Brake fluid pressure controlling actuator

A brake fluid pressure controlling actuator is equipped with a block, an electric device secured to the block, and a casing attached to the block, and a board support with a stay. The brake fluid pressure controlling actuator is designed to have the board support disposed in the casing and also have a circuit board placed in contact with the stay of the board support. The stay of the board support serves to firmly hold a portion of the circuit board around a through-hole formed in the circuit board when a terminal of an electric device is press-fitted into the through-hole, thereby minimizing the degree of bending of the circuit board to ensure the stability in electrically connecting the electric device to the circuit board.

CROSS REFERENCE TO RELATED DOCUMENT

The present application claims the benefit of priority of Japanese Patent Application No. 2014-106206 filed on May 22, 2014, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

This disclosure relates generally to a fluid pressure controlling actuator which is equipped with a casing, a circuit board which is disposed in the casing and to which an electric device working to control the pressure of brake fluid is connected, and a block in which a hydraulic brake circuit is formed and which is attached to the casing.

2. Background Art

Japanese Patent First Publication No. 2012-158228 discloses a brake fluid pressure controlling actuator made in the form of a unit which has a circuit board secured to a block in and on which a hydraulic pressure circuit and a variety of electric devices are disposed. The circuit board has disposed thereon a variety of electric parts for brake fluid pressure control, such as electromagnetic valves or an electric driver for an electric motor, and an electronic controller. The brake fluid pressure controlling actuator is equipped with a casing which covers the circuit board and electronic devices for waterproofing the circuit board. The casing has a portion which extends outside the block and to which a connector is secured to establish an electric connection between the circuit board and an external device.

Specifically, the casing has a first opening in which the electric devices are disposed and a second opening in which the connector is disposed. The first opening is secured to the block. The second opening has, as described above, the connector for achieving the electric connection with the external device.

The electric connection between the circuit board and the electric device such as the electromagnetic valve is achieved by press-fitting terminals extending from the electromagnetic valve into through holes formed in the circuit board.

The press-fitting of the terminals of the electromagnetic valve in the circuit board may, however, fail due to deflection of the circuit board when the terminals are inserted into the holes of the circuit board, which leads to a failure in connection between the circuit board and the electric devices.

SUMMARY

It is therefore an object to provide an improved structure of a brake fluid pressure controlling actuator designed to ensure the stability in electric connection between a circuit board and an electric device.

According to one aspect of the disclosure, there is provided a brake fluid pressure controlling actuator which comprises: (a) a block in which brake pipes are formed; (b) an electric device which is secured to a surface of the block and equipped with a terminal extending outside the block; (c) a casing which is secured to the block and has a wall which faces the surface of the block, the casing including an open chamber in which the electric device is installed; (d) a circuit board which is disposed within the casing so as to face the wall of the casing, the circuit board having a through-hole in which the terminal of the electric device is press-fit in an electric connection with the through-hole, the circuit board being equipped with an electric circuit which works to drive the electric device; and (e) a board support which is disposed on the wall of the casing within the casing. The board support is equipped with a stay which extends toward the circuit board and is placed in contact with a portion of the circuit board around the through-hole in which the terminal of the electric device is press-fit.

In short, the brake fluid pressure controlling actuator is designed to have the board support disposed in the casing and also have the circuit board placed in contact with the stay of the board support. The stay of the board support serves to firmly hold a portion of the circuit board around the through-hole when the terminal of the electric device is press-fitted into the through-hole, thereby minimizing the degree of bending of the circuit board to ensure the stability in electrically connecting the electric device to the circuit board.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, wherein like reference numbers refer to like parts in several views, particularly toFIG. 1, there is shown a brake fluid pressure controlling actuator1according to an embodiment.

The brake fluid pressure controlling actuator1is employed in a typical brake system for automotive vehicles. Specifically, the brake fluid pressure controlling actuator1is disposed between a master cylinder and a wheel cylinder of an automotive brake system to regulate the pressure of brake fluid to be delivered to the wheel cylinder.

The brake fluid pressure controlling actuator1includes a block2, electric devices such as electromagnetic valves3(also called solenoid valves) and an electric motor4, a circuit board5, a casing6, a board support7, and a retainer8.

