JP2008169593A - Engine load control device for work vehicle - Google Patents

Abstract

In a work vehicle equipped with a plurality of hydraulic pumps, when the deviation between the target engine speed and the actual engine speed is large, an operation capable of performing optimum engine load reduction control for each hydraulic pump. An engine load control device for a vehicle is provided.
An engine load control device is mounted on a wheel loader that transmits an output of an engine to a hydraulic actuator such as a loader hydraulic cylinder via a variable displacement hydraulic pump such as a loader hydraulic pump. ing. Based on the deviation Ne-No between the target engine speed Ne of the engine 1 and the actual engine speed No detected by the engine speed sensor 1a and the stroke sensor 17a, the controller 18 stores a map stored in the storage unit 22 in advance. Referring to this, the total value of the maximum absorption torque of each hydraulic pump 7-9 is adjusted, and the total value of this maximum absorption torque is appropriately distributed to each hydraulic pump 7-9.
[Selection] Figure 6

Description

  The present invention relates to an engine load control device for a work vehicle in which an output of an engine is transmitted to drive wheels and is transmitted to a plurality of hydraulic actuators including a work machine hydraulic actuator via a plurality of variable displacement hydraulic pumps.

  In general, in a work vehicle such as a wheel loader, an engine is a driving source for traveling and a driving source for working equipment. That is, the output of the engine is transmitted to the drive wheels via the torque converter, so that the vehicle can be driven. The engine drives various hydraulic pumps including a hydraulic pump of the work implement, and the hydraulic pump drives various devices such as the work implement via a hydraulic actuator. Specifically, for example, when the engine drives the steering hydraulic pump, the pressure oil discharged from the steering hydraulic pump can be supplied to the steering hydraulic cylinder to drive the steering mechanism. Further, when the engine drives the loader hydraulic pump, the pressure oil discharged from the loader hydraulic pump is supplied to the loader hydraulic cylinder to drive the loader.

Thus, in the wheel loader, the output of one engine is used for both driving for driving and driving various devices such as work machines. For this reason, the magnitude | size of the engine output used for driving | running | working drive will change according to the magnitude | size of the load concerning a working machine etc.
For example, when the engine speed is at a low idle speed (idling state), the increase in engine torque with respect to a sudden increase in hydraulic load becomes slower than when the engine speed is in a high speed range. Therefore, when an operation is performed in which the high load is suddenly applied, such as lifting the loader loaded with the steering wheel turned off while idling, the engine will not catch up with the sudden increase in hydraulic load, and the engine will stop. There is a case.

  In addition, when the loader or steering mechanism is operated while driving, the engine output is consumed as a hydraulic load for work equipment and steering. I can't. For this reason, the response to the accelerator operation by the operator is reduced, such as a sufficient traction force cannot be obtained or a long time is required to increase the vehicle speed.

For example, in Patent Document 1, when performing speed sensing control for controlling the maximum absorption torque of the hydraulic pump based on the deviation between the target rotational speed and the actual rotational speed, if the engine output has a margin, the engine output A pump torque control device for a hydraulic construction machine capable of effectively utilizing the above is disclosed.
Further, in Patent Document 2, when it is determined that the actual engine speed has decreased below a threshold value, the absorption torque of the variable displacement hydraulic pump is reduced to prevent the engine from being stopped when a sudden load is applied. An engine load control device is disclosed.
JP 2004-108155 A (published April 8, 2004) JP 2006-70877 A (published March 16, 2006)

However, the conventional pump torque control device has the following problems.
That is, in the pump torque control device disclosed in the above publication, the maximum absorption torque of the pump is controlled based on the deviation between the target rotational speed and the actual rotational speed or the actual rotational speed of the engine. The operational importance of each pump is different for each pump, and if the same control is performed for all pumps, the response due to the operation of the work implement lever, steering, etc. will deteriorate, and workability will be reduced. There is a risk of lowering.

  An object of the present invention is to perform optimal engine load reduction control for each hydraulic pump when the deviation between the target engine speed and the actual engine speed is large in a work vehicle equipped with a plurality of hydraulic pumps. An object of the present invention is to provide an engine load control device for a work vehicle.

  An engine load control device for a work vehicle according to a first aspect of the present invention is configured such that an output of an engine whose rotational speed is controlled by a rotational speed instruction device is transmitted to a drive wheel, and a plurality of variable displacement hydraulic pumps are used. An engine load control device for a work vehicle that is transmitted to a hydraulic actuator, and includes a target rotation speed detection unit, an actual rotation speed detection unit, a deviation amount calculation unit, a storage unit, and a control unit. The target rotational speed detection unit detects the target rotational speed of the engine in response to the instruction content from the rotational speed instruction device. The actual rotational speed detection unit detects the actual rotational speed of the engine. The deviation amount calculation unit calculates a difference between the detection result in the target rotation number detection unit and the detection result in the actual rotation number detection unit. The storage unit stores a map that defines the relationship between the deviation between the target engine speed and the actual engine speed and the maximum absorption torque of a plurality of variable displacement hydraulic pumps. The control unit refers to the map stored in the storage unit based on the detection result in the actual rotational speed detection unit and the calculation result in the deviation amount calculation unit, and determines the maximum absorption torque for the plurality of variable displacement hydraulic pumps. Set and control to reduce the total absorption torque of multiple variable displacement hydraulic pumps.

Here, the control unit detects the target engine speed and the actual engine speed, and based on the deviation amount and the actual engine speed, the engine target engine speed and the actual engine speed stored in the storage unit are detected. The maximum absorption torque for each variable displacement hydraulic pump is set with reference to a map showing the relationship between the magnitude of the deviation from the number and the maximum absorption torque of a plurality of variable displacement hydraulic pumps.
Here, the plurality of variable displacement hydraulic pumps include, for example, a steering hydraulic pump, a loader hydraulic pump that drives a work machine, and the like. Further, as the map, one or more graphs showing the relationship between the actual engine speed, the deviation between the target engine speed and the actual engine speed, and the maximum absorption torque of each variable displacement hydraulic pump are stored in the storage unit. Assume that it is stored.

  Thus, for example, when the engine speed difference is relatively large, referring to the map, the total number of variable displacement hydraulic pumps is adjusted so that the actual engine speed approaches the target engine speed as soon as possible. The absorption torque can be reduced, and the reduced total absorption torque can be appropriately distributed to each variable displacement hydraulic pump. As a result, by simply performing optimal control according to the characteristics and importance of each variable displacement hydraulic pump, compared to control that uniformly reduces the maximum absorption torque of a plurality of variable displacement hydraulic pumps, A work vehicle with high workability can be provided.

