JPH07181254A - Safety system of construction machine - Google Patents

Abstract

PURPOSE:To prevent a failure to detect a distance due to battery runout by modulating a reception signal according to the output of a phase shifter which gives a specific phase shift according to a signal indicating a specific discharge state which is detected by a discharge state detection circuit of a battery. CONSTITUTION:A transceiver 10 is mounted to the rear of a hydraulic shovel and a transponder 20 is mounted to the helmet of a worker. The transceiver 10 is provided with an operation circuit for measuring the distance to the transponder 20 and then sends the calculated distance to the controller of an operation stand. The transponder 20 is provided with a switching circuit 25a for selecting either a phase shifter 25, the output of the phase shifter 25, or that of an oscillation circuit 22 and then transmitting it to a mixing circuit 23, a discharge state detection circuit 29 etc. The detection circuit 29 is constituted by a comparator and generates a detection pulse L when the voltage of a battery 40 goes below a preset value. A communication control circuit 28 receives a pulse L from the detection circuit 29 and turns on or off the circuit 25a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety system for a construction machine, and more particularly, to a transponder type microwave distance sensor mounted on a construction machine as a safety system so that the operation of a transponder on the other side does not stop. , A safety system capable of ensuring higher safety by monitoring the remaining amount of the built-in battery.

[0002]

2. Description of the Related Art At construction sites, road pavement sites, civil engineering work sites, etc., there are many work modes in which construction machines and workers cross each other. In addition, depending on the location, general people also visit or carry in and carry out various machines used in association with work, and also obstacles. If these workers, ordinary people, obstacles, etc. are in a construction method or in a direction that obstructs the field of view of a driver of a work vehicle or the like, the risk of an accident is extremely high. Therefore,
Therefore, ensuring safety is important. Therefore, various sensors for detecting the position of the other party have been studied, and one of them is a construction machine equipped with a distance sensor using a transponder type microwave.

However, this type of microwave distance sensor mounted on a construction machine is in full-scale application and practical use. On the other hand, taking a hydraulic excavator at a construction site as an example, an operator who operates the hydraulic excavator and a worker who performs auxiliary work around the machine jointly perform construction work. In such a case, it is necessary to secure sufficient safety for work by using the microwave distance sensor. That is, in a hydraulic excavator, a microwave transceiver (transceiver) is mounted on the side of the excavator, and the worker wears the transponder by attaching it to a helmet or the like. Transmission and reception are performed between these, and the position of the worker is monitored.
This informs the operator of the hydraulic excavator that the operator has approached the dangerous area of the hydraulic excavator, and automatically stops the machine as necessary in order to prevent a contact accident between the machine and the operator.

[0004]

When a distance sensor of this type is mounted on a construction machine, the transceiver can be mounted on the construction machine side, so that the operating power can be obtained from the construction machine. On the other hand, the transponder worn and used by the worker currently has to rely on the battery for the electric power because of the wearing relation. At this time, if the transponder battery is exhausted, the distance cannot be detected as a matter of course. Therefore, the safety system described above does not work well. This is because when the distance to the other party cannot be detected, the transceiver side cannot determine whether the battery is dead or the operator is outside the detection range beyond the monitoring range.

[0005] In order to avoid such a thing, in order to inform the operator that the transponder battery is exhausted, a transponder is provided with a display device for the remaining amount, an alarm lamp or a meter is provided. It is to attach. However, with such a display, when the battery runs out during the work, the worker may not be aware that he is focusing on the work. In addition, the method of generating an alarm sound when the remaining amount is low may not be understood by the ambient noise. In consideration of such a situation, in the method of detecting the battery consumption or the battery remaining amount as described above,
We cannot ensure sufficient safety. An object of the present invention is to solve such a problem of the prior art, and to make it possible for the construction machine side to know the remaining amount of the battery of the transponder to prevent the distance detection from being impossible due to the dead battery. It is to provide a safety system for construction machinery that ensures higher safety.

[0006]

The features of the safety system for a construction machine of the present invention for achieving the above object are as follows.
A transponder sends a power to the battery, a first detection circuit for detecting the discharge state of the battery, and a predetermined transmission in response to a signal indicating the predetermined discharge state of the battery detected by the first detection circuit. A phase shifter that gives a predetermined phase shift to a signal, and a signal that is modulated by the output of this phase shifter and transmitted to the receiver side, and the receiver detects the predetermined phase shift. By detecting the signal indicating the predetermined discharge state from the signal transmitted from the transponder, the change in the phase given by the phase shifter is excluded to detect the rate of change in the phase of the predetermined signal. The distance is calculated.

