AU638213B2 - Electronic and pneumatic device for controlling and distributing pressure - Google Patents

Description

t

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION 638213 Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: 0O OS 6 0 0

S

*000

S

Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: COL-VEN S.A.

RUTA 11, KM 814, 3574 GUADALUPE NORTE SANTA FE

ARGENTINA

Actual Inventor: Address for Service: *0 GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: ELECTRONIC AND PNEUMATIC DEVICE FOR CONTROLLING AND DISTRIBUTING PRESSURE.

The following statement is a full description of this invention including the best method of performing it known to me:- 1A APPARATUS FOR CONTROLLING AND DISTRIBUTING TYRE AIR-PRESSURE Fipld of the Tnrvention: The instant invention comprises an electronic and pneumatic apparatus for controlling and distributing air pressure in vehicle tyres. The apparatus includes a pneumatic circuit for distributing air from an internal pressure source, such as the compressor of a pneumatic braking system of the vehicle, and an electronic circuit interfacing the pneumatic circuit for sensing tyre air-pressure and metering air from the air source to the different tires as needs be.

aR~krnn of t.h Tnv7ntin: A tyre may wear unevenly and its life span shorten if left to roll at low pressure for substantial mileage. Moreover, when air-pressure in the different tyres is uneven or inadequate in any way, vehicles are open to accident if 15 braked suddenly at high speed or when transporting heavy *6* loads. The development of new means of transport, both for goods and passengers, and improved road construction have brought lorries of ever increasing size and speeds as well as slicker and faster motor-cars on the roads. It is thus **ee S 20 essential for road safety that technologies regarding all the different vehicle parts keep pace by providing means preventing minimum fault which could lead to catastrophic results.

Equipment is already known for regulating air-pressure 25 in tyres in both light and heavy vehicles. It generally 0 comes with a control panel mounted to the vehicle dashboard for the driver to keep a check on tyre pressure status. The object of this sort of equipment is to enhance vehicle safety and protect tyres from damage through inadvertant use 30 at inadequate pressure levels.

aimmar'y of thpe Prio n Art-.

Mechanical air-pressure regulators comprise a diaphragm means driven by a screw-spring mechanism. Although they have proven some worth in protecting tyres and making vehicles /O 5 safer, their intrinsic mechanical nature causes them to be 2 insensitive to small pressure variations, rendering them unprecise for keeping the initial pressure the same. They are also unable to restore the exact set (or initial) pressure to a leaked tyre or take some time to do so.

Other apparatuses come with automatic electromechanical regulators of the type designed originally for refrigerators, air conditioners and the like, not really adequate constructively for tyre pressure regulators. The variety and relative complexity of the parts that make them up make them difficult to assemble and prone to continuous maintenance because of early wear of some parts, particularly the air distribution rotor damaging electrical connections arnd pipe joints. In fact, they have not seemed to attain the purpose for which they were developed, that Ia is, in extending tyre-life.

U.S. patent n° 4,782,879 to Le Chatelier et al discloses a distributed air-pressure system including separate high and low pressure circuits for pressure-gating valves spread out along the installed system. The circuits supply either subatmospheric pressure to the associated valve to open the tyre circuit to a purge or high pressure to inflate the tyre. The patented system also includes a computer/calculator control unit connected to pressure measuring units, with which they interface via rotary transformer 'device mounted on each axle end.

The disclosed components z.re costly and difficult to manufacture, requiring highly skilled control technicians on the assembly line. In addition, the system is both cumbersome and expensive to use on vehicles; for instance, in the 00• 30 case of a two-axle tractor drawing a three-axle trailer, the system would need eighteen pressure controllers, twenty three-way solenoid valves, a pressure regulator, a central e:gg control unit, eighteen manometers or the like plus corresponding interfaces for transmitting electrical signals to the control unit.

Moreover, the size and weight of the device mak- it difficult to mount to the wheel and contribute significantly j.0TCa>. to wheel imbalance.

3- As to tyre-pressure detection, U.S. patent no.

4,599,902 to Gray discloses an apparatus comprising a moveable or deformable pressure-responsive control element for engagement to a tyre inlet/outlet. This control element, preferably in the form of a Bourdon-tube pressuregauge, has a vane attached to it which switches in and out of a LED/phototransistor coupler which drives an output transistor to connect a pulse generator to suitable alarm or control means responsive to a low-pressure indicative signal to pump the tyre up.

