JP2020104818A - Power transmission device for work vehicle - Google Patents

Abstract

To suppress hunting of output from a phase modulation circuit.SOLUTION: A power transmission device for a work vehicle comprises: a power generator which generates electric power by power generated by an internal combustion engine; an electric motor which generates drive power by electric power generated by the power generator; a travel unit which travels by drove power generated by the electric motor; a phase modulation circuit which is connected in series between the power generator and the electric motor, and has a capacitor, and switching elements which are connected to one end side and the other end side of the capacitor; and a control unit which controls the switching element on the basis of a machine angle of the power generator, switches between charged and discharged states of the capacitor, and modulates a phase of electric current fed from power generator to the electric motor.SELECTED DRAWING: Figure 2

Description

The present invention relates to a power transmission device for a work vehicle.

A work vehicle such as a dump truck operates at a work site such as a mining site of a mine. The work vehicle includes a power transmission device that transmits the driving force to the traveling device. Patent Document 1 discloses a power transmission device that drives a generator by power generated by an internal combustion engine, drives an electric motor by electric power generated by the generator, and drives a traveling device by a driving force generated by the motor. There is. The power transmission device disclosed in Patent Document 1 has a capacitor and a phase modulation circuit having a switching element connected to one end side and the other end side of the capacitor, and switches the switching element to switch between a charged state and a discharged state of the capacitor. And a control device that modulates the phase of the current supplied from the generator to the electric motor by switching.

JP, 2018-052458, A

If the timing of switching between the charged state and the discharged state of the capacitor is not properly controlled, the output from the phase modulation circuit and the output from the electric motor may fluctuate, which is called hunting.

An aspect of the present invention is to suppress hunting of an output from a phase modulation circuit or the like.

According to the aspect of the present invention, a generator that generates electric power by the power generated by the internal combustion engine, an electric motor that generates a driving force by the electric power generated by the generator, and a traveling that travels by the driving force generated by the electric motor. An apparatus, a phase modulation circuit connected in series between the generator and the electric motor, having a capacitor and a switching element connected to one end side and the other end side of the capacitor; and a phase modulation circuit based on a mechanical angle of the generator. And a control device for controlling the switching element to switch between a charged state and a discharged state of the capacitor to modulate the phase of the current supplied from the generator to the electric motor. Will be provided.

According to the aspects of the present invention, hunting of the output from the phase modulation circuit or the like is suppressed.

FIG. 1 is a side view showing a work vehicle according to this embodiment. FIG. 2 is a configuration diagram showing a power transmission device for a work vehicle according to the present embodiment. FIG. 3 is a circuit diagram showing the phase modulation circuit according to the present embodiment. FIG. 4 is a diagram showing an operation example of the phase modulation circuit according to the present embodiment. FIG. 5 is a diagram showing an operation example of the phase modulation circuit according to the present embodiment. FIG. 6 is a diagram showing an operation example of the phase modulation circuit according to the present embodiment. FIG. 7 is a diagram showing an operation example of the phase modulation circuit according to the present embodiment. FIG. 8 is a functional block diagram showing the control device according to the present embodiment. FIG. 9: is a graph which shows operation|movement of the power transmission device which concerns on a comparative example. FIG. 10 is a graph showing the operation of the power transmission device according to this embodiment. FIG. 11 is a diagram showing the relationship between the induced voltage generated by the generator and the timing of switching the switching element. FIG. 12 is a diagram showing the timing of switching the switching element according to the comparative example. FIG. 13 is a diagram showing the timing of switching the switching element according to the present embodiment. FIG. 14 is a graph showing the results of an experiment conducted to confirm the effect of the control device according to this embodiment.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The constituent elements of the respective embodiments described below can be appropriately combined. In addition, some components may not be used.

[Work vehicle]
FIG. 1 is a side view showing a work vehicle 1 according to this embodiment. In the present embodiment, the work vehicle 1 is a dump truck that carries a load such as earth and sand or crushed stone at a work site such as a mining site of a mine. In the following description, the work vehicle 1 is appropriately referred to as the dump truck 1.

The dump truck 1 includes a vehicle body 2 and a vessel 3 supported by the vehicle body 2. The vehicle body 2 has a traveling device 4 and a vehicle body 5 supported by the traveling device 4. The traveling device 4 has wheels 6 and an axle 7 that rotatably supports the wheels 6. The wheels 6 include front wheels 6F and rear wheels 6R. The axle 7 includes a front axle 7F that rotatably supports the front wheels 6F and a rear axle 7R that rotatably supports the rear wheels 6R.

