JPH05287774A - Energy regenerator of hydraulic excavator - Google Patents

Abstract

PURPOSE:To enhance the effect of energy saving by giving assistance at an time, if necessary, without limiting a regeneration object of energy collected by an accumulator to a specific actuator in a hydraulic excavator. CONSTITUTION:When pressure storage in an accumulator is less than set pressure, and in the case of boom down control or turning control, solenoid valves 15 and 21 provided to a pipe line 14a or a pipe line 14e reaching a pressure pipe line of a bottom side pipe line or a turning hydraulic motor 10 of an assist cylinder 12 from the accumulator 13 are opened to store pressure in the accumulator 13 in the case a lever control amount is in excess of set value. When pressure storage in the accumulator is in excess of set pressure, and in the case an engine load and a lever control amount are respectively in excess of specific value against boom-up, arm excavation, bucket excavation and turning control, applicable solenoid valves among solenoid valves 15, 18, 20, 21 and 23 are opened to control the supply of collected energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy recovery system for a hydraulic excavator.

[0002]

2. Description of the Related Art In a hydraulic excavator in which a work machine having a boom, an arm, a bucket and the like rotatably connected to each other is mounted on an upper revolving structure, an accumulator provided in a hydraulic circuit is one of energy saving measures. BACKGROUND ART There is known an energy regenerator as described below, which collects energy by accumulating the pressure in a box and uses it as needed. (1) A work machine weight canceling system that guides a part of the pressure oil returned from the boom cylinder bottom side to the oil tank to the accumulator and accumulates the pressure when operating the work machine, for example, when lowering the boom. (2) A system for guiding a portion of the pressure oil returned from the swing motor to the oil tank to the accumulator and accumulating the pressure when the upper swing body is swung and stopped. The work implement weight cancellation system in (1) above utilizes the energy recovered by the boom lowering operation only for the boom raising operation, and the pressure accumulation system in (2) uses the energy recovered by the swing operation for the swing operation. It is used only for.

[0003]

Of all the work of the hydraulic excavator, the proportion of boom raising operation or turning operation is not so large, so there is little opportunity to utilize the recovered energy as an assist, and therefore the conventional energy is not used. The energy saving effect is small in the recovery system. Further, even if the engine output has a margin due to light work or the like, the assist is automatically performed. Therefore, in such a case, energy saving cannot be achieved. The present invention has been made focusing on the above-mentioned conventional problems, and does not limit the assist target of the energy stored in the accumulator, and when it is necessary for the working machine driving hydraulic cylinder, the turning hydraulic motor, and the engine. It is an object of the present invention to provide an energy recovery device for a hydraulic excavator that can enhance the energy saving effect by assisting at any time.

[0004]

In order to achieve the above object, an energy recovery device for a hydraulic excavator according to the present invention comprises a boom raising and lowering operation, an arm excavating operation, a bucket excavating operation, and a swinging operation of an upper swing body. At
A pressure switch that operates when the lever operation amount exceeds a predetermined value, an accumulator that collects and accumulates energy obtained when the boom is lowered and when turning is stopped, and the accumulator pressure and the boom cylinder, arm cylinder, and bucket cylinder Pressure sensors that detect the pressure on the bottom side and the pressure of the hydraulic motor for swing, a rotation speed sensor that detects the rotation speed of the engine, a conduit from the accumulator to the bottom side of the assist cylinder that assists the boom raising operation, arm cylinder A solenoid valve provided in each of the pipelines that reach the bottom side of the bucket cylinder, and the pipelines that extend from the accumulator to the pressure pipeline of the turning hydraulic motor and the suction pipeline of the assist hydraulic pump driven by the engine. , Of the pressure switch, pressure sensor and speed sensor A control device that outputs an opening / closing command signal to the solenoid valve based on the force signal is provided, and in such a configuration, the control device, when the accumulated pressure of the accumulator is less than a set pressure, performs a boom lowering operation or a swing operation. During operation, when the lever operation amount exceeds a specified value,
Open the solenoid valve provided in the pipeline from the accumulator to the bottom side of the assist cylinder or in the pipeline from the accumulator to the pressure pipeline of the turning hydraulic motor to accumulate pressure in the accumulator, and if the accumulated pressure in the accumulator is at or above the set pressure, For each of boom raising operation, arm excavation operation, bucket excavation operation, and turning operation, when the engine load and lever operation amount exceed a specified value, the corresponding solenoid valve is opened to supply the recovered energy. It is supposed to control.

