JP6446909B2 - Load measuring device for work equipment - Google Patents

Description

  The present invention relates to a load measuring device for a working machine. More specifically, for example, the present invention relates to a load measuring device that is provided in a crane and measures the weight of a suspended load.

  Patent Document 1 discloses a crane load measuring device using a pressure gauge. The crane hydraulic circuit is provided with a hydraulic pump driven by an engine and a hydraulic motor for operating the winch, which are connected via a control valve for controlling the direction and flow rate of the hydraulic oil. A pressure gauge is connected to the hydraulic line on the winch winding side among the hydraulic lines connecting the control valve and the hydraulic motor, and the winch hoisting operating pressure is measured by the pressure gauge. An analog pressure gauge such as a Bourdon tube pressure gauge is used as the pressure gauge, and the scale for displaying the pressure value is replaced with a scale for a load value proportional to the winch hoisting operating pressure. This allows the pressure gauge to function as a load cell.

JP 09-278379 A

  The proportional relationship between the winch hoisting operating pressure and the load is established under a specific hydraulic oil flow rate. The engine speed at idling and the reduction ratio of the PTO (power take-off) device differ depending on the vehicle, and there are individual differences in the hydraulic pumps and control valves constituting the hydraulic circuit. When the engine is idling, the flow rate of hydraulic oil supplied to the hydraulic motor varies depending on the vehicle. For this reason, it is necessary to set the engine speed to a higher state than the idling state to a specific hydraulic oil flow rate regardless of the vehicle.

Therefore, in the load measuring apparatus as described above, the following operation is necessary for each load measurement.
(1) Zero point adjustment First, a winch hoisting operation is performed in a no-load state, that is, a state in which a hook is not suspended. At this time, the spool opening degree of the control valve is fully opened by operating the operation lever of the control valve to the full side. Next, the rotational speed of the hydraulic pump is adjusted by adjusting the engine rotational speed with the accelerator so that the pointer of the pressure gauge indicates 0 on the scale. In this way, the flow rate of the hydraulic oil supplied to the hydraulic motor is adjusted to a specific flow rate by fully opening the spool opening of the control valve and setting the rotation speed of the hydraulic pump to a specific rotation speed. .
(2) Load measurement Next, a hanging load is applied to the hook and the winch is wound up. Also at this time, the control valve is fully opened by operating the operation lever of the control valve to the full winding side. Then, observe the pressure gauge while winding the winch and read the load value indicated by the pointer.

  Thus, the conventional load measuring device has a problem that the operation procedure is complicated, for example, it is necessary to adjust the zero point every time the load is measured. In addition, there is a problem that there are many points to be noted such as the need to operate the operating lever all the way to the winding side, or the observation of the pressure gauge while the winch is being wound, which is inconvenient.

  In view of the above circumstances, an object of the present invention is to provide a load measuring device for a work machine that is easy to operate and highly convenient.

