JP2008039063A - Hydraulic control circuit for construction machinery - Google Patents

Abstract

Energy saving is realized by performing relief cut at the time of turning with a simple structure and gradually increasing the flow rate required for the turning motor to turn.
A hydraulic pump, a swing motor that is driven by oil discharged from the hydraulic pump to swing an upper swing body, a swing motor switching valve that controls a rotation direction and a speed of the swing motor, and a hydraulic pressure A regulator 14 that controls the flow rate of the discharged oil by the pump 12, a negative control throttle 18 that generates a negative control pressure in the discharge oil that has passed through the control valve 11, and a negative control circuit 24 that applies the negative control pressure to the regulator, and a hydraulic pressure The pressure sensor 33 that detects the discharge pressure from the pump 12 and the amount of change in the discharge pressure is sensed from the value of the pressure sensor 33. If the amount of change changes suddenly, the flow proportional valve is controlled to adjust the hydraulic pressure to the regulator 14. In addition, a controller 31 that suppresses the discharge flow rate of the hydraulic pump 12 for a predetermined time is provided.
[Selection] Figure 1

Description

  The present invention relates to a hydraulic control circuit for a construction machine such as a hydraulic excavator, and more particularly to a hydraulic control circuit for a construction machine in which the amount of relief at the time of starting a swing motor is reduced to minimize energy loss. Is.

  Construction machines such as hydraulic excavators are generally well known, including Patent Document 1.

  4 and 5 show an example of a hydraulic excavator known from Patent Document 1. FIG. In FIG. 4, an upper swing body 2 is mounted on a crawler-type lower traveling body 1 so as to be rotatable about a vertical axis, and a cab 3 is placed on one front side of the upper swing body 2 so that a front center portion is provided. The boom 4 is attached to the boom cylinder 5 so as to be able to move up and down. An arm 6 is pivotally attached to the tip of the boom 3 by an arm cylinder 7, and a bucket 8 is pivotally attached to the tip of the arm 6 by a bucket cylinder 9. Further, as shown in FIG. 5, a turning motor 10 is provided in the vicinity of the turning center of the upper turning body 2, and a control valve 11 having a turning motor switching valve 11 b is attached to the rear part of the turning motor 10.

  The turning motor 10 is driven by oil discharged from a hydraulic pump (not shown) driven by an engine. On the other hand, the swing motor switching valve 11b is provided between the swing motor 10 and the hydraulic pump, and the rotational direction and speed of the swing motor 10 can be controlled by operating the swing motor switching valve 11b with a swing lever (not shown). It is like that.

  In addition, a hydraulic excavator or the like requires a large force when the swing motor is started. Therefore, when the swing motor is started, generally, the operation amount of the swing lever is maximized from the beginning, and the supply flow rate from the hydraulic pump increases at a constant rate with the elapsed time as shown by the solid line (a) in FIG. It is set to do. In the characteristic diagram shown in FIG. 6, the vertical axis indicates the discharge flow rate Q of the hydraulic pump, and the horizontal axis indicates time t.

  However, even if the flow rate of the hydraulic pump is set to the maximum from the beginning, the inertia of the upper swing body is large, so the swing motor is not driven at a speed commensurate with the flow rate supplied from the hydraulic pump. The rotation speed increases and the rotational speed also increases in proportion to the increase in the flow rate used. Then, after a certain period of time, most of the flow rate supplied from the control valve is used by the swing motor, and the swing motor rotates at a speed corresponding to it.

  Therefore, part of the discharged oil supplied from the hydraulic pump is discharged from the relief valve to the tank until the turning lever is operated and the elapsed time is reached. Discharging the discharged oil from the relief valve clearly results in energy loss, which not only decreases efficiency and increases fuel consumption, but also increases the oil temperature in the tank due to the oil discharged from the relief valve. As a result, the oil deteriorates and there is a problem that the life of the equipment in the hydraulic circuit is shortened.

  Further, generally, in the swing operation of the hydraulic excavator, the discharge flow rate of the hydraulic pump required at the time of starting varies depending on the posture of the working machine including the boom, the arm, the bucket, and various cylinders that drive these. That is, when the working machine is folded small and the turning radius is small, as shown by the dotted line (b) in FIG. 6, the necessary supply flow rate is reached in a relatively short time, but the working machine is greatly extended and rotated. When the radius is large, as shown by the dotted line (b) in FIG. 6, it takes a long time to reach the necessary supply flow rate.