[0005]

According to the above construction, when the accumulated pressure of the accumulator is less than the set pressure, during boom lowering operation or turning operation,
When the lever operation amount exceeds a predetermined value, a solenoid valve provided in the bottom side conduit of the assist cylinder or the pressure conduit of the turning hydraulic motor is opened, and pressure is accumulated in the accumulator. Therefore, energy can be efficiently recovered using the pressure oil returned to the oil tank. When the accumulated pressure in the accumulator exceeds the set pressure, when the engine load and lever operation amount exceed the specified values for boom raising operation, arm excavation operation, bucket excavation operation, and turning operation, respectively, the accumulator outputs Of the solenoid valves installed in the pipelines that lead to the hydraulic cylinders for driving the work equipment, the hydraulic motors for turning, and the suction pipelines of the assist hydraulic pump that is driven by the engine, open the relevant solenoid valve and collect it. Since the energy is supplied, the target of the recovery of the recovered energy is not limited to the specific actuator. Therefore, the working machine driving hydraulic cylinder, the turning hydraulic motor, and the engine can be assisted as needed, and the energy saving effect can be enhanced by effectively utilizing the recovered energy.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an energy recovery system for a hydraulic excavator according to the present invention will be described below with reference to the drawings. FIG. 1 shows only the part related to the energy regeneration device in the hydraulic / electric circuit of the hydraulic excavator, and the circuits other than this device are omitted. In the figure, an engine 1 drives a main hydraulic pump 2, a pilot hydraulic pump 3, an assist hydraulic pump 4, and a turning hydraulic pump 5, and a pressure line of the main hydraulic pump 2 passes through a main operating valve (not shown), It is connected to two boom cylinders 6, an arm cylinder 7, a bucket cylinder 8 and the like. Further, the pressure pipeline 5 a of the swing hydraulic pump 5 is connected to the swing hydraulic motor 10 via the swing operation valve 9, and the pressure pipeline 4 a of the assist hydraulic pump 4 is guided to the oil tank 11. .. An assist cylinder 12 is provided between the two boom cylinders 6.

Of the pipelines from the accumulator 13 to the actuators, the pipelines 14 branching from the pipelines 14
a is connected to the bottom side of the assist cylinder 12 via a solenoid valve 15, and the conduit 14b is connected to the bottom side of the boom cylinder 6 via a stop valve 16. In addition, pipeline 1
4c is on the bottom side of the arm cylinder 7 via the check valve 17 and the solenoid valve 18, the pipe line 14d is on the bottom side of the bucket cylinder 8 via the check valve 19 and the solenoid valve 20, and the pipe line 14e is The solenoid valve 21 and the check valve 22 are connected to the pressure pipeline 5a, and the pipeline 14f is connected to the suction pipeline 4b of the assist hydraulic pump 4 via the solenoid valve 23. The solenoid valves 15, 18, 20, 21, 23
Are operated by a command current output by the controller 24.

A pressure sensor 25 for detecting the pressure of the accumulator 13 is attached to the pipe line 14, and the pipe line 14b,
Pressure sensors 26, 27 and 2 are provided on 14c and 14d, respectively.
8 is attached. The branch line 14g of the line 14e is
A pressure sensor 32 that is connected to the pressure pipe of the turning hydraulic motor 10 via the sequence valve 29 and the check valve 30 or the check valve 31 and detects the pressure of the branch pipe 14g is attached. A rotation speed sensor 33 is attached to the engine 1, and output wirings of these pressure sensor and rotation speed sensor are both connected to the controller 24.

Pressure switches 35 and 36 which are activated when the boom / bucket operating lever 34 provided in the driver's seat is operated to raise or lower the boom and the pilot pressure generated in proportion to the lever operation amount reaches a set value. The output wiring between the control lever 34 and the pressure switch 37 which is operated when the pilot pressure reaches a set value by operating the operation lever 34 toward the bucket excavation side is connected to the controller 24. Also, the output wiring of the pressure switches 39 and 40, which are activated when the pilot pressure generated in proportion to the lever operation amount reaches a set value by operating or turning the arm / turn control lever 38 toward the arm excavation side. , Controller 2
4 is connected.

