TECHNICAL FIELD The present invention relates to a detection device for detecting brake pad wear of an electromagnetic brake. Moreover, the present invention also relates to an elevator comprising the same detection device.

BACKGROUND

With the economic and social development in our country and constant emerging of high floor buildings, elevators are gradually popularized. While the elevator brings convenience for users, its potential security problems also are gradually paid much attention. Elevator brakes play an important role in the elevator security protection, of which the effective part is brake pads (brake blocks).Wear of brake pads in the long run will result in greater braking noise, insufficient braking force will lead to longer stopping distance, unreliable brake and so on.

About the elevator brake wear, the brake torque detection is generally used to indirectly reflect the state of the brake pad wear, for example, a patent entitled "an elevator brake torque detection method concerns detecting the braking force by automatically detecting a stopping distance of the car in the starting and braking state, but the braking distance is influenced by many factors, easy to false alarm, etc. in this technical solution. Additionally, a patent entitled "a method for implementing brake force detection of motor" relates to detecting the braking force by directly detecting the rotation of the motor in the braking state, the result is reliable, but it needs maintenance personnel to test on-site regularly, thus it has high cost but low automation degree.

There are many literatures about the wear detection of automobile brake pads, generally divided into two kinds: one is to embed sensors in the brake pad, such as the one involved in a patent entitled "a brake pad capable of detecting and preventing wear"; the other is to use fiber optic sensors to detect the thickness of brake pads directly, such as the technology in "a technique of monitoring wear of brake conditions by optical fiber sensing"; however, these methods have the defection of complex process and high cost. The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. SUMMARY

Aiming to solve the above one or more problems existing in the conventional elevator manufacturing field, the present invention proposes a low cost detection device for automatically detecting brake pad wear of an electromagnetic brake.

The present invention relates to a detection device for detecting brake pad wear of an electromagnetic brake according to claim I. In particular the brake comprising a brake wheel, a moving block, a static block, and a brake pad arranged between the moving block and the brake wheel, a gap existing between the moving block and the static block, wherein the detection device comprises an electromagnetic displacement induction unit and an induction block; the induction block is arranged on one of the blocks; the electromagnetic displacement induction unit is arranged on the other one of the blocks, and the electromagnetic displacement induction unit and the induction block are arranged to face each other; During use the the electromagnetic displacement induction unit senses the gap change between the moving block and the static block, and generates an alarm signal when the gap change value is greater than a predetermined value. Preferably, the detection device further can comprise an alarm signal output unit, a timer unit is connected in series between the electromagnetic displacement induction unit and the alarm signal output unit; the timer unit receives alarm signals from the electromagnetic displacement induction unit continuously for a predetermined time period, then sends the alarm signals to the alarm signal output unit. Instead of a timer any other kind of filter may be used, in particular a low pass filter.

Preferably, the timer unit can comprise a reset switch which is electrically connected with a signal output terminal of a processor of the electromagnetic displacement induction unit, and when the processor has no signal output, the reset switch is used for resetting a timer of the timer unit.

Preferably, a signal control switch can be connected in series between the electromagnetic displacement induction unit and the timer unit, the signal control switch is electrically connected with a brake signal or standby signal input terminal of the electromagnetic brake, and switches off when the electromagnetic brake works. Preferably, the electromagnetic displacement induction unit can output a linear, non-linear or step type signal.

Preferably, the electromagnetic displacement induction unit can be arranged on the moving block via a first bracket; and the induction block can be arranged on the static block via a second bracket.

Preferably, the electromagnetic displacement induction unit can comprise a hall induction unit. Preferably, the induction block can comprise an iron or a magnet.

More preferably, the hall induction unit can comprise a hall displacement sensor and/or the alarm signal output unit comprises an alarm lamp or an alarm horn. The present invention further relates to an elevator comprising the detection device for detecting brake pad wear of an electromagnetic brake as mentioned above.