  Therefore, when the swing motor is started, the swing lever is operated to the maximum from the beginning, and when the constant increase curve shown by the solid line (a) in FIG. Is small, the difference between the dotted line (b) and the dotted line (a) is insufficient supply flow rate, while when the working machine has a large turning radius, the supply flow rate is excessive by the difference between the dotted line (a) and the dotted line (b). That is, useless relief is performed.

  In order to solve such problems, a control valve is provided between the hydraulic pump and the swing motor, and in the configuration in which the swing motor is controlled by bleed-off control, the bleed-off flow rate at the start of the turn is minimized, In order to obtain the characteristic that the turning acceleration pressure gradually decreases with time in the turning acceleration stage, the pump flow rate is increased by subtracting the flow amount obtained from the inertial mass and acceleration force of the turning body from the actual motor inflow rate increase. A turning hydraulic circuit is known (for example, see Patent Document 2).

The first detection means for detecting the pilot pressure from the pilot valve interlocked with the swing lever, and the second detection means for detecting the pressure generated in the pipe line between the flow control valve (control valve) and the swing motor. And a control device (controller) that outputs a command signal so as to switch the control valve (flow rate proportional valve) so as to reduce the discharge flow rate of the hydraulic pump based on the calculation result. A hydraulic circuit is also known (see, for example, Patent Document 3).
Japanese Examined Patent Publication No. 7-45748 JP 2005-16228 A JP-A-9-195322

  However, the hydraulic circuit described in Patent Document 2 requires motor flow rate detection means, inertial mass data detection means, and the like. Further, the hydraulic circuit described in Patent Document 3 requires complicated circuits such as a first detection unit that detects the pilot pressure from the pilot valve and a second detection unit that detects the pressure generated in the pipe of the swing motor. is there. In any case, there are problems such as expensive parts and complicated circuit configuration, poor economic efficiency, complicated system, and high cost.

  Therefore, there is a technical problem to be solved in order to realize energy saving by improving the efficiency and reducing the fuel consumption with a simple structure and economically excellent energy loss. It aims at solving this subject.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a hydraulic pump, a swing motor that is driven by oil discharged from the hydraulic pump to swing a swing body, and the swing A control valve that controls the rotational direction and speed of the motor, a regulator that controls the discharge flow rate of the hydraulic pump, and a negative control that generates a negative control pressure in the discharged oil that has passed through the control valve and applies the negative control pressure to the regulator. In a hydraulic control circuit of a construction machine having a circuit, a second negative control circuit is arranged separately from the negative control circuit, and a flow proportional valve for supplying pressure oil to the second negative control circuit is connected, A shuttle valve is provided for selecting the pressure oil in one negative control circuit to act on the regulator, and discharging the hydraulic pump. When the discharge pressure suddenly changes from the pressure sensor for detecting pressure and the detected value of the pressure sensor, the flow rate proportional valve is controlled to adjust the second negative control circuit pressure to increase or decrease the discharge flow rate of the hydraulic pump. Provided is a hydraulic control circuit for a construction machine, characterized in that the controller is provided with a controller.

  According to this configuration, when the discharge pressure of the hydraulic pump supplied to the swing motor is detected by the pressure sensor and the discharge pressure suddenly changes, the controller outputs a command signal to the flow rate proportional valve to output the command signal from the flow rate proportional valve to the second value. Adjust the pressure oil supplied to the negative control circuit. A hydraulic pressure is applied to the regulator by the shuttle valve selecting either the negative control pressure of the negative control circuit generated by passing through the control valve or the second negative control circuit generated by the flow rate proportional valve by the shuttle valve. The discharge flow rate is controlled. When turning is started, the discharge flow rate of the hydraulic pump becomes maximum, and if the detection value of the pressure sensor increases rapidly, the controller controls the discharge flow rate not to increase.

  According to a second aspect of the present invention, at the start of turning, the controller controls the flow rate proportional valve so as to restrict the flow rate supplied to the second negative control circuit to the minimum, thereby ensuring the discharge flow rate of the hydraulic pump. After the start of the turn, the controller controls the flow rate proportional valve so that the flow rate supplied to the second negative control circuit is increased by a predetermined time when the discharge pressure suddenly increases from the detection value of the pressure sensor. A hydraulic control circuit for a construction machine according to claim 1, wherein the hydraulic pump discharge circuit is configured to temporarily reduce the discharge flow rate of the hydraulic pump.

