Pressure supply diagnostics and controls and the tire inflation system made therewith

A method of determining tire pressure includes providing a control unit having a first pressure transducer. The control unit is in fluid communication with a fluid reservoir via an air supply circuit. A second pressure transducer is disposed at least partially within the fluid reservoir. The method also includes measuring a pressure of air in the air supply circuit utilizing the first pressure transducer and measuring a pressure of air in the reservoir utilizing the second pressure transducer. The method additionally includes determining a difference in the measurements of the first pressure transducer and the second pressure transducer and calibrating the second pressure transducer pressure measurement to agree with the first pressure transducer pressure measurement where the pressure difference is less than a predetermined value. The method further includes measuring a pressure in one or more tires.

BACKGROUND

The present disclosure relates to tire inflation systems and to a pressure supply control system.

Tire inflation systems for vehicles provide a vehicle the versatility of adjusting tire pressures while the vehicle is stationary or in motion. For example, the tire pressure of one or more wheel assemblies in fluid communication with a tire inflation system may be decreased to increase tire traction, or increased to reduce rolling resistance and increase the vehicle's fuel efficiency and tire longevity. Furthermore, tire inflation systems increase a vehicle's maneuverability over differing terrains and increase a vehicle's mobility through varying environmental conditions. Additionally, tire inflation systems reduce maintenance requirements.

Legacy tire inflation systems experience performance limitations during tire inflate. The present disclosure provides for a tire inflation system with increased inflate performance.

SUMMARY

In an embodiment, the present disclosure provides for a method of determining tire pressure that includes providing a control unit having a first pressure transducer. The control unit is in fluid communication with a fluid reservoir via an air supply circuit. A second pressure transducer is disposed at least partially within the fluid reservoir. The method also includes measuring a pressure of air in the air supply circuit utilizing the first pressure transducer, and measuring a pressure of air in the reservoir utilizing the second pressure transducer. The method additionally includes determining a difference in the measurements of the first pressure transducer and the second pressure transducer, and calibrating the second pressure transducer pressure measurement to agree with the first pressure transducer pressure measurement where the pressure difference is less than a predetermined value. The method further includes measuring a pressure in one or more tires.

In another embodiment, the present disclosure provides for a method of tire inflation including providing a control unit having a first pressure transducer, wherein the control unit is in selective fluid communication with one or more tires. The control unit is in fluid communication with a fluid reservoir via an air supply circuit. A second pressure transducer is disposed at least partially within the fluid reservoir. The method also includes determining a first pressure in the fluid reservoir necessary to operate a braking system, and determining a second pressure in the fluid reservoir to account for a hysteresis band in measurements of the first and second pressure transducers. The method additionally includes calculating a third pressure via summing the first and second pressures, and determining whether the fluid reservoir pressure is greater than the third pressure. The method further includes determining a virtual pressure switch OPEN and CLOSED threshold values where no check valve fault has been set, and determining a virtual pressure switch status for each one or more tires. The method also includes inflating each one or more tires having a CLOSED virtual pressure switch status.

DETAILED DESCRIPTION

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific assemblies and systems illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined herein. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. Also, although they may not be, like elements in various embodiments described herein may be commonly referred to with like reference numerals within this section of the application.

Embodiments of a tire inflation system10are described below. In certain embodiments, the tire inflation system10is utilized with a vehicle (not depicted). The tire inflation system10may be a central tire inflation system (CTIS) for a commercial vehicle. In addition, the tire inflation system10described herein may have applications in both light duty and heavy duty-vehicles, and for passenger, off-highway, and sport utility vehicles. It would be understood by one of ordinary skill in the art that the tire inflation system10also has industrial, locomotive, military, agricultural, and aerospace applications.

The tire inflation system10is described herein with reference to a pressurized fluid such as, for example, air. The tire inflation system10may have inflate and/or deflate capability to allow a tire pressure to be increased and/or decreased.

