MXPA00001782A - Abs modulator solenoid with a pressure balancing piston - Google Patents

Abstract

An ABS modulator solenoid valve (10), having one electric solenoid (12), in which the valve control piston (14) has a passage (16) therethrough for balancing the pneumatic pressure on both ends (34, 36) of the control piston (14). One end (34) of the piston (14) is disposed in a closed piston chamber (32) while the other end (36) is positioned to contact and position a valve spool (40). The passage (16) extends between the ends (34, 36) of the piston (14). Piston (14) is biased by a spring (50) to a position within the piston chamber (32). When the solenoid (12) is de-energized, the piston (14) remains in this position and variable air pressure, from an operator controlled brake valve (126), can be supplied through the valve (10) to a brake chamber (128) for operating the vehicle service brakes. During an ABS application, the solenoid (12) is energized to overcome the inlet spring (50) bias and the piston (14) moves into engagement with the valve spool (40). The spool (40) is biased by an exhaust spring (52) to a position wherein the exhaust port (24) is isolated from the supply port (20) and the delivery port (22). When the solenoid (12) is fully energized, the piston (14) engages the spool (40) and moves it to the exhaust position. When the solenoid is energized with a selected hold current, the piston (14) engages but does not move the spool (40) and the valve (10) is then in a hold position. Since the pressure on the ends (34, 36) of the piston (14) is balanced, the force required to move the piston (14) to the hold position is relatively constant and not greatly effected by the pneumatic pressure at the supply port (20) or the delivery port (22).

Description

SOLENOID ABS MODULATOR WITH PISTON PRESSURE COMPENSATOR BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates to a pneumatic ABS system and, more specifically, to a single ABS modulating solenoid valve, with a pressure compensating piston, which includes the accumulation, holding functions and escape. 2. DESCRIPTION OF THE PRIOR ART In air brake systems for heavy vehicles, a brake valve controlled by the vehicle operator supplies compressed air at a pressure of 10 psi to 120 psi to operate the vehicle's service brakes. During braking, air is supplied through the brake valve to the brake chambers to operate the service brakes. The air pressure supplied to the service brakes is a function of the position of the brake valve that is controlled by the vehicle operator. The normal practice in ABS tire industry is to use a modulator between the brake valve and the brake chambers to control the air supplied to the brake chambers. Typically, the modulator has two separate control circuits using solenoids, one to accumulate pressure in the brake chambers and one to evacuate the pressurized air from the brake chambers. The retention function is also achieved with these two circuits. During the holding function the modulator retains or regulates the air pressure in the brake chambers at a pressure between 0 psi and the pressure supplied by the brake valve. The pressure supplied by the brake valve can vary from 10 psi to 120 psi. Examples of the ABS modulators of the prior art are the modulators of the anti-lock system AlliedSignal M-21 and M-22. These modulators are practically high capacity on / off air valves that incorporate a pair of electric solenoids for control. The solenoids provide the electro-pneumatic interface or link between the anti-lock controller electronics and the air brake system. The modulator includes a normally open exhaust solenoid and a normally closed supply solenoid, an intake diaphragm valve and an exhaust diaphragm valve. During normal non-anti-lock operation both solenoids are de-energized. The application of the brake introduces air to the supply inlet and flows through the open exhaust solenoid towards the exhaust diaphragm, which with a spring keeps the outlet port closed. At the same time, the application air flows into the supply diaphragm, forcing it away from its seat and allowing the air to flow to the outlet port to the service brake chambers. When the feed solenoid is energized, air flows through it by closing the intake diaphragm to prevent communication between the intake or supply inlet and the outlet or exhaust port. When the exhaust solenoid is energized, the airflow opens the exhaust diaphragm allowing free communication between the exhaust port and the outlet port for rapid escape of compressed air into the brake chamber. If a service brake application is made and the anti-lock system detects an impending wheel lock, the anti-lock controller will immediately begin modifying the brake application using the modulator. To modify the application of the brake, the coils of the two solenoid valves contained in the modulator are energized or de-energized in a preprogrammed sequence by the anti-lock controller. The solenoids in the modulator are controlled independently by the anti-bias controller. When a solenoid is energized, it opens or closes, thereby causing the escape or reapplication of the air pressure to the brake actuator.

