TECHNICAL FIELD This invention relates to anti-lock brake systems for rotating members, such as the wheels of an automotive vehicle, and in one embodiment to an improvement in the modulator of such systems.

BACKGROUND Anti-lock brake systems are well-known, see for example those described in U.S. Patents 3,989,125,

3,833,097, A,138,165 and ,152,030, incorporated herein by reference. The system described in U.S. Patent 4,068,904 employs a modulator interposed in a conduit between a reservoir and a brake cylinder means for normally accomodating free flow of fluid therebetween and also having means, responsive to a sensor detecting a certain rate of retardation of a wheel, for pumping fluid from the brake cylinder back toward the reservoir for releasing the braking force. U. S. Patent ^' 4,138,165 describes a pumping anti-lock device including means for controlling the rate of rise of brake fluid pressure.

It is an object of the present invention to provide an improved anti-lock brake system.

It is a further object to provide such a brake system having a modulator with the three separate states of:(l) pressure reduction, (2) pressure hold, and (3) pressure reapplication.

It is another object to provide a modulator with a solenoid controlled isolation valve to isolate the pumping means from the brake fluid passageway through the modulator.

SUBSTITUTE SHEET

It is another object of the invention to isolate the volumetric expansion and contraction motion of a piston from the main check valves.

It is a further object to allow the pumping motor to run continuously after the first cycle and to greatly increase the efficiency and perforcance of an anti-lock system, and in a multi-channel configuration (see Figs. 3. 4A and 43 of U.S. Patent 4,068,904) to allow each channel to be controlled completely independently of the others. It is another object of the invention to provide a compact, fast, efficient modulator having a single motor operating a plurality of pistons.

It is a further object to provide a modulator with reapplication control means and pressure hold means that are operative without having to shut off the modulator motor.

It is a further object to provide a modulator with a single motor that allows the pressure to be reduced at one wheel while reapplying or holding pressure to another wheel, without the one act disturbing the other. BRIEF SUMMARY OF THE INVENTION

In a modulator of the type described in U.S. Patent 4,068,9-04 having means for pumping brake fluid back from a wheel brake cylinder to a master cylinder reservoir upon a particular rate of retardation of a wheel - being sensed, the improvement including means for con- trollably isolating a pumping chamber from the brake fluid passageway through the modulator. In a preferred embodi¬ ment, the isolating means is a solenoid controlled valve which is opened during pumping periods and closed during non-pumping periods .

In addition, a modulator havins three seυarate states during an anti-lock cycle, namely: (1) a pressure reduction state, (2) a pressure hold state, and (3) a pressure reapplication state. It is noted that the pump motor of the modulator can run continuously not only during the pumping state (1), but also during

SUBSTITUTE SHEET _^

states (2) and (3), that is. during pressure holding and pressure reapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully under- stood by reference to the following detailed description thereof, when read in conjunction with the attached drawings, wherein like reference numerals refer to like elements and wherein;

Fig. 1 is a diagrammatic view of the modulator of this invention as installed in an automobile;

Figs. 2, 3 and 4 are.front, top and rear views, respectively, of a modulator according to a preferred embodiment of this invention;

Fig. 5 is a partly cross-sectional, partly diagrammatic view of the modulator of Figs . 2-4 taken along line 5-5 of Fig. 3;

Fig. 6 is a partly cross-sectional, partly diagrammatic view of the modulator of Figs. 2-4 taken along line 6-6 of Fig. 3; Fig. 7 is a partly cross-sectional, partly diagrammatic view of the modulator of Figs. 2-4 taken along line 7-7 of Fig. 2;

Fig. 8 is a partly cross-sectional, partly diagrammatic view of the modulator of Figs . 2-4 taken . along line 8-8 of Fig. 2;

Fig. 9 is an enlarged cross-sectional view showing t e details of a portion of Fig. 7 and taken along line 9-9 of Fig. 2;

Fig. 10 is an enlarged cross-sectional view showing the details of a portion of Fig. 8;

Fig. 11 is a partly cross-sectional partly diagrammatic view of a portion of Fig. 2 taken along line 11-11 thereof; and

Fig. 12 is an enlarged, cross-sectional view identical to Fig. 9 except that certain parts are shown after movement to a different nosition.

