EP1606127A1

EP1606127A1 - Air pressure control system and operation of air pump for vehicle tyres

Info

Publication number: EP1606127A1
Application number: EP04723885A
Authority: EP
Inventors: Sven A. Jansson; Karl-Johan Edlund
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-03-27
Filing date: 2004-03-26
Publication date: 2005-12-21
Also published as: WO2005007425A1; SE0300857D0; SE0300857L; SE526278C2

Abstract

A system for pressure control in one or more tyres on a vehicle wheel by means of a piston pump (1) connected to the tyre of the wheel. A magnet (8) attached next to the wheel attract an anchor (6), which is in connection with the pump piston (3) at every rotation when the wheel (13) with the pump (1) moves past the magnet (9), so that a compression stroke occurs. During the rest of the rotation of the wheel a spring device (14) returns the piston (3), so that it produces a suction stroke.

Description

Air pressure control system and operation of air pump for vehicle tyres.

Area of Invention.

The present invention is of a control system for the pressure in one or several vehicle wheels by means of a piston pump mounted on the wheel and connected to the tyre.

Background of Invention. It is well known that the air pressure of a vehicle tyre affects the friction between the tyre and the road surface. The hardness and evenness of the road surface is a factor in determining the optimal air pressure for running economy. In addition, the temperature of the environment and the humidity of the road surface are important as well as the presence of water, snow and ice. Road safety is in this context dependent on the tyre pressure. It has been found that incorrect air pressure has been a decisive contributing factor in many road accidents. A decisive reason why vehicles are run with an incorrect tyre pressure is that the pressure is difficult to check and regulate. One has to stop at a service station and read the pressure with a special pressure gauge and then adjust it, if necessary. It is usually recommended that this should be done every time you fill up the fuel tank, but this, of course, requires an extra effort; the car may have to be moved to the air ^' line and four tyres have to be checked. In between these adjustments, if they are done, checks are rarely carried out, even if the load of the vehicle and the condition of the road were to make such checking advisable. In recent years, therefore, a number of systems have been proposed for gauging the tyre pressure centrally in the car, even while running, which indicate the level of the pressure and show a warning signal when it is incorrect. Such systems are on the market and they have been made possible by advent of contactless or wireless transfer systems for signals, so-called blue tooth systems. However, one problem is that the tyre is on the rotating wheel and the signals have to be transferred to a stationary part of the vehicle. A further problem is the adjusting of the pressure of the rotating tyres. This can be done easily only when the vehicle has come to a standstill, and, of course, in addition, an air pump needs to be at hand. Normally, to do all this, one needs to go to a service station.

Status of Techniques.

There are systems in which the vehicle carries a compressor through which air is conducted to the tyres through rotating gaskets . One such system is Eaton Corp'' s central tyre pumping system Eur Publ Nr 0164916. Another is Hughes Aircraft Go's, patent publication Nr 0621144. In this case the pump unit with steering valves is placed in the wheel and no rotating couplings are needed for the air supply, but, instead, the electrical energy for the pump must be transferred by slip rings and brushes, which also applies to the gauging and steering signals. A way of solving this problem is to place the pump itself in the rotating wheel and thus operate the pump mechanically. These systems all involve mounting, on the wheel, a piston pump which is caused to move forwards and backwards through the contact that the outer end of the piston or the piston rod has with a stationary camdisc. In some cases, the piston may be disengaged and idle when the pump does not need to be in operation. Patent US 2391652 A is of an air pump which follows the rotation of the wheel and whose piston motion derives from a stationary camdisc next to it. The air pressure determines when a barring pin locks the motion of the piston. In patent DE 242502 there is a piston in contact with a "thumb disc", but by twisting an eccentrically carried roll it may be kept free from interference.

In patent DE 156469, similarly, the piston motion may be blocked by a barring pin. For the rest, this design is suitable only for wheels with spokes, for example bicycle wheels.

And in patent DE 4225103, which is also suitable for bicycle wheels, the piston motion is stopped by turning an arm into a groove in the piston rod.

In patent JP 11139118, which is especially suitable for mounting on lorry wheels, the piston is always in motion as soon as the wheel moves .

In these solution systems there is direct mechanical contact between the rotating pump and a stationary point next to the wheel, which causes wear and noise. In most of the cases where the piston can be' disengaged this is done by means of a relatively complicated mechanism. Some of the designs are not particularly suitable for mounting on car wheels.

