JP4714721B2 - Traveling hydraulic working machine - Google Patents

Description

  The present invention relates to a wheel loader or telescopic machine that performs a predetermined work by driving a transmission by a prime mover (engine) and driving, operating a hydraulic actuator by a prime mover to actuate a work actuator, and driving a front work device. The present invention relates to a traveling hydraulic working machine such as a handler.

  In a conventional general traveling hydraulic working machine, the hydraulic pump is a fixed displacement type, and the pump maximum absorption torque is also constant (fixed). For this reason, the ratio of the engine output torque distributed to the hydraulic pump and traveling (transmission) is also constant, and the maximum traveling torque is also constant.

  For such a conventional general traveling hydraulic working machine, there is one described in Patent Document 1 in which a variable displacement hydraulic pump is used and the maximum absorption torque of the hydraulic pump can be changed. .

  The prior art described in Patent Document 1 detects the sum of the load of the travel drive device and the work actuator (the sum of the absorption torque of the hydraulic pump and the transmission torque (travel torque)), and the sum is smaller than the output torque of the engine Maintains the maximum absorption torque of the variable displacement hydraulic pump for the work actuator at the set value, and when the sum of the load of the travel drive device and the work actuator becomes larger than the engine output torque, such as when installing a convertor, the variable displacement hydraulic pump The maximum absorption torque (maximum pump torque) is reduced to increase the running torque so that a large traction force can be obtained.

  Further, the prior art described in Patent Document 1 further detects the operating state (traveling state) of the travel drive device and the load state of the work actuator (load state of the front work device), thereby bringing the travel drive device into a stalled state. Yes, even when the sum of the load of the travel drive and the work actuator is greater than the engine output torque, if the load pressure of the work actuator is low, the control of lowering the maximum pump torque is suppressed and the discharge flow rate of the hydraulic pump is increased. The drive speed (working speed) of the actuator is increased.

JP-A-2005-155494

  In the prior art described in Patent Document 1, the sum of the loads of the travel drive device and the work actuator is detected as described above, and the operating state (travel state) of the travel drive device and the load state of the work actuator (load of the front work device) are detected. By detecting the state, it is possible to effectively use the output of the engine at the time of combined operation of the travel drive device and the work actuator, such as excavation work, and improve work efficiency. In addition, when the load pressure of the work actuator is low, control of lowering the maximum pump torque is suppressed and the discharge flow rate of the hydraulic pump is increased to increase the drive speed (work speed) of the work actuator, maintaining a good composite operability and working And work efficiency can be improved.

  However, in the above prior art, there is a problem that workability is lowered in certain work and work efficiency is lowered.

  For example, as an operation to be performed with a wheel loader, the bucket is pushed into the earth and sand by running force with the bucket lowered, the earth and sand are poured into the bucket while the vehicle is running, and the bucket is raised and piled up There is work. Sedimenting and stacking work after pushing the bucket is generally called scraping work. In this scraping work, the amount of work increases by increasing the raising speed (working speed) of the front working device rather than the running force, and the working efficiency is improved.

  However, the load pressure of the work actuator does not necessarily decrease during the lifting operation of the lifting work, and the load pressure of the work actuator often increases especially when the front work device is high. When the load pressure increases in this way, the conventional technology described in Patent Document 1 determines that the conditions are the same as those during excavation. Therefore, the maximum pump torque reduction control functions and the maximum absorption torque of the hydraulic pump is increased. It will fall and the raising speed of a front work apparatus will fall. As a result, the work speed is reduced, and workability and work efficiency are reduced.

  The object of the present invention is to enable a reduction control of the maximum pump torque that accurately grasps the operation status (work status) of the front work device during the combined operation of the travel and the work actuator, maintaining a good composite operability, It is to provide a traveling hydraulic work machine that improves the performance and work efficiency.

  (1) To achieve the above object, the present invention comprises at least one prime mover, a vehicle body on which the prime mover is mounted, and traveling means including a torque converter provided on the vehicle body and coupled to the prime mover, A variable displacement hydraulic pump driven by the prime mover, a front work device provided in the vehicle body, and at least one work actuator that is operated by pressure oil of the hydraulic pump to drive the front work device. In the traveling hydraulic working machine, first detecting means for detecting whether or not the sum of the absorption torque of the hydraulic pump and the traveling torque of the traveling means exceeds the output torque of the prime mover; and a first detecting means for detecting an operating state of the traveling means. 2 detection means, third detection means for detecting the position of the front working device, and absorption torque of the hydraulic pump and travel by the first detection means When it is detected that the sum of the torques exceeds the output torque of the prime mover, depending on the operating state of the traveling means detected by the second detecting means and the position of the front working device detected by the third detecting means And pump torque correcting means for correcting the maximum absorption torque of the hydraulic pump.

  Thus, the first detecting means, the second detecting means, the third detecting means and the pump torque correcting means are provided, and the sum of the absorption torque and the running torque of the hydraulic pump exceeds the output torque of the prime mover by the first detecting means. When detected, the maximum absorption torque of the hydraulic pump is corrected according to the operating state of the traveling means detected by the second detecting means and the position of the front work device detected by the third detecting means, thereby It is possible to control the lowering of the maximum pump torque by accurately grasping the operating status (working status) of the front work device during combined operation with the work actuator. For example, increasing the speed of raising the front work device at the time of scraping work improves composite operability. It is possible to maintain good workability and work efficiency.

  (2) In the above (1), preferably, the pump torque correcting means detects that the sum of the absorption torque of the hydraulic pump and the running torque exceeds the output torque of the prime mover by the first detecting means. A first means for obtaining a correction torque; a second means for correcting the correction torque in accordance with the operating state of the travel means detected by the second detection means; and a front working device detected by the third detection means. Third means for correcting the correction torque according to the position, and fourth means for controlling the maximum absorption torque of the hydraulic pump to be reduced by the correction torque corrected by the second means and the third means.