SUBSTITUTE SHEET

DETAILED DESCRIPTION OF THE INVENTION

With reference now to the drawings, Fig. 1 shows a modulator 10 in accordance with the present invention for use in an automobile. The automobile has four wheels 12, 13, 14 and 15. each having a brake 16, 17, 18 and 19 respectively. The automobile also has a logic system 20 for detecting the rate of retardation of rotation of each of the wheels and for signalling impending wheel lock. The logic system 20 includes a sensor 22, 23. 24 and 25 .at each of the wheels 12, 13, 14 and 15, respectively, a control module 26 connected to the modulator 10 and to an automobile battery 28, and a warning indicator 30 which "lights" when the logic system 20 signals the occurrence of a system malfunction.

Any known sensor system can be used, such as one using a magnetic pickup or sensor at each wheel which feeds velocity information to a microcomputer which makes decisions about the impending lock and when the rate of retardation of rotation of a particular wheel reaches a certain value, it generates ^* a signal which then causes the modulator to be energized, for example, to reduce fluid pressure in that wheel. Such logic ^' systems are well-known in the art and therefore are not described here. The modulator 10 is connected to a master brake cylinder reservoir 32 by two hydraulic fluid conduits 34 and 36 and is connected to the four brakes 16-19 by four separate conduits 38, 39, 40 and 41 respectively.

The modulator 10 will .now be described in detail with reference to Figs; 2-12. Referring first to Figs. 2-4 showing the outside of the modulator, Fig. 2 is a front view, Fig. 3 is a top view, and Fig. 4 is a rear view of the modulator 10. The modulator 10 includes a modulator body 50 (Fig. 2) having a front plate 52 attached thereto by screws 54 and a rear plate 56 attached thereto by screws 58. The modulator also includes four through-bolts 60, see Figs. 4, 5, 6 and 11.

SUBSTITUTE SHEET

Referring now to Figs. 5-12, the modulator 10 includes four equally spaced-apart. identical, solenoid controlled re-application valves 62. 64, 66 and 68 in the front of the modulator (Figs. 5 and 7), and four equally spaced-apart, identical, solenoid controlled pressure reduction control valves 70, 72, 74 and 76 in the rear of the modulator (Figs. 6, 7 and 8). The modulator also includes four (only three are shown) identical pistons 78, 80 and 82 (Figs. 8 and 10) mounted for reciprocating movement and driven by a motor 86 and a cam 88 (Fig. 8).

The front plate 52 includes a pair of inlet ports 90 and 92 (Figs. 2, 3, 7 and 9) and the rear plate 56 includes four outlet ports 94, 96, 98 and 100 (Figs. 4. 7 and 8). There are four substantially identical, independent, fluid paths through the modulator 10, one for each of the wheels 12-15. Each path goes through one reapplication-valve and one pressure reduction valve and is associated with one piston..

A description of one path will suffice because all four are substantially identical. For purposes of this description, the path going through the reapplication valve 68, the pressure reduction valve 74 and associated with the piston 82 will be described in detail. Referring mainly to Fig. 7, this path includes (and starts with) fluid inlet port 92, a passageway 102 from port 92 to the reapplication valve -68, from reapplication 68 through passageway 104 to the pressure reduction valve 74 and from, pressure reduction valve 74 to the outlet port 96. Associated with this path is an expansible-contractible chamber 106 (see Fig. 10) which includes a passageway 108 and a cylinder 110 in which the piston 82 reciprocates. Fluid communication between the chamber 106 and the pressure reduction valve 74 is controlled by an isolation valve 112. Regarding path 104 shown in Fig. 6, it is noted that a bore is drilled through the modulator body 50 and the excess length of it is blocked by a steel ball 51 press-fitted into the bore.

