JP2866178B2 - Hydraulic drive for work vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a hydraulic drive device for a work vehicle represented by a hydraulic shovel, a wheel loader, etc., and more particularly, to an input torque of a hydraulic pump driven by a prime mover. The present invention relates to a hydraulic drive device for a work vehicle including a pump control unit that controls a pump discharge amount so as not to exceed a target torque.

[Conventional technology]

In a hydraulic drive device of a work vehicle represented by a hydraulic shovel, a wheel loader, or the like, for example, as described in WO90 / 08263, an input torque of a hydraulic pump driven by a prime mover is a target torque set in advance. A so-called horsepower limit control of a hydraulic pump is performed to control the pump discharge amount so as not to exceed the value and prevent overload of the prime mover. Also, for example, as described in JP-A-63-239327, a target rotation speed of a prime mover is set according to the operation amount of a travel pedal that controls the flow rate of pressure oil supplied to a travel motor, and is usually provided. It has also been practiced to control the prime mover using a target rotational speed set by the fuel lever and a larger value of the target rotational speed as a target rotational speed command value, as described in WO 90/08263.
This idea is also incorporated in the official gazette. By controlling the prime mover in this way, the target rotational speed of the fuel lever is set to a low speed during traveling, enabling the rotational speed of the prime mover to be controlled according to the operation amount of the travel pedal, ensuring excellent traveling operability. And the like.

On the other hand, in the horsepower limiting control of the hydraulic pump, as described in Japanese Utility Model Laid-Open No. 62-134902, two types of absorption torque (input torque) are prepared for traveling and working other than traveling. It has been proposed to control the pump discharge amount so that the absorption torque increases when only traveling is performed, and to control the pump discharge amount so that the absorption torque decreases when work other than traveling is performed. Accordingly, the absorbing horsepower is increased during traveling so that the work vehicle can travel at high speed, and the absorbing horsepower is reduced during operations other than traveling, thereby reducing the load on the working actuator.

[Problems to be solved by the invention]

However, in the horsepower limiting control described in WO90 / 08263, for example, as in the above-mentioned WO90 / 08263, no consideration is given to the difference in load characteristics between running and work other than running, and running is not considered. Because the pump discharge amount is controlled so that the same input torque is obtained regardless of work other than running, the torque characteristics depend on one of the work in terms of over torque, fuel efficiency, etc. There was a problem that the horsepower of the prime mover could not always be used effectively.

In particular, when the torque characteristics are set so that the pump input torque increases during work other than traveling in consideration of fuel efficiency,
In WO90 / 082632, as described above, the speed of the prime mover is controlled according to the operation amount of the travel pedal during traveling, so that the load immediately increases when the vehicle starts traveling, and as a result, the prime mover becomes stalled. I feel a little
There is a problem that the running performance is deteriorated, for example, it takes a long time to increase the rotation, the acceleration is deteriorated, the black smoke is emitted, and the running feeling is deteriorated.

In Japanese Utility Model Application Laid-Open No. 62-134902, two types of absorption torque characteristics, one for running and the other for running, are used. When the rotation speed of the prime mover is controlled in accordance with the operation amount of the travel pedal, there is a problem that the traveling performance is deteriorated as described above.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic drive device for a work vehicle that provides a pump input torque suitable for each of traveling and non-traveling work, can always effectively use the horsepower of a prime mover, and is excellent in traveling performance when traveling and starting. It is to be.

[Means for solving the problem]

To achieve the above object, according to the present invention, a prime mover, a variable displacement hydraulic pump driven by the prime mover, a traveling device driven by oil discharged from the hydraulic pump, A working actuator driven by the discharge oil, a traveling operation unit for controlling a flow rate of the pressure oil supplied to the traveling device, a first setting unit for setting a first target rotation speed of the prime mover,
The second drive of the prime mover is performed according to the operation amount of the traveling operation means.
Second setting means for setting the target rotation speed, third setting means for setting a target rotation speed command value based on the first and second target rotation speeds, and the target rotation speed command value. A motor control device for controlling the number of revolutions of the motor, and a pump control device for controlling a pump discharge amount so that an input torque of the hydraulic pump does not exceed a target torque. Determining means for determining whether the vehicle is in a working mode in which the working actuator is driven or in a running mode in which the traveling device is driven, and a first mode suitable for the working mode as a function of the target rotational speed command value. The pump input torque and the second pump input torque suitable for the traveling mode are set in advance, and when the determination unit determines that the work vehicle is in the work mode, The value of the first pump input torque corresponding to the target rotation speed command value at the time of the operation is selected as the target torque, and when it is determined that the work vehicle is in the traveling mode, the target rotation speed command value at that time The second corresponding to
And a switch setting means for selecting the value of the pump input torque and setting the target torque.