  As a result, when it is detected that the sum of the absorption torque of the hydraulic pump and the traveling torque exceeds the output torque of the prime mover, the maximum absorption torque of the hydraulic pump is corrected according to the operating state of the traveling means. The pump absorption torque can be reduced and the running torque can be increased according to the operating conditions. In addition, the maximum absorption torque of the hydraulic pump is corrected according to the operating status of the travel means and the position of the front working device, and it is possible to control the reduction of the maximum pump torque that accurately grasps the operating status (working status) of the front working device. For example, by increasing the lifting speed of the front working device during the scraping work, the composite operability can be kept good, and workability and work efficiency can be improved.

  (3) In the above (2), preferably, the third means reduces the correction torque when the third detecting means detects that the front working device is displaced to a certain position. Correct to zero.

  As a result, the amount of decrease in the maximum absorption torque of the hydraulic pump is adjusted in accordance with the position of the front working device, so that it is possible to control the reduction of the maximum pump torque by accurately grasping the operating status (working status) of the front working device. .

  (4) In the above (1), it is preferable that the apparatus further includes fourth detection means for detecting a load state of the work actuator, and the pump torque correction means absorbs the hydraulic pump by the first detection means. When it is detected that the sum of the torque and the running torque exceeds the output torque of the prime mover, the operating status of the running means detected by the second detecting means, and the front working device detected by the third detecting means The maximum absorption torque of the hydraulic pump is corrected according to the position and the load state of the work actuator detected by the fourth detecting means.

  As a result, the operating status (working status) of the front working device can be ascertained from the position of the front working device and the load status of the working actuator, and the maximum pump torque can be reduced by accurately grasping the operating status (working status) of the front working device. Control becomes possible.

  According to the present invention, it is possible to control the lowering of the maximum pump torque by accurately grasping the operation status (working status) of the front working device during the combined operation of traveling and the working actuator. By increasing the speed, the composite operability can be kept good, and workability and work efficiency can be improved.

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

  FIG. 1 is a diagram showing an overall drive system of a traveling hydraulic working machine (wheel loader) according to a first embodiment of the present invention.

  In FIG. 1, a traveling hydraulic working machine according to the present embodiment includes a diesel engine (hereinafter simply referred to as an engine) 1 as a prime mover, a working system 2 and a traveling system (traveling means) 3 driven by the engine 1, And a control system 4.

  The engine 1 includes an electronic governor 41, and the fuel injection amount of the electronic governor 41 is adjusted according to the operation amount (accelerator amount) of the accelerator pedal 42, and the rotational speed of the engine 1 is adjusted. The accelerator pedal 42 is operated by an operator and is a means for instructing a target engine speed (hereinafter referred to as a target speed), and the target speed is set according to the amount of depression (accelerator amount).

  The work system 2 includes a hydraulic pump 12 driven by the engine 1, a plurality of hydraulic actuators (work actuators) 13 and 14 that are operated by pressure oil discharged from the hydraulic pump 12, a hydraulic pump 12, and a plurality of hydraulic actuators 13. , 14 for controlling the flow of pressure oil supplied to the corresponding actuator, and the pilot pressure for controlling the hydraulic actuators 13, 14 by switching the direction switching valves 17, 18 (operation A plurality of operating lever devices 23 and 24 that generate a signal), and a pilot hydraulic pump 27 that supplies pressure oil to the operating lever devices 23 and 24 as a primary pressure. In the present embodiment, the hydraulic actuator 13 is a bucket cylinder, and the hydraulic actuator 14 is a boom cylinder (described later).

  The hydraulic pump 12 is a variable displacement type and includes a torque control regulator 28. When the discharge pressure of the hydraulic pump 12 increases, the torque control regulator 28 decreases the tilt (capacity) of the hydraulic pump 12 accordingly, and the absorption torque of the hydraulic pump 12 exceeds the set value (maximum pump absorption torque). The tilting (capacity) of the hydraulic pump 12 is controlled so as not to occur. The set value (maximum pump absorption torque) of the torque control regulator 28 is variable and is controlled by the torque control solenoid valve 29. The torque control solenoid valve 29 is operated by an electrical command signal, and outputs a control pressure according to the command signal using the discharge pressure of the pilot hydraulic pump 27 as a hydraulic pressure source.

  The traveling system 3 constitutes a traveling drive device, and includes a torque converter 31 connected in series with the hydraulic pump 12 to the output shaft of the engine 1 and a transmission (T / M) connected to the output shaft of the torque converter 31. ) 32, and a front wheel 35 and a rear wheel 36 connected to the transmission 32 through differential gears 33 and 34.

  The control system 4 includes a position sensor 43 that detects the amount of depression of the accelerator petal 42 (accelerator amount), a rotation sensor 45 that detects the output rotation speed of the engine 1 (the input rotation speed of the torque converter 31), and the torque converter 31 A rotation sensor 46 that detects the output rotation speed, an angle sensor 47 that detects the position (boom angle) of the front working device 104 (see FIG. 2) of the traveling hydraulic working machine, and a controller 48 are provided. The controller 48 has an engine control function for outputting a command signal to the electronic governor of the engine 1 so as to obtain a rotation speed corresponding to the accelerator amount based on a signal from the position sensor 43, a position sensor 43, rotation sensors 45 and 46, an angle Based on a signal from the sensor 47, a predetermined calculation process is performed, and a pump control function for outputting a command signal to the torque control electromagnetic valve 29 is provided.

  In this embodiment, the traveling hydraulic working machine is a wheel loader, and this embodiment is a case where the present invention is applied to a wheel loader.

  FIG. 2 is a view showing an appearance of a wheel loader to which the present invention is applied. In FIG. 1, a wheel loader 100 includes a vehicle body front portion 101 and a vehicle body rear portion 102 that are rotatably coupled to each other, and the vehicle body front portion 101 and the vehicle body rear portion 102 constitute a vehicle body. A front working device 104 is provided in the vehicle body front portion 101, a driver seat 106 is provided in the vehicle body rear portion 102, and operation means such as an operation lever device 107, a handle 108, and the accelerator pedal 42 described above are provided in the driver seat 106. It has been. Further, the front wheel 35 and the rear wheel 36 described above are attached to the vehicle body front portion 101 and the vehicle body rear portion 102, respectively, and the engine 1, the hydraulic pump 12, the torque converter 31, the transmission 32, the controller 48, and the like described above are attached to the vehicle body rear portion 102. Each of the above devices is mounted, and the engine 1 is controlled by depressing the accelerator pedal 42, and the power generated by the engine 1 is transmitted to the front wheels 35 and the rear wheels 36 via the torque converter 31 and the transmission 32. A steering cylinder 103 is provided between the vehicle body front portion 101 and the vehicle body rear portion 102, and the steering cylinder 103 is operated by operating the handle 108, and the direction of the vehicle body front portion 101 with respect to the vehicle body rear portion 102 (the traveling direction of the vehicle body). Changes.

