JPS599302A - Hydraulic control device - Google Patents

Abstract

PURPOSE:To make the easy addition of an attachment valve possible by a method wherein a pump is controlled by a pilot pressure prevailing between a pressure generating mechanism installed in the center bypass passage of a changeover valve, which is arranged at the lowest course of the stream from the pump, and a logic valve arranged in the upstream of said pressure generating mechanism. CONSTITUTION:In case that an attachment valve 23 is added, the delivery rate of a pump 2 is decreased by the pilot pressure in the upstream of a pressure generating mechanism 17, because the port 27 of a logic valve 20 is communicated to a tank and the logic valve is open under the conditions that changeover valves 8-10 and the attachment valve 23 are in their neutral positions respectively, while the delivery rate of the pump 2 is increased by changing-over the attachment valve 23, because the logic valve 20 is closed by said changing-over, resulting in lowering the pilot pressure. On the other hand, in case that the attachment valve is unnecessary, a poppet valve 30 and the like are removed from the logic valve 20 in order to extinguish the function of the logic valve 20 and only the pressure generating mechanism 17 is left at the back of the selector valve 10. The easy utilization of the attachment valve 23 is realized, because the mounting and dismounting of the logic valve 20 is easy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic system used in a hydraulic excavator or the like, and particularly to a hydraulic control system having a logic valve for adding an attachment valve to a control device.

Generally, a hydraulic control device equipped with a standard actuator in a hydraulic excavator, etc. has pumps 1 and 2 driven by an engine, as shown in FIG. 1, and switching valves 3, 4, 5, 6 connected to this pump 1. a control valve 7 having a pump 2;
It consists of a control valve 11 having switching valves 8, 9, 10 connected to the control valves 7, 11, and downstream of the center bypass passages 12, 13 and the tank passages 14, 15 via the switching valves. Pressure generator grooves 16 and 17 having a throttle and a relief valve are provided between the pressure generator grooves 16 and 1.
7, pilot pressure generated by the switching valve is applied to control cylinders 18 and 19 to control the discharge amount of the pumps 1 and 2.

When a hydraulic system having such a configuration is used to control a standard actuator, there are few problems in its control. However, in recent years, there has been a demand for attachments such as breaker specifications due to the versatility of hydraulic excavators, etc., and in order to cope with this, a four-set control valve 11 is equipped with a reserve switching valve for attachment in advance. A method is adopted in which a control valve is constructed of a control valve and the four control valves 7 described above, and depending on the demand, the three control valves 11 can be replaced with four control valves or modified to provide four control valves. Methods such as making it into a valve have been adopted.

By the way, when the former does not use the attachment valve,
One station is not necessary, and the latter has problems such as an increase in the number of man-hours for installing and removing the control valves and restrictions on the installation layout when replacing the three-station control valve with a four-station control valve or modifying it.

The present invention was made in view of the above-mentioned problems, and its purpose is to use the standard specification switching valve as is when an attachment valve is required, to arrange the attachment valve in any position, and to make the standard specification control valve preset. An object of the present invention is to provide a hydraulic control device that can handle attachment valve specifications by being configured with a logic valve that can be assembled in the same manner.

2 to 4 showing one embodiment of the present invention will be described below. If the members in FIGS. 2, 3, and 4 are the same as those in FIG. 1, the same reference numerals will be used and detailed explanations will be omitted. In FIG. 2, the most downstream switching valve 1 is located upstream of a pressure generator 17 (described later) provided between the center bypass passage 13 and the tank passage 15 of the control valve 11.
A logic valve 20 is interposed in series between the center bypass passage 13 downstream of the center bypass passage 13 and the pump control port 21 provided between the logic valve 20 and the pressure generating mechanism 17 is connected to the pump control port 21 via the circuit 22. Connect to cylinder 19 for use. In addition, a selector valve 25 is combined to interlock with a unit valve 24 of an attachment valve 23 disposed arbitrarily with respect to the control valve 11, and this supply passage 26 is connected to the discharge side of the pump 2, and the selector valve 25 is connected via a circuit 28 to a port 27 that opens and closes the logic valve 20.

