JP2011002085A - Hydraulic control device for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device for a construction machine, suppressing electric energy to be used to achieve the extension of a battery life while suppressing cost and a space occupied by an apparatus and maintaining a simple structure.SOLUTION: The construction machine includes travel motors 7L, 7R, a boom cylinder 15a, an arm cylinder 16a, a bucket cylinder 17a and a swing cylinder 18a, and is driven by these hydraulic actuators. In the construction machine, the hydraulic control device includes: variable displacement hydraulic pumps P1, P2 delivering hydraulic fluid for operating the hydraulic actuators; a displacement cylinder 37 changing the maximum displacement of the hydraulic pumps P1, P2; an electric motor M driving the hydraulic pumps P1, P2; the battery 60 supplying electric power to drive the electric motor M; and a controller 50 detecting the battery residual capacity of the battery 60, and performing control for reducing the maximum displacement of the hydraulic pumps P1, P2 by operating the displacement cylinder 37 according to a reduction in the battery residual capacity.

Description

  The present invention relates to a construction machine configured to operate an actuator using hydraulic pressure, and further relates to a hydraulic control device for a construction machine driven by an electric motor.

  As an electric construction machine having a configuration in which a hydraulic pump is operated by an electric motor and a hydraulic actuator is operated using hydraulic oil supplied from the hydraulic pump, for example, there is a power shovel vehicle. Examples of hydraulic actuators include hydraulic motors and hydraulic cylinders. By operating these hydraulic actuators, cylinders such as traveling devices, swiveling devices, booms, arms, and buckets are operated to perform various operations such as traveling and excavation. . In addition to running and excavating work, a power shovel vehicle can also perform work such as turning the vehicle and moving earth and sand.

  In a construction machine such as the above-described power shovel, the hydraulic actuator can usually be operated at a speed corresponding to the operation amount of the operation device (for example, an operation lever). In other words, the operating speed of the hydraulic actuator can be made variable. This is a control valve that controls the supply of hydraulic pressure to the hydraulic actuator and a pilot pressure drive type, and operates by adjusting the magnitude of the supplied pilot pressure. This is made possible by continuously changing the oil flow rate. As the control valve, for example, there is a type that continuously changes the flow rate of hydraulic oil to the control valve by changing a current supplied as a proportional solenoid valve, and a mechanical lever type.

  In the construction machine as described above, reduction of the amount of electric power used by an electric motor such as an electric motor and the extension of the battery life are problems. Therefore, in order to solve this problem, when the plurality of electric motors and the plurality of inverters, the battery, and the remaining power amount of the battery (hereinafter referred to as battery remaining amount) are reduced to a predetermined value or less, the plurality of electric motors Power control means for controlling to reduce the total power consumption by outputting a signal so as to reduce the amount of output power to one of the motors, and the power control means detects the remaining battery level and reduces the remaining battery level Accordingly, construction machines that reduce the amount of power used are well known (see, for example, Patent Document 1). In such a construction machine, the operating speed of the hydraulic actuator decreases with the output of the signal, so that the amount of power used can be reduced and the operator can recognize the decrease in the remaining battery level. .

JP 2008-63902 A

  However, although the construction machine as described above can reduce the amount of electric power used, there is a problem that a plurality of inverters are required and the cost is increased. In addition, since the number of devices increases, it is necessary to secure a new space for installing the devices. For example, the space occupied by the devices increases and the structure becomes complicated. Further, for example, as shown in FIG. 7A, when the load suddenly rises, the pump pressure rises and a large current flows from the battery. At this time, the voltage of the battery may drop suddenly. At this time, when the voltage reaches a set value even for a short time, there is a problem that a voltage drop error is output despite the remaining amount of the battery, and the construction machine stops.

  The present invention has been made in view of the above-described problems, and is a construction machine capable of reducing the amount of electric power used and realizing a long battery life while reducing the cost and space occupied by the equipment and maintaining a simple configuration. An object of the present invention is to provide a hydraulic control device.

  In order to solve the above problems, a hydraulic control device for a construction machine according to the present invention includes a hydraulically operated hydraulic actuator (for example, travel motors 7L and 7R, boom cylinder 15a, arm cylinder 16a, bucket cylinder 17a, swing in the embodiment) In a construction machine that includes a cylinder 18a) and is driven by a hydraulic actuator, a variable displacement hydraulic pump that discharges hydraulic fluid for operating the hydraulic actuator, and a capacity changing unit that changes the maximum capacity of the hydraulic pump (for example, In the embodiment, the capacity cylinder 37), an electric motor that drives the hydraulic pump, a battery that supplies electric power to drive the electric motor to the electric motor, and the remaining battery level of the battery are detected to reduce the remaining battery level. At the same time, operate the capacity changing means to increase the maximum capacity of the hydraulic pump. Characterized by comprising a controller for controlling small is allowed.