  According to this configuration, based on the change in the detected value of the pressure sensor, the flow rate supplied by the controller to the second negative control circuit is minimized by restricting the flow rate proportional valve at the time of turning start, and the discharge flow rate of the hydraulic pump is ensured. When the discharge pressure suddenly increases from the detection value of the pressure sensor after the start of the turning, the controller opens the flow rate proportional valve to increase the flow rate supplied to the second negative control circuit. Therefore, the second negative control circuit has a higher pressure than the negative control circuit, and high pressure oil from the shuttle valve acts on the regulator, and the discharge amount of the hydraulic pump is temporarily suppressed.

  The invention described in claim 1 is necessary for the turning motor to turn while sensing the discharge pressure detected by the pressure sensor, even if the flow rate required to rotate the turning body varies depending on the posture of the work implement and the like. The flow rate can be gradually increased. As a result, the discharge flow rate of the hydraulic pump can be maintained so that the true flow rate required for the rotation of the swing motor can be supplied to the swing motor regardless of the attitude of the work implement. Energy loss can be reduced, and energy saving can be realized by improving efficiency and reducing fuel consumption.

  According to the second aspect of the present invention, the discharge amount of the hydraulic pump is secured at the start of turning, and after the start of turning, when the discharge pressure of the hydraulic pump suddenly increases, it is determined that the supply is excessive and the increase in the discharge amount is suppressed. In addition to the effect of the invention described in item 1, it is possible to expect an effect that it is possible to provide a hydraulic control circuit for a construction machine that has a simple structure and is economically excellent.

  Driven by a hydraulic pump and oil discharged from the hydraulic pump in order to achieve the objectives of simple structure, excellent economics, low energy loss, improved efficiency and reduced energy consumption by reducing fuel consumption A swing motor that turns the swing body, a control valve that controls the rotation direction and speed of the swing motor, a regulator that controls the discharge flow rate of the hydraulic pump, and a negative control pressure applied to the discharged oil that has passed through the control valve. In a hydraulic control circuit of a construction machine having a negative control circuit that generates and applies the negative control pressure to the regulator, a second negative control circuit is disposed separately from the negative control circuit, and a pressure is applied to the second negative control circuit. Connect a flow proportional valve to supply oil, select either one of the negative control circuit pressure oil high pressure And a second pressure sensor for detecting the discharge pressure of the hydraulic pump, and when the discharge pressure suddenly changes from the detected value of the pressure sensor, the flow rate proportional valve is controlled to control the second negative control. This was realized by providing a controller capable of adjusting the circuit pressure and increasing / decreasing the discharge flow rate of the hydraulic pump.

  Hereinafter, a hydraulic control circuit for a construction machine according to the present invention will be described with reference to preferred embodiments.

  FIG. 1 is a schematic configuration diagram of a hydraulic control circuit shown as an embodiment of the present invention. Note that this hydraulic control circuit is applied to the hydraulic excavator as the construction machine shown in FIGS. 4 and 5, and the parts corresponding to the components of the construction machine shown in FIGS. 4 and 5 are the same. This will be described with reference numerals.

  In FIG. 1, the hydraulic control circuit is equipped with a hydraulic pump 12 that is driven to rotate by a prime mover such as an engine mounted on a hydraulic excavator. The hydraulic pump 12 is a variable displacement hydraulic pump, and has a variable displacement swash plate 12a of the hydraulic pump 12, and a regulator 14 is connected to the swash plate 12a. Further, on the center oil passage 16 of the hydraulic pump 12, the control valve 11 and the negative control throttle 18 are sequentially arranged downstream and connected to the tank T.

  The control valve 11 includes a travel switching valve 11a for controlling the travel of the lower traveling body 1, a swing motor switching valve 11b for operating the swing motor 10 for swinging the upper swing body 2, and an arm cylinder 7 in the work implement. An arm switching valve 11c to be operated, a boom switching valve 11d to operate the boom cylinder 5, a bucket cylinder switching valve 11e to operate the bucket cylinder 9, and the like are configured.