  According to a second aspect of the present invention, there is provided an engine load control device for a work vehicle, wherein an output of an engine whose rotation speed is controlled by a rotation speed instruction device is transmitted to a drive wheel, and a plurality of variable displacement hydraulic pumps are used. An engine load control device for a work vehicle that is transmitted to a hydraulic actuator, and includes a target rotation speed detection unit, an actual rotation speed detection unit, a deviation amount calculation unit, a storage unit, and a control unit. The target rotational speed detection unit detects the target rotational speed of the engine in response to the instruction content from the rotational speed instruction device. The actual rotational speed detection unit detects the actual rotational speed of the engine. The deviation amount calculation unit calculates a difference between the detection result in the target rotation number detection unit and the detection result in the actual rotation number detection unit. The storage unit stores a map that defines the relationship between the deviation between the target engine speed and the actual engine speed, the actual engine speed, and the maximum absorption torque of a plurality of variable displacement hydraulic pumps. Yes. The control unit refers to the map according to the detection result in the actual rotational speed detection unit, and determines the distribution of the absorption torque for the plurality of variable displacement hydraulic pumps.

  Here, the control unit detects the target engine speed and the actual engine speed, and based on the engine actual engine speed, the deviation between the engine target engine speed stored in the storage unit and the actual engine speed is determined. The maximum absorption torque for each variable displacement hydraulic pump is set with reference to a three-dimensional map showing the relationship between the size of the engine, the actual engine speed, and the maximum absorption torque of a plurality of variable displacement hydraulic pumps.

  Here, the plurality of variable displacement hydraulic pumps include, for example, a steering hydraulic pump, a loader hydraulic pump that drives a work machine, and the like. Further, as the map, a three-dimensional graph showing the relationship between the actual engine speed, the deviation between the target engine speed and the actual engine speed, and the maximum absorption torque of each variable displacement hydraulic pump is stored in the storage unit. Assume that one or more are stored.

  Thus, for example, based on the relationship between the engine speed difference and the actual engine speed, a plurality of variable capacities are referred to in order to bring the actual engine speed closer to the target engine speed as soon as possible with reference to the map. The total absorption torque of the hydraulic pump can be reduced, and the reduced total absorption torque can be appropriately distributed to each variable displacement hydraulic pump. As a result, by simply performing optimal control according to the characteristics and importance of each variable displacement hydraulic pump, compared to control that uniformly reduces the maximum absorption torque of a plurality of variable displacement hydraulic pumps, A work vehicle with high workability can be provided.

An engine load control device for a work vehicle according to a third invention is the engine load control device for a work vehicle according to the first or second invention, wherein the map indicates the importance of a plurality of variable displacement hydraulic pumps. Accordingly, the distribution ratio of the maximum absorption torque is set for each of the plurality of variable displacement hydraulic pumps.
Here, as the map stored in the storage unit, a map in which the distribution of the maximum absorption torque of each variable displacement hydraulic pump is set according to the importance of each variable displacement hydraulic pump is used.
As a result, before setting the distribution ratio of the absorption torque for each variable displacement hydraulic pump, first, by setting an upper limit on the total of the maximum absorption torque of each variable displacement hydraulic pump, Regardless of the distribution ratio of the absorption torque, the load on the engine can be surely reduced.

  An engine load control device for a work vehicle according to a fourth invention is the engine load control device for a work vehicle according to the first or second invention, wherein the map includes a target engine speed and an actual engine speed. The upper limit of the total value of the maximum absorption torque is set for each of the plurality of variable displacement hydraulic pumps.

Here, as the map stored in the storage unit, a map in which the upper limit value of the total value of the maximum absorption torque of each variable displacement hydraulic pump is set according to the magnitude of the deviation is used.
As a result, for example, when the actual rotational speed is relatively large, the engine output is also increasing, so the maximum absorption torque is set with a nearly uniform distribution ratio regardless of the importance of each variable displacement hydraulic pump. be able to. On the other hand, when the actual engine speed is relatively small, the engine output is low. Therefore, considering the importance of each variable displacement hydraulic pump, a large amount is distributed to the variable displacement hydraulic pumps with high importance. The ratio can be determined. As a result, the absorption torque can be appropriately distributed to each variable displacement hydraulic pump according to the output of the engine.

An engine load control device for a work vehicle according to a fifth invention is the engine load control device for a work vehicle according to the second invention, wherein the map includes a plurality of variable capacity types according to the actual engine speed. The upper limit of the total value of the maximum absorption torque is set for each hydraulic pump.
Here, as the map stored in the storage unit, an upper limit of the total value of the maximum absorption torque is set for each of the plurality of variable displacement hydraulic pumps according to the actual engine speed.

  Thereby, referring to the three-dimensional map of the actual engine speed, the deviation between the target engine speed and the actual engine speed, and the maximum absorption torque of each variable displacement hydraulic pump, in particular, based on the detected actual engine speed. The maximum absorption torque can be set for each variable displacement hydraulic pump so as not to exceed the upper limit of the total value of the maximum absorption torque of each variable displacement hydraulic pump that has been set. As a result, the absorption torque can be appropriately distributed to each variable displacement hydraulic pump in accordance with the actual engine speed.

An engine load control device for a work vehicle according to a sixth invention is the engine load control device for a work vehicle according to any one of the first to fifth inventions, wherein the plurality of variable displacement hydraulic pumps include: At least one of a steering hydraulic pump, a fan hydraulic pump, and a loader hydraulic pump is included.
Here, a plurality of variables such as a steering hydraulic pump corresponding to the steering for determining the traveling direction of the work vehicle, a fan hydraulic pump for driving a cooling fan included in a cooling unit, a loader hydraulic pump for driving a work machine, etc. A displacement type hydraulic pump is included as a control target for engine load reduction control.

  For this reason, for example, for the hydraulic pump for steering, which is the most important at the time of work from the viewpoint of safety, the absorption torque distribution ratio is set higher, and for the fan hydraulic pump that has a relatively small influence, the absorption torque distribution ratio Can be set lower. As a result, by setting priorities for a plurality of hydraulic pumps with different importance in terms of safety and work, it is possible to appropriately distribute absorption torque and prevent deterioration in workability as well as engine blow-up performance. it can.