  The front working device 104 has a bucket (working tool) 111 and a boom 112. The bucket 111 is rotated up and down (tilt and dumping operation) by the expansion and contraction of the bucket cylinder 13 described above, and the boom 112 is connected to the boom cylinder 14 described above. It rotates up and down by expansion and contraction. Each of the boom 112 and the boom cylinder 14 is pin-coupled to the support portion 115 and constitutes a link mechanism together with the support portion 115. The operation lever device 107 includes an operation lever that can be operated in the cross direction. When the operation lever is operated in one direction of the cross, the operation lever device 107 functions as the operation lever device 23 described above, and switches the direction switching valve 17 to expand and contract the bucket cylinder 113. When the operation lever is operated in the other direction of the cross, it functions as the operation lever device 24 described above, and the bucket 111 is rotated up and down, the direction switching valve 18 is switched, the boom cylinder 112 is expanded and contracted, and the boom 112 is rotated up and down. The angle sensor 47 described above is provided at the pin coupling portion between the boom 12 and the support portion 115.

  FIG. 3 is a functional block diagram showing the pump control function of the controller 48.

  In FIG. 3, the controller 48 includes a target rotation speed calculation unit 80, a base torque calculation unit 81, a rotation speed deviation calculation unit 82, a correction torque calculation unit 83, a speed ratio calculation unit 84, a traveling state determination unit 85, a multiplication unit 88, The front position determination unit 91, the multiplication unit 92, and the addition unit 93, which are first work state determination units, are provided.

  The target rotational speed calculation unit 80 receives an accelerator amount detection signal from the position sensor 43, refers to the table stored in the memory, and calculates a target engine rotational speed NR corresponding to the accelerator amount at that time. To do. The target rotational speed NR is the engine rotational speed intended by the operator during work, and the relationship between the two is set in the memory table so that the target rotational speed NR increases as the accelerator amount increases.

  The base torque calculation unit 81 inputs the target engine speed NR, refers to the table stored in the memory, and calculates the pump base torque TR according to the target engine speed NR at that time. In the memory table, the relationship between NR and TR is set so that the pump base torque TR increases as the target engine speed NR increases.

  The rotational speed deviation calculation unit 82 subtracts the target engine rotational speed NR calculated by the target rotational speed calculation unit 80 from the output rotational speed of the engine 1 detected by the rotational sensor 45 (hereinafter referred to as the actual engine rotational speed NA). The rotational speed deviation ΔN (= NA−NR) is calculated.

  The correction torque calculation unit 83 inputs the rotation speed deviation ΔN calculated by the rotation speed deviation calculation unit 82, refers to the table stored in the memory, and corrects the torque corresponding to the rotation speed deviation ΔN at that time. ΔT is calculated. The correction torque ΔT is a high load operation in which the hydraulic pump 12 consumes the maximum absorption torque and the sum of the pump absorption torque (work load) and the input torque (running torque) of the torque converter 31 exceeds the engine output torque. This is to reduce the maximum absorption torque of the hydraulic pump 12 when the state is reached, and to increase the running torque by that amount so that a large traction force can be obtained. In the memory table, the actual engine speed NA is the target. When the engine speed NR matches the engine speed NR and the engine speed deviation ΔN is 0, ΔT = 0, the decrease amount of the actual engine speed increases, and the first set value in the region where the engine speed deviation ΔN is a negative value. When the rotational speed deviation ΔN decreases, the correction torque ΔT becomes smaller than 0 in the negative value region, and the rotational speed deviation ΔN decreases below the second set value (<first set value). [Delta] T = relationship ΔN and [Delta] T to be constant value of ΔTC is set.

  The speed ratio calculation unit 84 inputs the input / output rotation speed detection signal of the torque converter 31 from the rotation speed sensors 45 and 46, calculates e = output rotation speed / input rotation speed, and calculates the torque converter speed ratio e. calculate.

  The running state determination unit 85 inputs the torque converter speed ratio e calculated by the speed ratio calculation unit 83, refers to the table stored in the memory, and corresponds to the torque converter speed ratio e at that time. 1 The determination coefficient α is calculated. The first determination coefficient α is when the torque converter speed ratio e is not small (when the torque converter 31 is not in a state close to a stall), that is, when the traveling system 3 does not require a large traveling force (traveling torque). Is to limit the correction of the pump absorption torque by the correction torque ΔT (decrease of the pump maximum absorption torque), and the memory table shows that the torque converter speed ratio e is smaller than the first set value. When α = 1 and the torque converter speed ratio e is equal to or greater than the second set value (> first set value), α = 0, and the torque converter speed ratio e is between the first set value and the second set value. In some cases, the relationship between e and α is set such that α decreases as the torque converter speed ratio e increases at a predetermined rate (gain).

  The front position determination unit 91 inputs a detection signal of the rotation angle of the boom 112 from the angle sensor 47 (boom angle: the height position of the front work device 104), and refers to a table stored in the memory. Then, the second determination coefficient η corresponding to the boom angle at that time is calculated. The boom angle becomes the smallest (for example, 0 °) when the boom 112 is in the downward rotation position and the front work device 104 is in the lowest position (for example, when the bucket 111 is in a position in contact with the ground in the excavation posture). The boom 112 increases from the position as the front working device 104 is moved upward. When the boom angle is large (when the position of the front working device 104 is high), that is, the second judgment coefficient η is dirt or sand that has been swept into the bucket 111 of the front working device 104 while traveling and lifted up. This is for limiting the correction of pump absorption torque by the correction torque ΔT (decrease of the pump maximum absorption torque) when it can be considered that the work is a lifting operation, and the memory table shows the boom angle. When it is smaller than the first set value, η = 1, and when the boom angle is equal to or greater than the second set value (> first set value), η = 0, and the boom angle first set value and the second set value are When it is between, the relationship between the boom angle and η is set so that η decreases as the boom angle increases at a predetermined rate (gain).