  In addition, it is preferable to provide a changeover switch (for example, an energy saving mode changeover switch 19a in the embodiment) that can switch whether or not to perform control for reducing the maximum capacity of the hydraulic pump by the controller.

  As described above, in the hydraulic control apparatus for a construction machine according to the present invention, the hydraulic pump is a variable displacement type, and the controller detects the remaining battery level and detects the detected remaining battery level. By performing control to reduce the maximum capacity, it is possible to reduce the amount of electric power used and extend the life of the battery while maintaining a simple configuration while suppressing cost and space occupied by the device. Furthermore, since the hydraulic pump is of a variable displacement type, even when the load suddenly increases, the self-pressure is fed back and the absorption torque of the hydraulic pump does not increase. As shown in FIG. A large amount of current will not flow. Therefore, it is possible to prevent the above-described sudden voltage drop, voltage drop error output, and stoppage of the construction machine.

  Also, by providing the controller with a selector switch that can select whether the maximum capacity of the hydraulic pump is to be decreased or not, the controller can be configured to increase the maximum capacity when the work needs to be performed quickly. It is also possible not to decrease it.

It is a side view of a power shovel vehicle shown as an example of a construction machine to which a hydraulic control device according to the present invention is applied. 1 is a hydraulic circuit showing a hydraulic control device according to the present invention. It is a graph showing a P-Q characteristic of the hydraulic pump before and after reducing the maximum capacity of the hydraulic pump in the hydraulic control device. FIG. 4 is a diagram showing the relationship between the hydraulic pressure and the current output from the battery, and the hydraulic pressure and the rotation speed of the electric motor in the hydraulic control device, wherein (a) shows the relationship between the hydraulic pressure and the current in the normal mode or the energy saving mode. The graph which shows a relationship, (b) is a graph which shows the relationship between a hydraulic pressure and the rotation speed of an electric motor. It is a graph which shows the relationship between the capacity | capacitance (discharge capacity) of a hydraulic pump, and a battery remaining charge in the said hydraulic control apparatus. (A) is a figure which shows the modification of a structure around a controller and a capacity | capacitance cylinder in the said hydraulic control apparatus. (B) is a relationship between the discharge capacity and the discharge pressure when the capacity cylinder is not provided with an elastic member in the modification, and (c) is a discharge capacity and a discharge pressure when the capacity cylinder is provided with an elastic member in the modification. It is a graph which shows the relationship. It is the graph shown about the change by the change of the voltage by the change of pump pressure, an electric current, and those, and time. (A) a fixed displacement hydraulic pump, (b) are graphs in the case of using a variable displacement hydraulic pump.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG. A crawler type power shovel 1 (hereinafter referred to as power shovel 1) will be described as an example of the construction machine according to the present invention. The excavator vehicle 1 is an electrically driven construction machine that operates using electric power, and includes a traveling device 2 having a pair of left and right crawler traveling mechanisms, a turning mechanism 3 provided on the upper portion of the traveling device 2, An operation cabin 4 provided on the upper part of the turning mechanism 3 so as to be horizontally turnable, a power shovel mechanism 5 attached to the front part of the operation cabin 4 so as to be horizontally turnable, and swingable up and down at the rear part of the operation cabin 4. It is constituted by a provided blade 6 (a soil discharge board) or the like.

  The traveling device 2 is configured by providing a crawler mechanism including driving wheels 2a, driven wheels 2b, and crawler belts 2c wound around the driving wheels 2a and driven wheels 2b on the left and right sides of the traveling frame 2d. The drive wheel 2a provided on the right side is driven by a right travel motor 7R, and the drive wheel 2a provided on the left side is driven by a left travel motor 7L. Further, a turning mechanism 3 is provided at the center upper portion of the traveling frame 2d, and the turning mechanism 3 tilts a turning operation lever of an operating device 19 described later, thereby driving a driving cabin 4 by a turning motor (not shown). Can be swiveled.

  A vehicle body frame 9 is provided below the driving cabin 4, and a cover member 13 on which a hydraulic control device 10 to be described later is mounted is disposed at the top of the vehicle body frame 9 and at the rear of the driving cabin 4. As shown in FIG. 1, the driving cabin 4 is provided with an operator seat 11 for an operator to board and an operation device 19 for operating various operations of the power shovel 1. The operation of the power shovel 1 can be operated by boarding the operator seat 11 and operating the operation device 19.

