JP2002349505A - Hydraulic actuator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic actuator circuit easy to operate in the fine operation range and allowing power regeneration effectively. SOLUTION: The hydraulic actuator circuit includes a boom cylinder circuit of motor driving type to drive hydraulic pumps 14 and 15 using an electric motor 13, in which a control valve 12 is installed in a cylinder elongation side pipeline 10. The control valve 12 is furnished with a lock valve 18 to hold the boom cylinder 7 at a standstill and a flow regulating valve 19, and in the contraction stroke of cylinder, the condition A<B should be met in the fine operation range, where A represents the rate of flow of the oil discharged from the boom cylinder 7 passing through the control valve 12 and B represents the rate of flow sucked into the hydraulic pumps, and thereby the cylinder speed is controlled by the control valve 12, and in the operating range beyond it, A>B should be established and the cylinder speed is controlled with the pump rotating speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic actuator circuit in which a hydraulic pump is driven by an electric motor, and oil discharged from a hydraulic actuator is returned to the hydraulic pump and regenerated.

[0002]

2. Description of the Related Art Recently, in construction machines such as hydraulic excavators and cranes, an electric motor drive system in which a hydraulic pump, which is a hydraulic source of a hydraulic actuator, is driven by an electric motor has been adopted.

In this motor drive system, the operation of an operating means (lever or pedal; hereinafter, the case of a lever) causes the motor to rotate at a rotational speed corresponding to the lever operation amount, thereby controlling the pump flow rate. In this configuration, the pump speed is used to control the actuator speed.

In the electric motor drive system, oil from an actuator is sucked into a hydraulic pump to perform a motor function, thereby generating a regenerative electric power in the electric motor and storing a power in a battery or the like. In particular, in the case of an actuator such as a boom cylinder of a hydraulic shovel, in which a load in one direction (reduction direction) is always applied by the weight of the excavation attachment plus the weight of earth and sand, the effect of power regeneration can be obtained by using negative pressure for the motor action. It is large and contributes to energy saving.

[0005]

However, in such an electric motor driving system, the actuator speed is controlled by the number of revolutions of the electric motor (pump). Therefore, depending on conditions, a low speed region (a fine operation region where the lever operation amount is small). However, there is a problem that speed control is difficult and operability is deteriorated.

For example, in the case of the above-described boom cylinder, the load pressure always acts on the cylinder head side oil chamber in almost all working postures. Accurate speed control becomes difficult due to the influence of leakage and the like.

It is conceivable to adopt a configuration in which a flow control valve is provided in a pipe connecting the actuator and the pump as in a conventional engine drive system, and the speed of the actuator is controlled by controlling the opening of the flow control valve. But,
In this case, since the pressure loss at the flow control valve is large, there is a problem that the power regeneration efficiency is reduced.

Accordingly, the present invention is to provide a hydraulic actuator circuit having good operability in a fine operation range and capable of efficiently performing power regeneration.

[0009]

According to a first aspect of the present invention, there is provided a hydraulic actuator, a hydraulic pump for driving the hydraulic actuator, an electric motor for driving the hydraulic pump, and a command of the number of rotations and the direction of rotation for the electric motor. Operating means for issuing, and control means for controlling the number of rotations and the rotation direction of the electric motor based on a command signal from the operating means, and
In a hydraulic actuator circuit configured to perform power regeneration by sucking oil from the hydraulic actuator into the hydraulic pump, a control valve controlled by the control means is provided in a pipe connecting the hydraulic pump and the hydraulic actuator. Assuming that the flow rate of the oil discharged from the hydraulic actuator through the control valve is A, and the flow rate of the oil sucked into the hydraulic pump is B, the control means determines that the operation amount of the operation means is smaller than a predetermined value. In the operating range, the actuator speed is controlled by the control valve as A <B, and in the operating range beyond this fine operating range, the actuator speed is controlled by the rotational speed of the hydraulic pump as A> B in the operating range. It is configured to control the rotation speed of the electric motor and the control valve.

According to a second aspect of the present invention, in the configuration of the first aspect, the control means includes:
The control valve passage flow rate A and the pump suction flow rate B are configured to increase continuously as the operation amount of the operation means increases.

According to a third aspect of the present invention, in the configuration of the first or second aspect, the control valve is provided in (a) a load side pipe line on which load pressure acts, of the two side pipe lines connecting the hydraulic actuator and the hydraulic pump. (B) When the hydraulic actuator is stopped, the load side pipe is closed to maintain the load pressure, and the lock valve is fully opened in an operation range exceeding the fine operation range.