An engine load control device for a work vehicle according to a seventh aspect is the engine load control device for a work vehicle according to any one of the first to sixth aspects, wherein the control unit is a variable displacement hydraulic pump. Control is performed to reduce the maximum absorption torque of the variable displacement hydraulic pump by controlling the EPC current that controls the discharge amount.
Here, when reducing the maximum absorption torque of the variable displacement hydraulic pump, the control unit controls the EPC current that adjusts the discharge amount of the variable displacement hydraulic pump.

  Thereby, the magnitude of the maximum absorption torque in the variable displacement hydraulic pump can be easily controlled by adjusting the discharge amount of the variable displacement hydraulic pump.

An engine load control device for a work vehicle according to an eighth aspect of the present invention is the engine load control device for a work vehicle according to any one of the first to seventh aspects, wherein the rotational speed instruction device is the engine rotational speed. This is an accelerator pedal that adjusts.
Here, an accelerator pedal is used as the rotation speed instruction device.
As a result, the target rotational speed detection unit can easily detect the target rotational speed in accordance with the depression amount of the accelerator pedal.

  According to the engine load control device for a work vehicle according to the present invention, the characteristics and importance of each variable displacement hydraulic pump are compared with a control that simply reduces the maximum absorption torque of a plurality of variable displacement hydraulic pumps uniformly. A work vehicle with high workability can be provided by performing optimal control according to the above.

A wheel loader equipped with a hydraulic circuit control device according to an embodiment of the present invention will be described below with reference to FIGS.
[Configuration of wheel loader 50]
As shown in FIG. 1, a wheel loader (work vehicle) 50 according to an embodiment of the present invention is attached to a vehicle body 51, a lift arm 52 attached to a front portion of the vehicle body, and a tip of the lift arm 52. A bucket 53, four tires 54 that rotate while supporting the vehicle body 51 to travel the vehicle body, and a cab 55 mounted on the upper portion of the vehicle body 51 are provided.

  The vehicle body 51 includes an engine room for storing the engine 1 (see FIG. 2), a control valve for driving the lift arm 52 and the bucket 53, actuators (hydraulic cylinders 13, 14, hydraulic motor 15), and the like ( Control unit, deviation amount calculation unit) 18 (see FIG. 2). Further, as shown in FIG. 2, the engine 1, the controller 18, and the like are mounted on the vehicle body 51. The configuration of the control block shown in FIG. 2 will be described in detail later.

The lift arm 52 is an arm member for lifting the bucket 53 attached to the tip, and is driven by a lift cylinder provided therewith.
The bucket 53 is attached to the tip of the lift arm 52 and is dumped and tilted by a bucket cylinder.
The cab 55 has a driver protection structure (ROPS structure) at the time of falling, and forms an operator's cab configured by combining a plurality of steel pipes and steel plates. The cab 55 is disposed slightly ahead of the center portion of the vehicle body 51.

[Internal configuration of wheel loader 50]
(Main configuration)
As shown in FIG. 2, the wheel loader 50 mainly includes an engine 1, a mechanism on the traveling side driven by the engine 1, a mechanism on the work machine side, a controller 18 for controlling these mechanisms, and the like. An engine load control device (engine load control device for work vehicle) 30 is provided inside. Between the engine 1 and each mechanism, a PTO (power take-off) mechanism 6 including a gear and a shaft is provided.

  The engine 1 is a diesel engine, and its output is controlled by adjusting the amount of fuel injected into the cylinder. Such adjustment of the amount of fuel injected into the cylinder is performed by controlling a governor attached to the fuel pump of the engine 1. In this embodiment, a general all speed control type governor is used as the governor. That is, the fuel injection amount is increased or decreased by the governor so that there is no difference between the target rotational speed corresponding to the depression amount of the accelerator pedal (rotational speed indicating device) 17 and the actual engine rotational speed.

  The travel side mechanism includes a torque converter 2 to which the output of the engine 1 is input, a transmission 3 coupled to the torque converter 2, a differential gear 4 coupled to the output shaft of the transmission 3, and drive wheels 5. ing. The transmission 3 includes a forward hydraulic clutch, a reverse hydraulic clutch, a plurality of shift clutches, and the like, and forward / reverse switching and shift are performed by controlling each hydraulic clutch on and off.

The wheel loader 50 is driven by the engine 1 in addition to a traveling system mechanism, mainly a steering mechanism (not shown), a loader such as a lift arm 52 and a bucket 53 provided at the front of the vehicle body, And a fan 16.
In order to drive each of these mechanisms, hydraulic pumps (variable displacement hydraulic pumps) 7 to 9 and actuators (hydraulic cylinders 13 and 14 and hydraulic motor 15) are provided. That is, in order to drive the steering mechanism, a steering hydraulic pump 7, a steering control valve 11, and a steering hydraulic cylinder 13 connected to the steering mechanism are provided. In order to drive the loader, a loader hydraulic pump 8, a loader control valve 12, and a loader hydraulic cylinder 14 connected to the loader are provided. Further, a fan hydraulic pump 9 and a fan hydraulic motor 15 are provided to drive the fan 16. These hydraulic pumps 7, 8, 9 are connected to the engine 1 via the PTO mechanism 6. A torque converter pump 10 is also provided for the torque converter 2. The torque charge pump 10 is connected to the engine 1 via the PTO mechanism 6.

The steering hydraulic pump 7, the loader hydraulic pump 8, and the fan hydraulic pump 9 are variable displacement hydraulic pumps having swash plates 7a, 8a, and 9a, respectively, and the swash plates 7a, 8a, and 9a are tilted. The pump capacity q (cc / rev) can be controlled by changing the angle.
(Configuration for engine load control)
Furthermore, in the wheel loader 50 of this embodiment, in order to perform load control of the engine 1, as shown in FIG. 2, the engine load control device 30 detects an engine speed sensor (actual speed detection unit) that detects the engine speed. ) 1a, a stroke sensor (target rotational speed detector) 17a for detecting the opening degree of the accelerator pedal 17, a discharge pressure sensor 7b for detecting the discharge pressure of the steering hydraulic pump 7a, and a controller 18. Yes.