SUBSTITUTE SHEET

An overview of the operation of this path will now be described. The pressure reduction valve 74 (Fig. 10) includes a one-way valve 114 (as well as the isolation valve 112) and the reapplication valve 68 5 includes a one-way valve 116 (Fig. 9). Both of the solenoid controlled valves 68 and 74 have two positions, that is, an unenergized position in which the respective one-way valve is held open and an energized position in which it is not held open but is allowed to 10 open and close as controlled by the fluid pressure .on each side of the one-way valve. Thus, the two one-way valves have two positions including a normally open position and a one¬ way operating position. The isolation valve 112 is closed when the pressure reduction valve 74 is unenergized and is open when the valve 74 is energized. In addition, it is noted that each of the one-way valves 114 and 116 15 (when not held open) block fluid flow in the braking direction (from the master cylinder reservoir 32 to the brakes 16-19) , and allow fluid flow in the opposite, or pressure release direction.

Thus, it will be seen that in the normal unener- 20 gized condition of the modulator 10, there is an open passageway through the modulator allowing free flow of fluid therethrough and that the reciprocating operation of the piston 82 has no affect on this passageway. However, when the solenoids of the valves 68 and 74 are energized. 25 the passageway through the modulator 10 is now defined between two one-wav valves and has an expansible and contractible volume, whereby fluid is. pumped from a wheel brake back to the master cylinder. After the pressure in the brake has been reduced, the valves 74 and 68 can 30. be de-energized returning the modulator to its normal off condition allowing free flow of fluid therethrough. There are other states or conditions the modulator can have, which will be described below.

The piston 82 reciprocates during pumping, i.e. 35 when the isolation valve 112 is opened. When the isolation valve is closed, the upward movement of the piston can force fluid out of the chamber 106 past the isolation valve, how-

SUB _S TITUTE SHEET

ever, since no fluid can get into the chamber 106 past the closed isolation valve, there is no force to push the piston down as the cam rotates and the piston will remain up (away from the cam) until the next time the isolation valve is opened.

The individual reapplication valve 68 and the pressure reduc _t ion valve 74 will now be described in detail with reference to the enlarged views thereof in Figs. 9 and 10, respectively. The reapplication valve 68 will now be described with reference to Figs. 9 and 12 which actually show the reapplication valve 64, however, they, are identical so a description of one is a description of the other. Fig. 9 shows the valve 64 in its open or unenergized state, Fig. 12 shows the valve 64 in its unenergized ^' but partly open state (following the pressure reduction cycle described below) . The reapplication valve 64 includes a solenoid coil 120 and a fluted armature plunger 122 which moves to the left in Fig. 9 against the action of a return spring 124 when the solenoid coil 120 is energized. The reappli¬ cation valve 64 also includes a washer or valve disc member 128, a cooperating seat 130, a pin or seal element 132 and its biasing spring 134 fitting inside of a tubular member 136. The tubular member 136 is located in a bore 140 in a disc 142. The member 136 includes openings therethrough to accommodate fluid flow around the seal element 132. When the reapplication valve 64 is in its normal unenergized state, it allows free flow of fluid through the reapplica¬ tion valve 64 through the tubular member 136, around the seal element 132, around and through the valve disc member 12S (through openings 143 in the edge thereof and through a central opening therein, that is, through an annular space 145 (Fig. 12) between the seal element 132 and the central opening in member 128) , through flutes 144 in the plunger 122, out through a passage 146 and into a passageway (not shown but corresponding to passageway 104 in Fig. 7).

SUBSTITUTE SHEET

The reapplication valve 64 also includes means for controlling the rate of rise of increasing fluid pressure applied through the modulator, similar to that described in U.S. Patent 4,138,165 (incorporated herein by reference). That is, the sealing element 132 and associated spring operate similar to that described in that patent. Thus, when the solenoid coil 120 is de-energized, the spring 124 can move the plunger 122 to the right holding the one-way valve 116 open. However, if the pressure differential is sufficiently high, the force of the return spring 124 is incapable of overcoming the pressure forces and the plunger 122 will only move part-way, far enough to unseat the sealing element 132 but not the valve disc member 128. With only the sealing element 132 unseated, a restricted flow path through the reapplication valve 64 is opened, thus controlling the rate of rise of increasing fluid pressure applied through the modulator, until such time as the pressure dif erential diminishes allowing full movement of the plunger 122 which will also unseat valve disc member 128 and allow full flow of fluid through the reapplication valve 64.