According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, a hydraulic pump is connected to both side oil chambers of a one-side rod cylinder as a hydraulic actuator, and hydraulic pressure is supplied by oil from one hydraulic pump. This is configured to drive the actuator and, at the same time, suck oil from the hydraulic actuator into the other hydraulic pump.

According to the above configuration, in the fine operation range, the flow rate A that exits the actuator and passes through the control valve is smaller than the flow rate B that is sucked into the pump. In this state, the actuator speed is determined by the opening of the control valve, and the speed control is performed by the control valve. Therefore, good operability in which the actuator moves as operated can be obtained.

On the other hand, in the operation range beyond the fine operation range, A> B is reversed, and the actuator speed control based on the rotation speed of the pump is performed in a state where pressure is generated between the control valve and the pump. Done. That is, the power regeneration operation is performed in a state where the pressure loss in the control valve is small.

In this manner, both good fine operability and efficient power regeneration can be achieved.

The effect of this point is particularly remarkable when the present invention is applied to an actuator (for example, a boom cylinder of a hydraulic shovel) in which a load always acts in one direction.

In this case, according to the configuration of claim 2, the control valve passage flow rate A and the pump suction flow rate B continuously increase in the fine operation range and the operation range beyond the fine control range in accordance with the operation amount of the operation means. Therefore, the switching of the speed control is performed smoothly without a shock.

According to the third aspect of the present invention, in the case where the actuator which always acts in one direction as described above is targeted, the lock valve locks the actuator against a load to a stop state. Can be. That is, the control valve that performs speed control in the fine operation range also serves as the lock valve, and the circuit configuration can be simplified.

According to the fourth aspect of the present invention, a single rod type cylinder is used as the hydraulic actuator, and separate pumps are connected to the oil chambers on both sides in order to eliminate a speed difference due to a difference in cross-sectional area between the oil chambers on both sides of the cylinder. In the circuit described above, the above-described effects can be obtained.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

In this embodiment, a boom cylinder circuit of a hydraulic shovel is taken as an example.

As shown in FIG. 4, the hydraulic excavator has an upper revolving unit 2 mounted on a lower traveling unit 1 and an excavation attachment 3 attached to the upper revolving unit 2.

The excavation attachment 3 comprises an arm 5 attached to the tip of a boom 4 that can be raised and lowered, and a bucket 6 attached to the tip of the arm 5.
The bucket 6 is driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, respectively.

In this excavation attachment 3, in the boom cylinder 7, a force in the reduction direction shown by the arrow in FIG. ) Is affected by the load pressure.

Therefore, in the boom cylinder circuit,
The extension-side pipeline (load-side pipeline) so that the boom cylinder 7 does not naturally extend due to the load pressure when the cylinder is stopped.
It is customary that a lock valve is provided on the vehicle.

In the boom cylinder circuit according to this embodiment shown in FIGS. 1 and 2, the control valve 12 having a lock function is provided on the extension-side pipe 10 of the extension-side and reduction-side pipes 10, 11 of the boom cylinder 7. And the control valve 12
The lock function when the cylinder is stopped by
As described later, the speed of the boom cylinder 7 is controlled in the fine operation range.

The boom cylinder circuit will be described in detail.

FIG. 1 shows a principle configuration of a boom cylinder circuit, and FIG. 2 shows a specific configuration.

First, the principle configuration will be described with reference to FIG. 1. Reference numeral 13 denotes an electric motor which rotates forward and backward using a generator or the like (not shown) as a power source. The electric motor 13 drives first and second hydraulic pumps 14 and 15. .

The first pump 14 is connected to the head-side oil chamber 7a of the boom cylinder 7 as a cylinder extension pump, and the second pump 15 is connected to the rod-side oil chamber 7b of the cylinder 7 as a cylinder reduction pump. Act like so.

(I) When the cylinder is extended The first pump 14 is driven by the forward rotation of the electric motor 13 to supply oil to the head side oil chamber 7a of the boom cylinder 7,
The cylinder 7 extends. At this time, the oil discharged from the rod-side oil chamber 7b is sucked into the second pump 15 to perform a motor function, and is returned to the tank T.

(Ii) When the cylinder is reduced The second pump 15 is driven by the reverse rotation of the electric motor 13 to supply oil to the rod-side oil chamber 7b of the boom cylinder 7,
The cylinder operates to contract. At this time, the head side oil chamber 7
The oil discharged from a is sucked into the first pump 14 to perform a motor function, and is returned to the tank T.