  The multipliers 88 and 92 add the first determination coefficient α output from the traveling state determination unit 85 and the second determination coefficient η output from the front position determination unit 91 to the correction torque ΔT calculated by the correction torque calculation unit 83. Multiplication is performed and a correction torque ΔTA is calculated.

  The adder 93 adds the correction torque ΔTA (negative value) to the pump base torque TR calculated by the base torque calculation unit 81, and calculates the corrected pump base torque TRA. This pump base torque TRA is converted into a command signal for the torque control electromagnetic valve 29 by a known method, and is output to the torque control electromagnetic valve 29. Thus, the torque control electromagnetic valve 29 outputs a control pressure corresponding to the command signal to the torque control regulator 28, and controls the maximum pump absorption torque set in the torque control regulator 28 to be TRA.

  The setting relationship between the output torque (hereinafter referred to as torque converter torque) of the torque converter 31 of the traveling hydraulic working machine according to the present embodiment and the absorption torque (hereinafter referred to as pump torque as appropriate) of the hydraulic pump 12 is described with reference to FIG. explain. In FIG. 4, the horizontal axis represents the number of revolutions of the engine 1 and the vertical axis represents the torque. TE is the output torque of the engine 1 in the entire load region where the fuel injection amount of the electronic governor 41 is maximum (hereinafter referred to as engine torque as appropriate), and TR is the regulation region before the fuel injection amount of the electronic governor 41 is maximum. , TT is the output torque (torque torque) of the torque converter 31, and TP is the maximum absorption torque of the hydraulic pump 12 (hereinafter referred to as maximum pump torque as appropriate). The engine output torque TR in the regulation region is set when the droop characteristic having a downward slope is set.

  The torque converter torque TT shown in the figure is when the torque converter 31 is in a stalled state (the output speed is 0 and the speed ratio e = 0), and the torque converter torque TT is increased as the speed ratio increases from 0 when the hydraulic working machine starts to move. It changes in the direction of the arrow X shown in the figure to decrease. The illustrated maximum pump torque TP sets the target rotational speed of the engine 1 to the maximum rated rotational speed N0 by depressing the accelerator pedal 42 to the maximum, and the correction torque ΔTA calculated by the multipliers 88 and 92 is 0. The target rotational speed NR calculated by the target rotational speed calculation unit 80 decreases as the engine rotational speed is decreased by reducing the depression amount of the accelerator pedal 42 (TPmax). Since the calculated base torque TR is also reduced, the maximum pump torque PT is reduced as shown by the arrow Y in the figure. Further, since the corrected pump base torque TRA decreases as the correction torque ΔTA decreases from 0 (the absolute value of ΔTA increases), the maximum pump torque TP similarly decreases as shown by the arrow Y in the figure.

  In the case of a traveling hydraulic working machine with a torque converter as in the present embodiment, traveling force (traction force) is very important. Therefore, the engine 1 is selected so that the output torque (point B) at the rated rotational speed N0 is larger than the maximum torque converter torque (point A) and has a margin. On the other hand, the maximum pump torque TP is determined by the excavation balance (the balance between the driving traction force and the front force) during the bucket operation, and basically has a value smaller than the torque converter torque TT (point C). The engine speed at point A is N1 (> N0), and the engine speed at point C is N2 (> N0). Therefore, in the traveling hydraulic working machine with a torque converter, the engine 1 does not fall below the target rated rotational speed N0 in the traveling independent operation as well as the front independent operation.

  In the above, the rotation sensor 45, the target rotation speed calculation unit 80 and the rotation speed deviation calculation unit 82 of the controller 48 are configured such that the sum of the absorption torque of the hydraulic pump 12 and the travel torque of the travel system (travel means) 3 is the engine (prime motor) 1. The rotation sensor 45, 46 and the speed ratio calculation unit 84 of the controller 48 constitute second detection means for detecting the operating state of the traveling means 3. The angle sensor 47 constitutes third detection means for detecting the position of the front working device 104, and includes a correction torque calculation unit 83, a traveling state determination unit 85, a front position determination unit 91, multiplication units 88 and 92, and an addition of the controller 48. The part 93 detects that the sum of the absorption torque of the hydraulic pump 12 and the running torque exceeds the output torque of the prime mover 1 by the first detection means. The pump torque correcting means for correcting the maximum absorption torque of the hydraulic pump 12 according to the operating state of the traveling means 3 detected by the second detecting means and the position of the front working device 104 detected by the third detecting means. Configure.

  Further, the correction torque calculation unit 83 of the controller 48 uses the first detection means (the rotation sensor 45, the target rotation number calculation unit 80 and the rotation number deviation calculation unit 82 of the controller 48) to calculate the absorption torque and the running torque of the hydraulic pump 12. When it is detected that the sum exceeds the output torque of the prime mover 1, a first means for obtaining a correction torque is configured, and the running state determination unit 85 and the multiplication unit 88 of the controller 48 include the second detection unit (the rotation sensor 45). , 46 and the speed ratio calculation unit 84) of the controller 48 constitutes a second means for correcting the correction torque in accordance with the operating condition of the traveling means 3, and a front position determination unit 91 and a multiplication unit 92 of the controller 48 are configured. Corrects the correction torque according to the position of the front work device 104 detected by the third detection means (angle sensor 47). That the third means constitute, adding unit 93, constituting the fourth means for controlling so as to reduce the correction torque component which the maximum absorption torque of the hydraulic pump 12 is corrected by the second means and third means.

  Next, the operation of the present embodiment will be described.

  FIG. 5 shows the case where the accelerator pedal 42 is depressed almost to the maximum, the target engine speed NR is set to the rated speed N0, and the speed ratio e of the torque converter 31 is e = 0 (stall state). 6 is a case where the accelerator pedal 42 is depressed almost to the maximum, the target engine speed NR is set to the rated speed N0, and the speed ratio e of the torque converter 31 is about e = 0.1 to 0.2.