  The controller 18 is a microcomputer comprising a CPU, a RAM, a ROM, etc. As shown in FIG. 2, the sensor output of the engine speed sensor 1a, the sensor output of the stroke sensor 17a of the accelerator pedal 17, and the steering hydraulic pump 7a. Sensor output of the discharge pressure sensor 7b is input. The controller 18 outputs a control signal to the engine 1 and the hydraulic pumps 7, 8, 9.

For example, in order to control the loader hydraulic pump 8 on the loader side, a control block as shown in FIG. 3 is formed. FIG. 3 shows a configuration for controlling the loader hydraulic pump 8, but the same control block is configured for the other variable displacement hydraulic pumps 7 and 9. Is omitted.
In the present embodiment, as shown in FIG. 3, a PC valve (horsepower control valve) 19 and a servo valve 20 are provided to control the swash plate 8 a of the hydraulic pump 8. A discharge pressure Pp (kg / cm ² ) of the hydraulic pump 8 is input to the PC valve 19 as a pilot pressure, and a control signal i1 from the controller 18 is input. The servo valve 20 is supplied with pressure oil from the PC valve 19, thereby controlling the capacity q of the hydraulic pump 8. More specifically, the swash plate 8a of the hydraulic pump 8 is controlled by the PC valve 19 so that the product of the discharge pressure Pp of the hydraulic pump 8 and the capacity q of the hydraulic pump 8 does not exceed a certain torque. Therefore, if the rotational speed of the engine 1 is constant, the swash plate 8a of the hydraulic pump 8 is controlled so that the product of the discharge pressure Pp of the hydraulic pump 8 and the capacity q of the hydraulic pump 8 does not exceed a constant horsepower. .

  Further, as shown in FIG. 4, the controller 18 includes an accelerator pedal signal (accelerator opening), an engine speed, a gear signal, an FNR (forward / neutral / reverse) signal, a boom cylinder bottom pressure, and a loader hydraulic pump. The discharge pressure, steering hydraulic pump discharge pressure, TM (transmission) speed sensor signal, and the like are input. The controller 18 outputs a throttle change signal to the engine controller 21, and the engine controller 21 outputs a fuel injection injector control signal. Further, the controller 18 calculates an optimum value of the loader hydraulic pump PC-EPC current according to the input accelerator pedal signal, engine speed, etc., and outputs it to the hydraulic pump 8. Similarly, the steering hydraulic pump PC-EPC current and the fan hydraulic pump PC-EPC current are output to the other hydraulic pumps 7 and 9, respectively.

  Specifically, the controller 18 determines a PC-EPC current (for realizing an improvement in engine 1 blowing performance and an engine stall prevention function) according to the magnitude of the deviation between the target engine speed and the actual engine speed. mA). Note that the PC-EPC current corresponds to the control signal i1 output from the controller 18 to the PC valve 19 shown in FIG. 3, and the tilt angle of the swash plate 8a becomes smaller as the current value becomes larger. The discharge amount is reduced, and the absorption torque of the hydraulic pump is reduced (pump capacity is reduced). Therefore, by controlling this PC-EPC current to reduce the maximum absorption torque in the hydraulic pump 8, the load on the engine 1 can be reduced as a result. The same applies to the other hydraulic pumps 7 and 9.

<Operation of each mechanism>
As shown in FIG. 2, the output of the engine 1 is input to the transmission 3 via the torque converter 2, and in this transmission 3, the forward / reverse movement is switched by the on / off control of the forward / backward hydraulic clutch. Further, shift control is performed by on / off control of the shift hydraulic clutch. The output of the transmission 3 is transmitted to the drive wheels 5 through the differential gear 4 as shown in FIG.

On the other hand, the output of the engine 1 is transmitted to the hydraulic pumps 7, 8, 9, and 10 through the PTO mechanism 6 as shown in FIG. 2, and the hydraulic pumps are driven.
When the steering hydraulic pump 7 is driven, the discharged pressure oil is supplied to the steering hydraulic cylinder 13 via the steering control valve 11 as shown in FIG. When pressure oil is supplied to the steering hydraulic cylinder 13, the steering mechanism is actuated to turn the vehicle body in a desired direction. Note that the spool of the steering control valve 11 moves in response to an operation of a steering handle (not shown). Therefore, the opening area of the steering control valve 11 changes accordingly, and the flow rate supplied to the steering hydraulic cylinder 13 changes.

  When the loader hydraulic pump 8 is driven, the discharged pressure oil is supplied to the loader hydraulic cylinder 14 via the loader control valve 12, as shown in FIG. When pressure oil is supplied to the loader hydraulic cylinder 14, the loader operates. That is, the boom constituting the loader can be raised or lowered to tilt the bucket. Note that the spool of the loader control valve 12 moves in response to an operation of a work machine operation lever (not shown). For this reason, the opening area of the control valve 12 changes accordingly, and the flow rate supplied to the loader hydraulic cylinder 14 changes.

When the fan hydraulic pump 9 is driven, the discharged pressure oil is supplied to the fan hydraulic motor 15 and the cooling fan 16 is operated, as shown in FIG.
The torque converter pump 10 is a fixed displacement gear pump, and when the torque converter pump 10 is driven, the discharge pressure oil is supplied to the torque converter 2.
<Control of engine 1>
Next, control of the engine 1 by the accelerator pedal 17 will be described. FIG. 5 shows the relationship between the engine speed N, the engine torque Te, and the hydraulic load. In FIG. 5, the area defined by the maximum torque line indicates the performance that the engine 1 can output. The engine 1 is controlled by the governor so that the engine torque does not exceed the maximum torque line and reach the exhaust smoke limit, and the engine speed N exceeds the high idle speed _NH and does not overspeed.

For example, when the accelerator pedal 17 is depressed to its maximum, sets the maximum target rotational speed corresponding to the depression amount of the accelerator pedal 17 by the controller 18, the governor, fastest connecting the rated point and the high idle point N _H Speed regulation is performed on the regulation line Fe. Becomes small depression amount of the accelerator pedal 17, the target rotational speed with the smaller, regulation line Fe-1, Fe-2, ··· Fe-n ··· F L is determined sequentially, each regulation line on The speed is controlled.

When the depression amount of the accelerator pedal 17 is not minimized, that is depressed is set low idle rotational speed N _L as the target rotational speed, the governor in regulation line F _L connecting the low idle point N _L is performed. At this time, when the hydraulic load Tp fluctuates as indicated by an arrow A, the matching point V where the output of the engine 1 and the pump absorption horsepower balance moves on the regulation line according to the fluctuation.

