JP2013117098A - Regenerative controller of work vehicle and regenerative control method of work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a regenerative controller of a work vehicle for not making an operator have a feeling of incompatibility or anxiety on an operation by preventing a difference from being generated in movement performances between the regenerative time of storing kinetic energy in an accumulator as hydraulic energy and the non-regenerative time.SOLUTION: The regenerative controller of a work vehicle includes: an HST circuit 10 for which an HST pump 2 connected to a drive source 1 and an HST motor 3 connected to a wheel 25 are closed by HST pipelines 4A, 4B; a regenerative accumulator 8 for converting the kinetic energy during deceleration to the hydraulic energy, storing, and supplying the stored hydraulic energy to a regenerative motor 7 connected to the drive source 1; a regenerative valve 9 for connecting the HST pipelines 4A, 4B and the regenerative accumulator 8; and a controller 20 for variably controlling a motor capacity so that brake torque is the same for the regenerative time and the non-regenerative time in the regenerative time of opening the regenerative valve 9 and storing regenerative hydraulic energy in the regenerative accumulator 8.

Description

  The present invention relates to a regenerative control device for a work vehicle that does not cause a sense of incongruity and anxiety in operation to an operator so that there is no difference in regenerative and non-regenerative motion performance when kinetic energy is stored as hydraulic energy in an accumulator. The present invention also relates to a regeneration control method for work vehicles.

  Conventionally, construction machines such as wheel loaders equipped with HST (Hydrostatic Transmission: hydrostatic power transmission device), work machines such as agricultural machines and industrial vehicles are known. A work vehicle equipped with an HST has a configuration in which a hydraulic pump and a hydraulic motor are communicated with each other through a closed hydraulic circuit and travels with the power of the hydraulic motor. Recently, an engine, a hydraulic pump, and a hydraulic motor can be driven with an optimal output, pump capacity, and motor capacity by electronic control technology to improve work efficiency and save fuel.

  On the other hand, in a work vehicle equipped with HST, the kinetic energy at the time of traveling deceleration is converted into hydraulic energy and stored, and the stored power is released to drive the power source in an auxiliary manner. Some reduce fuel consumption by reducing output.

  For example, in the one described in Patent Document 1, although not described in detail, the brake torque acting on the vehicle is adjusted by changing the capacity of the travel variable motor. Patent Document 1 discloses that the kinetic energy of a vehicle is regenerated as hydraulic energy and charged to the accumulator, and when the accumulator becomes full, the charging is stopped and the kinetic energy is heated by the service brake. It describes what selectively controls the release as energy.

Japanese Patent Laid-Open No. 55-6077

  However, in the above-described Patent Document 1, no consideration is given to the difference in the performance of the work vehicle between when the accumulator is charged with kinetic energy and when it is not charged. When there is a difference in exercise performance depending on the operator, there is a problem that the operator feels uncomfortable and uneasy about the operation. In particular, when the regeneration is stopped in the middle of deceleration of the work vehicle, since the change in the kinetic energy of the work vehicle is large, the change in the regenerative and non-regenerative changes causes a great change in the performance of the work vehicle that cannot be expected by the operator. .

  The present invention has been made in view of the above, and the operator feels uncomfortable in operation so that there is no difference in regenerative and non-regenerative motor performance when storing kinetic energy as hydraulic energy in the accumulator. An object of the present invention is to provide a work vehicle regenerative control device and a work vehicle regenerative control method that do not cause anxiety.

  In order to solve the above-described problems and achieve the object, a regenerative control device for a work vehicle according to the present invention includes a travel hydraulic pump coupled to a drive source and a travel hydraulic motor coupled to wheels. The hydraulic circuit closed by the working machine, the working machine driven by the working machine hydraulic pump coupled to the driving source, the kinetic energy at the time of deceleration is converted into hydraulic energy and accumulated, and the accumulated hydraulic energy is stored in the driving source. A regenerative accumulator for supplying to a combined regenerative motor, a regenerative valve connecting between the pipe line and the regenerative accumulator, and a regenerative hydraulic energy stored in the regenerative accumulator by opening the regenerative valve to regenerate And a control unit that variably controls the motor capacity so that the brake torque at the time and the non-regeneration time are the same.

  According to the regenerative control device for a work vehicle according to the present invention, in the above invention, the control unit is configured to generate one target brake torque out of a plurality of target brake torques determined in advance according to a traveling state during regeneration. The motor capacity is variably controlled so that the difference from the current brake torque becomes small.

  In the regenerative control device for a work vehicle according to the present invention, in the above invention, the target brake torque is a combination of one or more of an accelerator operation amount, a brake operation amount, a work implement height, and a work implement raising speed. The correction is based on the measured value.

