JP2019064451A - Work vehicle - Google Patents

Abstract

To suppress vibration of an engine at the time of changeover of a velocity stage thereby improving ride comfort.SOLUTION: A work vehicle comprising a control device which changes a drive mode between an engine drive mode in which a wheel is driven by power of an engine, and a motor drive mode in which a generator-motor is so made as to function as a motor, and the wheel is driven by power of the generator-motor. The control device releases a lock-up clutch and changes a drive mode to the motor drive mode at the time of gear changing of a transmission, and generates a load on a hydraulic circuit thereby decelerating a revolution speed of the engine. When a revolution speed of an input shaft of the transmission and a revolution speed of an output shaft of the engine become coincident with each other, the control device couples the lock-up clutch, and changes a drive mode to the engine drive mode from the motor drive mode.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a work vehicle.

  A wheel loader, which is an example of a work vehicle, excavates and transports earth and sand, etc. with a bucket portion of a hydraulic work unit at the front while traveling by transmitting engine power to a tire by a torque converter (torque converter) and transmission (T / M). Do.

  When the traveling portion of the wheel loader is motorized, the loss can be reduced by driving the power transmission in the low rotational speed region where the torque converter loss is large in the low rotational speed region. Further, in the middle and high speed regions, the drive efficiency can be enhanced by engaging the lockup clutch and directly connecting the engine and the axle to drive the engine.

  As an example of such a wheel loader, Patent Document 1 discloses that “an engine disconnecting clutch for coupling or disconnecting the output shaft of the engine and the sun gear is provided, and the sun gear and the carrier shaft are , And the engine output shaft and the sun gear by the engine disconnect clutch, and the sun gear and the carrier shaft are coupled by the first running mode in which the vehicle travels with the torque generated by the engine and motor generator, or by the direct coupling clutch. In addition, a second travel mode is established in which the output shaft of the engine and the sun gear are disconnected by the engine disengagement clutch and the vehicle travels only with the motor generator (see abstract).

  In Patent Document 1, when the vehicle speed is low and medium, the motor power and the engine power are combined, and switching of the transmission gear is controlled based on the storage amount of the capacitor, while the vehicle speed is high. In addition, by engaging the direct coupling clutch, it is possible to drive with high engine efficiency and drive with high efficiency.

JP, 2011-93345, A

  In Patent Document 1, when the direct coupling clutch is engaged and switching of the speed gear is performed, a speed change occurs according to the change of the gear ratio of the transmission at the time of speed gear switching. There is a problem that comfort worsens.

  The present invention has been made in view of the above-described situation, and an object thereof is to improve the ride comfort by suppressing the vibration of the engine at the time of speed gear switching in a work vehicle.

  In order to solve the above-mentioned problems, a typical present invention is an engine, a generator that generates electric power by the power of the engine, a generator motor driven by electric power supplied from the generator, the engine or the generator motor , A lock-up clutch provided between the engine and the transmission, a hydraulic circuit driven by the power of the engine, and an engine drive mode driving the wheels by the power of the engine And a control device that causes the generator motor to function as a motor and switches a drive mode between the motor drive mode in which the wheels are driven by the power of the generator motor, and the control device includes: At the time of a shift of the transmission, the lockup clutch is released to operate the drive mode. While switching to the motor drive mode, a load is generated on the hydraulic circuit to reduce the number of revolutions of the engine, and the number of revolutions of the input shaft of the transmission matches the number of revolutions of the output shaft of the engine Sometimes, the lockup clutch is engaged to switch the drive mode from the motor drive mode to the engine drive mode.