When accumulating pressure in the accumulator 13, the stop valve 16 is closed and the boom is first raised, and then the boom is lowered to operate the lever. Since the pressure of the accumulator 13 is low, the solenoid valve 15 is in the ON state, and a part of the pressure oil flowing out from the bottom side of the assist cylinder 12 passes through the pipeline 14 a and the pipeline 14 to accumulate the accumulator 13.
Flows into and accumulates pressure. When the pressure accumulation is completed and the pressure exceeds the set pressure, the solenoid valve 15 is turned off. Subsequent energy recovery, that is, pressure accumulation is performed by the assist cylinder 12 and the turning hydraulic motor 10. In addition, as for the assistance of the engine output, the present inventor has already made an application in Japanese Patent Application No. 4-909
It is the same as the one applied for No. 0, the electromagnetic valve 23 is turned on, and pressure oil is sent from the accumulator 13 to the suction pipe line 4b of the assist hydraulic pump 4, so that the assist hydraulic pump 4 operates at a speed equal to or higher than the engine speed. Rotate with
The engine output is temporarily increased.

FIG. 2 is a block diagram of a controller used in the energy regenerator. As described above, when the work implement operation lever is operated to the boom raising side or the boom lowering side, the bucket excavating side, the arm excavating side, or the turning operation is performed and each pilot pressure reaches the set value, the pressure switches 35, 36, The output signals of 37, 39, 40 are input to the solenoid valve opening / closing command signal output means 51 in the controller 24. The output signal of the pressure sensor 25 for detecting the accumulator pressure is subjected to calculation processing by the pressure calculation means 52 of the accumulator and then inputted to the accumulator quality determination means 53,
Whether the accumulated pressure is good or bad is judged by comparing with the accumulator set pressure output from the accumulator set pressure storage means 54.

When the accumulated pressure is less than the set pressure, the accumulated pressure must be accumulated. Therefore, the boom lowering operation, the swing operation, or the combined operation of the boom lowering operation and the swing operation is performed by the pressure switch 36 or 4.
When 0 is detected, the solenoid valve opening / closing command signal output means 51 outputs an ON command signal to both the solenoid valve 15, the solenoid valve 21, or both solenoid valves 15 and 21, and these solenoid valves are excited. As a result, a part of the pressure oil returned from the assist cylinder 12 or the turning hydraulic motor 10 to the oil tank flows into the accumulator, and the pressure is accumulated.

The calculation result by the pressure calculation means 52 of the accumulator is also input to the comparison / determination means 55 between the measured value of the accumulated pressure and the load pressure. The output signals of the pressure sensors 26, 27, 28, 32 for detecting the load pressures of the boom cylinder, the arm cylinder, the bucket cylinder, and the turning hydraulic motor are subjected to calculation processing by the load pressure calculating means 56,
The measured / accumulated pressure value and the load pressure are input to the comparison / determination means 55. Revolution sensor 3 for detecting engine revolution
The output signal of No. 3 is subjected to calculation processing by the rotation speed calculation means 57 and then input to the engine load determination means 58, compared with the engine rotation speed setting range output from the engine rotation speed setting range storage means 59, The load is determined. Here, the setting range of the engine speed is a range from the vicinity of the engine maximum torque point to the vicinity of the rated torque point. The above-mentioned judgment result of the accumulated pressure, the comparison result of the measured value of accumulated pressure and the load pressure, and the judgment result of the engine load are all inputted to the solenoid valve opening / closing command signal output means 51, and the solenoid valve opening / closing command signal output means 51. ON / O of each solenoid valve 15, 18, 20, 21, 23 by the command signal output by
FF is performed.

When the accumulated pressure in the accumulator 13 is equal to or higher than the set pressure, energy is regenerated. Pressure switch 3
If any one of 5, 37, 39, 40 is ON and the engine load determination means 58 determines that the engine load is large, the solenoid valve 15, 18, 20, 21 corresponds to the pressure switch. The solenoid valve and the solenoid valve 23 are excited, and energy is supplied from the accumulator to the target actuator and the engine.

