Monitoring for railway vehicles is an increasing area of interest. Especially the bogie of cars of such vehicles is important to monitor, since some parts such as wheels, wheel axles and wheel bearings are bearing heavy loads. The condition of these parts is crucial for passenger safety and comfort. The maintenance and overhaul of these parts is expensive.

The publication WO 98/44472 discloses a unidirectional telemetry system that can be suitable for condition monitoring of wheel bearings on a railway car. The system comprises a plurality of beacons that each transmits data from a sensor to a monitoring receiver. The objects of the system are to provide a robust, low cost and low energy monitoring system.

If vibration data is correctly analyzed it can give a lot of information of the vehicle status and early indications of faults in bearings, axles, wheels and suspension. To make a thorough analysis a lot of data is required. To collect, analyze and transfer expansive vibration data demand great capacity of the system and also demand electrical power. For surveillance of vehicle data a more complex system might be required, with the possibility to communicate with the sensors and with some processing capacity in the vicinity of the sensors.

It is not desirable to use batteries as a power source for equipment on a rail vehicle because of the need to check and replace them, and batteries are not reliable enough to be used in safety related functions.

SUMMARY OF THE INVENTION The object of this invention is to find a reliable and maintenance free monitoring system for railway vehicles.

The present invention relates to a system comprising a sensor unit, arranged at the bogie of the vehicle, in the vicinity of the wheel axle and a information processing arrangement, arranged at a car body of the vehicle for processing said information.

The sensor unit comprises sensor members for sensing parameters; communication means for transmitting the information obtained by said member further for processing and energy generating devise for supplying the sensors and the communication means with electrical energy. The information is transmitted wirelessly and electrical power is supplied by generating energy from the rotation of the wheel axle close to the sensor members and communication means. The sensor unit comprises means for performing some processing of the information obtained by said sensor members before said transmitting thereof by means of the communication means. This is particularly important for safety reasons, where time is critical. The information processing before further transmission can thus consist of evaluation of certain parameters, which enables, when necessary, taking measures for avoiding emergencies.

Furthermore, according to another preferred embodiment of the invention, said means for performing some information processing comprises means adapted to carry out analog-to-digital conversion of information from the sensor member. This can for instance be required for the transmission via said wireless connection or for the processing in said arrangement. According to other preferred embodiments of the invention, said means for performing some information processing comprises means adapted to carry out pulse-frequency modulation and/or means adapted to carry out pulse-width modulation of information from the sensor member. Arrangement of such means provides for a secure transmission of information, being highly resistant to noise and interference.

The provision of information processing arrangements can include one or several arrangements in one or several car bodies of said vehicle. According to one embodiment of the invention the monitoring system comprises one processing arrangement per bogie arranged in the car body of said vehicle, making the cars independent of each other as to information processing and interchangeable between different vehicles. According to another embodiment of the invention one processing arrangement is adapted to alone process information from a plurality of bogies enabling comparison between different parameters and between different bogies. Furthermore, according to another embodiment of the invention, one processing arrangement is adapted to alone process information from all bogies of a train, which allows for a provision of only one arrangement for example placed in a locomotive where ail processing can be performed simultaneously for a number of cars.

According to another embodiment of the invention said communication means is adapted to transmit said information to a plurality of information processing arrangements, which is needed when several arrangements with different tasks are provided in a car body. This also enables evaluation in one car body of information obtained from bogies of several car bodies.

The wireless connection between said sensor member on the bogie and said information processing arrangement in the car body could of course be arranged in any suitable manner. One possible way, according to a preferred embodiment of the invention, is that said communication means comprises radio interface and radio modem enabling use of standard components with known functionality and reliability.

The information that is communicated from the bogie to an information processing arrangement describes the state of said vehicle by means of a plurality of parameters. For sensing these parameters there may be provided a plurality of sensor members, preferably on the bogie, and according to the invention said members comprise for example vibration, velocity, acceleration and temperature sensing means. This information can then be used for various purposes such as safety control, comfort control, condition based maintenance etc.

According to another preferred embodiment of the invention the monitoring device comprises an information processing arrangement located in the driver's compartment of the vehicle enabling continuous supervision of the current state of the vehicle, in form of the information obtained by said sensor members, for safety and accurate driving.

