WO1995002531A1

WO1995002531A1 - Antilock modulator valve with variable control orifice

Info

Publication number: WO1995002531A1
Application number: PCT/US1994/007364
Authority: WO
Inventors: Kazuyoshi Suzuki; Timothy Jack Frashure; Julie Ann Miller
Original assignee: Alliedsignal Inc.
Priority date: 1993-07-12
Filing date: 1994-06-30
Publication date: 1995-01-26
Also published as: AU7319494A

Abstract

A test for an electronically controlled braking system, such as an adaptive braking system, is made to assure that the solenoids of each of the modulators (52, 54, 66, 68) are properly wired. According to the test, each modulator (52, 54, 66, 68) is tested in sequence. The exhaust solenoid of a modulator (52, 54, 66, 68) is actuated for 10 milliseconds, and the hold solenoid is then actuated for 30 milliseconds. If the modulator (52, 54, 66, 68) has been miswired, the exhaust solenoid will have been actuated for 30 milliseconds, thus generating a much louder 'popping' sound than that generated by the other modulators (52, 54, 66, 68) will be immediately noticed and corrected. Further, there is disclosed an antilock modulator valve with a variable control orifice having a relay valve (12), in which the pressure in the relay valve control chamber (28) is controlled by means of two normally open solenoid inlet valves (46, 94) in parallel, one of them being provided with a flow restricting orifice (60), and a single normally closed solenoid exhaust valve (68). During the anti-lock mode of operation pressure is (re-)applied to the control chamber (28) solely through the inlet valve (46) which is provided with the restriction (60), in order to control the rate of pressure increase. The disclosed antilock modulator valve provides a reduced brake application time during normal braking while affording a reduction in the total number of relay valves on the vehicle.

Description

ANTILOCK MODULATOR VALVE WITH VARIABLE CONTROL ORIFICE

This invention relates to a modulator for an antilock brake system.

Many current antilock modulators for fluid pressure braking systems include a relay valve section which controls communication from a pressure source (such as the vehicle air reservoirs) to the brake actuators. The relay valve section includes a control chamber which is communicated with the operator controlled brake valve during normal braking so that a pressure level is communicated to the brake actuators which is a direct function of the pressure level called for by the operator by operation of the brake valve. Such antilock modulators further include a normally open inlet solenoid valve which controls communication from the brake valve into the control chamber and which is actuated during brake pressure exhaust cycles during the antilock mode of operation of the modulator to close off communication from the brake valve to the control chamber, and which in its normal deenergized state permits communication into the control chamber through a flow restricting orifice. Antilock modulators further include a normally closed exhaust solenoid which controls communication between the control chamber and ambient atmosphere to reduce brake pressure during brake pressure reduction cycles when the modulator is operated in the antilock mode. The flow restricting orifice controls the rate of pressure increase. The blast of control air that would enter the control chamber without the orifice would make antilock brake performance very harsh; that is, a series of full applications followed by full exhaust would occur without any modulation in between. Governmental regulations require during normal braking, that the modulator deliver air to the brake actuators in sufficient quantity to effect a brake application in a predetermined time after the operator operates the brake valve. The aforementioned control orifice, which limits the rate of pressure increase in the modulator during antilock operation, also inherently limits communication of control air into the control chamber during operation in the normal braking mode when the orifice is not necessary. Accordingly, the orifice delays pressure communication inco the control chamber and thus increases the time between the operator applying the brake and the brake actuators effecting a brake application. In most vehicle applications, the time delay caused by the orifice still permits a brake application within the required time limits. However, on vehicles, particularly trailers, with multiple axles and relatively large brake chambers, the control orifice does not allow for pressure to be built up in the brake chambers quickly enough to meet governmental regulations. Accordingly, it has been necessary to use a second modulating relay valve solely to increase response time. Of course, this adds substantial expense to the system.

The present invention maintains optimum antilock brake performance by using a relatively small orifice, but the application time is sufficiently reduced to meet governmental regulations during normal braking while using only a single modulator. A third, normally open solenoid valve during normal braking permits communication through a second flow path parallel to the inlet flow path extending through the orifice. This second flow path communicates through the exhaust solenoid valve and the exhaust valve passage into the control chamber. During the antilock mode of operation, this third solenoid valve is actuated to close off the second path, so that only flow through the orifice is permitted. Accordingly, the time required to communicate control air into the control chamber during normal braking is reduced because a second flow path is available which parallels the flow path through the orifice.

