circumference part121of the filter member120. A first filter121aconfigured to filter oil flowing through an inlet path102of the modulator block100and a second filter121bconfigured to filter a foreign material of oil flowing toward an outlet path103are provided in the circumference part121. The first and second filters121aand121bare provided in the circumference part121at positions respectively opposite the inlet path102and the outlet path103.

In addition, a supporting part128supporting a lower end of the magnet core140is provided on an outer side of the insertion part125. When the magnet core140and the filter member120are coupled, the compression strength and durability of the solenoid valve110may be improved according to an increase in a contact area thereof by the supporting part128.

Meanwhile, the bypass flow path123formed in the filter member120is formed so that hydraulic pressure transferred through the inlet path102between the inlet path102and the outlet path103flows into the outlet path103. That is, the bypass flow path123is formed to allow oil to separately flow from flow paths of the radial direction flow path142and the through hole141of the magnet core140during brake operation, and a check valve130is installed therein. The check valve130includes an opening/closing ball131installed in the bypass flow path123to be movable forward and backward. The opening/closing ball131opens the bypass flow path123during a brake operation, and the opening/closing ball131closes the bypass flow path123when a brake operation is completed.

A slot122in communication with the inlet path102is formed in an entrance of the bypass flow path123, that is, a lower side of the supporting part128, so that oil flows into the entrance of the bypass flow path123. The slot122is formed between the supporting part128and the bypass flow path123of the circumference part121, and oil flowing into the inlet path102by the supporting part128is divided and supplied to the bypass flow path123and the radial direction flow path142of the magnet core140. Therefore, a brake hydraulic pressure transferred to a wheel cylinder (refer to20ofFIG. 1) through the slot122may be increased. In addition, a location of forming the supporting part128may be selectively changed to change a size of the slot122, and thus, an amount of oil flowing into the slot may be controlled.

The plunger160is installed to vertically move in the through hole141above the valve seat150. The plunger160includes an opening/closing part161configured to open and close the first orifice151on a lower end thereof. In addition, when power is not applied to the excitation coil assembly190, the plunger160is pressurized toward the armature180by the restoring spring165to open the first orifice151. At this time, a step163is provided on an upper outer side of the plunger160to support an one end of the restoring spring165, and a step-shaped spring supporting step143configured to support on the other end of the restoring spring165is provided in the through hole141of the magnet core140so that the restoring spring165is stably installed to supply an elasticity force to the plunger160. That is, a lower end of the restoring spring165is supported by the spring supporting step143and an upper end of the restoring spring165is supported by the step163of an outer side of the plunger160.

The sleeve170is in a cylindrical shape and coupled to an outer side of the magnet core140. The sleeve170includes a dome-shaped closing part171provided thereon to close an upper part of the magnet core140, and a flange part172, whose lower end is bent, provided to fix to an entrance side of the bore101of the modulator block100.

The armature180is located at an upper inner side of the sleeve170, that is, in the dome-shaped closing part171, and installed to be vertically movable. When power is applied to the excitation coil assembly190, the armature180moves to pressurize the plunger160so as to close the first orifice151.

The excitation coil assembly190is provided in a cylindrical shape and coupled to an upper outer side of the sleeve170. The excitation coil assembly190includes a cylindrical-shaped coil case191, a bobbin192accommodated in the coil case191, and an excitation coil193wound around an outer side of the bobbin192. Since a magnetic field is created when power is applied to the excitation coil193, the armature180is moved toward the magnet core140to pressurize the plunger160, and thus, the first orifice151may be closed.

When the solenoid valve110is installed on the modulator block100, the magnet core140, the filter member120, the valve seat150, the plunger160, the armature180, the sleeve170, and the like are first assembled outside the modulator block100, and the filter member120and the magnet core140insert into the bore101of the modulator block100. Then, an entrance side of the bore101of the modulator block100is modified. Therefore, a transform part105of the modulator block100is modified to cover the flange part172of the sleeve170and to fix the sleeve170, and valve installation is completed.

Since the magnet core140is provided in a simple cylindrical shape, the number of manufacturing processes of the magnet core140may be decreased, and thus the productivity thereof may be increased. In addition, since the flange part172of the sleeve170coupled to an outer side of the magnet core140is directly fixed to the modulator block100, an assembly process is easily performed and a manufacturing process may also be simplified.

Hereinafter, opening/closing operations of the solenoid valve for a brake system will be described.

When power is not applied to the excitation coil assembly190, the restoring spring165pushes the plunger160toward the armature180, the opening/closing part161of the plunger160is spaced apart from the first orifice151, and the first orifice151maintains an open state thereof. Therefore, oil flowing through the inlet path102flows into the outlet path103passing through the radial direction flow path142of the magnet core140, the through hole141, the first orifice151, the second orifice127, and connection flow path126. Simultaneously, oil flowing through the inlet path102flows into the outlet path103passing through the slot122formed on the circumference part121of the filter member120and the bypass flow path123.

As is apparent from the above description, a solenoid valve for a brake system in accordance with the embodiment of the present invention can improve compression strength and durability thereof so that a filter member coupled to a magnet core supports a lower end of the magnet core to increase a contact area therebetween.

In addition, a slot is formed in an entrance of a bypass flow path including a check valve to increase inlet of an amount of oil, and thus, sufficient brake hydraulic pressure may be provided to improve the performance of the brake system during general braking.