Solenoid valve for brake system

Disclosed is a solenoid valve for a brake system, the solenoid valve including a magnet core that is provided in a cylindrical shape, is installed in a bore of a modulator block, and has a through-hole opening in a lengthwise direction thereof and a radial direction passage communicating with the through-hole; an armature that is installed at one end of the magnet core so as to be reciprocated; a valve seat that is provided at the other end of the magnet core and has an orifice; a plunger that is inserted into the through-hole and performs a sliding motion by the armature to open and close the orifice; a sleeve that is fixed to the bore while accommodating the armature and the magnet core; and a return spring that is provided to apply an elastic restorative force to the plunger to open the orifice, wherein a passage hole is provided in a spiral shape along the through-hole at an inner circumferential surface of the magnet core to discharge air between the magnet core and the plunger and air between the magnet core and the armature.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2014-0043467, 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, to a solenoid valve for a brake system capable of easily discharging air inside the solenoid valve and thus improving a control performance of the solenoid valve.

2. Description of the Related Art

A hydraulic brake system is installed in a vehicle as an essential element to perform a braking operation. In this regard, various brake systems have been recently suggested to provide more strong and stable braking force. Examples of the hydraulic brake system include an Anti-Lock Brake System (ABS) for preventing skid of wheels at the time of the braking, a brake traction control system (BTCS) for preventing slip of driving wheels at the time of a sudden acceleration incident or an unintended acceleration, and an electronic stability system (ESC) implemented as a combination of an ABS and a traction control to maintain a stable driving state of a vehicle by controlling a liquid pressure of a brake.

In order to implement a brake system, a modulator block has a plurality of solenoid valves that are electronically controlled, and a passage (a hydraulic circuit) is selectively open and closed by the solenoid valve. The solenoid valve is divided into a normal open type solenoid valve that remains normally opened, and a normal closed type solenoid valve that remains normally closed.

In general, the normal open type solenoid valve includes a magnet core provided at a center thereof with a through-hole formed lengthwise thereof and provided at a periphery thereof with an outlet, a domed sleeve installed at an upper portion of the magnet core, an armature installed inside the sleeve so as to be reciprocated, and an excitation coil installed at an outer side of the sleeve to reciprocate the armature.

Inside the through-hole of the magnet core, a plunger, a valve seat and a return spring are installed. The plunger is reciprocated according to an operation of the armature. The valve seat is provided with an orifice that is open and closed by the plunger. The return spring allows the plunger to be pushed toward the armature such that the orifice is open when power is not applied to the excitation coil.

The solenoid valve is installed on the modulator block to selectively open or close the orifice through the operations of the armature and the plunger, thereby controlling a flow of oil in the passage formed on the modulator block.

PRIORITY ART DOCUMENT

However, the solenoid valve has difficulty in discharging air that remains between the magnet core and the armature, and between the magnet core and the plunger, which causes vibration and noise at the opening/closing of the orifice, and degrades the performance of the valve.

SUMMARY

Therefore, it is an aspect of the present invention to provide a solenoid valve for a brake system, capable of preventing vibration and noise that occur at the time of driving the solenoid valve by smoothly discharging air inside the valve.

In accordance with one aspect of the present invention, a solenoid valve for a brake system includes a magnet core, an armature, a valve seat, a plunger, a sleeve, and a return spring. The magnet core may be provided in a cylindrical shape, may be installed in a bore of a modulator block, and may have a through-hole opening in a lengthwise direction thereof and a radial direction passage communicating with the through-hole. The armature may be installed at one end of the magnet core so as to be reciprocated. The valve seat may be provided at the other end of the magnet core and may have an orifice. The plunger may be inserted into the through-hole and may perform a sliding motion by the armature to open and close the orifice. The sleeve may be fixed to the bore while accommodating the armature and the magnet core. The return spring may be provided to apply an elastic restorative force to the plunger to open the orifice. A passage hole may be provided in a spiral shape along the through-hole at an inner circumferential surface of the magnet core to discharge air between the magnet core and the plunger and air between the magnet core and the armature.

The passage hole may be molded in a form rolling.