FIG. 3, FIG. 4 and FIG. 5 are flowcharts for executing control of the energy regeneration system device. In these figures, the numbers in the upper left corner of each step indicate the step number. In FIG. 3, when the operation lever is moved and one or more output signals of the pressure switch that operates when the pilot pressure becomes equal to or higher than the set value is input, the controller is activated and the control program is started. First, in step 1, it is determined whether or not the accumulated pressure of the accumulator is equal to or higher than the set pressure, and if it is equal to or higher than the set pressure, energy regeneration is performed. Energy regeneration will be described with reference to FIGS. 4 and 5. If the accumulated pressure in the accumulator is less than the set pressure, enter the energy recovery program,
In step 2, it is determined whether the lever operation is only the boom lowering operation. This determination is YES if the pressure switch 36 for the boom lowering side pilot pressure is ON, and in that case, the solenoid valve 15 is turned ON in step 3.
As a result, the pressure oil flowing out from the bottom side of the assist cylinder 12 flows into the accumulator, and the pressure is accumulated in the accumulator. If the determination in step 2 is NO, the process proceeds to step 4, and it is determined whether or not the lever operation is only turning in the same manner as described above, and if YES, the solenoid valve 21 is turned on in step 5. As a result, the pressure oil flowing out from the turning hydraulic motor 10 when the turning is stopped flows into the accumulator, and the accumulator accumulates pressure. If the determination in step 4 is also NO, the process proceeds to step 6 to determine whether or not the lever operation is a combined operation of boom lowering and turning, and both pressure switches 36 and 40 are O.
If it is N, it becomes YES, and in step 7, the solenoid valves 15 and 2
Turn 1 on. As a result, the pressure oil flowing from the bottom side of the assist cylinder 12 and the turning hydraulic motor 10 flows into the accumulator, and the accumulator accumulates pressure. If the determination in step 6 is also NO, the process returns to step 2.

In step 3, 5 or 7 above, the solenoid valve 1
5 or solenoid valve 21 or solenoid valves 15 and 21 are ON
However, in Steps 8, 9 and 10, it is judged whether or not the operation state of each lever is continued based on ON and OFF of each pressure switch, and if YES, Step 3 or Step 5 respectively. Alternatively, returning to step 7, the state of each solenoid valve ON is continued. If NO in steps 8, 9 and 10, step 11
Switch each solenoid valve from ON to OFF and return to step 1.

FIG. 4 is a flow chart of energy regeneration during boom raising operation and arm excavation operation. In the case of a boom raising operation, it is determined in step 1 whether or not the pressure switch 35 is ON, and if YES, it is determined in step 2 whether or not the engine speed is within the set range, and if YES, the step Solenoid valve 15 and solenoid valve 2 in 3
Turn 3 and ON. As a result, the pressure oil is filled in the pipeline 14a from the accumulator to the assist cylinder bottom side and the pipeline 14f to the suction pipeline 4b of the assist hydraulic pump 4, so that in step 4, the accumulated pressure of the accumulator is equal to or higher than the set pressure. If YES, it is again determined in step 5 whether the pressure switch 35 is ON. Then, if the ON state of the switch continues, the process returns to step 3. That is, while the pressure switch on the boom raising side is ON, the pressure oil in the accumulator flows into the assist cylinder bottom side and the suction side of the assist hydraulic pump, and energy regeneration in the boom raising operation is performed. If the determination in step 2 is NO, the engine load is comparatively light and no assistance is required, so energy is not regenerated. If the determination in step 4 or step 5 is NO, the process proceeds to step 6, the solenoid valves 15 and 23 are turned off, and the energy recovery flow ends.

In the case of arm excavation operation, it is determined in step 7 whether the pressure switch 39 is ON, and if YES, it is determined in step 8 whether the engine speed is within the set range. If this determination is also YES, step 9
Then, the accumulator pressure P13 detected by the pressure sensor 25 is compared with the arm cylinder bottom side pressure P7 detected by the pressure sensor 27. If P13> P7, the solenoid valve 18 and the solenoid valve 23 are connected in step 10. Turn it on. As a result, the pressure oil is filled in the pipeline 14c from the accumulator to the arm cylinder bottom side and the pipeline 14f to the suction pipeline 4b of the assist hydraulic pump 4, so that in step 11, the accumulated pressure of the accumulator is equal to or higher than the set pressure. If YES, it is determined again in step 12 whether the pressure switch 39 is ON. If the ON state of the switch continues, the process returns to step 10. The determination in step 11 or step 12 is NO.
In the case of, proceed to step 13 and set the solenoid valves 18 and 23 to OF
Set to F, and the flow of energy regeneration ends.