<Engine load reduction control>
In the engine load control device 30 of the present embodiment, first, each hydraulic pump is used to reduce the absorption torque of the loader hydraulic pump 8 based on the magnitude of the deviation between the target rotational speed and the actual rotational speed of the engine 1. The upper limit value of the total absorption torque in 7 to 9 is set.
Specifically, for example, in the wheel loader 50, when the working machine operating lever and the accelerator pedal 17 are suddenly operated almost simultaneously from the low idle state, the controller 18 stores in the storage unit 22 (see FIG. 4) in advance. The following control is performed with reference to the graph (map) shown in FIG.

  That is, the controller 18 outputs the target rotational speed of the engine 1 corresponding to the depression amount of the accelerator pedal 17 and the actual rotational speed (actual rotational speed) of the engine 1 as outputs from the stroke sensor 17a and the engine rotational speed sensor 1a. Receive. Then, the controller 18 refers to the graph shown in FIG. 6 according to the deviation between the target rotational speed and the actual rotational speed, and suppresses the total absorption in order to suppress the sum of the maximum absorption torque in each of the hydraulic pumps 7 to 9. Set the upper limit of torque.

  As a result, most of the engine output can be prevented from being used on the hydraulic pumps 7 to 9 side, and the engine speed can be increased smoothly. Then, as the actual rotational speed of the engine 1 detected by the engine rotational speed sensor 1A increases, control is performed so that the discharge amount of each of the hydraulic pumps 7 to 9 is increased, thereby improving the blowing performance of the engine 1. In addition, the operation speed of the work machine or the like can be improved. For this reason, since the operator can feel that the engine 1 is blown up with an image close to his / her own depression amount, the operator does not depress the accelerator pedal 17 excessively. Therefore, it is possible to avoid a reduction in fuel consumption due to the engine 1 not being blown up when the operating lever for work implement and the accelerator pedal 17 are operated largely at the same time.

In addition, when setting the upper limit of the total of the maximum absorption torque of all the hydraulic pumps 7-9 like this embodiment, the sum of the absorption torque in all the hydraulic pumps 7-9 will be below a predetermined value. Control may be performed with reference to the map set as described above.
<Contents of maximum absorption torque control>
Here, the control for reducing the maximum absorption torque of the hydraulic pumps 7 to 9 by the above-described control will be described in detail by taking the loader hydraulic pump 8 as an example.

As described above, the PC valve 19 inputs the discharge pressure Pp of the hydraulic pump 8 as a pilot pressure, and supplies the drive pressure oil corresponding to the discharge pressure Pp to the servo valve 20, thereby increasing the capacity q of the hydraulic pump 8. I have control.
In the loader hydraulic pump 8, the pump capacity q is controlled in accordance with the pump discharge pressure within a range where the hydraulic load, that is, the absorption torque does not exceed the maximum absorption torque.

Here, the control signal i1 is input to the PC valve 19 from the controller 18 by the control described above, and the maximum absorption torque is controlled in accordance with the control signal i1. As the current value applied to the PC valve 19 by the control signal i1 increases, the maximum absorption torque value is set to a smaller value.
Therefore, by providing the PC valve 19 with the PC-EPC current value obtained by the above-described control, the absorption torque of the loader hydraulic pump 8 is reduced with reference to the target engine speed Ne and the actual engine speed No. can do.

<Absorption torque distribution control for each hydraulic pump 7-9>
In the engine load control device 30 of the present embodiment, the maximum absorption torque of each of the hydraulic pumps 7 to 9 is set, and the total absorption torque corresponding to the deviation of the rotation speed is set. Then, based on the actual rotational speed No of the engine 1 at that time, the distribution ratio of the total absorption torque to the hydraulic pumps 7 to 9 is determined with reference to the graph shown in FIG.

That is, the controller 18 refers to the actual rotational speed No. with reference to the graph shown in FIG. 6 for the total value of the absorption torque that is the upper limit value set based on the deviation between the target rotational speed Ne and the actual rotational speed No. Accordingly, the distribution ratio for the three hydraulic pumps 7 to 9 is set.
Specifically, in the map represented as the graph of FIG. 6, in principle, the steering hydraulic pump 7 ≈ the loader hydraulic pump 8> the fan hydraulic pump 9 according to the actual rotational speed No. The distribution ratio of the absorption torque to the steering hydraulic pump 7, the loader hydraulic pump 8, and the fan hydraulic pump 9 is set. This priority is set according to whether the importance is high in consideration of safety and operation aspects when operating the wheel loader 50. For example, the steering and loader are particularly important when working with the wheel loader 50, and therefore, the steering hydraulic pump 7 and the loader hydraulic pump 8 have priority over the fan hydraulic pump 9. It is set to be high.

  For example, when the rotational speed deviation Ne-No is a relatively small value (200 rpm), as shown in FIG. 7, the total of the maximum absorption torque is excluded except for the actual rotational speed No 1 regardless of the actual rotational speed No. (Total) is 90% (in the case of actual rotational speed No = 2300, the output of the engine 1 is large, so it is exceptionally 80%). Further, as the value of the deviation Ne-No increases, the total maximum absorption torque of each of the hydraulic pumps 7 to 9 is reduced to 50 to 60% in order to reduce the load on the engine 1.

  And as distribution ratio of the absorption torque with respect to each hydraulic pump 7-9 at that time, as shown in FIG. 8, when the sum total of the absorption torque to which the upper limit is set is 10, the deviation Ne-No is a relatively small value ( 200 rpm), the maximum absorption torque is set for the steering hydraulic pump 7, the loader hydraulic pump 8, and the fan hydraulic pump 9 at a distribution ratio of 3: 6: 1. That is, when the rotation speed deviation Ne-No is a relatively small value (200 rpm), the distribution ratio of the loader hydraulic pump 8 is set to be the highest.

  On the other hand, when the actual rotational speed No = 750 rpm and the rotational speed deviation Ne−No = 1500, the steering hydraulic pump 7, the loader hydraulic pump 8, and the fan hydraulic pump 9 are 5: The maximum absorption torque is set by the distribution ratio of 4: 1. That is, when the rotation speed deviation Ne-No is a relatively large value (1500 rpm), the distribution ratio of the steering hydraulic pump 7 is set to be higher than the distribution ratio of the loader hydraulic pump 8. Therefore, when the actual rotational speed No = 750 rpm and the rotational speed deviation Ne−No = 1500, the total value of the maximum absorption torque is also reduced to 50% as shown in FIG. In the distribution ratio setting control when the total torque value is reduced, the steering hydraulic pump 7 is set to have the highest priority.