The switching setting means may set the second pump input torque as a function of the operation amount of the traveling operation means instead of the target rotation speed command value.

Preferably, the hydraulic drive device further includes forward / reverse switching means for setting forward, backward, or neutral of the work vehicle, and the determination means determines whether the forward / backward switching means is on the forward side or on the reverse side. When the switching operation is performed, it is determined that the vehicle is in the traveling mode, and otherwise, it is determined that the vehicle is in the work mode. Further, the determining means determines that the vehicle is in the traveling mode when the forward / reverse switching means is switched to either the forward side or the reverse side, and the traveling operating means is operated. In this case, it may be determined that the vehicle is in the work mode, or the forward / reverse switching means may be switched to either the forward side or the reverse side, and the traveling operation means may be operated, and the work actuator may be driven. If not, it may be determined that the vehicle is in the traveling mode, and otherwise, it may be determined that the vehicle is in the work mode.

Preferably, the first pump input torque is set to a relatively large value when the target rotational speed command value is in the intermediate region, and the second pump input torque is set to the target rotational speed command value. The value is set to be smaller than the value of the first pump input torque when the value is in the intermediate range.

More preferably, the maximum value of the second target rotation speed is set to be larger than the maximum value of the first target rotation speed, and the second target rotation speed corresponding to the maximum value of the second target rotation speed is set. The pump input torque is set smaller than the first pump input torque corresponding to the maximum value of the first target rotation speed.

[Action]

In the present invention configured as described above, when the determination means determines that the work vehicle is in the work mode, the first setting suitable for the work mode corresponding to the target rotation speed command value at that time is performed by the switching setting means. The value of the pump input torque is selected as the target torque, and the pump control means controls the pump discharge amount so that the pump input torque does not exceed the target torque. On the other hand, when the determination means determines that the work vehicle is in the traveling mode, the value of the second pump input torque suitable for the traveling mode corresponding to the target rotational speed command value at that time is selected as the target torque, and The control means controls the pump discharge amount so that the pump input torque does not exceed the target torque. Therefore, the discharge amount of the hydraulic pump is controlled so that the input torque is optimal for different load characteristics between traveling and work other than traveling, and the horsepower of the prime mover that drives the hydraulic pump can be effectively used to the maximum. By setting the pump input torque of No. 1 to be a relatively large value in the intermediate range of the target rotation speed command value, the pump input torque when the prime mover is at the intermediate rotation speed increases, and the fuel consumption in work other than traveling is reduced. Excellent economical operation becomes possible. Further, by setting the second pump input torque to a value smaller than the value of the first pump input torque in an intermediate region of the target rotation speed command value, it is possible to increase the operation amount of the traveling operation means at the start of traveling. Since the pump input torque does not immediately increase accordingly, the rotation speed of the prime mover increases responsively according to the operation amount of the traveling operation means, and good acceleration and traveling feeling are obtained, and black smoke is generated. Reduce.

Further, by setting the maximum value of the second target rotation speed to be larger than the maximum value of the first target rotation speed, the power of the prime mover during traveling can be increased, and the load on the prime mover increases when climbing a hill or the like. However, the vehicle can travel without greatly reducing the vehicle speed. On the other hand, the second target rotation speed corresponding to the maximum value of the second target rotation speed is
Is set smaller than the first pump input torque corresponding to the maximum value of the first target rotation speed, the output characteristic of the prime mover is generally such that the torque at medium speed is larger than the torque at high speed. Therefore, the first and second
In accordance with the setting of the maximum value of the target rotation speed, an efficient output can be obtained under various conditions during running and work other than running.

〔Example〕

 Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

First Embodiment First, an embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, a hydraulic drive device according to the present embodiment includes a prime mover, that is, an engine 1, a variable displacement hydraulic pump 2 driven by the engine 1, and a hydraulic pump 2
, A traveling actuator that is connected in parallel with each other via a discharge pipe 3 and main circuit lines 4 and 5 and that is driven by oil discharged from the hydraulic pump 2, ie, a traveling motor 6 and a working actuator such as a boom cylinder 7. The main circuit lines 4 and 5 between the hydraulic pump 2 and the actuators 6 and 7 have control valves 8 and 9 for controlling the flow rate and the direction of the hydraulic oil supplied from the hydraulic pump 2 to each actuator, respectively. Pressure compensating valves 10 and 11 are connected and upstream of the control valves 8 and 9 to keep the differential pressure across the control valves constant.

The switching of the traveling control valve 8 is controlled by pilot pressure transmitted to pilot lines 55a and 55b connected to a traveling pilot circuit 57. Pilot circuit for traveling
57 is a pilot pressure reducing valve 58 for generating a pilot pressure for instructing the driving speed of the traveling motor 6 by depressing the pedal 58A, and a forward / reverse switching valve for instructing forward, reverse and neutral traveling by manual operation of the operation lever 59a. 59, a pilot pump 60 for supplying pilot pressure oil, and a slow return valve 61.