Although thorough and correct processing of the information obtained by said sensor members can be done in the car body, further processing in a remote arrangement may be of interest, e. g. for increased safety, maintenance planning and traffic control.

Therefore, according to another embodiment of the present invention, said information processing arrangement in the car body has a communication member comprising a wireless connection to a wide area network and being adapted to transmit the processed information through the wireless connection for enabling further remote information processing via an arrangement connected to the network.

According to another embodiment of the invention the monitoring device comprises one information processing arrangement in the car body adapted to alone provide all information to be transmitted through said wide area network. In this way all in- formation can be transmitted at the same time in one single transmission, one positive effect is a decrease of the total amount of transmissions saving bandwidth.

For enabling this one transmission of all information at the same time, the different processing arrangements, if more than one, advisably communicate with each other according to another embodiment of the invention.

According to another embodiment of the invention said communication member is adapted to transmit the processed information via a wide area network according to the digital standard Global System of Mobile communications (GSM). This provides for a simple arrangement of the communication since standard components can be used, which recently have become less expensive. Using a known standard also secures a reliable communication. According to another embodiment of the invention said communication member is adapted to utilise the Short Message Service (SMS) of GSM for information transmission, which further simplifies the communication procedure.

The power supply comprise a polarised member is arranged at a wheel axle, ena- bling placing of sensing means for supervision in the vicinity of the wheel bearing.

According to another embodiment said polarised member is arranged inside a wheel bearing box, which facilitates attachment of said member and provides a location safe from unnecessary wear avoiding maintenance or exchange thereof. This also means that the polarised member is not in the way of other components and it does not require any extra space. Said polarised member is, according to another preferred embodiment of the invention, arranged at the end of said wheel axle, which provides for a simple arrangement thereof.

The power supply provides electricity when the vehicle is in motion and the wheel axle is rotating. If continuous information is needed, also from standstill, the power supply should also include an accumulator or other storing means.

According to another embodiment of the invention the number of poles on said polarised member is arranged as to induce current in a pre-determined frequency interval when rotating, which enables adjustment to frequency requirements of the equipment to which the current is supplied. Furthermore, the vast majority of commercially available electronic equipment requires a supply of current with a substantially constant frequency and to satisfy this requirement, according to another embodiment of the invention, the device comprises frequency conversion means for enabling supply of current with a certain frequency to said equipment irrespective of the rotation speed of said polarised member. Depending on the nature of said electronic equipment direct current could also be desired, why the device comprises rectifying means for enabling supply of direct current to said electrical equipment according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a block diagram of the monitoring system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The monitoring system comprise sensor units (1) placed in the vicinity of the end of a wheel axle, and a processing arrangement (2) placed in a vehicle car body. A

wireless connection transfer sensor data from the sensor unit (1) to the processing arrangement (2). The processing arrangement analyses sensor data to infer the present condition of components. The status information is forwarded to the vehicle control system (8) but could also be forwarded, either directly from the sensor unit or from the processing arrangement, via a wireless connection to a wide area network.

The sensor unit comprises sensors for sensing vibration, velocity, acceleration and temperature. The sensors are placed in the vicinity of the end of the wheel axle. The sensor unit comprises means for some processing (5) of sensor data, which can mean evaluating parameters, encoding information, performing calculations etc. The sensor unit also includes communication means (6) comprising e. g. a radio modem and radio interface. The power supply (4) provides the sensors (3), the means for some processing (5) and the communication means (6) with electrical energy. The energy is generated from the rotation of the wheel axle. A polarised member (not shown) is arranged at the wheel axle thereby inducing current in an armature coil.

The invention is of course not in any way restricted to the preferred embodiments described above, but many possibilities to modifications thereof would be apparent to a person skilled in the art without departing from the scope of the claims.

The claim definition"information"is to be given a broad sense, and it also comprises the case of for instance first sensing information about the velocity of the vehicle and vibration of a wheel of the bogie, then calculating a value of a parameter indicating the condition of the bearing of said wheel and finally transmitting said value as "information".