  According to the present invention, it is possible to improve the ride comfort by suppressing the vibration of the engine at the time of speed stage switching. In addition, the subject except having mentioned above, a structure, and an effect are clarified by description of the following embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The external appearance side view of the wheel loader which is an example of the working vehicle which concerns on this invention. The system configuration figure of a wheel loader. Hydraulic circuit diagram of the wheel loader. Explanatory drawing of the switching method of the drive mode of a wheel loader. It is a functional block diagram of a control device. The flowchart which shows the control procedure of the switching of the drive mode at the time of switching a speed stage. FIG. 7 is a diagram showing the flow of energy when the wheel loader shifts from the second speed motor drive mode to the third speed. FIG. 7 is a diagram showing the flow of energy when the wheel loader shifts from the second speed motor drive mode to the third speed. FIG. 7 is a diagram showing the flow of energy when the wheel loader shifts from the second speed motor drive mode to the third speed. FIG. 7 is a diagram showing the flow of energy when the wheel loader shifts from the second speed motor drive mode to the third speed. It is the figure which took time on each axis | shaft and took each rotation speed on the vertical axis | shaft in the change of the state shown to FIGS. The figure which shows the example which consumes regenerative energy by a hydraulic circuit. The figure which shows the example which consumes regenerative energy by a thermal resistor. The figure which shows the example which consumes regenerative energy by vehicle body inertia. The figure which shows the example which consumes regeneration energy by 3 phase short circuit brakes. The figure which shows the example which consumes regenerative energy by an exhaust device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same elements will be denoted by the same reference symbols and redundant description will be omitted.

First Embodiment
FIG. 1 is an external side view of a wheel loader 200 which is an example of a work vehicle according to the present invention, and FIG. 2 is a system configuration diagram of the wheel loader shown in FIG. As shown in FIG. 1, the wheel loader 200 has a front frame 202 having a lift arm 201, a bucket 20, front wheels 18a and 18b and the like, and a rear frame 203 having a cab 19 and rear wheels 18c and 18d and the like. The lift arm 201 is rotated (up and down) in the vertical direction by driving the lift arm cylinder 13, and the bucket 20 is rotated (dump or cloud) in the vertical direction by driving the bucket cylinder 14. The front wheels 18a and 18b and the rear wheels 18c and 18d will be described as the wheels 18 when collectively referred to.

  The front frame 202 and the rear frame 203 are rotatably connected to each other by a connecting shaft (not shown). The wheel loader 200 is an articulated work vehicle in which the front frame 202 and the rear frame 203 are bent at a connection shaft. In the front frame 202 and the rear frame 203, one end and the other end of a pair of steering cylinders (hereinafter referred to as steering cylinders) 12 centering on a connecting shaft are rotatably engaged. The front frame 202 and the rear frame 203 can be respectively rotated about the connecting shaft by extending one of the pair of steering cylinders 12 and degenerating the other by a hydraulic circuit (see FIG. 3) described later. As a result, the relative attachment angle between the front frame 202 and the rear frame 203 changes, and the vehicle body bends and turns.

  As shown in FIG. 2, the wheel loader 200 is roughly divided into a hydraulic working unit A driven by pressure oil and a traveling unit B for traveling a vehicle body by engine power. The bucket cylinder 14, the lift arm cylinder 13 and the steering cylinder 12, which constitute the hydraulic working unit A, are driven by pressure oil supplied from the hydraulic pump 9 via the control valve 11. The hydraulic fluid is supplied to the bucket cylinder 14 and the lift arm cylinder 13 to perform work such as digging, and the hydraulic fluid is supplied to the steering cylinder 12 to steer the vehicle body.

  On the other hand, engine 1, generator 5, hydraulic pump 9, control valve 11, inverters 6, 8, chopper 25, thermal resistor 26, generator motor 7, gearbox 31, transmission 33, exhaust device 27, throttle device 27a, wheels 18, the propeller shafts 15f and 15r, the differential gears 16f and 16r, the drive shafts 17a, 17b, 17c and 17d, and the rotation speed sensors 41, 42, 43, and 44 constitute a traveling unit B.

