Initial excitation circuit and method for diagnosing initial excitation circuit

Abstract

An initial excitation circuit, which is electrically connected to an excitation coil of a generator and excites the excitation coil when the generator is started, is provided with: an input terminal connected to a power source that supplies direct current; an output terminal connected to the excitation coil via a brush and a slip ring of the generator; a circuit breaker connected between the input terminal and the output terminal; and a control circuit that controls the circuit breaker.

Description

Technical Field

[0001] The present invention relates to an initial excitation circuit for exciting an excitation coil of a generator when the generator is started and a diagnosis method thereof. Background Art

[0002] Conventionally, there is known a vehicle electric drive system that uses an internal combustion engine such as a diesel engine as a power source to drive a generator and uses the generated electricity to drive a motor to obtain a propulsion force for driving a work vehicle (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-166684 Summary of the invention

[0006] For the generator installed in the electric drive system described in Patent Document 1, for example, a brushed three-phase AC generator can be used. In this case, the electromotive force during power generation can be used to excite the excitation coil, and the generator can be maintained in a power generation state. On the other hand, when the generator is started from a stopped state, the electromotive force generated by the residual magnetic flux can be used to excite the excitation coil, and the generator can be put into a power generation state. However, since the residual magnetic flux is unstable, it may not be possible to correctly excite the excitation coil when the generator is started. In addition, in the event of poor contact between the brush and the slip ring, the excitation coil may not be correctly excited. In this case, there is a risk that the generator will fail to start, resulting in the inability to start the work vehicle.

[0007] The present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to reliably start a generator mounted on a work vehicle.

[0008] The initial excitation circuit of the present invention is electrically connected to the excitation coil of the generator and excites the excitation coil when the generator is started. The initial excitation circuit comprises: an input terminal connected to a power supply that supplies direct current; an output terminal connected to the excitation coil via a brush and a collector ring of the generator; a circuit breaker connected between the input terminal and the output terminal; and a control circuit that controls the circuit breaker.

[0009] The diagnostic method of the initial excitation circuit of the present invention is a diagnostic method of the initial excitation circuit which is electrically connected to the excitation coil of the generator and excites the excitation coil when the generator is started, and the initial excitation circuit comprises: a positive input terminal connected to the positive side of a power supply supplying direct current; a negative input terminal connected to the negative side of the power supply; a positive output terminal connected to one end of the excitation coil via a brush and a collector ring of the generator; a negative output terminal connected to the other end of the excitation coil via the brush and the collector ring; a first circuit breaker connected to the positive input terminal and the positive output terminal; a second circuit breaker connected between the negative input terminal and the negative output terminal; and a diode, which has an anode connected to the first circuit breaker side and a cathode connected to the positive output terminal side between the first circuit breaker and the positive output terminal, in which a first voltage value corresponding to the voltage between the first circuit breaker and the diode and a second voltage value corresponding to the voltage between the second circuit breaker and the negative output terminal are obtained, and the initial excitation circuit is diagnosed based on the obtained first voltage value and the second voltage value.

[0010] Effects of the Invention

[0011] According to the present invention, it is possible to reliably start a generator mounted on a work vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram showing a work vehicle equipped with a power generation device according to one embodiment of the present invention.

[0013] Figure 2 This is a structural diagram of a power generation device according to one embodiment of the present invention.

[0014] Figure 3 This is a diagram for explaining the diagnostic operation of the initial excitation circuit.

[0015] Figure 4 This is a flowchart showing the flow of diagnostic processing performed in the initial excitation circuit.

[0016] Figure 5 This is a diagram showing a list of diagnosis contents.

[0017] Figure 6 This is a diagram showing the correspondence between the diagnostic conditions and the diagnostic results for each diagnostic content. DETAILED DESCRIPTION

[0018] Hereinafter, the power generation device according to the embodiment of the present invention will be described by taking as an example a case where the working vehicle equipped with the power generation device is a dump truck for use in a mine.

[0019] Figure 1 1 is a diagram schematically showing a working vehicle equipped with a power generation device according to an embodiment of the present invention. A dump truck 100 as a working vehicle is equipped with a power generation device 1, an internal combustion engine 2, a rectifier circuit 3, an inverter 4, and an AC motor 5 as a drive device thereof. The dump truck 100 has wheels driven by the AC motor 5, and also has a cab, a cargo box (vessel: cargo box), an elevator for raising and lowering the cargo box, and the like, and is used, for example, in a mine to transport excavated materials or waste in the mine.