Similarly, even when the actual rotational speed No = 1000 rpm, when the rotational speed deviation Ne-No is changed from 200 to 1200, as shown in FIG. 7, the total maximum absorption torque is also reduced from 90% to 60%. Therefore, the distribution ratio to each of the hydraulic pumps 7 to 9 in that case is also changed from 3: 6: 1 to 4: 5: 1.
Further, when the actual rotational speed No = 1300 rpm, similarly, when the rotational speed deviation Ne-No is changed from 200 to 1000, as shown in FIG. 7, the total maximum absorption torque is also reduced from 90% to 60%. Therefore, the distribution ratio to each of the hydraulic pumps 7 to 9 in that case is also changed from 3: 6: 1 to 4: 5: 1.

  In the engine load control device 30 according to the present embodiment, as described above, first, the controller 18 has three hydraulic pressures according to the magnitude of the deviation Ne-No between the target rotational speed Ne of the engine 1 and the actual rotational speed No. An upper limit is set to the total value of the maximum absorption torques of the pumps 7-9. Then, the controller 18 sets the distribution ratio of the total value of the maximum absorption torque based on the actual rotational speed No.

  Thereby, for example, in the low idle state, when the steering, the working machine lever, or the like is operated almost simultaneously with the depression of the accelerator pedal 17, the deviation between the initial target rotational speed Ne and the actual rotational speed No. Since the Ne-No becomes large, by setting the upper limit of the total value of the maximum absorption torque set for the three hydraulic pumps 7 to 9, the load on the engine 1 is reduced and the engine 1 can be blown up. Can be improved. Then, the total value of the maximum absorption torque set with the upper limit value is set as a distribution ratio for each of the hydraulic pumps 7 to 9 in accordance with the actual rotational speed No. When the actual rotational speed No is low, the engine 1 Since the output is also small, the maximum absorption torque can be appropriately distributed according to the priority of each hydraulic pump 7-9.

As a result, the maximum absorption torque is appropriately distributed according to the importance of each hydraulic pump 7 to 9 even when the output of the engine 1 is low while improving the blow-up performance of the engine 1 from the low idle state. It is possible to improve the operability and responsiveness of the steering and work equipment.
<Flow of engine 1 load reduction control>
Here, the flow of the load reduction control of the engine 1 described above will be described with reference to FIG.

That is, in step S1, for example, when the operating lever for the work implement and the accelerator pedal 17 are operated almost simultaneously, in step S2, the controller 18 detects the detection results of the engine speed sensor 1a and the stroke sensor 17a of the accelerator pedal 17. Based on the above, the deviation between the target rotational speed Ne and the actual rotational speed No is calculated.
Next, in step S3, the controller 18 determines whether or not this deviation (Ne2-No2)> 200. Here, if the rotational speed deviation satisfies the above condition, the process proceeds to step S4 as it is, and if the above condition is not satisfied, the process returns to step S1 so that the work implement operating lever and the accelerator pedal 17 are almost simultaneously. Wait until it is detected that it has been operated. Here, the deviation (Ne2-No2)> 200 is set as the start condition of the engine load reduction control for reducing the maximum absorption torque of the hydraulic pumps 7 to 9 because the control for reducing the maximum absorption torque from 100% is started. This is because the minimum value of the deviation of the rotational speed is Ne-No> 200 in the loader hydraulic pump 8.

Next, in step S4, the upper limit of the total value of the maximum absorption torques of the hydraulic pumps 7 to 9 is set according to the actual rotational speed No of the engine 1.
Next, in step S5, based on the actual rotational speed No of the engine 1, a ratio for distributing the maximum absorption torque for which the upper limit value has been set in step S4 to the respective hydraulic pumps 7 to 9 is set.

Next, in step S6, control for reducing the maximum absorption torque of each of the hydraulic pumps 7 to 9 is performed based on the distribution ratio set in step S5.
[Characteristics of engine load control device 30]
(1)
As shown in FIG. 2, the engine load control device 30 of the present embodiment transmits the output of the engine 1 to a hydraulic actuator such as a loader hydraulic cylinder 14 via a variable displacement hydraulic pump such as a loader hydraulic pump 8. The wheel loader 50 is mounted. The controller 18 is stored in advance in the storage unit 22 based on the deviation Ne-No between the target engine speed Ne of the engine 1 and the actual engine speed No detected by the engine speed sensor 1a and the stroke sensor 17a. With reference to the graph shown in FIG. 6, the total value of the maximum absorption torques of the hydraulic pumps 7 to 9 is adjusted, and the total value of the maximum absorption torques is appropriately distributed to the hydraulic pumps 7 to 9.

  As a result, when the deviation between the target rotational speed Ne and the actual rotational speed No is large and the load on the engine 1 is large, the engine output to the three hydraulic pumps 7 to 9 is reduced, and the blowing performance of the engine 1 is increased. Can be improved. Furthermore, the total value of the maximum absorption torque set at this time is appropriately distributed to each of the hydraulic pumps 7 to 9 according to the actual rotational speed No, for example, so that the reduced maximum absorption torque is given priority. Can be preferentially allocated to high hydraulic pumps. As a result, it is possible to improve the work efficiency of the wheel loader 50 by improving the operability and responsiveness of the work machine, steering, etc., as well as the ability to blow up the engine 1.

(2)
In the engine load control device 30 of the present embodiment, as shown in FIG. 6 and the like, the controller 18 has a maximum absorption torque for highly important hydraulic pumps such as the steering hydraulic pump 7 and the loader hydraulic pump 8. A map set so as to be distributed in large numbers is stored in the storage unit 22.

Thereby, for example, even when the output of the engine 1 is small as in the low idle state, about half of the maximum absorption torque that has been greatly reduced is distributed to the steering hydraulic pumps 7 and the like, so that each hydraulic pump 7 The absorption torque can be appropriately distributed according to the importance of ˜9.
(3)
In the engine load control device 30 of the present embodiment, as shown in FIG. 9, first, based on the deviation Ne-No between the target rotational speed Ne of the engine 1 and the actual rotational speed No, the maximum in each hydraulic pump 7-9. Set an upper limit for the total absorption torque.