In EBS systems it is known to use a proportional modulating valve with a single solenoid for the supply of compressed air at different pressures to the brake chambers of the vehicle »Compressed air at a set pressure, typically 120 psi, is supplied to the valve inlet port and the valve outlet port pressure is controlled to vary directly with the current applied to the solenoid coil which controls the proportional modulating valve. U.S. Patent No. 5,154,203 and German Patent DE 3,111,716 Al disclose such proportional modulating valves.

SUMMARY OF THE INVENTION The present invention is for an ABS solenoid valve having a solenoid in which the control piston of the valve has a passage therethrough to compensate for the pneumatic pressure at both ends of the control piston. This allows the ABS solenoid modulating valve to be held in the detent position when selected, relatively constant current is used to energize the solenoid coil. The selected current valve can be constant or vary over a small interval. In the valve of the ABS modulating solenoid an electric solenoid is connected to move and move with the valve piston. One end of the piston is located in a piston chamber while the other end is located to make contact and place a valve spool. The passage extends from the end of the piston, next to the spool, through the piston to the end of the piston located in the piston chamber to compensate for the pressure at both ends thereof. The piston is pushed by spring to a position inside the piston chamber. When the solenoid is de-energized, the piston remains in position and the air pressure of the service brakes can be supplied through the valve by operating the vehicle's service brakes. The brake air pressure of the brake valve varies from 10 psi to 120 psi. During an ABS application the solenoid is energized to overcome the thrust of the piston spring and the piston moves outward and inward in engagement with the valve spool. The reel is pushed by an exhaust spring to a position where the exhaust port is isolated from the supply inlets and the outlet port. When the solenoid is fully energized the piston engages with the spool and moves it to the exhaust position where the air pressure in the brake chambers is vented to the atmosphere through the solenoid valve. When the solenoid is energized with a selected holding current, the piston moves out of clutch but does not move the spool and the valve is then in a detent position where the pressure in the brake chambers is maintained at a lower pressure than the pressure of the service brakes supplied to the valve inlet. The retention current selected to energize the solenoid coil can be relatively constant or vary slightly within a small interval because the pressure at both ends of the piston is compensated. Since the pressure at the ends of the piston is compensated, the force required to move the piston to the detent position is relatively constant and is not greatly affected by the pneumatic pressure of the supply port or the outlet port.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention reference may be made to exemplary preferred embodiments of the inventions shown in the accompanying drawings, in which: FIGURE 1 is an illustration of an ABS modulating solenoid with a piston pressure compensator according to the present invention; FIGURE 2 is an illustration of an ABS modulator as shown in FIGURE 1 in the pressure accumulation position; FIGURE 3 is an illustration of an ABS modulator as shown in FIGURE 1 the pressure retention position; FIGURE 4 is an illustration of an ABS modulator as shown in FIGURE 1 in the exhaust position; FIGURE 5 shows an ABS modulator valve with two solenoids of the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now with reference to the drawings and FIGURE 1 in particular, an improved ABS modulating solenoid valve 10 is shown, having a solenoid 12, in which a control piston of the valve 14 has a step 16 through it to offset the pressure pneumatic on both ends of the control piston 16. The modulating solenoid valve 10 can replace the modulating valves 110 of the prior art as shown in FIGURE 5 and will be described later. Compensating the pressure at the ends of the piston 14 allows a relatively constant force to be necessary to maintain the piston in the detent position. Now in relation to FIGURE 5 an ABS modulator unit of the prior art 110 is shown. The modulating valve 110 is essentially on / off air valves, high capacity that incorporate a pair of electric solenoids 112, 113 for control. The solenoids 112, 113 provide electro-pneumatic interface or link between the electronics of the anti-lock controller and the air brake system. The modulator 110 includes a normally open exhaust solenoid 113 and a normally closed supply solenoid 112, an intake diaphragm valve and an exhaust diaphragm valve. During non-anti-lock operation, both solenoids 112, 113 are de-energized. The air from the application of the brake, from a brake valve 126, enters the supply port or intake port 120 and flows through the open exhaust solenoid 113 towards the exhaust diaphragm 114 which with a spring 115 holds the exhaust port 124, At the same time, the application air flows to the supply diaphragm 116, forcing it away from its seat and allowing air to flow out of the outlet port or exhaust port 122 to the brake chambers service 128. When the supply solenoid 112 is energized, the pressurized air flows through it by closing the supply diaphragm 116 to prevent communication between the intake or supply port 120 and the exhaust or exit port 122. When the solenoid Exhaust 113 is energized, the air flow opens the exhaust diaphragm 114 allowing free communication between the exhaust port 124 and the exit port 122 for the rapid escape of the air compressed In the braking chamber 128. If an application of the service brakes is made and the anti-lock system detects an imminent wheel lock, the anti-lock controller will immediately start the modification of the brake application using the modulator 110. To modify the application of the brake, the coils of the two solenoid valves 112, 113 contained in the modulator 110 are energized or de-energized in a sequence pre-programmed by the anti-blocking controller. The solenoids 112, 113 in the modulator 110 are independently controlled by the anti-lock controller. When a solenoid 112 or 113 is energized it opens or closes causing or closing thereby causing the exhaust or reapplication of the air pressure to the brake chamber actuator 128.