As illustrated inFIG. 1, the tire inflation system10may comprise a control unit14. In an embodiment, the control unit14comprises a plurality of valve assemblies18,20,22,24, which may be of the solenoid variety. The control unit14further comprises a control unit first conduit26in fluid communication with the valve assemblies18,20,22,24. The control unit first conduit26is utilized for controlling the flow of, and directing, pressurized fluid through the system10. In an embodiment, the control unit14may comprise a mechatronic control unit (MCU). In another embodiment, the control unit14may comprise a pneumatic control unit (PCU) coupled with an electronic control unit (ECU).

As illustrated inFIG. 1, the control unit14comprises an electronic control portion28. The electronic control portion28may receive input signals from a first pressure transducer16, a power supply30, and one or more additional sensors (not depicted) such as, for example, a load sensor and a speed sensor. The electronic control portion28may also receive input signals from an operator control device32. The electronic control portion28may include a microprocessor34operating under the control of a set of programming instructions, which may also be referred to as software. The electronic control portion28may include a memory (not depicted) in which programming instructions are stored. The memory can also store identification codes, tire pressure records and/or user inputs over a period of time.

The electronic control portion28may output signals to the valve assemblies18,20,22,24to open or close the valve assemblies18,20,22,24. The electronic control portion28may also output signals to a display device (not depicted). The display device may be included as a part of the operator control device32or may be included in a freestanding device.

The control unit14selectively communicates with an air supply36via an air supply circuit38. The first pressure transducer16is in fluid communication with the control unit first conduit26and measures the pressure of the air supply36via the air supply circuit38and the control unit first conduit26. The control unit14may also comprise a control valve assembly24. The control valve assembly24is provided with an orifice (not depicted) which is smaller than the orifice of the supply valve assembly22and is utilized to provide a bleed of air from the air supply36to a fluid control circuit40. In an embodiment, the supply valve assembly22and control valve assembly24are of the solenoid variety.

The air supply36is utilized to check the tire pressure and, if needed, increase and/or decrease the tire pressure. The air supply36provides storage of pressurized fluid such as, but not limited, to air or nitrogen. In an embodiment, the air supply36comprises an air compressor42attached to the vehicle. The air supply36may also comprise a fluid reservoir44such as, for example, a wet tank (also called supply tank). The compressor42is in fluid communication with the reservoir44via a supply conduit46. The air compressor42supplies pressurized air to the reservoir44for storage therein. In certain embodiments, a drier48is provided between the air compressor42and the reservoir44for removing water from the air supply36. Pressurized fluid from the air supply36is provided to the air supply circuit38via the reservoir44. A filter (not depicted) may also be interposed in the air supply circuit38or the supply conduit46.

The control unit14is also selectively in fluid communication with the fluid control circuit40. The fluid control circuit40is utilized to provide fluid communication between the control unit14and one or more tire channels70,72. In an embodiment, first and second tires50,52are in fluid communication with the first channel70, and third and fourth tires54,56are in fluid communication with the second channel72. In an embodiment, fluid communication between the control unit14and fluid control circuit40is controlled by opening or closing a channel valve assembly18.

Each tire50,52,54,56contains air at a certain pressure which will hereinafter be referred to as tire pressure. In an embodiment, the tire pressure is equal to a target tire pressure. The target tire pressure can be selected to be a desired pressure. After the target tire pressure is selected, it is programmed into the control unit14. If it is determined that the tire pressure is less than the target tire pressure, the tire pressure can be increased. If it is determined that the tire pressure is greater than the target tire pressure, the tire pressure can be decreased.