The magnet core may be provided at an inner circumferential surface thereof with a spring support ledge protruding to support a lower end of the return spring. The plunger may be provided with an outer circumferential surface thereof with a step portion stepped inward to support an upper end of the return spring. One end of the passage hole may extend to a portion between the magnet core and the armature, and the other end of the passage hole may extend to a portion between the spring support ledge and the step portion, to expand a gap between the magnet core and the armature and a gap between the magnet core and the plunger.

The passage hole may connect to the orifice through a transfer passage hole formed lengthwise along the spring support ledge.

As is apparent from the above, the solenoid valve for the brake system according to the embodiment of the present invention can prevent noise and vibration that may be caused by air remaining in the solenoid valve by using a spiral passage hole provided at an inner circumferential surface of the magnet core to naturally discharge air remaining between the magnet core and the armature and between the magnet core and the plunger in the valve at the time of operation of the plunger.

In addition, the spiral passage hole provided in the magnet core of the solenoid valve for the brake system according to the embodiment of the present invention is manufactured by a form rolling to have a superior concentricity, thereby effectively preventing a center deviation of a plunger that may occur due to a repeated long-term operation.

DETAILED DESCRIPTION

Various embodiments will now be described more fully with reference to the accompanying drawings in which some embodiments are shown. These inventive concepts may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough and complete and fully conveys the inventive concept to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity.

FIG. 1is a cross-sectional view illustrating a solenoid valve for a brake system in accordance with one embodiment of the present invention.

Referring to the drawing, a solenoid valve for a brake system according to an embodiment of the present invention100includes a filter member120accommodated in a bore111of a modulator block110, a magnet core140coupled to the filter member120, a valve seat150and a plunger160that are installed in the magnet core140, a sleeve170coupled to an outer side of the magnet core140, an armature180provided in the sleeve170, a return spring190applying an elastic force to move the plunger160toward the armature180, and an excitation coil assembly (not shown) installed at an outer side of the sleeve170.

The magnet core140is provided with a cylindrical shape while having a through-hole141formed in a lengthwise direction thereof, and having a radial passage142radially formed at a lower portion of the magnet core140to communicate with the through-hole141. The valve seat150having an orifice151is press fitted to the inside of the through-hole141of the magnet core140. In addition, the magnet core140is provided at an inner circumferential surface thereof with a spring support ledge145protruding to support a lower end of the return spring190.

The filter member120is introduced and installed to the bore111of the modulator block110in a state of being coupled to the magnet core140. The filter member120includes a periphery portion121surrounding an outer surface of the lower portion of the magnet core140, and an insert portion125positioned at the lower end of the magnet core140and integrally formed with the periphery portion121so to be press fitted to the through-hole141. The periphery portion121accommodates the lower portion of the magnet core140, and has an outer surface thereof supported by an inner surface of the bore111of the modulator block100. The insert portion124is provided at a center thereof with a connecting passage126connected to the through-hole141of the magnet core140, so as to be insertedly coupled to the through-hole141of the magnet core140. The connecting passage125communicates with the through-hole141in a lengthwise direction of the magnet core140.

In addition, the periphery portion121of the filter member120is additionally provided with a bypass passage123formed at an outside of the connecting passage126. The periphery portion121is provided with a first filter portion121ato filter foreign substance of oil passing through a first passage112of the modulator block110, and a second filter portion121bto filter foreign substance of oil passing through a second passage113of the modulator block110. The first filter portion121aand the second filter portion121bare provided at positions of the periphery portion121facing the first passage112and the second passage113, respectively.

Meanwhile, the bypass passage123formed at the filter member120allows an oil pressure transferred through the first passage112from between the first passage112and the second passage113to flow to the second passage113. That is, the bypass passage123is provided to flow oil independent of a passage allowing oil to pass through the radial passage142and the through-hole141of the magnet core140at a braking operation. A check valve130is installed. The check valve130includes an opening/closing ball131installed in the bypass passage123so as to be reciprocated. The opening/closing ball131opens the bypass passage123at a braking operation, and closes the bypass passage123upon termination of a braking operation.