The work control valve 9 is controlled to be switched by a pilot pressure transmitted to pilot lines 56a and 56b connected to the pilot pressure reducing valve 18. The pilot pressure reducing valve 18 generates a pilot pressure for instructing the driving speed and direction of the boom cylinder 7 by manually operating the operation lever 18A.

Load lines 12, 13 for detecting the load pressure of the actuators 6, 7 are connected to the control valves 8, 9, respectively.The load lines 12, 13 are further connected to a load line 14 via a high-pressure selection valve 19. I have. The load pressure on the high pressure side selected by the high pressure selection valve 19, that is, the maximum load pressure is led to the load line 14,
The load pressure detected in the load lines 12 and 13 is guided to the above-described pressure compensating valves 10 and 11, and the maximum load pressure detected in the load line 14 is guided to the unload valve 16 connected to the discharge pipe 3. The unload valve 16 operates in response to the pressure difference between the pump discharge pressure and the maximum load pressure, holds the pressure difference at a set value, and reduces the minimum discharge pressure of the hydraulic pump 2 when the control valves 8 and 9 are neutral. Hold.

A displacement angle sensor 70 for detecting a swash plate displacement angle (displacement volume) θs of the hydraulic pump 2;
Pressure sensor 71 for detecting discharge pressure Pp of hydraulic pump 2
And a position sensor 72 that detects the operation state of the operation lever 59a of the forward / reverse switching valve 59, a controller 74 that receives detection signals from these sensors and performs processing described below, and an electric signal output from the controller 74. It is controlled by a pump control device including a driven tilt angle control device 75. The tilt angle control device 75 has two solenoid valves 76 and 77 and a servo cylinder 78 in which the supply and discharge of pressure oil is controlled by switching the solenoid valves and the piston position is controlled. The swash plate tilt angle of the hydraulic pump 2 is controlled by controlling the position.

The engine 1 is preferably a diesel engine with a fuel injection device 30 with an all speed cabana,
The fuel injection device 30 has a governor lever 31. The number of rotations of the engine 1 is determined by a rotation sensor 73 for detecting the rotation speed.
A potentiometer 34 for detecting the amount of rotation of the governor lever 31, a pressure sensor 90 connected to the output line of the pilot pressure reducing valve 58, and detecting the pilot pressure of the pilot pressure reducing valve 58 corresponding to the operation amount of the traveling pedal 58a, By manually operating the fuel lever, a rotation speed setting device 32 for instructing a target rotation speed according to the displacement amount, and a detection signal from the sensors 73, 34, and 90 and a command signal from the rotation speed setting device 32 are input. The engine is controlled by an engine control device including the controller 74 for performing processing described later and the pulse motor 35 driven by an electric signal output from the controller 74. The pulse motor 35 rotates by an angle corresponding to the drive signal from the controller 74, and the governor lever
Turn 31 to adjust the fuel injection amount. In addition, the rotation speed setting device 32 includes a dial type (rotary potentiometer) and a push button type (up / down switch) outside the fuel lever.
For example, other operation means may be used.

FIG. 2 shows an example of a work vehicle on which the above hydraulic drive device is mounted. This work vehicle is a wheel-type hydraulic excavator. A traveling motor 6 drives a rear wheel 50 via a transmission 51 and a propeller shaft 52, and a boom cylinder 7 raises and lowers a boom 54 which is a part of a front attachment 53.

The controller 74 is constituted by a microcomputer or the like and has an arithmetic processing function for controlling the rotation speed of the engine 1 as shown by a block 80 in FIG. Block 80
In the block 40, a first signal corresponding to the displacement x is obtained from a command signal corresponding to the displacement x of the fuel lever of the rotation speed setting device 32.
The block 41 determines the second target rotation speed Nt according to the operation amount S from the detection signal of the pressure sensor 90 corresponding to the operation amount S of the pedal 58A. These target rotation speeds Nx and Nt are selected in the maximum value selection block 42, whichever is larger, and set as the target rotation speed command value Ny. The target rotation speed command value Ny is the displacement amount Nθ of the governor lever 31 detected by the potentiometer 34 in the servo control block 43.
The pulse motor 35 is controlled so that the rotation speed of the engine 1 matches the target rotation speed command value Ny.

In block 40, the displacement x and the first target rotation speed Nx
Is set such that the first target rotation speed Nx linearly increases from the idle rotation speed Ni as the displacement x increases. Also in block 41, the displacement x and the second
Is set so that the second target speed Nt increases linearly from the idle speed Ni as the pedal operation amount S increases.