Legacy tire inflation systems utilizing a pressure switch for brake system prioritization experience performance limitations during tire inflate. When a pressure switch is closed it indicates that the availability of pressurized fluid is sufficiently greater than the brake system requirements. However, a pressure switch does not provide the information necessary to determine whether there is a sufficient pressure potential difference between the availability of pressurized fluid and a tire for increasing tire pressure during an active inflate. For example, if the pressurized fluid supply tank pressure is close to the current tire pressure and an inflate is in progress, where the target tire pressure is much higher than the current tire pressure, it would be desirable to stop the inflate activity to preserve the life of the tire inflation system components, and to resume the inflate activity after a compressor sufficiently charges the pressurized fluid supply tank.

As illustrated inFIGS. 1 and 2, in an embodiment, the air supply36may include a second pressure transducer60. The second pressure transducer60may be disposed at least partially within the reservoir44. Further, the second pressure transducer60is in electrical communication with the electronic control portion28. The second pressure transducer may be utilized to determine the exact fluid pressure in the air supply reservoir44. With the second pressure transducer60, the tire inflation system10can constantly provide the available pressure in the air supply reservoir44.

In the tire inflation system10, having the first and second pressure transducers16,60, the software of the electronic control portion microprocessor34may include a tire pressure check algorithm having an additional logic routine100. The additional logic routine100comprises a step102in which the pressure in the air supply reservoir44is measured via the second pressure transducer60, the pressure in the air supply reservoir44is simultaneously measured via the first pressure transducer16by activating the supply valve assembly22and control valve assembly24, and any difference between the two measurements is determined.

In a step104, the additional logic routine100determines whether the difference between the pressure measurements from the step102is greater than a maximum acceptable value. The maximum acceptable value of the difference between the pressure measurements determined in the step102may be previously determined based on sensor tolerances and other system considerations. In an embodiment, the maximum acceptable value of the difference between the pressure measurements determined in the step102may be ±3% of the measured pressure. If the difference between the pressure measurements of the first and second transducers16,60is greater than the maximum acceptable value, the algorithm100sets a transducer erratic fault in a step106. A transducer erratic fault may be caused by a number of electronic or pneumatic issues including, but not limited to, a faulty or loose wire between the air supply reservoir44and the electronic control portion28, a faulty or loose wire between the first pressure transducer16and the electronic control portion28, a blocked valve assembly18,20,22,24in the control unit14, and/or component deterioration of the first or second pressure transducer16,60.

When the erratic fault is set in the step106, an error is communicated to the vehicle operator via a diagnostic tool/interface and the tire pressure check process is aborted to prevent the potential dumping of air supply36pressurized fluid to the atmosphere in a step106A. The tire pressure check process may be resumed/re-attempted on the next tire pressure check interval. In an embodiment, the tire pressure check interval may be 15 minutes, 1 hour, etc., as programmed in the software of the electronic control portion28. In an embodiment, the erratic fault of the step106may be displayed via the operator control device32as an indicator light (not depicted). In another embodiment, the erratic fault of the step106may be communicated to the vehicle operator via audio. For example, a warning tone may sound in the vehicle cabin.

If the difference between the pressure measurements of the first and second transducers16,60is less than or equal to the maximum acceptable value, the additional logic routine100calibrates the pressure measurement of the second pressure transducer60to agree with the pressure measurement of the first pressure transducer16in a step108. After calibrating the first and second pressure transducer offset, any set erratic fault is cleared in a step110.

Each tire's pressure check (i.e., tire pressure measurement routine) involves drawing a small volume of pressurized air into the air supply circuit38, the control unit first conduit26, and the fluid control circuit40to open the wheel valves. After the tire pressure checks, the small volume of pressurized air is dumped to the atmosphere. In an embodiment, the pressure checks for all tires are performed simultaneously, rather than checking the pressure of a few tires and then waiting for the pressure in the air supply reservoir44to sufficiently recharge in order to check the pressures of the remaining tires. The tire pressure checks are performed in sequence without pauses, for lack of air supply pressure, in between successive channels. By auto-calibrating the second pressure transducer60such that the first and second pressure transducers16,60work coherently, wait times in a tire pressure measurement routine are eliminated.

