MXPA99001193A - Line pressure control system - Google Patents

Abstract

The present invention relates to a vehicle tire pressure control system having a pneumatic control unit, a pressure sensor, a rotary seal associated with the rim, a wheel valve having a plurality of functional positions and is connected to and rotates with the rim, an input connected to a source of compressed air, the control unit being connected through a connecting line and the rotary seal to the wheel valve, and the functional position of the wheel valve being controlled as a function of a pressure level in the connecting line, the functional positions of the wheel valve including a closed position, an open position connecting the control unit to the rim, and a ventilation position which is opens the rim to the atmosphere, the wheel valve occupies its open position as soon as an inflation pressure exists in the connection line, the wheel valve occupies its ventilation position whenever there is ventilation pressure in the connection line that exceeds the inflation pressure by a predetermined amount, the wheel valve occupies its closed position as soon as there is a closing pressure in the line of connection which is less than the inflation pressure at least by a predetermined pressure difference characterized by: a pressure level line, the first and second parallel pressure lines between the source of compressed air and the level line of pressure pressure, a high pressure valve in the first pressure line, a medium pressure valve in the second pressure line, the high pressure valve and the average pressure valve can each be changed between a closed position and an open position; and a pressure reducing valve in the second pressure line to regulate an inflation pressure

Description

RING PRESSURE CONTROL SYSTEM Background of the Invention This invention relates to a tire pressure control system and method, and more particularly, to such a system which includes a tire control unit, a pressure sensor, a rotary seal associated with a rim and a tire valve. wheel turning with the rim that can move to various positions. The system is connected to a source of air pressure. The control unit is connected through a connection pipe and the rotary seal is connected to the wheel valve, each of whose positions is a position of the pressure level in the connection line.

Tire pressure is regulated in agricultural vehicles such as tractors to conform to the particular operating condition of the moment. The tractors are increasing in capacity of force and in total weight. In order to reduce the undesirable compaction of the ground, the systems for regulating the tire pressure can reduce the pressure during operation in the field in contrast to the pressure during the operation on the road.

Patent EP-B1-0 164 917 shows a central tire inflation system with control devices and a wheel valve. The control devices provide an inlet pressure for a first connection of a pressure reducing valve. The pressure reducing valve contains a second connection that opens to the atmosphere and a third connection that is connected on a connection line and a rotary seal with a rim valve rotating with the rim. The first connection and the third connection of the pressure reducing valve are connected to each other when the inlet pressure exceeds the pressure at the third connection. The third connection is connected to the ventilation connection when the pressure at the third connection exceeds the inlet pressure. The wheel valve is connected to a tire that can be inflated. This makes possible an opening when a pressure is applied to the inlet side which exceeds a first reference pressure and when the pressure in the rim lies above a minimum wheel reference pressure. The rim is ventilated through the pressure relief valve that is located in front of the rotary seal. For this purpose the system must be pressurized with a vent pressure so that the wheel valve takes its open position. This pressure of ventilation opposes the actual ventilation of the pressure chamber, which harms the ventilation process. Beyond this, the ventilation connection located in front of the pressure chamber slows down and damages the ventilation process.

DE-OS-3836105 discloses a tire pressure regulator installation for off-road motor vehicles consisting of a combination of stationary valve, a rotary seal for the wheel for a pressurized air supply line as well as for a control pipe and a valve combination for each wheel rotating with the wheel. The stationary valve combination includes a relay valve, at least one pilot valve and one shut-off pressure control valve. The valve combination rotating with the wheel includes a wheel control valve which is opened by a pressure pulse from the supply line and closed by the control pressure in the control line, and a localized quick release valve ahead of it which is used to vent the tire pressure. A check valve can follow the vent opening of the quick release valve. In this configuration the control piping as well as the supply piping must be connected through a rotary seal with the wheel control valve. This is expensive and expensive.

Synthesis of the Invention An object of the present invention is to provide a rim pressure control system having a simple configuration and which can quickly vent a rim.

