JPH0625562B2 - Electro-hydraulic controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrohydraulic control device, and more particularly, to an electromagnetic proportional pressure reducing valve for switching operation of a control valve or the like for controlling the operation of a hydraulic actuator in a construction machine or the like. The present invention relates to a hydraulic control device that is controlled by the above.

[Conventional technology]

In construction machines, etc., that use hydraulic pressure to operate an actuator to obtain power to achieve a specified operation, a control valve is provided in the actuator circuit to operate from a hydraulic pump. The discharge direction and discharge amount of oil are adjusted. The operation of switching the functional position of the control valve is performed by mechanically transmitting the operating force from the operating lever to the spool, or applying the pilot hydraulic pressure to the pilot chamber.

By the way, the operating speed of the actuator increases in proportion to the increase in the spool stroke of the control valve, as shown in FIG. However, the control valve does not start to move immediately after the operation lever is operated, and a dead zone is provided in the initial operation area of the operation lever.

This is for preventing the actuator from operating undesirably even if the operator touches the operation lever unintentionally or the operation lever shakes due to vibration of the vehicle body or machine, for example. That is, as shown in FIG. 4, a play corresponding to, for example, 10% of the total operation amount is provided at the beginning and the end of the operation area, and the control valve is moved by the movement of the operation lever within the remaining 80% range. It is designed to make a full stroke.

On the other hand, the control valve has a neutral holding force of the spool that is determined in consideration of the flow force of the hydraulic fluid flowing through the valve and resistance due to other factors.
The initial force Fo shown in the figure is the minimum operation force required to move the spool of the control valve.
Therefore, when the operating lever is operated beyond the dead zone and the operating force Fo which is larger than the initial force Fo acts, it overcomes the spring built in the control valve and the spool of the control valve starts to move.

When the opening degree of the control valve increases and the amount of hydraulic oil passing through the valve increases, the operation force for moving the spool also increases. The size of the initial force Fo and the width of the dead zones at the start end and the end are different depending on the operating environment and conditions of the machine or device in which the actuator is mounted, and are selected in advance at the stage of hydraulic circuit design.

As can be seen from the above description, the actual stroke of the control valve with respect to the operation amount of the operation lever is performed in the operation area excluding the two dead areas at the operation start end and the operation end of the operation lever. The operation to change the functional position of the control valve is performed in advance even if it is a mechanical type that directly transmits the operation amount of the lever as touched above or a hydraulic type that converts it to pilot hydraulic pressure and applies that pressure to the pilot chamber. It is performed in the lever operation range of, for example, 80 to 90% excluding the specified dead zone. That is, it is possible to obtain a high controllability in which the spool of the control valve can be gently displaced by using the region between them to finely adjust the operation of the actuator.

[Problems to be Solved by the Invention]

For mechanical control in which the manual operating force from the operating lever is applied directly to the control valve spool to operate the control valve, a large actuator with a large amount of hydraulic oil is used. When actuated, a large operating force is required for the control valve, and the burden on the operator becomes extremely large. In the hydraulic system in which the operation amount of the lever is converted into the hydraulic pressure and the pilot pressure is applied to the pilot chamber, since the amplification by the hydraulic pressure is possible, it is possible to avoid an increase in the operating force applied to the operating lever. However, the viscosity of hydraulic oil changes depending on the ambient temperature, and it may be difficult to thicken the pipe or it may have to be spread for a long time.Therefore, for example, in a construction engine operating in a cold region, There is a problem that the flow of hydraulic oil becomes poor and the response speed of the actuator is significantly reduced.

By the way, these days, it is not affected by temperature and piping, and it can be easily controlled by control signals, etc., and if necessary, each control signal can be transmitted to others to adjust the interlocking operation in the hydraulic system. It may be desired to enable Therefore, a control valve such as an electromagnetic pressure reducing valve that operates by receiving an electric signal is employed, and the pilot pressure is applied to the pilot chamber of the control valve via the control valve.

The current input to the electromagnetic pressure reducing valve is proportional to the lever operating angle of the operating lever. However, the relationship between the input current to the electromagnetic pressure reducing valve and the pilot pressure acting on the pilot chamber of the control valve via the electromagnetic pressure reducing valve is as shown in FIG. 6, which is necessary to start moving the spool of the control valve. A large input current A1 to obtain a large force Fa,
That is, a large lever operation angle is required.