This device is by its very nature sensitive to mechanical vibrations and jerks, rendering it unsuitable for vehicles subjected to severe travelling conditions, such as encountered when transporting heavy loads on rough and earth roads or in bad weather conditions.

A need is therefore felt for robust yet simple means for detecting and distributing air and for an li apparatus promoting a simple yet reliable design.

eo :Got -SUMMARY OF THE INVENTION 20 It is an object of the present invention to

*SS.

provide an apparatus for controlling and maintaining the air pressure in land vehicle tyres which attempts to alleviate at least one of the disadvantages in the above described prior art.

25 According to the invention there is provided an

CC

apparatus for a vehicle having a plurality of axles and a obe compressor, said compressor having an output for outputting air at a nominal pressure, at least a pair of wheels se: mounted on each axle, a tyre mounted to each wheel and normally pumped up with air to at least a set pressure less than said compressor nominal pressure, said apparatus o0 controlling and maintaining air pressure in said tyres and comprising: a plurality of pneumatic circuits, each of said tyres associated with a respective one of said pneumatic circuits, each pneumatic circuit including piping means for 3A monitoring and carrying air to said associated tyre; means for distributing pressurised air from said compressor to each of said piping means; each of said pneumatic circuits further comprising: an electrovalve means disposed in the associated piping means; a rotary coupling means mounted to the axle on which the associated tyre is mounted for coupling said piping means and said associated tyre in a manner to allow said pressurised air to flow therebetween; a pressure sensor connected to a point on the piping means intermediate said electrovalve means and said associated tyre, said pressure sensor adapted to generate an electrical signal indicative of whether air pressure in said associated tyre is higher or lower than said set pressure; and, S* an electronic circuit responsive to said airpressure indicative signal to cause the electrovalve means to open when and while the air-pressure in the associated tyre is lower than said set pressure.

°BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic of the electronic circuit of the invention, contained in the unit of Figure 1.

o 4 Figure 2 is a schematic of the pneumatic circuit of the invention which interfaces with the electronic circuit of figure 1.

Detail di Dr Rniption o-f an mhniment nf Ehp Tnventinn Refering to figure 1, the apparatus of the invention comprises an electronic control unit including a pushbutton 1 and LED indicators 2, 3, 4, 19 and 19A. The pushbutton switch 1 enables the driver to activate or deactivate the apparatus. In the deactivated state, tyre pressure is not monitored, one of the LEDs 2 lighting up to warn the driver of this unprotected mode. LED 2 is preferably red and also lights up if the compressor C (figure 2) outlet pressure is lower than nominal.

The control unit comprises an electronic circuit shown :15 schematically in figure 1. Power is supplied by the vehicle's battery (not shown) via a battery terminal and •e the push-button switch 1 to a voltage regulator 20. The red LED 2 is in parallel with the switch and thus permanently see• connected to the battery terminal In the deactivated 20 mode, the switch 1 connects the red LED 2 to ground voltage so that it lights up.

Pressing the button 1 activates the apparatus, whereby LED 2 is turned off and electric current from terminal is supplied to the voltage regulator circuit 20, to a green 25 LED 3 and to LEDs 4 lighting up a plurality of pressure gauges 27, one for each tyre P (figure The electronic "S circuit of figure 1 interfaces with the pneumatic circuit of figure 2 by means of pressure sensors 22 and electrovalves 24.

Figure 2 shows the pneumatic circuit which is airpressurized by the compressor C to maintain and sustain, when required, the tyres P of a vehicle properly pumped up.

Only two such tyres P are shown for the sake of simplicity to illustrate the basic circuit and the add-ons for each tyre P. The compressor outlet is connected to the compressor pressure sensor 21 and, via piping 23, to the tyres P. Each s tyre circuit 23 includes a check valve 24-A, the 5 electrovalve 24, the pressure sensor 22 and the pressure gauge 17, before joining a rotor or rotary coupling 25. The wheel includes a second check-valve 26 connecting the tyre P to the rotary coupling 25. Both check valves 24-A, 26 protect the tyre system from leaking should any part of the piping 23 be damaged or the compressor C be disconnected for servicing).

