DE29513754U1 - Machine damage detection device - Google Patents

Description

Device for detecting machine damage

The present invention relates to a device for detecting machine damage.

In practice, we often face the problem that machines seem to break down unexpectedly. If the manufacturer, service or maintenance company cannot react quickly or spare parts have to be procured at a time-consuming pace, days or weeks of production downtime and therefore high costs are threatened.

Often, however, unexpected failures are caused by parts that wear out too early, which can be due to assembly, quality or design errors. However, these errors are preceded by changes in the behavior of the machines. By detecting these changes, timely maintenance or repairs can be planned in the long term. This saves costs and stress, and increases customer confidence.

The noise of the machine is used to detect the changes, which changes when there are signs of wear or damage.

The present invention is based on the object of creating a device for detecting machine damage which detects damage very reliably and can be produced inexpensively.

This object is achieved according to the invention by a device having the features of claim 1.

Here, the vibrations and noises generated by a machine are recorded and digitized using a sensor. This data in the time domain is transferred by the computer into a Fourier spectrum and then converted into a power spectrum, which indicates the energy over the frequency axis. Since short-term changes in this spectrum do not represent machine damage that can be detected, several measurements are averaged. Only when specified limit values are exceeded for a long period of time (depending on the application, freely selectable from minutes to hours) will the device issue a warning message (bus connection, warning light, acoustic). Since only slowly developing damage should be detected, processing speeds do not play a major role, which contributes to the inexpensive production of the device. The signal received can also be analyzed and, if detailed knowledge of the machine is available, a damage analysis can be carried out.

An advantageous embodiment provides that the sensor is a microphone. This means that the sensor is very inexpensive, since microphones are mass-produced.' Dynamic microphones are advantageous here, since they are particularly suitable for recording vibrations in the frequency range of the application and replace expensive acceleration sensors.

A further embodiment provides that a multiplexer is arranged in front of the measuring amplifier, which allows

to evaluate several sensors serially one after the other, especially in complex machines with multiple drives.

A further embodiment provides that the downstream measuring amplifier is adjustable in bandwidth and gain, so that it can be automatically and optimally adapted to the respective measuring task, i.e. the signal to be analyzed. This is advantageously done automatically by the downstream computer.

Digitization of the data enables an inexpensive transformation of the time data into the frequency domain, without complex analog circuits.

Another embodiment provides that the computer is equipped with a real-time clock so that analysis data can be stored with time recording.

Another embodiment provides that the computer is equipped with an interface that allows the data to be transferred to a host computer in which more detailed evaluations and analyses can be carried out.

Another embodiment provides that the computer is supplied via the interface with a comparison spectrum that was obtained through detailed measurements of other devices.

The invention is explained in more detail below with reference to the drawing of an embodiment.

Show it:

Fig.l a schematic diagram of a device according to the invention

Fig.2 is a block diagram of the device according to Fig.l and

Fig.3 a diagram of a frequency spectrum and an alarm threshold

Fig.l shows a device 10 for detecting damage to a machine not shown, such as an electric motor with a gearbox or the like.

The device 10 comprises a sensor 12 in the form of a microphone, which is either permanently attached (screwed, glued) to the machine to be monitored or is removably attached using, for example, a magnetic holder, a measuring amplifier 14 which amplifies the analog sensor signals, a converter 16 which digitizes the amplified sensor signals and a computer 18 connected to it which processes the digital signals.

The computer 18 forms a transformation unit 20, a storage unit 22, a comparison unit 24 and a communication unit 30, which can process a wide variety of bus protocols. The real-time clock is also connected

26 and an optical, electrical (digital output or relay) or acoustic alarm unit 12.

The entire device 10 is housed in a ""housing, which, depending on the design, can be miniaturized and integrated into the sensor, battery-operated, portable or designed in a housing for control cabinets.

Claims (11)

Protection claims 1. Device for detecting machine damage, with a sensor (12) for recording vibrations of a machine to be monitored, a processing unit (20) for repeatedly transforming the time-variable sensor signals into a frequency spectrum, a storage unit (22) for storing a predeterminable spectrum, a comparison unit (24) for comparing a current spectrum output by the processing unit (20) with the stored one and for outputting an alarm signal if the current spectrum deviates from the stored one in a predeterminable manner. 2. Device according to claim 1, characterized in that a measuring amplifier (14) is connected downstream of the sensor (12). 3. Device according to claim 1 or 2, characterized in that a measuring amplifier (14) is connected downstream of the sensor (1·2). 4. Device according to claim 3, characterized in that the processing unit (20) is connected to the measuring amplifier (14) in such a way that the gain of the measuring amplifier (14) is controllable or adjustable. 5. Device according to one of the preceding claims, characterized in that a converter (16) is provided for converting the analog, optionally amplified sensor signals into digital signals. 6. Device according to one of the preceding claims, characterized in that the processing unit (20) is designed so that an averaged frequency spectrum can be output to the comparison unit (24) and/or the storage unit (22). 7. Device according to one of the preceding claims, characterized in that the storage unit (22) is designed so that in a learning mode an averaged frequency spectrum of the processing unit (20) or a spectrum derived therefrom, smoothed and increased by a predeterminable amount or a spectrum determined by an external measurement can be stored. 8. Device according to one of the preceding claims, characterized in that the processing unit (20), the storage unit (22) and the comparison unit (24) are formed by a digital computer (18). 9.Device according to claim 98, characterized in that the computer (18) is connected to the time base (2 6). 10. Device according to one of the preceding claims, characterized in that all components of the device (10), either including the sensor (12) or excluding the sensor (12), are housed in a housing. 11. Device according to one of the preceding claims, characterized in that the device comprises a digital interface (30) for connection to a network or computer for transmission of the current or stored data.