JP2675066B2 - Hydraulic circuits for civil engineering and construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a natural lowering (spool) of a hydraulic actuator (boom, arm, etc. of a power shovel) for holding the addition of civil engineering and construction machinery when the directional control valve is in the neutral position. Hydraulic circuit for preventing pressure oil leaks from the land portion of the.

[Conventional technology]

The conventional hydraulic circuit for civil engineering and construction machinery is shown in FIG. That is, in FIG. 6, the pressure oil discharged from the hydraulic pumps 31a and 31b is supplied to the combined control valves 32a and 32b. Directional switching valves 33, 34, 35a, 35
The arm cylinder 38, the turning motor 39, the left traveling motor 40a, the right traveling motor 40b, the boom cylinder 41, and the bucket cylinder 42 are connected to b, 36, and 37, respectively, and each of the directional switching valves is connected. When operated, the corresponding actuators are activated. Reference numerals 43a and 43b indicate main relief valves, which operate to prevent abnormal high pressures of the hydraulic pumps 31a and 31b. Further, reference numerals 44a, 44b, 45a, 45b, 46a, 46b represent overload relief valves, and further reference numerals 47a, 47b, 48a, 48b, 49.
Reference numerals a and 49b denote make-up valves. The former is provided at a necessary place for protecting the actuator and the latter is provided at a necessary place for preventing cavitation, and they are arranged in the combined control valves 32a and 32b, respectively.

[Problems to be solved by the invention]

In recent years, however, the hydraulic circuit for civil engineering and construction machinery has become higher in pressure, which tends to increase the load pressure for holding each actuator when the switching valve is neutral.

However, the structure of the conventionally known switching valve is as shown in FIG. 4 when the directional switching valve 36 used in the hydraulic circuit of FIG. 6 is enlarged and shown. Therefore, in the direction switching portion 36 shown in FIG. 4, the location for preventing the pressure oil leak is the valve body 54 and the land portion 56 of the spool 55. Need and
Due to this gap, there was a limit to preventing pressure oil leak.

As a solution in this case, it is proposed to provide a pilot check valve between the boom cylinder 41 and the directional control valve 36 in FIG. 6, but in this case, the installation location of the overload relief valves 45a, 45b. Is a problem. That is, by installing the pilot check valve, it is necessary to provide the overload relief valves 45a and 45b between the boom cylinder 41 and the pilot check valve. However, the structure of the conventionally known directional control valve is, as shown in FIG. 4, overloaded relief valves 45a, 45a in the valve body 54.
Since the location where b is arranged and where pressure oil leak prevention is required is not for all directional control valves of the combined control valves 32a, 32b, a pilot check valve is installed in the valve body 54. With the structure, there is a problem that the portion of the directional control valve that does not require the pilot check valve unnecessarily lengthens. On the other hand, if the pilot check valve is installed outside the valve main body 54 only for the direction switching valve K that requires it, an overload relief valve and another tank passage are also installed outside the pilot check valve. However, there is a problem that the cost is increased. Further, as described above, by installing the overload relief valve between the actuator and the pilot check valve,
Strictly speaking, pressure oil leak from the overload relief valve itself cannot be prevented.

Therefore, an object of the present invention is to install a pilot check valve between an actuator and a directional switching valve in order to prevent pressure oil leakage of the directional switching valve as the hydraulic circuit for civil engineering / construction machinery is increased in pressure. The overload relief valve and the tank passage are located inside the valve body as before, and a pilot check valve is installed outside the valve body only for the directional control valve that needs to prevent pressure oil leakage. (EN) It is an object to provide a hydraulic circuit for civil engineering / construction machinery, which can effectively prevent a pressure oil leak.

[Means for solving the problem]