The present invention adopts the above technical solutions, which generates the following beneficial effects:

The brake pad wear state is detected by using a hall displacement sensor, in order to replace the brake timely, and avoid the security incidents caused by lacking of braking force. Moreover, the brake is only detected when it's power off, which greatly improves the detection accuracy, and also prevents the elevator accidents from occurring due to signals detected during the elevator operation;

Confirming the signal availability by the timer can filter false alarm caused by random interference, such as field impact, vibration, temperature fluctuations, the brake remanence, and so on;

The bracket type installation does not need to change the internal structure of the brake, which is convenient and quick, easy to be popularized;

In addition, the hall displacement sensors and related modules are widely used and of low cost. BRIEF DESCRIPTION OF THE DRAWINGS

More detailed explanation will be made to the exemplary examples of the present invention in conjunction with appended drawings hereinafter. For clarity, like parts in different drawings are designated by like reference numbers. It should be understood that the appended drawings only serve to illustrate, not necessarily to scale. In these figures:

Fig. 1 is a structural schematic diagram of a detection device for detecting brake pad wear of an electromagnetic brake of the present invention;

Fig. 2 is a structural block diagram of an electromagnetic displacement induction unit of the present invention;

Fig. 3 is a working principle diagram of an electromagnetic displacement induction unit comprising hall elements of the present invention; Fig. 4 is a structural schematic diagram of the detection device for detecting brake pad wear of the present invention prior to brake pad wear; and

Fig. 5 is a structural schematic diagram of the detection device for detecting brake pad wear of the present invention after brake pad wear.

DETAILED DESCRIPTION Hereinafter, detailed description will be made to the exemplary embodiments of the present invention in conjunction with the accompanying drawings.

As shown in Fig. 1, a detection device for detecting brake pad wear of an electromagnetic brake of the present invention comprises: an electromagnetic displacement induction unit 1, a first bracket 2, an induction block 3, a second bracket 4, a signal control switch 5, a timer unit 6, an alarm signal output unit 7, a static block 8, a moving block 9, a brake pad 10 arranged between the moving block and a brake wheel 11. Wherein, a certain gap exists between the moving block 9 and the static block 8, the electromagnetic displacement induction unit 1 is installed on the moving block 9 of the brake via the first bracket 2, the induction block 3 is installed on the static block 8 of the brake via the second bracket 4, and the electromagnetic displacement induction unit 1 comprises a hall induction unit and a processor. The hall induction unit and the induction block 3 are arranged to face each other, thus it does not need to change the internal structure of the brake, and installation is convenient. In addition, the first bracket 2 and the second bracket 4 is an L-shape metal bracket respectively, which structure is stable and light, reducing cost.

The alarm signal output unit 7 is electrically connected with a signal output terminal of the processor, the hall induction unit of the electromagnetic displacement induction unit 1 can sense the gap change between the moving block 9 and the static block 8. When the gap change value is less than the predetermined value set in the processor, i.e. the gap value does not change much or has no change, as shown in Fig. 4, which shows that the brake pad is not worn or wear is not serious, the alarm signal is not output (or OV low level is output); when the gap change value is greater than the predetermined value set in the processor, i.e. the gap changes much and the brake pad is worn seriously, as shown in Fig. 5, the processor sends the alarm signal to the alarm signal output unit 7, such that the alarm signal output unit 7 outputs the alarm information. That is, when the brake pad 10 is worn and become thin, since the static block 8 keeps still, the displacement between the induction block 3 installed on the first bracket 2 and the electromagnetic displacement induction unit 1 becomes large. When the wear reaches the predetermined value set in the processor, the electromagnetic displacement induction unit 1 outputs signal inversion via the processor, which may send the alarm signal (for example, 24V piezoelectric signal) to the alarm signal output unit 7 directly or indirectly via the following timer unit 6. As shown in Fig. 2, the electromagnetic displacement induction unit 1 of the present invention can comprise a hall induction unit 13 which may output linear, non-linear or step type signals and a processor 14 which may comprise a signal processing unit and a storing unit. The signal processing unit can be single chip, DSP or general purpose processor, and it can be integrated with the storing unit and also can be arranged separately. The storing unit can be used to store related information, for example, the predetermined value used to be compared with the above gap change, and the storing unit can be: ROM, PROM, EPROM, EEPROM or flash memory, and so on.