As described above, when the cylinder is expanded and contracted, both pumps 1
When one of the motors 4 and 15 functions as a motor, regenerative electric power is generated in the electric motor 13, and the regenerative electric power is stored in a battery (not shown). In particular, since the load pressure always acts on the cylinder head 7a side as described above, the power regeneration efficiency when the boom is lowered (when the cylinder is contracted) is improved.

Here, the boom cylinder 7 is a one-side rod type, and the cross-sectional area of the rod-side oil chamber 7b is equal to the head-side oil chamber 7a.
Therefore, even if the supply flow rate is the same, there occurs a speed difference between the expansion operation and the reduction operation, which causes a problem that the bucket trajectory cannot be accurately controlled.

Therefore, in this embodiment, the pump volumes of the two pumps 14 and 15 are set so that the above-mentioned speed difference does not occur (the discharge amount differs according to the sectional area ratio).

More specifically, the pump volumes q1 and q2 of the two pumps 14 and 15 are given by the relationship with the cross-sectional areas Ah and Ar of the head-side and rod-side oil chambers 7a and 7b of the cylinder 7, q2 = q1 × (Ar / Ah).

Next, a specific configuration will be described with reference to FIG.

The rotation speed of the electric motor 13 is changed from a low speed (for example, 100 rpm) to a high speed (for example, 3 rpm) by a rotation speed command signal from a controller 17 as a control means based on the operation of an operation lever (or an operation pedal) 16 as an operation means. , 000 rpm). Reference numeral 13a denotes a motor controller for setting the motor speed based on a command from the controller 17.

Here, the operating lever 16 means a lever composed of the lever itself and a converter for converting the lever operation amount into an electric signal.

The control valve 12 includes a lock valve 18 for stopping and holding the cylinder 7 and a flow regulating valve 19 for controlling the lock valve 18 and controlling the speed of the cylinder 7 in a fine operation range.
And a relief valve 20 with a check valve.

The lock valve 18 has an opening-side pressure chamber 22 on the left side in the figure for pressurizing the valve body 21 in the valve opening direction and a closing-side pressure chamber 23 on the right side in the figure for pressurizing the valve body 21 in the valve closing direction. The closing side pressure chamber 23 is provided with a spring 24 for adding a spring force to the closing side pressure.

The flow control valve 19 is provided with a pilot pressure from a pilot pump 26 driven by a pilot pump motor 25 and a controller 1 based on lever operation.
7 is operated as an electric / hydraulic pilot type switching valve operated in response to an electric command signal from the control unit 7 in accordance with the lever operation amount. It switches between the positions c of 3.

The control valve 12 includes a lock valve 18.
The main passage 27 connecting the opening-side pressure chamber 22 of the boom cylinder 7 and the head-side oil chamber 7a of the boom cylinder 7, and the head-side oil chamber 7a and the extension-side pipe 10 bypassing the lock valve 18 and via the flow control valve 19
, And the pressure chambers 22 on both sides of the lock valve 18.
A communication path 29 connecting the flow path 23 through a flow control valve 19;
A tank passage 30 leading to the tank T is provided.

The following operations are performed at the respective positions a, b, and c of the flow control valve 19.

First position a The pressure chambers 22 and 23 on both sides of the lock valve 18 communicate with each other through a communication passage 29 to have the same pressure. In this state, a closing-side spring force is applied to the valve body 21, so that the valve body 21 The lock valve 18 is closed by being pushed to the closing side.

In this state, the main passage 27 is closed, and at this time, the sub passage 28 is also closed by the flow control valve 19, so that the cylinder 7 is stopped and held (natural reduction is prevented).

Since the pressure chambers 22, 23 on both sides at the second position b are still in communication with each other by the communication passage 29, the lock valve 18 remains closed.

On the other hand, the sub-passage 28 opens at an opening corresponding to the lever operation amount, and the oil in the cylinder head side oil chamber 7a flows through the sub-passage 28 to the reduction side pipe 10 while being subjected to the throttle action.

Third position c Since the closing-side pressure chamber 23 communicates with the tank passage 30, when the pressure in the extension-side conduit 10 exceeds the spring force of the spring 24, the lock valve 18 is fully opened and the cylinder head side is opened. The oil in the oil chamber 7a flows through the main passage 27 (the lock valve 18) to the extension-side conduit 10 with almost no throttle action.