Referring now to FIGS. 1 to 4, the modulating valve 10 of FIGURE 1 is shown in the accumulation position in FIGURE 2, in the retention position in FIG.

FIGURE 3 and in the exhaust position in FIGURE 4. In the described ABS modulating solenoid valve 10 an electric solenoid actuator 18 is connected to the valve piston 14. The actuator 18 moves in response to the applied electric current to the coil 30 of the solenoid in a manner well known in the art. The actuator 18 and the piston 14 move together as a unitary part.

One end 34 of the piston 14 is located in a piston chamber 32 while the other end 36 is positioned to contact and position a valve spool 40. One step extends from the end 36 of the piston 14, next to the spool 40, through the piston 14 to the end 34 located in the chamber of the piston 32 to compensate the pressure at both ends 34, 36 of the piston 14. A suitable gasket, such as a piston ring 35 is located around the piston 14 in coupling with the walls of the piston chamber 32 to isolate the closed end of the piston chamber 32 from the outlet port 22. The piston 14 is spring-loaded to a position, as shown in FIGURE 2, within the chamber of the piston. piston 32 by an inlet spring 50. When the solenoid 12 is deenergized the piston 14 remains in this position and the air pressure of the service brakes can be supplied through the solenoid valve 10. to operate the vehicle service brakes. The service brake air pressure of the brake valve 126 varies from 10 psi to 120 psi. When the vehicle operator presses a brake pedal 127, the brake valve 126 begins to supply air to the brake chambers 128 through the valve 10. The pneumatic pressure in the brake chambers 128 rapidly accumulates the pressure supplied from the brake. brake valve 126. When the brake pedal 127 is released and the ABS is not activated, the pressure supplied from the brake valve 126 drops below 10 psi and the pressure in the brake chambers 128 also drops. During the ABS application, the coil of the solenoid 30 is energized with sufficient current to overcome the thrust on the piston 14 of the spring 59, and the piston 14 moves in engagement with the spool of the valve 40. The spool 40 is pushed by a exhaust spring 52 to a position as shown in FIGS. 1 to 3, wherein the exhaust port 24 is insulated from the supply port 20 and the outlet port 22. The spool 40 is supported for longitudinal movement within an orifice formed in the housing 54. A suitable gasket, such as a toroidal seal 56 fits around the spool 40 and isolates the supply port 20 from the exhaust port 24. One end of the spool 40 engages a valve seat formed in the housing 54 for isolating the outlet port 22 from the exhaust port 24. When the coil 30 of the solenoid 12 is fully energized, the piston 14 engages the spool 14 and moves it to the exhaust position, as shown in FIG. FIG. 4, wherein the air pressure in the brake chambers 128 is vented to the atmosphere through the valve of the solenoid 10. To move to this position the force supplied by the solenoid driver 18 must overcome the force of the intake spring 50, the exhaust spring 52 and the friction associated with the different components. When in the position shown in FIGURE 4, the end 36 of the piston 14 is in sealing engagement with the end of the spool 40 to prevent the supply port 20 from communicating with the outlet port 22 or the exhaust port 24. brake chamber 128 is in free communication with the