Abstract:
A solenoid valve for use in an actuator for controlling brake hydraulic pressure includes a valve housing, a movable core having an integral valve rod and axially slidably received in the valve housing, and a valve body configured to be moved into and out of contact with a valve seat when the valve body moves. The solenoid valve further includes a yoke having a U-shaped section. Even with such a U-shaped yoke, it is possible to form a magnetic path. Compared to tubular yokes, it is possible to reduce its width and thus the width of the solenoid valve by an amount equal to the thickness of tubular yokes. Thus, by arranging such solenoid valves in an actuator for controlling brake hydraulic pressure such that the width directions of the respective solenoid valves coincide with the height direction of the actuator, in which it is required to reduce the size of the actuator, it is possible to reduce its size in this direction. The flanges of the yoke have first ends that extend substantially along the outer peripheral edges of the coil winding to minimize the length of the flanges and thus the length of the solenoid valve.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based on and claims priority under 35 U.S.C. sctn. 119 with respect to Japanese Patent Application No. 2005-327724 filed on Nov. 11, 2005, No. 2005-327740 filed on Nov. 11, 2005, and No. 2006-218778 filed on Aug. 10, 2006, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to an actuator for controlling brake hydraulic pressure in a vehicle brake system, and solenoid valves used therein.  
         [0003]     As shown in  FIGS. 6 and 7 , a typical actuator A for controlling brake hydraulic pressure in a vehicle brake system A comprises a hydraulic unit  1 , a motor unit  2  mounted to one end of the hydraulic unit  1 , and an electronic control unit (ECU)  3  mounted to the other end of the hydraulic unit  1 .  
         [0004]     Typically, the hydraulic unit  1  includes a reservoir  12 , a pump  13 , pressure increasing control valves  20  and pressure reducing control valves  30 , which are all mounted in a housing  10  made of aluminum. The housing  10  is formed with a master cylinder port  14  and wheel cylinder ports  15  which communicate with the master cylinder port  14  through passages  16  in which the pressure increasing valves  30  are disposed. The wheel cylinder ports  15  also communicate with the reservoir  12  through passages  17  in which the pressure reducing valves  20  are disposed and through passages  18  in which the pump  13  and the pressure increasing valves  30  are disposed. This arrangement is shown in JP patent publication 2005-7955A.  
         [0005]     The control valves  20  and  30  of the hydraulic unit  1  are solenoid valves. Typically, as shown in  FIG. 8  and also in  FIG. 2  of JP patent publication 2005-7955A, the pressure increasing control valves  30  each include a tubular yoke  31 , a tubular bobbin  32  received in the tubular yoke  31 , a current-excited coil  33  wound around the bobbin  32 , and a movable core (plunger)  34  having a valve rod  35  and axially movably received in the bobbin  32  through a guide (valve housing)  36 . A valve body  37  is disposed at the free end of the valve rod  35  and is moved into and out of contact with a seating surface  38 a of a valve seat  38  by the core  34 . In  FIG. 8 , numeral  4  indicates a terminal through which electricity is supplied to the coil  33 , and  39  indicates a return spring for the valve rod  35 .  
         [0006]     Ordinarily, this type of actuator A includes eight or more hydraulic pressure control valves V (solenoid valves  20  and  30 ) that are arranged in a plurality of rows and a plurality of columns. In order to facilitate mounting of such control solenoid valves  20  and  30  (which are sometimes referred to as “control solenoid valves V” or “solenoid valves V”), as shown in  FIG. 9 , JP patent publication 09-118215A discloses an arrangement in which the yokes  31  of the respective eight solenoid valves V are integrally formed (see  FIG. 3  of this publication). The yokes  31  have a substantially U-shaped cross-section and are arranged in two rows such that the yokes in each row are mirror images of the yokes in the other row with their openings facing the openings of the yokes in the other row. In each of the (eight) yokes  31 , a coil  33  is mounted.  
         [0007]     The conventional solenoid valve V shown in  FIG. 8  has the tubular yoke  31  (circular in section). A plurality of such solenoid valves V are mounted in the housing  10  at predetermined intervals as shown in  FIG. 10 .  