The vessel 3 is a structure on which cargo is loaded. The vessel 3 can be moved up and down with respect to the vehicle body 2 by a lifting device such as a hoist cylinder. The cargo of the vessel 3 is discharged by raising the vessel 3 by the lifting device.

The vehicle body 5 includes a driver's cab 8, a power generation device 9 having an internal combustion engine 11 and a power transmission device 10, and a control device 30. The driver gets on the cab 8. In the present embodiment, the dump truck 1 is a manned dump truck that travels based on an operation of a driver who is in the cab 8.

The driver's cab 8 is provided with an accelerator pedal 8a. The accelerator pedal 8a is operated by the driver. The output of the internal combustion engine 11 is adjusted based on the operation amount of the accelerator pedal 8a.

FIG. 2 is a configuration diagram showing the power generation device 9 of the dump truck 1 according to the present embodiment. The power generation device 9 drives the traveling device 4 by generating power by an electric drive system. As shown in FIG. 2, the power generation device 9 has an internal combustion engine 11 and a power transmission device 10.

The internal combustion engine 11 is a power source of the dump truck 1. A diesel engine is exemplified as the internal combustion engine 11. The internal combustion engine 11 is connected to the power transmission shaft 17. The internal combustion engine 11 rotates the power transmission shaft 17. The generator 12 and the hydraulic pump 18 are connected to the power transmission shaft 17. The hydraulic pump 18 supplies hydraulic oil to hydraulic equipment included in the dump truck 1. The hydraulic pump 18 is driven by the power of the internal combustion engine 11. The internal combustion engine 11 is provided with an engine rotation sensor 11s that detects an engine rotation speed that indicates the rotation speed of the internal combustion engine 11.

[Power transmission device]
The power transmission device 10 transmits the power of the internal combustion engine 11 to the traveling device 4. The power transmission device 10 includes a generator 12, a phase modulation circuit 13, a rectifier 14, an inverter 15, an electric motor 16, an angle sensor 40, and a control device 30.

The generator 12 generates electric power by the power generated by the internal combustion engine 11. The generator 12 includes an alternator. The generator 12 has a stator and a rotor. A coil is arranged on one of the stator and the rotor of the generator 12, and an electromagnet is arranged on the other of the stator and the rotor. The rotor of the generator 12 is connected to the power transmission shaft 17. The rotor of the power generator 12 rotates as the power transmission shaft 17 rotates, and an induced voltage E and an induced current are generated in the coil by electromagnetic induction. The generator 12 generates a three-phase alternating voltage and alternating current as the induced voltage E and the induced current. The generator 12 is provided with a generator rotation sensor 12s that detects the generator rotation speed that indicates the rotation speed of the rotor of the generator 12.

The generator 12 has an exciting device 19. The exciter 19 adjusts the magnetic force of the field-side electromagnet by adjusting the exciting current flowing through the field-side electromagnet, thereby adjusting the power generation amount of the generator 12.

The phase modulation circuit 13 modulates the phase of the current supplied from the generator 12 to the electric motor 16. The phase modulation circuit 13 is a magnetic energy regeneration phase modulation circuit. The phase modulation circuit 13 is connected in series between the generator 12 and the electric motor 16. In the present embodiment, the phase modulation circuit 13 is connected in series between the generator 12 and the rectifier 14. A three-phase AC voltage and AC current are generated from the generator 12. The phase modulation circuit 13 includes a first phase modulation circuit 13A, a second phase modulation circuit 13B, and a third phase modulation circuit 13C that are arranged in parallel so as to correspond to the three-phase AC voltage and AC current. A rectifier 13 a that rectifies the AC voltage output from the phase modulation circuit 13 is connected to the phase modulation circuit 13. Further, the rectifier 13a is provided with a voltage sensor 13s that detects an added value of the three-phase DC voltage values rectified by the rectifier 13a.

The rectifier 14 rectifies the AC voltage output from the phase modulation circuit 13 and outputs a DC voltage. The smoothing capacitor 20 is arranged between the rectifier 14 and the inverter 15. The smoothing capacitor 20 smoothes the DC current output from the rectifier 14. A load device 21 such as a retarder is arranged between the rectifier 14 and the inverter 15. The load device 21 absorbs kinetic energy when the dump truck 1 is braked. A blower motor BM that drives a fan that cools the load device 21 is provided between the rectifier 14 and the inverter 15.

The inverter 15 converts the DC voltage output from the rectifier 14 and smoothed by the smoothing capacitor 20 into an AC voltage and outputs the AC voltage. The inverter 15 has a front wheel side output unit 15F that outputs an AC voltage to the front wheel 6F side and a rear wheel side output unit 15R that outputs an AC voltage to the rear wheel 6R side. Each of the front wheel side output section 15F and the rear wheel side output section 15R is arranged in parallel so as to correspond to the three-phase AC voltage.