These and other objects of this invention are achieved with a tire pressure control system that includes a pneumatic control unit, a pressure sensor, a rotary seal and a wheel valve rotating with the wheel in various positions. The system is connected to a source of compressed air and the control unit is connected via a connection pipe and the rotary seal to the wheel valve whose position at the moment is a function of the pressure level in the connecting pipe . The wheel valve is provided with at least one closed position, an open position as well as a ventilation position that opens to the surrounding atmosphere. The wheel valve occupies its open position whenever there is an inflation pressure in the connection pipe. The valve will be in its ventilation position as long as there is a pressure in the connecting pipe that exceeds the inflation pressure at least by a predetermined value, and this will be in its closed position whenever there is a closing pressure in the pipeline. connection that is below the inflation pressure at least by a predetermined pressure difference. Here the ventilation is carried out directly on the wheel, which reduces the time required for ventilation. Only one pipeline must be taken through the rotary seal since the control of the wheel valve is carried out exclusively by the pressure in the connecting pipe and not by an additional control pipe.

This system allows a quick modification of the limitation values to accommodate the changes of the tires and the load. This offers advantages, in particular, if the tire pressure is changed frequently in order to regulate it optimally and smoothly according to the specifications of the tire manufacturer as a function of the operating conditions, the wheel load and the speed of real operation. The actual tire pressure limit values can be established with a change of the tires either by the operator or through an appropriate responder built in the tire.

The actual load of the rim can be determined by the deflection of the vehicle spring.

If the pressure is to be regulated on several tires of the vehicle, these tires are preferably connected with a common stationary pneumatic control unit. This allows a reduction in the number of components. The pneumatic control unit is preferably a modular valve block.

The stationary pneumatic control unit can also be used to regulate not only the tire pressure of a vehicle but also the tire pressure of one or more attachments or trailers connected to the vehicle.

It is advantageous to hold the tire control unit as a stationary device to the vehicle. Therefore a regulation of the pressure can be carried out at any time without the need to use an external control facility. A pneumatic control system attached to the vehicle can be applied with great advantage for regulating the pressure of a trailer or of an implement connected to the vehicle. When joining a trailer or changing a trailer, only the particular pipes need to be connected and no additional costly modification work is required.

Preferably, the wheel valve is ur-to spool valve. The spool valve is brought to each of its positions as a function of the pressure in the connecting pipe. The spool valves are simple in configuration and are not sensitive to the flow rate. These are used frequently and are therefore cost effective. The wheel valve is loaded by a spring which opposes the air pressure in the connecting pipe that controls the wheel valve. The design of the spring allows the definition of the selector pressure points of the various valve positions.

It is advantageous that the rims of at least the axle of the vehicle and / or of a connected implement or of a trailer are connected in each case through the associated wheel valves and of the rotary seals with only one connection pipe. associated with the axis. The connecting pipe can be connected through a selector valve associated with a pressure level pipe of the pneumatic control unit. In this configuration the regulation of the pressure in the rims of an axle is carried out together, so that the same pressure is applied on all the wheels on an axis. This is advantageous since the wheels of an axle are usually subjected to the same loads. Beyond this, the number of individual components forming the pneumatic control unit is reduced.

It is appropriate that the pneumatic control unit contains at least one high pressure valve and one medium pressure valve which are arranged in parallel lines between the source of compressed air and the pressure level pipe and each can be switched between a blocking position and an open pressure. In the pipe of the valve of average pressure a valve of reduction of pressure is arranged, which regulates the inflation pressure. The pressure regulated by the pressure reducing valve is higher than the maximum required inflation pressure of the tires, however, it is lower than the pressure required to bring the rim valve to its ventilation position. As long as the pressure level pipe is connected to the connecting pipe, the wheel valve occupies its ventilation position if the high pressure valve is open. This occupies its open position when the medium pressure valve is open, and the wheel valve is loaded by the pressure decreased by the pressure reducing valve.