In FIG. 2, reference numerals 31 and 32 are discharge valves which are operated by a signal from the controller 17 based on the lever operation to return the excess flow during cylinder operation to the tank T, while the discharge valves 33 and 34 are in a flow shortage state. Sometimes pipe 1 from tank T
A check valve for replenishing oil to 0 and 11 is provided, a check valve 35 and 36 are provided for sucking the tank oil into both pumps 14 and 15 as necessary, and a main relief valve 37 is provided.

Next, the operation of the entire boom cylinder circuit will be described.

The lever 16 is lowered with the boom (cylinder reduction).
When it is operated to the side, the electric motor 13 rotates based on the command signal from the controller 17, the discharge oil from the second pump 15 is supplied to the cylinder rod side oil chamber 7b, and the cylinder 7 starts the reducing operation.

In this case, the rotation speed of the electric motor 13 and the state of the control valve 12 (the lock valve 18 and the flow regulating valve 19) change according to a command signal from the controller 17 in accordance with the lever operation amount, and the cylinder head side oil chamber 7a The oil that has flowed out is sucked into the first pump 14 and returned to the tank T while being subjected to a flow control action according to this state change.

At this time, the cylinder speed is controlled by the flow rate control function, and the power regeneration function is performed by the first pump 14 performing the motor function.

FIG. 3 shows the control contents of the controller 17 based on the lever operation amount when the cylinder is contracted, that is, FIG.
The relationship between the lever operation amount, the flow rate A passing through the control valve 12 (hereinafter referred to as control valve passing rate) A, and the flow rate sucked into the first pump 14 (hereinafter referred to as pump suction flow rate) B is shown.

According to this control, in the fine operation range where the lever operation amount is small (the range of "10" or less in the numerical value of the horizontal axis in FIG. 3), the lock valve 18 is closed and the flow control valve 19 is set in the second position.
Is set at position b.

In this state, A <B, and the opening speed (lever operation amount) of the flow control valve 19 at the second position b determines the reduction speed of the boom cylinder 7. That is, speed control by the control valve 12 is performed.

Both the control valve passage flow rate A and the pump suction flow rate B continuously increase as the lever operation amount increases, and when the lever operation amount exceeds the fine operation range, as shown in FIG. The relationship between the passing flow rate A and the pump suction flow rate B is A> B, contrary to the fine operation range.

In this state, the first pump 14 does not catch up with the suction operation, and a pressure is generated between the control valve 12 and the first pump 14 (extension side pipe 10). The cylinder speed is controlled by the number of revolutions of ()).

When the lever operation amount reaches a certain value,
The flow control valve 19 is switched to the third position c and the lock valve 1
8 is fully opened. At this time, pressure has already been generated in the first pump 14 as described above, and control is performed by the pump rotation speed. However, there is a smooth transition from the control valve 12 to the pump rotation speed.

As described above, when the boom cylinder 7 is contracted, the cylinder speed is controlled by the throttle action of the control valve 12 in the fine operation range, and the first pump 14
Control in the fine operation range, and the control valve 1 in the operation range beyond this
2, the power regeneration action can be performed efficiently by reducing the pressure loss.

On the other hand, boom lowering (boom cylinder extension)
Sometimes, the lock valve 18 of the control valve 12 is fully opened and the first
When the oil discharged from the pump 14 is supplied to the cylinder head side oil chamber 7a via the lock valve 18, the cylinder 7 is extended at a speed corresponding to the lever operation amount.

At this time, the oil that has flowed out of the cylinder rod side oil chamber 7 b is sucked into the second pump 15 via the reduction side pipe 11 and returned to the tank T.

When the cylinder is extended, unlike the contraction, the cylinder 7 is operated by the pressure of the first pump 14, so that the speed is controlled by the motor speed (pump speed) in the entire operation range including the fine operation range. .

However, in the small flow rate state in the fine operation range, the flow rate is liable to change under the influence of the pressure change. Therefore, in this embodiment, the controller 17 is controlled so as to obtain a stable pump flow rate in the fine operation range. The pump rotation speed is set to be higher than the lever operation amount by the control, and the difference (excess) between the actual flow rate and the required cylinder flow rate is set as the discharge valve 3.
The bleed-off at 1 and 32 is adopted.

In the above embodiment, the boom cylinder 7 is driven by separate pumps 14 and 15 when the boom cylinder 7 is extended and contracted, as an example suitable for a one-sided rod type cylinder. It may be configured to be driven by one pump (a two-way discharge pump whose discharge direction changes in accordance with the rotation direction).