  Also, the regenerative control device for a work vehicle according to the present invention is the above-described invention, wherein the control unit is configured such that the drive source rotation speed or the drive source output is less than or equal to a first threshold value during regeneration and / or the work implement. When the height is equal to or higher than the second threshold value or the work implement raising speed is equal to or lower than the third threshold value, control for increasing the physical supply amount for driving source output and / or increasing the capacity of the traveling hydraulic pump is performed. Features.

  The regenerative control device for a work vehicle according to the present invention is characterized in that, in the above invention, the control unit starts regenerative control based on an accumulator pressure and / or an absolute value of a traveling speed. To do.

  In the regenerative control device for a work vehicle according to the present invention as set forth in the invention described above, the control unit is configured to match / mismatch the forward / reverse lever position and the traveling direction, and / or the accelerator operation amount, and / or the brake operation. Regenerative control is started based on the amount.

  The regenerative control device for a work vehicle according to the present invention is characterized in that, in the above-described invention, the regenerative control is started based on the physical supply amount for driving source output and / or the rotational speed of the driving source. To do.

  Further, the regenerative control device for a work vehicle according to the present invention is characterized in that, in the above invention, the control unit ends the regenerative control based on an accumulator pressure and / or an absolute value of a traveling speed. To do.

  In the regenerative control device for a work vehicle according to the present invention as set forth in the invention described above, the control unit regenerates based on the coincidence / mismatch between the forward / reverse lever position and the traveling direction and / or the accelerator operation amount. Control is terminated.

  Further, the regenerative control device for a work vehicle according to the present invention is characterized in that, in the above invention, the regenerative control is terminated based on the physical supply amount for driving source output and / or the rotational speed of the driving source. To do.

  The work vehicle regenerative control method according to the present invention includes a hydraulic circuit in which a traveling hydraulic pump coupled to a drive source and a traveling hydraulic motor coupled to a wheel are closed by a pipeline, and coupled to the drive source. A working machine driven by the working machine hydraulic pump, a regenerative accumulator that converts the kinetic energy at the time of deceleration into hydraulic energy, accumulates it, and supplies the accumulated hydraulic energy to a regenerative motor coupled to the drive source; A regenerative control method for a work vehicle comprising a regenerative valve for connecting between the pipe line and the regenerative accumulator, wherein the regenerative hydraulic energy is accumulated in the regenerative accumulator by opening the regenerative valve, The motor capacity is variably controlled so that the brake torque at the time of regeneration is the same as that at the time of non-regeneration.

  Further, the regenerative control method for a work vehicle according to the present invention is the above-described invention, wherein the accumulator pressure and / or the absolute value of the traveling speed, and / or the coincidence / non-coincidence between the forward / reverse lever position and the traveling direction, and Based on the accelerator operation amount and / or the brake operation amount and / or the physical supply amount for the drive source output and / or the drive source rotation speed, the regeneration control is started or ended. Features.

  According to this invention, the motor capacity is variably controlled so that the brake torque is the same during regeneration and during non-regeneration during regeneration when the regeneration valve is opened and regenerative hydraulic energy is stored in the regenerative accumulator. The regenerative accumulator stores no kinetic energy as hydraulic energy, so that there is no difference between the regenerative and non-regenerative kinetic performances. As a result, the operator does not feel uncomfortable or uneasy about the operation.

FIG. 1 is a diagram illustrating an overall configuration of a wheel loader that is an example of a work vehicle. FIG. 2 is a diagram showing a circuit configuration centered on the HST circuit of the wheel loader. FIG. 3 is an overall flowchart showing a regeneration control processing procedure by the controller. FIG. 4 is a detailed flowchart showing the regeneration start determination processing procedure in step S11. FIG. 5 is a detailed flowchart showing the regenerative braking torque control processing procedure in step S13. FIG. 6 is a detailed flowchart showing the regeneration end determination processing procedure shown in step S14. FIG. 7 is a time chart showing an example of regenerative control during a specific shuttle operation. FIG. 8 is a time chart showing another example of regenerative control during a specific shuttle operation. FIG. 9 is a flowchart showing a regenerative braking torque control processing procedure according to the first modification. FIG. 10 is a flowchart illustrating a regeneration start determination processing procedure according to the second modification. FIG. 11 is a flowchart illustrating a regeneration start determination processing procedure according to the third modification. FIG. 12 is a flowchart illustrating a regeneration end determination processing procedure according to the fourth modification. FIG. 13 is a flowchart illustrating the regeneration end determination processing procedure according to the fifth modification. FIG. 14 is a flowchart illustrating a regeneration end determination processing procedure according to the sixth modification.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

[overall structure]
FIG. 1 is a diagram illustrating an overall configuration of a wheel loader 50 that is an example of a work vehicle. FIG. 2 is a diagram showing a circuit configuration centered on the HST circuit of the wheel loader 50. As shown in FIG. 1, the wheel loader 50 includes a vehicle body 51, a lift arm 52 attached to the front portion of the vehicle body 51, a bucket 53 attached to the tip of the lift arm 52, a bell crank 56, and the like. A vehicle, four wheels 54 for rotating the vehicle body 51 while supporting the vehicle body 51, and a cab (cab) 55 mounted on the upper portion of the vehicle body 51.