[0007]

In this way, the transponder is provided with the function of detecting the remaining battery level (battery discharge state) of the transponder,
Since the detection data of the battery remaining amount is carried on the received transmission wave and transmitted to the transceiver side, it is possible to obtain the battery remaining amount information on the transceiver side. Therefore,
The construction machine side equipped with a transceiver can detect the dead battery information of the transponder. As a result, the operator who operates the construction machine can determine whether the battery is dead or the transponder side is far away. Further, by doing so, it is possible to take safety measures for running out of battery, such as issuing an alarm to the worker of the transponder running out of battery.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system configuration diagram of a microwave distance sensor mounted on a construction machine to which a safety system for a construction machine according to the present invention is applied, and FIG. 2 is an explanation of a relation between a transceiver and a transponder of the construction machine. 3, FIG. 3 is an explanatory view of transmission / reception timing, FIG. 4 is an explanatory view of transmission data, FIG. 5 is an explanatory view of a display state of a liquid crystal display panel of a driver's cab, and FIG. It is a flowchart of a display process. As shown in FIG. 2, the transceiver 10 is attached to the rear portion of the hydraulic excavator 1, while the transponder 20 is attached to the helmet of the worker 2.
The transceiver 10 has a distance D0 from the transponder 20.
It has an arithmetic circuit for measuring and sends the calculated distance D0 to the controller 4 of the cab 3. The control device 4 compares the distance D0 with a predetermined reference value, and when the transponder 20 (worker) is approaching a predetermined distance or more, an alarm device on the operator's cab 3 of the hydraulic excavator 1 where the operator is located. To display a danger on the display provided on the cab 3. Furthermore, here, the operator is notified when the battery built in the transponder 20 is in a depleted state, that is, a so-called dead state.

As shown in FIG. 1, the transceiver 10 is provided with a transmitting antenna 10a and a receiving antenna 10b, and a frequency control oscillator (VCO) 12 has a frequency within a predetermined frequency range according to the passage of time. A signal of a so-called swept frequency that sequentially increases or decreases by (here, microwave) is generated, sent to the transmission circuit 13, the microwave of the microwave is transmitted from the transmission antenna 10a, and the same is performed by the reception antenna 10b. Receiving microwave signals. The radio wave from the transceiver 10 is received by the antenna 20a of the transponder 20, and the radio wave signal that has entered this is amplified by the receiving circuit 21 and is then sent to the switching circuit 2a.
The output of the oscillation circuit 22 of 100 kHz supplied via 5a is mixed with the output of the mixing circuit 23 and transmitted to the transmission circuit 2.
Then, the signal is transmitted from the antenna 20b to the transceiver 10 via No.4.

The radio signal received by the receiving antenna 10b of the transceiver 10 is amplified by the receiving circuit 14 and mixed with the signal of the VCO 12 by the mixing circuit 15, and the bandpass filter (BP) having a center frequency of 100 kHz is used.
It is input to the phase difference detection circuit 18 via F) 16. The phase difference detection circuit 18 receives the reference signal of 100 kHz from the oscillation circuit 17 of 100 kHz at one input, and the phase of this signal is compared with the signal passed through the BPF 16.

The phase difference G detected by the phase difference detection circuit 18
Is added to the phase change amount detection circuit 19, and the change amount (slope) of the phase difference G is detected here. This amount of change, in other words, the slope of the phase difference G is the transponder 20.
And the distance D0. This slope is a function of the current sweep frequency of the VCO 12 and the sweep frequency when it is transmitted, and corresponds to the round-trip propagation time of the microwave to the transponder 20. The details are described in International Patent Publication No. 63-501981. Therefore, the output of the phase change amount detection circuit 19 is sent to the distance calculation means 30. Here, the distance D0 between the transceiver 10 and the transponder 20 is calculated. The calculated distance D0 is applied to the communication control circuit 31 and is sent to the microprocessor (MPU) 32 mounted on the control device 4 via the communication control circuit 31.

The triangular generator circuit 11 generates a triangular wave control voltage for controlling the oscillation frequency of the VCO 12. As shown in FIG. 3A, the communication control circuit 31 drives intermittently to drive the triangular generation circuit 11 for a period T1 and then stop it for a period T2. The phase change amount detection circuit 19 and the distance calculation means 30 are also driven for a period T1 by a drive signal from the communication control circuit 31, and operate during this drive period, and the same figure (b).
Measure the distance as shown in. In addition, the communication control circuit 31 controls the entire transceiver 10.