Operation is as follows. The pressure sensors 22 are calibrated to a threshold value corresponding to normal tyre pressure, say 95 psi (6.7 kg/cm 2 The compressor outlet pressure is normally much higher of course. In the event tyre P, for instance, should leak air and lose a certain amount of pressure, say down to about 90 psi (6.3 kg/cm 2 its corresponding sensor 22 generates an electrical signal for the tyre monitor circuit 14-15-16 (figure 1) to open electrovalve 24, in order to let pressurized air through from the compressor C to the tyre P. Once the tyre has re- S*Q* covered the right pressure (95 psi), the pressure sensor 22 signals the monitor circuit to close the valve 24 back 20 again. The driver may monitor all tyre pressures visually by means of the gauges 19.

The source pressure sensor 21 responds to inlet pressure supplied by the compressor C. Refering back again to figure 1, inlet pressure being normal, that is, over a predetermined threshold, a light passage between a LED 5 and an associated phototransistor 6 is blocked. A pull-up resistor at the phototransistor's collector then forces the negative (or inverting) input of an operational amplifier (op-amp) 7 up and over the voltage at the positive (or noninverting) input which is set by a voltage-divider resistor network 8. The output of the op-amp 7 is connected by a feedback resistor 9 to enhance hysteresis in the switching response of the op-amp 7. The low level normally S* present at the output of the op-amp 7 is twice inverted by a pair of cascaded logic inverter gates 10 and 11 and shuts off a driver transistor 12. The op-amp 7 and its associated circuitry condition the signal derived from the pressure L sensor, in particular to sharpen driver transistor 12 6 a

SP

o 00 990 a..

S

0 s.

S..

e switching and introduce hysteresis to avoid oscillations when pressure is near thxeshold levels or from mechanical vibrations, which could be encountered if the vehicle travels over rough terrain.

This driver transistor 12 connects the cathode of warning LED 2 to ground, in parallel with the push-button switch 1. If the compressor C pressure is too low, the light passage 5-6 will become unblocked, resulting in that the driver transistor 12 turns on and, consequently, so does the LED 2.

The electronic circuit in figure 1 comprises a plurality of tyre monitor circuits 14-15-16 and 14A-15A-16A.

Again, only two such tyre monitor circuits are shown for simplicity. These circuits may correspond to the tyres P (figure 2) of a two-wheel axle of the vehicle, for example.

If tyre pressures are at the right level, the corresponding pressure sensors 22 will block the light passages, formed between respective pairs of LED 13, 13-A and phototransistor 14, 14-A assemblies. The photo- 20 transistors 14, 14-A are in emitter-follower configurations, so that the associated op-amps 15, 15-A will normally supply high levels to respective logic NOR gates 16, 16-A. The resulting logic low levels at the ouput of these NOR gates 16, 16-A will thus keep driver transistors 47A, 47B in the 25 off state. These driver transistors 47A, 47B form solid state switches in series with the solenoids of a pair of electrovalves 24. The electrovalves 24 control high pressure air supply from the compressor C to the respective tyres P through the pneumatic circuit disclosed hereinafter in connection with figure 2.

If pressure at one (or more) of the tyres P (say the tyre P associated with tyre monitor circuit 14-15-16, for instance, the other tyre monitor circuit 14-A 15-A 16-A being identical), drops down low, light from the LED 13 will impinge on the phototransistor 14 in the corresponding pressure sensor 22, driving it to saturation. The op-amp will receive a high voltage at its negative input so that sg its output will go low, the NOR gate 16 output go high, and Si-' 7r -7 driver transistor 17 saturate to energize the solenoid of the corresponding electrovalve 24. As a result, the valve 24 will open to let pressurized air enter the tyre P until the tyre has been inflated to a predetermined pressure (plus a bit more to allow for hysteresis). The feedback resistors may be dimensioned so that the response function has hysteresis in the 90-100 psi (6.3-7.1 kg/cm 2 range.

The NOR gates 16, 16-A have a second input each jointly connected to the output from the op-amp 7 in the compressor J. 0 monitor circuit, to ensure that the tyre electrovalves 24 are kept closed in the event that the compressor C should become ander pressurized. This will protect the tyre P from becoming even more unpumped in such a circumstance and will also ensure that compressor pressure is not permanently lost in the event of a big tyre leak, such as a blow-out. Thie is importani. to preserve vehicle braking ability.