A load measuring device for a work machine according to a first aspect of the present invention is a lifting machine for lifting a load, a hydraulic actuator for driving the lifting machine, a hydraulic circuit for supplying hydraulic oil to the hydraulic actuator, and measuring a driving pressure of the hydraulic actuator comprising a pressure sensor that includes a control device, wherein the control device, in a load measurement for measuring the weight of the load, initial adjustment of the flow rate of the hydraulic fluid supplied to the hydraulic actuator by controlling the hydraulic circuit The output of the pressure sensor when the lifting machine is operated is converted into a load value.
According to a second aspect of the load measuring apparatus for a work machine according to the first aspect, the hydraulic circuit includes a hydraulic pump driven by an engine, and a flow rate provided in a hydraulic line connecting the hydraulic pump and the hydraulic actuator. A control valve, and the control device sets the rotation speed of the engine to a predetermined rotation speed, and sets the spool opening degree of the flow rate control valve to a predetermined opening degree. characterized by the flow rate and the predetermined flow rate.
According to a third aspect of the present invention, there is provided a load measuring apparatus for a work machine according to the first or second aspect of the present invention, comprising a remote operation terminal capable of communicating with the control device and having a display unit, wherein the control device receives a load from the remote operation terminal. when receiving the measurement instruction, the flow rate of the hydraulic fluid supplied to the hydraulic actuator by controlling the hydraulic circuit and the predetermined flow rate, the output of the pressure sensor at the time of operating the said crane to load value The load value is converted and transmitted to the remote operation terminal, and the remote operation terminal displays the load value received from the control device on the display unit.
The load measuring device for a work machine according to a fourth aspect of the present invention is the first, second or third aspect, wherein the hydraulic actuator is a variable displacement type hydraulic motor, and the control means corresponds to the capacity of the hydraulic motor. The output of the pressure sensor when the lifting machine is operated is converted into a load value by using the gain of the pressure sensor.
According to a fifth aspect of the load measuring apparatus for a work machine according to the first, second, or third invention, the hydraulic actuator is a variable displacement hydraulic motor, and the control means controls the hydraulic circuit to control the hydraulic pressure. the flow rate of the hydraulic fluid supplied to the motor with a predetermined flow rate, wherein the capacity of the hydraulic motor to a predetermined volume, and converts the output of the pressure sensor at the time of operating the said crane to load value And
The load measuring device for a work machine according to a sixth aspect of the present invention is the first, second, third, fourth, or fifth aspect, wherein the control device is configured such that the rate of change of the output of the pressure sensor is equal to or less than a threshold value. The operation of the hydraulic actuator is stopped.

According to the first invention, since the control device automatically sets the flow rate of the hydraulic oil supplied to the hydraulic actuator to a predetermined flow rate, the zero point adjustment and the flow rate adjustment operation are unnecessary, and the convenience is high.
According to the second invention, the control device controls the engine and the flow rate control valve, whereby the flow rate of the hydraulic oil supplied to the hydraulic actuator can be set to a predetermined flow rate.
According to the third aspect of the invention, the load can be measured by operating the remote control terminal, so that the operation is simple. Further, since the load value is displayed on the remote operation terminal, it is easy to check the load value.
According to the fourth aspect of the invention, since the output of the pressure sensor is converted into a load value using the gain of the pressure sensor corresponding to the capacity of the hydraulic motor, an appropriate load value can be obtained regardless of the setting of the hydraulic motor. .
According to the fifth aspect, since the capacity of the hydraulic motor is automatically set to a predetermined capacity, an appropriate load value can be obtained even with a variable capacity type hydraulic motor.
According to the sixth aspect of the invention, the lifting machine is automatically stopped when the load measurement is completed, so that it is safe.

It is a flowchart of the load measurement process by a remote control terminal and a control apparatus. It is a side view of a load-type truck crane. It is a hydraulic circuit diagram of a small crane.

Next, an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
(Loading truck crane)
The load measuring device according to the first embodiment of the present invention is provided in a load-type truck crane CR. First, the configuration of the loadable truck crane CR will be described.
As shown in FIG. 2, the load-type truck crane CR is configured by mounting a small crane 20 on a vehicle frame 13 between a cab 11 and a loading platform 12 of a general-purpose truck 10.

  The small crane 20 includes a base 21 fixed on the vehicle frame 13, a post 22 provided so as to be rotatable with respect to the base 21, and a boom 23 provided on an upper end portion of the post 22 so as to be raised and lowered. Yes. The post 22 has a winch built therein. A wire rope is guided from the winch to the tip of the boom 23 and hung around the hook 24 via a pulley at the tip of the boom 23, whereby the hook 24 is connected to the tip of the boom 23. Hanging from the part. A crane device is constituted by the post 22, the boom 23, the hook 24, and the like. The small crane 20 includes outrigger devices 25 and 26 provided on both the left and right sides of the base 21. Hereinafter, the crane device (post 22, boom 23, hook 24) and outrigger devices 25, 26 are collectively referred to as “working device”.