Here, in block 40, the maximum value Nxmax of the first target rotational speed Nx is set lower than the maximum rotational speed that the engine 1 can output, and the maximum value Ntmax of the second target rotational speed Nt is the maximum rotational speed of the engine 1. As a result, the maximum value Ntmax of the target rotation speed Nt is larger than the maximum value Nxmax of the target rotation speed Nx.

The servo control block 43 performs the processing shown in the flowchart of FIG. That is, in steps S1 and S2, the detected value Nθ of the potentiometer 34 and the command value Ny from the block 42 are input, and in step S3, the detected value Nθ is compared with the command value Ny to determine the difference A = Nθ−Ny between the two. Calculate. Next, step S4
It is determined whether or not the absolute value of the difference A is equal to or greater than a predetermined value ΔA. The predetermined value ΔA is determined by the pulse motor 35 and the governor lever.
The value is set to a minute value corresponding to a control error due to backlash or the like of the link mechanism 37 or the like connecting the link 31. Next, when the absolute value of the difference A is less than the predetermined value ΔA, the procedure proceeds to step S5.
In step S6, when the pulse motor 35 is stopped, and when the difference A is equal to or more than the predetermined value ΔA, in steps S6, S7, and S8, a signal for driving the motor 35 in the forward rotation direction or the reverse rotation direction depending on whether the difference A is positive or negative Is output. That is, a drive signal for rotating the governor lever 31 in a direction to reduce the difference A is output. Then, step S1
And the above processing is repeated.

As described above, by detecting and feeding back the displacement amount Nθ of the governor lever 31, the displacement amount Nθ of the governor lever 31 is controlled in accordance with the change in the target rotation speed command value Ny, and the detected rotation amount Nθ matches the target rotation speed command value Ny. The rotation speed of the prime mover 1 is controlled in such a manner.

The controller 74 also has an arithmetic processing function for controlling the discharge amount of the hydraulic pump 2 as indicated by a block 81 in FIG. In block 81, the block 44 determines whether the work vehicle is in the traveling mode in which the operation motor 6 is driven or the boom cylinder 7 is driven based on the output signal of the sensor 72 which detects the operation state R of the operation lever 59A of the forward / reverse switching valve 59 It is determined whether or not the operation mode is set. In block 45, a target torque Tpo suitable for the working state at that time is determined from the determination signal from block 44 and the target rotation speed command value Ny obtained in the engine speed control block 80 described above, and block 4
In 6, the horsepower calculation is performed by multiplying the reciprocal 1 / Pp of the pump discharge pressure Pp obtained in the block 47 by the target torque Tpo,
At block 48, the obtained value θps is filtered by a primary delay element to obtain a target pump tilt angle θA for input torque limiting control. This target pump tilt angle θA is compared with the actual tilt angle feedback value θs detected by the tilt angle sensor 70 in the servo control block 49, and the tilt angle of the pump is adjusted so that the pump tilt amount matches the target pump tilt angle θA. The controller 75 is controlled.

Work state determination method and block in block 44
Details of the method of determining the target torque at 45 will be described with reference to FIGS.

In FIG. 6, the sensor 72 outputs an OFF signal when the operation lever 59A is at the neutral position, and outputs an ON signal when the operation lever 59A is at the forward or marching position. Block 44 turns off the traveling work determination flag F when the output of the sensor 72 is OFF.
(0), and it is determined that the operation mode is other than the traveling mode.
When the output of the sensor 72 is ON, the traveling work determination flag F is turned ON (1), and it is determined that the vehicle is in the traveling mode.

In a block 45 shown in FIG. 7, a block 50 includes a first pump input torque Tf suitable for a work mode other than the traveling mode.
Is set as a function of the target speed command value Ny,
In 51, a second pump input torque Tt suitable for the traveling mode is set as a function of the target rotation speed command value Ny. First
The pump input torque Tf immediately increases with an increase in the target rotation speed command value Ny, and is set to have a maximum value Tfmax in an intermediate region of the target rotation speed command value Ny. Second
Pump input torque Tt gradually increases with an increase in the target rotation speed command value Ny, does not yet reach the maximum value Ttmax in the intermediate region of the target rotation speed command value Ny, and the target rotation speed command value N
The relationship is set such that the maximum value Ttmax is reached only when y reaches the vicinity of the maximum.

Further, when the second target rotation speed Nt is selected as the target rotation speed command value Ny, the second pump input torque Tt corresponding to the maximum value Ntmax of Nt is the first target rotation speed Nx is the target rotation speed command. The relationship of Ttmax <Tfmax is set so as to be smaller than the first pump input torque Tf corresponding to the maximum value Nxmax of Nx when selected as the value Ny.

