JP2003074517A - Controlling method of hydraulic cylinder circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a power regenerating operation and normal operation possible while an oversupply and short supply for the flowing amount of a pump are well solved, in a method driving the pump by an electric motor and in a cylinder circuit in which external force acts on a cylinder. SOLUTION: A boom cylinder 14 is driven to an extending and contracting direction by means of one hydraulic pump 12 driven by the electric motor 11 in an one pump formation. When the boom cylinder 14 is operated to the same direction with a direction of external force W, power regeneration is performed by flowing oil of a cylinder oil chamber located at an acting side of pressure by the external force W into the pump 12. When the boom cylinder 14 is operated to the opposite direction to the direction of the external force, normal cylinder motion is performed by supplying pump-discharged oil to the oil chamber located at an acting side of pressure by the external force W.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a hydraulic cylinder circuit in which oil is discharged from a hydraulic cylinder to drive a hydraulic pump to regenerate power.

[0002]

2. Description of the Related Art In a hydraulic cylinder circuit of an electric motor drive system in which a hydraulic pump as a hydraulic pressure source of a hydraulic cylinder is driven by an electric motor, from the viewpoint of efficient use of energy, the expansion / contraction force acting on the hydraulic cylinder by an external force is used as power. There is a demand for recovery (power regeneration) to a battery via a hydraulic cylinder, a hydraulic pump, and an electric motor.

For example, a boom of a hydraulic excavator always receives a downward force due to the weight of a work attachment including the boom, and an external force in a reducing direction acts on a boom cylinder that drives the boom.

At this time, in the boom cylinder, pressure is raised in the head-side oil chamber due to the external force in the contracting direction. Therefore, when the cylinder is contracted, only the head-side oil chamber needs to be drained. Oil flowing from the cylinder can rotate the hydraulic pump to drive the electric motor to regenerate power.

FIG. 3 shows the principle configuration of a conventional hydraulic cylinder circuit for performing this power regeneration. The case of the boom cylinder circuit of the hydraulic excavator will be described.

In this circuit, both the head-side and rod-side hydraulic pumps (hereinafter referred to as head-side pump and rod-side pump) 2 and 3 are driven by the electric motor 1 to discharge the discharged oil from the one-rod type boom cylinder 4. The oil is supplied to the head side oil chamber 4a or the rod side oil chamber 4b. T is a tank.

As described above, a downward force acts on the boom cylinder 4 as indicated by an arrow in the figure, and a pressure is generated in the cylinder head side oil chamber 4a (shown by hatching).

When the boom cylinder 4 is extended in this situation, the head side pump 2 is driven by rotating the electric motor 1 in the normal direction, and the discharged oil is supplied to the head side oil chamber 4a. By doing so, the cylinder 4 is extended and the oil discharged from the rod-side oil chamber 4b flows into the rod-side pump 3 to rotate it, and this rotational force is applied to the electric motor 1
Power regeneration is performed by being added to.

On the other hand, when the boom cylinder 4 is contracted, the electric motor 1 is rotated in the reverse direction to drive the rod side pump 3 to supply the discharge oil to the rod side oil chamber 4b.

At this time, the high pressure oil generated by the external force is sucked into the head side pump 2 from the head side oil chamber 4a. As a result, the pump 2 performs a stronger motor action than in the case of the rod side pump 3 during the cylinder extension operation, so that a higher power regeneration action is performed.

[0011]

However, since the boom cylinder 4 is of the single rod type, that is, there is a difference in volume between the head-side and the rod-side oil chambers 4a and 4b, the following problems occur.

For example, when the cylinder is extended, oil is supplied from the head side pump 2 to the head side oil chamber 4a as described above, and at the same time, the oil in the rod side oil chamber 4b flows into the rod side pump 3.

