Patent Application
20180017087
The present invention relates to the technical field of a hydraulic actuator control circuit for controlling supply and discharge of oil to and from a hydraulic actuator provided in a construction machine such as an excavator.
In general, various hydraulic actuators are provided in construction machines such as excavators. As a control circuit for controlling supply and discharge of oil to and from such a hydraulic actuator, a control circuit has been known which is configured to simultaneously perform, using one spool valve, directional control that switches between the direction of supply of hydraulic oil to the hydraulic actuator and the direction of discharge of hydraulic oil from the hydraulic actuator, meter-in control that controls a supply flow rate from a hydraulic pump to the hydraulic actuator, and meter-out control that controls a discharge flow rate from the hydraulic actuator to an oil tank. However, when the meter-in control and the meter-out control are thus performed using one spool valve, a relation between a meter-in opening area and a meter-out opening area with respect to a moving position of the spool valve is uniquely determined. This causes a problem in that the relation between the meter-in and the meter-out cannot be changed in accordance with the contents of work and an operator.
Thus, a technique has been known in which the control of supply and discharge of oil to and from the hydraulic actuator is performed by a bridge circuit formed using four metering valves including a head-side meter-in valve and a rod-side meter-in valve (a head-end supply valve and a rod-end supply valve) that control supply flow rates from the hydraulic pump to a head-side oil chamber of a hydraulic cylinder and to a rod-side oil chamber of the hydraulic cylinder, respectively, and a head-side meter-out valve and a rod-side meter-out valve (a head-end drain valve and a rod-end drain valve) that control discharge flow rates from the head-side oil chamber and from the rod-side oil chamber to the oil tank, respectively (see, for example, PTL 1). In this technique, the four metering valves are individually actuated based on commands from a controller. Thus, the relation between the meter-in and the meter-out can be easily changed in accordance with the contents of work and the operator.
Moreover, the bridge circuit using the four metering valves enables recycling such that discharged oil from one of the oil chambers of the hydraulic actuator is supplied to the other oil chamber. When the recycling is performed, both the head-side and rod-side meter-in valves are opened to merge the discharged oil from one of the oil chambers with pump discharge oil via one of the meter-in valves, and the merged hydraulic oil is then supplied to the other oil chamber via the other mere-in valve.
On the other hand, as another technique that individually performs the meter-in control and the meter-out control on the hydraulic actuator, a technique is also known in which a meter-in selector valve that switches a port of the hydraulic actuator connected to the hydraulic pump while controlling a supply flow rate to the port and a meter-out selector valve that switches a port of the hydraulic actuator connected to the oil tank while controlling a discharge flow rate from the port are provided, and the meter-in selector valve and the meter-out selector valve are independently controlled (see, for example, PTL 2).
However, in the configuration in which the control of supply and discharge of oil to and from the hydraulic actuator is performed using the four metering valves as in PTL 1, in addition to four spools (or poppets) forming the respective four metering valves, four actuators (in PTL 1, solenoids) allowing the spools to be moved are needed, disadvantageously leading to a large number of components and increased costs. Moreover, in PTL 1, when both meter-in valves are opened to perform the recycling as described above, recycling oil passes through the two meter-in valves, making the control of a recycling flow rate difficult to control. Furthermore, the total flow rate of the recycling flow rate and the pump flow rate passes through the other meter-in valve, resulting in the need for a larger opening and in an increased valve size.
In contrast, the control circuit in PTL 2 has fewer components than the hydraulic actuator in PTL 1 but needs, besides two spools forming the respective two selector valves of the meter-in selector valve and the meter-out selector valve, a total of four actuators (in Patent Literature 2, electromagnetic proportional pressure control valves) allowing each of the spools to be moved in both directions. Thus, a further reduction in the number of components has been desired, and this is an object of the present invention.
The present invention has been developed in view of the above-described circumstances. An invention in claim 1 is a hydraulic actuator control circuit for controlling supply and discharge of oil to and from a hydraulic actuator, the hydraulic actuator control circuit including a meter-in valve that controls a supply flow rate from a hydraulic pump to the hydraulic actuator, and a meter-out selector valve arranged downstream of the meter-in valve to switch between a direction of supply of hydraulic oil td the hydraulic actuator and a direction of discharge of hydraulic oil from the hydraulic actuator while controlling a discharge flow rate from the hydraulic actuator to an oil tank.
An invention in claim 2 is the hydraulic actuator control circuit in claim 1 characterized in that a pressure compensation valve for keeping a pressure difference between an upstream side and a downstream side of the meter-in valve constant is provided upstream of the meter-in valve.