  These working devices are hydraulically driven by a hydraulic circuit described later. A lever group 27 for operating the hydraulic circuit is provided on both the left and right sides of the base 21. A control device 28 for electrically controlling the hydraulic circuit is provided near the lever group 27.

  A winch that winds up and lowers the hook 24 corresponds to the “lifter” described in the claims. A suspended load can be lifted by hanging a load on the hook 24 and rotating the winch to the winding side. Moreover, the suspended load can be unloaded by rotating the winch to the lowering side.

(Hydraulic circuit)
As shown in FIG. 3, the hydraulic circuit 30 of the small crane 20 mainly includes a hydraulic valve unit 31, a hydraulic pump 33 that supplies hydraulic oil in a tank 32 to the hydraulic valve unit 31, a hydraulic pump 33, and a hydraulic valve. A main oil passage 34 connecting the unit 31, a return oil passage 35 connecting the hydraulic valve unit 31 and the tank 32, and a plurality of hydraulic actuators 41 to 46 connected to the hydraulic valve unit 31. .

  The hydraulic pump 33 is connected to the engine 14 of the general-purpose truck 10 via a PTO (power take-off) device, and is driven by the engine 14.

  The hydraulic actuators 41 to 46 connected to the hydraulic valve unit 31 include a boom expansion / contraction hydraulic cylinder 41, a winch hydraulic motor 42, a boom raising / lowering hydraulic cylinder 43, a turning hydraulic motor 44, and outrigger hydraulic cylinders 45 and 46. is there. The boom 23 is expanded and contracted by the operation of the boom expansion / contraction hydraulic cylinder 41, the hook 24 is wound up and down by the operation of the winch hydraulic motor 42, and the boom 23 is raised and lowered by the operation of the boom raising / lowering hydraulic cylinder 43, and the swing hydraulic pressure The post 22 is turned by the operation of the motor 44, and the outrigger devices 25, 26 are expanded and contracted by the operation of the outrigger hydraulic cylinders 45, 46.

  The hydraulic valve unit 31 is provided with an expansion / contraction switching control valve 51, a winch switching control valve 52, a hoisting switching control valve 53, a turning switching control valve 54, and outrigger switching control valves 55, 56. The boom expansion / contraction hydraulic cylinder 41 is used as the expansion / contraction switching control valve 51, the winch hydraulic motor 42 is used as the winching switching control valve 52, the boom raising / lowering hydraulic cylinder 43 is used as the raising / lowering switching control valve 53, and the turning switching control valve 54. The hydraulic motor 44 for turning is connected to the switching control valves 55, 56 for the outrigger, respectively, and the hydraulic cylinders 45, 46 for the outrigger are respectively connected to control the direction and flow rate of the hydraulic oil supplied from the hydraulic pump 33, The operations of these hydraulic actuators 41 to 46 can be switched and controlled.

  A lever is attached to each of the switching control valves 51 to 56, and the direction and flow rate of hydraulic oil supplied from the hydraulic pump 33 can be switched by manually operating the lever. The levers attached to the switching control valves 51 to 56 are provided on the left and right sides of the base 21 as the lever group 27 (see FIG. 2). Therefore, the working device can be operated by the user U operating the lever group 27.

  Further, pilot cylinders 61 to 66 are attached to the switching control valves 51 to 56, respectively, and the direction and flow rate of the hydraulic oil supplied from the hydraulic pump 33 are also switched by the operation of the pilot cylinders 61 to 66. Can be done.

  Each of the pilot cylinders 61 to 66 is a double-acting cylinder, and is provided with an electromagnetic valve for supplying and discharging hydraulic oil to and from the right oil chamber and an electromagnetic valve for supplying and discharging hydraulic oil to and from the left oil chamber. Yes. These solenoid valves are connected to the control device 28. The control device 28 is a computer composed of a CPU, a memory, and the like, and is provided near the lever group 27 (see FIG. 2). The solenoid valve is operated based on a control signal from the control device 28, so that the pilot cylinders 61 to 66 are driven and the switching control valves 51 to 56 are switched. In this way, the control device 28 controls the operation of the work device. Further, the control device 28 is equipped with various operation units such as switches and levers and a display unit such as a 7-segment display and a liquid crystal panel.