As a result, the frequency generated from the VCO 12 is, as shown in FIG.
A transmission wave that increases from the frequency f1 to the frequency fm and decreases is generated, and the frequency of the VCO 12 is locked at a constant frequency f0 during the intermittent period T2. The transponder 20 transmits data indicating the discharge state of the battery to the transceiver 10 during the intermittent period T2 of the frequency f0. Further, as will be described later, communication from the transceiver 10 to the transponder 20 may be performed during this intermittent period T2. The operation of oscillating the frequency f0 of the VCO 12 is performed at the timing after the communication control circuit 31 stops the operation of the triangular wave generation circuit 11. At this time, the VCO 12 is supplied with a constant voltage from the communication control circuit 31, so that the oscillation frequency f0 is maintained.

The transponder 20 receives the output of the oscillation circuit 22 of 100 kHz, a 180 ° phase shifter 25, and selects either the output of the phase shifter 25 or the output of the oscillation circuit 22 and sends it to the mixing circuit 23. Switching circuit 25a,
Demodulation circuit 26, intermittent period detection circuit 27, communication control circuit 2
8, a detection circuit 29 for detecting the discharged state (or charged state) of the battery, and a battery 40. The 180 ° phase shifter 25 sends the output of the 100 kHz oscillation circuit 22 to the mixing circuit 23 with a 180 ° phase delay. The demodulation circuit 26 demodulates (for example, detects by FM detection) the voltage signal of the triangular wave generation circuit 11 from the received signal. The intermittent period detection circuit 27 detects the intermittent period T2 from the signal demodulated by the demodulation circuit 26 and generates a pulse P having a width corresponding to the intermittent period T2 (see FIG. 3 (c)).

The communication control circuit 28 includes an intermittent period detection circuit 2
During the period in which the pulse P corresponding to the intermittent period T2 after receiving the detection pulse P of 7 is at the HIGH level ("H"), the output of the phase shifter 25 and the oscillation circuit 22 of the switching circuit 25a are switched according to the transmission data. Switching drive between output and. Further, while the pulse P is at the LOW level, the switching circuit 25a is set to the side that selects the output of the oscillation circuit 22 of 100 kHz.
The detection circuit 29 is composed of a comparator and is a battery 40.
The detection pulse L is generated when the voltage of 1 drops below a predetermined value. Here, the predetermined value is that the transponder 20 transmits the transmission signal to the transceiver 1
If the limit value of the electric power to be sent to 0 or a value with some margin, for example, 1.2V for the voltage of the drive battery, it corresponds to a voltage value of 0.9V.

When the communication control circuit 28 receives the detection pulse L from the detection circuit 29, it turns ON the switching circuit 25a.
Drive OFF. Therefore, the output signal of the 180 ° phase shifter 25 and the output signal of the oscillating circuit 22 are mixed with the signal C of the received radio wave by the mixing circuit 23 to receive the received signal C.
Is used as a carrier wave for amplitude modulation. It is transmitted to the transceiver 10 via the transmission circuit 24 and the transmission antenna 20b as microwave radio waves. The switching circuit 25a is controlled by the communication control circuit 28 so that, for example, the transmission bit is "1".
At the time of, the output signal of the 180 ° phase shifter 25 is switched to the side to select, and when the transmission bit is "0", the output signal of the oscillation circuit 22 is switched to the side to be selected. This is the intermittent period T2
Do in between. As a result, the carrier wave is amplitude-modulated by the signals of 100 kHz whose phases are different by 180 °. As shown in FIG. 4C, the transmission data at this time is, as a transmission start bit, for example, the 8-bit all "1" bit data STB followed by the identification code I of the transponder 20.
Data of a control signal to which D is added is generated as a serial pulse D, and this is sent to the switching circuit 25a as a switching signal. In addition, the communication control circuit 28 also has a memory internally storing its own identification code for that purpose. It also controls the transponder 20 as a whole. It should be noted that when transmitting the information on the discharge state of the battery, 1
The phase of the oscillating signal of 00 kHz changes by 180 ° depending on the content of the transmission data.

On the other hand, in the transceiver 10, the radio wave received by the receiving antenna 10b is amplified by the receiving circuit 14 and input to the mixing circuit 15. Here, during the intermittent period T2, the transceiver 10 itself is mixed with the oscillation signal f0 of the VCO 12 that is being generated at that time and synthesized. As a result, the mixed frequency is (twice the transmission frequency of the transceiver + the oscillator 22 of the transponder).
Frequency) and the frequency of the oscillator 22), and the frequency component of the oscillator 22 and its 180 ° phase-modulated component are separated through the BPF 16.