[0020] The power generation device 1 generates electricity by being driven by the internal combustion engine 2, and generates AC power and outputs it to the rectifier circuit 3. The internal combustion engine 2 is, for example, a diesel engine, and drives the power generation device 1 by transmitting the driving force generated by burning fuel to the power generation device 1. The rectifier circuit 3 rectifies the AC power input from the power generation device 1 and converts it into DC power, and outputs the DC power to the inverter 4. The inverter 4 generates AC power of a desired voltage and frequency using the DC power input from the rectifier circuit 3, and outputs it to the AC motor 5. The AC motor 5 is driven by the AC power input from the inverter 4, and generates a driving force for driving the dump truck 100. As a result, the dump truck 100 travels.

[0021] It should be noted that a secondary battery may be provided between the rectifier circuit 3 and the inverter 4 , and direct current may be temporarily stored in the secondary battery for use.

[0022] Figure 2 FIG. 1 is a structural diagram of a power generation device according to an embodiment of the present invention. Figure 2 As shown, the power generation device 1 includes a generator 10 , an excitation circuit 20 , and an initial excitation circuit 30 .

[0023] The generator 10 is a brushed three-phase AC generator having a stator 11 , an exciting coil 12 , slip rings 13 a , 13 b , brushes 14 a , 14 b , a U-phase output line 15 u , a V-phase output line 15 v , and a W-phase output line 15 w .

[0024] The excitation coil 12 is excited by the direct current supplied from the excitation circuit 20 or the initial excitation circuit 30, and generates magnetic flux. The excitation coil 12 is provided on a rotor (not shown), and rotates and moves along the inner side of the stator 11 when the internal combustion engine 2 drives the rotor to rotate. As a result, the magnetic flux interlinked with the stator coil (not shown) provided on the stator 11 changes, and the stator coil generates an electromotive force, thereby generating electricity in the generator 10.

[0025] The three-phase AC power generated by the generator 10 is output via the U-phase output line 15u, the V-phase output line 15v, and the W-phase output line 15w. The U-phase output line 15u, the V-phase output line 15v, and the W-phase output line 15w are connected to Figure 1 Thus, the three-phase AC power is output from the power generation device 1 to the rectifier circuit 3, and is converted into DC power by the rectifier circuit 3.

[0026] Slip rings 13a and 13b are connected to both ends of the field coil 12. The slip rings 13a and 13b rotate around a common rotation axis with the rotor as the rotor is driven to rotate. Brushes 14a and 14b are electrically connected to the field circuit 20 and the initial field circuit 30, and are fixedly arranged in the generator 10 in a manner that they slide with respect to the rotation of the slip rings 13a and 13b. Thus, even if the rotor is driven to rotate, direct current can be supplied from the field circuit 20 or the initial field circuit 30 to the field coil 12.

[0027] The exciting circuit 20 is a circuit for exciting the exciting coil 12 when the generator 10 is in a power generation state. The exciting circuit 20 includes reactors 21u, 21v, 21w, an exciting control circuit 22, and rectifying diodes 23a, 23b, 23c, 23d, 23e, 23f.

[0028] Reactors 21u, 21v, 21w are connected to U-phase output line 15u, V-phase output line 15v, W-phase output line 15w, respectively. Part of the AC power of each phase flowing through U-phase output line 15u, V-phase output line 15v, W-phase output line 15w is output to rectifier diodes 23a to 23f via reactors 21u, 21v, 21w.

[0029] The rectifying diodes 23a to 23f rectify the AC power input through the reactors 21u, 21v, and 21w, convert the AC power into DC power, and output the DC power to the generator 10. In the generator 10, the DC power input from the rectifying diodes 23a to 23f is output to the field coil 12 through the brushes 14a, 14b and the slip rings 13a, 13b. As a result, in the generator 10, the field current flows through the field coil 12, and the field coil 12 is excited.

[0030] The excitation control circuit 22 controls the amount of current flowing through the reactors 21u, 21v, and 21w, thereby controlling the direct current output from the rectifying diodes 23a to 23f to the generator 10 and adjusting the excitation current flowing through the excitation coil 12.

[0031] The initial excitation circuit 30 is a circuit for exciting the excitation coil 12 when starting the generator 10 from a stopped state. The initial excitation circuit 30 includes resistors 31, 32, relays 33, 34, a diode 35, a capacitor 36, a discharge resistor 37, a control circuit 40, interface circuits 41, 42, 43, 44, a positive input terminal 45p, a negative input terminal 45n, a positive output terminal 46p, and a negative output terminal 46n.