The block2has brake pipes formed therein (not shown) as a hydraulic brake circuit for use in controlling the pressure of brake fluid. The block2is cuboid and has major opposed surfaces: a surface2aand a surface2b. The surface2ahas at least the electromagnetic valves3disposed thereon. The surface2bis opposed to the surface2ain a thickness-wise direction of the block2and has the motor4mounted thereon. The block2is made of, for example, a metal such as aluminum.

The electromagnetic valves3are arranged on the surface of the block2. Specifically, each of the electromagnetic valves3is equipped with a coil unit3aand has a portion other than the coil unit3a(which will also be referred to as a body below) fit in a chamber2gformed in the surface2aof the block2. For instance, the securement of each of the electromagnetic valves3to the block2is achieved by inserting the body into the chamber2gand swaging a portion of the block2to hold the body in the chamber2gtightly. The coil units3aare located outside the block2. Each of the coil units3ahas a terminal3bextending outside thereof. The terminal3belectrically leads to a solenoid coil installed in the coil unit3aand is also electrically connected to the circuit board5for energizing the solenoid coil.

The coil unit3ais detachable from the body of the electromagnetic valve3. This enables only the coil unit3ato be first connected to the circuit board5after which the body fit in the block2is joined to the coil unit3a.

The electric motor4is fixed on the surface2bof the block2. The block2has a pump9partially installed therein. The motor4is activated to drive the pump9to suck or discharge brake fluid for the brake fluid pressure control. The motor4has leads (not shown) which pass through, for example, holes extending from the surface2bto the surface2aof the block2and connect with the circuit board5. The joints of the leads of the motor4to the circuit board5may be achieved by soldering or press-fitting techniques.

The block2also has a pressure sensor which works to measure the pressure in the master cylinder. The electromagnetic valves3and the pressure sensor are electric devices covered by the casing6.

The circuit board5has disposed thereon electric circuits serving to driver electric devices such as the electromagnetic valves3and the electric motor4. The circuit board5extends outside the block2as viewed in a direction normal to the surfaces2aand2binFIG. 1, in other words, has a portion located on the right side of the block2, as viewed inFIG. 1, to which a connector10is attached. The connector10is equipped with a plurality of terminals10afit in the circuit board5. The terminals10aare electrically connected to the electric circuits on the circuit board5via through holes5apassing through the thickness of the circuit board5. The electric circuits on the circuit board5outputs or receives information to or from an external device through the connector10. Terminals3bof the electromagnetic valves3are press-fit in through-holes5bformed in the circuit board5to connect with the electric circuits on the circuit board5. The number of the through-holes5bcorresponds to that of the electromagnetic devices3.

The circuit board5also has an electronic control unit (ECU), not shown, mounted thereon to control operations of the electric devices. The electronic control unit works as a brake ECU to analyze signals inputted from the external device through the connector10or an output of the pressure sensor to control operations of the electronic devices to regulate the pressure of the brake fluid.

The casing6has open chambers6aand6bformed therein. The open chamber6afaces the block2. The open chamber6bhas the connector10disposed therein. The casing6in which the circuit board5is arranged is secured to the block2so that it covers the electronic devices mounted on the surface2aof the block2in a liquid-tight form.

Specifically, the open chamber6ahas a rectangular opening which is contoured to conform with the surface2aof the block2. The casing6is attached to the block2, so that the electronic devices secured to the surface2aof the block2are arranged inside the open chamber6a. For instance, the joining of the casing6to the block2is achieved by inserting screws into holes (not shown) formed in corners of the open chamber6aof the casing6and then fastening the screws into internally threaded holes (not shown) formed in corners of the surface2aof the block2.

The open chamber6bis located outside the block2, as viewed from a lower portion ofFIG. 1, so as to have the connector10exposed outside the block2. This enables the connector10to be electrically joined to the external device.