A hydraulic circuit for civil engineering and construction machinery according to the present invention includes a hydraulic pump (31a, 31b), an arm actuator (38) driven by pressure oil from the hydraulic pump, a boom actuator (41), and a bucket actuator ( 42)
A direction switching valve (33, 36, 37) for controlling the direction and flow rate of the pressure oil supplied from the hydraulic pump to the actuators, and the actuators for preventing any of the actuators from spontaneously descending. In the hydraulic circuit for civil engineering / construction machinery, which includes a pilot check valve provided together with an overload relief valve (44a, 44b, 45a, 45b, 46a, 46b) between each directional control valve that controls this and A first pilot check connected to the valve opening / closing signal line (Px) via the slow return valve (14) between one side of the arm actuator (38) and the overload relief valve (44a) of the arm actuator. A valve (12) is provided, and a slow retarder is provided between one side of the boom actuator (41) and the boom actuator overload relief valve (45a). A valve opening / closing signal line (Px) for opening / closing each pilot check valve (12, 13) by providing a second pilot check valve (13) connected to the valve opening / closing signal line (Px) via a valve (15). ) Is provided with a pilot pump (16) for supplying a signal pressure, and the opening / closing signal line (Px) is branched into two directions, one of which is used for opening / closing each of the corresponding directional control valves (33, 36). , The first pilot pilot and the second pilot pilot via the slow return valve (14, 15) which is set to operate faster than the actuator when opened and delay to operate the overload relief valve with priority when closed. The check valves (12, 13) are connected so as to operate, and the other branched valve opening / closing signal line (Px) controls each directional switching valve (3) that controls each actuator (38, 41, 42).
Selector valve (17,18,1)
9) is connected to the tank (50) so as to circulate, and when the directional control valves (33, 36, 37) are in a neutral state, the selector valves (17, 18, 19) are opened, The circuit is constructed so that the signal pressure supplied from the pilot pump (16) is unloaded to close the pilot check valves (12, 13) to surely prevent leakage of pressure oil, and the direction of When the switching valve is operated, the corresponding selector valve is closed to increase the signal pressure of the one signal line, and the pilot check valve (12, 13) is opened before starting the operation of the corresponding actuator to smooth the operation. It is characterized in that the circuit is configured to perform oil passage.

[Action]

The operation of the hydraulic circuit for civil engineering / construction machinery according to the present invention will be described with reference to the civil engineering / construction machinery shown in FIG.
In FIG. 5, the arm cylinder 38, the boom cylinder 41, and the bucket cylinder 42 are respectively denoted by the same reference numerals as those shown in the hydraulic circuit diagram in FIG. 6, and these are the arm 51, the boom 52, and the bucket. It is configured to operate each of the 53 actuators.

The problem here is, for example, the boom 52 and the arm.
It is the amount of pressure oil leak of 51. However, the pressure oil leak amount becomes a problem when the directional control valves for the actuators of the arm 51, the boom 52, and the bucket 53 are all in the neutral state and the load is maintained in the air. However, when any one of the above-mentioned actuators is operated, it does not cause a serious problem in use as well as in appearance.

The overload relief valve operates when a large external force is applied when the actuator is at rest (when the directional control valve is neutral). In most cases, the external force is different from that of the machine itself. Or the impact load when the operation of the actuator itself is suddenly stopped (when the directional control valve is rapidly returned to the neutral state).

Therefore, as shown in FIG. 5, assuming that the bucket 53 is in contact with the ground and the arm directional control valve 33 (FIG. 6) is stopped in the neutral state, the boom 52 is lowered (for the boom). When the boom direction switching valve (FIG. 6) is operated in the direction in which the cylinder 41 contracts, an external force acts in the direction in which the arm cylinder 38 extends due to its own weight as the vehicle body tries to lift up. At this time, since the arm directional control valve 33 is in the neutral state, if the holding pressure becomes higher than the set pressure of the overload relief valve due to the external force due to its own weight, the overload relief valve 44a (the 6
(Figure) operates. By operating the boom 52 in this manner, the overload relief valve on the arm 51 side operates.

In this case, in the hydraulic circuit of the present invention, the time for which the check valve function operates is delayed by an external force generated by another actuator of the machine itself and an abnormally high pressure due to an impact load when the actuator itself is suddenly stopped. (The operating time of the overload relief valve is several seconds), and by providing the pilot check valve that enables the operation of the overload relief valve, it is possible to prevent the pressure oil leak when the directional control valve is in the neutral position.

〔Example〕

Next, an embodiment of a hydraulic circuit for civil engineering and construction machinery according to the present invention will be described in detail below with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional hydraulic circuit shown in FIG. 6 are designated by the same reference numerals.

FIG. 1 shows an embodiment of a hydraulic circuit for civil engineering and construction machinery according to the present invention. In FIG. 1, reference numerals 12,1
Reference numeral 3 denotes a pilot check valve, and the pilot check valves 12 and 13 are provided on the rod side of the arm cylinder 38 and the bottom side of the boom cylinder 41. The valve opening / closing signal lines Px for the pilot check valves 12 and 13 are provided with slow return valves 14 and 15, respectively.
The opening and closing of the corresponding directional control valves 33 and 36 are set to be early when opened and to be delayed when closed.