[0032] The positive input terminal 45p is connected to the positive side of the battery 52 via the power switch 53. The negative input terminal 45n is connected to the negative side of the battery 52. ​​The battery 52 is a power source for supplying direct current to the initial excitation circuit 30, and is composed of, for example, a lead storage battery. The battery 52 is connected to the charger 51 and is appropriately charged by the charger 51. The charger 51 is composed of, for example, an AC generator driven by the internal combustion engine 2 to generate electricity.

[0033] The power switch 53 is a switch for switching the power supply from the battery 52 to the initial excitation circuit 30. The power switch 53 is switched, for example, in a manner linked to a start switch (not shown) provided on the dump truck 100. That is, when the start switch of the dump truck 100 is switched on to start the dump truck 100, the power switch 53 is switched on accordingly, and the power supply from the battery 52 to the initial excitation circuit 30 begins. It should be noted that in the following description, the power switch 53 is sometimes referred to as "SW0".

[0034] One end of the relay 33 is connected to the positive input terminal 45p via the resistor 31, and the other end is connected to the positive output terminal 46p via the diode 35. One end of the relay 34 is connected to the negative input terminal 45n via the resistor 32, and the other end is connected to the negative output terminal 46n. The relays 33 and 34 as circuit breakers are connected to the control circuit 40, and the electrical connection state between the battery 52 and the capacitor 36 and the excitation coil 12 is switched by the control circuit 40 to either the on state or the off state. It should be noted that in the following description, the relays 33 and 34 are sometimes referred to as "RL1" and "RL2", respectively.

[0035] When the relays 33 and 34 are switched from the off state to the on state, the DC power supplied from the battery 52 is output to the excitation coil 12 via the resistors 31, 32, the relays 33, 34, and the diode 35. Thus, even if the generator 10 is in the stopped state, the excitation current flows through the excitation coil 12 in the generator 10, and the excitation coil 12 can be excited. Thereafter, when the generator 10 is started and enters the power generation state, and the excitation coil 12 begins to be energized from the excitation circuit 20, the relays 33 and 34 are switched to the off state in order to prevent the high-voltage DC current output from the excitation circuit 20 from entering the battery 52 side.

[0036] The resistors 31 and 32 are provided to limit the charging current flowing when the capacitor 36 is charged by switching the relays 33 and 34 to the on state, and to prevent the charging current from exceeding the rated current of the relays 33 and 34 or the diode 35. The diode 35 is provided between the relay 33 and the positive output terminal 46p, with the anode connected to the relay 33 side and the cathode connected to the positive output terminal 46p side. Thus, the current is prevented from flowing back from the initial excitation circuit 30 to the battery 52 side. The discharge resistor 37 is provided to discharge the residual charge of the capacitor 36 when the generator 10 stops to ensure safety.

[0037] The control circuit 40 is a circuit for controlling the operation of the initial excitation circuit 30, and is configured by using a calculation processing device such as a microcomputer. The control circuit 40 has input terminals AI1 and AI2 and output terminals DO1 and DO2. The input terminals AI1 and AI2 are connected to the positive output terminal 46p side of the relay 33 and the negative output terminal 46n side of the relay 34 via interface circuits 41 and 42, respectively. The interface circuits 41 and 42 detect the voltage between the relay 33 and the diode 35, and the voltage between the relay 34 and the negative output terminal 46n, respectively, convert the detected voltage values ​​into voltage values ​​corresponding to the input voltage characteristics of the control circuit 40, and output them to the input terminals AI1 and AI2, respectively. As a result, the control circuit 40 can obtain the voltage value corresponding to the voltage between the relay 33 and the diode 35, and the voltage value corresponding to the voltage between the relay 34 and the negative output terminal 46n, respectively, at the input terminals AI1 and AI2, and monitor these voltages.

[0038] The output terminals DO1 and DO2 of the control circuit 40 are connected to the relays 33 and 34 via the interface circuits 43 and 44, respectively. The output terminals DO1 and DO2 output relay switching signals for switching the relays 33 and 34 from the off state to the on state to the interface circuits 43 and 44, respectively. The interface circuits 43 and 44 convert the relay switching signals input from the output terminals DO1 and DO2 into signals suitable for the operation of the relays 33 and 34, respectively, and output them to the relays 33 and 34. Thus, the control circuit 40 can control the switching operation of the relays 33 and 34 using the relay switching signals output from the output terminals DO1 and DO2.

[0039] Generally, in a three-phase AC generator, when the rotor is rotated from a stopped state, an electromotive force caused by the residual magnetic flux is generated. The electromotive force caused by the residual magnetic flux can be used to energize the excitation coil and start the generator. However, since the residual magnetic flux is unstable, it is not always possible to properly energize the excitation coil when the generator is started. In addition, in a brushed three-phase AC generator, occasional poor contact sometimes occurs due to the formation of an oxide film between the brush and the collector ring or the adhesion (contamination) of foreign matter. In this case, even if the rotor rotates, the excitation coil cannot be properly energized, and in the worst case, the generator may not be started.