Preferably, the electromagnetic displacement induction unit 1 comprises a hall induction unit. The induction block 3 comprises an iron or a magnet. Here the induction block can be an iron also can be a magnet because the hall means as a preferred embodiment of the induction unit can be embedded or not embedded with a magnet. When it is embedded with a magnet, the induction mean can be an iron, and when it is not embedded with a magnet, the induction mean is a magnet. Below the hall mean not embedded with a magnet is taken as an example, said induction mean is a magnet. The processor 14 firstly self-learns according to relative location of the electromagnetic displacement induction unit 1 and the magnet, and then initializes inversion thresholds of output signal according the preset amount of wear.

As shown in Fig. 3, the basic working principle of the hall displacement sensor is: when the hall induction unit (hall sensor) of the electromagnetic displacement induction unit 1 is disposed in the magnetic field B of Z+ direction, if current A passes in the Y direction, hall voltage u may be generated in the X direction, whose size is proportional to the magnetic field intensity B. When the magnetic field B is provided by a magnet, the displacement between the magnet and the hall mean would result in change of the magnetic field intensity B, which may be further represented by the hall voltage. Therefore, by use of such hall displacement sensor, it can accurately measure the displacement of an object, and it has low cost and mature technology.

Again referring to Fig. 1, a timer unit 6 can be connected in series between the electromagnetic displacement induction unit 1 and the alarm signal output unit 7. After the timer unit 6 continuously receives the alarm information from the processor for a certain period of time, then the alarm information is sent to the alarm signal output unit 7. That is, only after the wear signal output by the electromagnetic displacement induction unit 1 lasts for a certain period of time (the time period preset in the timer unit 6), then the confirmed wear alarm signal is output to the elevator control system. It can filter false alarm caused by random interference, such as field impact, vibration, temperature fluctuations, the brake remanence, and so on. Preferably, the predetermined time period can be 20 seconds. For the purpose of the invention the any other suitably configured low pass filter can be used as well.

In addition, the timer unit 6 further comprises a reset switch RST that is electrically connected with a signal output terminal of the processor, and the reset switch automatically reset the timer of the timer unit 6 when the processor has no signal output.

A signal control switch 5 is connected in series between the electromagnetic displacement induction unit 1 and the timer unit 6, the signal control switch is electrically connected with a brake signal or standby signal input terminal of the electromagnetic brake. When the electromagnetic brake works, the signal control switch 5 switches off, and when the electromagnetic brake does not work, the signal control switch 5 switches on, to start detecting the wear situation of the brake pad. Only when the signal control switch 5 switches on, i.e. the brake is powered off, then it can be detected, to prevent the self magnetic field of the brake to interfere the hall sensor when the brake is powered on, simultaneously to avoid users to be trapped due to alarm of brake pad wear.

The alarm signal output unit 7 can comprise an alarm lamp or an alarm horn, which outputs the alarm information in the form of lighting or sound. Additionally, the output unit also can be connected with outputting devices such as a display or a printer or the like, so as to output the wear situation in the form of image or document. In addition, the present invention also relates to an elevator (not shown), comprising the above said detection device for detecting brake pad wear of an electromagnetic brake. Since other structures of said elevator here are the same or similar as structures of the elevators in the prior art, they are not described in detail hereinafter. The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain certain principles of the invention and their practical application, to enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

list of reference signs

1 electromagnetic displacement induction unit

2 first bracket

3 induction block

4 second bracket

5 signal control switch

6 timer unit

7 signal output unit

8 static block

9 moving block

10 brake pad

11 brake wheel

13 hall induction unit

14 processor