The electric motor 16 generates a driving force by the electric power generated by the generator 12. The electric motor 16 is driven by the electric power output from the inverter 15. The electric motor 16 includes a motor. The traveling device 4 travels by the driving force generated by the electric motor 16. The electric motor 16 has, for example, a front wheel side electric motor 16F arranged on the front wheel 6F side and a rear wheel side electric motor 16R arranged on the rear wheel 6R side. The electric motor 16 is connected to the transmission mechanism 22. The transmission mechanism 22 transmits the driving force generated by the electric motor 16 to the wheels 6 via the axle 7. The motor 16 is provided with a motor rotation sensor 16s that detects a motor rotation speed indicating the rotation speed of the electric motor 16.

The angle sensor 40 detects the mechanical angle θ of the generator 12. In the present embodiment, the angle sensor 40 detects the mechanical angle θ of the power generator 12 by detecting the rotation angle of the power transmission shaft 17. The angle sensor 40 includes, for example, a resolver.

[Phase modulation circuit]
FIG. 3 is a circuit diagram showing the phase modulation circuit 13 according to this embodiment. FIG. 3 is an electric circuit diagram showing an example of one phase modulation circuit 13. As shown in FIG. 3, the phase modulation circuit 13 includes a capacitor C and switching elements S connected to one end side and the other end side of the capacitor C, respectively. The switching element S includes a first switching element S1, a second switching element S2, a third switching element S3, and a fourth switching element S4.

In the following description, each of the first switching element S1, the second switching element S2, the third switching element S3, and the fourth switching element S4 is appropriately referred to as a switching element S1, a switching element S2, a switching element S3, and a switching element. It is referred to as S4.

Further, the phase modulation circuit 13 has a connecting portion P1 connected to the generator 12 and a connecting portion P2 connected to the rectifier 14.

The switching element S is a switching element such as a MOSFET (metal-oxide-semiconductor field-effect transistor) or an IGBT (Insulated Gate Bipolar Transistor). The switching element S is not limited to the above, and may be another type of switch. Hereinafter, description will be made on an embodiment in which an IGBT is used as the switching element S.

The first switching element S1 and the fourth switching element S4 are connected to one end of the capacitor C. The second switching element S2 and the third switching element S3 are connected to the other end side of the capacitor C. The phase modulation circuit 13 is arranged in parallel with the first portion A1 in which the switching element S4 and the switching element S1 are connected in series from the connection portion P1 to the connection portion P2, and is arranged in parallel with the first portion A1. It has a second portion A2 in which the switching element S3 and the switching element S2 are connected in series toward the connection portion P2.

The emitter terminal of the switching element S4 is connected to the connecting portion P1. The collector terminal of the switching element S4 is connected to the collector terminal of the switching element S1. The emitter terminal of the switching element S1 is connected to the connection portion P2. The collector terminal of the switching element S3 is connected to the connection portion P1. The emitter terminal of the switching element S3 is connected to the emitter terminal of the switching element S2. The collector terminal of the switching element S2 is connected to the connection portion P2.

The switching element S4 and the switching element S1, and the switching element S3 and the switching element S2 are connected in parallel.

One end of the capacitor C is connected to the connection portion P3 between the switching element S4 and the switching element S1 in the first portion A1. The other end of the capacitor C is connected to the connection portion P4 between the switching element S3 and the switching element S2 of the second portion A2. A bridge circuit is formed by the four switching elements S and the capacitors C.

Each of FIG. 4, FIG. 5, FIG. 6, and FIG. 7 is a diagram showing an operation example of the phase modulation circuit 13 according to the present embodiment. The switching element S is turned on or off. In the present embodiment, the switching element S1 and the switching element S3 are simultaneously turned on or off, and the switching element S2 and the switching element S4 are simultaneously turned on or off. When the switching elements S1 and S3 are turned on, the switching elements S2 and S4 are turned off. When the switching elements S1 and S3 are turned off, the switching elements S2 and S4 are turned on.

FIG. 4 shows a state in which the switching element S1 and the switching element S3 are turned on and the switching element S2 and the switching element S4 are turned off in a state where the voltage of the connection portion P1 is negative. In the case of the state shown in FIG. 4, a current flows from the connection part P2 to one end of the capacitor C via the switching element S1, and a current flows from the other end of the capacitor C to the connection part P1 via the switching element S3. In this case, the capacitor C is charged.