[0040] Therefore, in the power generation device 1 of the present embodiment, the initial excitation circuit 30 is connected to the generator 10, and when the generator 10 is started, the relays 33 and 34 are switched to the on state by the control circuit 40. Thus, the capacitor 36 is charged with the direct current supplied from the battery 52, and the excitation coil 12 can be reliably excited by the charge accumulated in the capacitor 36 via the brushes 14a and 14b and the slip rings 13a and 13b.

[0041] However, in the initial excitation circuit 30, if the diode 35 fails to short-circuit and the relays 33 and 34 cannot be switched to the OFF state due to a stuck-on failure, the power generation potential of the generator 10 is electrically coupled to the battery 52 via the excitation circuit 20 and the initial excitation circuit 30 after the generator 10 is started. As a result, there is a risk of damaging the battery 52 or other equipment connected to the battery 52. ​​In order to prevent this, in the power generation device 1 of the present embodiment, the initial excitation circuit 30 performs its own diagnosis when the generator 10 is started, and when an abnormality is found, the relays 33 and 34 are forcibly switched to the OFF state to protect the battery 52 and other equipment.

[0042] Reference Figure 3 The diagnostic operation of the initial exciting circuit 30 will be described below. Figure 3 It is an explanatory diagram of the diagnostic operation of the initial exciting circuit 30 .

[0043] When the dump truck 100 equipped with the power generation device 1 is started, the power switch 53 (SW0) is switched from off to on (time t0) to start the vehicle-mounted system including the power generation device 1. As a result, power starts to be supplied from the battery 52 to the initial excitation circuit 30, a DC voltage is applied between the positive input terminal 45p and the negative input terminal 45n, and the control circuit 40 is started.

[0044] When the control circuit 40 is started, the control circuit 40 switches the relays 33 and 34 (RL1 and RL2) from off to on (time t1). As a result, the capacitor 36 starts to be charged from the battery 52, and the potential on the anode side of the diode 35 gradually rises. As a result, Figure 3 As shown in FIG. 1 , after time t1 , the voltage of the input terminal AI1 increases with a predetermined time constant. The time constant at this time is determined by the resistance values ​​of the resistors 31 and 32 and the capacitance value of the capacitor 36 .

[0045] When capacitor 36 is charged, a DC voltage corresponding to the amount of power stored in capacitor 36 is applied between positive output terminal 46p and negative output terminal 46n. This DC voltage is output to field coil 12 via brushes 14a, 14b and slip rings 13a, 13b, and field coil 12 is excited.

[0046] After the voltage of the input terminal AI1 rises sufficiently and exceeds the predetermined threshold value Vth1, if RL1 is switched off while RL2 is maintained on (time t2), the connection between the battery 52 and the capacitor 36 is disconnected, and the voltage of the input terminal AI1 becomes 0. Thereafter, if RL1 is switched on and RL2 is switched off (time t3), the voltage of the input terminal AI1 rises again according to the voltage on the positive electrode side of the battery 52 and returns to the state before time t2, and the voltage of the input terminal AI2 is affected and rises. Thereafter, after time t3, the voltage of the input terminal AI2 gradually decreases to 0.

[0047] As described above, in the initial excitation circuit 30 , the voltages of the input terminals AI1 and AI2 change according to the switching states of RL1 and RL2 . The control circuit 40 can diagnose the initial excitation circuit 30 by monitoring the voltages of the input terminals AI1 and AI2 .

[0048] Figure 4 1 is a flowchart showing the flow of the diagnostic process performed in the initial exciting circuit 30 . Figure 4 The process shown in the flowchart is implemented by the control circuit 40 of the initial excitation circuit 30 executing a predetermined program, for example.

[0049] When the power switch 53 is switched on and the startup of the control circuit 40 is completed, in step S10, the control circuit 40 sets the value of the variable t to the processing start time t1. In the following steps S20 and S30, the control circuit 40 outputs the relay switching signal from the output terminals DO1 and DO2, respectively, and switches RL1 and RL2 to be turned on. Therefore, if the initial excitation circuit 30 is normal, as shown by Figure 3As described above, the capacitor 36 starts to be charged from the battery 52, and the potential on the anode side of the diode 35 gradually rises.

[0050] In step S40, the control circuit 40 adds the value of the variable t set to t=t1 in step S10 to the prescribed value x. The prescribed value x is used to determine Figure 3 The count value at time t2 is executed according to the control circuit 40. Figure 4 The processing cycle during the processing shown in the flowchart is preset.