The pressure reduction valve 74 will now be described in detail with reference to Fig. 10. The valve 74 includes a solenoid coil 150 and a fluted armature plunger 152 which moves to the left in Fig. 10 against the action of a return spring 154 when the solenoid coil 150 is energized in Fig. 10. The plunger 152 is hollow and includes a pin 156 press-fitted therein. The isolation valve 112 is a ball 157 press-fitted in the hollow plunger and adapted to seal against a seat 158 when the valve 74 is unenergized, thus sealing the chamber 106 from the passageway between the two one-way valves 114 and 116. The one-way valve 114 includes a ball 160, a seat 161 and a spring 162. The ball 160 is not press-fitted in the hollow plunger 152 but is slidably movable therein. When the plunger 152 is in its energized position (to the left in Fig. 10) the ball 160 can move against the spring 162

SUBSTITUTE SHEET

to open and close depending on the fluid pressure across the ^• ball. When the plunger 152 is in its unenergized position (to the right in Fig. 10) the ball is held off of its seat 161 and the one-way valve 114 is held open. It will thus be seen that, with respect, for example, to wheel 13, the modulator 10 (see Fig. 1) is inter¬ posed in a single brake fluid conduit between the reservoir 32 and the brake 17 and in the normal operation of the vehicle has a passageway therethrough that allows the free flow of brake fluid therethrough. However, when the logic system 20 senses- an impending wheel lock, the modulator 10 is caused to go into its pressure reduction state or condition by the logic system 20 energizing the solenoid valves 68 and 74, thus positioning the valves 114 and 116 for one-way valve operation and opening the isolation valve 112. This causes brake fluid to be pumped from the brake 17 back to the reservoir 32. When the logic system senses that wheel lock is no longer imminent, the modulator 10 is caused to go from its pressure reduction state to its pressure hold state by the logic system- de-energizing only the solenoid in the valve 74, thus again isolating the expandible-contractible chamber 106 from the passageway between the one-way valves 114 and 116, while leaving valve 114 open and valve 116 closed. This prevents further pressure increase because valve 116 is closed and prevents further pressure decrease because valve 112 is closed. "At the appropriate time, the logic system then causes the modulator to go from its pressure hold state to its pressure reapplication state by the logic system now de-energizing the solenoid in valve 68, whereby the modulator is returned to its original condition, with the exception that depending upon the pressure differential as discussed above, the valve 68 may not open all the way, thus controll¬ ing the rate of rise of pressure reapplication.

The sequence of modulation state- pressure reduc- tion, pressure hold and pressure reapplication are not limited to the order described above; other sequences may be required by the logic system and followed by the modulator, e.g., pressure hold, pressure reduce and pressure reapply.

SUBSTITUTE SHEET

Thus, this invention provides a single, compact modulator having only a single motor, for use, for example, in automobiles, and which can operate the various brake con¬ duits independently of each other. For example, the fluid pressure can be reduced at one wheel while it is being re- applied at another wheel, with the single motor running all the time, and without the one action disturbing the other.

The above detailed description is only of the presently preferred embodiment of this invention. Other embodiments can.be used. For example, it may be desired to have only three outlets from the modulator with a single fluid conduit to the rear wheels and separate conduits to each of the front wheels. Further, if desired a plurality of individual modulators can be used, each with a single pair of solenoid controlled one-way valves and a single isolation valve and a single piston. The isolation valve can be separate from the two one-way valves and can have its own solenoid control. The means for controlling the rate of rise of re-applying fluid pressure can be omitted if desired. The following terms are hereby defined for use in the specification and claims: the term "normal or non anti- lock brake operation" means the periods of tine during which the anti-lock modulator 10 is not being used, that is, during non-braking operation as well as braking operation that does not use the anti-lock modulator; the one-way valves in the reapplication valves 62-68 will be referred to as the "upstream" valve and the other one-way valves in the pressure reduction valves 70-76 as the "downstream" valves; and the direction of brake fluid flow from the reservoir 32 to the brakes 16-19 is termed the "braking direction" and the opposite direction is termed the "pressure release direction'. ¹

The invention has been described in detail with particular reference to the preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

SUBSTITUTE SHEET