  The lift arm 52 is a link member for lifting the bucket 53 attached to the tip, and moves up and down as the working machine hydraulic cylinder (lift cylinder) 19a connected to the lift arm 52 expands and contracts. The bucket 53 is attached to the tip of the lift arm 52, and further, the working machine hydraulic cylinder (bucket cylinder) 19b connected via a link member called a bell crank 56 is extended and retracted to be dumped and tilted. .

[Circuit configuration]
The wheel loader 50 is mounted with the circuit configuration shown in FIG. That is, by driving the wheel 54 by driving the HST motor (travel hydraulic motor) 3 with hydraulic fluid discharged from the HST pump (travel hydraulic pump) 2 driven by the drive source 1 such as an engine or a motor. An HST circuit 10 for running the wheel loader 50 is included. The HST circuit 10 forms a hydraulic circuit that is closed by connecting the HST pump 2 and the HST motor 3 by an HST line 4 constituted by HST lines 4A and 4B.

  In addition to the HST pump 2, a work machine pump 5, a charge pump 6, and a regenerative motor 7 are coupled to the drive shaft of the drive source 1. The work machine pump 5 supplies hydraulic oil to the control valve 18 to expand and contract the work machine hydraulic cylinders 19a and 19b. The charge pump 6 is connected to the tank via a low pressure relief valve 11. Further, the charge pump 6 supplies hydraulic oil to the HST pipe lines 4A and 4B that are in a low pressure state via the check valves 12A and 12B, respectively.

  The regenerative motor 7 is a pump that is rotationally driven by hydraulic energy accumulated in the regenerative accumulator 8. The regenerative valve 9 is “open” in the regenerative control mode, and the high-pressure hydraulic oil from the HST pipe lines 4A and 4B is accumulated in the regenerative accumulator 8 as hydraulic energy via the check valves 13A and 13B. That is, in the regenerative control mode, the kinetic energy from the wheel 54 due to traveling deceleration or the like is converted into hydraulic energy through the HST motor 3 and the HST pipe lines 4A and 4B, and this hydraulic energy is converted into the check valves 13A and 13B and It accumulates in the regenerative accumulator 8 via the regenerative valve 9. The hydraulic energy accumulated in the regenerative accumulator 8 is supplied to the regenerative motor 7 and assists the rotation of the rotation shaft of the drive source 1. The case where hydraulic energy is accumulated in the regenerative accumulator 8 is when the high-pressure side pipe pressure of the HST pipe lines 4A and 4B is larger than the pressure of the regenerative accumulator 8. The regenerative motor 7 is driven until the hydraulic energy accumulated in the regenerative accumulator 8 is exhausted, but when the hydraulic energy accumulated in the regenerative accumulator 8 is exhausted, oil is supplied from the tank via the check valve 14 to the inlet of the regenerative motor 7. Works to inhale to the side. When the regenerative control mode is not set, the regenerative valve 9 is “closed”, and the high-pressure hydraulic oil from the HST pipe lines 4A and 4B passes through the check valves 13A and 13B and the high-pressure relief valve 14 and further passes through the check valves 12A and 12B. The hydraulic fluid is supplied to the HST pipe lines 4A and 4B in the low pressure state.

  The controller 20 controls the driving of the driving source 1 based on the detection results of the forward / reverse lever sensor 21, the accelerator opening sensor 22, the brake opening sensor 23, and the rotation speed of the driving source 1. Further, the controller 20 controls the control unit valve 18 based on the detection result of the work implement lever sensor 24 to control the drive of the work implement hydraulic cylinders 19a and 19b. Further, the controller 20 controls the swash plate 2C of the HST pump 2 and the swash plate 3C of the HST motor 3 based on the pressures of the HST pressure sensors 2A and 2B for detecting the pressures of the HST pipe lines 4A and 4B, respectively. Control the capacity and motor capacity respectively.

  In particular, the controller 20 controls the opening and closing of the regenerative valve 9 based on the accumulator pressure of the regenerative accumulator 8 detected by the pressure sensor 8a, the traveling speed detected by the speed sensor 25, and the like, and the hydraulic energy to the regenerative accumulator 8 And the motor capacity of the HST motor 3 is variably controlled so that the brake torque is the same during regeneration and during non-regeneration in the regeneration control mode in which the regeneration valve 9 is in the “open” state.