  5 and 6, TEP is the engine torque that can be used by the torque converter 31 (traveling side) when the hydraulic pump 12 that subtracts TPmax from TE is consuming the maximum absorption torque TP. TPmin is the maximum pump torque when the maximum pump torque TP is reduced by the correction torque ΔTC, and TEPA is the torque when the maximum pump torque TP obtained by subtracting TPmin from TE is reduced by the correction torque ΔTC. This is the engine torque that can be used in the converter 31. When the correction torque ΔTA varies between 0 and ΔTC, the maximum absorption torque TP of the hydraulic pump 12 varies between TPmax and TPmin, and the engine torque available in the torque converter 31 varies between TEP and TEPA. To do.

<Operating state 1: Point A or D in FIG. 6>
Even when the torque converter 31 is in a stalled state (e = 0), the front work is not performed, or the pump discharge pressure is low and the pump torque consumed by the hydraulic pump 12 is small even when the front work is performed. , Engine torque ≧ torque torque + pump torque. In this case, the engine speed does not decrease, and the matching point between the running load and the pump load (actuator load) is the intersection of the point A in FIG. 6 or the curve of TT and a straight line extending upward from the rated speed N0. Near the point. At this time, since the rotational speed deviation calculated by the rotational speed deviation calculating unit 82 in FIG. 3 is ΔN≈0, the correction torque calculated by the correction torque calculating unit 83 is ΔT = 0. Therefore, the maximum pump torque TP does not decrease.

<Operating state 2: Point E and point F in FIG. 6>
When the torque converter 31 is in a stalled state (e = 0) and the torque consumption of the hydraulic pump 12 is increased and the engine torque <torque torque + pump torque, the engine 1 is overloaded and the actual engine speed NA is descend. Therefore, the rotation speed deviation calculating unit 82 in FIG. 3 calculates the rotation speed deviation ΔN <0, and the correction torque calculating unit 83 calculates correction torque ΔT> 0, for example, ΔT = ΔTC. Further, since the speed ratio e = 0, the travel condition determination unit 85 calculates the first determination coefficient α = 1. Furthermore, in the stalled state of the torque converter 31 (e = 0), there are many cases where work that requires traveling traction force (pressing force) such as excavation work for pushing the bucket into the ground is performed, and in such work, In many cases, the rotation angle of the boom 112 is small and the front working device 104 is in a low posture. In this case, the front position determination unit 91 in FIG. 3 calculates, for example, boom angle <first set value and the second determination coefficient η = 1. As a result, the correction torque ΔTA = ΔT (that is, ΔTA = ΔTC) is calculated by the multipliers 88 and 92, and the maximum pump torque TP decreases by ΔTC to become TPmin, so that the hydraulic pump 12 consumes the maximum absorption torque TP. The engine torque available at the time torque converter 31 increases to TEPA. Therefore, at this time, the matching point between the traveling load and the pump load is the point F which is the intersection of the curve of TT (e = 0) and the curve of TEPA, and the engine speed decreases from the rated speed N0 to N4.

  In a conventional general traveling hydraulic working machine using a fixed displacement type hydraulic pump, the maximum pump torque TP does not change in the same operation state as described above, and the engine torque available in the torque converter 31 remains TEP. Therefore, the matching point between the running load and the pump load is the point E, which is the intersection of the curve of TT (e = 0) and the curve of TEP, and the engine speed decreases to N3 (<N4).

  As described above, in the conventional general traveling hydraulic working machine, the maximum pump torque TP does not change, and the engine torque that can be used by the torque converter 31 remains TEP. Therefore, the traveling traction force (pressing force) is increased. It is not possible. On the other hand, in the present embodiment, since the driving force (traction force) increases from TEP to TEPA, a large traction force can be secured in an operating state that requires traction force, such as excavation work on a natural ground. The output can be used effectively.

<Operating state 3: points G and H in FIG. 6>
Even when the speed ratio of the torque converter 31 is about e = 0.1 to 0.2 and engine torque <torque torque + pump torque, the engine 1 becomes overloaded and the actual engine speed NA decreases. Therefore, the rotation speed deviation calculating unit 82 in FIG. 3 calculates the rotation speed deviation ΔN <0, and the correction torque calculating unit 83 calculates the correction torque ΔT> 0, for example, ΔT = ΔTC. On the other hand, at this time, in the traveling state determination unit 85, for example, if the first setting value <0.2, the first determination coefficient α = 1 is calculated. Furthermore, the state in which the speed ratio of the torque converter 31 is about e = 0.1 to 0.2 indicates that the excavation work after excavation (moving soil into the bucket 111 of the front working device 104 while traveling and raising the bucket 111) 3), for example, boom angle> first set value, second determination coefficient η <1 is calculated, and boom angle> second. When the set value is reached, the second determination coefficient η = 0 is calculated. As a result, correction torque ΔTA <ΔT (that is, ΔTA <ΔTC), for example, ΔTA = 0, is calculated by the multipliers 88 and 92, and the maximum pump torque TP remains at the maximum TPmax. The engine torque that can be used by the torque converter 31 when TP is consumed also remains TEP. Therefore, at this time, the matching point between the running load and the pump load is the point G which is the intersection of the curve of TT (e = 0.1 to 0.2) and the curve of TEP in FIG.

  Here, in the prior art described in, for example, Japanese Patent No. 2968558, since the boom angle (the height position of the front work device 104) is not seen in the operation state similar to the above, as in the case of the operation state 2, When engine torque <torque torque + pump torque, the maximum pump torque TP was immediately reduced, and the engine torque available in the torque converter 31 was increased to TEPA. In this case, the matching point between the running load and the pump load is the H point that is the intersection of the curve of TT (e = 0.1 to 0.2) and the curve of TEPA.