         [0008]     With an increase in the number of electronic devices used in today&#39;s vehicles, it is increasingly required to reduce the size and cost of individual parts thereof, including an actuator A mounted in the engine compartment for controlling brake hydraulic pressure. It is especially required to reduce the height H (see  FIG. 6 ) of the actuator A.  
         [0009]     In order to reduce the height H of the actuator A, in the arrangement of  FIG. 10 , the solenoid valves V are arranged at shorter intervals in the direction of the height H of the actuator. But even with this arrangement, it is often difficult to sufficiently reduce the height H of the actuator.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the present invention is to reduce the size, especially the height, of an actuator for controlling brake hydraulic pressure.  
         [0011]     According to the present invention, this object is achieved by reducing a width of each solenoid valve of an actuator for controlling brake hydraulic pressure and mounting a plurality of such solenoid valve in the actuator such that the width direction of each solenoid valve coincides with a direction (e.g. the height direction) of the actuator in which it is required to reduce the size of the actuator.  
         [0012]     The solenoid valve according to the present invention includes a yoke having a substantially U-shaped section, based on the finding that a yoke having a U-shaped section can achieve its expected function, i.e. the function of forming a magnetic path. Since such a U-shaped yoke has a width smaller than the outer diameter of conventional tubular yokes, the solenoid valve according to the present invention has a smaller width W 1  ( FIG. 4 ) than conventional solenoid valves including tubular yokes. By arranging a plurality of such solenoid valves in the housing of an actuator for controlling brake hydraulic pressure such that the width directions of the respective solenoid valves coincide with the direction of the actuator in which it is required to reduce the size of the actuator, it is possible to reduce the size of the actuator in this direction.  
         [0013]     In this arrangement, each flange preferably has a first end extending substantially along the circular outer peripheral edge of the coil winding, thereby minimizing the length of the flanges of the yoke and thus the dimension of the entire solenoid valve in the width direction of the flanges.  
         [0014]     Specifically, according to the present invention, there is provided a solenoid valve for an actuator for controlling brake hydraulic pressure, the solenoid valve comprising a yoke comprising a pair of parallel flanges each having first and second ends and a web connected to the second ends of the flanges, the yoke having a substantially U-shaped section, a bobbin received in the yoke, a current-excited coil wound around the bobbin, forming a coil winding, a movable core provided inside the bobbin so as to be movable in an axial direction of the bobbin, and including a valve rod, a valve body disposed at a free end of the valve rod, and a valve seat having a seating surface, the valve body being configured to be moved into and out of contact with the seating surface of the valve seat when the movable core moves in the axial direction of the bobbin, the flanges having a width that is greater than a diameter of the coil winding and smaller than the sum of the diameter of the coil winding and twice the thickness, preferably the thickness, of the yoke, the flanges each having the first end thereof extending substantially along an outer peripheral edge of the coil winding, a plurality of the solenoid valves being configured to be mounted, independently of each other, in a housing of the actuator in a plurality of rows and a plurality of columns.  
         [0015]     A plurality of such solenoid valves are mounted in a housing of an actuator for controlling brake hydraulic pressure so as to be arranged in a plurality of rows and a plurality of columns in the same manner as conventional actuators. By arranging the solenoid valves such that the length directions of the flanges of the yokes thereof coincide with each other, it is possible to minimize the dimension of the actuator in the length directions of the flanges.  
         [0016]     For example, if eight of such solenoid valves are mounted in the housing of the actuator for controlling brake hydraulic pressure, they may be arranged in two rows, each row comprising four of the eight solenoid valves, with two of the four solenoid valves in each row that are at both ends of the row each positioned such that the first ends of the flanges of the yoke thereof face toward or away from the other three solenoid valves in the row.  
         [0017]     By arranging the solenoid valves such that the length directions of the flanges of their yokes coincide with each other, the solenoid valves can be easily mounted in the housing.  
         [0018]     The solenoid valves may be arranged such that the length directions of the flanges of their yokes coincide with the width direction of the actuator.  
         [0019]     If more than eight such solenoid valves (hydraulic pressure control valves) are mounted in the actuator, at least eight of them are arranged as described above.  