The block 45 includes a switch 52 that is switched by the traveling work determination flag F. When the flag F is OFF (0), the value of the first pump input torque Tf corresponding to the target rotation speed command value Ny at that time. Is selected as the target torque Tpo, and when the flag F is ON (1), the value of the second pump input torque Tt corresponding to the target rotation speed command value Ny at that time is selected and set as the target torque Tpo. That is, when it is determined that the work vehicle is in the work mode other than the traveling mode, the block 45 determines the first pump input torque Tf suitable for the work mode.
Is set as the target torque, and when it is determined that the work vehicle is in the traveling mode, the switching setting means for selecting the value of the second pump input torque Tf suitable for the traveling mode as the target torque is configured.

The servo control block 49 shown in FIG. 5 performs the processing shown in the flowchart of FIG. That is, step S11,
In step S12, the detection value θs of the tilt angle sensor 70 and the target value θA from the block 48 are input, and in step S13, the detection value θ
s is compared with the target value θA to calculate a difference Z = θA−θs between the two. Next, in step S14, it is determined whether the absolute value of the difference Z is equal to or greater than a predetermined value ΔZ. The predetermined value ΔZ is set to a minute value corresponding to a control error due to backlash or the like of a mechanism for connecting the actuator 78 and the hydraulic pump 2. Next, when the absolute value of the difference Z is less than the predetermined value ΔZ, in step S15, both the solenoid valves 76 and 77 are turned off.
If the difference Z is equal to or greater than the predetermined value ΔZ, one of the solenoid valves 76 and 77 is turned on in steps S16, S17 and S18 according to whether the difference Z is positive or negative. That is, when the difference Z is positive, the solenoid valve 77 is turned on to reduce the pump tilt angle, and when the difference Z is negative, the solenoid valve 76 is turned on.
Turn ON to increase the pump tilt angle. Then, the process returns to step S11, and the above processing is repeated.

As described above, by detecting the tilt angle θs of the hydraulic pump 2 and feeding it back, the pump tilt angle θs corresponding to the change of the target pump tilt angle θA is adjusted until the pump tilt angle θs becomes equal to the tilt angle θs. The turning angle is controlled.

In this embodiment configured as described above, when performing work other than driving to drive the boom cylinder 7, the fuel operation lever of the rotation speed setting device 32 is held at the maximum stroke position, and the engine speed is kept constant. Do the work. That is, in the engine control block 80 shown in FIG. 3, the target rotation speed Nxmax corresponding to the maximum displacement of the fuel lever is obtained in the block 40, and since the travel pedal 58A is not operated in the block 41, the idle rotation speed Ni is equivalent. The target rotation speed Nt is obtained, and in a block 42, the target rotation speed Nxmax is selected as the target rotation speed command value Ny. As a result, the engine 1 is controlled to have a constant speed that matches the target rotation speed Nxmax.

On the other hand, in the pump control block 81 shown in FIG. 5, since the forward / reverse switching valve 59 is in the neutral position, the traveling work determination flag F obtained in the block 44 becomes OFF (0),
In block 45, the first pump input torque Tf corresponding to the target rotation speed command value Ny of block 50, that is, the target rotation speed Nxma
The maximum pump input torque Tfmax corresponding to x is the target torque
A target pump tilt angle θA for input torque limiting control is obtained in blocks 46 and 48 from the target torque Tpo and the pump discharge pressure Pp. Thus, as described above, the swash plate of the hydraulic pump 2 is controlled to match the target pump tilt angle θA, and the pump tilt angle is controlled so that the input torque of the hydraulic pump 2 does not exceed the first pump input torque Tf. Is controlled.

When the fuel lever of the rotation speed setting device 32 is lowered to the intermediate stroke position, the target rotation speed Nx corresponding to the displacement x
Is similarly selected as the target rotation speed command value Ny, but also in this case, the maximum pump input torque Tfmax
Is obtained, the input torque of the hydraulic pump 2 becomes the maximum value.
The pump tilt angle is controlled so as not to exceed Tfmax.

As described above, in the operation mode other than the traveling, the maximum pump input torque Tfmax is obtained even at the target rotation speed Ny in the intermediate region.
Is set, the fuel efficiency of the engine 1 is improved during work other than traveling, and economical operation becomes possible.

When traveling by driving the traveling motor 6, the fuel lever of the rotational speed setting device 32 is lowered to the minimum stroke position, and the rotational speed of the engine 1 is controlled according to the operation amount S of the travel pedal 58A. That is, in a block 80 shown in FIG. 3, a target rotation speed Nx corresponding to the displacement amount x of the fuel lever is determined in a block 40, in this case, a target rotation speed Nx corresponding to the idle rotation speed Ni is determined. The target rotation speed Nt according to the operation amount S of 58A is determined. Block 42
In the target rotation speed Nt is selected as the target rotation speed command value Ny,
The rotation speed of the engine 1 is controlled to match the target rotation speed Nt.