Additionally, auto-calibration of the second pressure transducer60with the first pressure transducer16eliminates a condition where the first and second transducer16,60disagree within the acceptable tolerance (i.e., less than or equal to the maximum acceptable value) such that an erratic fault is not activated, but the tire pressure measurement routine becomes stuck or immobilized.

As illustrated inFIG. 3, the software may include a virtual pressure switch status determination algorithm300. The virtual pressure switch status determination algorithm300utilizes signals of the first and second pressure transducers16,60to define a binary virtual pressure switch status for each of the tire channels70,72. The virtual pressure switch status is either “CLOSED” (i.e., go) or “OPEN” (i.e., no-go). The virtual pressure switch status is utilized by measure pressure and inflate algorithms to perform tire pressure checks or inflates. The virtual pressure switch status provides the need-based and availability-based go or no-go state for each channel70,72to draw from the air supply reservoir44; unlike legacy systems which only provide one state for all channels. For example, a tire50,52,54,56or a channel70,72that has a pressure very low relative to the target tire pressure may receive a CLOSED state, where another tire50,52,54,56or a channel70,72that has a pressure only marginally low relative to the target tire pressure may receive an OPEN state due to insufficient potential difference between the air supply reservoir44pressure and the pressure in the tires50,52,54,56.

The virtual pressure switch status determination algorithm300enables the electronic control portion28to switch between the channels70,72and optimize the tire inflation system performance when the virtual pressure switch status is CLOSED for some channels and OPEN for others. The ability to perform tire pressure checks and inflate activity when the virtual pressure switch status is CLOSED for some channels and OPEN for others reduces the time necessary to achieve the target tire pressures in a scenario where multiple tires need inflation. Additionally, drawing the air supply reservoir44pressurized air when the virtual pressure switch status for at least one channel70,72is CLOSED, rather than waiting for the virtual pressure switch status for all the channels to be CLOSED, activates the air compressor42governor to recharge the air supply reservoir44sooner. Thus, the air pressure that is eventually needed to inflate the remaining channels is available sooner, and the overall system inflate (i.e., all tires) is achieved in the shortest possible time.

The first step302of the virtual pressure switch status determination algorithm300includes determining a necessary pressure250in the air supply reservoir44that is necessary for the prioritized braking system (not depicted) to be operable. The necessary pressure250is a hard-limit below which the virtual pressure switch status for all situations and channels is a no-go.

A second step304includes determining an additional pressure252in the air supply reservoir44to account for a hysteresis band in the measurements of the first and second pressure transducers16,60. The additional pressure252is added to the necessary pressure250to calculate a minimum pressure254. The hysteresis band accounts for pressure measurement of a value following an increase in pressure in the air supply reservoir44, versus following a decrease in pressure in the air supply reservoir44. The minimum pressure254is a minimum above which the virtual pressure switch status transition from OPEN to CLOSED is allowed.

In a third step306, the virtual pressure switch status determination algorithm300determines whether the air supply reservoir44pressure is above the minimum pressure254. Where the air supply reservoir44pressure is below the minimum pressure254, in a step307A, the braking system is prioritized, and the tire inflation system10draws no air to measure the pressure of or inflate the tires50,52,54,56. In a step307B, the virtual pressure switch status determination algorithm300is then restarted after a predetermined period of time.

Where the air supply reservoir44pressure is above the minimum pressure254, the virtual pressure switch status determination algorithm300looks for the presence or absence of a check valve fault in a fourth step308. In an embodiment, the check valve fault may occur in wheel valves80,82,84,86. The check valve fault may be established in a different software module.

In an embodiment, the check valve fault is determined by the ratio of the pressure measured in the fluid control circuit40for a predefined duration when the control valve assembly24is ON, versus when both the supply valve and control valve assemblies22,24are ON. The pressurized air measured in the control unit14is a result of air flow from the air supply36side in both the control valve assembly24ON, and supply and control valve assembly22,24ON cases. In a scenario where there is a check valve failure, air also flows from the tire50,52,54,56side (i.e., both sides of the control unit14). Air flowing into the control unit14from the tire50,52,54,56side skews the expected ratio of the pressure measured in the fluid control circuit40, and the presence or absence of a check valve fault is detected.