  Of the two hydraulic pipes connected to the winch hydraulic motor 42, a pressure sensor 36 is provided in the hydraulic pipe that supplies hydraulic oil when the winch hydraulic motor 42 is rotated to the winding side. ing. The pressure sensor 36 can measure the driving pressure when the winch is wound up by the winch hydraulic motor 42. Here, “driving pressure” means the pressure of hydraulic oil supplied to the input port of the hydraulic actuator.

  As the pressure sensor 36, for example, a piezoelectric element or the like that can output the detection result as an electric signal is used. The output of the pressure sensor 36 is input to the control device 28.

  The control device 28 is also connected to an ECU (engine control unit) of the engine 14 and is configured to control at least the rotational speed of the engine 14.

  The winch hydraulic motor 42 for driving the winch corresponds to a “hydraulic actuator” recited in the claims. The winch switching control valve 52 that controls the direction and flow rate of the hydraulic oil supplied from the hydraulic pump 33 and guides it to the winch hydraulic motor 42 corresponds to the “flow control valve” recited in the claims.

(Remote operation terminal)
The control device 28 is capable of wireless communication or wired communication with the remote operation terminal 29 in both directions. The remote operation terminal 29 includes a wired operation terminal as well as a wireless operation terminal including a so-called radio-controlled transmitter. The remote operation terminal 29 is equipped with an operation unit including various switches and an accelerator trigger, and a display unit 29a such as a liquid crystal panel.

  The remote operation terminal 29 has a plurality of operation modes in order to improve operability in a limited operation unit, and the function of the operation unit and the display of the display unit 29a are switched according to each operation mode. For example, a crane operation mode for operating the crane device (post 22, boom 23, hook 24), an outrigger operation mode for operating the outrigger devices 25 and 26, and the like are provided. The operation mode is switched by pressing a specific switch, for example.

(Load measuring device)
The load measuring device according to this embodiment mainly includes the remote operation terminal 29, the control device 28, and the pressure sensor 36. By cooperating with each other, the weight (load) of the suspended load can be measured.

(Load measurement method)
Next, a load measuring method using a load measuring device will be described with reference to FIG.
First, the worker hangs a load to be measured on the hook 24.
Next, the worker presses a specific switch of the remote operation terminal 29. Then, the remote operation terminal 29 is switched to the load measurement mode, and the function of the operation unit and the display of the display unit 29a are switched. Then, the remote operation terminal 29 transmits a load measurement preparation signal to the control device 28 (step SA1). When the control device 28 receives the load measurement preparation signal from the remote operation terminal 29, the control device 28 transmits a control signal to the ECU of the engine 14 to set the rotational speed of the engine 14 to a predetermined rotational speed (step SB1).

  Here, the predetermined rotational speed of the engine 14 is a predetermined value and is stored in the control device 28. The predetermined number of revolutions may be set arbitrarily, for example, set as ½ of the maximum number of revolutions of the engine 14. By setting the rotational speed of the engine 14 to a predetermined rotational speed, the rotational speed of the hydraulic pump 33 can also be set to the predetermined rotational speed.

  Next, the worker pulls the accelerator trigger of the remote operation terminal 29. Then, the remote operation terminal 29 transmits a load measurement start signal to the control device 28 (step SA2). When the control device 28 receives the load measurement start signal from the remote operation terminal 29, the control device 28 switches the winch switching control valve 52 so that the winch hydraulic motor 42 rotates to the winding side, and the spool opening degree is set to a predetermined opening degree. (Step SB2).