[Regenerative control]
Next, the regeneration control process by the controller 20 will be described with reference to a flowchart. FIG. 3 is an overall flowchart showing a regeneration control processing procedure by the controller 20. As shown in FIG. 3, the controller 20 first determines whether or not to start the regenerative control process in a state where the regenerative valve 9 is “closed” and whether to reopen the regenerative valve 9 or not. It is determined whether or not (step S11). Thereafter, in the process of step S11, it is determined whether or not the regenerative valve 9 is set to “open” (step S12). If the regenerative valve 9 is not set to “open” (step S12, No), step The process of S11 is repeated. On the other hand, when the regenerative valve 9 is set to “open” (step S12, Yes), the swash plate 3C of the HST motor 3 is changed so that the brake torque at the time of regeneration is the same as that at the time of non-regeneration. Then, a regenerative brake torque control process for changing the motor capacity is performed (step S13). Since the brake torque is proportional to the motor capacity and the brake pressure (absolute differential pressure of the HST pipes 4A and 4B), in order to make the brake torque the same during regenerative and non-regenerative, Since the brake pressure decreases, control is performed to increase the motor capacity corresponding to the decrease.

  Thereafter, it is determined whether or not the regenerative control for setting the regenerative valve 9 to the “open” state is terminated, that is, whether or not the regenerative valve 9 is “closed” (step S14). Thereafter, in the process of step S14, it is determined whether or not the regenerative valve 9 is set to “closed” (step S15). If the regenerative valve 9 is not set to “closed” (step S15, No), the regeneration is performed. The “open” state of the valve 9 is maintained, the process proceeds to step S13, and the regenerative brake torque control process is repeated. On the other hand, when the regenerative valve 9 is set to “closed” (step S15, Yes), the process proceeds to step S11, and the regeneration start determination process for determining whether to start the regeneration control is performed again.

  Here, with reference to the flowchart shown in FIG. 4, the regeneration start determination processing procedure of step S11 will be described. As shown in FIG. 4, first, the controller 20 determines whether or not the forward / reverse lever position matches the traveling direction based on the detection result of the forward / reverse lever sensor 21 and the detection result of the travel speed sensor 25. Judgment is made (step S101). As shown in FIG. 7A, the forward / reverse lever sensor 21 detects forward (F), neutral (N), and reverse (R) states. Further, the traveling speed sensor 25 detects forward (F) if positive and reverse (R) if negative based on the sign of the traveling speed. Here, when the forward / reverse lever position does not match the traveling direction, a sudden deceleration state occurs. For example, the forward / reverse lever operation at time t1 in FIG. 7 corresponds to this sudden deceleration. Such reverse operation of the forward / reverse lever is called “shuttle operation”, and in V-shaped work such as a wheel loader, the operation is often performed only by the shuttle operation without performing the accelerator operation or the brake operation. Here, in the case of rapid deceleration where the forward / reverse lever position does not coincide with the traveling direction (step S101, No), the process proceeds to step S103.

  On the other hand, when the forward / reverse lever position coincides with the traveling direction (Yes in step S101), the accelerator operation amount is further set to the threshold value based on the detection results of the accelerator opening sensor 22 and the brake opening sensor 23. And / or whether or not the brake operation amount is greater than or equal to a threshold value is determined (step S102). That is, it is determined whether or not the vehicle is in a deceleration state. If the accelerator operation amount is less than the threshold and / or the brake operation amount is greater than or equal to the threshold (step S102, Yes), the process proceeds to step S103. On the other hand, if the accelerator operation amount is less than the threshold value and / or the brake operation amount is not greater than or equal to the threshold value (No in step S102), the present process is terminated and the regenerative valve 9 is kept in the “closed” state.

  Thereafter, in step S103, based on the detection result of the pressure sensor 8a, it is determined whether or not the accumulator pressure of the regenerative accumulator 8 is equal to or lower than a threshold value, that is, whether or not there is an ability to store regenerative hydraulic energy (step S103). S103). If the accumulator pressure is not less than or equal to the threshold value (No at Step S103), since there is no regeneration effect, the “closed” state of the regeneration valve 9 is maintained and the process returns.

  On the other hand, if the accumulator pressure is equal to or lower than the threshold (step S103, Yes), it is further determined based on the detection result of the travel speed sensor 25 whether or not the absolute value of the travel speed is equal to or greater than the threshold (step). S104). When the absolute value of the traveling speed is less than the threshold value, the hydraulic energy that can be regenerated is reduced. If the absolute value of the traveling speed is equal to or greater than the threshold value (Yes at Step S104), the regenerative valve 9 is set to the “open” state (Step S105) to perform the regeneration control, and the process returns to Step S11. On the other hand, when the absolute value of the traveling speed is not equal to or greater than the threshold value (No at Step S104), the “reclosed” state of the regenerative valve 9 is maintained, and the process returns to Step S11.

  That is, when the work machine is rapidly decelerating and has a capability of accumulating hydraulic oil in the regenerative accumulator 8, and there is a certain traveling speed, the regenerative valve 9 is opened and regenerative control is started. Yes.