The plunger160is installed to be reciprocated up and down in the through-hole141at the upper side of the valve seat150. The plunger160is provided at a lower end thereof with an opening/closing portion161to open/close the orifice151. In addition, the plunger160is pushed toward the armature180by the return spring190to open the orifice151when power is not applied to the excitation coil assembly (not shown). In this case, the plunger160is provided at an upper outer side thereof with a step portion165stepped outward to support one end of the return spring190so that the return spring190is stably installed on the step portion165to provide the plunger160with an elastic force. A spring support ledge145having a step is provided at the through-hole141of the magnet core140to support the other end of the return spring190, so that the lower end of the return spring190is supported by the spring support ledge145and the upper end of the return spring190is supported by the step portion165formed on the outer surface of the plunger160.

The sleeve170is provided in a cylindrical shape, and is coupled to the outer surface of the magnet core140. The sleeve170is provided at an upper side thereof with a domed closing portion171to close the upper side of the magnet core140, and a flange portion172formed by bending a lower end of the sleeve170to be fixed to an inlet of the bore111of the modulator block110. Since the flange portion172of the sleeve170coupled to the outer surface of the magnet core140is directly fixed to the modulator block110, the assembly of the solenoid valve is facilitated and the manufacturing process of the solenoid valve is simplified.

The armature180is positioned inside the upper side of the sleeve170, that is, inside the domed closing portion171, and is installed to be reciprocated upward and downward. When power is applied to the excitation coil assembly (not shown), the armature180moves and pushes the plunger160, so that the orifice151is closed.

The solenoid valve100according to the embodiment of the present invention includes a passage hole142formed in an inner circumferential surface of the magnet core140, which faces the plunger160, in a lengthwise direction of the through-hole141, to prevent noise and degradation of the braking performance of the brake system that are caused by poor discharge of air remaining between the armature180and the magnet core140and between the magnet core140and the plunger160.

In more detail, referring toFIG. 2, the passage hole142is formed in a spiral shape on the inner circumferential surface of the magnet core140. Since the spiral is provided in a form rolling method by pressing a nut shaped form against the magnet core140having been subjected to forging, the manufacturing cost of the solenoid valve is reduced. In addition, the spiral shaped passage hole has a superior concentricity from being manufactured through the form rolling method, thereby effectively preventing center deviation of the plunger that may occur due to a repeated long-term use of the solenoid valve.

One end of the spiral communicates with a gap between the armature180and the magnet core140, and the other end of the spiral communicates with a gap between the magnet core140and the plunger160, for example, the other end of the spiral extends to the step portion165of the plunger160stepped outward to support the one end of the return spring190.

Accordingly, the narrow gap between the armature180and the magnet core140and the narrow gap between the plunger160and the magnet core140are expanded due to the spiral shaped passage hole142, so that air kept in the gaps is naturally discharged along a flow of oil caused by a motion of the plunger160. The passage hole142inclined with respect to the lengthwise direction of the magnet core140results in a superior flow of oil when compared to a passage hole formed in a lengthwise direction.

Referring toFIG. 4, a transfer passage hole146is formed in the spring support ledge145of the magnet core140in a lengthwise direction of the through-hole. Air discharged through the passage hole142and then through the transfer passage hole146is discharged to the orifice side, and finally discharged to the outside of the solenoid valve.

According to the embodiment of the present invention, the passage hole142and the transfer passage hole146connected to each other enable the air kept in the valve100to be easily discharged to the outside of the solenoid valve during the operation of the solenoid valve.

The following description will be made in relation on the opening/closing operations of the solenoid valve for the brake system.

When power is not applied to the excitation coil assembly (not shown), the return spring190pushes the plunger160toward the armature180such that the opening/closing portion161of the plunger160is spaced apart from the orifice151so that the orifice151remains open.

Accordingly, oil introduced through the first passage112passes through the radial passage142, the through-hole141, the orifice151and the connecting passage126, and finally flows to the second passage113. At the same time, oil introduced through the first passage112passes through the bypass passage123formed at the periphery portion121of the filter member120and finally flows to the second passage113.

In addition, air remaining between the magnet core140and the armature180and between the magnet core140and the plunger160may be easily discharged through the expanded passage formed by the passage hole142formed in the inner circumferential surface of the magnet core140and the transfer passage hole along a flow of oil caused by a motion of the plunger160.