  The power shovel mechanism 5 includes a boom 15 that is pivoted horizontally or swingably with respect to a main body pivoting portion 14 that protrudes forward of the vehicle body frame 9, and a tip of the boom 15 within the same vertical plane. The arm 16 is pivotably pivotable up and down, and the bucket 17 is pivotally coupled to the tip of the arm 16 so as to be pivotable vertically within the same vertical plane. A swing-side pivot 18 and a swing cylinder 18a are provided in front of the body frame 9, and the swing-side pivot 18 can be swung by an expansion / contraction operation of the swing cylinder 18a. Also, a boom cylinder 15a that swings the boom 15 up and down is disposed by connecting the swing side pivot 18 and the boom 15, and an arm cylinder 16a that swings the arm 16 up and down connects the boom 15 and the arm 16. A bucket cylinder 17 a and a link 17 b that are arranged in a connected manner and swing the bucket 17 up and down are arranged to connect the arm 16 and the bucket 17. The blade 6 can be swung by the expansion and contraction operation of the blade cylinder 6a.

  By the way, the actuators described above (the left and right traveling motors 7L and 7R, the boom cylinder 15a, the arm cylinder 16a, the bucket cylinder 17a, the swing cylinder 18a, and the blade cylinder 6a) are operated by the supply of hydraulic oil (hydraulic pressure). The hydraulic control device 10 (see FIG. 2) controls the amount and direction of hydraulic oil supplied to each hydraulic actuator in accordance with the operation of the operator's operating device 19, thereby driving and excavating the power shovel vehicle 1. Etc. can be performed.

  As shown in FIG. 2, the hydraulic control device 10 includes first and second control valve groups 20 and 30, first and second hydraulic pumps P <b> 1 and P <b> 2, an electric motor M, an inverter 36, and a capacity cylinder 37. The first and second pressure sensors 38, 39, the hydraulic oil tank 40, the controller 50, the battery 60, and the like. The first control valve group 20 includes a left traveling control valve 21 that controls the amount of hydraulic oil supplied to the left traveling motor 7L, the boom cylinder 15a, and the bucket cylinder 17a, a boom control valve 22, and a bucket control valve. 23. The second control valve group 30 includes a right traveling control valve 31 that controls the amount of hydraulic oil supplied to the right traveling motor 7R, the arm cylinder 16a, and the swing cylinder 18a, an arm control valve 32, and a swing control valve. 33. In addition, the boom control valve 22, the arm control valve 32, and the bucket control valve 23 have a built-in spool, and the spool can be moved by a pilot pressure supplied from a pilot valve (not shown). The amount of hydraulic oil supplied to the boom cylinder 15a, the arm cylinder 16a, and the bucket cylinder 17a can be controlled by the movement of the spool.

  The first and second hydraulic pumps P1 and P2 are provided for running and excavating the power shovel vehicle 1 (operation of the power shovel mechanism 5), and are connected to an output shaft (not shown) of the electric motor M. Each of the hydraulic oils obtained from the hydraulic oil tank 40 as the electric motor M is driven is configured to be discharged. The first and second hydraulic pumps P1 and P2 are so-called swash plate type piston pumps having a swash plate (not shown), and the angle of the swash plate can be changed. By changing the angle, the amount of hydraulic oil to be discharged (discharge capacity) can be changed.

  In the first and second hydraulic pumps P1 and P2 in the present embodiment, the discharge capacity is controlled (feedback) based on the hydraulic pressure of the discharged hydraulic oil (detected values of first and second pressure sensors 38 and 39 described later). Not control). Therefore, as shown in FIG. 3, the discharge capacities of the first and second hydraulic pumps P1 and P2 do not change even if the load torque of the electric motor M increases and the discharge pressure fluctuates. The electric motor M is driven by converting DC power supplied from a battery 60 (to be described later) into AC power having a predetermined voltage and frequency via an inverter 36 and supplying it.

  The first and second pressure sensors 38 and 39 are provided so as to be connected to the oil passages of the hydraulic oil supplied from the first and second hydraulic pumps P1 and P2, respectively. The first pressure sensor 38 is the first hydraulic pump. The second pressure sensor 39 detects the hydraulic pressure of the hydraulic oil discharged from the P1 and the second pressure sensor 39 detects the hydraulic pressure of the hydraulic oil discharged from the second hydraulic pump P2. The hydraulic pressure detected by the first and second pressure sensors 38 and 39, respectively to be outputted to the controller 50.