An invention in claim 3 is the hydraulic actuator control circuit in claim 1 characterized in that a recycling control valve for controlling a recycling flow rate at which discharged oil from one of oil chambers of the hydraulic actuator is supplied to the other oil chamber is provided downstream of the meter-out selector valve.
The invention in claim 1 allows meter-in control and meter-out control to be individually performed, while enabling the number of components to be reduced to contribute to cost reduction.
The invention in claim 2 allows flow rate control to be accurately performed using the meter-in valve.
The invention in claim 3 facilitates control of the recycling flow rate, allowing accurate recycling flow rate control to be achieved.
An embodiment of the present invention will be described below based on the drawings.
Moreover, in
The pressure compensation valve 5 receives an inlet-side pressure and an outlet-side pressure on the meter-in valve 7 disposed downstream of the pressure compensation valve 5 to control the flow rate so as to keep a pressure difference between an upstream side and a downstream of the meter-in valve 7 constant.
Furthermore, the check valve 6 is configured to permit a flow of oil from the pressure compensation valve 5 to the meter-in valve 7, while inhibiting a flow in the opposite direction.
Furthermore, the meter-in valve 7 is a pilot valve that is pilot-operated by an electromagnetic proportional valve for the meter-in valve 20 (not depicted in
Furthermore, the meter-out selector valve 8 is a pilot selector valve that is pilot-operated by a contraction-side electromagnetic proportional valve for the meter-out selector valve 21a and an extension-side electromagnetic proportional valve for the meter-out selector valve 21b (not depicted in
Moreover, 12 is a recycling oil path located downstream of the meter-out selector valve 8 to allow the rod-side oil path 10 and the head-side oil path 11 to communicate with each other. A recycling control valve 13 is disposed in the recycling oil path 12. The recycling control valve 13 is a pilot selector valve that is pilot-operated by an electromagnetic proportional valve for the recycling control valve 22 (not depicted in
Additionally, 14 is a bypass oil path branching from a discharge line 4 from the hydraulic pump 2 and extending to the oil tank 3. A bypass valve 15 is disposed in the bypass path 14. The bypass valve 15 is a pilot selector valve that is pilot-operated by an electromagnetic proportional valve for the bypass valve 23 (not depicted in
On the other hand, as depicted in a block diagram in
Now, control performed by the controller 9 will be described. First, when the hydraulic-cylinder operation unit has not been operated, the controller 9 outputs no actuating control signal to the electromagnetic proportional valve for the meter-in valve 20, the contraction-side electromagnetic proportional valve for the meter-out selector valve 21a, the contraction-side electromagnetic proportional valve for the meter-out selector valve 21b, the electromagnetic proportional valve for the recycling control valve 22, or the electromagnetic proportional valve for the bypass valve 23. Thus, the meter-in valve 7 is controllably placed in the neutral position N where the discharged oil from the hydraulic pump 2 is not passed to the meter-out selector valve 8. The meter-out selector valve 8 is controllably placed in the neutral position N where the oil supplied through the meter-in valve 7 is not passed to the hydraulic cylinder 1 and where the discharged oil from the hydraulic cylinder 1 is not passed to the oil tank 3. The recycling control valve 13 is controllably placed in the closed position N where the recycling oil path 12 is closed. Thus, oil is not supplied from the hydraulic pump 2 to the hydraulic cylinder 1 or discharged from the hydraulic cylinder 1 to the oil tank 3, the recycling is also not performed, and the hydraulic cylinder 1 is not contracted or extended. Furthermore, the bypass valve bypass valve 15 is controlled to open the bypass path 14 with the maximum opening area, and thus, the hydraulic pump 2 exerts a low discharge pressure.
On the other hand, when the hydraulic-cylinder operation unit is operated to the contraction side, the controller 9 outputs the actuating control signal to the electromagnetic proportional valve for the meter-in valve 20 to controllably place the meter-in valve 7 in the actuation position X. In this case, the opening area of the meter-in valve 7 is controllably increased or reduced based on control signals from the controller 9. Thus, a pump flow rate of oil controlled by the meter-in valve 7 is supplied from the meter-in valve 7 to the meter-out selector valve 8. As described above, the pressure compensation valve 5 is actuated to keep the pressure difference between the upstream side and the downstream side of the meter-in valve 7 constant, allowing for accurate flow rate control.