  The hydraulic pump 9 is a variable displacement hydraulic pump. The rotary shaft of the hydraulic pump 9 is provided coaxially with the drive shaft of the engine 1. When the hydraulic pump 9 is driven by the engine 1, the hydraulic oil of the oil tank 10 (see FIG. 3) is supplied to the steering cylinder 12, the lift arm cylinder 13 and the bucket cylinder 14 via the control valve 11.

  The control valve 11 is a control valve that controls the flow of hydraulic fluid to the bottom chamber or rod chamber of the steering cylinder 12, the lift arm cylinder 13, and the bucket cylinder 14. The control valve 11 is controlled by a signal (hydraulic signal or electrical signal) output from an operating device (not shown) installed in the cab 19. The hydraulic oil guided from the hydraulic pump 9 to the control valve 11 is distributed to the steering cylinder 12, the lift arm cylinder 13 and the bucket cylinder 14 according to the operation of the operating device.

  In the generator 5, a rotor is attached to a rotating shaft coaxial with the output shaft of the engine 1, and a stator is disposed on the outer periphery of the rotor. The generator 5 generates electricity when the rotor is rotated by the engine 1 and supplies power to the generator motor 7 via the inverter 6 and the inverter 8. Here, a generator-motor is used instead of the generator 5, and the generator-motor is made to function as a generator, and the generated electric power is stored in a storage device such as a capacitor or a battery. The generator motor may be functioned as a motor to assist the engine 1.

  The generator motor 7 is connected at its output shaft to the input shaft of the gear box 31 and is driven by the electric power generated by the generator 5 to transmit torque to the input shaft of the gear box 31. Further, as will be described later, the electric power regenerated by the generator motor 7 is converted to thermal energy via the chopper 25 and the thermal resistor 26 and consumed.

  The output shaft of the engine 1 is connected to the input shaft of the gearbox 31 via a lockup clutch 32. Further, the output shaft of the gear box 31 is connected to the input shaft of the transmission 33 via the transmission clutch 34.

  The output torque of the engine 1 or the output torque of the generator motor 7 is transmitted in the order of the gear box 31 and the transmission 33, and is transmitted to the front wheels through the propeller shafts 15f and 15r, the differential gears 16f and 16r and the drive shafts 17a, 17b, 17c and 17d. The wheel loader 200 travels by being transmitted to the wheels 18a and 18b and the rear wheels 18c and 18d.

  Further, a rotation speed sensor 41 for detecting the rotation speed of the rotation shaft of the generator 5, a rotation speed sensor 42 for detecting the rotation speed of the output shaft of the engine 1, and a rotation speed sensor for detecting the rotation speed of the output shaft of the generator motor 7. A rotational speed sensor 44 is provided to detect the rotational speed of the output shaft of the gear box 31, and the rotational speed signals from the rotational speed sensors 41, 42, 43 and 44 are input to the control device 100.

  Control device 100 has a CPU, a ROM, a RAM, a communication interface (I / F), etc., and controls the traveling of wheel loader 200 based on the control program, specifically, controls switching the driving mode of wheel loader 200, etc. I do.

  Next, a hydraulic circuit provided in the wheel loader 200 according to the present embodiment will be described. FIG. 3 is a hydraulic circuit diagram of the wheel loader 200 shown in FIG. As shown in FIG. 3, in the hydraulic circuit of the wheel loader 200, the hydraulic pump 9, the oil tank 10, the control valve 11, the variable displacement second hydraulic pump 301, the first proportional valve 302, the first A two proportional valve 303, a hydraulic motor 304, a cooling fan 305, a cooling core 306, and an oil temperature sensor 307 are provided.

  As described above, the hydraulic pump 9 is driven by the generator 5 driven by the engine 1, and the hydraulic oil of the oil tank 10 is transmitted to the steering cylinder 12, the lift arm cylinder 13 and the bucket cylinder 14 via the control valve 11. Supply 1). The first proportional valve 302 variably controls the displacement amount (capacity) of the hydraulic pump 9 in accordance with a control signal from the control device (M / C) 100.