         [0020]     The solenoid valve according to the present invention has a smaller width, and thus takes up less mounting space, than conventional solenoid valves. By mounting a plurality of such solenoid valves in an actuator for controlling brake hydraulic pressure, it is possible to reduce the size of the actuator too. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:  
         [0022]      FIG. 1  is a partially cutaway front view of a portion of an actuator for controlling brake hydraulic pressure embodying the present invention;  
         [0023]      FIG. 2  is a partially cutaway front view of a solenoid valve in the actuator of  FIG. 1 ;  
         [0024]      FIG. 3  is a perspective view of the solenoid valve of  FIG. 2 ;  
         [0025]      FIG. 4  is a plan view of the solenoid valve of  FIG. 2 ;  
         [0026]      FIGS. 5A  to  5 H show different arrangements of a plurality of solenoid valves according to the present invention in an actuator for controlling brake hydraulic pressure;  
         [0027]      FIG. 6  is a schematic perspective view of an actuator for controlling brake hydraulic pressure;  
         [0028]      FIG. 7  is a front view of the actuator of  FIG. 6 ;  
         [0029]      FIG. 8  is a partially cutaway front view of a pressure increasing valve for an actuator for controlling brake hydraulic pressure;  
         [0030]      FIG. 9  is a partial exploded perspective view of a conventional actuator for controlling brake hydraulic pressure; and  
         [0031]      FIG. 10  shows how conventional solenoid valves are arranged in an actuator for controlling brake hydraulic pressure. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]     FIGS.  1  to  4  show a solenoid valve  30  embodying the present invention, which is a pressure increasing control valve including, like conventional valves, a yoke  31 , a bobbin  32  received in the yoke  31 , a current-excited coil  33  wound around the bobbin  32 , a movable core  34  having a valve rod  35  and axially movably received in the bobbin  32 , and a valve body  37  disposed at the free end of the valve rod  35  and moved into and out of contact with a seating surface  38   a  of a valve seat  38  by the movable core  34  (see  FIG. 2 ).  
         [0033]     In these figures and the figures showing the prior art, like elements are denoted by like numerals. The solenoid valve of  FIG. 2  further includes a check valve  41 , a filter  42 , and a ring  43  pressed into a valve housing  36  to fix the filter  42  in position.  
         [0034]     In this embodiment, the yoke  31  and the coil  33  are separable from the valve housing  36  by sliding the former along the latter. More specifically, a coil assembly C 1  (see  FIG. 2 ) comprising the yoke  31 , bobbin  32  and coil  33  is separable from a main body C 2  including the valve housing  36 , which is fixed to a housing  10  of the hydraulic unit, and the movable core  34  including the valve rod  35  by upwardly (in  FIG. 2 ) sliding the former relative to the latter (in the manner as shown in  FIG. 9 ).  
         [0035]     Unlike conventional yokes, the yoke  31  of this embodiment comprises upper and lower flanges  31 a having first and second ends and a web  31   b  through which the second ends of the flanges  31   a  are joined together and thus has a substantially U-shaped cross-section, with the flanges  31   a  having a width W 1  (see  FIG. 4 ) that is greater than the outer diameter s of the winding of the coil  33  and smaller than the sum of the outer diameter s of the winding of the coil  33  and the thickness t (see  FIG. 3 ) of the yoke  31  (s&lt;W 1 &lt;s+t).  
         [0036]     With this arrangement, the width of the solenoid valve  30  is equal to the width W 1  of the flanges  31   a.    
         [0037]     In this embodiment, as shown in  FIG. 3 , the lower flange  31   a  has its first end  31   c  arcuately curved substantially along the circular outer peripheral edge of the winding of the coil  33 . The upper flange  31   a  has its first end  31   c  disposed slightly radially inwardly from the circular outer peripheral edge of the winding of the coil  33  to such an extent that a magnetic path is formed by the yoke and the upper flange can stably guide the movement of the core  34 . But instead, the lower flange  31   a  may have its first end  31   c  disposed slightly radially inwardly as with the upper flange  31   a  to such an extent that a magnetic path is formed by the yoke and the lower flange can stably guide the movement of the core  34 . Also, the upper flange  31   a  may have its first end  31   c  arcuately curved substantially along the circular outer edge of the winding of the coil as with the lower flange  31   a.    