FIG. 5 shows a state in which the switching element S1 and the switching element S3 are turned on and the switching element S2 and the switching element S4 are turned off while the voltage of the connection portion P1 is positive. In the case of the state shown in FIG. 5, a current flows from the connection portion P1 to the other end of the capacitor C via the switching element S3, and a current flows from one end of the capacitor C to the connection portion P2 via the switching element S1. In this case, the capacitor C is discharged.

FIG. 6 shows a state in which the switching element S2 and the switching element S4 are turned on and the switching element S1 and the switching element S3 are turned off while the voltage of the connection portion P1 is positive. In the case of the state shown in FIG. 6, a current flows from the connection part P1 to one end of the capacitor C via the switching element S2, and a current flows from the other end of the capacitor C to the connection part P2 via the switching element S4. In this case, the capacitor C is charged.

FIG. 7 shows a state in which the switching element S2 and the switching element S4 are turned on and the switching element S1 and the switching element S3 are turned off in a state where the voltage of the connection portion P1 is negative. In the case of the state shown in FIG. 7, a current flows from the connection part P2 to the other end of the capacitor C via the switching element S4, and a current flows from one end of the capacitor C to the connection part P1 via the switching element S2. In this case, the capacitor C is discharged.

[Control device]
FIG. 8 is a functional block diagram showing the control device 30 according to the present embodiment. The control device 30 compensates for the delay of the current phase with respect to the voltage phase generated in the generator 12. As shown in FIG. 8, the control device 30 includes a data acquisition unit 36, a storage unit 35, an internal combustion engine control unit 31, a generator control unit 32, an electric motor control unit 33, and a phase modulation circuit control unit 34. Have.

The data acquisition unit 36 acquires the accelerator opening command value calculated based on the operation amount of the accelerator pedal 8s. The data acquisition unit 36 includes detection data of the engine rotation sensor 11s indicating the engine rotation speed, detection data of the generator rotation sensor 12s indicating the generator rotation speed, detection data of the motor rotation sensor 16s indicating the motor rotation speed, and a DC voltage value. The detection data of the voltage sensor 13 s indicating the added value of and the detection data of the angle sensor 40 indicating the mechanical angle θ of the rotor of the generator 12 are acquired.

The storage unit 35 stores a computer program and data used to control the dump truck 1 including the power transmission device 10. In the present embodiment, the storage unit 35 stores the engine rotation speed command value calculation data, the DC voltage command value calculation data, the output designated value calculation data, the motor torque command value calculation data, and the switching command value calculation data.

The engine rotation speed command value calculation data is correlation data indicating the relationship between the accelerator opening command value and the engine rotation speed command value. The DC voltage command value calculation data is correlation data indicating the relationship between the engine rotation speed, the motor rotation speed, and the DC voltage command value. The output designated value calculation data is correlation data indicating the relationship between the engine rotation speed and the engine torque. The motor torque command value calculation data is correlation data indicating the relationship between the motor rotation speed and the motor torque command value. The switching command value calculation data is correlation data indicating the relationship between the mechanical angle θ of the generator 12 and the switching command value.

The internal combustion engine control unit 31 controls the internal combustion engine 11. The internal combustion engine control unit 31 calculates the engine rotation speed command value based on the accelerator opening command value and the engine rotation speed command value calculation data stored in the storage unit 35, and outputs it to the internal combustion engine 11.

The generator control unit 32 controls the generator 12. The generator control unit 32 is based on the detection data of the engine rotation sensor 11s, the detection data of the motor rotation sensor 16s, the detection data of the voltage sensor 13s, and the DC voltage command value calculation data stored in the storage unit 35. , Calculates the excitation current command value and outputs it to the generator 12.

The electric motor control unit 33 controls the electric motor 16. The electric motor control unit 33 stores the accelerator opening command value, the detection data of the engine rotation sensor 11s, the detection data of the motor rotation sensor 16s, the output designated value calculation data stored in the storage unit 35, and the storage unit 35. Based on the calculated motor torque command value calculation data, the motor torque command value is calculated and output to the electric motor 16.

The phase modulation circuit control unit 34 controls the phase modulation circuit 13. The phase modulation circuit control unit 34 controls the switching element S shown in S1 to S4 based on the detection data of the angle sensor 40 to switch between the charged state and the discharged state of the capacitor C, and the generator 12 to the motor 16 Modulates the phase of the current supplied to. The phase modulation circuit control unit 34 calculates a switching command value based on the detection data of the angle sensor 40 and the switching command value calculation data stored in the storage unit 35, and outputs the switching command value to the phase modulation circuit 13.

The phase modulation circuit control unit 34 adjusts the ON and OFF timings of the switching element S shown in S1 to S4 based on the mechanical angle θ of the generator 12. The charging state and the discharging state of the capacitor C of the phase modulation circuit 13 are switched by adjusting the ON and OFF timings of the switching element S shown in S1 to S4.