Therefore, the operation lever is
Even if the operation exceeds 10% of play, the operation force Fa at which the spool of the control valve starts to move cannot be obtained, and as a result, the operation force equal to or greater than the force Fa that enables the operation of the control valve can be obtained. The range is narrow, about 1/2 to 1/3 of all lever operation angles. This causes a problem that the spool movement of the control valve is greatly changed by the lever operation, making it difficult to finely adjust the flow rate, resulting in poor controllability.

The present invention has been made to solve the above problems,
It is possible to easily realize the interlocking operation in the hydraulic system by using the electric signal without increasing the operating force due to the enlargement of the actuator, and without being affected by the temperature and piping. Therefore, it is an object of the present invention to provide an electro-hydraulic control device capable of improving controllability by widening the control range of the control valve to the same level as in the case of mechanical type or hydraulic type.

[Means for Solving the Problems]

INDUSTRIAL APPLICABILITY The present invention is applied to a hydraulic control device that switches control valves by applying output pressure from an electromagnetic proportional pressure reducing valve.

The feature is that, referring to FIG. 1, it acts on the spool of the control valve 3 in addition to the pilot chambers 3A, 3B of the control valve 3 on which the output pressure from the electromagnetic proportional pressure reducing valves 5A, 5B acts. Sub-pilot room 3a, 3b
Is attached to control valve 3. A switching valve 8 for opening / closing operation is installed to apply pressure to the sub-pilot chambers 3a and 3b. This switching valve 8 operates when the operating lever 11 is operated beyond the dead zone, and the solenoid proportional pressure reducing valve 5
The pilot chamber 3a or 3b of the control valve 3 on which the output pressure from A, 5B acts is connected to the electromagnetic proportional pressure reducing valve 5A, 5B.
B is connected to a hydraulic pump 7 that supplies pilot hydraulic pressure. Then, the assisting pressure is introduced to the sub-pilot chamber 3a or 3b.

[Action]

An operation force that exceeds the initial force is required to operate the operation lever 11, but the operation lever 11 is in the dead zone up to a certain operation angle. During that time, a current according to the operation angle of the operating lever 11 is input to the electromagnetic proportional pressure reducing valve 5A or 5B, but the value is extremely small, and the electromagnetic proportional pressure reducing valve 5A or 5B is provided in the pilot chamber 3A or 3B of the control valve 3.
Even if pilot pressure is applied via the spool, the spool does not move at the low pressure.

When the operating angle of the operating lever 11 increases and exceeds the dead zone, the switching valve 8 is switched, and the pilot chamber 3A or 3 on which the output pressure from the electromagnetic proportional pressure reducing valve 5A or 5B acts.
The sub-pilot chamber 3a or 3b on the same side as B is communicated with the hydraulic pump 7 that supplies pilot hydraulic pressure to the electromagnetic proportional pressure reducing valves 5A and 5B, and is connected to the sub-pilot chamber 3a or 3b.
Helping pressure is introduced into. As a result, the electromagnetic proportional pressure reducing valve 5
The pilot pressure via A or 5B becomes a predetermined pressure, and the superimposed pilot pressure generates an operating force for moving the spool of the control valve 3.

The spool moves to a position that balances the force, hydraulic oil is supplied to the actuator 1 via the control valve 3, and the solenoid pressure reducing valve 5A that does not start operation unless pilot pressure from the switching valve 8 acts. Alternatively, the actuator 1 operates even at the input current value of 5B.

〔The invention's effect〕

According to the present invention, the sub-pilot chamber is provided in the control valve in addition to the pilot chamber in which the output pressure from the electromagnetic proportional pressure reducing valve acts, and the sub-pilot chamber is opened and closed via the switching valve that opens and closes according to the operating angle of the operating lever. Since the pressure is applied to the control valve, pilot pressure is assisted via the electromagnetic proportional pressure reducing valve, which has a poor start-up, and the spool stroke of the control valve is as wide as the mechanical or hydraulic control valve control. Adjusted in
High controllability of the control valve can be secured.
Of course, there is no increase in the operating force due to the size increase of the actuator, and there is no influence of temperature or piping. Moreover, various interlocking operations in the hydraulic system can be easily realized by using the electric signal.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples thereof.