Thereby, when the deviation between the target rotational speed Ne and the actual rotational speed No is large and the engine 1 is loaded, first, the total value of the maximum absorption torques of the hydraulic pumps 7 to 9 is set to be reduced. Thus, regardless of the distribution ratio of the absorption torque to each of the hydraulic pumps 7 to 9, it is possible to reliably reduce the addition of the engine 1 and improve the blowing performance.
(4)
In the engine load control device 30 of the present embodiment, as shown in FIG. 9, first, based on the deviation Ne-No between the target rotational speed Ne of the engine 1 and the actual rotational speed No, the maximum in each hydraulic pump 7-9. After setting the upper limit on the total value of the absorption torque, the distribution ratio of the absorption torque to each of the hydraulic pumps 7 to 9 is set based on the actual rotational speed No.

  Thus, the distribution ratio of the absorption torque to each of the hydraulic pumps 7 to 9 is changed between the case where the actual rotational speed No is small and the output of the engine 1 is small and the case where the actual rotational speed No is large and the output of the engine 1 is large. Can do. As a result, for example, when the actual rotational speed No is small and the output of the engine 1 is low, the control can be performed so that a small absorption torque is preferentially distributed to the steering hydraulic pump 7 having high importance. it can. Therefore, no matter how small the output of the engine 1 is, it is possible to avoid the danger that the steering response will be reduced.

(5)
In the engine load control device 30 of the present embodiment, as shown in FIG. 2, the steering hydraulic pump 7, the loader hydraulic pump 8, and the fan hydraulic pump 9 are controlled as objects to be controlled by the controller 18. Used.
Thereby, when there is a difference in importance in each of the hydraulic pumps 7 to 9, for example, when the actual rotational speed No of the engine 1 is small and the output of the engine 1 is low, the responsiveness of operations such as steering is reduced. Therefore, the distribution of the maximum absorption torque of the steering hydraulic pump 7 can be set to be large. As a result, it is possible to maintain the responsiveness at the time of operations such as steering while minimizing the load on the engine 1.

(6)
In the engine load control device 30 of the present embodiment, as shown in FIG. 3 and the like, when performing control to reduce the maximum absorption torque of each of the hydraulic pumps 7 to 9 according to the rotation speed deviation Ne-No, Control is performed by adjusting the PC-EPC current applied to the PC valve 19 connected to each hydraulic pump 7-9.

Thus, by controlling the PC-EPC current in the controller 18, the discharge amount in each of the hydraulic pumps 7 to 9 can be easily adjusted, and the reduction amount of the maximum absorption torque can be adjusted.
(7)
In the engine load control device 30 of the present embodiment, as shown in FIG. 2, a stroke sensor 17 a attached to the accelerator pedal 17 is used as means for detecting the target rotational speed of the engine 1.

As a result, the target rotational speed of the engine 1 can be detected accurately and appropriately according to the amount of depression of the accelerator pedal 17, so that the rotational speed deviation Ne-No can be accurately calculated.
[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.

(A)
In the above embodiment, when the control for reducing the maximum absorption torque of the plurality of hydraulic pumps 7 to 9 is performed when the deviation between the target rotational speed of the engine 1 and the actual rotational speed is equal to or greater than a predetermined value, the steering hydraulic pressure Set a priority in the order of the pump 7, the loader hydraulic pump 8, and the fan hydraulic pump 9, and refer to a map (see FIG. 6) set to distribute the absorption torque to each of the hydraulic pumps 7-9. Thus, an example of performing control has been described. However, the present invention is not limited to this.

As the priority set for each hydraulic pump, for example, the loader hydraulic pump, the steering hydraulic pump, and the fan hydraulic pump are set in this order, and control is performed with reference to a map set to distribute absorption torque. May be performed.
Further, the distribution ratio of the maximum absorption torque according to the priority is not limited to the example of the above embodiment, and a plurality of maps may be prepared so that the distribution ratio can be changed as appropriate.

(B)
In the above embodiment, when the control for reducing the maximum absorption torque of the plurality of hydraulic pumps 7 to 9 is performed when the deviation between the target rotational speed of the engine 1 and the actual rotational speed is a predetermined value or more, the actual rotational speed is determined. The example in which the control is performed based on the map set so as to change the distribution ratio to each of the hydraulic pumps 7 to 9 according to the above has been described. However, the present invention is not limited to this.

For example, as shown in FIG. 11, control may be performed with reference to a map set to change the distribution ratio of the absorption torque to each hydraulic pump based on the target rotational speed instead of the actual rotational speed. Good.
In this case, the high target rotational speed means that the accelerator pedal is depressed to a deep position, for example, and therefore it is determined that the engine output is likely to increase when the target rotational speed is high. The distribution ratio of absorption torque to each hydraulic pump can be set. On the other hand, a low target speed means, for example, that the amount of accelerator pedal depression is shallow. Therefore, when the target speed is low, it is determined that the engine output is unlikely to increase, The distribution ratio of the absorption torque can be set.

(C)
In the said embodiment, the wheel loader 50 which mounted three hydraulic pumps (steering, loader, fan) 7-9 was mentioned as an example, and demonstrated as a hydraulic pump used as the control object which reduces maximum absorption torque. However, the present invention is not limited to this.
For example, the present invention can be applied to a work vehicle such as a wheel loader equipped with only one or four or more hydraulic pumps for work machines.

Note that, even in a work vehicle equipped with a plurality of hydraulic pumps as in the above embodiment, the maximum absorption torque is controlled by limiting the number of hydraulic pumps to be controlled to one or two. Good.
(D)
In the above embodiment, as shown in FIG. 2, an example in which the target rotational speed of the engine 1 is detected according to the depression amount of the accelerator pedal 17 detected by the stroke sensor 17 a has been described. However, the present invention is not limited to this.

For example, the present invention can be applied in the same manner as long as the operator indicates the rotation speed, such as an accelerator operation lever as the operator's intention.
(E)
In the above embodiment, as shown in FIG. 3 and the like, as a means for controlling the maximum absorption torque of each hydraulic pump 7-9, the PC-EPC current for adjusting the discharge amount in each hydraulic pump 7-9 is controlled. Explained with an example. However, the present invention is not limited to this.