  The regulator 14 is connected to an output port of a shuttle valve 22, and the shuttle valve 22 has two input ports. A first negative control circuit 24 is connected to an input port on one side of the shuttle valve 22. In this first negative control circuit 24, a negative control generated by the oil that has passed through the control valve 11 being throttled by the negative control throttle 18. Pressure is introduced. A second negative control circuit 26 is connected to the other input port of the shuttle valve 22, and the second negative control circuit 26 is connected to the pilot negative pressure source 30 via a flow rate proportional valve 28 controlled by a controller 31. Pilot pressure oil is introduced. The shuttle valve 22 selects the higher pressure oil from the pressure oil in the first negative control circuit 24 and the pressure oil in the second negative control circuit 26, and supplies the selected pressure oil to the regulator 14. The regulator 14 is controlled.

  The controller 31 outputs a drive signal corresponding to the operation of the turning lever 32 that operates the work machine to each switching valve 11 a to 11 e of the control valve 11. A pressure sensor 33 is provided between the hydraulic pump 12 and the control valve 11, and the controller 31 detects the discharge pressure P1 of the hydraulic pump 12 from the input signal of the pressure sensor 33, and is proportional to the flow rate based on this detected value. A command current is output to the solenoid 28a of the valve 28.

  Subsequently, the operation of the present embodiment will be described. In addition, in order to simplify description, the case where the turning motor 10 is driven will be described, and the case where other working machines and the like are not driven will be described. FIG. 2 is a flowchart showing an example of the operation of the hydraulic control circuit according to the present embodiment. The operation of the hydraulic control circuit will be described in the order of step S1 to step S6 according to this flowchart.

  First, when the excavator stops traveling and the swing motor 10 is not driven, the hydraulic pump 12 is in an idling state, and all of the oil discharged from the hydraulic pump 12 is returned to the tank T. At this time, the negative control throttle 18 generates a high negative control pressure in the first negative control circuit 24. Further, the flow rate proportional valve 28 is also at the position a shown in FIG. 1, and the second negative control circuit 26 communicates with the hydraulic tank T and is at a low pressure, and is kept at a lower pressure than the hydraulic pressure of the first negative control circuit 24.

  Thereby, the shuttle valve 22 selects the high pressure oil on the first negative control circuit 24 side and supplies it to the regulator 14, and the regulator 14 controls the tilting amount of the swash plate 12a according to the negative control pressure. Thereby, the discharge flow rate of the hydraulic pump 12 during idling can be kept low, and energy saving can be achieved.

  Here, the controller 31 always monitors whether or not the turning operation has been performed by the operation lever 32 (step S1).

  When the turning operation is performed by the operation lever 32, the controller 31 switches the turning motor switching valve 11b to the turning side, the discharge oil from the hydraulic pump 12 is supplied to the turning motor 10, and the turning motor 10 is driven to rotate. The upper swing body 2 turns (step S2).

  Further, the controller 31 constantly senses the discharge pressure P1 from the pressure sensor 33, and monitors the change with time of the discharge pressure P1 when the rotation of the turning motor 10 is started. If the change amount of the discharge pressure P1 increases more than a predetermined inclination, it is determined that the pressure oil discharged from the hydraulic pump 12 is excessively supplied (step S3), and the controller 31 determines the solenoid 28a of the flow proportional valve 28. The command current is output only during time t1 (step S4). With this command current, the flow proportional valve 28 is switched to the position b shown in FIG. 1, and the pilot hydraulic source 30 communicates with the second negative control circuit 26 via the flow proportional valve 28. High pressure oil is led to the negative control circuit 26.

  Thus, the shuttle valve 22 selects the high pressure oil of the second negative control circuit 26 higher than the pressure oil of the first negative control circuit 24 and supplies it to the regulator 14, and the regulator 14 responds to this high pressure oil. The amount of tilt of the swash plate 12a is controlled to temporarily suppress the discharge flow rate of the hydraulic pump 12.

  When the time t1 elapses, the command current from the controller 31 is cut off, the flow proportional valve 28 is returned to the position a shown in FIG. 1 again, and the second negative control circuit 26 communicates with the hydraulic tank T. Accordingly, the pressure oil in the second negative control circuit 26 is lower than the pressure oil in the first negative control circuit 24. As a result, the shuttle valve 22 selects the negative control pressure from the first negative control circuit 24 and supplies it to the regulator 14, and the regulator 14 controls the amount of tilt of the swash plate 12a in accordance with the negative control pressure. Thus, the discharge flow rate is controlled from the hydraulic pump 12 according to the negative control pressure on the first negative control circuit 24 side, and this is supplied to the turning motor 10.

  In this operation, the operations of step S5 and step S6 are repeated in order until the rotation of the upper swing body 2 is stabilized and the discharge pressure P1 from the pressure sensor 33 becomes substantially constant. During the operation of the hydraulic excavator, the same operation is repeated every time the upper swing body 2 starts to rotate.