  Here, in a working state in which the height position of the front work device 104 is increased, if the raising speed of the front work device is increased, the work speed is increased, the work amount is increased, and the work efficiency is increased. In the prior art described in Japanese Patent No. 2968558, even in such a case, the maximum pump torque TP is reduced and the engine torque that can be used by the torque converter 31 is increased to TEPA. descend. On the other hand, in the present embodiment, since the maximum pump torque TP does not decrease, the hydraulic pump 12 can increase the pump torque to the maximum TP, ensure the work speed, and improve the work efficiency.

  Next, a specific work example according to the present embodiment will be described.

<Outline of excavation and lifting work>
Examples of work include excavation work of earth and sand such as natural ground and subsequent scraping work. For excavation work, the front work device 104 is lowered, and the accelerator pedal 42 is operated to control the engine speed, and the bucket 111 is pushed into the earth and sand (excavation object) by the running force (traction force). It is an operation to excavate earth and sand. In the scraping work, the front working device 104 is lifted by rotating the boom 112 upward, and the soil is rubbed into the bucket 111 while traveling (while climbing the natural ground when excavating natural ground during excavation work). This is an operation to raise the bucket 111 and pile up the soil that has been crushed.

  In excavation work, a combined stall state occurs when the bucket is pushed in, and engine torque <torque torque + pump torque. The combined stall state is a state where the torque converter 31 is in a stalled state (e = 0) and a relief state is reached in which the discharge pressure of the hydraulic pump 12 rises to a set pressure of a main relief valve (not shown).

  In the lifting work while climbing the ground, the speed ratio of the torque converter 31 is in a traveling state of about 0.1 to 0.2, for example. In addition, since the earth and sand trapped in the bucket 111 is quickly lifted upward by the rotation of the boom 112, the discharge pressure (work load) of the hydraulic pump 12 rises to near the relief pressure. Therefore, also in this case, engine torque <torque torque + pump torque.

<Drilling work>
In the conventional general traveling hydraulic working machine, the maximum absorption torque of the hydraulic pump is constant (fixed). Therefore, in the convert installed state, the matching point is point E in FIG. 5 and the engine speed is N3. In this case, the output torque of the engine 1 is used in preference to the hydraulic pump 12.

  In the present embodiment, when the combined stall state occurs when the bucket is pushed in, the engine speed is reduced and the correction torque calculation unit 83 calculates the correction torque ΔT = ΔTC. At this time, since it is in the combined stall state, the speed ratio calculation unit 84 calculates e≈0 as the speed ratio e, and the running state determination unit 85 calculates α = 1 as the first determination coefficient α. At this time, since the front working device 104 is lowered, the boom angle is small (≈0 °), and the front position determination unit 91 calculates the second determination coefficient η = 1. As a result, the multiplication units 88 and 92 calculate the correction torque ΔTA = ΔTC, and the addition unit 93 adds the base torque TR calculated by the base torque calculation unit 81 and the correction torque ΔTA (= ΔT) (TR to ΔTA). Is calculated as the corrected base torque TRA. That is, the corrected base torque TRA decreases by the correction torque ΔTC. As a result, the maximum pump torque TP decreases to TPmin, the engine torque TEP that can be used for driving increases from the solid line in FIG. 5 to the broken TEPA, the matching point becomes the F point in FIG. 5, and the torque converter torque increases. The traction force increases and the engine output can be used effectively.

<Scraping work>
In the prior art described in Japanese Patent No. 2968558, when engine torque <torque torque + pump torque, this is detected by a decrease in engine speed, and the maximum pump torque TP is immediately reduced to TPmin and used in the torque converter 31. The possible engine torque was increased to TEPA. For this reason, the pump torque is lowered, the matching point is the H point in FIG. 6, and the discharge flow rate of the hydraulic pump 12 is lowered. As a result, the lifting speed of the bucket is lowered and the work amount is lowered.

  In the present embodiment, engine torque is less than the torque converter torque + pump torque in the scraping operation, and the engine speed is reduced. The correction torque calculation unit 83 calculates the correction torque ΔT = ΔTC, and the speed ratio calculation unit 84 calculates the speed ratio. As e, approximately e = 0.1 to 0.2 (<first set value) is calculated, and α = 1 is calculated as the first determination coefficient α by the traveling state determination unit 85, while the boom 112 is rotated upward. Since the boom angle increases as it moves, the front position determination unit 91 calculates a value that gradually decreases from 1 to 0 as the second determination coefficient η. When the boom angle> the second set value, the second determination coefficient η = 0 is calculated. As a result, the multipliers 88 and 92 calculate a value that becomes smaller than ΔTC as the boom angle increases as the correction torque ΔTA, and when the boom angle> second set value and the second determination coefficient η = 0 is calculated. , ΔTA = 0 is calculated. As a result, the amount of decrease in the maximum pump torque TP gradually decreases. When the boom angle> the second set value, the maximum pump torque TP does not decrease and remains at TPmax, and the matching point is the point G in FIG. Therefore, it is possible to limit the decrease in the discharge flow rate of the hydraulic pump 12 (increase the discharge flow rate of the hydraulic pump 12), increase the bucket speed, increase the work amount, and improve the work efficiency.

  As described above, according to the present embodiment, it is possible to control the reduction of the maximum pump torque that accurately grasps the work situation at the time of the combined operation of the travel and the work actuator, and the composite operability is kept good, the workability and the work are improved. Efficiency can be improved.

  A second embodiment of the present invention will be described with reference to FIGS. In FIG. 7, the same components as those shown in FIG. 1 are denoted by the same reference numerals. In FIG. 8, the same components as those shown in FIG.

  In FIG. 7, the traveling hydraulic working machine according to the present embodiment includes a control system 4A, and the control system 4A includes loads of the hydraulic actuators 13 and 14 in addition to those of the first embodiment shown in FIG. A pressure sensor 44 that detects the discharge pressure of the hydraulic pump 12 as a situation is further provided, and the controller 48A is based on signals from the position sensor 43, the pressure sensor 44, the rotation sensors 45 and 46, and the angle sensor 47 in its pump control function. Then, predetermined calculation processing is performed, and a command signal is output to the torque control electromagnetic valve 29. The configuration of the work system 2 and the traveling system 3 and the engine control function provided in the controller 48A are the same as those in the first embodiment shown in FIG.