These and other advantages of the present invention will become apparent from the following description, with reference to the accompanying drawings, in which:

Figure l is a side elevational view of an antilock brake modulator made pursuant to the teachings of the present invention; Figure 2 is a view taken substantially along lines 2-2 of Figure 1; and

Figure 3 is a schematic illustration, partly in section, of the arrangements of the solenoids used in the antilock modulator of Figure l.

Referring now to the drawings, an antilock modulator generally indicated by the numeral 10 includes a relay valve section 12, a cover 14 for the relay valve section 12, in which solenoid valves are mounted, and an electronic module 16 which is mounted on top of the cover 14. A bracket 18 is provided to secure the modulator 10 to the vehicle.

Referring now to Figure 2, the relay valve section 12 includes a housing 20 which defines a bore 22 which slidably receives a conventional relay piston 24. The relay piston 24 includes a control surface 26 which cooperates with a cover (not shown in Figure 2) which extends across the top of the housing 20 (viewing Figure 2) to define a control chamber 28 therebetween. Housing 20 further includes an inlet port 30 which is connected to a source of pressure, such as the air reservoir. Housing 20 further includes a delivery port 32 through which pressure is communicated to the aforementioned brake actuators. A conventional combination inlet and exhaust valve generally indicated by the numeral 34 controls communication between the inlet port 30, the outlet or delivery port 32, and an exhaust port 36. The combination inlet and exhaust valve 34 is conventionally operated by operating member 38, which is a part of the relay piston 24. Accordingly, the relay piston 24 responds to an increase in braking pressure in the control chamber 28 to move into engagement with the combination inlet and exhaust valve 34, thereby cutting off communication between delivery port 32 and exhaust port 36, and thereafter opens the inlet and exhaust valve 34 to allow pressure at inlet port 30 to communicate through delivery chamber 40 to the delivery port 32. Accordingly, it will be understood that the relay piston 24 responds UO the pressure level in the control chamber 28 to establish a pressure level at the delivery port 32 which is a function of the pressure level in the control chamber 28. This foregoing described operation of the relay section 12 is conventional.

Referring now to Figure 3, the three valves incorporated within the aforementioned cover 14 are illustrated schematically. These valves control communication to and from the control chamber 28. Control air from the aforementioned operator actuated brake valve is received at the modulating valve 10 at inlet 42 and is communicated through a first flow path 44 to a normally open inlet solenoid valve generally indicated by the numeral 46. The control pressure is received at inlet 48 and is communicated into a bore 50. A stationary pole piece 52 mounted in bore 50 is circumscribed by a coil 54. An armature 56 is also circumscribed by coil 54 and is slidably mounted for movement within the coil 54. A spring 57 yieldably urges the armature 56 away from the pole piece 52. Pole piece 52 defines a passage 58 which terminates in a flow restricting orifice 60. Armature 56 carries a sealing member 62 which is adapted to engage the pole piece 52 to terminate communication through passage 58. In the normally open position of the valve 46, pressure communicates through the passage 58 and orifice 60 and then through an annular passage defined between the outer circumferential surface of the armature 56 and the inner circumferential surface of the coil 54 to delivery passage 64, which communicates with control chamber 28. Pressure is released from control chamber 28 upon brake release through the one-way check valve 66 and delivery passage 64.