  The control valve 11 is configured to include a first direction control valve 308 and a second direction control valve 309. The first direction control valve 308 supplies hydraulic oil supplied from the hydraulic pump 9 to the steering cylinder 12 in accordance with a signal output from an operating device installed in the driver's cab 19. The second direction control valve 309 supplies hydraulic oil supplied from the hydraulic pump 9 to the pair of lift arm cylinders 13 in accordance with a signal output from an operating device installed in the driver's cab 19. In FIG. 3, the bucket cylinder 14 is not shown.

  When the second hydraulic pump 301 is driven by the generator 5, the hydraulic oil of the oil tank 10 is supplied to the hydraulic motor 304 to drive the hydraulic motor 304. The second proportional valve 303 variably controls the amount of displacement (capacity) of the second hydraulic pump 301 in accordance with a control signal from the control device 100. The amount of displacement of the second hydraulic pump 301 is controlled based on the temperature of the hydraulic oil in the oil tank 10 detected by the oil temperature sensor 307.

  The cooling fan 305 is driven by the hydraulic motor 304 to cool the hydraulic oil that has flowed into the cooling core 306 provided downstream of the cooling fan 305. Therefore, the rotational speed of the cooling fan 305 is controlled in accordance with the amount of displacement of the second hydraulic pump 301. In other words, the rotational speed of the cooling fan 305 is controlled according to the temperature of the hydraulic oil detected by the oil temperature sensor 307.

  In addition, a fixed displacement flow control valve (hereinafter, referred to as a fixed throttle) 310 is provided on the first conduit 400 downstream of the control valve 11, that is, in the return flow path to the oil tank 10. Therefore, the pressure oil from the hydraulic pump 9 passes through the fixed throttle 310 and returns to the oil tank 10.

  In the fixed throttle 310, energy flow equivalent to the braking force is consumed as heat when the flow rate of the pressure oil is limited and passed. That is, the braking force applies a hydraulic load to the hydraulic pump 9. As a result, the load of the generator 5 driven by the surplus power and driving the hydraulic pump 9 is increased, and the electric energy at the time of regeneration can be consumed. Thereby, the engine 1 can be decelerated promptly (details will be described later). The heat corresponding to the braking force generated by the fixed throttle 310 is cooled by the cooling fan 305.

  Next, the drive mode of the traveling unit B will be described. The traveling unit B is driven by two drive modes, an engine drive mode (E) and a motor drive mode (M). In the engine drive mode, the power of the engine 1 is directly transmitted to the transmission 33 through the lockup clutch 32 to drive the vehicle body. In the motor drive mode, the generator 1 drives the generator 5, the power generated by the generator 5 causes the generator motor 7 to perform a powering operation (function as a motor), and the rotational drive force of the generator motor 7 is transmitted to the transmission 33. Run the car body.

  The engine drive mode and the motor drive mode are switched by the lockup clutch 32. The engine drive mode is set when the lockup clutch 32 is engaged, and the motor drive mode is set when the lockup clutch 32 is released. As described above, the wheel loader 200 according to the present embodiment can travel and work without using the power storage device. However, since the power storage device is not provided, the regenerated energy can not be stored. Therefore, the regenerated energy is consumed by the heat resistor 26, the exhaust system 27, the hydraulic working unit A, the three-phase short circuit brake of the generator motor 7, and the like.

  Next, a method of switching the drive mode of the wheel loader 200 will be described. FIG. 4 is a diagram for describing a method of switching the drive mode of the wheel loader 200. As shown in FIG. Since the engine 1 can not output torque when stopped and the engine 1 can not rotate at low speed, the wheel loader 200 travels in the motor drive mode (M) at the first speed stage (low speed). When the speed gear is switched to second gear, third gear, or fourth gear, as shown in FIG. 4, the engine rotational speed changes according to the gear ratio of each speed gear. Since a large change in rotational speed occurs at the time of speed gear switching (during gear change), when the speed gear is switched in the engine drive mode (E), a vibration shock is generated due to the change in rotational speed.