A pilot pump 16 is provided for the valve opening / closing signal pressure of the pilot check valves 12 and 13. The pressure oil supplied from the pilot pump 16 passes through the throttle 21 and the selector valves 17, 18 and 19 interlocking with the directional switching valves 33, 36 and 37 for arms, booms and buckets, respectively, and then to the tank 50. Is set to return to. Further, the pressure oil supplied from the pilot pump 16 is kept at a constant pressure (usually 30 to 40 kgf / cm ² ) by the relief valve 20, and the pilot check valves 12, 13 are provided from the downstream of the throttle 21 via the valve opening / closing signal line Px. Have been led to. The selector valves 17, 18, 19 which are interlocked with the respective directional control valves 33, 36, 37 are switched ON / OFF at an early point in the middle of their strokes, and the timing is the respective directional control valves 33, 36, 37. It is set to a point before the passage leading from the cylinder port to the tank 50 is opened.

Now, if the directional control valves 33, 36, 37 for arms, booms, and buckets are in the neutral state, the directional control valves 33, 3
Since the selector valves 17, 18, 19 which are interlocked with 6,37 are open, the pressure oil supplied from the pilot pump 16 is
Since it is unloaded and the pressure is low, the pressure in the valve opening / closing signal line Px also becomes low, and the pilot check valves 12 and 13 are closed, so that the leak is surely prevented.

Next, when the arm directional control valve 32 is operated, the selector valve 17 is interlocked to close the pressure oil supplied from the pilot pump 16, so that the pressure of the valve opening / closing signal line Px rises and the pilot check valves 12 and 13 are closed. open. Since this timing is before the passage from the cylinder port of the direction switching valve 33 to the tank 50 is opened, oil can be passed from the rod side of the arm cylinder 38 to the tank 50 without resistance. At this time, the pilot check valve 13 on the boom cylinder 41 side also opens, but not only does it pose a big problem as described above, but it also prevents the boom overload relief valves 45a and 45b from operating due to arm operation. There is no hindrance.

Although the bucket cylinder 42 is not provided with a pilot check valve, when the bucket directional control valve 37 is operated, the selector valve 19 is used for operating the overload relief valves 45a and 45b. The pilot check valves 12 and 13 are provided so as to open. Note that, in practice, the pilot pressure selector valve may be provided in the turning direction switching valve 34. Further, as described above, the slow return valves 14 and 15 cause the directional control valve to operate quickly when opened and when there is a time delay when closed when opening and closing the directional control valve.

FIG. 2 shows an embodiment of the pilot check valve in FIG. In FIG. 2, when the pressure of the valve opening / closing signal line Px becomes high when the pilot check valve is released (for example, the relief setting pressure is set to 30 to 40 kgf / cm ² ), the piston 22 is pushed up and the pilot poppet valve 23
Push up. In this case, if the pressing area of the piston 22 is set to about 10 times the pilot poppet seat diameter (3 times the diameter), the pilot will work even when the cylinder load pressure is 300 to 400 kgf / cm ² (approximately the maximum hydraulic circuit pressure used). The poppet valve 23 can be released. When the pilot poppet valve 23 is released, the pressure in the main poppet spring chamber 24 drops and the main poppet 25 opens. In this case, the oil discharged from the pilot poppet valve 23 is discharged to the cylinder port 26 side of the directional control valve (at this time, the passage from the actuator port of the directional control valve to the tank is blocked). There is no momentary descent. However, the main poppet
The orifice 27 provided in 25 does not cause a response delay in the free flow direction, and the pilot valve poppet 23
It is necessary to design so that the pressure in the main poppet spring chamber 24 will drop sufficiently when opening the. Further, when the oil flows from the cylinder port 26 of the directional control valve to the actuator, the pressure of the cylinder port 26 acts on the main poppet spring chamber 24 so that the pilot check valve does not open so that the pilot poppet valve 23 does not open. A check valve 28 is provided in the passage.

FIG. 3 shows a modification of the pilot check valve shown in FIG. That is, in this example, the basic structure of the pilot check valve is the same as that of the embodiment shown in FIG. 2, and therefore, the same components are designated by the same reference numerals and detailed description thereof will be omitted. However, the present embodiment is characterized in that the pressure switch 29 and the timer 30 are used to set the opening / closing of the pilot check valve so that the pilot check valve operates quickly when opened and delays when closed.

〔The invention's effect〕

As is apparent from the above-described embodiments, according to the present invention, it is possible to reliably prevent pressure oil leakage due to the load pressure of the actuator, and further, to provide the overload relief valve at the position of the conventional composite control valve. In addition, the pilot check valve can be easily installed only in a necessary place.