To enable remote regulation and remote monitoring of the systems from the operator's cab of a vehicle, the selector valves and / or the high pressure valve and / or the medium pressure valve are electromagnetic valves which are controlled to through an electronic unit.

When these are not activated the selector valves and / or the high pressure valve and / or the medium pressure valve preferably occupy their blocking position. In the selector valves the blocking position preferably corresponds simultaneously to the ventilation position for the connection pipe. Therefore the wheel valve is in its closed position when the electromagnetic valves are de-energized, so that during a failure of the power supply the tires are not ventilated. The data detected by a pressure sensor in the pressure level pipe are preferably processed by an electronic or electrical unit. It is therefore possible for the electronic or electrical unit to automatically carry out a ventilation or inflation process necessary to reach a preselected or required pressure.

An electric or electronic control unit can bring the wheel valve to a particular desired position to ventilate or inflate to the closed position. Beyond this, the electronic or electrical unit allows the monitoring and testing of the wheel valve. This allows controlled pressure regulation and pressure monitoring of several wheel valves.

With this system the inflation pressure is applied briefly to the rim valve in order to bring the rim valve to its open position. Then the value of the actual pressure on the rim in the connecting pipe is measured. An inflation duration is determined from a comparison between the value of the actual pressure and a target pressure value that can be predetermined. After this, the inflation pressure or the ventilation pressure is applied to the wheel valve for the determined time interval, in order to carry out an inflation or ventilation of the rim. The process allows precise and rapid regulation of the tire pressure.

Preferably, these process steps are repeated until the target pressure value lies within a predetermined tolerance band, whereby a repetitive approach to the required pressure occurs. The operation of the described process can be improved by the application of an electronic unit. In the electronic unit, an initial predetermined functional relationship of the actual / target value difference and the duration of inflation or ventilation is stored in the memory. This reproduces the flow relationships or system parameters. The functional relationship is varied by considering the actual / initial target difference and the sum of the individual inflation or ventilation durations in order to make them conform to the true relationships such as, in particular, the actual flow characteristics and the tire parameters. These process steps ensure that the system conforms to changes in flow characteristics and tire parameters. It is also possible to determine and regulate the tire pressure depending on the variable road conditions, the wheel load and the speed.

Brief description of the Drawings Figure 1 is a schematic diagram of a tire pressure control system according to the present invention.

Figure 2 is a diagram which illustrates the operation or process for regulating the pressure of a tire.

Description of the Preferred Incorporation A vehicle (not shown), such as an agricultural tractor, is equipped with a system 10 for regulating the pressure in its rims 12 and 13. As shown in Figure 1, the system 10 includes a pneumatic control unit 22 which is connected with the four rims 12 and 13 to the connecting pipes 24. Each rim 12 is associated with a rotating seal 26 which connects the connecting pipe 24 with a wheel valve 28 rotating with the wheel. Each wheel valve 28 is connected through a connecting pipe 29 to the inside of the associated rim 12 and 13. The system is connected to a reservoir 14 through a supply pipe 16 in which the discharge valve 18 it is provided. The reservoir 14 supplied with pressurized air by a source of compressed air 20, such as a compressor that supplies priority pressure to the air brake system.

The pneumatic control unit 22 is attached to the vehicle and is stationary with respect to the vehicle. The supply pipe 16 of the tank 14 divides the control unit 22 into two pipes 30 and 32. The first pipe 30 contains a high pressure valve 34 in the form of a spring-loaded electromagnetic valve with an open position 34 'and a closed position 34"The second line 32 includes a medium pressure electromagnetic valve 40, with an open position 40 'and a closed position 40". The pipe 32 also includes a pressure reducing valve 42 upstream of the valve 40. After the high pressure valve 34 and the medium pressure valve 40, the two pipes 30 and 32 are combined in a pressure level pipe 25. The pressure level pipe 25 is connected to a pressure sensor 44.