[0051] In step S50, the control circuit 40 determines whether the value of the variable t has reached t2. With respect to the processing start time t1, the time t2 is the time when the voltage of the input terminal AI1 exceeds the above threshold value Vth1 when the initial excitation circuit 30 is normal, and is preset according to a time constant based on the resistance values ​​of the resistors 31 and 32 and the capacitance value of the capacitor 36. If the result of the determination in step S50 is that the value of the variable t has not reached t2, the process returns to step S20 to repeat the above process, and after t=t2, the process enters the next step S60.

[0052] In step S60, the control circuit 40 detects the voltage of the input terminal AI1 and determines whether the voltage is greater than or equal to the threshold value Vth1. The threshold value Vth1 is preset according to the voltage when the battery 52 charges the capacitor 36. Specifically, for example, the threshold value Vth1 is set within a range that does not exceed the value obtained by subtracting the forward voltage of the diode 35 from the voltage value obtained by dividing the output voltage of the battery 52 according to the voltage dividing ratio of the resistors 31, 32 and the discharge resistor 37. If the result of the judgment in step S60 is that the voltage of the input terminal AI1 is greater than or equal to the threshold value Vth1, it is judged that the capacitor 36 is normally charged, and the process proceeds to step S70. On the other hand, if the voltage of the input terminal AI1 is less than the threshold value Vth1, it is judged that the capacitor 36 is not normally charged, and the process proceeds to step S65.

[0053] In step S65, the control circuit 40 obtains a diagnosis result that the capacitor 36 is not sufficiently charged due to abnormal charging of the capacitor 36 caused by a disconnection or the like in the initial excitation circuit 30. When step S65 is completed, the process proceeds to step S115.

[0054] In step S70, the control circuit 40 stops the output of the relay switching signal from the output terminal DO1 started in step S20, and switches RL1 to be off. Figure 3 As described above, the connection between the battery 52 and the capacitor 36 is disconnected, and the voltage of the input terminal AI1 drops to approximately zero.

[0055] In step S80, the control circuit 40 detects the voltage of the input terminal AI1 and determines whether the voltage is less than the threshold value Vth2. The threshold value Vth2 is preset according to the voltage generated on the anode side of the diode 35 when the connection between the battery 52 and the capacitor 36 is disconnected. If the result of the determination in step S80 is that the voltage of the input terminal AI1 is less than the threshold value Vth2, it is determined that the connection between the battery 52 and the capacitor 36 is normally disconnected, and the process proceeds to step S90. On the other hand, if the voltage of the input terminal AI1 is greater than the threshold value Vth2, it is determined that the connection between the battery 52 and the capacitor 36 is not normally disconnected, and the process proceeds to step S85.

[0056] In step S85, the control circuit 40 obtains the following diagnosis result: a short-circuit failure of the diode 35 or an abnormality in the on-state of RL1 has occurred in the initial excitation circuit 30, and thus the voltage of the battery 52 or the capacitor 36 is detected on the anode side of the diode 35. When step S85 is completed, the process proceeds to step S115.

[0057] In step S90, the control circuit 40 restarts the output of the relay switching signal from the output terminal DO1 that was stopped in step S70, and switches RL1 to on. In addition, the control circuit 40 stops the output of the relay switching signal from the output terminal DO2 that was started in step S30, and switches RL2 to off. Thus, if the initial excitation circuit 30 is normal, as in Figure 3 As described at time t3, the voltage of the input terminal AI2 rises.

[0058] In step S100, the control circuit 40 detects the voltage of the input terminal AI2 and determines whether the voltage is greater than or equal to a predetermined threshold value Vth3. If the result of the determination in step S100 is that the voltage of the input terminal AI2 is greater than or equal to the threshold value Vth3, it is determined that the connection between the battery 52 and the capacitor 36 is normally disconnected, and the process proceeds to step S110. On the other hand, if the voltage of the input terminal AI2 is less than the threshold value Vth3, it is determined that the connection between the battery 52 and the capacitor 36 is not normally disconnected, and the process proceeds to step S105.

[0059] In step S105, the control circuit 40 obtains a diagnosis result that an ON-fixed abnormality of RL2 has occurred in the initial excitation circuit 30. When step S105 is completed, the process proceeds to step S115.

[0060] In step S110, the control circuit 40 obtains a diagnosis result that the initial excitation circuit 30 is normal. In this case, RL1 and RL2 are switched on again to start the operation of the initial excitation circuit 30, and when the generator 10 is started, the excitation coil 12 is excited by outputting the DC power supplied from the battery 52 to the excitation coil 12. Thereafter, when the generator 10 is started and the excitation circuit 20 starts to energize the excitation coil 12, RL1 and RL2 are switched off.