That is, according to the present invention, against an abnormal high pressure due to an external force generated by another actuator of the machine itself and an impact load when the actuator itself stops suddenly,
By providing the pilot check valve that enables the operation of the overload relief valve, it is possible to effectively prevent the pressure oil leak when the direction switching valve is in the neutral position.

Therefore, according to the hydraulic circuit of the present invention, it is possible to effectively prevent the pressure oil leak against the high pressure of the hydraulic circuit, and to greatly improve the performance of various civil engineering / construction machines to which the hydraulic circuit is applied.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention. is there.

[Brief description of the drawings]

FIG. 1 is a hydraulic system diagram showing an embodiment of a hydraulic circuit for civil engineering / construction machinery according to the present invention, and FIG. 2 is a main part showing an example of a configuration of a pilot check valve used in the hydraulic circuit shown in FIG. 3 is a structural sectional view, FIG. 3 is a structural sectional view of an essential part showing a modified example of the pilot check valve in FIG. 2, FIG. 4 is an essential sectional view of a directional control valve arranged in a combined control valve, and FIG. FIG. 6 is a schematic explanatory view showing a structural example of a civil engineering / construction machine to which the hydraulic circuit according to the present invention can be applied, and FIG. 6 is a hydraulic system diagram of a conventional civil engineering / construction machine hydraulic circuit. 12,13 …… Pilot check valve 14,15 …… Slow return valve 16 …… Pilot pump 17,18,19 …… Selector valve 20 …… Relief valve, 21 …… Throttle 22 …… Piston, 25 …… Main poppet 23 ...... Pilot poppet valve 24 …… Main poppet spring chamber 26 …… Cylinder port, 27 …… Orifice 28 …… Check valve, 29 …… Pressure switch 30 …… Timer, 31a, 31b …… Hydraulic pump 33,34,35a , 35b, 36,37 …… Direction switching valve 38 …… Cylinder for arm 41 …… Cylinder for boom 42 …… Cylinder for bucket 44a, 44b, 45a, 45b, 46a, 46b …… Overload relief valve 47a, 47b, 48a, 48b, 49a, 49b …… Makeup valve 51 …… Arm, 52 …… Boom 53 …… Bucket, 54 …… Valve body 55 …… Spool, 56 …… Land Px …… Valve opening / closing signal line

Claims (1)

(57) [Claims] 1. A hydraulic pump (31a, 31b), an arm actuator (38) driven by pressure oil from the hydraulic pump, a boom actuator (41) and a bucket actuator (42), and the hydraulic pump. Directional switching valves (33, 36, 37) for controlling the direction and flow rate of the pressure oil supplied to the actuators, and the actuators for controlling the actuators in order to prevent the actuators from spontaneously descending. Overload relief valve (44a, 44b, 45a, 45b, 46a, 46b) between directional valve
In a hydraulic circuit for civil engineering / construction machinery, which comprises a pilot check valve provided together with the pilot check valve, a slow return valve (44a) is provided between one side of the arm actuator (38) and the overload relief valve (44a) of the arm actuator. The first pilot check valve (12) connected to the valve opening / closing signal line (Px) via the (14) is provided, and one side of the boom actuator (41) and the overload relief valve (45a) of the boom actuator are connected. A second pilot check valve (13) connected to the valve opening / closing signal line (Px) via the slow return valve (15) is provided between the valve and the valve opening / closing for opening / closing each pilot check valve (12, 13). A pilot pump (16) for supplying a signal pressure to the signal line (Px) is provided, and the valve opening / closing signal line (Px) is branched into two and one of them is connected. When opening and closing the corresponding directional control valves (33, 36) respectively, the slow retan valve is set so that it operates faster than the actuator when open and delays so that the overload relief valve operates preferentially when closed. The first and second pilot check valves (12, 13) are connected to each other via valves (14, 15) so as to operate, and the other branched valve opening / closing signal line (Px) is connected to each actuator ( 38,41,42) directional control valves (33,3)
Selector valves (17,18,19) interlocking with 6,37)
When the directional valves (33, 36, 37) are in the neutral state,
The selector valves (17, 18, 19) are opened, the signal pressure supplied from the pilot pump (16) is unloaded, and the pilot check valves (12, 13) are closed to ensure pressure oil leakage. In addition to configuring the circuit to prevent it, when any of the directional control valves is operated, the corresponding selector valve closes to increase the signal pressure of the one signal line, and before the operation of the corresponding actuator starts. ,
A hydraulic circuit for civil engineering and construction machinery, which has a circuit configuration that opens the pilot check valves (12, 13) to allow smooth oil passage.