The casing6has an upper wall6copposed to the surface2aof the block2. The circuit board5is arranged so as to face the wall6c. It is preferable that the circuit board5is disposed to extend substantially parallel to the wall6c. The board support7is disposed along the wall6cwithin the casing6. The board support7has, as will be described later in detail, a plurality of stays7aextending from a major surface thereof away from the wall6c. The circuit board5is retained by the stays7aat a given interval away from the wall6cof the casing6. The circuit board5is less subjected to bending near the stays7a.

The casing6has a support6dwhich extends from the circumference of the wall6ctoward the circuit board5. The support6dis defined by a portion of a side wall6eextending over the whole of the circumference of the casing6. The support6dhas an end (i.e., an inner shoulder of the side wall6eof the casing6) laid flush with the ends of the stays7a, that is, the support6dhas a height from the wall6cof the casing6which is equal to that of the stays7a. In other words, the support6dextends to have the end contacting with the circuit board5, thereby supporting the periphery of the circuit board5. The stays7aand the support6dserve to hold the circuit board5away from the wall6cby the height of the stays7a. The support6dis, as described above, shaped so as to extend over the whole of the circumference of the casing6, but may alternatively be made of a plurality of portions of the side wall6eof the casing6which are arranged at given intervals away from each other in a circumferential direction of the casing6and extend toward the circuit board5.

The casing6has, as described above, the side wall6ewhich extends from the outer edge of the wall6cof the casing6toward the block2, in other words, extends parallel to a direction normal to the surface2aof the block2. The side wall6ehas, as clearly illustrated inFIG. 3, an insertion opening6fwhich is formed on one of side surfaces thereof and faces in a planar direction of the circuit board5. Specifically, the insertion opening6fis formed in the side surface of the side wall6eof the casing6which defines the open chamber6bin which the connector10is disposed. The insertion opening6fis, as can be seen fromFIG. 3, shaped to have a size large enough to enable the circuit board5to be inserted into the casing6. The casing6also has a cover6gfit in the insertion opening6f. The cover6ghas a sealing member (not shown) attached to an outer periphery thereof to establish a liquid-tight seal between the cover6gand the inner peripheral wall of the insertion opening6fwhen the cover6gis fit in the insertion opening6f. The cover6gmay be welded to the inner periphery of the insertion opening6for alternatively be press-fit in the insertion opening6f.

The casing6has a partition wall6hwhich defines the open chambers6aand6b. When the circuit board5is inserted into the casing6through the open chamber6a, it may result in physical interference with the partition wall6h. It is, thus, advisable that the circuit board5is disposed inside the casing6through the insertion opening6f.

The casing6is made of resin material, but may alternatively be made of metal as long as the electric circuits on the circuit board5are electrically insulated from the casing6. For instance, the electric insulation is achieved by printing conductive leads (i.e., conductive tracks or pads) of the electric circuits on an area of the circuit board5other than a contact with the support6d. The use of metal as material of the casing6enhances the thermal conductivity as compared with when the casing6is made of resin, thus facilitating the ease with which the heat, as generated from the electronic devices such as the brake ECU mounted on the circuit board5and the electromagnetic valves3, is dissipated outside the casing6. This results in improved thermal dissipation of the brake fluid pressure controlling actuator1.

The board support7is formed by a plate extending along the wall6cof the casing6. The plate may be made of an insulating material such as resin. The board support7is disposed in contact with the inner surface of the support6d, so that it is positioned in place within the casing6. The board support7, as described above, has the stays7aextending toward the circuit board5from one of the major surfaces thereof which is farther away from the wall6cof the casing6. The stays7aare, as clearly illustrated inFIG. 3, of a hollow cylindrical shape and arrayed substantially in coincidence with through-holes5bof the circuit board5in which the terminals3bof the electromagnetic valves3are fit. For instance, in the case where the brake fluid pressure controlling actuator1is of a so-called 8-sol type equipped with, as demonstrated inFIG. 3, the eight electromagnetic valves3, the eight stays7aare arrayed in alignment with the respective electromagnetic valves3. Each of the electromagnetic valves3has the two terminals3b. Each of the stays7aworks to support a portion of the circuit board5around corresponding two of the through-holes5b, thereby minimizing the bending of the circuit board5when the terminals3bof the electromagnetic valves3are press-fit in the through-holes5b, and thus ensuring the stability in electrically connecting the terminals3bwith the conductive through-holes5b.