[0061] In step S115, the control circuit 40 stops the output of the relay switching signals from the output terminals DO1 and DO2, respectively, and forcibly disconnects RL1 and RL2, in order to protect the battery 52 and other circuits, based on the abnormality diagnosis result of any one of steps S65, S85, and S105. Thus, even if it is diagnosed in step S85 or S105 that one of the circuit breakers RL1 and RL2 is fixedly closed, the other circuit breaker is switched to an open state to reliably disconnect the electrical connection with the battery 52, thereby preventing the power generation potential of the generator 10 from being transmitted to the battery 52 side. However, if at least RL1 and the diode 35 are normal, the battery 52 can be protected by disconnecting RL1, so the processing of step S115 may not be performed after step S105, and the initial excitation circuit 30 may continue to operate.

[0062] After the processing of step S110 or S115 is performed, in step S120, the control circuit 40 notifies the outside of the diagnosis result of the initial excitation circuit 30. Here, for example, the diagnosis result is transmitted to a display device (not shown) mounted on the dump truck 100, and the diagnosis result is displayed on the display device, thereby notifying the driver of the dump truck 100 of the diagnosis result of the initial excitation circuit 30. Alternatively, for example, the diagnosis result may be output to a transmission device (not shown) mounted on the dump truck 100, and the diagnosis result may be transmitted from the transmission device to the management center of the dump truck 100, thereby notifying the administrator in the management center of the diagnosis result of the initial excitation circuit 30. In addition, the diagnosis result of the initial excitation circuit 30 may be notified to any object by any method.

[0063] After the process of step S120 is performed, the control circuit 40 ends Figure 4 The diagnostic process is shown in the flowchart.

[0064] Figure 5 2 is a diagram showing a list of diagnostic contents performed in the initial excitation circuit 30. Figure 5 As shown in the table, at time t2 after the capacitor 36 is charged, Figure 4 The process of step S60 is used to diagnose whether RL1 and RL2 are normally switched to the on state. Figure 4 The process of step S80 is used to diagnose whether RL1 is normally switched to the off state and the diode 35 is not short-circuited. Figure 4 The process of step S100 is used to diagnose whether RL2 is normally switched to the disconnected state.

[0065] Figure 6 It is a diagram showing the corresponding relationship between the diagnostic conditions and the diagnostic results of each diagnostic content. Figure 6 As shown in the table, in the on-diagnosis of RL1 and RL2 performed at time t2, RL1 and RL2 are switched to the on state, and the voltage of input terminal AI1 is compared with threshold value Vth1. As a result, if the voltage of input terminal AI1 is above threshold value Vth1, it is diagnosed that the on-action of RL1 and RL2 is normal, and if it is less than threshold value Vth1, it is diagnosed that RL1 or RL2 has an open circuit fault. In addition, in the off-diagnosis of RL1 and the diagnosis of diode 35 performed between time t2 and time t3, RL1 is switched to the off state and RL2 is switched to the on state, and the voltage of input terminal AI1 is compared with threshold value Vth2. As a result, if the voltage of input terminal AI1 is below threshold value Vth2, it is diagnosed that the off-action of RL1 and diode 35 are normal, and if it is greater than threshold value Vth2, it is diagnosed that RL1 or diode 35 has a short circuit fault. In the disconnection diagnosis of RL2 performed at time t3, RL1 is switched to the on state and RL2 is switched to the off state, and the voltage of the input terminal AI2 is compared with the threshold value Vth3. As a result, if the voltage of the input terminal AI2 is greater than the threshold value Vth3, it is diagnosed that the disconnection action of RL2 is normal, and if it is less than the threshold value Vth3, it is diagnosed that a short circuit fault occurs in RL2.

[0066] According to one embodiment of the present invention described above, the following effects are achieved.

[0067] (1) The initial excitation circuit 30 is electrically connected to the excitation coil 12 of the generator 10, and excites the excitation coil 12 when the generator 10 is started. The initial excitation circuit 30 includes: input terminals (positive input terminal 45p and negative input terminal 45n) connected to the battery 52 that supplies direct current; output terminals (positive output terminal 46p and negative output terminal 46n) connected to the excitation coil 12 via brushes 14a, 14b and collector rings 13a, 13b of the generator 10; circuit breakers (relays 33, 34) connected between the input terminals and the output terminals; and a control circuit 40 that controls the circuit breaker. Therefore, the generator 10 mounted on the dump truck 100 as a working vehicle can be reliably started.