During operation of the modulator 10 in the adaptive braking mode, reduction of brake pressure in the control chamber 28 is effected by normally closed exhaust solenoid valve generally indicated by the numeral 68. The exhaust solenoid 68 includes a housing defining a bore 70 therewithin and having exhaust passages 72, 74 which communicate the bore 70 with the control chamber 28. An exhaust port 76 communicates the bore 70 with ambient atmosphere. A pole piece 78 is mounted in the bore 70 and is circumscribed by an actuating coil 80 which also extends around an armature 82 which is coaxial with the pole piece 78. The armature 82 carries a seal 84 at one end thereof which sealing engages the exhaust passage 76. A spring 86 yieldably urges the armature 82 toward the passage 76. Air is exhausted from the control chamber 28 through the exhaust passages 72 and 74. Exhaust passage 72 is communicated to the exhaust passage 76 through a passage 88 which extends through the pole piece 73 and armature 82 and through a radial opening 90 which communicates with a passage defined by the clearance between the outer circumferential surface of the armature 82 and the coil 80. Accordingly, when the coil 80 is actuated, the armature 82 is moved to the right, viewing the Figure, thereby opening the passage 76. Pressure is exhausted from the control chamber through the aforementioned passages to the exhaust passage 76. During the normal braking mode of operation, pressure is communicated from the inlet 42 to the control chamber 28 through a second flow path generally indicated by the numeral 92. The second flow path 92 communicates the inlet 42 through a normally open antilock mode solenoid valve generally indicated by the numeral 94. The valve 94 is identical to the valve 46, except that it does not include the flow restricting orifice 60. Accordingly, the valve 94 will not be disclosed in detail. Valve 94 includes an outlet passage 96 which is communicated to bore 70 of the valve 68 through an inlet fitting 98 which closes the end of the bore 70. It should be noted that in the prior art modulator inlet fitting 98 is replaced by a plug. Accordingly, the only changes necessary from the standard modulator which is used for the majority of braking systems which do not require the increased flow capacity provided by the modulator of the present invention is that the plug is replaced by the fitting 98 and the additional solenoid valve 94 is added, along with the associated piping and wiring to connect the valve 94 to the fitting 98. In operation, during operation of the modulator 10 in the normal braking mode, pressure signals generated by the vehicle operator in operating the aforementioned brake valve (not shown) are communicated through the inlet 42. This pressure simultaneously travels through the first flow pach 44 and also through -he second flow path 92 as will hereinafter be described. It will be noted that, during normal braking, each of he solenoid valves 46, 68 and 94 are and remain deenergized. Accordingly, pressure is communicated through the first flow path 44, through the normally open inlet solenoid valve 46 and the passage 64 into the control chamber 26. It will of course be remembered that flow through this path will be restricted because it must pass through the flow restricting orifice 60. Simultaneously, however, pressure will also be communicated through the solenoid valve 94, and the fitting 98. Since valve 68 is deenergized, the seal 84 remains sealed against the passage 76, thereby preventing fluid from communicating to atmosphere. Fluid communicated through the inlet fitting 98 is communicated into the control chamber 28 through the passage 72 and also through the passage 74, as pressure entering the bore 70 also communicates through the passages 88 and 90 to the passage 74. Accordingly, pressure is communicated into the control chamber 28 through two parallel paths, the first flow path being restricted by the flow restricting orifice 60. However, sufficient air is communicated through the flow path 92 to supplement the pressure communicated through the flow path 44 such that sufficient volume is available to control pressure in the chamber 28 within the time limits imposed by governmental regulations.

As discussed above, during operation of the modulator 10 in the antilock control mode, it is desirable to restrict pressure communication into the control chamber 28 during pressure build cycles. Accordingly, when incipient skidding condition is sensed, all of the valves 46, 68 and 94 are actuated. Actuation of the valve 94 closes off communication through the flow path 92, so that all communication to the control chamber 28 must be through the flow path 44. Accordingly, communication into the chamber 28 during operation in the antilock mode is restricted by the flow restricting orifice 60. When the adaptive antilock control is initiated, normally open valve 46 is actuated to close off communication through the flow path 44, and the valve 68 is actuated to initiate a brake pressure decay cycle by communicating the control chamber 28 with atmosphere, thereby reducing brake pressure. The antilock control system senses that an incipient skidding condition no longer exists and it is desirable to build pressure, valves 68 is deenergized, thereby closing communication between atmosphere in the control chamber 28, and valve 46 is also deenergized, thereby permitting pressure to build in the control chamber 28 by pressure communicated through the flow path 44 in the flow restricting orifice 60. It will be noted that the valve 94 is continuously actuated at all times when the modulator 10 is operated in the antilock mode, even through the valves 46 and 68 are alternatively energized and deenergized. When the modulator goes out of the antilock mode, valve 94 is deenergized, thereby again permitting normal operation in the normal braking load wherein pressure is communicated to chamber 28 through both of the path 44 and 92.