At this time, since the inflow flow rate into the rod side pump 3 is smaller than the outflow flow rate from the head side pump 2 due to the volume difference between the oil chambers 4a and 4b on both sides, it is assumed that the two pumps 2 and 3 have the same capacity. Cavitation occurs due to insufficient inflow of the rod-side pump 3.

On the contrary, when the cylinder is contracted, the outflow rate from the head side oil chamber 4a becomes larger than the inflow rate into the rod side oil chamber 4b, and the pressure on the head side becomes high.

In order to eliminate such excess and deficiency of the flow rate on the head side and the rod side, conventionally, the volume ratio of both head side and rod side pumps 2, 3 is the same as the volume ratio of both side oil chambers 4a, 4b. Is set to.

However, in the relationship of pump flow rate = rotational speed × pump capacity × volumetric efficiency, the volumetric efficiency greatly changes depending on the pressure, and also changes with the rotational speed, and furthermore, individual differences also affect. For this reason, the capacity ratio of the pump is set to
The excess and deficiency of the flow rate cannot be sufficiently eliminated only by adjusting the volume ratio of 4b.

Further, both head side and rod side pumps 2,
It is conceivable to rotate 3 at different rotation speeds by different electric motors, but this does not provide a fundamental solution because the problem of difference in pump volume efficiency remains. Moreover, adding an electric motor is disadvantageous in terms of equipment cost and space.

Therefore, the present invention adopts a method of driving a pump by an electric motor, and performs power regeneration operation and normal operation while solving the problem of excess and deficiency of pump flow rate in a cylinder circuit in which an external force acts on the cylinder. It provides a control method capable of

[0019]

According to a first aspect of the present invention, a single hydraulic pump is driven by an electric motor, and the discharge oil of the hydraulic pump is passed through a direction switching valve to a head-side oil chamber of a one-rod hydraulic cylinder. Alternatively, it is configured to supply to the rod-side oil chamber, the direction of the external force acting on the hydraulic cylinder is detected, and (a) when the hydraulic cylinder is operated in the same direction as the external force, the power regeneration mode is set as follows. The oil in the cylinder oil chamber on the side on which the pressure due to the external force acts is introduced into the hydraulic pump to perform power regeneration, and (b) when the hydraulic cylinder is operated in the direction opposite to the direction of the external force, the normal operation mode is set as above. The hydraulic pump is driven by the electric motor to supply oil to the cylinder oil chamber on the side where the pressure due to the external force acts.

According to a second aspect of the present invention, in the method of the first aspect, when the hydraulic cylinder is contracted under the condition that an external force in the contracting direction acts on the hydraulic cylinder, the oil chambers on both sides of the hydraulic cylinder are provided with a directional control valve. It is intended to communicate via.

According to the above method, since one hydraulic pump drives the hydraulic cylinders in the expansion and contraction directions, the problem of excess and deficiency of the flow rate of both pumps unlike the case of using two pumps does not occur.

Moreover, when the hydraulic cylinder is operated in the same direction as the external force, the oil in the cylinder oil chamber on the side where the pressure is applied by the external force is introduced into the pump for power regeneration, and when operating in the opposite direction. The normal operation can be performed by supplying the pump discharge oil to the oil chamber on the side where the pressure due to the external force acts.

That is, the power regeneration operation and the normal operation can be performed without any trouble while adopting the one-pump system in which the problem of excess or deficiency of the flow rate does not occur.

By the way, in this circuit configuration, when the hydraulic cylinder is contracted under the condition that an external force in the contracting direction is applied to the hydraulic cylinder, when the external force (load) is small, the pressure generated in the head side oil chamber (the head side oil chamber). The pressure of the oil that flows into the pump from = the force that rotates the pump also weakens,
The efficiency of power regeneration is reduced.

In this respect, according to the method of claim 2, in the above situation, since the oil chambers on both sides of the hydraulic cylinder are communicated with each other through the direction switching valve, the oil chambers on both sides of the cylinder have the same pressure.
The pressure in the head side oil chamber is increased. Therefore, even if the external force is small, the pump can be rotated at a high pressure to efficiently perform the power regeneration operation.