Moreover, when the hydraulic-cylinder operation unit is operated to the contraction side, the controller 9 outputs the actuating control signal to the contraction-side electromagnetic proportional valve for the meter-out selector valve 21a to controllably place the meter-out selector valve 8 in the contraction-side actuation position X. In this case, since the opening area of the contraction-side supply path 8c is set sufficiently larger than the opening area of the meter-in valve 7 as described above, a pump flow rate of oil controlled by the meter-in valve 7 is supplied to the rod-side oil chamber 1b of the hydraulic cylinder 1 through the contraction-side supply path 8c. On the other hand, the oil in the head-side oil chamber 1c is discharged to the oil tank 3 through the contraction-side discharge path 8e in the meter-out selector valve 8. The opening area of the contraction-side discharge path 8e is controllably increased or reduced based on control signals from the controller 9. Thus, a discharge flow rate of oil controlled by the meter-out selector valve 8 flows from the head-side oil chamber 1c to the oil tank 3.
Moreover, when the hydraulic-cylinder operation unit is operated to the contraction side, the controller 9 outputs no actuating control signal to the electromagnetic proportional valve for the recycling control valve 22. Consequently, the recycling control valve 13 is controllably placed in the closed position N where the recycling oil path 12 is closed.
When the hydraulic-cylinder operation unit is operated to the contraction side, a pump flow rate of oil controlled by the meter-in valve 7 is supplied to the rod-side oil chamber 1b of the hydraulic cylinder 1. On the other hand, the discharged oil from the head-side oil chamber 1c is subjected to flow rate control by the meter-out selector valve 8 and then flows to the oil tank 3. Thus, the hydraulic cylinder 1 is contracted. In this case, the controller 9 controllably increases or reduces the opening areas of the meter-in valve 7 and the meter-out selector valve 8 so that the pump flow rate and the discharge flow rate correspond to the amount of operation of the hydraulic-cylinder operation unit. This allows the hydraulic cylinder 1 to be contracted at a speed corresponding to the amount of operation of the hydraulic-cylinder operation unit.
Now, a case where the hydraulic-cylinder operation unit is operated to the extension side will be described. Control varies between a case where the head-side pressure in the hydraulic cylinder 1 is higher than the rod-side pressure in the hydraulic cylinder 1, precluding the recycling from the rod-side oil chamber 1b to the head-side oil chamber 1c, and a case where the rod-side pressure is higher than the head-side pressure and where the recycling from the rod-side oil chamber 1b to the head-side oil chamber 1C is performed. Thus, first, the case where the head-side pressure is higher than the rod-side pressure will be described.
If the hydraulic-cylinder operation unit is operated to the extension side when the head-side pressure in the hydraulic cylinder 1 is higher than the rod-side pressure in the hydraulic cylinder 1, the controller 9 outputs the actuating control signal to the electromagnetic proportional valve for the meter-in valve 20 to controllably place the meter-in valve 7 in the actuation position X. In this case, the opening area of the meter-in valve 7 is controllably increased or reduced based on control signals from the controller 9. Thus, a pump flow rate of oil controlled by the meter-in valve 7 is supplied from the meter-in valve 7 to the meter-out selector valve 8.
Moreover, if the hydraulic-cylinder operation unit is operated to the extension side when the head-side pressure is higher than the rod-side pressure, the controller 9 outputs the actuating control signal to the contraction-side electromagnetic proportional valve for the meter-out selector valve 21b. Consequently, the meter-out selector valve 8 is controllably placed in an extension-side actuation position Y. In this case, since the opening area of the extension-side supply path 8d is set sufficiently larger than the opening area of the meter-in valve 7 as described above, a pump flow rate of oil controlled by the meter-in valve 7 is supplied to the head-side oil chamber 1c of the hydraulic cylinder 1 through the extension-side supply path 8d. On the other hand, the oil in the rod-side oil chamber 1b is discharged to the oil tank 3 through the extension-side discharge path 8f. The opening area of the extension-side discharge path 8f is controllably increased or reduced based on control signals from the controller 9. Thus, the discharge flow rate controlled by the meter-out selector valve 8 flows from the rod-side oil chamber 1b to the oil tank 3.
If the hydraulic-cylinder operation unit is operated to the extension side when the head-side pressure is higher than the rod-side pressure, the controller 9 outputs no actuating control signal to the electromagnetic proportional valve for the recycling control valve 22. Thus, the recycling control valve 13 is controllably placed in the closed position N where the recycling oil path 12 is closed.