The pressure level pipe 25 is connected to identical selector valves 46 and 48 configured as spring loaded electromagnetic valves, each having an open position 46 'and 48' and a ventilation position 46"and 48". One of the selector valves 46 and 48 is connected to a corresponding connecting line 24, both are connected to the rims 24 through the wheel valves 28. In its ventilation position, the selector valve opens the connecting pipe 24 to the atmosphere, and there is no pressure in the connecting pipe 24, and therefore there is less stress on this pipe. When there is no pressure in the connecting pipe 24 the wheel valve 28 is closed so that the pressure of the rim is not bled through the wheel valve 28. Simultaneously, the pressure level pipe 25 is blocked in a manner that his pressure is maintained. In this open position the pressure line 24 is connected to the pressure level line 25. The selector valves 46 and 48 are located between the pressure level line 25 and the connection line 24. The selector valves 46 and 48 can be switched between the ventilation and opening positions.

The wheel valve 28 is configured as a spool valve with a closed position 54 ', an open position 54"and a venting position 54' '' A spring 56 at one end of the spool pushes the spool of the wheel valve 28 to its closed position 54 'At its other end the reel is exposed to pressure in a control line 58, which is connected to the connection pipe 24. Corresponding to the pressure level provided by the control unit 22 in the connecting pipe 24, the wheel valve 28 takes one of its three positions 54 ', 54", 54' ''. The pneumatic control unit 22 is connected to an electronic unit 60 which controls the selector valves 46, and 48, the medium pressure valve 40, the upper pressure valve 34 and evaluates the measured values of the pressure sensor 44.

Operation The relief valve 18 in the supply pipe 16 opens only when there is a predetermined minimum pressure in the tank 14. This ensures that the pressurized air flows out of the tank 14 only when the pressure is above the minimum pressure required to supply a compressed air braking system. In order to determine whether the reservoir 14 contains the pressure required for the operation of the high pressure valve system 34 it can be opened. Therefore the reservoir 14 is connected to the pressure sensor 44. The pressure sensor 44 transmits the determined data to the electronic unit 60 in order to avoid an inflation process if a sufficient air pressure is not available.

To inflate the tires, the medium pressure valve 40 is moved to its open position 38 by means of the electronic unit 60. In addition, the selector valve 46 is moved to its open position 46 'by the inflation of the front axle tires 12. 50 or the selector valve 48 is put in its open position 48 'for inflating the rims 13 of the rear axle 52, or both selector valves 46 and 48 are put in their open position 46', 48 '. Since the pressure reducing valve 42 is arranged in front of the medium pressure valve 40, the connecting pipe 24 carries an inflation pressure which is reduced from the pressure in the tank 14. This reduces the pressure as it is applied to the pipeline. connection 24 and on the control pipe 58 to the spool of the wheel control valve 28 so that the wheel control valve 28 moves to its open position 54"and the tires 12 and 13 are inflated. ventilating the rims 12 and 13, the medium pressure valve 40 is closed and the valve selector 46 and the selector valve 48 in each case is put in its open position 46 'or 48' The operating pressure of the reservoir 14 here controls the wheel valve 28 directly and brings it to its ventilation position 54 '' 'The interior of the rims 12, 13 is thus directly vented to the atmosphere without being opposed by ventilation by a control pressure or by having travel through trajectories of long connections.

If the tires 12 and 13 are not to be inflated or ventilated, then the electromagnetic valves 34, 40, 46, 43 are de-energized and therefore closed. In this position the selector valves 46 and 48 open the connecting pipe 24 to the surrounding atmosphere, so that no pressure is applied to the spool of the wheel control valve 28 and this is moved to its closed position 54 'in which the connection pipe 29 is closed.

In order to regulate the tire pressure first a brief inflation process is carried out so as to bring the rim valves 28 to their open positions 54", then the electromagnetic valve 40 is closed and the pressure sensor 44 is connected to the pressure exiting in the connection pipe 24, which corresponds to the pressure in rim 12 and 13.

Between the inflation, ventilation or measuring processes, the selector valves 46 or 48 are in their ventilation position 46"or 48", so that the connection pipe 24 is connected to the surrounding atmosphere and therefore the region of the seals Rotary 26 is no longer loaded with pressure.

