Tire pressure regulating device with a pneumatically pilot-controlled relay valve

Abstract

A pressure regulating device is provided for at least one tire of a commercial vehicle, having a relay valve which performs compressed air loading of a working line which leads to the tire starting from a pressure source in accordance with a pneumatic pilot controller which has an electropneumatic converter for converting an electric actuating signal into a corresponding pneumatic pilot control signal for the relay valve. The converter has an electropneumatic aeration valve and an electropneumatic ventilating valve for pneumatic signal specifying for increasing or reducing the tire pressure. The pneumatic signal specifying takes place according to special regulations.

Claims

1. A method of regulating the pressure of at least one tire of a utility vehicle, using a relay valve with which compressed air loading or compressed air venting of a working line extending from a pressure source and leading to the tire is performed in accordance with a pneumatic pilot controller with which an electrical actuation signal is converted into a pneumatic pilot control signal, corresponding to a setpoint tire pressure, for the relay valve, the method comprising the acts of: in an event of a low actual tire pressure and/or a high setpoint tire pressure in an initial phase of an aeration of the tire predefining by an electronic control unit a higher pressure than the setpoint tire pressure in order to accelerate the aeration; and in the event of a high actual tire pressure and/or a low setpoint tire pressure at a start of a venting of the tire, predefining a lowest possible pressure above a switch-off pressure of a wheel valve by the electronic control unit in order to accelerate the venting.

2. The method according to claim 1, wherein an initial increase or decrease with respect to the setpoint tire pressure which is to be set is predefined based on a characteristic curve stored in the electronic control unit or formed therein.

3. The method according to claim 2, wherein the electronic control unit performs signal processing of both the tire pressure measured with a pressure sensor and further measurement signals, originating from an on-board pneumatic system, for determining the pneumatic pilot control signal, and an inflation time of the tire is calculated based on the signal processing in order to carry out aeration of the tire in a calculated time period.

4. The method according to claim 3, wherein the electronic control unit newly calculates an inflation time after modification of the tire pressure and/or of the further measurement signals of the on-board pneumatic system.

5. The method according to claim 4, wherein the electronic control unit prevents or interrupts the aeration if the evaluation of the further measurement signals of the on-board pneumatic system indicates that execution of a higher priority basic function of the on-board pneumatic system from the compressed air requirement of the tire inflation would be jeopardized.

6. The method according to claim 1, wherein the increasing of the aeration or the decreasing of the venting of the tire is stopped by the electronic control unit if the tire pressure measured by a pressure sensor has reached at least 90% of the setpoint tire pressure.

7. The method according to claim 6, wherein the electronic control unit records a pressure profile plotted over time determined by the pressure sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic illustration of a compressed air supply system for a utility vehicle.

(2) FIG. 2 is a block circuit diagram illustration of a tire inflation device for inflating two tires of a utility vehicle.

(3) FIG. 3 is a graphic illustration of a SETPOINT value profile with offset for a rapid pressure compensation.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) According to FIG. 1, a compressed air system of a utility vehicle (not illustrated here in more detail) is composed essentially of compressor 1 for generating compressed air from the ambient air (atmosphere), downstream of which compressor 1 an air dryer 2 for removing the moisture from the compressed air is connected. The compressed air which is dried as a result serves to supply various compressed air consumers 3 and, inter alia, also to supply, via a pressure limiting valve 4, a tire inflation device 5 for inflating at least one tire 6 connected thereto.

(5) According to FIG. 2, the tire inflation device 5 for two tires 6a and 6b which are connected therein is composed essentially of a relay valve 7 which performs compressed air loading of a working line 8 which starts from a supply pressure input 9 and leads to the tire 6a and 6b. The actuation of the pneumatically pilot-controlled relay valve 7 is carried out by an electropneumatic aerating valve 10 and by an electropneumatic venting valve 11. The aerating valve 10 serves to increase the pilot control pressure, which triggers an increase in the tire pressure by the relay valve 7. The venting valve 11 serves to reduce the pilot control pressure, which results in a reduction in the tire pressure. The tire pressure which is present is measured in an analogous fashion by use of a pressure sensor 12 which is arranged on the working line 8 of the relay valve 7. The electrical measurement signal is fed on the input side to an electronic control unit 13. The electronic control unit 13 determines the control error on the basis of the predefined setpoint tire pressure n setpoint and as a result thereof electrically actuates either the aerating valve 10 to generate the tire pressure or the venting valve 11 to reduce the tire pressure. A separate wheel valve 14a or 14b is provided per tire 6a and 6b in order to make a selection of the tire inflation.

(6) The electropneumatic aerating valve 10 and the electropneumatic venting valve 11 are connected in series with one another and are both embodied as a monostable electropneumatic 2/2-way valve. Both valves can be actuated alternately by the control unit 13.

(7) In order to accelerate the aeration, in the case of an excessively low ACT tire pressure at the start of the aeration, the control unit 13 predefines a higher pressure than the setpoint tire pressure p.sub.setpoint. The same occurs analogously in the case of venting, that is to say regulated reduction of the tire pressure.

(8) FIG. 3 illustrates a linear characteristic curve which is stored in the control unit 13 and has an initial increase with respect to the setpoint tire pressure which is to be set. This initials increase decreases continuously from the time t1 to the time t2 in this exemplary embodiment until it drops to the level of the predefined setpoint tire pressure p1. The aeration of the tire is stopped by the control unit if the ACT tire pressure which is measured by the pressure sensor 12 has almost reached the setpoint tire pressure. The closed-loop regulating process also includes predefined threshold values in order to avoid overshooting of the regulating system.

(9) The invention is not limited to the preferred exemplary embodiment described above. Rather, refinements thereof which are also included in the scope of protection of the following claims are also contemplated. It is therefore also possible for example to monitor more than two tires with a single tire inflation device and to inflate them with a predefined tire pressure. A corresponding number of wheel valves are to be integrated into the system for this purpose.

LIST OF REFERENCE SYMBOLS

(10) 1 Compressor

(11) 2 Air dryer

(12) 3 Compressed air consumer

(13) 4 Pressure limiting valve

(14) 5 Tire inflation device

(15) 6 Tire

(16) 7 Relay valve

(17) 8 Working line

(18) 9 Forward pressure wave

(19) 10 Aerating valve

(20) 11 Venting valve

(21) 12 Pressure sensor

(22) 13 Control unit

(23) 14 Wheel valve

(24) P.sub.setpoint Setpoint tire pressure

(25) P.sub.act Actual tire pressure

(26) p1 Predefined setpoint value

(27) t1 Starting point of predefinition of setpoint values

(28) t2 Time for increase

(29) Increase with respect to predefined setpoint value

(30) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.