[Operation of phase modulation circuit]
Next, the operation of the phase modulation circuit 13 will be described. FIG. 9: is a graph which shows operation|movement of the power transmission device which concerns on a comparative example. FIG. 10 is a graph showing the operation of the power transmission device 10 according to this embodiment.

The power transmission device according to the comparative example does not include the phase modulation circuit 13. FIG. 9 is a graph showing each of voltage, current, and power factor generated in the generator 12 when the phase modulation circuit 13 is not provided. FIG. 9A shows the relationship between the voltage generated in the generator 12 and the time. FIG. 9B shows the relationship between the current generated in the generator 12 and the time. FIG. 9C shows the relationship between the power factor and time. FIG. 9D shows the relationship between the time and the DC voltage value generated by the generator 12 and detected by the voltage sensor 13s. The power factor is a value represented by active power/(active power^2+reactive power^2)^1/2.

As shown in FIGS. 9A and 9B, when the phase modulation circuit 13 is not provided, the electric power generated by the generator 12 is reduced by the influence of the reactance of the coil provided in the generator 12 in the voltage. The phase of the current is delayed by α with respect to the phase. Therefore, as shown in FIG. 9C, the value of the power factor becomes a value smaller than 1. In this case, the DC voltage value detected by the voltage sensor 13s is V _P.

The power transmission device 10 according to the present embodiment includes a phase modulation circuit 13. FIG. 10 is a graph showing each of the voltage, the current, and the power factor generated in the generator 12 and output from the connecting portion P2 of the phase modulation circuit 13 when the phase modulation circuit 13 is provided. FIG. 10B shows the relationship between the voltage output from the connection P2 of the phase modulation circuit 13 and time. FIG. 10C shows the relationship between the current output from the connection P2 of the phase modulation circuit 13 and time. FIG.10(d) shows the relationship between a power factor and time. FIG graph. 10 (b), the voltage _{V acout} outputted from the connecting portion P2 of the phase modulation circuit 13, the voltage _{V acin} output from the generator 12, and the voltage V output from the capacitor C of the phase modulation circuit 13 Each of _c is shown. FIG. 10A is a timing chart showing ON and OFF timings of the switching element S1 and the switching element S3 of the phase modulation circuit 13, and ON and OFF timings of the switching element S2 and the switching element S4. FIG. 10E shows the relationship between the time and the DC voltage value output from the phase modulation circuit 13 and detected by the voltage sensor 13s.

As shown in FIG. 10, when the value of the voltage V _acin generated in the generator 12 becomes the minimum value (negative value) in the time section (1), the phase modulation circuit control unit 34 _causes the switching element S1 to _operate. Also, the switching element S3 is turned on, and the switching elements S2 and S4 are turned off. That is, the phase modulation circuit 13 is in the state shown in FIG. In this case, since the voltage of the connecting portion P1 of the phase modulation circuit 13 is negative, the capacitor C is charged.

In the section (2) after the section (1), the phase modulation circuit control unit 34 _keeps the switching element S1 and the switching element S3 ON until the timing when the value of the voltage V _acin gradually increases and switches to a positive value. The state where the switching element S2 and the switching element S4 are OFF is maintained. That is, the phase modulation circuit 13 is in the state shown in FIG. In this case, since the voltage of the connection P1 of the phase modulation circuit 13 is positive, the capacitor C is discharged.

In the section (3) after the section (2), the phase modulation circuit control unit 34 switches the switching elements S1 and S3 to OFF at the timing when the value of the voltage V _acin becomes the maximum value (positive value). , The switching elements S2 and S4 are turned on. That is, the phase modulation circuit 13 is in the state shown in FIG. In this case, since the voltage of the connecting portion P1 of the phase modulation circuit 13 is positive, the capacitor C is charged.

In the section (4) after the section (3), the phase modulation circuit control unit 34 _keeps the switching elements S1 and S3 OFF until the timing when the value of the voltage V _acin gradually decreases and switches to a negative value. The state where the switching element S2 and the switching element S4 are ON is maintained. That is, the phase modulation circuit 13 is in the state shown in FIG. In this case, since the voltage of the connection portion P1 of the phase modulation circuit 13 is negative, the capacitor C of the phase modulation circuit 13 is discharged.