  Therefore, in the present embodiment, the engine drive mode is switched to the motor drive mode at the time of shifting (when upshifting from 2nd to 3rd and 3rd to 4th), and after adjusting the engine speed, the engine is started from the motor drive mode The control to switch back to the drive mode suppresses the vibration shock at the time of speed stage switching to improve the ride comfort. The method of adjusting the engine speed will be described later.

  Next, details of the control device 100 will be described. FIG. 5 is a functional block diagram of the control device 100. As shown in FIG. The speed stage calculation unit 110 calculates the speed stage from the vehicle speed sensor from the vehicle speed sensor, the brake, forward / backward travel, and accelerator signals generated by the operation of the operator. The speed stage switching signal generator 120 generates a speed stage switching signal from the calculation result of the speed stage by the speed stage calculator 110. Based on the speed stage switching signal generated by speed stage switching signal generation section 120, drive mode switching section 130 switches the drive mode between the engine drive mode and the motor drive mode. At the time of speed stage switching, as described in FIG. 3, the rotational speed of the engine 1 changes, so the engine rotational speed control unit 140 adjusts the rotational speed of the engine 1. Furthermore, the regenerative energy consumption control unit 150 determines a regenerative energy consumption method obtained when adjusting the rotational speed of the engine 1 (details will be described later).

  Next, a control procedure of switching of the drive mode by the control device 100 will be described. FIG. 6 is a flowchart showing a control procedure of switching of the drive mode when switching the speed stage. Here, the process illustrated in FIG. 6 is performed by the control device 100, and more specifically, is performed by each unit illustrated in FIG.

  As shown in FIG. 6, first of all, in the engine drive mode or the motor drive mode, the speed stage calculation unit 110 generates the speed stage from the respective signals of the vehicle speed from the vehicle speed sensor, the brake generated by the operator's operation, Is calculated, and the calculation result is output to the speed stage switching signal generation unit 120 (step S1).

  The speed stage switching signal generation unit 120 generates a speed stage switching signal based on the calculation result of the speed stage. For example, when it is determined that the gear shift should be made from the third gear to the fourth gear, the gear shift signal generation unit 120 generates a gear shift signal for shifting the gear to the fourth gear (step S2). When the speed stage switching signal is input to the drive mode switching unit 130, the drive mode switching unit 130 switches the drive mode from the engine drive mode to the motor drive mode as shown in FIG. 4 (step S3).

  When the drive mode is switched to the motor drive mode, the engine speed control unit 140 releases the transmission clutch 34 (step S4), and controls the engine speed to a desired value (step S5). Then, engine speed control unit 140 determines whether the input shaft speed of transmission 33 input from speed sensor 44 (see FIG. 1) matches the engine speed input from speed sensor 42. Determine if If they do not match (step S6 / No), the process returns to step S5, and the determination is repeated until the input shaft speed of the transmission 33 and the engine speed match. If they match (step S6 / Yes), the engine speed control unit 140 controls the transmission clutch 34 to be engaged in step S7.

  Next, the drive mode switching unit 130 controls the lockup clutch 32 to be engaged (step S8), switches the drive mode from the motor drive mode to the engine drive mode (step S9), and ends the process. As described above, in this embodiment, when switching the speed gear, the drive mode is switched to the motor drive mode first, and then the engine speed is made equal to the rotation speed suitable for changing the speed gear. It is controlled to switch to the drive mode.

  FIGS. 7 to 10 are diagrams showing the flow of energy when the wheel loader 200 shifts (shifts up) from the second speed motor drive mode to the third speed. The direction of the arrow in the figure indicates the flow of energy. In addition, a part of structure shown in FIG. 2 is abbreviate | omitting illustration in FIGS.