At this time, the forward / reverse switching valve 59 has been switched to a position other than neutral, ie, forward or reverse, and the block 81 in FIG.
, The flag F obtained in the block 44 is ON (1)
In block 45, the value of the second pump input torque Tt of the block 51 corresponding to the above target rotation speed Ny is selected as the target torque Tpo, and the input torque of the hydraulic pump 2 exceeds this Tt by blocks 46 to 49. Not controlled.

At this time, in this embodiment, the second pump input torque Tt of the block 51 in FIG.
When the travel pedal 58A is depressed at the time of starting traveling, the target rotation speed Nt increases with an increase in the operation amount S in the block 41 of FIG. In response to this, as the target rotational speed command value Ny increases, the value of the pump input torque Tt that increases with the increase of the target rotational speed command value Ny in the blocks 51 and 52 in FIG. And the hydraulic pump 2 is controlled so that the input torque gradually increases. Therefore, the load on the engine 1 does not immediately increase when the vehicle starts running, and the engine 1 is controlled so that the rotation speed increases smoothly in accordance with the increase in the target rotation speed Ny. A feeling is obtained, and generation of black smoke is prevented.

When the travel pedal 58A is fully depressed, the target rotation speed command value Ny becomes the maximum value Ntmax of the target rotation speed Nt.
The maximum value Ntmax is the maximum value Nxmax of the target rotational speed Nx.
A larger horsepower can be obtained from the larger setting, so that the vehicle can travel without greatly lowering the vehicle speed even when the load on the prime mover increases, for example, when climbing a hill. Further, since the maximum value Ttmax of the second pump input torque corresponding to the maximum value Ntmax is set smaller than the maximum value Tfmax of the first pump input torque, when the maximum value Ntmax is equal to the target rotation speed command value Ny, Since the pump input torque decreases and the output characteristics of the prime mover generally become smaller at high speeds than at medium speeds, operation corresponding to the output characteristics becomes possible.

As described above, according to the present embodiment, the first pump input torque Tf suitable for the work mode is determined during work other than traveling, and the second pump input torque Tt suitable for the travel mode is determined during travel. The pump discharge rate is controlled so that the input torque conforms to the different load characteristics in each of the running and non-running operations, so that the horsepower of the prime mover can be used effectively to the maximum. Excellent economical driving is possible, and in the traveling mode, traveling performance is improved, such as good acceleration at the start of traveling and traveling feeling are obtained, and generation of black smoke is prevented.

Also, while running, a large horsepower can be obtained,
Efficient output can be obtained under various conditions during work other than running.

Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the pump input torque suitable for the traveling mode is directly obtained from the operation amount of the traveling pedal instead of the target rotation speed command value.

That is, in block 81A shown in FIG.
In 5A, the judgment signal F from block 44 and the target rotation speed command value
Travel pedal 58A detected by Ny and pressure sensor 90 in FIG.
Then, the target torque Tpo is determined from the operation amount S. Fig. 10 shows the details. In FIG. 10, a block 50 is the same as that of the first embodiment, and a block 51A sets a second pump input torque Tt suitable for the traveling mode as a function of the operation amount S of the traveling pedal 58A. The relationship between the manipulated variable S and the pump input torque Tt in the block 51A is substantially the same as the relationship between the target rotation speed command value Ny and the pump input torque Tt in the block 51 of the first embodiment.

 The configuration other than the above is the same as that of the first embodiment.

In the present embodiment configured as described above, since the operation is performed while the fuel lever of the rotation speed setting device 32 is held at the minimum stroke position during traveling, the target rotation speed command value Ny of the engine 1 is determined by the travel pedal 58A. Since the target rotation speed command value Ny and the operation amount S are proportional to each other depending on the operation amount S, the pump input torque Tt suitable for the traveling mode can be obtained from the operation amount S in the same manner as in the first embodiment. it can. Therefore, according to this embodiment, the same effect as that of the first embodiment can be obtained.

Third Embodiment A third embodiment of the present invention will be described with reference to FIGS. In this embodiment, the working state of the vehicle is determined using signals other than the switching signal of the forward / reverse switching valve.

That is, in FIG. 11, in block 44A, the operation state Pr of the travel pedal 58 is input in addition to the operation state R of the operation lever 59A of the forward / reverse switching valve 59, and the traveling motor 6 drives the work vehicle from these. It is determined whether the vehicle is in the traveling mode or the work mode in which the boom cylinder 7 is driven.