Further, FIG. 3 shows details of how the pressure generating mechanism 17 and the logic valve 20 are attached to the control valve 11, and the logic valve 20 and the logic valve 20 are attached to the valve member 29 fixed to the valve body 11a of the control valve 11. A pressure generating mechanism 17 is provided, and the logic valve 20 includes a poppet 30 having a throttle inside.
is inserted, and port 2 is installed at the rear of this poppet 30.
7 and a plug 31 connected to the circuit 28 is removably screwed together. Also, the poppet 30 has a spring 32
The center bypass passage 13 and the control port 21 are connected when the center bypass passage 13 and the control port 21 move against each other. In addition, the pressure generating mechanism 17 uses the pressure of the control port 21 to cause the spring 3 to
A relief poppet 33 is provided which moves against the tank 5 and connects the port 21 to the tank passage 15 via a restriction 34. The other configurations are omitted because they are well-known techniques.

What is shown in FIG. 4 is a control valve 11 from which the logic valve 20 is removed when the attachment valve 23 is not used.
0, and replace the plug 31 with a blank plug 31.
a is screwed onto the valve member 29.

Next, the operation of the present invention will be explained. First, in FIG. 3 when the attachment valve 23 is added, the control valve 1
When the switching valves 8, 9, 30 of the logic valve 2 and the unit valve 24 of the actuation valve 23 are in the neutral position shown in the figure, the logic valve 2
0 port 27 is connected to the tank via the circuit 28 and the selector valve 25, so it is at tank pressure, so the oil in the center bypass passage 13 flows through the poppet 30 that moves against the spring 32. The pilot pressure in front of the throttle 34 that is generated when flowing into the pressure generator groove 17 and from this pressure generating mechanism 17 to the tank acts on the control cylinder 19 via the circuit 22 to minimize the discharge amount of the pump 2. Close.

Now, when the switching valve 10 is switched from the neutral position shown in the figure to any direction position, the flow rate to the downstream center bypass passage 13 decreases according to the amount of movement of the switching valve 10, and the flow rate to the downstream center bypass passage 13 decreases according to this decreased flow rate. The pressure of the pump 21 decreases, and the discharge amount of the pump 2 increases in response to this pressure decrease.

When the unit valve 24 of the attachment valve 23 is switched from the illustrated position to any direction position, the selector valve 25 interlocked with the unit valve 24 cuts off the connection to the tank, so the circuit 28 becomes closed, and the logic valve 20 closes. Since the center bypass passage 13 is cut off at this point, the center bypass flow rate flowing to the pressure generating mechanism 17 becomes zero, and the center bypass passage 13 is cut off.
Since the pilot pressure generated in pump 1 becomes lower, pump 2 can maximize its discharge amount. Therefore, the maximum discharge amount of the pump 2 is such that the supply flow rate from the supply passage 26 to the actuator via the attachment valve 23 can be ensured, and even when the switching valves 8, 9, and 10 of the control valve 11 are operated, the flow rate is maintained through the switching valve. Since the oil supply to the actuator can be secured, combined operation of the control valve 11 and the attachment valve 23 is made possible.

When the attachment valve 23 is not needed, the supply passage 26 connected to the pump 2 and the circuit 28 connected to the port 27 are cut off as shown in FIG. A certain brag 31, spring 3
2. Remove the poppet 30, etc. to eliminate its function, and then replace the spare metal flag 31a with the valve member 29.
By screwing into the control valve 11, the valve member 29 having only the pressure generating mechanism 17 can be made into a fixed control valve 11 to meet standard actuator specifications.

As described above, according to the present invention, the logic valve can be easily installed and removed depending on whether an attachment valve is required or not, so that the number of man-hours can be reduced and the manufacturing cost can be made relatively low. This device can be used in a wide range of applications by arranging the attachment valve at any position without being restricted by installation space.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional hydraulic control device, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a schematic horizontal sectional view of the circuit diagram shown in Fig. 2, and Fig. 4 3 is a schematic horizontal sectional view showing the main parts in FIG. 3. FIG. 1, 2... pump, 3, 4, 5, 6, 8, 9, 10.
...Switching valve, 7,11...Control valve, 12,13...
Center bypass passage, 14, 15...Tank passage, 16
, 17... Pressure generation mechanism, 20... Logic valve, 2
3. Attachment valve. Applicant: Toshiba Machine Co., Ltd.

Claims (1)

[Claims] In a hydraulic control device in which a pressure generator groove is provided between a center bypass passage and a tank passage of a control valve, and the pump discharge amount is controlled by the pilot pressure of this pressure generation mechanism, the most downstream switching valve is provided upstream of the pressure generator groove. A logic valve is interposed in series with the pressure generation mechanism downstream of the center bypass passage via the pressure generator groove, and the pilot pressure generated between the logic valve and the pressure generator groove is guided for pump control. Hydraulic control device.