FIG. 5 is a flowchart of energy recovery during bucket excavation operation and turning operation.
The flow is the same as that of the arm excavation operation shown in FIG.
That is, when the pressure switch is ON and the engine speed is within the set range, the accumulator pressure P13 is compared with the bucket cylinder bottom side pressure P8 or the swing hydraulic motor pressure P10, and P13> P8 or P13> P10. If so, the solenoid valves 20, 23 or the solenoid valves 21, 23 are turned on. Further, it is determined whether the accumulated pressure in the accumulator is equal to or higher than the set pressure and whether the pressure switch is ON, and the open / close command signal for the solenoid valve is output.

In this embodiment, the controller is activated when one or more pressure switches are operated by moving the operation lever, but the invention is not limited to this, and the controller may be activated when the engine is started.

[0021]

As described above, according to the present invention, when the accumulated pressure of the accumulator is less than the set pressure, the boom lowering operation or the turning operation is performed, and when the lever operation amount becomes a predetermined value or more, The pressure oil returned to the oil tank is used to efficiently accumulate pressure in the accumulator. When the accumulated pressure in the accumulator exceeds the set pressure and the engine load and lever operation amount both exceed the specified values, it was decided to supply the recovered energy to the work implement, the swing actuator, and the engine. As described above, the assisting target is not limited to a specific actuator or assisting when the engine output has a margin, and the recovered energy can be effectively used for the working machine, the engine, or the like that requires the assisting. Thereby, the energy saving effect can be further enhanced.

[Brief description of drawings]

FIG. 1 is a hydraulic / electrical circuit diagram of an energy recovery device mounted on a hydraulic excavator.

FIG. 2 is a block diagram of a control device that controls the energy regeneration device.

FIG. 3 is a flowchart for executing control of energy recovery.

FIG. 4 is a flowchart for executing control of energy regeneration, showing a case of boom raising operation and arm excavation operation.

FIG. 5 is a flowchart for executing control of energy regeneration, showing a case of bucket excavation operation and turning operation.

[Explanation of symbols]

1 Engine 4 Assist Hydraulic Pump 4a, 5a Pressure Pipeline 4b Suction Pipeline 6 Boom Cylinder 7 Arm Cylinder 8 Bucket Cylinder 10 Turning Hydraulic Motor 12 Assist Cylinder 13 Accumulator 14, 14a, 14b. 14c, 14d, 14e, 14
f Pipe line 15, 18, 20, 21, 23 Solenoid valve 24 Control device (controller) 25, 26, 27, 28, 32 Pressure sensor 33 Rotation speed sensor 35, 36, 37, 39, 40 Pressure switch

Claims (2)

[Claims] 1. A pressure switch that is activated when a lever operation amount reaches or exceeds a predetermined value in boom raising and lowering operations of a hydraulic excavator, arm excavating operations, bucket excavating operations, and swing operations of an upper swing body, An accumulator that collects and accumulates energy obtained when the boom is lowered and the swing is stopped, and a pressure sensor that detects the pressure of the accumulator, the bottom side pressure of the boom cylinder, arm cylinder, and bucket cylinder, and the pressure of the swing hydraulic motor, respectively. A rotation speed sensor that detects the number of rotations of the engine, a conduit from the accumulator to the bottom side of the assist cylinder that assists the boom raising operation, a conduit to the bottom side of each of the arm cylinders and bucket cylinders, and the hydraulic pressure for turning from the accumulator. Driven by motor pressure line and engine A solenoid valve provided in each of the pipelines leading to the suction pipeline of the assist hydraulic pump, and a control device that outputs an opening / closing command signal to the solenoid valve based on the output signals of the pressure switch, the pressure sensor, and the rotation speed sensor. An energy recovery device for a hydraulic excavator, characterized by comprising: 2. The control device according to claim 1, when the accumulated pressure of the accumulator is less than a set pressure, during a boom lowering operation or a turning operation, when the lever operation amount becomes a predetermined value or more,
Open the solenoid valve provided in the pipeline from the accumulator to the bottom side of the assist cylinder or in the pipeline from the accumulator to the pressure pipeline of the turning hydraulic motor to accumulate pressure in the accumulator, and if the accumulated pressure in the accumulator is at or above the set pressure, For each of boom raising operation, arm excavation operation, bucket excavation operation, and turning operation, when the engine load and lever operation amount exceed a specified value, the corresponding solenoid valve is opened to supply the recovered energy. An energy regeneration device for a hydraulic excavator, which is characterized in that it is configured to perform a control.