If the hydraulic-cylinder operation unit is operated to the extension side when the head-side pressure is higher than the rod-side pressure (when the recycling from the rod-side oil chamber 1b to the head-side oil chamber 1c cannot be preformed), a pump flow rate of oil controlled by the meter-in valve 7 is supplied to the head-side oil chamber 1c of the hydraulic cylinder 1. On the other hand, the discharged oil from the rod-side oil chamber 1b is subjected to flow rate control by the meter-out selector valve 8 and then flows to the oil tank 3. Consequently, the hydraulic cylinder 1 is extended. In this case, the controller 9 controllably increases or reduces the opening areas of the meter-in valve 7 and the meter-out selector valve 8 so that the pump flow rate and the discharge flow rate correspond to the amount of operation of the hydraulic-cylinder operation unit. Thus, the hydraulic cylinder 1 can be extended at a speed corresponding to the amount of operation of the hydraulic-cylinder operation unit.
On the other hand, if the hydraulic-cylinder operation unit is operated to the extension side when the rod-side pressure in the hydraulic cylinder 1 is higher than the head-side pressure in the hydraulic cylinder 1, the controller 9 outputs the actuating control signal to the electromagnetic proportional valve for the meter-in valve 20 and the contraction-side electromagnetic proportional valve for the meter-out selector valve 21b as in the case where the head-side pressure is higher than the rod-side pressure as described above. Consequently, the meter-in valve 7 is controllably placed in the actuation position X, whereas the meter-out selector valve 8 is controllably placed in the extension-side actuation position Y. Thus, a pump flow rate of oil controlled by the meter-in valve 7 is supplied to the head-side oil chamber 1c of the hydraulic cylinder 1 through the meter-out selector valve 8 in the extension-side actuation position Y. On the other hand, the oil in the rod-side oil chamber 1b is discharged to the oil tank 3 through the meter-out selector valve 8 in the extension-side actuation position Y. In this case, the opening areas of the meter-in valve 7 and the meter-out selector valve 8 are controllably increased or reduced based on control signals from the controller 9.
Moreover, if the hydraulic-cylinder operation unit is operated to the extension side when the rod-side pressure is higher than the head-side pressure, the controller 9 outputs the actuating control signal to the electromagnetic proportional valve for the recycling control valve 22 to controllably position the recycling control valve 13 in the open position X. In this case, the opening area of the recycling control valve 13 is controllably increased or reduced based on control signals from the controller 9. Thus, a recycling flow rate of oil controlled by the recycling control valve 13 is supplied from the rod-side oil chamber 1b to the head-side oil chamber 1c of the hydraulic cylinder 1.
If the hydraulic-cylinder operation unit is operated to the extension side when the rod-side pressure is higher than the head-side pressure, the head-side oil chamber 1c of the hydraulic cylinder 1 is supplied with a pump flow rate of oil controlled by the meter-in valve 7 and a recycling flow rate of oil controlled by the recycling control valve 13. On the other hand, the discharged oil from the rod-side oil chamber 1b is supplied to the head-side oil chamber 1c as the recycling flow rate, and the remaining oil is subjected to flow rate control by the meter-out selector valve 8 and is then discharged to the oil tank 3. Consequently, the hydraulic cylinder 1 is extended. In this case, the controller 9 controls the opening area of the recycling control valve 13 so as to provide the desired recycling flow rate according to the difference between the rod-side pressure and the head-side pressure and the amount of operation of the hydraulic-cylinder operation unit. Further, in order for a flow rate of oil corresponding to the amount of operation of the hydraulic-cylinder operation unit to be supplied to the head-side oil chamber 1c, the controller 9 controls the opening area of the meter-in valve 7 so as to provide the pump flow rate equal to a pump flow rate obtained by subtracting the recycling flow rate from the corresponding flow rate. Furthermore, in order for a flow rate of oil corresponding to the amount of operation of the hydraulic-cylinder operation unit to be discharged from the rod-side oil chamber 1b, the controller 9 controls the opening area of the extension-side discharge path 8f in the meter-out selector valve 8 so as to provide the discharge flow rate equal to a discharge flow rate obtained by subtracting the recycling flow rate from the corresponding flow rate. Thus, the hydraulic cylinder 1 can be extended at a speed corresponding to the amount of operation of the hydraulic-cylinder operation unit.
When the hydraulic-cylinder operation unit is operated to the contraction side or the extension side, the controller 9 outputs the actuating control signal to the electromagnetic proportional valve for the bypass valve 23 to controllably increase or reduce the opening area of the bypass valve 15 in order to adjustably increase or reduce the pump flow rate in association with the opening area of the meter-in valve 7. Thus, a proper amount of discharged oil can be supplied from the hydraulic pump 2 to the meter-in valve 7.