[0026]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS.

First Embodiment (see FIG. 1) In this cylinder circuit, one electric motor 11 drives one hydraulic pump 12, and the discharged oil is hydraulically supplied via an electromagnetic-hydraulic pilot type directional switching valve 13. A cylinder (which will be described below in the case of a boom cylinder of a hydraulic excavator in accordance with the description of the prior art) 14 is supplied to the head side oil chamber 14a or the rod side oil chamber 14b.

The electric motor 11 is connected to a controller 16 via an inverter 15 and is operated by a lever 1
The operation (rotation / stop / rotation speed) is controlled by a command signal from the controller 16 based on the operation of 7.

A battery 18 is connected to the inverter 15, and electric energy generated by power regeneration is stored in the battery 18.

The directional control valve 13 has a neutral position a, a first position b on the lower side of the drawing, and a second position c on the upper side of the drawing, and an electric signal from the controller 16 is provided between these positions. The operation is switched to control the operation of the boom cylinder 14.

That is, when neither of the solenoids 13a, 13b on both sides of the direction switching valve 13 is energized, the switching valve 13 is in the neutral position B. At this time, the boom cylinder 14 is not supplied with oil and is prevented from flowing out of the boom cylinder 14, so that the boom cylinder 14 does not operate.

When the first solenoid 13a on the lower side of the direction switching valve 13 is energized, the switching valve 13 is switched to the first position b. At this time, the head-side oil chamber 14a of the boom cylinder 14 communicates with the pump 12, and the rod-side oil chamber 14b of the boom cylinder 14 communicates with the tank T via the tank line 19.

When the second solenoid 13b on the upper side of the directional control valve 13 is energized, the directional control valve 13 switches to the second position C. At this time, the head side oil chamber 14a of the boom cylinder 14 communicates with the tank T via the tank line 19, and the rod side oil chamber 14b communicates with the pump 12.

Reference numeral 20 denotes a head side pipe line connecting the direction switching valve 13 and the head side oil chamber 14a of the boom cylinder 14,
Reference numeral 21 denotes a rod-side conduit that connects the switching valve 13 and the rod-side oil chamber 14b, and the head-side conduit 20 is provided with a pilot check valve 22 that functions as a holding valve.
Pressure sensors 23, 23 for detecting the pressure in the oil chambers 14a, 14b (the direction of the external force acting on the cylinder 14) are provided in the pipes 20, 21 on both sides.

Reference numeral 24 is a pilot pump as a pilot pressure source for the direction switching valve 13 and pilot check valve 22, 25 is a pilot pump electric motor for driving the pilot pump 24, and 26 is a pilot check valve 22.
The pilot check valve 22 is opened by the pilot pressure when the solenoid valve 26 is switched from the off position a on the right side of the figure to the on position b on the left side of the figure by a signal from the controller 16.

In FIG. 1, 27 is a main relief valve,
28 is a relief valve for pilot pressure source, 29 is a pump 12
And a check valve for preventing backflow provided between the tank and the tank T.

Next, the operation of this cylinder circuit will be described.

A. During normal work As described above, during normal work, the external force W due to the total weight of the attachment weight including the boom and the load acts on the boom cylinder 14 as a force in the cylinder contracting direction. 14a).

This situation is detected by the controller 16 based on the pressure signals from the pressure sensors 23, 23.

When the cylinder 14 is extended / reduced in this situation, the controller 1 based on the operation of the operation body 17 is used.
An electric signal from 6 energizes the first solenoid 13a of the directional control valve 13 to switch the directional control valve 13 to the first position b. Further, the solenoid valve 26 is also energized and switched to the ON position B.

As a result, as described above, the cylinder 14
Head side oil chamber 14a of the pump 12, the rod side oil chamber 1
4b are connected to the tank T, respectively.