FIG. 1 is a hydraulic circuit of a construction machine or the like to which an electrohydraulic control device is applied, in which a hydraulic motor 1 as an actuator is driven by supplying and discharging hydraulic oil from a hydraulic pump 2. There is a control valve 3 for controlling the rotation direction and rotation speed of the hydraulic motor 1, and by switching from the neutral state shown in the figure to the functional position 3M or 3N,
The direction of supply and discharge of hydraulic oil can be changed.

The control valve 3 has pilot chambers 3A and 3B on which pilot pressure acts, and the pilot pressure acting on one pilot chamber 3A or 3B causes the spool to move against the spring 4a or 4b. Therefore, the electromagnetic proportional pressure reducing valves 5A and 5B for applying the pilot pressure are provided in the respective pilot chambers 3.
It is installed corresponding to A and 3B.

The magnitude of the pilot pressure by the electromagnetic proportional pressure reducing valves 5A, 5B is determined by the excitability of the solenoids 6a, 6b. The current supplied for that purpose is the operation of the operation lever 11 operated to operate the hydraulic motor 1. Proportional to the angle. The electromagnetic proportional pressure reducing valves 5A and 5B are connected to a hydraulic pump 7 that supplies pilot hydraulic pressure.

In this way, in the hydraulic control device in which the control valve 3 is switched by applying the output pressure from the electromagnetic proportional pressure reducing valves 5A and 5B,
Pilot chambers 3A, 3 on which output pressure from A, 5B acts
Apart from B, sub-pilot chambers 3a and 3b that act on the spool of the control valve 3 are provided. Since the sub-pilot chambers 3a and 3b serve to assist the pilot pressure acting on the pilot chambers 3A and 3B,
The operating area of the pilot pressure in the sub-pilot chambers 3a and 3b is set to be smaller than the operating area of the pilot pressure through the electromagnetic proportional pressure reducing valves 5A and 5B.

A switching valve 8 that opens and closes to apply pressure to the sub-pilot chambers 3a and 3b is installed, and is interposed between the hydraulic pump 7 and the two sub-pilot chambers 3a and 3b. The switching valve 8 has solenoids 8a and 8b that are excited in accordance with the operating angle of the operating lever 11, and when the operating lever 11 exceeds a preset dead zone from the neutral position, a limit switch is actuated. The pilot pressure can be applied to the pilot chamber 3a or 3b. Relief valves 9 and 10 are provided in the circuit that operates the hydraulic motor 1 and the circuit that applies the pilot pressure, respectively, and is regulated so that a pressure exceeding a predetermined range is not generated.

In the electro-hydraulic control device having such a configuration, when the operating lever 11 exceeds the dead zone, the sub pilot on the same side as the pilot chamber 3A or 3B of the control valve 3 on which the output pressure from the electromagnetic proportional pressure reducing valve 5A or 5B acts. Room 3
The switching valve 8 is operated so that a or 3b communicates with the hydraulic pump 7 and guides the assisting pressure to the sub-pilot chamber 3a or 3b. The force for moving the spool of the control valve 3 by the pilot pressure from the electromagnetic proportional pressure reducing valves 5A and 5B tends to gradually rise as shown by the solid line in FIG. 2 as described in FIG. 6 of the prior art. However, due to the above-mentioned assisting pressure, it is considered to have been raised as shown by a broken line to be described later.

Explaining in order, the operation lever 11 is in the dead zone up to a certain angle at the beginning of operation, and the electromagnetic proportional pressure reducing valve 5
The current value input to A and 5B is extremely low as in the K portion of FIG. Therefore, even if the pilot pressure via the electromagnetic proportional pressure reducing valve 5A or 5B acts on the pilot chamber 3A or 3B of the control valve 3, the pressure is also extremely low,
The spool of the control valve 3 does not move.

When the operating angle of the operating lever 11 becomes large and reaches the point R before the dead zone, the operating lever 11 turns on the limit switch, and the switching valve 8 moves to the functional position 8M.
Then, a predetermined amount of pilot pressure is applied to the sub-pilot chamber 3a on the same side as the pilot chamber 3A on which the output pressure of the electromagnetic proportional pressure reducing valve 5A acts. As a result, the pilot pressure is weighted, and a pressure corresponding to a force slightly smaller than the operating force Fa for moving the spool of the control valve 3 acts.