FIG. 12 shows the details of the determination. Traveling pilot valve 58
A pressure sensor 85 for detecting the secondary pressure is provided on the output side of
Operating state P of whether or not travel pedal 58A is depressed
Detect r. In block 44A, the forward / reverse switching valve 59
AND of the operation state R of the traveling pedal 58A and the operation state Pr of the traveling pedal 58A to determine whether the operation mode is the traveling mode or the other working mode. If the forward / reverse switching valve 59 is switched to the forward or reverse position and the secondary pressure of the traveling pilot valve 58 rises, the traveling work determination flag F is turned ON (1), it is determined that the vehicle is in the traveling mode, and In this case, the traveling work determination flag is set to OFF (0), and it is determined that the vehicle is in a work mode other than traveling.

According to the present embodiment, even if work other than traveling is performed with the forward / reverse switching valve 59 switched to the forward or reverse position, the traveling mode is not determined unless the traveling pedal 58A is depressed. Work modes other than the above can be determined more accurately.

An embodiment of another determination method will be described with reference to FIGS. 11 and 13. In FIG. 11, in block 44B, in addition to the operation state R of the operation lever 59A of the forward / reverse switching valve 59 and the operation state Pr of the traveling pedal 58, the operation of the operation lever 18b of the pilot valve 18 with respect to the direction control valve 9 of the boom 7 is performed. The state Pb is input, and it is determined from these whether the work vehicle is in the drive mode in which the drive motor 6 is driven or in the work mode in which the boom cylinder 7 is driven.

FIG. 13 shows the details of the determination. A pressure sensor 86 is provided on the output side of the pilot valve 18 of the boom 7 to detect the secondary pressure, and detects an operation state Pb as to whether the operation lever 18A is operated. In block 44B, the operation state R of the forward / reverse switching valve 59 and the operation state Pr of the travel pedal 58A are determined.
AND with the operation state Pb of the operation lever 18A to determine whether the operation mode is the traveling mode or the other operation mode. In this case, the forward / reverse switching valve 59 is switched to the forward or reverse position, the secondary pressure of the traveling pilot valve 58 rises, and if the secondary pressure of the operation pilot valve 18 does not rise, the traveling work determination flag F is turned ON (1 ), And determines that the vehicle is in the traveling mode. Otherwise, the traveling work determination flag is turned off (0).
And it is determined that the operation mode is other than the traveling mode.

According to the present embodiment, when the forward / backward switching valve 59 is switched to the forward or reverse position, and the traveling pedal 58A is depressed to operate while operating the operation lever 18A to perform the work by the boom, the work other than the traveling is performed. Since it is determined that the vehicle is in the mode, the operation by the boom can be economically performed by using the pump input torque suitable for the operation other than the traveling.

Others In the above embodiment, the operation amount S of the travel pedal 58A is detected by the pressure sensor 90. However, as shown in FIG. 14, a potentiometer 87 may be provided on the travel pedal 58A to detect mechanically. In addition, the operation state Pr of the travel pedal and the operation state of the operation lever 18A of the boom are also detected by the pressure sensor, but a limit switch or the like that can directly contact the travel pedal or the travel lever is provided, and even if mechanical detection is performed. good.

Further, in the above embodiment, the larger value of the first and second target rotation speeds Nx and Nt was selected in the block 42 shown in FIG. 3, but as described above in the block 42A of FIG. Using the traveling work determination flag F, the flag F is OFF (0)
, The first target speed Nx is selected, and the flag F is turned ON.
In the case of (1), a switch function for selecting the second target rotation speed Nt may be used. In this case, the same effect as described above can be obtained.

Although several embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made.

〔The invention's effect〕

According to the present invention, the first pump input torque suitable for the work mode is determined when the vehicle is in the work mode other than the traveling mode, and the second pump input torque suitable for the travel mode is determined when the vehicle is in the travel mode. The pump discharge rate is controlled so that the input torque conforms to the different load characteristics for both running and non-running work, maximizing the effective use of horsepower of the prime mover, and fuel efficiency in work modes other than running. In the driving mode, the driving performance can be improved. For example, in the driving mode, good acceleration and driving feeling at the start of driving can be obtained, and generation of black smoke can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic view of a hydraulic drive device for a work vehicle according to an embodiment of the present invention, FIG. 2 is a side view of a wheel type hydraulic shovel as an example of a work vehicle, and FIG. 3 is an engine of a controller. FIG. 14 is a block diagram showing a control function, and FIG.
FIG. 5 is a flowchart of the servo control of the engine speed in the engine control. FIG. 5 is a block diagram showing a pump control function of the controller. FIG. 6 is a block diagram showing details of a work state determination block. FIG. 7 is a block diagram showing details of determination of a target torque, FIG. 8 is a flowchart of servo control of a pump tilt angle, and FIG. 9 is a pump control function according to a second embodiment of the present invention. FIG. 10 is a block diagram showing details of the work state determination block, and FIG.
FIG. 11 is a block diagram showing a pump control function according to a third embodiment of the present invention, FIG. 12 is a block diagram showing details of the work state determination block, and FIG. FIG. 4 is a block diagram showing details of a block,
FIG. 14 is a diagram showing another embodiment for detecting the operation amount of the travel pedal, and FIG. 15 is a block diagram showing a modification of the engine control function of the controller. DESCRIPTION OF SYMBOLS 1 ... Engine (motor) 2 ... Hydraulic pump 6 ... Travel motor (travel device) 7 ... Boom cylinder (working actuator) 32 ... Rotational speed setting device (first setting means) 35 ... … Pulse motor (motor control means) 58… Pilot valve pressure valve (operating means for traveling) 58A… Traveling pedal (same) 59 …… Forward / reverse switching valve 74 …… Controller 75 …… Tilt angle control device (pump control) Means 40 Block (first setting means) 41 Block (second setting means) 42 Block (third setting means) 43 Block (motor control means) 81 Block (pump) Control means) 44; 44A; 44B... Block (judgment means) 45; 45A... Block (switch setting means) Nx... First target speed Nθ... Second target speed Ny. Command value Tf: First pump input torque Tt: No. Pump input torque Tpo ...... target torque S ...... travel pedal operation amount F ...... autonomous operating determination flag of