In this way, the phase modulation circuit control unit 34 switches the switching element S of the phase modulation circuit 13 between ON and OFF, thereby controlling the timing of charging and discharging the capacitor C. The voltage V _acin output from the generator 12 is an addition value of the voltage V _acout output from the phase modulation circuit 13 and the voltage V _c output from the capacitor C. The phase of the voltage V _acin becomes equal to the phase of the current output from the phase modulation circuit 13. In the power output from the phase modulation circuit 13, the voltage and the current have the same phase, so that the power factor becomes 1. As shown in FIG. 10E, the DC voltage value output from the phase modulation circuit 13 is V _Q. The DC voltage value V _Q is larger than the DC voltage value V _P when the phase modulation circuit 13 is not provided.

By providing the phase modulation circuit 13 in this manner, the power factor of the generator 12 is improved. Due to the improvement of the power factor, in the power transmission device 10, when the internal combustion engine 11 and the generator 12 have the same size and the accelerator opening is the same, the output of the generator 12 is increased. Therefore, the transmission efficiency of the power transmission device 10 is improved.

[Hunting suppression]
In the present embodiment, the switching element S shown in S1 to S4 is switched between ON and OFF based on the mechanical angle θ of the generator 12. That is, the timing at which the capacitor C is switched between the charged state and the discharged state is controlled based on the mechanical angle θ of the generator 12. By switching the switching element S between ON and OFF based on the mechanical angle θ of the generator 12, hunting of the output from the phase modulation circuit 13 is suppressed or hunting of the output from the electric motor 16 is suppressed. .. The hunting of the output from the phase modulation circuit 13 includes at least one of the hunting of the voltage V _acout output from the phase modulation circuit 13 and the hunting of the current output from the phase modulation circuit 13. The hunting of the output from the electric motor 16 includes the hunting of the torque output from the electric motor 16.

FIG. 11 is a diagram showing the relationship between the induced voltage E generated by the coil of the generator 12 and the timing of switching the switching element S. As shown in FIG. 11, the switching phase difference means a shift in the timing of switching the switching element S between ON and OFF with respect to the induced voltage E.

11A1 and 11A2 are graphs showing the relationship between the induced voltage and the time. 11(b1) and 11(b2) are timing charts showing the timing of switching the switching elements S1 and S3 between ON and OFF. 11(c1) and 11(c2) are timing charts showing the timing of switching the switching elements S2 and S4 between ON and OFF. 11(a1), (b1), and (c1) are timing charts when the switching phase difference is 0°. 11(a2), (b2), and (c2) are timing charts when the switching phase difference is 90°.

FIG. 11 shows a state in which switching from one of ON and OFF of the switching element S to the other is ideally executed. As shown in FIGS. 11(a1) and 11(a2), the induced voltage E generated by the generator 12 draws a sine wave. If the switching element S is switched based on the induced voltage E, hunting of the output from the phase modulation circuit 13 or the like is sufficiently suppressed.

The timing of switching the switching element S between ON and OFF can be arbitrarily shifted with respect to the induced voltage. The difference in the timing of switching the switching element S between ON and OFF with respect to the induced voltage E is called a switching phase difference.

11(a1), (b1), and (c1) are timings when the induced voltage is switched from negative to positive or when the induced voltage is switched from positive to negative, and when the switching element S is switched to ON and OFF. A chart is shown. The switching phase difference at this time is 0°.

11(a2), (b2), and (c2) show the switching element S at the timing at which the induced voltage switches from negative to positive or at the timing shifted by only a quarter cycle from the timing at which the induced voltage switches from positive to negative. The timing chart at the time of switching to ON and OFF is shown. The switching phase difference at this time is 90°.

By changing the switching phase difference, the phase of the voltage _{Vacout with} respect to the voltage _Vacin can be adjusted. In other words, the effect of the phase modulation circuit 13 can be adjusted.

FIG. 12 is a diagram showing the timing of switching the switching element S according to the comparative example. 12A is a graph showing the relationship between the induced voltage E generated by the coil of the generator 12 and the time, and FIG. 12B is the graph showing the relationship between the voltage V _acin output from the generator 12 and the time. FIG. 12C is a timing chart showing the timing of switching the switching elements S1 and S3 between ON and OFF. FIG. 12D is a timing chart showing the timing of switching the switching elements S2 and S4 between ON and OFF.

The inventor of the present application has a phenomenon in which the voltage V _acin output from the generator 12 is distorted without drawing a sine wave due to charging and discharging of the capacitor C, as shown in FIG. I found that it occurs. Further, the inventor of the present application has _found that if the switching timing of the switching element S is controlled based on the distorted voltage V _acin , the phenomenon in which the output from the phase modulation circuit 13 or the like _hunts occurs.