At this time, when the operating body 17 is operated in the cylinder extending direction, the electric motor 11 rotates in the normal direction on the basis of a signal from the controller 16, that is, the pump 12
Rotates in the direction in which the original pump action is performed (discharging oil), and the pump discharge oil is transferred to the head side oil chamber 14a of the cylinder 14.
Oil in the rod-side oil chamber 14b is discharged to the tank T via the rod-side conduit 21, the direction switching valve 13, and the tank line 19.

As a result, the cylinder 14 is extended. However, at this time, the power regeneration action is not performed.

On the other hand, when the operating body 17 is operated in the cylinder contracting direction, the signal from the controller 16 causes the electric motor 11 to rotate in the reverse direction, that is, the pump 12 rotates in a direction in which oil is sucked to perform a motor action. The oil in the head side oil chamber 14a is sucked into the pump 12. At this time, the oil in the tank T is sucked up into the rod-side oil chamber 14b through the tank line 19 and the rod-side conduit 21.

In this way, the power regeneration operation is performed when the cylinder 14 is contracted while the external force W in the contraction direction is being applied to the cylinder 14.

When the cylinder is expanded or contracted, the electric motor 11
The inching control of the cylinder 14 can be performed by gradually operating the directional control valve 13 with a constant rotation speed.

B. In a hydraulic excavator during special work, the suspension may be inspected or cleaned while the boom is lowered and the attachment is pressed against the ground so that the vehicle body is raised forward.

During this special work, the boom cylinder 14
In contrast, the external force W in the upward direction (cylinder extension direction) acts contrary to the time of the normal work, and the rod side oil chamber 14b is in a state of having a pressure.

When the cylinder 14 is extended in this state, the direction switching valve 13 is set to the first position B and the electric motor 11 rotates in the normal direction, as in the above-mentioned normal operation.

As a result, the oil discharged from the pump 12 is supplied to the head-side oil chamber 14a, and at the same time, the rod-side oil chamber 14a.
The oil of b is discharged to the tank T and the cylinder 14 extends.

When the cylinder 14 is reduced,
The electric motor 11 rotates in the normal direction, the direction switching valve 13 is switched to the second position C, and the solenoid valve 26 is set to the ON position B. In this state, the pump discharge oil is supplied to the rod-side oil chamber 14b, and at the same time, the oil in the head-side oil chamber 14a returns to the tank T and the cylinder 14 shrinks.

When the cylinder is extended during this special work, the power regeneration action can be obtained by switching the direction switching valve 13 to the second position C so that the oil in the rod side oil chamber 14b flows into the pump 12. Is possible. However, during special work such as lifting the vehicle body, the operating stroke of the cylinder 14 is small, so that the power regeneration is not effective.

As described above, the boom cylinder 14 can be operated in the same manner as in the case of the two pumps both during the normal work and during the special work with one pump and while obtaining the power regeneration action.

Second embodiment (see FIG. 2) Only differences from the first embodiment will be described.

According to the circuit configuration of the first embodiment, under the condition that the external force W in the contracting direction is applied to the boom cylinder 14, the external force W is utilized to reduce the cylinder 14 while obtaining the power regeneration action. If the external force W is small, the pressure standing in the head-side oil chamber 14a is also low, so that the pump 12
There is a concern that the power to rotate will also be weakened, and a sufficient power regeneration effect will not be obtained.

Therefore, in the second embodiment, the following configuration is adopted as a measure against this point.

The directional control valve 13 is provided with a communication passage 30 for communicating the cylinder side pipe lines 20 and 21 at the neutral position a, and the cylinder rod side pipe line 21 is also connected to the pilot check valve 22 of the head side pipe line 20. Similarly, the solenoid valve 31
A pilot check valve 32 controlled by is provided.