  Here, the predetermined opening degree of the spool of the winch switching control valve 52 is a predetermined value and is stored in the control device 28. The predetermined opening may be set arbitrarily, for example, fully open. As described above, the rotational speed of the engine 14 (the rotational speed of the hydraulic pump 33) is set to a predetermined rotational speed, and the spool opening degree of the winch switching control valve 52 is set to a predetermined opening degree, thereby supplying the winch hydraulic motor 42. The flow rate of the operating oil is set to a predetermined flow rate. The load measurement preparation signal and the load measurement start signal correspond to the “load measurement instruction” described in the claims.

  When the winch switching control valve 52 is switched, the winch hydraulic motor 42 rotates to the winding side, and the suspended load is lifted. When the suspended load is separated from the ground (ground cutting), the control device 28 reads the output of the pressure sensor 36 and converts it into a load value (step SB3).

  Here, the conversion from the output of the pressure sensor 36 to the load value is performed using the zero point of the pressure sensor 36 and the gain. The zero point of the pressure sensor 36 is an output of the pressure sensor 36 when the winch hoisting operation is performed in a no-load state, that is, a state where no load is applied to the hook 24. When the pressure sensor 36 is a piezoelectric element, it is the output voltage of the piezoelectric element when there is no load. The gain of the pressure sensor 36 is a ratio between the load and the output of the pressure sensor 36. When the pressure sensor 36 is a piezoelectric element, it is the ratio between the load and the output voltage of the piezoelectric element. The zero point and gain of these pressure sensors 36 are obtained by initial adjustment described later, and are stored in the control device 28. The load value can be obtained by subtracting the zero point from the output of the pressure sensor 36 and multiplying by the gain.

  The control device 28 transmits the obtained load value to the remote operation terminal 29 (step SB4). The remote operation terminal 29 displays the load value received from the control device 28 on the display unit 29a (step SA3). The operator can confirm the load by looking at the display unit 29 a of the remote operation terminal 29.

  The load value may be displayed on the display unit 29a of the remote operation terminal 29 while the worker is pulling the accelerator trigger. In this case, when the worker returns the accelerator trigger, the remote operation terminal 29 is automatically switched to the crane operation mode, and the load value display is turned off. Then, the worker can continue normal crane work.

  Even when the worker returns the accelerator trigger, the load value may be displayed on the display unit 29a. Then, it is safe because the winch hoisting operation is performed while observing the state of the suspended load, and the load can be confirmed after the operation is stopped. In this case, when a specific switch of the remote operation terminal 29 is pressed, the operation mode can be switched to the crane operation mode or the like.

  Further, while the operator is pulling the accelerator trigger of the remote control terminal 29, the winch hydraulic motor 42 may be driven to continue lifting the suspended load, or the winch is detected by detecting that the suspended load has been cut off. The driving of the hydraulic motor 42 may be automatically stopped.

  When the suspended load is lifted, the load applied to the hook 24 is initially only the weight of the hook, and the load gradually increases when a part of the suspended load leaves the ground, and the load is constant after the ground is completely grounded. It becomes. Along with this, the output of the pressure sensor 36 (drive pressure at the time of winding the winch) is initially constant (the load on the hook), and after gradually increasing, becomes constant again (the load on the hook and the suspended load). After the suspended load is grounded, the time change rate of the output of the pressure sensor 36 becomes small. Therefore, the time change rate of the output of the pressure sensor 36 may be obtained, and it may be determined that the suspended load has grounded when the time change rate is equal to or less than the threshold.

  The control device 28 determines whether the suspended load is grounded by the above-described method, and when the suspended load is grounded, the control device 28 switches the winch switching control valve 52 to stop the operation of the winch hydraulic motor 42. With such a configuration, the winch automatically stops when the load measurement is completed, so that the suspended load is not lifted more than necessary and is safe.

  As described above, according to the load measuring device of the present embodiment, the control device 28 automatically sets the flow rate of the hydraulic oil supplied to the winch hydraulic motor 42 to a predetermined flow rate. And the operation of adjusting the flow rate is unnecessary, and it is highly convenient.