Referring to Figure 2, the control system operates as follows. At certain points in time that are determined either by the electronic control unit 60 or manually, for example, by the vehicle operator, a tire pressure regulation process is initiated. First, the inflation pressure is briefly applied to the rim valve 28 (opening valves 40 and 46 or 48). Then, the pressure of both rims, PO, is perceived in the connecting pipe 24 by the pressure sensor 44. From this perceived rim pressure, PO, the electronic unit 60 determines whether the regulation of rim pressure is necessary by comparing the perceived rim pressure with a desired predetermined rim pressure Pl. If the perceived pressure PO differs from the desired pressure Pl, then the electronic unit 60 determines a time interval ti for a required ventilation or inflation process. The inflation pressure or the ventilation pressure is applied by a corresponding control of the electromagnetic valves 34, 40, 46 and 48 for the time interval ti to the wheel valve 28 so that the tires are inflated or ventilated in a correspondent. After the time interval of inflation or ventilation has expired, the tire pressure reaches the pressure Pm and this pressure is perceived. If the new perceived pressure Pm still does not equal the desired pressure Pl, then the process is repeated. This is continued until the desired pressure Pl is reached. Through this process a repetitive approach is made to the desired pressure Pl. This process can be terminated if the perceived pressure is within a tolerance band T of the desired pressure. This process can also be terminated if a certain number of inflation or ventilation cycles have been carried out, in which case the process is terminated if a tire is defective and the desired pressure Pl can not be reached.The steps of the described process are controlled by the electronic unit 60. The unit 60 stores in the memory an initial theoretical functional relationship, represented in Figure 2 by the line F, between the duration of inflation or ventilation time and the difference between the tire pressure perceived and desired. On the basis of the stored ratio, the regulation of the repetition of the duration of inflation and / or ventilation is carried out. When the tire pressure reaches the tolerance band T, then the inflation or ventilation process is finished. From the inflation or ventilation durations, the electronic unit 60 determines an actual functional G relation which is stored in the memory and which is used to control the subsequent inflation and ventilation processes. In this way the process is done to conform to the actual flow conditions in the system.

In the embodiment shown, the two rims 12 of the front axle 50 or the two rims 13 of the rear axle 52 are each regulated in common. It is also possible to regulate each tire 12 and 13 individually or the tires 12 and 13 of the complete vehicle together. It is also possible to include the tires (not shown) of a trailer (not shown) in the system. Up to now it is possible to regulate the tires of a trailer, for example, individually, in pairs or in combination with the tires 12 of the vehicle.

Even though the invention has been described in terms of only one embodiment, any person skilled in the art will perceive many alternatives, modifications and variations in light of the foregoing description as well as the drawing, all of which fall within the present invention.

Claims (18)

R E I V I ND I C A C I O N S

1. A tire pressure control system for a vehicle having a pneumatic control unit, a pressure sensor, a rotary seal associated with the rim, a wheel valve having a plurality of functional positions and which is connected to the rim and it rotates with it, an inlet connected with a source of compressed air, the control unit is connected through a connecting pipe and the rotary seal to the wheel valve, and the functional position of the wheel valve is controlled as a function of a pressure level in the connection pipe, characterized in that: the wheel valve functional positions include a closed position, an open position that connects the control unit with the rim, and a ventilation position which opens the rim to atmosphere, the wheel valve occupies its open position whenever there is an inflation pressure in the connection pipe, the wheel valve occupies its ventilation position whenever there is a ventilation pressure in the connection pipe which exceeds the inflation pressure by a predetermined amount, the wheel valve takes its position closed whenever there is a closing pressure in the connection pipe which is less than the inflation pressure at least by a predetermined pressure difference.

2. The control system as claimed in clause 1 characterized in that: the pneumatic control unit is connected with a plurality of rims, wherein each of the rims is associated with its own rotating seal and a wheel valve.