In this configuration, when the cylinder 14 is contracted in a situation where the external force W acting on the cylinder 14 in the contracting direction is small, the controller 16 detects the above condition by the pressure signal from the pressure sensors 23, 23. A signal from 16 opens both pilot check valves 22 and 32 while keeping the directional control valve 13 in the neutral position B.

In this way, the oil chambers 14a, 1 on both sides of the cylinder are
Since 4b communicates with each other through the communication passage 30 and has the same pressure, the head side pressure is increased by applying the head side pressure to the rod side oil chamber 14b. Therefore, by sending the oil in the head-side oil chamber 14a having a high pressure to the pump 12, a sufficient power regeneration action can be obtained.

That is, the power regeneration action can be secured in a wide range of the magnitude of the external force W.

In the above embodiment, the boom cylinder circuit of the hydraulic excavator is applied as an example, but the present invention is applicable to other cylinder circuits (for example, arm cylinder circuit) of the hydraulic excavator, and also to the hydraulic excavator. It can also be applied to various hydraulic cylinder circuits of hydraulic working machines.

[0062]

As described above, according to the present invention, since one hydraulic pump drives the hydraulic cylinders in the expanding and contracting directions, the flow rate of the two pumps is the same as when two pumps are used. The problem of excess and deficiency does not occur.

Moreover, when the hydraulic cylinder is operated in the same direction as the external force, the oil in the cylinder oil chamber on the side on which the pressure from the external force acts is introduced into the pump for power regeneration, and when operating in the opposite direction. The normal cylinder operation can be performed by supplying the pump discharge oil to the oil chamber on the side where the pressure by the external force acts.

That is, it is possible to secure the power regeneration operation and the normal operation which are the same as in the case of the two-pump system while adopting the one-pump system in which the problem of excess and deficiency of the flow rate does not occur.

Further, according to the second aspect of the present invention, since the oil chambers on both sides of the hydraulic cylinder communicate with each other through the direction switching valve under the condition that the external force in the reducing direction acts on the hydraulic cylinder, the oil chambers on both sides of the cylinder are With the same pressure, the pressure in the head-side oil chamber is increased. Therefore, the power regeneration action can be secured even when the external force is small.

[Brief description of drawings]

FIG. 1 is a boom cylinder circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a boom cylinder circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a principle configuration diagram of a conventional cylinder circuit that performs a power regeneration operation.

[Explanation of symbols]

11 Electric Motor 12 Hydraulic Pump 13 Directional Switching Valve 14 Boom Cylinder (Hydraulic Cylinder) 14a Head Side Oil Chamber 14b Rod Side Oil Chamber 16 Controller 20 Head Side Pipe Line 21 Rod Side Pipe Line 23 Pressure Sensor 30 to Detect Cylinder Pressure Oil on Both Sides of Cylinder A communication passage for the directional control valve to connect the chambers

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Claims (2)

[Claims] 1. A structure in which one hydraulic pump is driven by an electric motor and the discharge oil of this hydraulic pump is supplied to a head-side oil chamber or a rod-side oil chamber of a one-rod hydraulic cylinder via a direction switching valve. Then, the direction of the external force acting on the hydraulic cylinder is detected, and (a) when operating the hydraulic cylinder in the same direction as the direction of this external force, the cylinder oil chamber on the side where the pressure by the external force acts as the power regeneration mode. (B) When the hydraulic cylinder is operated in the direction opposite to the direction of the external force, the hydraulic pump is driven by the electric motor to generate the external force. A method for controlling a hydraulic cylinder circuit, characterized in that oil is supplied to a cylinder oil chamber on the side where pressure is applied. 2. The control method for a hydraulic cylinder circuit according to claim 1, wherein when the hydraulic cylinder is contracted under a condition in which an external force in a contracting direction acts on the hydraulic cylinder, the direction changeover valve is provided in both oil chambers of the hydraulic cylinder. A method for controlling a hydraulic cylinder circuit, which is characterized in that the hydraulic cylinder circuit is communicated via a.