Each of the stays7ais, as described above, of a hollow cylindrical shape, but may be made of a bar or formed to have another shape. In this embodiment, each of the stays7asupports the circuit board5around the terminals3bof a corresponding one of the electromagnetic valves3.

The board support7is disposed so as to occupy substantially the whole of the inner surface of the wall6cof the casing6, that is, extends across the partition wall6h, but may alternatively be shaped to face only the open chamber6a. In this case, the support6dis preferably shaped to extend around the outer periphery of the open chamber6b, so that it contacts with the periphery of the board support7to position the board support7in place within the casing6.

The retainer8is, as clearly illustrated inFIG. 3, made of a plate and disposed inside the open chamber6aof the casing6to press the circuit board5against the wall6c, thereby retaining the circuit board5in abutment with the end of the support6dand the ends of the stays7a. The retainer8may be secured to the casing6using screws. In this embodiment, the retainer8is press-fit in the casing6in abutment with the inner wall of the casing6which defines the open chamber6a. This eliminates the need for the screws, thus decreasing the number of parts of the brake fluid pressure controlling actuator1.

The retainer8includes supports8aformed by curved ends of the retainer8. The supports8aextend from a major portion of the retainer8in alignment with the support6dof the casing6, in other word, protrude toward contacts of the circuit board5with the support6d. The support6dand each of the supports8ahold the circuit board5tightly therebetween to retain the circuit board5firmly in the casing6.

The retainer8has formed therein openings or holes8blocated in alignment with the terminals3bof the electromagnetic valves3. Specifically, the terminals3bextend from below to above the retainer8, as viewed inFIG. 1, through the holes8band contact with the circuit board5. The retainer8also includes a plurality of elastic supports8cformed near the holes8b. Each of the elastic supports8cis curved so as to protrude toward a corresponding one of the electromagnetic valves3. Each of the elastic supports8cis made by drilling the plate-like major portion of the retainer8to as to form a strip or tab and bending the tab in a direction opposite a direction in which the supports8aextend from the major portion of the retainer8. Each of the elastic supports8cis placed, as clearly illustrated inFIG. 1, in contact with the upper end of one of the electromagnetic valves3which faces the circuit board5, so that it elastically presses the electromagnetic valve3against the block2, thereby suppressing mechanical vibration of the electromagnetic valve3. This eliminates dislodgement of the terminals3bfrom the through-holes5bof the circuit board5due to the vibration of the electromagnetic valves3and thus ensures the stability of electric connection of the terminals2bwith the circuit board5.

The production method of the brake fluid pressure controlling actuator1will be described below with reference toFIGS. 2(a), 2(b), 2(c), and3.

First, the casing6with the insertion opening6fnot closed by the cover6gis prepared. The board support7is inserted into the casing6through the open chamber6aor the insertion opening6f. The board support7is then placed in direct contact with the inner surface of the wall6cof the casing6. Afterwards, the circuit board5is put into the casing6through the insertion opening6f. The board support7may be laid across the partition wall6hin contact with substantially the whole of the inner surface of the wall6c. In this case, it is advisable that the board support7be inserted through the insertion opening6f. The board support7, however, may be inserted into the casing6through the open chamber6a. The board support7may alternatively be laid so as to face only the open chamber6a. In this case, it is advisable that the board support7be inserted into the casing6through the open chamber6aand laid in contact with a portion of the inner surface of the wall6cwhich is oriented to the open chamber6a.

Subsequently, the retainer8is, as illustrated inFIGS. 2(b)and3, press-fit into the open chamber6aand urges the circuit board5at the supports8aagainst the supports6dof the casing6, thereby holding the circuit board5firmly through the supports6dand8a.

Afterwards, the insertion opening6fis closed by the cover6g. The attachment of the cover6gto the casing6may be achieved by press-fitting the cover6gwith the sealing member installed around the circumferential edge thereof into the insertion opening6f. This eliminates the need for, for example, a vibration welding machine, to weld the cover6gto the casing6, thus facilitating the ease with which the cover6gis secured to the casing6. A portion of the wall6cmay be made as a cover separate from the other portion of the wall6cto form an opening in the wall6cin order that the circuit board5is put into the casing6through the opening. This, however, requires the need for hermetically sealing a wider area around the opening of the wall6c. The cover6gmay be made to be small in size, thus ensuring the stability in hermetically sealing around the cover6g.