  Next, the regenerative brake torque control processing procedure in step S13 will be described with reference to the flowchart shown in FIG. First, the controller 20 determines whether or not the forward / reverse lever position is neutral (N) (step S201). When the forward / reverse lever position is neutral (step S201, Yes), the process proceeds to step S205, the target brake torque TC in the regenerative state is set, and the process proceeds to step S206.

  On the other hand, if the forward / reverse lever position is not neutral (step S201, No), it is further determined whether or not the forward / reverse lever position matches the traveling direction (step S202). If the forward / reverse lever position matches the traveling direction (step S202, Yes), the process proceeds to step S203, the target brake torque TA in this regenerative state is set, and the process proceeds to step S206. If the forward / reverse lever position does not match the traveling direction (No at Step S202), the process proceeds to Step S204, the target brake torque TB in the regenerative state is set, and the process proceeds to Step S206. The target brake torques TA, TB, and TC are values set in advance corresponding to the traveling states classified according to the determination results of steps S201 and S202. Although the magnitude varies depending on the sudden deceleration state, etc., the values become smaller in the order of target brake torque TB → TA → TC.

  At this stage, the target brake torque in steps S203 to S205 is corrected by taking into account the values of the accelerator operation amount and the brake operation amount, as well as the bucket height and bucket lifting speed of the work implement. Also good. By this correction, finer brake torque control can be performed.

  Thereafter, the motor capacity of the HST motor 3 is variably controlled so that the current brake torque is the same as the set target brake torque (step S206), and the process returns to step S13. The current brake torque is obtained from the value obtained by multiplying the absolute differential pressure between the HST line 4A pressure detected by the HST line sensors 2A and 2B and the HST line 4B pressure by the current motor capacity. .

  Here, the regeneration end determination processing procedure shown in step S14 will be described with reference to the flowchart of FIG. First, the controller 20 determines whether or not the accumulator pressure is equal to or less than a threshold value (step S301). If the accumulator pressure is not less than or equal to the threshold value (step S301, No), the regeneration valve 9 is set to “closed” (step S303) in order to end the regeneration control, and the process returns to step S14.

  On the other hand, when the accumulator pressure is equal to or lower than the threshold value (step S301, Yes), it is further determined whether or not the absolute value of the traveling speed is equal to or higher than the threshold value (step S302). If the absolute value of the traveling speed is not equal to or greater than the threshold (No at Step S302), the regenerative valve 9 is “closed” (Step S303), and the process returns to Step S14. If the absolute value of the traveling speed is equal to or greater than the threshold value (Yes in step S302), the process returns to step S14 while the regenerative valve 9 is kept “open”.

  That is, in this regeneration end determination processing, the ability to accumulate hydraulic oil in the regenerative accumulator 8 is substantially lost, and when there is substantially no regenerative hydraulic energy accumulation when the traveling speed is low, the regenerative valve 9 is set to “ It is set to “Close” to end the regenerative control.

[Specific examples of regenerative control]
7 and 8 are time charts showing examples of regenerative control during specific shuttle operations, respectively. FIG. 7 shows an example in which the regenerative control is basically started in a state where the forward / reverse levers do not match, and the regenerative control is ended in a state where the absolute value of the traveling speed is equal to or less than the threshold value. In FIG. 8, basically, the regenerative control is started in a state where the forward / reverse levers do not match, and the regenerative control is ended in a state where the accumulator pressure is equal to or less than the threshold value. FIGS. 7A and 8A show the traveling speed and the forward / reverse lever position, and FIGS. 7B and 8B show the regeneration control ON / OFF (opening and closing of the regeneration valve 9). 7 (c) and 8 (c) show the engine speed, and FIG. 7 (d) and FIG. 8 (d) show the accelerator operation amount and the brake operation amount. 8 (e) shows the HST line pressure, FIGS. 7 (f) and 8 (f) show the HST pump capacity and HST motor capacity, and FIGS. 7 (g) and 8 (g) show the accumulator. The internal gas pressure (accumulator pressure) and the accumulator gas capacity are shown, and FIG. 7 (h) and FIG. 8 (h) show the brake torque. In FIG. 7, the solid line indicates the case where the regeneration control according to the present embodiment is performed, and the broken line indicates the case where the regeneration control according to the present embodiment is not performed. In FIG. 8, a solid line indicates a case where the regeneration control according to the present embodiment is performed, and a two-dot chain line indicates a case where the regeneration control shown in FIG. 7 is performed. In FIGS. 7 and 8, from time t0 to t1, a slow reverse acceleration is performed. At time t1, the forward / reverse lever is reversely operated, and the vehicle is decelerated from time t1 to t2, and from time t2 to t3. A state in which the vehicle moves forward by reverse acceleration is shown, and after time t3, a case where the vehicle is in a forward steady state is shown.

  In FIG. 7, at the time point t1, the forward / reverse lever position becomes inconsistent with the traveling direction (FIG. 7 (a)), the accumulator pressure is not more than the threshold value Pmax (FIG. 7 (g)), and the absolute value of the traveling speed is also the threshold value Vth. As described above (FIG. 7A), the regenerative valve 9 shifts from the “closed” state to the “open” state (FIG. 7B), and regenerative control is started.