<Step (1)>: Second-speed motor drive mode As shown in FIG. 7, in the second-speed motor drive mode, the generator 5 is driven by the power of the engine 1 to generate power, and inverters 6 and 8 perform frequency conversion. The wheel loader 200 travels by causing the generator motor 7 to function as a motor and transmitting the driving force of the generator motor 7 to the wheels 18 via the transmission 33. The lockup clutch 32 is released. At this time, the engine speed is Ne, the motor speed of the second speed (speed of the generator motor 7) is N2, and the speed of the transmission input shaft of the second speed is N2.

<Step (2)>: 3-speed motor drive mode (rotational speed adjustment of generator motor 7)
As shown in FIG. 8, when the speed gear switching signal of the third speed is input, the transmission clutch 34 is released, and the load of the generator motor 7 is set to zero. In this state, the generator motor 7 is caused to function as a generator, and the speed N2 of the second speed is changed (decelerated) to the speed N3 of the third speed. At this time, the electric energy regenerated by the generator motor 7 is converted into heat energy by the heat resistor 26 and consumed. That is, the heat energy corresponding to the braking force is consumed by the heat resistor 26, thereby decelerating the generator motor 7 from N2 to N3.

<Step (3)>: 3-speed motor drive mode (rotation speed adjustment of engine 1)
As shown in FIG. 9, the lockup clutch 32 is engaged, and the generator motor 7 and the engine 1 are connected. As a result, the engine rotational speed is controlled by the rotational speed N3 of the generator motor 7, so the speed is reduced from N2 to N3. At this time, regenerative energy corresponding to a braking force for reducing the engine speed is consumed by the thermal resistor 26 via the generator 5.

<Step (4)>: Three-speed engine drive mode As shown in FIG. 10, when the number of revolutions of the engine 1 matches the number of revolutions of the generator motor 7, the transmission clutch 34 is engaged to drive the engine 1 Transmit to 18 As a result, since the engine rotational speed in the engine drive mode in the third gear accelerates from N3, a smooth shift from the second gear to the third gear can be realized.

  FIG. 11 is a diagram showing changes in the states described in FIGS. 7 to 10, with time on the horizontal axis and each rotation speed on the vertical axis. In the figure, (1) corresponds to the state of FIG. 7, (2) to the state of FIG. 8, (3) to the state of FIG. 9, and (4) to the state of FIG.

  In (1), since the wheel loader 200 starts at the second speed and travels in the motor drive mode at that time, the rotation speed Ne of the output shaft of the engine 1 is constant, and the rotation speed Nm of the output shaft of the generator motor 7 The rotation speed Ntm of the input shaft of the transmission 33 similarly increases with the passage of time, and the rotation speed Nt of the axle gradually increases with the passage of time.

  In (2), although the rotation speed Ne of the output shaft of the engine 1 is constant, the transmission clutch 34 is released and the generator motor 7 functions as a generator, so the rotation speed Nm of the output shaft of the generator motor 7 and the transmission 33 The rotation speed Ntm of the input shaft decreases with time.

  In (3), the engine 1 and the lockup clutch 32 are engaged, and the rotation speed Ne of the output shaft of the engine 1 gradually decreases with time, and coincides with the rotation speed Nm of the output shaft of the generator motor 7.

  In (4), when the transmission clutch 34 is engaged and the rotation speed Ne of the output shaft of the engine 1 increases with the passage of time, the rotation speed Nm of the output shaft of the generator motor 7 and the input shaft of the transmission 33 The rotational speed Ntm and the rotational speed Nt of the axle increase. That is, the wheel loader 200 accelerates by switching to the third speed.

  Next, how to consume the regenerative energy to decelerate the engine 1 at the time of speed gear switching will be described with some specific examples. The control of the consumption of the regenerative energy is performed by the regenerative energy consumption control unit 150 of the control device 100.