The frequency components separated by the BPF 16 are applied to the phase difference detection circuit 18 and compared with the signal of the 100 kHz oscillation circuit 17 to detect the phase difference G between them, as in the case of the above distance measurement. To be done. The detected phase difference G is sent to the phase change amount detection circuit 19. The phase change amount detected by the phase change amount detection circuit 19 is sent to the distance calculating means 30 during the sweep period T1 and sent to the transmission signal detection circuit 33 during the intermittent period T2. The transmission signal detection circuit 33 compares the reference change rate with the phase change amount detected by the phase change amount detection circuit 19 and performs phase modulation by the 180 ° phase shifter 25 on the transponder 20 side having a change higher than the normal change rate. The detected change point is detected, a pulse having a width corresponding to the 1-bit width of the transmission signal is generated, and the detection pulse is sent to the decoder 34 and the distance calculating means 30. Here, as indicated by the dotted line, the transmission signal detection circuit 33 may receive the output of the phase difference detection circuit 18 and the change point of the phase difference phase-modulated by the 180 ° phase shifter 25 may be detected. In such a case, the transmission signal detection circuit 33
As the comparison reference value of, the maximum phase difference when the phase is not modulated by the 180 ° phase shifter 25, or a value larger than that is adopted.

The decoder 34 is a circuit for extracting an identification code. When receiving the first detection pulse, the decoder 34 starts bit shift at a timing corresponding to the 1-bit width of the transmission signal and detects the transmission start bit. At that time, the identification code is decoded by detecting the identification code with the subsequent detection bit. As a result, the identification code signal of the transponder 20 in which the battery 40 has a voltage value of 0.9 V or less is obtained. This is sent to the MPU 32 via the communication control circuit 31. As a result, the MPU 32 drives the alarm device 35 and displays on the display device 36 that the battery of the transponder 20 corresponding to the identification code has run out. As a result, the operator contacts, for example, a worker carrying the transponder 20 via a speaker or the like.

In the above, the intermittent period T2 is provided between the sweep periods T1 and the data of the discharge state of the battery is transmitted during this intermittent period. In the present invention, however, the intermittent period T2 is used.
It is possible to transmit the data on the discharge state of the battery 40 during the sweep period without providing the above. It is because the transmission signal detection circuit 33 uses the reference change rate and the phase change amount detection circuit 19
180 ° phase shifter 25 on the side of the transponder 20 that has a change higher than the normal change rate by comparing the amount of phase change detected by
This is because the change point that is phase-modulated by is detected. Alternatively, as described above, the same applies when the transmission signal detection circuit 33 receives the output of the phase difference detection circuit 18. As a result, a phase change amount or phase difference of the signal of the 100 kHz oscillation circuit 22 generated by mixing with the sweep signal and a similar signal by shifting the phase shifter by 180 ° can be detected separately. .

Incidentally, At this time, when the signal whose phase is shifted by 180 ° in the phase shifter 25 adversely affects the distance calculation of the distance calculating means 30, the detection pulse of the transmission signal detecting circuit 33 is changed to the distance calculating means as indicated by the dotted line. It is sufficient to send it to 30 and stop the calculation of the distance calculation for the detection period. In this case, if the intermittent period T2 is not provided, the transponder 20 does not need the demodulation circuit 26 and the intermittent period detection circuit 27. On the other hand, when the intermittent period is provided, the phase shift value of the 180 ° phase shifter 25 may be set to a rate of change that exceeds the reference rate of change set by the transmission signal detection circuit 33. The reference change rate set in the transmission signal detection circuit 33 may be arbitrarily selected.

By the way, the detection circuit 28 is an A / D conversion circuit which constantly detects the voltage of the battery 40, in other words,
As shown in FIG. 4 (b), the data converted by this A / D conversion circuit is used to constantly detect the discharge state (or charge state) of the battery 40, and the data is converted to D after the identification code ID.
You may make it transmit in addition to ATA. In this case, the MPU 32 compares the numerical value of the DATA portion of the code from the decoder 34 with the digital value corresponding to 0.9 V and drives the alarm device 35 when it becomes less than this value. Then, the display device 36 displays the voltage value indicated by the transmitted DATA.