  At time t12, the accumulator pressure is equal to or lower than the threshold value Pmax (FIG. 7 (g)), and the absolute value of the traveling speed becomes less than the threshold value Vth (FIG. 7 (a)). The state shifts from the state to the “closed” state (FIG. 7B), and the regenerative control ends.

  During the regenerative control between this time point t1 and t12, the controller 20 uses the absolute difference between the HST pipe line 4B pressure and the HST pipe line 4A pressure as a brake pressure, and sets the brake pressure during regeneration to the brake pressure during non-regeneration. Corresponding to the increase (FIG. 7 (e)), the HST motor capacity is increased (FIG. 7 (f)). As a result, as shown in FIG. 7 (h), the time change of the brake torque is the same as that at the time of non-regeneration regardless of the time of regeneration and non-regeneration.

  As a result, the operator of the work vehicle does not have an unexpected sudden acceleration when moving from the regenerative mode to the non-regenerative mode, and can work without feeling uncomfortable or uneasy about the operation.

  On the other hand, in FIG. 8, since the accumulator pressure has exceeded the threshold value Pmax at time t13 as the end determination of the regenerative control (FIG. 8 (g)), the regenerative valve 9 is changed from “open” to “closed”, and the regenerative control ends. (FIG. 8B). Even in this case, as shown in FIG. 8 (h), the time change of the brake torque is the same as in the non-regenerative operation regardless of the regeneration time and non-regeneration time.

  In the above-described embodiment, the threshold value of the accumulator pressure is set to the maximum value Pmax. However, the threshold value is not limited to this, and may be a neighborhood value less than the maximum value Pmax.

[Modification 1]
When regenerative control is performed in the above-described embodiment, the engine (drive source) rotational speed is greatly decreased as the driving regeneration contradicts, and acceleration after deceleration may deteriorate. For this reason, in the first modification, control that does not affect the acceleration after deceleration is performed simultaneously.

  FIG. 9 is a flowchart showing a regenerative braking torque control processing procedure according to the first modification. As shown in FIG. 9, the controller 20 first determines whether or not the forward / reverse lever position is neutral (N) as in the regenerative braking torque control process shown in FIG. 5 (step S401). When the forward / reverse lever position is neutral (step S401, Yes), the process proceeds to step S405, the target brake torque TC in the regenerative state is set, and the process proceeds to steps S406, S411.

  On the other hand, if the forward / reverse lever position is not neutral (step S401, No), it is further determined whether or not the forward / reverse lever position matches the traveling direction (step S402). If the forward / reverse lever position coincides with the traveling direction (step S402, Yes), the process proceeds to step S403, the target brake torque TA in this regenerative state is set, and the process proceeds to steps S406, S411. If the forward / reverse lever position does not coincide with the traveling direction (No at Step S402), the process proceeds to Step S404, the target brake torque TB in the regenerative state is set, and the process proceeds to Steps S406 and S411. The target brake torques TA, TB, and TC are values set in advance corresponding to the traveling states classified according to the determination results of steps S401 and S402. Although the magnitude varies depending on the sudden deceleration state, etc., the values become smaller in the order of target brake torque TB → TA → TC.

  At this stage, the target brake torque in steps S403 to S405 is corrected by taking into account the values of the accelerator operation amount and the brake operation amount, as well as values such as the bucket height and bucket lifting speed of the work implement. Also good. By this correction, finer brake torque control can be performed.

  Thereafter, the process of step S406 and the process of step S411 are performed in parallel. First, in step S406, the motor capacity of the HST motor 3 is variably controlled so that the current brake torque becomes the same as the set target brake torque, and the process returns to step S13. The current brake torque is obtained from the value obtained by multiplying the absolute differential pressure between the HST line 4A pressure detected by the HST line sensors 2A and 2B and the HST line 4B pressure by the current motor capacity. .

  On the other hand, the engine injection amount control and the HST pump capacity control are performed in parallel with the brake torque control by the variable control of the motor capacity in step S406 described above. First, it is determined whether or not the engine speed or the engine output is below a threshold value (step S411). When the engine speed or the engine output is less than or equal to the threshold value (step S411, Yes), processing for increasing the fuel injection amount of the engine and / or increasing the HST pump capacity is performed (step S413), and step S13. Return to

  On the other hand, if the engine speed or the engine output is not less than the threshold (No in step S411), it is further determined whether or not the bucket height is equal to or greater than the threshold or the bucket raising speed is equal to or less than the threshold (step S412). The controller 20 acquires the bucket height and the bucket lifting speed based on the detection result of the posture sensor 17 of the work implement. When the bucket height is equal to or higher than the threshold value or the bucket raising speed is equal to or lower than the threshold value (step S412, Yes), the process proceeds to step S413 to increase the fuel injection amount of the engine and / or increase the HST pump capacity. And return to step S13. If the bucket height is not greater than the threshold value or the bucket raising speed is not less than the threshold value (step S412, No), the process directly returns to step S13.