  The controller 50 can detect the remaining battery level from the value of current supplied from a battery 60 described later, and outputs a capacity change signal to the capacity cylinder 37 in accordance with the detected remaining battery level. Volume cylinder 37, telescopic movement freely configured, so as to stretch the dynamic depending on the volume change signal. This expansion / contraction movement makes it possible to change the angle of the swash plate of the first and second hydraulic pumps P1, P2, and the displacement cylinder 37 changes the angle of the swash plate so that the first and second hydraulic pumps P1. , P2 can be changed in maximum capacity.

  Battery 60 is provided to supply DC power to the inverter 36 and the controller 50, the maximum value of the output current is 30A. The pressure of the hydraulic oil discharged from the first and second hydraulic pumps P1, P2 increases in proportion to the output current. Regarding the relationship between the magnitude of the current supplied from the battery 60 and the pressure (hydraulic pressure) of the hydraulic oil discharged from the first and second hydraulic pumps P1 and P2, and the relationship between the rotation speed of the electric motor M and the hydraulic pressure As shown in FIGS. 4A and 4B, when the load torque of the electric motor M increases, the rotation speed of the electric motor M is maintained at a constant value, so that the hydraulic pressure and the current supplied from the battery 60 also increase. Become. However, when the load torque exceeds a certain value, the current does not increase more than 30 A as an upper limit, and the rotation speed of the electric motor M decreases. The output of the electric motor M is 7 kW.

  The operating device 19 includes a traveling operation lever that operates traveling of the power shovel 1 and a boom operating lever, arm operating lever, bucket operating lever, and the like for operating the boom, arm, bucket, and the like. In addition, the operation device 19 is provided with an energy saving mode switch 19a. The energy saving mode switch 19a can be turned on / off. The energy saving mode is turned on and the normal mode is turned off. Each can be switched to. When the energy saving mode changeover switch 19a is turned on to enter the energy saving mode, the controller 50 performs control to reduce the maximum capacities of the first and second hydraulic pumps P1 and P2 in accordance with a decrease in the remaining battery level of the battery 60. Do. That is, as shown by the arrows and broken lines in FIG. 3, when the maximum capacity of the first and second hydraulic pumps P1, P2 is lowered, the discharge capacity does not exceed the maximum capacity even if the discharge pressure is lowered. It becomes possible to suppress the output power amount of the battery 60. As described above, in the energy saving mode, the battery 60 can be used for a longer period of time by suppressing the amount of power by reducing the maximum capacity. In contrast, in the normal mode, the controller 50 does not decrease the maximum capacities of the first and second hydraulic pumps P1 and P2, and each hydraulic actuator can be operated quickly.

  In the hydraulic control apparatus 10 configured as described above, the energy saving mode is provided as described above, and the controller 50 reduces the maximum capacities of the first and second hydraulic pumps P1 and P2 in accordance with a decrease in the remaining battery level. By controlling in this way, the power consumption of the battery 60 can be suppressed and the operation time can be extended. Further, when the capacity of the first and second hydraulic pumps P1 and P2 is reduced in the energy saving mode, the work speed is reduced, but it is possible not to drop the hydraulic pressure (power). It can be recognized that the amount is decreasing. Specifically, as shown in FIG. 5, the first and second hydraulic pumps P1, P2 are set at a maximum capacity of 4.5 cc / rev when the remaining battery level is 100%. When the hydraulic pumps P1 and P2 are operated, the remaining battery level gradually decreases from 100%. When the controller 50 detects that the remaining battery level has decreased to 50%, the controller 50 outputs a capacity change signal to the capacity cylinder 37, and the capacity cylinder 37 has an angle of the swash plate of the first and second hydraulic pumps P1, P2. To reduce its maximum capacity. At this time, since the speed of each hydraulic actuator is lowered, the operator can recognize that the remaining battery capacity is low. When the remaining battery level becomes 0%, the maximum capacity is reduced to 3.0 cc / rev.

  As described above, the hydraulic control device 10 according to the above-described embodiment can reduce the maximum capacities of the first and second hydraulic pumps P1 and P2 in accordance with a decrease in the remaining amount of the battery. The time can be extended. Further, in the energy saving mode in which the maximum capacities of the first and second hydraulic pumps P1 and P2 are decreased in accordance with the decrease in the remaining battery level, as shown in FIG. 5A, compared with the normal mode in which the maximum capacity is not changed. Thus, the current output from the battery 60 can be reduced.