The above is the transponder 2 during the intermittent period T2.
Although the description is centered on communication from 0, in this system, the transponder 20 and the transceiver 10 can communicate with each other during the intermittent period T2. In such a case, the transponder 20 can be made to transmit the state of the battery when receiving a command from the transceiver 10 to transmit the state of discharge of the battery 40. The transmission from the transceiver 10 in this case can be performed as shown in FIG. The command of the transceiver 10 can be written in the position of DATA after the identification code ID of FIG. 4 (b). The transponder 20 decodes the identification code ID from the transceiver 10 by the communication control circuit 28, and when it is its own identification code, when the data written in the position of DATA is a command to transmit the state of the battery. Then, the above-mentioned transmission is executed and transmitted to the transceiver 10.

As described above, according to the present invention, the transceiver has a communication function of transmitting data about the discharge state of the battery between the transponder and the transceiver during the distance measurement time and the distance measurement idle time. At the time of communication, as shown in Fig. 4 (c), the free time can be divided into two, and can be controlled separately from the time from the transceiver to the transponder and the time from the transponder to the transceiver. it can. Since there are a plurality of transponders depending on the situation of use, the mutual communication method between the transponder and the transceiver described above can perform communication with more transponders without competition. If the communication function is not required even during the communication time, the intermittent period T2 is set to zero by measuring the distance. There is an advantage that the transponder does not need to use the communication function.

Transceiver 10 to transponder 20
The communication to is performed at a timing after the communication control circuit 31 stops the operation of the triangular wave generation circuit 11. At this time VC
O12 is supplied with a constant voltage from the communication control circuit 31 and is maintained at a predetermined oscillation frequency f0. Then, the oscillation frequency f0 is modulated to another frequency, for example, fs, according to "1" or "0" of the transmission data. Alternatively, the VCO 12 oscillates at the oscillation frequency f0 according to "1" or "0" of the transmission data.
It may be intermittently oscillated at. Then, the demodulation circuit 26 demodulates this transmission data and sends it to the communication control circuit 28.

When the battery state detection circuit 28 of the transponder 20 is composed of an A / D conversion circuit, the digitally converted data is put on the microwave. Therefore, the transceiver can always detect the remaining battery level and the like. On the hydraulic excavator 1 side, by displaying the state of the battery 40 of the transponder 20 in the state as shown in FIG. 5, for example, the operator can know the discharge state (charge state) of the battery of the transponder 20. In the figure, 35a is a buzzer provided on the operation panel of the cab 3 as a specific example of the alarm device 35, and 35b
Is a LE as a specific example of the alarm device 35 provided in the same manner.
It is a D display element. Reference numeral 36 denotes an LCD display device, and each bar graph represents the discharged state of the battery of each transponder or the remaining amount of charge (charged state) of the battery. Further, 37 is various operation switches.

FIG. 6 shows the MP for such a display.
It is a flow chart of control about an alarm and a display which U32 performs. The battery voltage is the specified voltage V0 (= 0.9V)
If it is larger, the timer counter is reset, the warning sound is reset, the LED is stopped, and the machine stop signal is reset. If it is smaller, start the timer counter. Then, when a certain time has elapsed, a warning sound is generated. This warning sound is given to the operator from the buzzer 35a on the operation panel of the control device 4. After the warning sound is generated, the LED 35b is blinked. LED35b
Blinks, for example. Furthermore, when the value of the timer counter is larger than the set time, that is, when the time when the battery voltage is lower than the specified value exceeds the set time,
Set the machine stop signal. The flow of this processing is executed by the MPU 32 of the control device 4. This is done by interrupt calculation at regular intervals. Further, when the distance sensor is not used, interrupt calculation is not performed.

With this configuration, since information from each transceiver is input to the MPU 32, which is a construction machine control device, the discharge amount (charge amount) of the battery of each transceiver.
Is displayed so that the operator can know it. Further, according to the present invention, when the battery charge becomes insufficient, an alarm sound is generated and a warning is given to the operator by blinking the lamp of the control circuit. This alert tells the operator that the worker's battery is dead. The meaning of this alarm is that the operator or the operator can reduce the burden of constantly monitoring the discharge amount of the battery, and the operator can concentrate on the work. In the unlikely event that you do not notice this, after issuing an alarm,
The controller can also cause the construction machine to stop after a certain amount of time.

