JPH0423124B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control valve device that has different feels depending on the content of each work in a construction machine used for a variety of purposes.

[Prior Art] In a conventional control valve device operated by a pilot valve, there is always a one-to-one relationship between the lever stroke of the pilot valve and the pilot signal pressure that is its output, and the When used for multiple purposes, such as work and work that requires fine manipulation, it is suitable for excavation work where the controlled flow rate is relatively large.

[Problems to be Solved by the Invention] Therefore, when performing work with a relatively small control flow rate, such as work requiring fine operation, the control valve is operated in a small opening range, that is, a small lever stroke range. This made operation extremely difficult.

The present invention has been developed to eliminate these drawbacks, and its purpose is to have a simple structure, but to have a different feeling depending on the work content of each purpose in multi-purpose work, and especially in the case of fine operation. An object of the present invention is to provide a control valve device that allows full stroke operation of a lever.

[Means for Solving the Problems] The control valve device of the present invention includes an actuator, a hydraulic source, a control valve that controls the flow of pressure oil from the hydraulic source to the actuator, a pilot valve that switches the control valve, and a pilot valve that controls the flow of pressure oil from the hydraulic source to the actuator. A pilot pump supplies pressure oil to the valve, a pressure reducing valve is installed in the pipeline from the pilot signal pressure outlet of the pilot valve to the pilot chamber of the control valve, and a small part of the oil chamber is installed to press the spring of the pressure reducing valve with a piston. Either connect one side upstream of the pressure reducing valve and connect the oil chamber on the other side to pressure oil, or connect the stepped cylinder connected to the tank and the oil chamber on the other side of the stepped cylinder to pressure oil, or It shall consist of a switching valve that is switched to connect to the tank.

Further, the switching valve may be energized when the rotational speed of the prime mover becomes less than or equal to a predetermined rotational speed.

[Function] When controlling the flow of pressure oil from the hydraulic source to the actuator using a control valve that switches the flow of pressure oil by operating a pilot valve, when the control flow rate is relatively large, the pressure oil of the pilot pump is transferred to one of the stepped cylinders. Connected to the oil chambers on one side and the other side, the combined pressure is applied to the spring of the pressure reducing valve through the piston, and the pilot signal of the high set pressure that is depressurized flows into the pilot chamber of the control valve and moves the spool of the control valve by a large amount. However, on the other hand,
When relatively small control flow control is required, the switching valve is energized to connect the oil chamber on the other side of the stepped cylinder to the tank, and the pilot pump is connected only to the oil chamber on one side of the stepped cylinder. By connecting pressure oil and applying a smaller pressure to the spring of the pressure reducing valve via the piston than when the control flow rate is relatively large, a pilot signal of a low set pressure flows into the pilot of the control valve, thereby controlling the control valve. Since the spool is moved, fine control is possible.

In addition, by energizing the switching valve when the prime mover rotation speed falls below a predetermined rotation speed, the same operation as fine control is performed on the reduced discharge amount. .

[Example] The present invention will be described below with reference to figures showing examples. The actuator 11 sucks oil in a tank 12 and supplies and discharges oil by providing a control valve 15 midway from a variable discharge amount pump (hereinafter simply referred to as pump) 14 whose maximum pressure is controlled by a relief valve 13. A control cylinder 16 is attached to the pump 14 to control the discharge amount. As shown in the figure, when the control valve 15 is in the neutral state, the pressure oil of the pump 14 passes through the passage 17A of the switching valve 17 and is transferred from the throttle mechanism 18 to the tank 12. is discharged. As the pressure oil passes through the throttle mechanism 18, pressure is generated upstream of the throttle mechanism 18, and in response to this pressure, the piston rod 19 of the control cylinder 16 moves forward, thereby throttling the discharge amount of the pump 14.

A pilot valve 23 receives pressure oil from a pilot pump 22 whose maximum pressure is controlled by a relief valve 21, and is configured to allow pilot signal pressure to flow out from either one of outlets 25 and 26 by operating a lever 24. The control valve 15 is switched by moving a spool (not shown), and pilot chambers 27 and 28 on the left and right sides of the spool are connected to outlets 25 and 26 with pressure reducing valves 29 and 30 placed in between. The springs 31 of the pressure reducing valves 29 and 30 are pressed by the pistons 32A and 33A of the stepped cylinders 32 and 33, and the large diameter oil chambers 34 and 35 of the stepped cylinders 32 and 33
is connected to the upstream side of the pressure reducing valves 29 and 30, and the small diameter oil chambers 36 and 37 are connected to a switching valve 38 provided on the discharge side of the pilot pump 22. A shuttle valve 39 is connected to the pipes connecting the outlets 25 and 26 of the pilot valve 23 to the pressure reducing valves 29 and 30, and the downstream side of the shuttle valve 39 is connected to the pilot chamber 40 of the switching valve 17.

Next, the operation of the embodiment described above will be explained. First, in the case of excavation work in which the controlled flow rate is relatively large, the lever 24 of the pilot valve 23 is tilted to the right side, for example, with the switching valve 38 in a de-energized state as shown in the figure. As a result, the pilot signal pressure at the outlet 25 of the pilot valve 23 flows into the pilot chamber 28 on the left side of the control valve 15 through the pressure reducing valve 29 and moves the spool to the right. At the same time, the pilot signal pressure that has passed through the shuttle valve 39 also flows into the pilot chamber 40 of the switching valve 17 and raises the spool (not shown) of the switching valve 17, thereby passing into the tank 12 through the passage 17A of the switching valve 17. The pressure oil from the pump 14 that has been discharged passes from the fully open passage 17A to the half-open passage 17B to the fully closed passage 17C and stops being discharged to the tank 12. On the other hand, since the control valve 15 is switched to the left ventricle, the pressure oil from the pump 14 flows into the head side of the actuator 11, and the oil from the rod side is discharged into the tank 12. The pilot signal pressure that moves the spool of the control valve 15 is applied to both the large and small diameter oil chambers 34 and 36 of the stepped piston 32, so the spring 31 is strongly pressed and the pressure decreases downstream of the pressure reducing valve 29. The pressure, that is, the set pressure increases, and this pressure oil is used as the pilot signal pressure to control the control valve 1.
5 into the pilot chamber 28 of the control valve 1.
5's spool moves a lot.