[0068] (2) The input terminal of the initial excitation circuit 30 includes a positive input terminal 45p connected to the positive side of the battery 52 and a negative input terminal 45n connected to the negative side of the battery 52, and the output terminal includes a positive output terminal 46p connected to one end of the excitation coil 12 and a negative output terminal 46n connected to the other end of the excitation coil 12. In addition, the circuit breaker of the initial excitation circuit 30 includes a relay 33 connected between the positive input terminal 45p and the positive output terminal 46p, and a relay 34 connected between the negative input terminal 45n and the negative output terminal 46n. Therefore, the direct current flowing through the excitation coil 12 can be reliably controlled in the initial excitation circuit 30 using the direct current supplied from the battery 52.

[0069] (3) The initial excitation circuit 30 further includes a diode 35 connected between the relay 33 and the positive output terminal 46p, wherein the anode of the diode 35 is connected to the relay 33 side and the cathode is connected to the positive output terminal 46p side. Therefore, it is possible to prevent the current from flowing back from the initial excitation circuit 30 to the battery 52.

[0070] (4) The control circuit 40 acquires the voltage value of the input terminal AI1 corresponding to the voltage between the relay 33 and the diode 35, and the voltage value of the input terminal AI2 corresponding to the voltage between the relay 34 and the negative output terminal 46n, and performs the initial diagnosis of the excitation circuit 30 based on the acquired voltage values. Specifically, the control circuit 40 diagnoses the quality of the disconnection operation performed by the relay 33 and the diode 35 based on the voltage value of the input terminal AI1 when the relay 33 is turned off after the relay 33 and the relay 34 are turned on (steps S20 and S30) to energize the excitation coil 12 (steps S70 to S85 and S110). In addition, the control circuit 40 diagnoses the quality of the disconnection operation performed by the relay 34 based on the voltage value of the input terminal AI2 when the relay 33 and the relay 34 are turned on (steps S20 and S30) to energize the excitation coil 12 and the relay 34 is turned off (steps S90 to S105 and S110). Therefore, it is possible to reliably diagnose whether the initial excitation circuit 30 is operating normally, and to safely start the generator 10 using the initial excitation circuit 30 .

[0071] (5) The control circuit 40 diagnoses whether the relay 33 and the relay 34 are fixedly connected during the initial diagnosis of the excitation circuit 30, and when it is diagnosed that either the relay 33 or the relay 34 is fixedly connected (steps S85 and S105), the other circuit breaker is switched to an open state (step S115). Therefore, even if the relay 33 or the relay 34 fails, the electrical connection with the battery 52 can be reliably disconnected, and the power generation potential of the generator 10 can be prevented from being transmitted to the battery 52 side.

[0072] (6) The control circuit 40 notifies the outside of the diagnosis result of the initial excitation circuit 30 (step S120 ). Therefore, when an abnormality occurs in the initial excitation circuit 30 , the driver or the manager of the dump truck 100 can be promptly notified of the abnormality.

[0073] It should be noted that, in the above-described embodiment, the initial excitation circuit 30 of the power generation device 1 mounted on the dump truck 100 as a working vehicle is described as an example, but the present invention is not limited to this. For example, the present invention can also be applied to the initial excitation circuit of a power generation device mounted on a working vehicle other than a dump truck, or a power generation device used for other purposes. Furthermore, a brushed three-phase AC generator is described as an example of the generator 10 connected to the initial excitation circuit 30, but other types of generators may also be used. As long as it is an initial excitation circuit that is connected to the excitation coil provided on the brushed generator and excites the excitation coil when the generator is started, the present invention can be applied.

[0074] In addition, the present invention is not limited to the above-mentioned embodiment, and various changes can be made without departing from the scope of the present invention.

[0075] Description of Reference Numerals

[0076] 1: Generator, 10: Generator, 11: Stator, 12: Field coil, 13a, 13b: Collector ring, 14a, 14b: Brush, 15u: U-phase output line, 15v: V-phase output line, 15w: W-phase output line, 20: Field circuit, 21u, 21v, 21w: Reactor, 22: Field control circuit, 23a, 23b, 23c, 23d, 23e, 23f: Rectifier diode , 30: initial excitation circuit, 31, 32: resistor, 33, 34: relay, 35: diode, 36: capacitor, 37: discharge resistor, 40: control circuit, 41, 42, 43, 44: interface circuit, 45p: positive input terminal, 45n: negative input terminal, 46p: positive output terminal, 46n: negative output terminal, 51: charger, 52: battery, 53: power switch.