Characteristics of Invention. The main aim of the present invention is to eliminate the drawbacks of the existing systems, which is achieved by the characteristics of our system listed in the patent claims in the following. A salient feature of the present invention is an air pump which is mounted on the vehicle wheel and follows its rotation. However, a particularly prominent feature of the invention is that an electro-magnet fixed next to the wheel attracts an anchor connected to the piston of the pump, so that every time the wheel and the pump rotate past the magnet a compression stroke occurs in the pump. The return power for the suction stroke is provided by a stainless spring. The advantage of "this particular type of power transfer is the absence of any mechanical link between the moving piston system and the stationary environment. This eliminates wear and noise. Another advantage is that it is possible to determine when the pump should deliver air by interrupting the electricity supply to the stationary coil. This can be done both manually and automatically with frequency-controlled sensors in the air system of the tyres.

Valves are placed in the wheel for pressure adjustment of the tyres. The valves receive an wireless operation impulse from a central unit, which also receives wireless signals from the temperature and pressure sensors of the tyres. The central unit also receives signals with information about the temperature and humidity of the environment. Incoming data are processed by computer programmes in the central unit, which controls the air pressure of the tyres and transmits the information to the driver. Thus the present invention provides a totally computerized control system of the tyre pressure while the vehicle is moving, which is possible to accomplish without any rotating air couplings or electric slip contacts.

Description of I den on . In the description of the present invention reference will be made to the following figures: Figure 1 shows a section of a vehicle wheel with the air pump mounted on the rim of the wheel. Figure 2 shows a side section of the same wheel in which only the parts vital to the functioning of the pump are indicated. Figure 3 shows a scheme of equipment needed for gauging and regulating tyre pressure. The air pump 1 consists of a cylinder 2 in which a piston 3 can move forwards and backwards. At one end of the cylinder 2 there is a lid 4 with the inlet and outlet valves commonly used in compressors, which are not described in detail here. The piston 3 is connected by means of a rod 5 to an anchor 6 of soft iron with good magnetic properties. The anchor 6,. which is part of a toroid with the same centre as the wheel rim, is partly enclosed by the pole shoes 7 of an electro-magnet 8 with a coil 9; and the pole shoes have a toroidal shape, so that the anchor 6 can move freely in the air gap between them. The piston rod 5 passes through the anchor 6 in the form of a pin 10, which is controlled by and moves in a casing 11. The pump cylinder 1 and the steering casing 11 are fixed to the wheel rim 13 with a bracket 12a. Between the cylinder 2 and the anchor 6 is placed a coil spring 14, which pushes the piston 3 towards the right, which produces a suction stroke. The wheel also contains a brake disc 15 straddled by the brake shoes 16, which are fixed to a stationary part of the wheel suspension by means of a bedplate. Similarly, another bedplate 18 is mounted in an area not occupied by the brake shoes 16. This bedplate 18 carries the core yoke of the electro-magnet already mentioned 8, mounted in such a way that there is the smallest possible air gap (s) to the pump anchor 6 when the wheel is in a certain position. In order to counteract the destabilizing power of the pump, a bracket 12b is fixed diametrically opposed to it, to which balancing weights can be attached. Additionally, valves and sensors for regulating the tyre pressure can be attached to the same bracket. We take it as understood that the electro-magnet can be replaced by a permanent magnet, but in such a system the pump will be constantly in operation, regardless of whether air is needed or not . The system operates as follows: Every time the wheel with the pump 1 sweeps past the poles 7 of the magnet, if its coil has the right voltage, they will attract the iron core 6 of the piston 3, so that the piston falls behind in the motion of the wheel (19, right in figure 2) , which means that the air is compressed in the cylinder 2 and is blown into the tyre or a volume accumulator. Once the pump 1 together with the wheel has moved past the stationary magnet 7, the attractional force on the anchor 6 of the piston is released and the spring 14 returns the piston 3 in a suction stroke to its initial position, after which the procedure is repeated when the pump 1 in the next rotation comes near the magnet coil 14.