<Consumption of regenerative energy by hydraulic equipment>
FIG. 12 shows an example in which the regenerative energy generated at the time of shifting of the transmission 33 is consumed by the hydraulic circuit. As shown in FIG. 12, the motive power of the engine 1 is transmitted to the hydraulic pump 9 and the cylinders 12, 13 and 14, and by driving the hydraulic working unit A, the regenerative energy is consumed. That is, the power is consumed by the hydraulic drive on the hydraulic circuit to generate a load, the engine 1 decelerates, and the rotational speed of the engine 1 can be matched with the rotational speed of the input shaft of the transmission 33. As an example of driving the hydraulic circuit to consume the regenerative energy, in addition to operating the lift arm 201 and the bucket 20, the fixed throttle 310 is used to perform loading, or the relief valve 315 is operated. Thus, regenerative energy can be consumed.

<Consumption of regenerative energy by thermal resistor>
FIG. 13 shows an example in which the thermal energy is consumed by the regenerative energy generated when the transmission 33 is shifted. As shown in FIG. 13, the regenerative energy generated at the time of deceleration of the engine 1 is consumed by the thermal resistor 26 via the generator 5. That is, the power of the engine 1 is converted to heat in the thermal resistor 26 to generate a load, and the engine 1 decelerates. Thus, the rotational speed of the engine 1 can be made to coincide with the rotational speed of the input shaft of the transmission 33.

<Consumption of regenerative energy>
FIG. 14 shows an example in which the regenerative energy of the generator 5 generated at the time of the shift of the transmission 33 is consumed. As shown in FIG. 14, the power of the engine 1 is consumed as kinetic energy of the vehicle body by accelerating the generator motor 7. That is, acceleration by the generator motor 7 becomes a load on the engine 1 and the engine 1 decelerates. Thus, the rotational speed of the engine 1 can be made to coincide with the rotational speed of the input shaft of the transmission 33.

<Consumption of regenerative energy by 3-phase short circuit brake>
FIG. 15 shows an example in which the regenerative energy generated at the time of gear shift of the transmission 33 is consumed by the three-phase short circuit brake of the generator 5. As shown in FIG. 15, the motive power of the engine 1 is transmitted to the generator 5 and consumed by the copper loss due to the three-phase short circuit brake of the generator 5. That is, the engine 1 is decelerated by the load of the three-phase short circuit brake. Thus, the rotational speed of the engine 1 can be made to coincide with the rotational speed of the input shaft of the transmission 33.

<Consumption of regenerative energy by exhaust brake>
FIG. 16 shows an example in which the regenerative device generated at the time of gear shift of the transmission 33 is consumed by the exhaust system 27. As shown in FIG. 16, an exhaust device 27 is provided in an exhaust pipe line of the engine 1, and the exhaust device 27 has a throttle device 27 a for throttling the flow rate of the exhaust gas. By throttling the flow rate of the exhaust gas with the expansion device 27a and operating the exhaust brake, the engine 1 is decelerated with the exhaust resistance of the exhaust device 27 as a load. Thus, the rotational speed of the engine 1 can be made to coincide with the rotational speed of the input shaft of the transmission 33.

  As described above, according to the present embodiment, after switching to the motor drive mode at the time of speed gear switching, adjustment is made to switch to the engine drive mode after adjusting the rotational speed of the engine 1 and the input shaft of the transmission 33 to match. By doing this, it is possible to suppress the vibration at the time of speed gear switching of the engine 1 and to improve the ride comfort. In addition, since smooth speed gear switching can be performed, engine stall can be prevented.

  Further, since the regenerative energy generated at the time of speed stage switching can be consumed by the hydraulic circuit, the thermal resistor 26, the vehicle inertia, the three-phase short circuit brake of the generator 5, the exhaust system 27, etc. Even if there is, the vibration at the time of speed stage switching can be suppressed.