  FIG. 3 is a characteristic diagram of the discharge flow rate Q and the time t of the hydraulic pump 12 shown as an example of control in the hydraulic control circuit of the present embodiment. In FIG. 3, the range indicated by the symbol a is a state when the discharge flow rate from the hydraulic pump 12 is determined to be excessive supply, and high pressure oil on the second negative control circuit 26 side is applied to the supply regulator 14 for t1 time. When the high pressure oil on the second negative control circuit 26 side is applied, the increase in the discharge flow rate Q is suppressed. When the discharge flow rate Q is increased while being suppressed stepwise in this way, even if the flow rate required by the swing motor 10 changes due to the posture of the work machine or the like, the discharge flow rate of the hydraulic pump 12 is the true value required by the swing motor 10. The flow rate can be maintained.

  Thus, according to the present embodiment, the controller 31 senses the pressure of the discharge oil of the hydraulic pump 12 supplied to the turning motor 10 via the pressure sensor 33, and the amount of change in the discharge pressure P1 is determined. If the change suddenly is larger than a predetermined change amount, the supply flow rate to the swing motor 10 is suppressed by suppressing the discharge flow rate of the hydraulic pump 12 for a predetermined time t1. Then, by automatically repeating the operation of returning to the original state after the lapse of the predetermined time t1, the true flow rate required by the swing motor 10 for the discharge flow rate of the hydraulic pump 12 is not affected by the posture of the work implement or the like. Can be kept in. As a result, excessive pressure oil is supplied to the turning motor 10 and waste is returned to the tank from the relief valve or the like, so that there is little energy loss, improving efficiency and reducing fuel consumption. Energy saving.

  Further, since the above control can be realized by the controller 31 and the flow rate proportional valve 28 from the arithmetic circuit, a hydraulic control circuit for a construction machine having a simple structure and excellent economical efficiency can be provided.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

1 is a schematic configuration diagram of a hydraulic control circuit according to an embodiment of the present invention. The flowchart explaining operation | movement of the hydraulic control circuit shown in FIG. FIG. 3 is a flow characteristic diagram illustrating an operation example of the hydraulic control circuit shown in FIG. 1. An overall side view of a general excavator. The whole top view of a general hydraulic excavator. The flow characteristic figure explaining the problem of the conventional hydraulic control circuit.

Explanation of symbols

2 Upper swing body 10 Swing motor 11 Control valve 11b Swing motor switching valve 12 Hydraulic pump 12a Swash plate 14 Regulator 16 Center oil passage 18 Negative control throttle 22 Shuttle valve (high pressure selection means)
24 First negative control circuit 26 Second negative control circuit 28 Flow proportional valve 30 Pilot hydraulic power source 31 Controller 32 Operation lever 33 Pressure sensor

Claims (2)

A hydraulic pump, a swing motor that is driven by the oil discharged from the hydraulic pump to swing the swing body, a control valve that controls the rotation direction and speed of the swing motor, and a regulator that controls the discharge flow rate of the hydraulic pump; In a hydraulic control circuit for a construction machine, including a negative control circuit that generates a negative control pressure on the discharged oil that has passed through the control valve, and causes the negative control pressure to act on the regulator.
A second negative control circuit is arranged separately from the negative control circuit, and a flow proportional valve for supplying pressure oil to the second negative control circuit is connected, and the pressure oil of either negative control circuit is selected to be a high pressure regulator Provide a shuttle valve to act on
A pressure sensor for detecting a discharge pressure of the hydraulic pump;
A controller that can control the flow rate proportional valve to adjust the second negative control circuit pressure to increase or decrease the discharge flow rate of the hydraulic pump when the discharge pressure changes suddenly from the detection value of the pressure sensor; Hydraulic control circuit for construction machinery. At the time of turning start, the controller controls the flow rate proportional valve so as to reduce the flow rate supplied to the second negative control circuit to the minimum, and ensures the discharge flow rate of the hydraulic pump,
After the start of turning, when the discharge pressure suddenly increases from the detection value of the pressure sensor, the controller controls the flow rate proportional valve so as to increase the flow rate supplied to the second negative control circuit for a predetermined time, 2. The hydraulic control circuit for a construction machine according to claim 1, wherein the hydraulic pump is configured to temporarily reduce a discharge flow rate of the hydraulic pump.

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