  In FIG. 8, the controller 48 </ b> A has functions of a work load determination unit 86 and a selection unit 87, which are second work state determination units, in addition to the various functions illustrated in FIG. 3.

  The work load determination unit 86 receives the pump pressure detection signal from the pressure sensor 44, refers to the table stored in the memory, and calculates a third determination coefficient β corresponding to the pump pressure at that time. . The third determination coefficient β is a correction torque ΔT when the discharge pressure of the hydraulic pump 12 is not so high (the work load is not so large), that is, when the working system 2 is in an operating condition that requires a larger pump flow rate. The pump absorption torque correction (decrease in the pump maximum absorption torque) due to the above is limited. In the memory table, when the pump pressure is lower than the first set value, β = 0, and the pump pressure is When the second set value (> first set value) is exceeded, β = 1, and when the pump pressure is between the first set value and the second set value, the pump pressure decreases at a predetermined rate (gain). As a result, the relationship between the pump pressure and β is set so that β decreases.

  The selection unit 87 selects the smaller value of the first determination coefficient α and the third determination coefficient β and sets it as the determination coefficient γ. Here, when the first determination coefficient α and the third determination coefficient β are equal, the selection unit 87 selects one of them, for example, α according to a predetermined logic.

  The multipliers 88 and 92 multiply the correction torque ΔT calculated by the correction torque calculation unit 83 by the determination coefficient γ output from the selection unit 87 to obtain a correction torque ΔTA.

  In the above, the pressure sensor 44 constitutes fourth detection means for detecting the load status of the hydraulic actuators 13 and 14 (work actuator), and the correction torque calculation unit 83, the travel state determination unit 85, and the work load determination unit 86 of the controller 48A. The selection unit 87, the front position determination unit 91, the multiplication units 88 and 92, and the addition unit 93 are performed by the first detection unit (the rotation sensor 45, the target rotation number calculation unit 80 and the rotation number deviation calculation unit 82 of the controller 48A). When it is detected that the sum of the absorption torque and the running torque of the hydraulic pump 12 exceeds the output torque of the prime mover 1, it is detected by the second detection means (the rotation sensor 45, 46 and the speed ratio calculation unit 84 of the controller 48A). The operating state of the traveling means 3 and the front working device detected by the third detecting means (angle sensor 47) And position 04, constituting the pump torque correction means for correcting the maximum absorption torque of the hydraulic pump 12 according to the load condition of the fourth detection means (pressure sensor 44) working actuator 13 detected by.

  In the present embodiment configured as described above, the load pressure of the hydraulic actuator 14 (boom cylinder) is low and the hydraulic pump 12 is low even when the front work device 104 is in a low posture at the beginning of lifting the front work device. When the discharge pressure (pump pressure) is low, β = 0 or β << 1 is calculated as the third determination coefficient β, the correction torque ΔTA = 0 or ΔTA << ΔTC, and the base torque corrected accordingly Increase TRA and do not perform control to reduce maximum pump torque, or significantly limit control to reduce maximum pump torque. As a result, it is possible to increase the discharge flow rate of the hydraulic pump 12 and increase the work speed when the front work device 104 at the beginning of raising the front work device for scraping is in a low posture.

  A third embodiment of the present invention will be described with reference to FIG. 9, the same functions as those shown in FIGS. 3 and 8 are denoted by the same reference numerals.

  In FIG. 9, the controller 48B of the traveling hydraulic working machine according to this embodiment is similar to the controller 48 of the first embodiment shown in FIG. The rotation speed deviation calculating unit 82, the correction torque calculating unit 83, the speed ratio calculating unit 84, the running state determining unit 85, the multiplying unit 88, the front position determining unit 91, and the adding unit 93 are included in the first embodiment. The selection unit 87 is provided instead of the multiplication unit 92 which is a form, and the first determination coefficient α calculated by the traveling state determination unit 85 and the second determination coefficient η calculated by the front position determination unit 91 in the selection unit 87. Is selected, and the selection result is set as a determination coefficient γ. Here, when the first determination coefficient α and the third determination coefficient η are equal, the selection unit 87 selects one of them, for example, α according to a predetermined logic. The determination coefficient γ obtained by the selection unit 87 is multiplied by the correction torque ΔT calculated by the correction torque calculation unit 83 in the multiplication unit 88 to calculate the correction torque ΔTA.

  In the above, the correction torque calculation unit 83, the traveling state determination unit 85, the front position determination unit 91, the selection unit 87, the multiplication unit 88, and the addition unit 93 of the controller 48B are the first detection means (the rotation sensor 45, the controller 48B). When it is detected by the target rotational speed calculation unit 80 and the rotational speed deviation calculation unit 82) that the sum of the absorption torque of the hydraulic pump 12 and the running torque exceeds the output torque of the prime mover 1, the second detection means (rotation sensor) 45, 46 and the operating ratio of the traveling means 3 detected by the speed ratio calculating unit 84) of the controller 48B and the position of the front working device 104 detected by the third detecting means (angle sensor 47). The pump torque correction means for correcting the maximum absorption torque of 12 is configured.

  This embodiment configured as described above operates in the same manner as the first embodiment, and the same effect as the first embodiment can be obtained.

  The operation of the present embodiment configured as described above is substantially the same as that of the first embodiment, and the same effect as that of the first embodiment can be obtained by this embodiment.

  A fourth embodiment of the present invention will be described with reference to FIG. In FIG. 10, the same functions as those shown in FIGS. 3, 8, and 9 are denoted by the same reference numerals.

  10, the controller 48C of the traveling hydraulic working machine according to the present embodiment is similar to the controller 48A of the second embodiment shown in FIG. 8 in that the target rotational speed calculator 80, the base torque calculator 81, Each of a rotation speed deviation calculation unit 82, a correction torque calculation unit 83, a speed ratio calculation unit 84, a traveling state determination unit 85, a work load determination unit 86, a selection unit 87, a multiplication unit 88, a front position determination unit 91, and an addition unit 93 It has a function. However, as in the case of the third embodiment shown in FIG. 9, the selection unit 87 uses the first determination coefficient α calculated by the traveling state determination unit 85 and the second determination coefficient η calculated by the front position determination unit 91. Is selected, and the selection result is set as a determination coefficient γ. The determination coefficient γ obtained by the selection unit 87 and the second determination coefficient η obtained by the front position determination unit 91 are multiplied by the correction torque ΔT calculated by the correction torque calculation unit 83 in the multiplication units 88 and 92 to calculate the correction torque ΔTA. To do.

