Actuator control device
View Patent ↗In an actuator control device that controls an expansion/contraction operation of a hydraulic cylinder, when a main spool 52 is switched to a discharge position for discharging working fluid in the hydraulic cylinder, a back pressure chamber 7 communicates with a tank passage 13 via a first port 14 , thereby opening an operate check valve 51 , and as a result, the working fluid in the hydraulic cylinder flows into a return passage 4 from an actuator port 1 and into a pilot chamber 20 through a second port 15 . A pilot spool 53 is maintained in a balanced position by the pressure of the pilot chamber 20 , which is caused to act by a front-rear differential pressure of a control throttle 25 , and the biasing force of a spring 22 housed in a spring chamber 21 , and therefore the opening area of the first port 14 is controlled to and maintained at a fixed level.
1. An actuator control device that controls an expansion/contraction operation of a hydraulic cylinder, comprising:
an actuator port connected to the hydraulic cylinder;
a main spool that switches the actuator port between communication with a working fluid supply passage and communication with a working fluid return passage; and
an operate check valve interposed between the hydraulic cylinder and the main spool, which allows a working fluid to flow from the supply passage to the actuator port, and allows the working fluid to flow from the actuator port to the return passage in accordance with a pressure of a back pressure chamber,
wherein, the actuator port communicates constantly with the back pressure chamber of the operate check valve via a connecting passage,
the main spool comprises:
a pilot spool housed slidably in the main spool;
a pilot chamber delimited on one end side of the pilot spool;
a spring chamber delimited on another end side of the pilot spool;
a biasing member that is housed in the spring chamber and biases the pilot spool against a pressure of the pilot chamber; and
a first port that connects the back pressure chamber to a tank passage downstream of the return passage and a second port that connects the return passage to the pilot chamber when the main spool is switched to a discharge position for discharging the working fluid in the hydraulic cylinder,
the pilot spool comprises a control throttle that applies resistance to a flow of working fluid flowing out of the pilot chamber into the tank passage, and
when the main spool is switched to the discharge position, the pilot spool is maintained in a balanced position by the pressure of the pilot chamber, which acts in accordance with a front-rear differential pressure of the control throttle, and a biasing force of the biasing member in the spring chamber, whereby an opening area of the first port is controlled to and maintained at a fixed level.
2. The actuator control device as defined in claim 1 , wherein the main spool further comprises:
a third port that is provided so as to communicate with the spring chamber and communicates with the tank passage when the main spool is switched to the discharge position; and
a pressure chamber that is delimited by an outer periphery of the pilot spool and connects the first port to the third port when the pilot spool moves against the biasing force of the biasing member in the spring chamber, and
when the main spool is switched to the discharge position, the back pressure chamber of the operate check valve communicates with the tank passage through the first port, the pressure chamber, and the third port, whereby the operate check valve opens and the actuator port communicates with the return passage.
3. The actuator control device as defined in claim 1 , wherein the operate check valve further comprises a second valve body that is housed in a valve body, connects the actuator port to the back pressure chamber, and moves slidingly along a guide member,
the second valve body comprises:
a first control orifice having an opening portion on a tip end portion of the second valve body;
a second control orifice that communicates with the first control orifice and has a larger opening diameter than the first control orifice;
a spring chamber that communicates with both the second control orifice and the back pressure chamber, and is delimited by a back surface of the second valve body;
a biasing member that is housed in the spring chamber and biases the second valve body in a retreating direction from the guide member such that the tip end portion of the second valve body is pressed against the valve body, thereby blocking a flow through the first control orifice; and
an introduction port that is capable of introducing the working fluid from the connecting passage into the second control orifice and decreases in opening area as the second valve body moves against a biasing force of the biasing member so as to advance into the guide member,
when a front-rear differential pressure of the second control orifice is equal to or smaller than a predetermined value, the actuator port communicates with the back pressure chamber via the introduction port and the second control orifice, and
when the front-rear differential pressure of the second control orifice exceeds the predetermined value, the second valve body moves against the biasing force of the biasing member such that the actuator port communicates with the back pressure chamber via the first control orifice.
4. The actuator control device as defined in claim 3 , wherein the introduction port has an opening portion on an outer peripheral surface of the second valve body, and
when the front-rear differential pressure of the second control orifice exceeds the predetermined value, the opening portion of the introduction port is closed by an inner peripheral surface of the guide member.
5. The actuator control device as defined in claim 2 , wherein the operate check valve further comprises a second valve body that is housed in a valve body, connects the actuator port to the back pressure chamber, and moves slidingly along a guide member,
the second valve body comprises:
a first control orifice having an opening portion on a tip end portion of the second valve body;
a second control orifice that communicates with the first control orifice and has a larger opening diameter than the first control orifice;
a spring chamber that communicates with both the second control orifice and the back pressure chamber, and is delimited by a back surface of the second valve body;
a biasing member that is housed in the spring chamber and biases the second valve body in a retreating direction from the guide member such that the tip end portion of the second valve body is pressed against the valve body, thereby blocking a flow through the first control orifice; and
an introduction port that is capable of introducing the working fluid from the connecting passage into the second control orifice and decreases in opening area as the second valve body moves against a biasing force of the biasing member so as to advance into the guide member,
when a front-rear differential pressure of the second control orifice is equal to or smaller than a predetermined value, the actuator port communicates with the back pressure chamber via the introduction port and the second control orifice, and
when the front-rear differential pressure of the second control orifice exceeds the predetermined value, the second valve body moves against the biasing force of the biasing member such that the actuator port communicates with the back pressure chamber via the first control orifice.
6. The actuator control device as defined in claim 5 , wherein the introduction port has an opening portion on an outer peripheral surface of the second valve body, and
when the front-rear differential pressure of the second control orifice exceeds the predetermined value, the opening portion of the introduction port is closed by an inner peripheral surface of the guide member.