Brake fluid pressure control unit

Abstract: Brake fluid pressure control unit improved for smaller size and lower cost. A motor (1) for a pump (3) is mounted in the circuit block (2) and the pump (3) is mounted on one axial end of the motor (1). The pressure adjusting units (26) having solenoid valves (4a) are arranged around the motor (1). The case (1a) of the motor (1) has a portion (16) forming a part of a magnetic circuit through which magnetic fluxes produced in the coils (4e) of the solenoid valves (4a) flow.

Description: The present invention relates to a brake fluid pressure control unit for controlling the brake fluid pressure in the wheel cylinders in response to commands from an electronic control unit, thereby preventing wheel locking. Such a brake fluid pressure control unit is used to add the antilock or traction control function to a vehicle brake device. It comprises a fluid pressure pump, an electric motor for driving the pump, and solenoid valves for opening and closing the fluid passages between the master cylinder and the wheel cylinders and the discharge passages leading from the wheel cylinders. Fig. 6 shows one of such control units that is disclosed in US-A-4953918. A circuit block 2 is mounted to the front part of a motor 1. This block houses a hydraulic pump 3 (generally a plunger pump) driven by the motor 1 and fluid passages opened and closed by solenoid valves 4a. As shown in the figure, a conventional brake fluid pressure control unit has its circuit block 2, which comprises a pump unit 2a and a pressure adjusting unit 2b, disposed in front of the motor 1 and its solenoid valves 4a attached to the pressure adjusting unit 2b so as to extend in a direction perpendicular to the motor. Since the motor 1 and the circuit block 2 were disposed in series with each other, conventional control units were rather large in size. Further, it was necessary to attach a magnetic circuit to each of a plurality of solenoid valves in each unit to guide the magnetic flux produced in the coil to the yoke. Thus, conventional control units required a large number of parts and were thus expensive. On the other hand, in SAE PAPER 920647 is disclosed a control unit having its solenoid valves disposed in parallel around the outer periphery of the motor to reduce its overall size. But this arrangement also requires two separate cases, one for the motor and the other for the solenoid valves. Thus, the overall size of the unit is large and the cost high. The control unit disclosed in FR-A-2 301 417, which shows all the features of the preamble of claim 1, comprises a motor carrying a pump at one axial end thereof and solenoid valves of pressure adjusting means mounted to the motor in positions radially offset with respect to the pump pistons of said pump. The case of the pressure adjusting means, however, extends considerably axially from the end of the motor to which the pump is mounted. Thus, this unit also requires two cases, even if these are integrally formed. This leads to a relatively large size of this control unit. An object of the present invention is to provide a brake fluid pressure control unit which is small in size and inexpensive. The invention achieves this object with the features of patent claim 1. Especially, in order to provide a compact structure, the pump unit of the circuit block is mounted on one axial end of the motor and the pressure adjusting means is provided to surround the outer periphery of the motor. As the rear cover alone or both the rear cover and the body case of the motor are also used as a part of the magnetic circuit of the motor and that of the solenoid valves, the number of parts and the costs and weight of the entire unit are reduced. In a preferred embodiment of the invention the circuit block is made of magnetizable material, a portion thereof serving as the body case of the motor and forming a part of said magnetic circuit. In another preferred embodiment of the invention the rear cover has a portion protruding outwards from the outer periphery of the motor, the solenoid valves being kept in position by the protruding portion of the rear cover against the brake fluid pressure. In a further preferred embodiment of the invention the rear cover of the motor has a housing in which is mounted an electronic control unit having a microcomputer. Connectors from the solenoid valves and the motor are guided into the housing and electrically connected to a control circuit of the electronic control unit. Thus the space for the fluid pressure control unit can be utilized efficiently and the entire length of wiring from the solenoid valves and the motor to the electronic control unit can be reduced to a minimum. This leads to a further reduction in size, weight and costs. Moreover, the fluid pressure control unit and the electronic control unit can be integrated into a one-piece unit before shipping. This greatly facilitates handling. Also, such a one-piece unit can be mounted on a car much more easily. This serves to reduce the size, weight an costs of the entire brake system. Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: Fig. 1 is a plan view showing one embodiment of the brake fluid pressure control unit; Fig. 2 is a side view partially cut away along line II-II of Fig. 1; Fig. 3 is an enlarged sectional view of a portion of another embodiment; Fig. 4 is a partially cutaway side view of a portion of a further embodiment; Fig. 5 is a partially cutaway side view of a portion of still another embodiment; and Fig. 6 is a side view of a prior art control unit. Figs. 1-5 show a preferred embodiment of the brake fluid pressure control unit according to the present invention. A motor 1 is fitted in a recess 5 formed in a circuit block 2 with part of its body case 1a and part of its rear cover 1b protruding from the circuit block 2. Mounted in the circuit block 2 are a pressure adjusting unit 2b including pressure adjusting means 4 and a pump unit 2a. The positional relation between the units 2a and 2b are opposite to the conventional arrangement, with the unit 2b surrounding the outer periphery of the motor 1. The pressure adjusting means 4 are provided at a radial outer position of the rotor 1d of the motor 1 and include a flow control valve. Since such a valve is disclosed in US-A-4915459, it is deemed not necessary to describe it in detail. Solenoid valves 4a are secured to the rear face of the pressure adjusting unit 2b at its four corners so as to be parallel to the motor 1. The motor rear cover 1b is secured to the circuit block 2 by means of bolts 6 so as to protrude outwardly from the body case 1a to support coils 4e of the solenoid valves 4a thereon. The solenoid valves 4a are urged by the brake fluid pressure in such a direction as to get out of the circuit block 2. The force urging the valves 4a is borne by the rear cover 1b. Each solenoid valve has a stator 4b and a yoke 4d that are integral with the coil 4e. Thus, simply by tightening the bolts 6, the solenoid valves 4a as well as the motor 1 can be fixed in position. The control unit is thus assembled easily. The body case 1a, made of a magnetizable material, serves as a magnetic circuit. Namely, the magnetic flux produced in the coil of the motor 1 flows into the body case 1a. The magnetic flux produced in the coils 4e of each solenoid valve 4a flows through the stator 4b, armature 4c, yoke 4d and rear cover 1b. In other words, these parts act as a magnetic circuit. Thus, there is no need to provide extra members for forming a magnetic circuit between the yoke 4d and the stator 4b. Also, no coil support member is needed. The number of parts is thus small. The motor body case 1a is reinforced by the circuit block 2, so that the former can be formed of a thin and low-strength material. This leads to a reduction in weight of the entire unit. Further, as shown in Fig. 3, the motor body case 1a may be used as part of the magnetic circuit of each solenoid valve coil 4e shown by arrow. With this arrangement, the yokes (4d of Fig. 2) provided around each coil can be omitted, so that the number of parts and the overall weight can be reduced still further. The circuit block 2 may be formed of a magnetizable material so as to use it as the body case 1a of the motor. As shown in Fig. 4, the circuit block 2 serves as a common magnetic circuit member for all the solenoid valves 4a. Fig. 5 shows an embodiment in which an electronic control unit 9 is mounted in the motor rear cover 1b. The rear cover 1b has a hollow space 10 in which is mounted the electronic control unit 9, which comprises a circuit board 9a and a microcomputer (not shown). Similar to the arrangement of Fig. 2, the solenoid valves 4a are kept in position by the rear cover 1b against the brake fluid pressure acting thereon. Also, lead pins 4f coupled to both ends of the coil 4e are inserted into the hollow space 10 through holes formed in the cover 1b and electrically connected to an electrical circuit on the circuit board 9a. Another lead pin 1f, which extends from a brush base 1e coupled to a brush 1c of the motor 1, is electrically connected to a corresponding circuit on the circuit board 9a in the same manner as with the lead pins 4f. The pressure adjusting means 4 may not include a flow control valve as disclosed in US-A-4915459 but may consist of a solenoid valve only as shown in US-A-3617098. With this arrangement, since the rear cover 1b of the motor also serves as a housing for the electronic control unit, the fluid pressure control unit and the electronic control unit can be easily housed in a single unit. This will save space and simplify the wiring. As shown in Fig. 1, this control unit has input ports 7 communicating with the master cylinder and output ports 8 leading to the wheel cylinders. The solenoid valves 4a serve to open and close the discharge circuits between the wheel cylinders and a low-pressure reservoir connected to the intake ports of pumps 3.