[Modification 2]
In the second modification, as shown in FIG. 10, it is determined whether or not the fuel injection amount of the engine is equal to or less than a threshold value in the regeneration start determination process shown in FIG. 4 (step S505). Is equal to or less than the threshold (step S505, Yes), the regenerative valve 9 is set to “open” to perform regenerative control. The other steps S501 to S504 and S506 correspond to steps S101 to S104 and S105 shown in FIG.

  The reason for determining whether or not the engine fuel injection amount is less than or equal to the threshold value is that the engine fuel injection amount is almost zero in many shuttle operations.

  Instead of determining whether or not the fuel injection amount of the engine is equal to or less than the threshold value, it may be determined whether or not the temporal change in the fuel injection amount of the engine is negative (injection amount decrease).

[Modification 3]
In the third modification, as shown in FIG. 11, it is determined whether or not the engine speed is equal to or higher than a threshold value instead of the process of step S505 of the regeneration start determination process shown in FIG. 10 ( Step S605). Other steps S601 to S604 and S606 correspond to steps S501 to S504 and S506 shown in FIG.

  The reason for determining whether or not the engine speed is greater than or equal to the threshold value is that the engine speed may increase during a shuttle operation. This is because when the accelerator operation is performed, the engine speed is often higher than the engine speed corresponding to the accelerator operation amount.

  It should be noted that the elements of the above-described modifications 2 and 3 can be combined as appropriate, and determination can also be performed by combining each element with AND or OR.

[Modification 4]
Next, Modification 4 is a modification of the regeneration end determination process. As shown in FIG. 12, in this regeneration end determination process, it is further determined whether or not the engine speed is equal to or lower than a threshold value (step S703). If the engine speed is equal to or lower than the threshold value (step S703, Yes). Is configured to end the regenerative control by closing the regenerative valve 9. The other steps S701, S702, and S704 correspond to steps S301 to S303 shown in FIG.

[Modification 5]
In Modification 5 shown in FIG. 13, instead of step S703 in FIG. 12, it is determined whether the forward / reverse lever position matches the traveling direction and the accelerator operation amount is equal to or greater than the threshold (step S803). When the advance lever position coincides with the traveling direction and the accelerator operation amount is equal to or greater than the threshold value (step S803, Yes), the regenerative valve 9 is set to “closed” to terminate the regenerative control. Other steps S801, S802, and S804 correspond to steps S701, S702, and S704 shown in FIG.

  The reason why the forward / reverse lever position coincides with the traveling direction and the accelerator operation amount is greater than or equal to the threshold value is determined because there is a case where deceleration is interrupted and reacceleration is performed during deceleration.

[Modification 6]
In the sixth modification shown in FIG. 14, instead of step S <b> 803 in FIG. 13, it is determined whether or not the fuel injection amount of the engine is equal to or greater than the threshold (step S <b> 903), and the fuel injection amount of the engine is equal to or greater than the threshold. In the case (step S903, Yes), the regenerative valve 9 is “closed” to terminate the regenerative control. The other steps S901, S902, and S904 correspond to steps S801, S802, and S804 shown in FIG.

  The reason for determining whether or not the fuel injection amount of the engine is equal to or greater than the threshold value is that there is a case where deceleration is interrupted and reacceleration is performed during deceleration.

  It should be noted that the elements of the modified examples 4 to 6 described above can be combined as appropriate, and the determination can also be performed by combining each element with AND or OR. Also, an appropriate combination of each regeneration start determination process and regeneration end determination process is possible.

  In the regeneration start determination process, the regeneration valve 9 may be set to “open” only by the determination processes in steps S103 and S104 shown in FIG.

[Modification 7]
In addition, each threshold value (step S103, S301, S503, S603, S701, S801, S901) of the accumulator pressure in the regeneration start determination process and the regeneration end determination process of the above-described embodiment and modification examples 1 to 6 is a threshold value that is close to full. However, the present invention is not limited to this, and a threshold value Pth2 (Pth2 <Pth1) lower than the threshold value near full filling (Pth1) is set, and the regenerative valve 9 is opened as the current accumulator pressure approaches full filling. It is also possible to shorten the regeneration possible period. For example, in the determination process of step S104 in the regeneration start determination process shown in FIG. 4, it is determined whether or not the accumulator pressure is equal to or lower than the threshold value Pth1 and higher than the threshold value Pth2. In this case, as the threshold value Pth2 is made closer to the fully-filled value, the above-described regeneration possible period becomes shorter. The regenerative period is referred to as the accumulator pressure condition is only one condition for starting regeneration, and regeneration is performed only when other conditions are satisfied. In other words, the regeneration possible period can be changed and controlled by appropriately changing the above-described threshold value Pth2. Also in the regeneration end determination process, the regeneration possible end time can be advanced by changing and controlling the threshold value Pth2, and as a result, the regeneration possible period can be shortened.