atmosphere through the outlet port 22 and the exhaust port 24. Any pressure within the brake chamber 128 is quickly evacuated. The supply port 20, in this position, still communicates with the chamber of the piston 32, through the passage 16, to compensate for the pneumatic forces at both ends of the piston 14. If during operation, ABS is desired not to accumulate or evacuate the pressure to the chambers of brakes 128, but to maintain the pressure inside the brake chamber 128, the coil 30 of the solenoid 12 is energized with a selected holding current which through the actuator 18 causes the piston 14 to clutch but not move the spool 40. away from the coupling with the valve seat formed in the housing 54. The solenoid valve 10 is then in a detent position where the pressure in the brake chambers is maintained at the desired pressure which can be between 0 psi and the pressure of the service brakes supplied to the valve intake 20. If an application of the service brake is made and the anti-lock system detects a blockage of the impending wheel, the The anti-lock controller will immediately begin modification of the brake application using the modulating valve 10. To modify the brake application, the coil 30 of the solenoid 12 is de-energized or energized to the retention or exhaust positions in a preprogrammed sequence by the anti-lock controller. In a common ABS situation, when a wheel lock is going to occur, the coil 30 is energized to fully extend the piston 14 and move the modulating valve 10 to the exhaust position, as shown in FIGURE 4. The pressure in the brake chamber 128 then it drops to approximately 0 psi. The modulating valve 10 is then modulated between the accumulated pressure position, as shown in FIGURE 2, and the retention pressure position, as shown in FIGURE 3, to raise the pressure in the brake chamber 128 in steps up to the desired level. Depending on the conditions of the road surface, the wheel lock can occur at different air pressures of the service brakes which are applied to the inlet port 20 and the brake chambers 128. The air pressure of the brakes Brake valve service 126 varies from 10 psi to 120 psi depending on the use of pedal 127 by vehicle operators. During an impending wheel lock situation, the ABS controller will control the modulating valve 10 to modulate the pressure in the brake chamber 128 at a pressure less than the pressure of the brake valve 126 supplied to the intake port 20. The flow of The selected retention for energizing the solenoid coil 30 can be relatively constant or vary slightly within a small range because the pressure at both ends 34, 36 of the piston 14 is compensated. The outer areas of the piston 14 are dimensioned so that, when the pressures at the end 34, 36 of the piston 14 are equal to the pressures of the brake chambers 128 acting on the piston 14 are canceled and there is no net force pending to move the piston 14 in any direction. Since the pressure at the ends 34, 36 of the piston 14 are compensated, the force necessary to move the piston to the detent position is relatively constant and is not carried out to a large extent by the pneumatic pressure at the supply port 20 or the outlet port 22. Excluding friction, the force required to maintain the solenoid valve 10 in the detent position must be greater than the thrust of the intake spring 50 but less than the combined thrust of the intake spring 50 and the spring of escape 52.