Next, a case will be described in which work requires a relatively small amount of fine manipulation of the controlled flow rate. Note that the operation of the switching valve 17 is the same as in the case of the excavation work described above, so a description thereof will be omitted, and the case where the lever 24 of the pilot valve 23 is tilted to the right will be described. In this case, the switching valve 38 is energized. As a result, the stepped cylinder 32
Since the small diameter oil chamber 36 of the stepped cylinder is connected to the tank 12, the spring 31 of the pressure reducing valve 29 is only pressed by the pilot signal pressure applied to the large diameter oil chamber 34 of the stepped cylinder. The pressure is weaker than in the case of the excavation work described above, and the downstream pressure of the pressure reducing valve 29, that is, the set pressure is low, so this pilot signal pressure is
The amount of water flowing into the pilot chamber 28 and displacing the spool of the control valve 15 is reduced. The former case is when the pilot signal pressure is applied to both oil chambers 34 and 36 of the stepped cylinder 32, and when the pilot signal pressure is applied only to the large diameter chamber 34 by energizing the switching valve 38. is the latter. Therefore, if the latter pressing force acting on the piston 32A is half of the former pressing force, the pilot signal pressure flowing into the pilot chamber 28 of the control valve 15 in the latter case is reduced by the pressure reducing valve 29 to half that of the former case. The amount of movement of the spool of the control valve 15 is half of the former in the latter case. Therefore, in the latter case, even if the lever 24 of the pilot valve 23 is pushed down a full stroke, the amount of movement of the spool of the control valve 15 will be half that of the former case, allowing fine control.

In addition, in the above explanation, the amount of spool movement of the control valve 15 is half in the latter case than in the former case, but this depends on the selection of the diameters of the large and small oil chambers 34 and 36 of the stepped cylinder 32. Needless to say, it can happen any way you like. Further, in the above description, the large diameter oil chamber 34 of the stepped cylinder 32 was connected to the upstream side of the pressure reducing valve 29, and the small diameter oil chamber 36 was connected to the discharge side of the pilot pump 22, but these may be interchanged. Further, although the stepped cylinder 32 has two stages, it may have three or more stages and may be switched between one stage, two stages, and then three stages. Furthermore, the stepped cylinder 32
Although the large diameter oil chambers 34 and 35 of 33 are connected to the outlet of the pilot pump 22 via the switching valve 38, they may be connected to the outlet of the pump 14 via the switching point 38.

When the rotation speed of the prime mover (not shown) that drives the pump 14 becomes less than a predetermined rotation speed,
Since the discharge amount of the pump 14 decreases, the spool of the control valve 15 switches the total discharge amount by a short movement distance. Therefore, the lever 24 of the pilot valve 23 is required to be operated in the same way as in the case where the fine operation described above is required. For this reason, when the rotational speed of the prime mover falls below a predetermined rotational speed, the switching valve 38 detects this using, for example, a tacho generator and is energized.

[Effects of the Invention] As explained above, the control valve device of the present invention provides a pressure reducing valve with variable set pressure using a stepped cylinder between the pilot valve and the pilot chamber of the control valve, and does not require fine operation. In this case, the set pressure of the pressure reducing valve is lowered, the pilot signal pressure is reduced, and the pilot signal pressure is allowed to flow into the pilot chamber of the control valve, and the spool travel amount is reduced, so that the stroke amount of the lever of the pilot switching valve can be maintained at full capacity even in the case of slight operation. This has the advantage that the stroke allows fine operation, resulting in improved operability of the control valve.

[Brief explanation of drawings]

The figure is a hydraulic circuit diagram showing an embodiment of the present invention. 11...actuator, 12...tank, 14
... Hydraulic source, 15 ... Control valve, 22 ... Pilot pump, 23 ... Pilot valve, 25, 26 ...
...Exit, 27, 28...Pilot room, 29, 3
0...Pressure reducing valve, 32, 33...Stepped cylinder, 3
2A, 33A...Piston, 34, 35...Large diameter oil chamber, 36, 37...Small diameter oil chamber, 38...Switching valve.

Claims (1)

[Scope of Claims] 1. An actuator, a hydraulic source, a control valve that controls the flow of pressure oil from the hydraulic source to the actuator, a pilot valve that switches the control valve, and a supply of pressure oil to the pilot valve. A pilot pump to
A pressure reducing valve is provided in a conduit from the pilot signal pressure outlet of the pilot valve to the pilot chamber of the control valve, and at least one side of the oil chamber is connected to the pressure reducing valve in order to press the spring of the pressure reducing valve with a piston. A stepped cylinder that is connected upstream and has an oil chamber on the other side connected to the pressure oil or a tank, and an oil chamber on the other side of the stepped cylinder that is connected to the pressure oil or to the tank. A control valve device consisting of a switching valve. 2. The control valve device according to claim 1, wherein the switching valve is energized when the rotational speed of the prime mover becomes less than or equal to a predetermined rotational speed.