3. The control system as claimed in clause 1 characterized in that: the pneumatic control unit is attached to the vehicle and is fixed with respect to the vehicle.

4. The control system as claimed in clause 1 characterized in that: The wheel valve comprises a spool valve with a mobile valve spool there.

5. The control system as claimed in clause 1 characterized in that: The wheel valve includes a spring which acts on one end of the spool and which opposes the pressure in the connecting pipe acting on the other end of the spool, the spring defines selector pressure valves for various valve positions.

6. The control system as claimed in clause 1 characterized in that: the pneumatic control unit includes a selector valve, the selector valve has a ventilation position which opens the connecting pipe to the atmosphere.

7. The control system as claimed in clause 1 characterized in that the pneumatic control unit comprises: a pressure level pipe; a selector valve located between the pressure level pipe and the connection pipe, the selector valve being switchable between a ventilation position where the connection pipe is vented to the atmosphere and the pressure level pipe is blocked, and an open position where the connecting pipe is connected to the pressure level pipe.

8. The control system as claimed in clause 1, characterized in that it also comprises: a pressure level pipe; a group of wheels are associated with an axle, each rim of said group is connected through an associated wheel valve and a rotary seal with a connecting pipe for said group, and a selector valve controls the communication between the pipeline connection and the pressure level pipe.

9. The control system as claimed in clause 8 characterized in that: The selector valve is composed of an electromagnetic valve which can be controlled by an electronic unit.

10. The valve control system as claimed in clause 11 characterized in that: the selector valve moves to a closed position when it is de-energized.

11. The control system as claimed in clause 1, characterized in that it comprises: a pressure level pipe; the first and second parallel pressure pipes between the compressed air source and the pressure level pipe; a high pressure valve in the first pressure pipe; an average pressure valve in the second pressure line, the high pressure valve and the average pressure valve each being switchable between a closed position and an open position; Y a pressure reducing valve in the second pressure line to regulate an inflation pressure.

12. The control system as claimed in clause 11 characterized in that: at least one of the high pressure and medium pressure valves is composed of electromagnetic valves which can be controlled by an electronic unit.

13. The control system as claimed in clause 12 characterized in that: the high pressure valve and the medium pressure valve move to closed positions when de-energized.

14. The control system as claimed in clause 7, characterized in that: a pressure sensor is connected to the pressure level pipe and transmits a pressure signal to an electronic unit, the electronics unit controls the pneumatic control unit as a function of a perceived pressure.

15. A method for controlling the pressure in a rim with a pressure control system having a pneumatic control unit, a pressure sensor, a rotary seal associated with the rim, a wheel valve connected to and rotating with the rim, an inlet connected to the source of compressed air, the control unit being connected through a connection pipe to the rotary seal with the wheel valve, which comprises the following steps: briefly apply an inflation pressure to the wheel valve; immediately after receiving the actual tire pressure value in the connecting pipe; comparing the actual pressure value with a predetermined desired pressure value; from the comparison result determine an inflation time interval or a ventilation time interval; Y Subsequently, apply the inflation pressure or the ventilation pressure to the wheel valve for the corresponding time interval.

16. The method as claimed in clause 15 characterized in that: said method steps are carried out repeatedly until the actual pressure lies within a predetermined tolerance band of the desired pressure.

17. The method as claimed in clause 15 characterized in that: the steps of the method are controlled by an electronic unit which stores in its memory an initial functional relationship between a time interval of inflation and a difference between the perceived and desired pressure, and where the stored functional relationship is varied as a ratio of an initial difference between the perceived and desired pressure and a sum of other time intervals of the inflation required to achieve the desired pressure.

18. The method as claimed in clause 15, characterized in that. the steps of the method are controlled by an electronic unit which stores in its memory an initial functional relationship between a deflation time interval and a difference between the perceived and desired pressure, and wherein said stored functional relationship is varied as a function of an initial difference between the perceived and desired pressure and a sum of other deflation time intervals required to achieve the desired pressure.