Claims

-LAIMS

1. Method of testing an electronically controlled braking system to assure that exhaust and hold solenoids are properly wired, said electronically controlled braking system having an electronic control unit (70) and at least one modulator (52,54,66,68) controlled by said electronic control unit (70) for controlling the braking pressure of at least one of the wheels of the vehicle, said modulator (52,54,66,68) having a hold solenoid valve (96) for controlling communication between said modulator (52,54,66,68) and a pressure source and an exhaust solenoid valve (80) for controlling communication between said modulator (52,54,66,68) and ambient atmosphere, characterized in that said method comprises the steps of energizing one of the solenoid valves (80,96) for a predetermined time period, and energizing the other solenoid valve of said modulator (52,54,66,68) for a predecided time period significantly different from said predetermined time period after the predetermined time period has expired to permit pressure to exhaust through the exhaust solenoid valves (80) for one of said time periods if the exhaust and hold solenoid valves (80,96) are properly wired and for the other of said time periods if said exhaust and hold solenoid valves (80,96) are improperly wired, whereby the noise generated by pressure exhausting through said exhaust solenoid valve (80) for the other time period is significantly different from the noise generated by pressure exhausting through said exhaust solenoid valve (80) for said one time period, thereby alerting of a miswired solenoid valve condition.

2. Method of testing an electronically controlled braking system as claimed in claim 1, further characterized in that said one time period is substantially longer than said other time period.

3. Method of testing an electronically controlled braking system as claimed in claim 2, further characterized in that the steps of energizing the hold and exhaust solenoids (80,96) for said time periods are repeated serially for each modulator (52,54,66,68) controlling one or more brakes of the vehicle.

4. Method of testing an electronically controlled braking system as claimed in claim 2, further characterized in that said one time period is the predecided time period and the other time period is the predetermined time period.

5. Method of testing an electronically controlled braking system as claimed in claim 3, further characterized in that said method includes the step of waiting a preestablished time period after the solenoid valves (80,96) of each modulator (52,54,66,68) are actuated before actuating the valves of another modulator (52,54,66,68).

6. Method of testing an electronically controlled braking system as claimed in claim 5, further characterized in that said method steps are initiated by starting the vehicle upon which said modulator (52,54,66,68) while effecting a brake application.

7. Method of testing an electronically controlled braking system as claimed in claim 1, further characterized in that said electronically controlled braking system includes testing means (122-136) for checking said solenoid valves (80,96) to determine if any of said solenoids are open or short, said method including the steps of checking all of the solenoid valves for open solenoid or a shorted solenoid condition before actuating said solenoids for the predetermined or predecided time periods.

8. Electronically controlled braking system comprising an electronic control unit (70) and at least one modulator (52,54,66,68) controlled by said electronic control unit (70) for controlling the braking pressure of at least one of the wheels of the vehicle, said modulator (52,54,66,68) having a hold solenoid valve (96) for controlling communication between said modulator (52,54,66,68) and a pressure source and an exhaust solenoid valve (80) for controlling communication between said modulator (52,54,66,68) and ambient atmosphere, characterized in that said electronic control unit (70) includes testing means (122-136) for determining if the solenoid valves (80,96) are improperly wired, said testing means (122-136) including means for energizing one of the solenoid valves (80,96) for a predetermined time period and for energizing the other solenoid valve of said modulator (52,54,66,68) for a predecided time period significantly different from said predetermined time period after said predetermined time period has expired, whereby the noise generated by pressure exhausting through said exhaust solenoid valves (80) for one of said time periods is significantly different from the noise generated by pressure exhausting through said exhaust solenoid valves (80) for the other time period, thereby alerting of a miswired solenoid valve condition.

9. Electronically controlled braking system as claimed in claim 8, further characterized in that said one time period is substantially longer than said other time period.

10. Electronically controlled braking system as claimed in claim 9, further characterized in that said testing means (122-136) includes means for energizing the hold and exhaust solenoids for said time periods are repeated serially for each modulator (52,54,66,68) controlling one or more brakes of the vehicle.

11. Electronically controlled braking system as claimed in claim 10, further characterized in that said testing means (122-136) includes means for starting the vehicle upon which said modulator (52,54,66,68) is mounted, and means for effecting a brake application, said testing means (122-136) including means for initiating actuation of said solenoid valves (80,96) for said predetermined and predecided time periods only after said starting means and brake application effecting means are actuated simultaneously.