  In the above-described embodiment, the first and second pressure sensors 38 and 39 detect the hydraulic pressure of the hydraulic oil discharged from the first and second hydraulic pumps P1 and P2, respectively, and the detected value is used as the controller 50. The controller 50 outputs the displacement change signal to the displacement cylinder 37 to change the displacements of the first and second hydraulic pumps P2. However, the configuration of the controller and the displacement cylinder is limited to this. There is no.

  For example, in the hydraulic control apparatus 10 configured as shown in FIG. 2, it is necessary to provide signal changing means (not shown) for changing an electrical signal such as a proportional valve to a hydraulic signal between the controller 50 and the displacement cylinder 37. There is. Therefore, as shown in FIG. 6A by changing such a configuration, the ON-OFF valve 145 communicating with the oil passages of the hydraulic oil discharged from the first and second hydraulic pumps P1 and P2 is provided as described above. It may be provided between the oil passage and the capacity cylinder 137. With such a configuration, the first and second pressure sensors 38 and 39 can be omitted, and the ON-OFF valve 145 and the controller 150 can be less expensive than the proportional valve and the controller 50. The cost of the entire control device can be reduced.

  The capacity cylinder 137 in the configuration shown in FIG. 6A can be attached with an elastic member such as a spring. The relationship between the discharge capacity and the pressure of the first and second hydraulic pumps P1 and P2 is as described above. as shown in FIG. 6 if there is no elastic member (b), when there is the elastic member is as shown in FIG. 6 (c). That is, when there is no elastic member, the capacity is changed based on the self-pressures of the first and second hydraulic pumps P1 and P2, so the discharge capacity in the energy saving mode (see the broken line in FIG. 6B). Is the same as the discharge capacity in the normal mode when the discharge pressure is 0 (see the solid line in FIG. 6B), but the discharge capacity decreases to some extent as the pressure increases from 0. After that, it becomes constant even if the pressure is increased. On the other hand, when there is an elastic member, the discharge capacity in the energy saving mode (see the broken line in FIG. 6C) is the discharge capacity in the normal mode (see FIG. 6 (FIG. 6 (c)). c) (see solid line)), but gradually decreases when the pressure exceeds a predetermined value. The predetermined value can be changed by using an elastic member having a different elastic force as the elastic member of the capacity cylinder 137.

  In this way, if the configuration shown in FIG. 6A is used, the cost can be reduced, and the discharge of the pump can be reduced by attaching / detaching the elastic member to / from the displacement cylinder 137 and changing the elastic force of the elastic member. The relationship between the capacity and the discharge pressure can be changed as shown in FIG. 6B or 6C, for example. Furthermore, it is possible to perform so-called two-stage control in which the discharge capacity is lowered stepwise in accordance with the increase in discharge pressure and the discharge pressure is changed in two stages.

  The present invention is not construed as being limited to the above-described embodiments, and can be appropriately improved without departing from the spirit of the present invention. For example, in the present embodiment, an example in which two hydraulic pumps are provided has been described, but the number of hydraulic pumps is not limited to two, and the present invention can be applied even if one or three or more hydraulic pumps are provided. The output of the electric motor M (7.0 kW), the maximum capacities of the first and second hydraulic pumps P1 and P2 (4.5 cc / rev and 3.0 cc / rev), and the maximum output current (30 A) of the battery 60 are Without being limited to these values, it can be arbitrarily changed.

  Furthermore, in the above-described embodiment, an example in which the crawler-type power shovel vehicle 1 is used as an example of the construction machine has been described. However, the present invention is not limited to this, and other construction machines such as an excavator loader and a hydraulic crane can be used. The present invention may be applied to.

P1, P2 1st and 2nd hydraulic pump (hydraulic pump)
M Electric motor 1 Power shovel (Construction machinery)
10 Hydraulic control device 19a Energy saving mode changeover switch (changeover switch)
37 Capacity cylinder (capacity changing means)
50 controller 60 battery

Claims (2)

In a construction machine comprising a hydraulically operated hydraulic actuator and driven by the hydraulic actuator,
A variable displacement hydraulic pump that discharges hydraulic oil for operating the hydraulic actuator;
Capacity changing means for changing the maximum capacity of the hydraulic pump;
An electric motor for driving the hydraulic pump;
A battery for supplying electric power for driving the electric motor to the electric motor;
A controller for detecting a remaining battery capacity of the battery and performing a control to operate the capacity changing means to reduce the maximum capacity of the hydraulic pump in accordance with a decrease in the remaining battery capacity. Hydraulic control device of the machine.   The hydraulic control device for a construction machine according to claim 1, further comprising a changeover switch capable of switching whether to perform control for reducing the maximum capacity of the hydraulic pump by the controller.

Images