It may be seen that one of the advantages of tiinvention is that the pressure sensors 22 and electroval-ves 24 may all be conveniently housed under the dashboard. This minimizes electrical wiring and enables use of electrovalves without needing lengthly electrical leads other than for the power supply All piping 23, including from a trailer hooked on to the back of the lorry, is connected straight from the rotors 25 to dashboard location. This has several 215 advantages, such as simplifying maintenance and shielding devices 22 and 24 from bangs and dirt and reducing the chances of an electrical wire being severed or having to be layed out in protective shieths.

Although a preferred embodiment has been brought out in to the drawings, the invention is by no means limited thereto but rather extends to all embodiments within goo* the purview of the appended claims.

0 0

Claims (2)

1. Apparatus for a vehicle having a plurality of axles and a compressor, said compressor having an output for outputting air at a nominal pressure, at least a pair of wheels mounted on each axle, a tyre mounted to each wheel and normally pumped up with air to at least a set pressure less than said compressor nominal pressure, said apparatus controlling and maintaining air pressure in said tyres and comprising: a plurality of pneumatic circuits, each of said tyres associated with a respective one of said pneumatic circuits, each pneumatic circuit including piping means for monitoring and carrying air to said associated tyre; means for distributing pressurised air from said compressor to each of said piping means; each of said pneumatic circuits further comprising: S* OS an electrovalve means disposed in the associated r. piping means; see S 20 a rotary coupling means mounted to the axle on which the associated tyre is mounted for coupling said piping means and said associated tyre in a manner to allow said pressurised air to flow therebetween; O a pressure sensor connected to a point on the

55.5 piping means intermediate said electrovalve means and said associated tyre, said pressure sensor adapted to generate electrical signal indicative of whether air pressure in "said associated tyre is higher or lower than said set pressure; and, 30 an electronic circuit responsive to said air- pressure indicative signal to cause the electrovalve means to open when and while the air-pressure in the associated *tyre is lower than said set pressure. 2. The apparatus of claim i, wherein said electronic circuit further includes a luminous indicator 9 which lights up in response to said electrical signal when the air-pressure in said associated tyre is lower than said set pressure. 3. The apparatus of claim 1 or 2, wherein said pressure sensor is coupled to a pressure gauge for indicating air-pressure in said associated tyre. 4. The apparatus according to any one of claims 1 to 3 farther including means for sensing pressure at the compressor outlet and means for maintaining said electrovalve closed in response to the sensed compressor pressure being less than the nominal compressor pressure. The apparatus of claim 1, wherein said pressure sensor further comprises: light emitting means and associated phototransistor, positioned so that light from said light ;emitting means can impinge on said phototransistor; *o an amplifier having an input connected to said ophototransistor, and an output for generating an active signal in response to the air-pressure of said associated ease 20 tyre being less than said set pressure; a driver transistor connected to said output from the amplifier and to said electrovalve means for energising 0.0. and opening said electrovalve means in respond- to said active signal; and, 25 a feedback circuit connected to said amplifier for introducing hysteresis in the operational characteristics of the amplifier. 6. The apparatus of claim 5, further including means for sensing pressure at the compressor outlet and a S 30 logic circuit connected to said electronic circuit, said logic circuit responsive to said compressor outlet pressure •sensing means for blocking said active signal from passing from the amplifier to the driver transistor to maintain 10 said electrovalve closed when the sensed compressor pressure is less than the nomin compressor pressure. 7. The apparatus according to any one of claims 1 to 6, further including manual switch means for turning off power to said electronic circuit, thereby rendering the apparatus inoperative and keeping said electrovalve closed. 8. The apparatus according to any one of claims 1 to 7, further comprising a check-valve connected between the associated tyres and rotary coupling means to prevent leakage of air from said tyre in the event that said associated piping means becomes ruptured or is disconnected from said rotary coupling means. 9. An apparatus substantially as described with reference to and as illustrated in the accompanying drawings. Dated this 16th day of April, 1993. COL-VEN S.A. By its Patent Attorneys: GRIFFITH HACK CO. 20 Fellows Institute of Patent Attorneys of Australia. 0 Sees S S* 5650 000355 0