Claims

1. An initial excitation circuit electrically connected to an excitation coil of a generator and exciting the excitation coil when the generator is started, the initial excitation circuit being characterized in that: An input terminal connected to a power source supplying direct current; An output terminal connected to the excitation coil via a brush and a slip ring of the generator; a circuit breaker connected between the input terminal and the output terminal; and A control circuit controls the circuit breaker.

2. The initial excitation circuit according to claim 1, characterized in that: The input terminal includes a positive input terminal connected to the positive side of the power supply, and a negative input terminal connected to the negative side of the power supply, The output terminal includes a positive output terminal connected to one end of the excitation coil and a negative output terminal connected to the other end of the excitation coil. The circuit breaker includes a first circuit breaker connected between the positive input terminal and the positive output terminal, and a second circuit breaker connected between the negative input terminal and the negative output terminal.

3. The initial excitation circuit according to claim 2, characterized in that: further comprising a diode connected between the first circuit breaker and the positive output terminal, The diode has an anode connected to the first circuit breaker side, and a cathode connected to the positive output terminal side.

4. The initial excitation circuit according to claim 3, characterized in that: The control circuit acquires a first voltage value corresponding to a voltage between the first circuit breaker and the diode, and a second voltage value corresponding to a voltage between the second circuit breaker and the negative output terminal, and performs diagnosis of the initial excitation circuit based on the acquired first voltage value and the second voltage value.

5. The initial excitation circuit according to claim 4, characterized in that: The control circuit diagnoses an opening operation of the first circuit breaker and quality of the diode based on the first voltage value when the first circuit breaker is opened after the first circuit breaker and the second circuit breaker are turned on to energize the exciting coil.

6. The initial excitation circuit according to claim 4 or 5, characterized in that: The control circuit diagnoses whether the opening operation of the second circuit breaker is good or bad based on the second voltage value when the second circuit breaker is opened after the first circuit breaker and the second circuit breaker are turned on to energize the exciting coil.

7. The initial excitation circuit according to claim 4 or 5, characterized in that: The control circuit diagnoses whether the first circuit breaker and the second circuit breaker are fixedly closed during diagnosis of the initial excitation circuit, and switches the other circuit breaker to an open state when it is diagnosed that either the first circuit breaker or the second circuit breaker is fixedly closed.

8. The initial excitation circuit according to claim 4 or 5, characterized in that: The control circuit notifies the outside of the diagnosis result of the initial excitation circuit.

9. A method for diagnosing an initial excitation circuit, wherein the initial excitation circuit is electrically connected to an excitation coil of a generator and excites the excitation coil when the generator is started, wherein the method for diagnosing the initial excitation circuit is characterized in that: The initial excitation circuit comprises: A positive input terminal connected to the positive side of a power source supplying direct current; A negative input terminal connected to the negative side of the power supply; a positive output terminal connected to one end of the excitation coil via a brush and a slip ring of the generator; a negative output terminal connected to the other end of the excitation coil via the brush and the slip ring; a first circuit breaker connected between the positive input terminal and the positive output terminal; a second circuit breaker connected between the negative input terminal and the negative output terminal; and a diode having an anode connected to the first circuit breaker side and a cathode connected to the positive output terminal side between the first circuit breaker and the positive output terminal, In the diagnostic method of the initial excitation circuit, a first voltage value corresponding to the voltage between the first circuit breaker and the diode and a second voltage value corresponding to the voltage between the second circuit breaker and the negative output terminal are obtained. The initial excitation circuit is diagnosed based on the acquired first voltage value and the second voltage value.

10. The method for diagnosing an initial excitation circuit according to claim 9, characterized in that: acquiring the first voltage value when the first circuit breaker is opened after the first circuit breaker and the second circuit breaker are turned on to energize the exciting coil, Based on the acquired first voltage value, a disconnection operation performed by the first circuit breaker and the quality of the diode are diagnosed.

11. The method for diagnosing an initial excitation circuit according to claim 9 or 10, characterized in that: acquiring the second voltage value when the second circuit breaker is opened after the first circuit breaker and the second circuit breaker are turned on to energize the exciting coil, The quality of the opening operation performed by the second circuit breaker is diagnosed based on the acquired second voltage value.

12. The method for diagnosing an initial excitation circuit according to claim 9 or 10, characterized in that: In the diagnosis of the initial excitation circuit, the first circuit breaker and the second circuit breaker are diagnosed as being stuck in contact, and when it is diagnosed that either the first circuit breaker or the second circuit breaker is stuck in contact, the other circuit breaker is switched to an open state.

13. The method for diagnosing an initial excitation circuit according to claim 9 or 10, characterized in that: The diagnosis result of the initial excitation circuit is notified to the outside.

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