For example, as means for adjusting the maximum absorption torque of each hydraulic pump, a method other than the adjustment of the PC-EPC current may be used.
(F)
In the above embodiment, the controller 18 as the engine load control device according to the present invention has been described with reference to an example in which the controller 18 is mounted on the wheel loader 50 as shown in FIG. However, the present invention is not limited to this.

  For example, the present invention can be applied to other construction machines such as a hydraulic excavator and a hydraulic crane.

  The engine load control device for a work vehicle according to the present invention is based on the characteristics and importance of each variable displacement hydraulic pump as compared with a control that simply reduces the maximum absorption torque of a plurality of variable displacement hydraulic pumps uniformly. By performing optimal control, it is possible to provide a work vehicle with high workability. Therefore, the present invention can be widely applied to various work vehicles that drive a hydraulic pump by the output of an engine.

The side view which shows the structure of the wheel loader carrying the engine load control apparatus of the working vehicle which concerns on one Embodiment of this invention. The control block diagram which shows the structure of the engine load control apparatus mounted in the wheel loader of FIG. The PC control block diagram of the hydraulic pump for loaders contained in FIG. FIG. 3 is a control block diagram showing input / output information of a controller included in FIG. 2. The graph which shows the relationship between an engine speed and an engine torque. The three-dimensional graph which shows the relationship between the total absorption torque of three hydraulic pumps, the actual rotational speed, and the deviation of target rotational speed. The table which shows the relationship between real rotation speed, rotation speed difference, and total absorption torque. The table which shows the relationship between a real rotation speed, a rotation speed difference, and the distribution ratio of the absorption torque to each hydraulic pump. The flowchart which shows the flow of the engine load reduction control which concerns on one Embodiment of this invention. The table which shows the distribution ratio of the absorption torque which changes according to each hydraulic pump and target rotation speed which were set to the engine load control apparatus of the working vehicle which concerns on other embodiment of this invention.

Explanation of symbols

1 Engine 1a Engine speed sensor (actual speed detector)
2 Torque converter 3 Transmission 4 Differential gear 5 Drive wheel 6 PTO (power take-off) mechanism 7 Steering hydraulic pump (variable displacement hydraulic pump)
7a Swash plate 7b Discharge pressure sensor 8 Hydraulic pump for loader (variable displacement hydraulic pump)
8a Swash plate 9 Hydraulic pump for fans (variable displacement hydraulic pump)
9a Swash plate 10 Torque lubrication hydraulic pump 11 Steering control valve 12 Loader control valve 13 Steering hydraulic cylinder (actuator)
14 Hydraulic cylinder for loader (actuator)
15 Fan hydraulic motor (actuator)
16 Fan 17 Accelerator pedal (rotation speed indicator)
17a Stroke sensor (target speed detector)
18 Controller (control unit, deviation amount calculation unit)
19 PC valve 20 Servo valve 21 Engine controller 22 Storage unit 30 Engine load control device (engine load control device for work vehicle)
50 wheel loaders (work vehicles)
51 Car body 52 Lift arm 53 Bucket 54 Tire 55 Cab Ne Target speed No. Actual speed S Step

Claims (8)

An engine load control device for a work vehicle in which the output of an engine whose rotation speed is controlled by a rotation speed instruction device is transmitted to drive wheels and is also transmitted to a plurality of hydraulic actuators via a plurality of variable displacement hydraulic pumps. And
A target rotational speed detection unit that receives an instruction content from the rotational speed instruction device and detects a target rotational speed of the engine;
An actual engine speed detector for detecting the actual engine speed;
A deviation amount calculation unit for calculating a difference between a detection result in the target rotation number detection unit and a detection result in the actual rotation number detection unit;
A storage unit storing a map that defines a relationship between a deviation amount between the target rotational speed of the engine and the actual rotational speed and a maximum absorption torque of the plurality of variable displacement hydraulic pumps;
Based on the detection result in the actual rotational speed detection unit and the calculation result in the deviation amount calculation unit, referring to the map stored in the storage unit, the maximum absorption torque for the plurality of variable displacement hydraulic pumps A control unit that performs control to reduce the total absorption torque of the plurality of variable displacement hydraulic pumps;
An engine load control device for a work vehicle. An engine load control device for a work vehicle in which the output of an engine whose rotation speed is controlled by a rotation speed instruction device is transmitted to drive wheels and is also transmitted to a plurality of hydraulic actuators via a plurality of variable displacement hydraulic pumps. And
A target rotational speed detection unit that receives an instruction content from the rotational speed instruction device and detects a target rotational speed of the engine;
An actual engine speed detector for detecting the actual engine speed;
A deviation amount calculation unit for calculating a difference between a detection result in the target rotation number detection unit and a detection result in the actual rotation number detection unit;
A map defining the relationship between the deviation between the target rotational speed of the engine and the actual rotational speed, the actual rotational speed of the engine, and the maximum absorption torque of the plurality of variable displacement hydraulic pumps is stored. A storage unit;
A control unit that determines distribution of absorption torque to the plurality of variable displacement hydraulic pumps with reference to the map according to a detection result in the actual rotational speed detection unit;
The engine load control device for a work vehicle according to claim 1. In the map, the distribution ratio of the maximum absorption torque is set for each of the plurality of variable displacement hydraulic pumps according to the importance of the plurality of variable displacement hydraulic pumps.
The engine load control device for a work vehicle according to claim 1 or 2. In the map, an upper limit of the total value of the maximum absorption torque is set for each of the plurality of variable displacement hydraulic pumps according to a deviation between the target rotational speed of the engine and the actual rotational speed.
The engine load control device for a work vehicle according to claim 1 or 2. In the map, an upper limit of the total value of the maximum absorption torque is set for each of the plurality of variable displacement hydraulic pumps according to the actual rotational speed of the engine.
The engine load control device for a work vehicle according to claim 2. The plurality of variable displacement hydraulic pumps include at least one of a steering hydraulic pump, a fan hydraulic pump, and a loader hydraulic pump.
The engine load control device for a work vehicle according to any one of claims 1 to 5. The control unit controls an EPC current for controlling a discharge amount in the variable displacement hydraulic pump to perform a control to reduce a maximum absorption torque of the variable displacement hydraulic pump;
The engine load control device for a work vehicle according to any one of claims 1 to 6. The rotation speed instruction device is an accelerator pedal that adjusts the rotation speed of the engine.
The engine load control device for a work vehicle according to any one of claims 1 to 7.

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