The coil units3aare put into the casing6through the open chamber6a. Simultaneously, the terminals3bof the coil units3aare press-fit into the through-holes5b. This establishes physical and electrical connections of the terminals3awith a metallic coat on the inner surfaces of the through-holes5b. The connector10is put into the open chamber6bto connect the terminals10aof the connector10physically and electrically to the electric circuits on the circuit board5. The electrical connections of the terminals10ato the electric circuits on the circuit board5may be accomplished, like the terminals3b, by press-fitting the terminals10ainto the through-holes5awhose inner surfaces are coated with conductive material.

The block2is prepared, as illustrated inFIGS. 2(c)and3, to which the bodies of the electromagnetic valves3other than the coil units3aand the electric motor4are secured. The block2is put on the casing6so as to close the open chamber6a. The mechanical joint of the block2to the casing6may be achieved by inserting screws into holes (not shown) formed in corners of the open chamber6aof the casing6and then fastening the screws into internally threaded holes (not shown) formed in corners of the surface2aof the block2. This completes the brake fluid pressure controlling actuator1, as illustrated inFIG. 1.

As apparent from the above discussion, the brake fluid pressure controlling actuator1is designed to have the board support7disposed in the casing6and also have the circuit board5placed in contact with the stays7aof the board support7. Each of the stays7aof the board support7serves a press to firmly hold a portion of the circuit board5around at least a corresponding one of the through-holes5bwhen the terminals3bof the electromagnetic valves3are press-fitted into the through-holes5b, thereby minimizing the degree of bending of the circuit board5to ensure the stability in electrically connecting the electromagnetic valves3to the circuit board5.

The retainer8is disposed on the opposite side of the circuit board5to the wall6cof the casing6so as to hold the circuit board5tightly between the supports6dand8a. In other words, the circuit board5is retained at a plurality of supports in place within the casing6, thus ensuring the stability in securement of the circuit board5at a preselected position within the casing6.

The retainer8is equipped with the elastic supports8cto elastically urge the electromagnetic valves3against the block2, thereby absorbing the mechanical vibrations of the electromagnetic valves3being in operation to avoid the dislodgement of the terminals3bfrom the through-holes5b. This minimizes the risk of electrical disconnection of the electromagnetic valves3from the circuit board5.

While the present invention has been disclosed in terms of the preferred embodiment in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention.

The cover6bis, as described above, separate from the circuit board5, however, an assembly of the circuit board5and the cover6gwhich is, as illustrated inFIG. 4, secured or adhered to the end of the circuit board5may be prepared and inserted into the casing6through the insertion opening6f. The casing6may be, as illustrated inFIG. 5, shaped to have the insertion opening6fand the cover6gwhich are both greater in size than the ones in the above embodiment. The cover6gis attached to the end of the circuit board5. The connector10is attached to the circuit board5. This assembly is inserted into the casing6through the insertion opening6f.

The block2may be attached to the casing6without using screws. For instance, such attachment may be achieved by inserting a portion of the block2into the open chamber6aand swaging a portion of the casing6around the open chamber6ato make a mechanical joint with the block2or welding a contact between the block2and the casing6which are made of the same metallic material. The casing6may be made of die-cast aluminum. In this case, the swaging of the casing6to make a mechanical joint with the block2is achieved easily.

The pump9is illustrated as being a trochoid pump, however, it may be engineered as a plunger pump.

The insertion opening6fis formed in one of four faces of the side wall6eof the casing6which, as can be seen inFIG. 3, directly faces, in other words, is closest to the side surface of the connector10, however, may alternatively be made in another face of the side wall6e, for example, one of the faces of the side wall6efarther away from the connector10or extending perpendicular to the face of the side wall6e, as illustrated inFIG. 3, in which the insertion opening6fis formed.