Claims: A brake fluid pressure control unit provided in a fluid passage extending between a master cylinder and wheel cylinders to control the brake fluid pressure in said wheel cylinders, said control unit comprising a circuit block (2) having a pump (3), a motor (1) for driving said pump, and a pressure adjusting means (4) including solenoid valves (4a) for opening and closing fluid passages, said pump (2a) in said circuit block (2) being mounted on one axial end of said motor (1) and said pressure adjusting means (4) being provided so as to surround the outer periphery of said motor (1), said solenoid valves being provided parallel to the motor (1), said motor (1) having a body case (1a) provided at the outer periphery of a rotor (1d) of said motor and a rear cover (1b) provided at the other axial end of said motor (1), characterized in said pressure adjusting means (4) being provided at a radial outer position of a rotor (1d) of said motor (1) and said rear cover (1b) alone or both said rear cover (1b) and said body case (1a) being made of magnetizable material and forming a part of the magnetic circuit through which magnetic fluxes produced in the coils (4e) of said solenoid valves pass. A brake fluid pressure control unit as claimed in claim 1, characterized in that said circuit block (2) is made of magnetizable material, a portion thereof serving as said body case (1a) of said motor (1) and forming a part of said magnetic circuit. A brake fluid pressure control unit as claimed in claims 1 or 2, characterized in said rear cover (1b) having a portion protruding outwards from the outer periphery of said motor (1), said solenoid valves (4a) being kept in position by the protruding portion of said rear cover (1b) against a brake fluid pressure. A brake fluid pressure control unit as claimed in any of claims 2-3, characterized in that said rear cover (1b) of said motor (1) has a housing (10) in which is mounted an electronic control unit (9) having a microcomputer and wherein connectors (4f; 1f) from said solenoid valves (4a) and said motor (1) are guided into said housing and electrically connected to a control circuit on said electronic control unit (9).

Inventors: KOHNO TERUHISA, KOHNO, TERUHISA, KOHNO, TERUHISA, C/O ITAMI WORKS OF SUMITOMO
Applicants: SUMITOMO ELECTRIC INDUSTRIES, SUMITOMO ELECTRIC INDUSTRIES, LIMITED
Application year: 1993
Main classification: B60T8
IPC codes: B60T8