For example, as described with reference to FIG. 10, if the voltage V _acin output from the generator 12 _{draws a} sine wave without distortion, the switching timing of the switching element S is controlled based on the value of the voltage V _acin. This is equivalent to controlling the switching timing of the switching element S based on the induced voltage E. However, actually, as shown in FIG. _12B , a phenomenon occurs in which the voltage V _acin output from the generator 12 is distorted. If the switching timing of the switching element S is controlled based on the distorted voltage V _acin , the timing of switching the charged state and the discharged state of the capacitor C is not properly controlled, and as a result, the phase modulation circuit 13 Output hunts.

FIG. 13 is a diagram showing the timing of switching the switching element S according to this embodiment. 13A is a graph showing the relationship between the induced voltage E generated by the coil of the generator 12 and the time, and FIG. 13B is a graph showing the voltage V _acin actually output from the generator 12 and the time. 13C is a timing chart showing the timing of switching the switching element S between ON and OFF, and FIG. 13D shows the mechanical angle θ of the generator 12 and the time. It is a graph which shows the relationship of.

In the present embodiment, the phase modulation circuit control unit 34 controls the timing of switching the switching element S based on the mechanical angle θ of the generator 12. The mechanical angle θ of the generator 12 is not affected by the charging and discharging of the capacitor C. As shown in FIGS. 13A and 13D, the induced voltage E draws a periodic sine wave, and the mechanical angle θ of the generator 12 draws a periodic triangular wave. The phase modulation circuit control unit 34 controls the timing of switching the switching element S based on the mechanical angle θ of the generator 12 to appropriately control the timing of switching the charged state and the discharged state of the capacitor C. You can Therefore, hunting of the output from the phase modulation circuit 13 or the like is suppressed.

For example, in FIG. 10, the switching of the switching element S, which was performed at the timing of the boundary between the section (4) and the section (1), is performed at the timing when the mechanical angle θ of the generator 12 becomes 0 degrees, for example. Switching of the element S, which is performed at the boundary timing between the section (2) and the section (3), is performed at the timing when the mechanical angle θ of the generator 12 becomes 180 degrees, for example. By switching the element S, the phase modulation circuit control unit 34 can appropriately control the timing of switching between the charged state and the discharged state of the capacitor C based on the mechanical angle θ of the generator 12.

For example, when the phase modulation circuit control unit 34 determines that the mechanical angle θ of the generator 12 is 0 degrees based on the detection data of the angle sensor 40, the switching device S1 and the switching device S3 are turned on, and the switching device S3 is turned on. S2 and switching element S4 are turned off. As a result, the phase modulation circuit 13 enters the state shown in FIG. In this case, since the voltage of the connecting portion P1 of the phase modulation circuit 13 is negative, the capacitor C is charged.

When the phase modulation circuit control unit 34 determines that the mechanical angle θ of the generator 12 is 90 degrees based on the detection data of the angle sensor 40, the switching element S1 and the switching element S1 until the mechanical angle becomes 180 degrees. The state in which S3 is ON and the switching elements S2 and S4 are OFF is maintained. As a result, the phase modulation circuit 13 enters the state shown in FIG. In this case, since the voltage of the connection P1 of the phase modulation circuit 13 is positive, the capacitor C is discharged.

When it is determined that the mechanical angle θ of the generator 12 is 180 degrees based on the detection data of the angle sensor 40, the phase modulation circuit control unit 34 switches the switching element S1 and the switching element S3 to OFF, and the switching element S2. And the switching element S4 is turned on. As a result, the phase modulation circuit 13 enters the state shown in FIG. In this case, since the voltage of the connecting portion P1 of the phase modulation circuit 13 is positive, the capacitor C is charged.

When it is determined that the mechanical angle θ of the generator 12 is 270 degrees based on the detection data of the angle sensor 40, the phase modulation circuit control unit 34 switches until the mechanical angle becomes 0 degree (360 degrees). The state in which S1 and the switching element S3 are OFF and the states in which the switching element S2 and the switching element S4 are ON are maintained. As a result, the phase modulation circuit 13 enters the state shown in FIG. In this case, since the voltage of the connection portion P1 of the phase modulation circuit 13 is negative, the capacitor C of the phase modulation circuit 13 is discharged.

[effect]
As described above, according to this embodiment, the switching element S is controlled based on the mechanical angle θ of the generator 12, and the charged state and the discharged state of the capacitor C are switched. Therefore, the timing of switching the charged state and the discharged state of the capacitor C is appropriately controlled. Therefore, hunting of the output from the phase modulation circuit 13 is suppressed.