When the operating lever 11 reaches the point S that exceeds the dead zone, a force Fa that moves the spool acts on the control valve 3,
The control valve 3 has a predetermined opening. The hydraulic oil is supplied to the hydraulic motor 1 via the control valve 3, and the switching valve 8
If the pilot pressure from 1 does not act, the hydraulic motor 1 that does not start operating up to point T in the figure operates. The pilot pressure applied to the sub-pilot chamber 3a is gradually reduced as the operating angle of the operating lever 11 increases, and the spool of the control valve 3 moves over the entire stroke at point U when the operating lever 11 is operated to a predetermined angle. To complete.

By the way, when the hydraulic motor 1 is rotated in the reverse direction, the operation lever 11 is tilted in the reverse direction, and the functional position of the switching valve 8 is set to 8N. The switching valve 8 is an electromagnetic valve as described above,
It is electrically easy to change the pilot pressure applied to the sub-pilot chamber 3a or 3b according to the operation angle of the operation lever 11.

By the way, as described above, the switching valve 8 guides the assisting pressure to the sub-pilot chamber 3a or 3b, and the pilot pressure from the electromagnetic proportional pressure reducing valves 5A and 5B superimposes the force to move the spool of the control valve 3 for operation. I am trying to increase my strength. However, since the operating force acting on the control valve 3 for raising the height as it is increases uniformly, the increase of the pilot pressure acting on the pilot chamber 3A or 3B from the electromagnetic proportional pressure reducing valve 5A or 5B causes the operating angle of the operating lever 11 to increase. It goes without saying that the adjustment is changed so as to gradually decrease with the increase, that is, as shown by the broken line in FIG.

In other words, even if the assisting pressure is uniformly introduced into the sub-pilot chamber 3a or 3b, at the time when the input current of the electromagnetic proportional pressure reducing valve becomes U, the operating force increases with respect to the current so as to cancel the padding amount. The characteristic of the electromagnetic proportional pressure reducing valve 5 may be changed so that Naturally, the characteristic of the electromagnetic proportional pressure reducing valve 5 is selected according to the characteristic of the control valve 3, and it goes without saying that such characteristic change does not cause any difficulty at the design stage.

In the above operation, the controllable range of the operating lever can be set to, for example, 80% or more of the total operating angle of the operating lever. When the control valve is operated only by the pilot pressure via the electromagnetic pressure reducing valve, the control range is narrow (from point T to point U in Fig. 2), but it is the same as in the mechanical or hydraulic type. Thus, the hydraulic system can be made wider, and the operation of the actuator can be finely adjusted to have high controllability.

[Brief description of drawings]

FIG. 1 is an example of a hydraulic circuit in which the electrohydraulic control device of the present invention is adopted, FIG. 2 is a graph showing the relationship between the operating angle of the operating lever and the control valve operating force, and FIG. 3 is the spool stroke of the control valve. 4 is a graph showing the operating speed of the actuator with respect to the control valve, FIG. 4 is a graph showing the spool stroke amount of the control valve with respect to the lever operation amount, FIG. 5 is a graph showing the operation force of the control valve with respect to the lever operation amount, and FIG. It is a graph which shows the operating force of the control valve with respect to the input current of a valve. DESCRIPTION OF SYMBOLS 1 ... Hydraulic motor (actuator), 3 ... Control valve, 3A, 3B ... Pilot chamber, 3a, 3b ... Sub-pilot chamber, 5A, 5B ... Electromagnetic (proportional) pressure reducing valve, 7 ... Hydraulic pump, 8 ... Switching valve, 11 … Operating lever.

Claims (1)

[Claims] 1. A hydraulic control device in which a control valve is switched by applying an output pressure from an electromagnetic proportional pressure reducing valve, in addition to a pilot chamber of the control valve on which the output pressure from the electromagnetic proportional pressure reducing valve acts. , A sub-pilot chamber that acts on the spool of the control valve is attached to the control valve, and a switching valve that opens and closes to apply pressure to the sub-pilot chamber is installed. The switching valve operates when the operating lever exceeds the dead zone. And a sub-pilot chamber on the same side as the pilot chamber of the control valve on which the output pressure from the electromagnetic proportional pressure reducing valve acts, is connected to a hydraulic pump that supplies pilot hydraulic pressure to the electromagnetic proportional pressure reducing valve. An electrohydraulic control device characterized in that an assisting pressure is introduced into the sub-pilot chamber.