         [0038]     With this arrangement, it is possible to minimize the length W 2  (i.e. the dimension perpendicular to the width W 1 ; see  FIG. 4 ) of the flanges  31   a  and thus the length of the solenoid valve  30 .  
         [0039]     Lead terminals  4  connected to the coil  33  extend through terminal support pieces  32   a  (see  FIG. 3 ) of the bobbin  32  provided near the first end of the upper flange  31   a , and protrude from the respective terminal support pieces  32   a . Each lead terminal  4  comprises a first portion protruding upwardly (in  FIG. 1 ) from the terminal support piece  32   a , a second bent portion extending from the free end of the first portion toward the web  31   b , and a third portion extending upwardly from the free end of the second bent portion.  
         [0040]     A pressure reducing control valve  20  according to the present invention is also of substantially the same structure as the above-described pressure increasing control valve  30 .  
         [0041]     The actuator according to the present invention includes solenoid valves V comprising a plurality of the above-described pressure increasing valves  30  and a plurality of the above-described pressure reducing valves  20  that are arranged in a plurality of rows and a plurality of columns such that the direction of the width W 1  of the yoke of each valve V coincides with a direction of the actuator in which it is desired to reduce the dimension of the actuator, typically the direction of the height H of the actuator in  FIG. 6 .  
         [0042]     For example, if the actuator includes eight such solenoid valves (control valves) V, they may be arranged as shown in  FIGS. 5A and 5B . If the actuator includes ten such solenoid valves V, they may be arranged as shown in  FIGS. 5C  to  5 H.  
         [0043]     With this arrangement, the orientation of the first ends of the flanges  31   a  of each yoke (orientation in the length direction of the flanges  31   a ) is determined according to the structure of the housing  10 . For example, in the arrangements of  FIGS. 5A, 5C ,  5 D and  5 G, the two solenoid valves V on each side of each of two rows each consisting of four solenoid valves V are oriented such that the first ends of their flanges face away from the two valves on the other side of the row. In the arrangements of  FIGS. 5B, 5E ,  5 F and  5 H, the two valves on each side of each of two rows each consisting of four solenoid valves V are oriented such that the first ends of their flanges face toward the two valves on the other side of the row.  
         [0044]     Also, the position and orientation of each solenoid valve V are preferably determined taking into consideration the shape of the mounting surface (surface of the sheet of each drawing) of the housing  10 . For example, if it is necessary to mount a solenoid valve V near an arcuately curved portion of the mounting surface, the solenoid valve V is preferably positioned and oriented such that its arcuately curved portion is disposed in juxtaposition with the arcuately curved portion of the mounting surface (as shown in  FIGS. 5C and 5E ). If it is necessary to mount a solenoid valve V near an angular portion of the mounting surface, the solenoid valve V is preferably positioned and oriented such that its angular portion is disposed in juxtaposition with the angular portion of the mounting surface (as shown in  FIGS. 5D and 5F ).  
         [0045]     In the embodiments shown in  FIGS. 5A  to  5 H, the solenoid valves V are arranged such that the width direction of the flanges  31   a  of each solenoid valve V coincides with the direction of the height (H in  FIG. 6 ) of the housing  10  (actuator A). Thus, if the diameter of the winding of the coil  33  of each solenoid valve V is the same, the actuator according to the present invention has a smaller height H than conventional actuators of this type.  
         [0046]     As shown in  FIGS. 1 and 3 , the solenoid valves V are provided so as to face a housing  5  of an electronic control unit (ECU)  3 . The ECU housing  5  is formed with holes  6  at positions corresponding to the lead terminals  4  of the respective solenoid valves V. Busbars  7  connected to a control circuit for the solenoid valves V protrude from the inner wall of each hole  6 .  
         [0047]     Each busbar  7  protrudes from the inner wall of the hole  6  at point P 1  disposed, as viewed from the axial direction of the solenoid valve (see  FIG. 4 ), between the center of gravity g of the coil assembly C 1  and the points P 3  at which the pair of lead terminals  4  are connected to the coil  33  (leftwardly of the center of gravity g in  FIG. 4 ).  