FIG. 14 is a graph showing the results of an experiment conducted to confirm the effect of the control device 30 according to this embodiment. In the graph shown in FIG. 14, the vertical axis represents the amplitude of the DC voltage output from the connection portion P2 of the phase modulation circuit 13 and output from the rectifier 14, and the horizontal axis represents the switching phase difference. In the graph shown in FIG. 14, the line La represents the amplitude of the DC voltage when the phase modulation circuit 13 is controlled based on the mechanical angle θ of the generator 12, and the line Lb represents the voltage V _acin output from the generator 12. The amplitude of the DC voltage when the phase modulation circuit 13 is controlled based on the above is shown. In FIG. 14, the smaller the amplitude of the DC voltage is, the smaller the hunting is. As shown in FIG. 14, when the phase modulation circuit 13 is controlled based on the mechanical angle θ of the generator 12, the amplitude of the DC voltage is _determined by the phase modulation circuit 13 based on the voltage V _acin output from the generator 12. It is smaller than the amplitude of the DC voltage when controlled. As described above, it was confirmed that the hunting of the output from the phase modulation circuit 13 and the like is suppressed by controlling the phase modulation circuit 13 based on the mechanical angle θ of the generator 12.

[Other Embodiments]
In the above embodiment, two switching elements S are provided on each of the one end side and the other end side of the capacitor C. For example, one switching element may be provided on at least one of the one end side and the other end side of the capacitor C. Three or more switching elements may be provided on at least one of the one end side and the other end side of the capacitor C.

In the above-described embodiment, the dump truck 1 is a manned dump truck that travels based on the operation of the driver in the cab 8. The dump truck 1 may be an unmanned dump truck that travels based on a control command without depending on a driver's operation. The dump truck 1 may be a rigid dump truck or an articulated dump truck.

1... Dump truck (work vehicle), 2... Vehicle body, 3... Vessel, 4... Traveling device, 5... Car body, 6... Wheel, 6F... Front wheel, 6R... Rear wheel, 7... Axle, 7F... Front axle, 7R ... rear axle, 8... driver's cab, 8a... accelerator pedal, 9... power generation device, 10... power transmission device, 11... internal combustion engine, 11s... engine rotation sensor, 12... generator, 12s... generator rotation sensor, 13 ... phase modulation circuit, 13a... rectifier, 13s... voltage sensor, 13A... first phase modulation circuit, 13B... second phase modulation circuit, 13C... third phase modulation circuit, 14... rectifier, 15... inverter, 15F... front wheel side Output part, 15R... Rear wheel side output part, 16... Electric motor, 16F... Front wheel side electric motor, 16R... Rear wheel side electric motor, 16s... Motor rotation sensor, 17... Power transmission shaft, 18... Hydraulic pump, 19... Exciting device, 20... Smoothing capacitor, 21... Load device, 22... Transmission mechanism, 30... Control device, 31... Internal combustion engine control unit, 32... Generator control unit, 33... Electric motor control unit, 34... Phase modulation circuit control unit, 35... Storage part, 36... Data acquisition part, 40... Angle sensor, A1... First part, A2... Second part, C... Capacitor, P1... Connection part, P2... Connection part, P3... Connection part, P4... Connection part, S... switching element, S1... first switching element (switching element), S2... second switching element (switching element), S3... third switching element (switching element), S4... fourth switching element (switching element).

Claims (4)

A generator that generates electric power by the power generated in the internal combustion engine,
An electric motor that generates a driving force by the electric power generated by the generator,
A traveling device that travels by the driving force generated by the electric motor,
A phase modulation circuit having a switching element connected in series between the generator and the electric motor and connected to a capacitor and one end side and the other end side of the capacitor;
A control device that controls the switching element based on a mechanical angle of the generator, switches between a charged state and a discharged state of the capacitor, and modulates a phase of a current supplied from the generator to the electric motor.
A power transmission device for a work vehicle including the. An angle sensor for detecting the mechanical angle of the generator is provided,
Controlling the switching element based on the detection data of the angle sensor,
The power transmission device for a work vehicle according to claim 1. The control device compensates for a delay in the phase of the current with respect to the phase of the voltage generated in the generator,
The power transmission device for a work vehicle according to claim 1 or 2. The switching element includes a first switching element, a second switching element, a third switching element, and a fourth switching element,
The phase modulation circuit includes a first portion in which the fourth switching element and the first switching element are connected in series from the generator toward the electric motor, and the generator is arranged in parallel with the first portion. To the electric motor, the third switching element and the second switching element having a second portion connected in series,
One end of the capacitor is connected to a connection portion of the first portion between the fourth switching element and the first switching element, and the other end of the capacitor is the third switching portion of the second portion. Connected to a connection between an element and the second switching element,
The power transmission device for a work vehicle according to any one of claims 1 to 3.

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