  Further, it is not necessary to operate the winch switching control valve 52 with a lever, and the load can be measured by operating the remote operation terminal 29, so that the operation is simple. Since the load value is displayed on the remote operation terminal 29, the operator can easily confirm the load value. In addition, since the worker can operate at any place with the remote operation terminal 29, it is easy to check the safety of the work.

(Initial adjustment method)
Next, an initial adjustment method of the load measuring device will be described.
The zero point and gain of the pressure sensor 36 can be determined by the initial adjustment. This initial adjustment is basically performed once at the beginning, and need not be performed every time the load is measured.

In the initial adjustment, the basic flow is the same as the load measurement.
That is, by operating the remote operation terminal 29, the control device 28 sets the rotation speed of the engine 14 to a predetermined rotation speed and sets the spool opening degree of the winch switching control valve 52 to a predetermined opening degree. At this time, the predetermined rotational speed of the engine 14 and the predetermined opening degree of the spool of the winch switching control valve 52 are the same as in the case of load measurement. That is, the flow rate of the hydraulic oil supplied to the winch hydraulic motor 42 is the same in the initial adjustment and the load measurement .

  In this state, the lifting operation of the suspended load is performed at least twice while changing the weight of the suspended load, and the output of the pressure sensor 36 in each case is acquired. For example, the first time is an unloaded state, and the second time is a lifting of a known weight, and the output of the pressure sensor 36 in each case is acquired. Then, the zero point and gain of the pressure sensor 36 can be determined from the relationship between the weight of the suspended load for two times and the output of the pressure sensor 36.

[Second Embodiment]
The load measuring apparatus according to the second embodiment of the present invention is a form in which a variable displacement hydraulic motor is used as the winch hydraulic motor 42. By using a variable displacement type hydraulic motor as the winch hydraulic motor 42, there are two types, a high speed low torque mode in which the capacity of the winch hydraulic motor 42 is increased and a low speed high torque mode in which the capacity of the winch hydraulic motor 42 is decreased. A winch having a mode can be realized.

  Since the output torque with respect to the drive pressure of the winch hydraulic motor 42 differs in these two modes, it is necessary to determine the zero point and gain of the pressure sensor 36 for each mode. For this, the initial adjustment in the first embodiment may be performed in each of the two modes. The control device 28 stores the zero point and gain of the pressure sensor 36 for each mode.

  The load measurement of this embodiment is basically the same as the load measurement of the first embodiment. However, in step SB3 in which the output of the pressure sensor 36 is converted into a load value, the output of the pressure sensor 36 is obtained using the winch mode, that is, the zero point and gain of the pressure sensor 36 corresponding to the capacity of the winch hydraulic motor 42. Is converted into a load value. In this way, an appropriate load value can be obtained regardless of the setting of the winch hydraulic motor 42.

  Instead of the method for determining the zero point and gain of the pressure sensor 36 for each winch mode as described above, a method for switching the winch mode to a specific mode in load measurement may be used. For example, in the load measurement, the winch may be always set to the low speed and high torque mode. In the load measurement, the winch may be operated at a low speed, and the low speed is rather safe.

  In this case, the zero point and gain of the pressure sensor 36 may be determined only in the low speed and high torque mode. In the load measurement, in step SB1, the rotational speed of the engine 14 is set to a predetermined rotational speed, and the winch is switched to the low speed high torque mode, that is, the capacity of the winch hydraulic motor 42 is set to a predetermined capacity. Thus, by automatically setting the capacity of the winch hydraulic motor 42 to a predetermined capacity, an appropriate load value can be obtained even with a variable displacement hydraulic motor.

  Although the case where the winch has two modes has been described above, the same applies when the winch has three or more modes, that is, when the capacity of the winch hydraulic motor 42 is controlled in three or more stages. Further, the same applies to the case where the capacity of the winch hydraulic motor 42 is controlled without any steps.