DESCRIPTION OF SYMBOLS 1 Drive source 2 HST pump 2A, 2B HST pressure sensor 2C, 3C Swash plate 3 HST motor 4, 4A, 4B HST pipe line 5 Working machine pump 6 Charge pump 7 Regenerative motor 8 Regenerative accumulator 8a Pressure sensor 9 Regenerative valve 10 HST circuit DESCRIPTION OF SYMBOLS 11 Low pressure relief valve 12A, 12B, 13A, 13B, 14 Check valve 14 High pressure relief valve 17 Attitude sensor 18 Control valve 19a, 19b Hydraulic cylinder for work machines 20 Controller 21 Forward / reverse lever sensor 22 Accelerator opening sensor 23 Brake opening sensor 24 Working machine lever sensor 25 Travel speed sensor 54 Wheel

Claims (12)

A hydraulic circuit in which a traveling hydraulic pump coupled to a drive source and a traveling hydraulic motor coupled to a wheel are closed by a pipeline;
A work machine driven by a work machine hydraulic pump coupled to the drive source;
A regenerative accumulator that converts kinetic energy during deceleration into hydraulic energy and stores the energy, and supplies the stored hydraulic energy to a regenerative motor coupled to the drive source;
A regenerative valve for connecting between the conduit and the regenerative accumulator;
A controller that variably controls the motor capacity so that the brake torque at the time of regeneration is the same as that at the time of non-regeneration, during regeneration that opens the regeneration valve and accumulates regeneration hydraulic energy in the regeneration accumulator;
A regenerative control device for a work vehicle, comprising:   The control unit variably controls the motor capacity so that a difference between one target brake torque of a plurality of target brake torques determined in advance according to a traveling state and a current brake torque becomes small during regeneration. The regenerative control device for a work vehicle according to claim 1.   3. The target brake torque is corrected based on a combination value of any one or more of an accelerator operation amount, a brake operation amount, a work implement height, and a work implement raising speed. A regenerative control device for a work vehicle as described.   In the regeneration, when the drive source rotational speed or the drive source output is less than or equal to the first threshold and / or the work implement height is greater than or equal to the second threshold or the work implement raising speed is less than or equal to the third threshold during regeneration. 4. The control of the work vehicle according to claim 1, wherein control for increasing a physical supply amount for driving source output and / or increasing a capacity of the traveling hydraulic pump is performed. Regenerative control device.   The regenerative control of the work vehicle according to any one of claims 1 to 4, wherein the control unit starts the regenerative control based on an accumulator pressure and / or an absolute value of a traveling speed. apparatus.   The control unit starts regenerative control based on coincidence / non-coincidence between a forward / reverse lever position and a traveling direction and / or an accelerator operation amount and / or a brake operation amount. A regenerative control device for a work vehicle according to claim 1.   The regeneration control device for a work vehicle according to claim 5 or 6, wherein regeneration control is started based on a physical supply amount for driving source output and / or a driving source rotational speed.   The regenerative control of the work vehicle according to any one of claims 5 to 7, wherein the control unit ends the regenerative control based on an accumulator pressure and / or an absolute value of a traveling speed. apparatus.   9. The control unit according to claim 5, wherein the control unit ends the regenerative control based on coincidence / non-coincidence between a forward / reverse lever position and a traveling direction and / or an accelerator operation amount. A regenerative control device for a work vehicle according to claim 1.   The regenerative control of the work vehicle according to any one of claims 5 to 9, wherein the regenerative control is terminated based on a physical supply amount for driving source output and / or a rotational speed of the driving source. apparatus. A hydraulic circuit in which a traveling hydraulic pump coupled to a drive source and a traveling hydraulic motor coupled to a wheel are closed by a pipeline;
A work machine driven by a work machine hydraulic pump coupled to the drive source;
A regenerative accumulator that converts kinetic energy during deceleration into hydraulic energy and stores the energy, and supplies the stored hydraulic energy to a regenerative motor coupled to the drive source;
A regenerative valve for connecting between the conduit and the regenerative accumulator;
A regenerative control method for a work vehicle equipped with
In a work vehicle, the motor capacity is variably controlled so that the brake torque is the same during regeneration and during non-regeneration during regeneration when the regeneration valve is opened and regenerative hydraulic energy is accumulated in the regeneration accumulator. Regenerative control method.   Accumulator pressure and / or absolute value of travel speed and / or coincidence / mismatch of forward / reverse lever position and travel direction, and / or accelerator operation amount and / or brake operation amount, and / or The regenerative control method for a work vehicle according to claim 11, wherein the regenerative control is started or ended based on a physical supply amount for driving source output and / or a rotational speed of the driving source.

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