Since it is constructed as described above,
It is possible to notify the operator before the worst state without constantly monitoring the battery status. Therefore, the burden on the operator is small, and it is possible to prevent the battery of the transponder from running out and prevent the transponder from failing before the battery runs out. These further increase the safety of workers around the construction machine. Needless to say, the transponder may be provided with various alarms and display devices that allow the operator to recognize when the battery is dead. The battery 40 is not limited to the rechargeable battery, and may be a normal dry battery. The phase shift value of the 180 ° phase shifter 25 is not limited to 180 °.

[0030]

As described above, according to the present invention, the transponder is provided with the function of detecting the remaining battery level (battery discharge state) of the transponder, and the detection data of the remaining battery level is added to the received transmission signal and sent to the transceiver side. Since the data is transmitted, the remaining battery level information can be obtained at the transceiver side. Therefore, the construction machine side equipped with the transceiver can detect the dead battery information of the transponder. As a result, the operator of the construction machine can determine whether the battery is dead or the transponder side is far away. Also,
As a result, it is possible to take safety measures for running out of battery, such as issuing an alarm to a transponder worker running out of battery.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a microwave distance sensor mounted on a construction machine to which a safety system for a construction machine according to the present invention is applied.

FIG. 2 is an explanatory diagram of a relationship between a transceiver and a transponder of a construction machine.

FIG. 3 is an explanatory diagram of transmission / reception timing.

FIG. 4 is an explanatory diagram of transmission data.

FIG. 5 is an explanatory diagram of a display state of a liquid crystal display panel of a driver's cab.

FIG. 6 is a flowchart of an alarm process and a display process of the control device.

[Explanation of symbols]

1 ... Hydraulic excavator, 2 ... Worker, 3 ... Driver's cab, 4 ... Control device, 10 ... Transceiver, 10a, 20b ... Transmitting antenna, 10b 20a ... Receiving antenna, 11 ... Triangular wave generating circuit, 12 ... Voltage control oscillation circuit ( VCO), 13, 24
... transmission circuit, 14, 21 ... reception circuit, 25 ... 180 ° phase shifter, 25a ... switching circuit, 15, 23 ... mixing circuit, 16 ... band pass filter (BPF), 17, 22
... 100 kHz oscillation circuit, 18 ... Phase difference detection circuit, 19
... Phase change amount detection circuit, 20 ... Transponder, 27,
31 ... Communication control circuit, 28 ... Intermittent period detection circuit, 29 ...
Battery discharge charge state detection circuit, 30 ... Distance calculation circuit, 3
2 ... Microprocessor (MPU), 34 ... Transmission signal detection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigenori Aoki 650, Kazunachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant

Claims (3)

[Claims] 1. A transmission signal whose frequency is sequentially increased or decreased in a predetermined frequency range is transmitted from a transmitter, and a transponder which receives the transmission signal modulates the reception signal with a predetermined signal and transmits it to the transmitter side. Calculating the distance from the transmitter to the transponder by detecting the rate of change of the phase of the predetermined signal by mixing the transmission signal and the reception signal from the transponder by the receiver on the transmitter side, In a construction machine having a safety system that generates an alarm or the like according to the position of the transponder, the transponder includes a battery that supplies power to the transponder, a first detection circuit that detects a discharge state of the battery, and Of the phase shifter for giving a predetermined phase shift transition to the predetermined signal according to a signal indicating a predetermined discharge state of the battery detected by the detection circuit of 1. The received signal is modulated by force and transmitted to the receiver side, and the receiver indicates the predetermined discharge state from the signal transmitted from the transponder by detecting the predetermined phase shift. A safety system for a construction machine, which detects a signal, excludes a phase change given by the phase shifter, and detects a phase change rate of the predetermined signal to calculate a distance to the transponder. 2. The phase shift value of the phase shifter is selected to be a value that gives a phase change greater than a rate of change of the phase of the predetermined signal to the predetermined signal, and the receiver is A signal indicating the predetermined discharge state is detected from the signal transmitted from the transponder by detecting a change rate of the phase shift larger than the predetermined change rate of the phase, and the detected discharge state is predetermined. When it is below the standard, an alarm is generated or an accident prevention process such as stopping the operation of the machine is performed, and the phase change rate given by the phase shifter is excluded to determine the phase of the predetermined signal. The safety system for a construction machine according to claim 1, wherein the distance to the transponder is calculated by detecting a rate of change. 3. The frequency in the predetermined range is microwave and is intermittently swept, and the transponder causes the receiver to perform a predetermined discharge of the battery while the sweep of the microwave is stopped. Send a signal indicating the status,
The safety system for a construction machine according to claim 2, wherein the first receiver detects a signal indicating the predetermined discharge state from a signal received from the transponder during the period.