[Other Embodiments]
In the above embodiment, in order to set the flow rate of the hydraulic oil supplied to the winch hydraulic motor 42 to a predetermined flow rate, the rotation speed of the engine 14 is set to a predetermined rotation speed, and the spool opening degree of the winch switching control valve 52 is set to a predetermined value. The predetermined opening was used. However, other controls may be adopted as long as the configuration of the hydraulic circuit changes. For example, when a variable discharge amount type hydraulic pump is used as the hydraulic pump 33, the discharge capacity of the hydraulic pump 33 needs to be a predetermined capacity.

  In the above embodiment, the remote operation terminal 29 is used. However, a configuration in which this is not used may be used. In this case, the operation unit of the control device 28 may be used instead of the operation unit of the remote operation terminal 29, and the display unit of the control device 28 may be used instead of the display unit 29a of the remote operation terminal 29.

  Furthermore, although the loading type truck crane CR has been described as the working machine provided with the load measuring device in the above-described embodiment, other working machines may be used. As a work machine, what is necessary is just a work machine provided with the lifting machine which lifts a load besides a crane. The crane may be a mobile crane or a fixed crane. Examples of the mobile crane include an all terrain crane, a rough terrain crane, a truck crane, and a loading truck crane. The lifting machine is not limited to a winch of a crane, and may be any device that can lift a load.

CR load type truck crane 10 general purpose truck 20 small crane 28 control device 29 remote control terminal 30 hydraulic circuit 31 hydraulic valve unit 33 hydraulic pump 36 pressure sensor 41-46 hydraulic actuator 51-56 switching control valve 61-66 pilot cylinder

Claims (6)

A hoist to lift the load,
A hydraulic actuator for driving the lifting machine;
A hydraulic circuit for supplying hydraulic oil to the hydraulic actuator;
A pressure sensor for measuring a driving pressure of the hydraulic actuator;
A control device,
In the load measurement for measuring the weight of the load , the control device ,
The flow rate of hydraulic oil supplied to the hydraulic actuator by controlling the hydraulic circuit is set to a predetermined flow rate that is the same as the flow rate in the initial adjustment ,
A load measuring device for a working machine, wherein an output of the pressure sensor when the lifting machine is operated is converted into a load value. The hydraulic circuit is
A hydraulic pump driven by an engine;
A flow rate control valve provided in a hydraulic line connecting the hydraulic pump and the hydraulic actuator,
Wherein the control device, the rotational speed of the engine and a predetermined rotational speed, the spool opening degree of the flow control valve by a predetermined opening, the flow rate of the hydraulic fluid supplied to the hydraulic actuator and the predetermined flow rate The load measuring device for a working machine according to claim 1, wherein A remote control terminal capable of communicating with the control device and having a display;
The control device includes:
When a load measurement instruction is received from the remote control terminal,
The flow rate of the hydraulic fluid supplied to the hydraulic actuator by controlling the hydraulic circuit and the predetermined flow rate,
Convert the output of the pressure sensor when operating the lifting machine into a load value,
Sending the load value to the remote control terminal;
The load measuring device for a working machine according to claim 1 or 2, wherein the remote operation terminal displays the load value received from the control device on the display unit. The hydraulic actuator is a variable displacement hydraulic motor,
The control means includes
The output of the said pressure sensor at the time of operating the said lifting machine is converted into a load value using the gain of the said pressure sensor corresponding to the capacity | capacitance of the said hydraulic motor, The claim 1, 2, or 3 characterized by the above-mentioned. Load measuring device for working machines. The hydraulic actuator is a variable displacement hydraulic motor,
The control means includes
With the flow rate of the predetermined flow rate of hydraulic fluid supplied to the hydraulic motor by controlling the hydraulic circuit, the capacity of the hydraulic motor to a predetermined volume,
The load measuring device for a work machine according to claim 1, 2, or 3, wherein an output of the pressure sensor when the lifting machine is operated is converted into a load value. The control device includes:
The load measuring device for a working machine according to claim 1, 2, 3, 4, or 5, wherein the operation of the hydraulic actuator is stopped when a change rate of an output of the pressure sensor becomes a threshold value or less.