Continuation of the front page (72) Inventor Seiji Tamura 650, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (56) References JP-A-62-160333 (JP, A) JP-A-63-239327 ( JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) E02F 9/22

Claims (7)

(57) [Claims] A motor; a variable displacement hydraulic pump driven by the motor; a traveling device driven by oil discharged from the hydraulic pump; and a work apparatus driven by oil discharged from the hydraulic pump. An actuator,
Traveling operation means for controlling the flow rate of the pressure oil supplied to the traveling device, first setting means for setting a first target rotation speed of the motor, and operation amount of the traveling operation means. Second setting means for setting a second target speed of the prime mover; third setting means for setting a target speed command value based on the first and second target speeds; Hydraulic drive for a work vehicle, comprising: a motor control means for controlling the number of revolutions of the prime mover so as to be a number command value; and a pump control means for controlling a pump discharge amount so that an input torque of the hydraulic pump does not exceed a target torque. A determination means for determining whether the work vehicle is in a work mode in which the work actuator is driven or in a work mode in which the travel device is driven; and a work as a function of the target rotation speed command value. The first pump input torque suitable for the driving mode and the second pump input torque suitable for the traveling mode are set in advance, and when the determination means determines that the work vehicle is in the work mode, A value of the first pump input torque corresponding to a target rotation speed command value is selected and set as the target torque, and when it is determined that the work vehicle is in the traveling mode, the value corresponds to the target rotation speed command value at that time And a switch setting means for selecting the value of the second pump input torque to be set as the target torque. 2. The hydraulic drive system for a work vehicle according to claim 1, wherein said switching setting means replaces said second pump input torque with said target rotational speed command value and reduces the amount of operation of said travel operating means. A hydraulic drive device for a work vehicle, which is set in advance as a function. 3. The hydraulic drive system for a work vehicle according to claim 1, further comprising forward / reverse switching means for setting forward, backward, or neutral of the work vehicle, wherein said determination means determines whether said forward / backward change means is on the forward side. A hydraulic drive device for a work vehicle, wherein a drive mode is determined when a switching operation is performed to one of a reverse side and a work mode otherwise. 4. The hydraulic drive system for a work vehicle according to claim 1, further comprising forward / reverse switching means for setting forward, backward or neutral of the work vehicle, wherein said determination means determines whether said forward / backward travel means is on the forward side. A work vehicle characterized in that it is determined that the vehicle is in the traveling mode when the vehicle is switched to any one of the reverse and the traveling operation means is operated, and otherwise it is determined that the vehicle is in the working mode. Hydraulic drive. 5. The hydraulic drive system for a work vehicle according to claim 1, further comprising forward / reverse switching means for setting forward, backward, or neutral of the work vehicle, wherein said determination means determines whether said forward / backward travel means is on the forward side. It is determined that the vehicle is in the traveling mode when the operation is switched to any one of the reverse and the traveling operation means is operated and the working actuator is not driven, and otherwise, the traveling mode is determined. A hydraulic drive device for a work vehicle, wherein the hydraulic drive device is configured to make a determination. 6. The hydraulic drive system for a work vehicle according to claim 1, wherein the first pump input torque is set to a relatively large value when the target rotation speed command value is in an intermediate range. Wherein the second pump input torque is set to be smaller than the first pump input torque when the target rotational speed command value is in an intermediate range. Drive. 7. The hydraulic drive system for a work vehicle according to claim 1, wherein a maximum value of said second target rotation speed is set to be larger than a maximum value of said first target rotation speed, and Wherein the second pump input torque corresponding to the maximum value of the target rotation speed is set smaller than the first pump input torque corresponding to the maximum value of the first target rotation speed. Hydraulic drive.