The system shown in figure 3 of controlling and maintaining the tyre pressure functions as follows:

The details of the frame marked A are attached to the wheel and move together with it when it rotates, whereas the details within the B-area are fixed next to the wheel on the vehicle itself. The figure shows a wheel with two tyres 20,21 next to each other on the same axle, but the system can obviously be used for a wheel with only one tyre. The wheel must be equipped with a air accumulator 22, which can be filled with air from the outside through a valve 23 in the normal way at a service station. A safety valve 24, which is remote-controlled from the central unit C, limits the pressure and can also after starting centrifugally empty the volume accumulator of condensing water once the wheel is rotating. The pressure and temperature sensors 25, 26 in the tyres produce gauging signals, which are transformed into radio frequency signals, in their turned received by the receivers 27, 28 attached to a stationary part next to the wheel. The pressure in the accumulator 22 is gauged in the same way by a sensor 29, whose readings are likewise transmitted to a stationary receiver 30. The readings are passed on to a central unit C, from where they are further passed to the driver's position 31, where they show the pressure level or switch on warning lights. Readings of the temperature (t) and humidity (m) of the environment are also passed on to the central unit C from a sensor 32, placed on the outside of the vehicle close to the road. The central unit contains a computer programme which operates warning lights as well as regulates the tyre pressure. This procedure works as follows: When the pressure of one of the tyres is too low, a wireless open-signal is transmitted by a transmitter 33, 34 to a corresponding receiver in the wheel 35, 36 and further to the magnetic valve 37, 38, which opens and adds air from the volume accumulator 22. The opposite happens if the pressure is too high, but in this case a valve opens and let out air into the atmosphere. The central unit C may also contain a computer programme which redistributes the weight on the two tyres in the volume accumulator, if the wheel has two tyres. If the pressure in the accumulator 22 falls below a pre-programmed level, the central unit C sends a starting signal to the air pump by activating a contactor 39, so that the magnet coil of the pump 9 receives voltage (ϋl) , after which the pump starts working in the manner described above. In order to prevent the pump from working when not needed under the influence of remanence in the core and the pole shoes, the contactor, in rest position, may feed a lower voltage (U2) with the opposite polarity into the coil.

Since condensation water will gather in the air accumulator 22, a magnet valve 40 is also coupled to the safety valve connection 24, which gives open-impulses according to a timing programme in the computer centre C via the stationary transmitter 41 to the rotating receiver 42, which drains the accumulator of condensation water.

Claims

C L A M S .

1. A system for controlling the pressure in one or (two) more tyres on vehicle wheels with a piston pump (1) connected to the tyre, cbaracfc-e-r-izβd by the pump being a piston pump and an electromagnet (8) fixed next to the wheel attracting an anchor (6) connected to the pump piston (3) . A compression stroke occurs at every rotation when the wheel (13) and the pump (1) pass the electro-magnet (8), so that a compression stroke occurs while the piston (1) , during the rest of the wheel rotation, is returned to its initial position in a suction stroke by means of a spring coil device (14). The magnet is an electro-magnet (8) whose coil (9) receives voltage when the tyre (or tyres) (20, 21) needs increased pressure.

2. A system according to Claim 1, c-ha-raefce-ri-zed by the vehicle wheel (13) having an air accumulator (22) connected to the piston pump (1) and to the tyre (or tyres) (20, 21) via valves (37,38).

3. A system according to Claim 2, c-aracterized by the coil (9) of the electro-magnet being voltage-controlled according to impulses from a central unit by a computer programme which receives pressure readings for the accumulator (22) and the tyres (20, 21), radio-transmitted by sensors (25, 26, 29) in the rotating wheel to receivers (27, 28, 30) . The temperature and humidity of the environment are also gauged by a sensor (32), which gives impulses to the central unit which, in its turn, transmits ^λopen' and ^Λclose' signals via stationary transmitters (35, 36) to magnetic valves (37, 38) which rotate with the wheel and are placed in air ducts between the accumulator (22) and the tyres (20, 21) .

4. A system according to Claim 2 or 3, characterized by manual control of the pressure from the driver's seat (31), to which readings are also transmitted of the tyre pressure and the temperature and humidity of the environment.

5. A system according to one of Claims 1-4, when the wheel has at least two tyres, characterized by the pressure being adjustable from the driver's seat to different levels in the different tyres (20, 21) , in order to select which of the tyres is to be in contact with the road surface or in order to redistribute the pressure between the tyres and the road.

6. A system according to Claims 3-5, characterized by the accumulator (22) being connected to a magnetic drainage valve (40) which rotates with the wheel and which gives a wireless 'open' signal through a rotating receiver (42) from a stationary transmitter (41) and is thus able to empty the container (22) of condensation water either automatically at every start according to a programme in the central unit (C) or by manual impulses from the driver's seat (31).