Claims (8)

1. An ABS modulating valve comprising: a housing having an intake port, an outlet port and an exhaust port; a reel located inside the housing and being pushed by the spring to a first position isolating the exhaust port of the intake port and the outlet port; a piston having one end located inside the sealed piston chamber and having the other end located to engage and move the spool to a second position isolating the intake port, the outlet port and the exhaust port or a third isolated position on the port of admission of the port of exit and the port of escape; an electrical solenoid attached to the housing having a connection to the piston for moving the piston when the electric solenoid is energized with a first current selected to the second position and, or with a second current selected to the third position; and a passage formed through the piston allowing free communication between the intake port and the sealed piston chamber to compensate for pressures at the ends of the piston. An ABS modulating valve as recited in claim 1 comprising: a hole through the spool through which the intake port can communicate with the outlet port and the passage to the sealed piston chamber; and the sealing means for sealing the hole through the spool of the communication with the outlet port when the piston engages the spool. 3. An ABS electrically operated solenoid modulating valve having an intake port, an outlet port and an exhaust port and being operable in a first mode where the intake port is in free communication with the port of departure and the port of escape is isolated, a second mode where the intake port, the exit port and the exhaust port are all isolated, and a third way where the exit port is in free communication with the escape port and the port of admission is isolated, the modulating valve comprises: a reel having a central passage communicating with the intake port and being spring-loaded into a position to isolate the exhaust port from the intake port and the outlet port; a piston having one end located in a sealed piston chamber, having one end closed, and the other end positioned to engage the spool when the piston moves away from the closed end of the sealed piston chamber; an intake spring pushing the movable piston toward the closed end of the piston chamber; an electric solenoid having an actuator connected to move the piston when the electric solenoid is energized to cause operation in the second mode or the third mode; and a passage extending through the piston allowing free communication from the intake port, through the central passage of the spool to the sealed piston chamber to allow to compensate the pneumatic pressure acting on the ends of the piston so that the necessary force of the electric solenoid to operate in the second mode is relatively constant even as the supply pressure applied to the intake port varies. 4. An ABS system for heavy vehicles where the air pressure, which can vary between approximately 10 psi and 120 psi in response to the braking demands of the vehicle operator, is supplied through an electrically controlled solenoid modulating valve, having a supply port, an outlet port and an exhaust port, to the braking chambers for the brakes of the heavy vehicle, the modulating valve comprises: a reel that can be moved between a first insulating position of the port of escape of the port of supply and the port of departure and a second position; a piston that can be moved from a first position where there is free communication between the supply port and the exit port to a second position, by engaging the reel, where the supply port, the outlet port and the exhaust port are isolated or to a third position, moving the reel to its second position, where the exit port is in free communication with the escape port; and an electric solenoid having an actuator connected to move the piston when energized to its second position or its third position. The ABS system as recited in claim 4, wherein the piston is partially located in a piston chamber and a passage is formed through the piston to compensate for the pressure within the piston chamber with the pressure in the other piston end. 6. An ABS modulating valve comprising: a housing having an intake port, an outlet port and an exhaust port; a reel located inside the housing and being spring-loaded to a first position isolating the exhaust port of the intake port and the outlet port; a piston having one end located for the reel clutch isolating the exhaust port, the inlet port and the outlet port and moving the reel to a position isolating the inlet port of the outlet port and the exhaust port; an electrical solenoid attached to the housing having a connection to the piston to move the piston when energized with a first current to engage the spool and when energized with a second current to move the spool 7. The ABS system As mentioned in claim 6 , where: the piston is partially located in a sealed piston chamber; and a passage is formed through the piston to compensate for the pressure at the end of the piston inside the sealed piston chamber with the pressure at the other end of the piston. 8. An ABS modulating valve located in a heavy vehicle between the vehicle's brake valve and a vehicle's brake chamber to modulate the variable air inlet of the brake valve when the ABS is operated, consists of in: an elongate housing with an electric solenoid actuator located at one end of the housing and a supply port located at the other end; an exit port and an escape port formed on the side of the housing; the movable valve means located within the housing and being movable to a first position where there is free communication between the supply port and the outlet port, to a second position where the supply port, the outlet port and the exhaust port are located. isolated, and a third position where the exit port is in free communication with the escape port; and an electrical solenoid connected to operate with the moving valve means for positioning the moving valve means to the first position, the second position and the third position in response to the inputs of the ABS controller. SUMMARY OF THE INVENTION An ABS modulating solenoid valve (10) having an electric solenoid (12), in which the valve controls the piston (14) has a passage (16) therethrough to compensate for the pneumatic pressure at both ends (34, 36) of the control piston (14). One end (34) of the piston (14) is located in a closed piston chamber (32) while the other end (36) is located to contact and position a valve spool (40). The passage (16) extends between the ends (34, 36) of the piston (14). The piston (14) is urged by a spring (50) to a position within the piston chamber (32). When the solenoid is de-energized, the piston (14) remains in this position and the variable air pressure, coming from a brake valve controlled by the operator (126) can be supplied through the valve (10) to a chamber of brake (128) to operate the vehicle service brakes. During an ABS application, the solenoid (12) is energized to overcome the thrust of the intake spring (50) and the piston (14) moves in clutch with the valve spool (40). The spool (40) is pushed by an exhaust spring (52) to a position where the exhaust inlet (24) is isolated from the supply or supply inlet (20) and the outlet port (22). When the solenoid (12) is fully energized, the piston (14) engages the spool (40) and moves it to the exhaust position. When the solenoid is energized with a selected holding current, the piston (14) engages but does not move the spool (40) and the valve (10) is then in a detent position. Since the pressure at the ends (34, 36) of the piston (14) is compensated, the force necessary to move the piston (14) to the retention position is relatively constant and is not greatly affected by the pneumatic pressure in the piston (14). the supply input (20) or the output port (22).