In the present embodiment configured as described above, the hydraulic actuator control circuit for controlling supply and discharge of oil to and from the hydraulic cylinder 1 includes the meter-in valve 7 that controls the supply flow rate from the hydraulic pump 2 to the hydraulic cylinder 1 and the meter-out selector valve 8 arranged downstream of the meter-in valve 7 to switch between the direction of supply of hydraulic oil to the hydraulic cylinder 1 and the direction of discharge of hydraulic oil from the hydraulic cylinder 1 while controlling the discharge flow rate from the hydraulic cylinder 1 to the oil tank 3. The hydraulic oil supplied from the hydraulic pump 2 is subjected to flow rate control by the meter-in valve 7 and is then supplied to the hydraulic cylinder 1 via the meter-out selector valve 8 that switches between the supply direction and the discharge direction. On the other hand, the discharged oil from the hydraulic cylinder 1 is subjected to flow rate control by the meter-out selector valve 8 that switches between the supply direction and the discharge direction and is then discharged to the oil tank 3.
As a result, the control of the supply flow rate from the hydraulic pump 2 to the hydraulic cylinder 1 (meter-in control) is performed by the meter-in valve 7, whereas the control of the discharge flow rate from the hydraulic cylinder 1 to the oil tank 3 (meter-out control) is performed by the meter-out selector valve 8. Thus, the meter-in control and the meter-out control are performed by the individual valves, allowing the relation between the meter-in and the meter-out to be easily changed in association with the contents of work and an operator. Moreover, even though the meter-in control and the meter-out control can be individually performed, the meter-in control, the meter-out control, and the directional control can be performed on the hydraulic cylinder 1 using the two valves of the meter-in valve 7 and the meter-out selector valve 8. Furthermore, the meter-in valve 7 performs only the meter-in control and does not execute the directional control. Consequently, the meter-in valve 7 need not be moved in both directions. Accordingly, movement of the meter-in valve 7 may be achieved exclusively using a single actuator (or a single set of actuators; in the present embodiment, the electromagnetic proportional valve for the meter-in valve 20 or a set of the electromagnetic proportional valve for the meter-in valves 20), enabling the number of components to be reduced to contribute to cost reduction.
Furthermore, on the upstream side of the meter-in valve 7, the pressure compensation valve 5 is provided which keeps the pressure difference between the upstream side and the downstream side of the meter-in valve 7 constant. Thus, the flow rate control can be accurately performed using the meter-in valve 7 without being affected by, for example, a fluctuation in the pressure of the hydraulic pump 2.
Moreover, on the downstream side of the meter-out selector valve 8, the recycling control valve 13 is provided which controls the recycling flow rate at which the discharged oil from one of the oil chambers (in the present embodiment, the rod-side oil chamber 1b) of the hydraulic cylinder 1 is supplied to the other oil chamber (in the present embodiment, the head-side oil chamber 1c). This enables the pump flow rate to be reduced by an amount equal to the recycling flow rate from one of the oil chambers to the other oil chamber, contributing to energy saving. The recycling control valve 13 is provided independently of the meter-in valve 7 and the meter-out selector valve 8, allowing the recycling flow rate to be easily and accurately controlled.
The present invention is of course not limited to the above-described embodiment. For example, in the above-described embodiment, the meter-in valve, the meter-out selector valve, the recycling control valve, and the bypass valve are pilot selector valves, and the electromagnetic proportional valves are used as actuators that operate the pilot selector valves. However, the meter-in valve, the meter-out selector valve, the recycling control valve, and the bypass valve may be electromagnetic proportional valves directly driven by solenoids.
Furthermore, in the above-described embodiment, the recycling is performed such that the discharged oil from the rod-side oil chamber is supplied to the head-side oil chamber 1c when the hydraulic cylinder is extended. However, depending on a load imposed on a working portion driven by the hydraulic cylinder, the orientation of the working portion, and the like, the recycling may be performed such that discharged oil from the head-side oil chamber is supplied to the rod-side oil chamber when the hydraulic cylinder is contracted.
Moreover, in the above-described embodiment, the recycling is controlled so as to make the total flow rate of the recycling flow rate and the pump flow rate equal to the flow rate corresponding to the amount of operation of the hydraulic-cylinder operation unit. However, the recycling may be controlled so as to make the total flow rate of the recycling flow rate and the pump flow rate higher than the flow rate corresponding to the amount of operation of the hydraulic-cylinder operation unit, increasing an actuation speed of the hydraulic cylinder. Such a change in control may be optionally made by changing settings for the controller 9.
The present invention can be utilized for a hydraulic actuator control circuit for controlling supply and discharge of oil to and from a hydraulic actuator such as a hydraulic cylinder.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-021794 | Feb 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/052367 | 2/4/2016 | WO | 00 |