  In particular, in the case where the regenerative energy is consumed by the hydraulic circuit (FIG. 12), effective use of the energy can be achieved by using the regenerative energy as a part of the digging operation, for example, moving the lift arm 201 up and down with the regenerative energy. it can. In particular, in the wheel loader, the lift arm 201 is lifted while accelerating to frequently carry out a loading operation of loading the earth and sand onto the dump truck. Therefore, in the wheel loader 200, it can be said that it is preferable to adopt a method of consuming the regenerative energy at the time of gear change with a hydraulic circuit.

  The consumption methods shown in FIGS. 12 to 16 can be used not only alone but also in combination with each other. For example, the engine 1 may be decelerated by combining other consumption methods while consuming regenerative energy by driving the hydraulic circuit (FIG. 12). In this case, from the values input from the rotational speed sensors 41, 42, 43 and 44 by the regenerative energy consumption control unit 150 (see FIG. 5), the working state of the hydraulic working unit A, the traveling speed of the wheel loader 200, etc. It may be decided to use any of the consumption methods alone or in combination.

  The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment is described in detail to explain the present invention in an easy-to-understand manner, and is not necessarily limited to one having all the described configurations. Although the upshift has been exemplified, it may be applied to downshifting. However, at the time of downshifting, not the control for reducing the engine speed but the control for increasing the engine speed is required. In this case, this can be realized by outputting a command signal for increasing the rotational speed to the controller performing engine control. Furthermore, at the time of downshifting, it is expected that the motor is regenerating because in most cases the operator has the intention to decelerate. In this case, since the generator 5 can perform power running, it is possible to increase the engine speed in a shorter time.

  Further, in the above-described embodiment, the present invention has been described by taking the thermal resistor 26 as an example, but it is also possible to change the thermal resistor 26 to a power storage device, and it is not excluded as a technical idea. .

1 Engine 5 Generator 6 Inverter 7 Generator Motor 8 Inverter 9 Hydraulic Pump 11 Control Valve 12 Steering Cylinder 13 Lift Arm Cylinder 14 Bucket Cylinder 18 (18a, 18b, 18c, 18d) Wheel 20 Bucket 25 Chopper 26 Thermal Resistor 27 Exhaust System 27a throttle device 31 gearbox 32 lockup clutch 33 transmission 34 transmission clutch 41, 42, 43, 44 RPM sensor 100 controller 200 wheel loader 201 lift arm

Claims (5)

An engine, a generator for generating power by the power of the engine, a generator motor driven by the power supplied from the generator, a transmission for transmitting the power of the engine or the generator motor to the wheels, the engine and the transmission A lock-up clutch provided between them, a hydraulic circuit driven by the motive power of the engine, an engine drive mode for driving the wheels by the motive power of the engine, and the generator motor functioning as a motor; A control device for switching a drive mode between the motor drive mode for driving the wheels by the
The controller is
At the time of shifting of the transmission, the lockup clutch is released to switch the drive mode to the motor drive mode, and a load is generated on the hydraulic circuit to reduce the number of revolutions of the engine.
The lockup clutch is engaged to switch the drive mode from the motor drive mode to the engine drive mode when the rotation speed of the transmission input shaft matches the rotation speed of the output shaft of the engine. Work vehicle to be. It is a work vehicle according to claim 1, and
And a thermal resistor electrically connected to the generator,
The controller is
A working vehicle characterized by reducing a rotational speed of the engine by generating a load by converting power of the engine into heat in the thermal resistor via the generator. It is a work vehicle according to claim 1, and
The transmission has a transmission clutch,
The controller is
A work vehicle characterized by reducing the rotational speed of the engine by generating a load by engaging the transmission clutch and accelerating the generator motor. It is a work vehicle according to claim 1, and
The engine exhaust line is provided with a throttle device for operating an exhaust brake,
The controller is
A work vehicle characterized by reducing the rotational speed of the engine by generating a load by operating the exhaust brake. It is a work vehicle according to claim 1, and
The generator has a mechanism that causes the internal resistance to consume power by shorting the three phases,
The controller is
A working vehicle characterized by reducing the number of revolutions of the engine by consuming power by the mechanism and generating a load.