         [0048]     The ECU housing  5  is formed by resin molding with the busbars  7  inserted therein. Each of the pair of busbars  7  comprises a first portion extending from point P 1  in a direction perpendicular to the axis of the winding of the coil  33 , a second bent portion extending axially of the winding of the coil  33  from the free end of the first portion, and a third bent portion extending in a direction perpendicular to the axis of the winding of the coil  33  from the free end of the second bent portion toward the other busbar  7 . The third bent portion of each busbar  7  is fixed to and connected to the third portion of the corresponding lead terminal  4  at point P 2  as shown in  FIG. 3 .  
         [0049]     With this arrangement, as viewed from the axial direction of the solenoid valve V (see  FIG. 4 ), points P 2  are located between points P 1  and points P 3 .  
         [0050]     The solenoid valves V are mounted in the housing  10  of the hydraulic unit as shown in  FIG. 1  with the valves V shown disposed one over the other. Thus, each coil assembly C 1  is supported in cantilever fashion by the busbars  7  and the lead terminals  4 , which are fixed to the busbars  7  at points P 2 .  
         [0051]     Generally speaking, when each coil assembly C 1  is supported by the pair of lead terminals  4  of the coil  33  and the pair of busbars  7  of the ECU which are connected to the lead terminals  4  at points P 2 , if the points P 2  are located on the straight line parallel to the axis of the coil winding and passing the center of gravity g of the coil assembly C 1 , moment will scarcely act or not act at all on the connecting points P 2  even if the coil assembly C 1  moves (vibrates) relative to the valve housing  36 .  
         [0052]     Also, the greater the distance between the points P 3  and the points P 1 , the larger the deflection of the coil assembly C 1 , which in turn increases stress acting on the connecting points P 2  between the lead terminals  4  and the busbars  7 . Because the stress on the connecting points P 2  is produced by the moment based on the weight of the coil assembly C 1  and proportional to the distance between points P 1  and points P 3 , this distance is preferably as small as possible in order to reduce the moment that acts on the contact points P 2 .  
         [0053]     Thus, in order to reduce the stress on the connecting points P 2  between the lead terminals  4  and the busbars  7 , which results from deflection of the coil assembly C 1 , the points P 1 , at which the busbars  7  protrude from the ECU housing  15 , are preferably located, as viewed from the axial direction of the winding of the coil  33 , between the center of gravity g of the coil assembly C 1  and the points P 3 , at which the lead terminals  4  extend from the coil  33 .  
         [0054]     In this embodiment, because busbars  7  and the lead terminals  4  are connected together and each coil assembly C 1  is supported so as to satisfy all of the above-described requirements, it is possible to minimize stress on the connecting points P 2  due to deflection of the coil assemblies C 1 .  
         [0055]     When the ECU housing  5  is mounted on the hydraulic unit housing  10 , protrusions  5   a  (see  FIG. 3 ) formed on the bottom surface of the ECU housing  5  abuts the yokes  31  of the respective solenoid valves  30 (V). The solenoid valves  30 (V) (coil assemblies C 1 ) are thus securely sandwiched between the hydraulic unit housing  10  and the ECU housing  5 , and additionally held in position by the protrusions  5   a . This minimizes deflection of the valves  30 (V) (coil assemblies C 1 ).  
         [0056]     If it is necessary to reduce the width WA (see  FIG. 6 ) of the actuator A, each solenoid valve V is arranged such that the direction of the width W 1  of its flanges  31   a  coincides with the direction of the width WA of the actuator A.  
         [0057]     Various modifications and alterations can be made to the embodiments without departing from the spirit of the present invention. For example, connecting points P 2  between the lead terminals  4  and the respective busbars  7  may not be disposed between the points P 1  and points P 3 . The abovementioned second bent portion and/or third portion of each lead terminal  4  may be omitted. Also, the abovementioned second bent portion of each busbar  7  may be omitted.  
         [0058]     A motor unit  2  and the ECU  3  may be mounted to the opposed sides of the hydraulic unit housing  10  as shown in  FIGS. 6 and 7 . But instead, the motor unit  2  and the ECU  3  may be mounted to the same one side of the hydraulic unit housing  10 . Also, the motor unit  2  may be mounted not to the hydraulic unit housing  10  but to a different member.