The present invention is particularly suitable for a circuit in which a load pressure always acts on the actuator in one direction, such as the boom cylinder circuit described in the above embodiment. The present invention can be widely applied to actuator circuits (cylinder circuits, hydraulic motor circuits) in which speed control is difficult.

Further, the control valve 12 may be provided in the conduit on both sides of the actuator as required.

Further, in the above embodiment, the lock valve 18
Although the case where the control valve 12 provided with is used is exemplified, the lock valve 18 for holding the actuator and the control valve for speed control in the fine operation range may be separately provided as independent valves.

[0070]

As described above, according to the present invention, a control valve is provided between a hydraulic actuator and a pump in a motor-driven hydraulic actuator circuit, and a flow rate of oil discharged from the actuator passes through the control valve. Is A, and the flow rate sucked into the pump is B, and in the fine operation range, A <
Controlling the actuator speed by a control valve as B,
In an operation range exceeding this range, A> B is set so that the actuator speed is controlled by the pump rotation speed, so that both good fine operability and efficient power regeneration can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a principle configuration of a boom cylinder circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a specific configuration of the circuit.

FIG. 3 is a diagram showing a relationship between a lever operation amount controlled by a controller, a control valve passage flow rate, and a pump suction flow rate.

FIG. 4 is a schematic side view of a hydraulic shovel to which the boom cylinder circuit is applied.

[Explanation of symbols]

 Reference Signs List 7 boom cylinder (hydraulic actuator) 7a head-side oil chamber of boom cylinder 7b rod-side oil chamber 13 motor 14 first hydraulic pump 15 second hydraulic pump 10 extension side pipeline 11 reduction side pipeline 12 control valve 18 control valve Constructed lock valve 19 Same flow control valve 16 Lever as operating means 17 Controller as control means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuki Egawa 8-7-24 Tsuji, Saitama-shi, Saitama F-term in the Urawa Plant of Kayaba Industry Co., Ltd. F-term (reference) 2D003 AA01 AB03 AB05 BA01 BA05 BB02 CA04 CA10 DA03 DA04 3H089 AA44 BB04 CC01 DA02 DA07 DA14 DB12 DB32 DB33 DB47 DB49 FF05 GG02 JJ02

Claims (4)

[Claims] 1. A hydraulic actuator, a hydraulic pump for driving the hydraulic actuator, an electric motor for driving the hydraulic pump, operating means for issuing a command of the number of rotations and a rotating direction to the electric motor, and a command from the operating means. A hydraulic actuator circuit comprising control means for controlling the number of rotations and the rotation direction of the electric motor based on the signal, and configured to perform power regeneration by sucking oil coming out of the hydraulic actuator into the hydraulic pump. A control valve controlled by the control means is provided in a line connecting the hydraulic pump and the hydraulic actuator, and the flow rate of the oil discharged from the hydraulic actuator passing through the control valve is A,
Assuming that the flow rate sucked into the hydraulic pump is B, the control means controls the actuator speed by the control valve as A <B in a fine operation range where the operation amount of the operation means is equal to or less than a preset value. In the operation range exceeding the fine operation range, the rotation speed of the electric motor and the control valve are controlled such that A> B and the speed of the actuator is controlled by the rotation speed of the hydraulic pump. Hydraulic actuator circuit. 2. The hydraulic actuator circuit according to claim 1, wherein the control means includes a control valve passing flow rate A and a pump suction flow rate B in a fine operation range and an operation range beyond the fine operation range in accordance with an increase in the operation amount of the operation means. The hydraulic actuator circuit is configured to increase continuously. 3. The hydraulic actuator circuit according to claim 1, wherein the control valve is provided in: (a) a load-side pipe on which a load pressure acts, of the two-side pipe connecting the hydraulic actuator and the hydraulic pump; (B) A hydraulic actuator circuit having a lock valve that closes a load-side pipe line when a hydraulic actuator is stopped to maintain a load pressure, and that is fully opened in an operation range exceeding a fine operation range. 4. A hydraulic pump is connected to both oil chambers of a one-side rod cylinder as a hydraulic actuator,
4. The hydraulic pump according to claim 1, wherein the hydraulic actuator is driven by oil from one of the hydraulic pumps, and the oil from the hydraulic actuator is sucked into the other hydraulic pump at the same time. Hydraulic actuator circuit.