  In the above, the correction torque calculation unit 83, the traveling state determination unit 85, the front position determination unit 91, the selection unit 87, the work load determination unit 86, the multiplication units 88 and 92, and the addition unit 93 of the controller 48C are the first detection unit. When (the rotation sensor 45, the target rotation speed calculation unit 80 and the rotation speed deviation calculation unit 82 of the controller 48C) detects that the sum of the absorption torque and the running torque of the hydraulic pump 12 exceeds the output torque of the prime mover 1, The operating state of the traveling means 3 detected by the second detecting means (the rotation sensors 45 and 46 and the speed ratio calculating unit 84 of the controller 48C), and the front working device detected by the third detecting means (angle sensor 47). 104 and the load conditions of the work actuators 13 and 14 detected by the fourth detecting means (pressure sensor 44). Constituting the pump torque correction means for correcting the maximum absorption torque of the hydraulic pump 12 Te.

  The operation of the present embodiment configured as described above is substantially the same as that of the second embodiment, and the same effect as that of the second embodiment can be obtained by this embodiment.

  In the embodiment described above, the wheel loader has been described as an example of the traveling hydraulic working machine. However, the same effect can be obtained by applying to other traveling hydraulic working machines provided with a torque converter. Is obtained. Examples of the traveling hydraulic working machine with a torque converter other than the wheel loader include a telescopic handler and a wheel excavator.

1 is a diagram showing an overall system of a traveling hydraulic working machine according to a first embodiment of the present invention. It is a figure which shows the external appearance of the wheel loader to which this invention is applied. It is a functional block diagram which shows the pump control function of the controller in the 1st Embodiment of this invention. It is a figure which shows the setting relationship of the output torque of a torque converter with respect to the engine output of the traveling hydraulic working machine concerning this Embodiment, and the absorption torque of the hydraulic pump. It is a figure which shows the operation state of the traveling type hydraulic working machine concerning this Embodiment. It is a figure which shows the operation state of the traveling type hydraulic working machine concerning this Embodiment. It is a figure which shows the whole system of the traveling type hydraulic working machine concerning the 2nd Embodiment of this invention. It is a functional block diagram which shows the pump control function of the controller in the 2nd Embodiment of this invention. It is a functional block diagram which shows the pump control function of the controller in the 3rd Embodiment of this invention. It is a functional block diagram which shows the pump control function of the controller in the 4th Embodiment of this invention.

Explanation of symbols

1 prime mover (engine)
2 Working system 3 Traveling system 4, 4 A Control system 12 Hydraulic pump 13, 14 Hydraulic actuator 17, 18 Directional switching valve 23, 24 Operation lever device 28 Torque control regulator 29 Torque control solenoid valve 31 Torque converter 32 Transmission 33, 34 Differential gear 35 Front wheel 36 Rear wheel 41 Electronic governor 42 Accelerator pedal 43 Position sensor 44 Pressure sensor 45, 46 Rotation sensor 47 Angle sensors 48, 48A, 48B, 48C Controller 80 Target rotational speed calculation unit 81 Base torque calculation unit 82 Rotational speed deviation calculation unit 83 Correction Torque Calculation Unit 84 Speed Ratio Calculation Unit 85 Traveling State Determination Unit 86 Work Load Determination Unit 87 Selection Unit 88 Multiplication Unit 91 Front Position Determination Unit 92 Multiplication Unit 93 Addition Unit 100 Wheel Loader 101 Car Body Front Part 102 Car Body Rear Part 10 Front working mechanism 106 driver seat 107 operating lever unit 108 handle 111 bucket 112 Boom

Claims (4)

At least one prime mover, a vehicle body on which the prime mover is mounted, traveling means provided on the vehicle body and including a torque converter coupled to the prime mover, a variable displacement hydraulic pump driven by the prime mover, A traveling hydraulic working machine comprising a front working device provided on a vehicle body and at least one work actuator that is operated by pressure oil of the hydraulic pump to drive the front working device;
First detection means for detecting whether the sum of the absorption torque of the hydraulic pump and the running torque of the running means exceeds the output torque of the prime mover;
Second detection means for detecting an operating state of the traveling means;
Third detecting means for detecting the position of the front working device;
When the first detection means detects that the sum of the absorption torque of the hydraulic pump and the running torque exceeds the output torque of the prime mover, the operating status of the running means detected by the second detection means and the third detection A traveling hydraulic working machine comprising pump torque correcting means for correcting the maximum absorption torque of the hydraulic pump in accordance with the position of the front working device detected by the means. The traveling hydraulic working machine according to claim 1,
The pump torque correction means includes a first means for obtaining a correction torque when the first detection means detects that the sum of the absorption torque of the hydraulic pump and the running torque exceeds the output torque of the prime mover; Second means for correcting the correction torque according to the operating state of the traveling means detected by the detection means, and third correction for correcting the correction torque according to the position of the front working device detected by the third detection means. And a fourth means for controlling to reduce the maximum absorption torque of the hydraulic pump by a correction torque corrected by the second means and the third means. The traveling hydraulic working machine according to claim 2,
When the third detecting means detects that the front working device has been displaced to a certain position, the third means corrects the correction torque to be reduced or zero. Hydraulic work machine. The traveling hydraulic working machine according to claim 1,
Furthermore, it has a 4th detection means to detect the load condition of the said working actuator,
The pump torque correcting means detects the traveling means detected by the second detecting means when the first detecting means detects that the sum of the absorption torque and traveling torque of the hydraulic pump exceeds the output torque of the prime mover. The maximum absorption torque of the hydraulic pump is corrected in accordance with the operation status of the hydraulic pump, the position of the front work device detected by the third detection means, and the load status of the work actuator detected by the fourth detection means. A traveling hydraulic working machine that is characterized.

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