Check valve failure is a serious condition; therefore the check valve fault software module may utilize any air available until the air supply reservoir44pressure decreases to the necessary pressure250for the prioritized braking system. The air available to the check valve fault software module does not include any additional pressure252for hysteresis, accuracy, system timing performance, etc., as safety of the vehicle takes precedence in all situations. Where a check valve open fault is set, a tire pressure measurement event is triggered sooner rather than later. For example, if in normal conditions tire pressure was checked every 15 minutes, when a check valve open fault is active tire pressure may be checked every 2 minutes to ensure that tires do not go flat. In an embodiment, the control valve assembly24may be turned ON to close the vent to atmosphere when the check valve fault is active, such that tire pressure is contained in the control unit14and is not lost to atmosphere.

In legacy tire pressure measurement algorithms, a check valve poppet stuck due to debris in the tire inflation system may cause a continuous dump of pressurized air from the air supply reservoir44until the pressure in the reservoir44reaches a minimum pressure. This same phenomenon may occur where there exists any plumbing leakage between the air supply reservoir44and the control unit14. The tire inflation system10provides protection from a stuck solenoid poppet dumping air supply fluid to atmosphere in the step106A discussed supra. When a check valve poppet is stuck, and air supply is dumped to atmosphere, the air supply pressure measured by the first and second pressure transducers16,60differs beyond an acceptable value. An erratic fault is activated, the pressure check is aborted, and the safety goal is achieved.

If the fourth step308determines that there is not a check valve fault, a step310is utilized to determine the virtual pressure switch OPEN and CLOSE thresholds during tire inflation. The first and second pressure transducer16,60offset calibration value determined in step108is included in the virtual pressure switch OPEN and CLOSED threshold values. Once it is ensured that there is sufficient pressure for operation of the braking system, target tire pressure may be utilized to define the OPEN and CLOSED thresholds. In an embodiment, the virtual pressure switch OPEN threshold is equal to the necessary pressure250plus the transducer offset calibration value. In an embodiment, the virtual pressure switch CLOSED threshold may be equal to the necessary pressure250plus the transducer offset calibration value, plus the additional pressure252.

In an embodiment having a check valve based system, air supply reservoir44pressure that is higher than the tire pressure would be required to open the channel valve assembly18,20. The target pressures for front channel tires may be setup differently than rear channel tires. Therefore, it is possible that one set of tires has an OPEN status while the other set of tires has a CLOSED status. For example, one tire pressure may be very low (e.g., due to a puncture) and have a CLOSED status, while another tire has an OPEN status because its last known pressure was much higher (i.e., the air supply reservoir44pressure is inadequate to open that channel's valve18,20).

As described supra, the virtual pressure switch status provides the tire inflation system the opportunity to measure the pressure in, or inflate, one channel while waiting on another channel. This channel differentiation also activates the governor on the air compressor42to recharge the air supply reservoir44such that pressurized air is available more often. After the step310, the virtual pressure switch status determination algorithm300determines the virtual pressure switch status for each tire channel in a step316. In an embodiment, the virtual pressure switch status for each channel70,72is based on the respective target tire pressure and the last known measured tire pressures.

If the fourth step308determines that there is a check valve fault, a step312sets the lowest possible threshold pressure in the air supply reservoir44for the virtual pressure switch OPEN and CLOSED threshold. In an embodiment, the lowest possible threshold pressure is the necessary pressure250. After a predetermined period of time, the tire inflation system10reinitiates the virtual pressure switch status determination algorithm300.

While various embodiments have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant arts that the disclosed subject matter may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments described above are therefore to be considered in all respects as illustrative, not restrictive.