JPH01176807A - Speed control circuit of construction equipment - Google Patents

Abstract

PURPOSE:To simultaneously perform maximum discharge amount regulating paired-off hydraulic pumps by shortening each positive control circuit by means of a short circuit pipe line in order to prevent a backflow, and providing a pressure regulator on the short circuit pipe line. CONSTITUTION:Positive control pipe lines 12a, 12b are shortened by a short circuit pipe line 18 on the way of which line check valves 19a, 19b are provided. A flowout pipe line 20 communicated with an oil tank is formed from the short circuit pipe passage 18, between the check valves 19a and 19b, while a relief valve 21 capable of adjusting pressure is arranged on the flowout pipe line 20. Maximum discharge amounts of hydraulic pumps 2a, 2b at the time of tilting levers 17a, 17b in a full-stroke are regulated accordingly, just by adjusting a set pressure of the relief valve 21, so that the maximum speed setting of hydraulic motors 4a, 4b are simultaneously performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a speed control circuit for a construction machine, such as a crawler crane, which has a hydraulic circuit for traveling and hoisting.

[Prior Art] In general, construction machinery involves work that is performed by driving two hydraulic motors either synchronously or individually. For example, in a crawler crane, the left and right crawlers are driven by two corresponding hydraulic motors. They travel by being individually driven by hydraulic motors.

Conventionally, such a hydraulic circuit for traveling has generally been used as shown in FIG. 2. engine 1
Hydraulic motors 4a, 4b are connected to the discharge sides of variable displacement hydraulic pumps 2a, 2b driven by the hydraulic motors 4a, 4b via four-point, one-three-position pilot type directional control valves 3a, 3b, respectively.

Pilot pipes 7a and 8a are connected to the pressure receiving parts 5a and 6a of the directional switching valve 3a, respectively.

A remote control valve 10a connected to the control hydraulic line 9 is connected to the remote control valve 8a, and similarly, pilot pipes 7b and 8b are connected to the pressure receiving parts 5b and 6b of the directional control valve 3b, respectively. A remote control valve fo connected to the control hydraulic line 9 is connected to the pipes 7b and 8b.
b is connected. There are pilot pipes 7a, 8a in the middle of the pilot pipes 7a, 8a and 7b, 8b.
A check block Ha whose inlet side is connected to the pilot pipes 7b and a check block Llb whose inlet side is connected to the pilot pipes 7b and 8b are provided, respectively.
The outlet sides of a and Ilb are connected to pump regulator L3a, via positive control lines 12a and 12b, respectively.
13b positive control port. The pump regulators 13a, tab are for adjusting the discharge amount of the hydraulic pumps 2a, 2b, and are negative control pipes 15a branched from the discharge side pipes 14a, 14b of the hydraulic pumps 2a, 2b.

15b is connected to both negative control ports of pump regulators 13a and 13b. Furthermore, the positive control conduit 12a.

12b, the positive control conduit 12
A pressure reducing valve 16a that individually adjusts the pressures of a and 12b.

Each tab is provided in the middle of the pipe.

When operating a crawler crane or the like equipped with such a hydraulic circuit, the operator must turn on the remote control valve LO.
a, lOb operating levers 17a.

When 17b is tilted in the direction of the arrow, for example, hydraulic pressure corresponding to the tilting of the operating levers 17a and L7b is output to the pilot pipes 7a and 7b, respectively, and the hydraulic pressure is applied to the pressure receiving parts 5a and 5b.
As a result, the directional control valves 3a and 3b are respectively switched to position 8. At the same time, the pilot pipes 7a, 7
The hydraulic pressure output to b is checked by check blocks lla and l.
Positive control line L2a, 1 via lb
2b to pump regulators 13a, 13b and are individually regulated pressure reducing valves 16a.

Pump regulator 13a within the set pressure range of lBb.

tab, and the pump regulators 13a, 13
The discharge amount of the hydraulic pumps 2a and 2b is adjusted by b,
The hydraulic motors 4a, 4b rotate in the direction of the arrow at a speed corresponding to the discharge amount. Note that the discharge pressure of the hydraulic pumps 2a and 2b is controlled by a negative control line 15a.

15b to the negative control ports of the pump regulators 13a, 13b, thereby controlling the constant horsepower of the hydraulic pumps 2a, 2b.

Further, if the operating levers 17a, 17b are tilted in the opposite direction of the arrow, the directional control valves 3a, 3b are switched to position B, and the remote control valve 10 is moved in the same manner as described above.
The control oil pressure of a and 10b is pump regulator 13a,
13b acts on the positive control lines 12a, L2b, and the hydraulic motors 4a, 4b are reversed.

In this way, by the driver adjusting the set pressures of the pressure reducing valves 16a and 1Bb individually as appropriate, the operating lever 17a
, 17b are tilted to full stroke, the maximum discharge amount of the hydraulic pumps 2a, 2b is limited, and the hydraulic motors 4a,
4b, respectively, and set the maximum speed of the hydraulic motors 4a, 4b.
It is designed to drive the left and right crawlers.

In addition, a main winch that lifts and lowers packets, opens and closes, etc.
A hydraulic circuit similar to that shown in FIG. 2 is used for the auxiliary winch.

[Problem to be solved by the invention] However, as described above, there are two pressure reducing valves 16a.

If the driver adjusts the set pressure of 1Bb separately during work, it is cumbersome to operate, and the pressure reducing valves lea,
It is difficult to completely match the discharge amounts of the hydraulic pumps 2a and 2b determined by the set pressure of tab, and a difference may occur in the discharge pressures. In this case, the operating levers 17a, 17b
When traveling with both hydraulic motors 4a and 4b tilted at full stroke, there is a problem in that the speed cycle of both hydraulic motors 4a, 4b cannot be maintained, resulting in meandering due to the speed difference between the left and right crawlers.

In addition, when the main hoisting winch and auxiliary hoisting winch are driven by the above-mentioned hydraulic circuit, simultaneous hoisting work of the main hoisting and auxiliary hoisting winches,
If synchronization could not be achieved, this would result in a speed difference between the wire ropes, causing problems such as gaps in the packets that were being hoisted.

In view of these circumstances, the present invention aims to provide a speed control circuit for construction machinery that can simultaneously adjust the maximum discharge amount of a set of two hydraulic pumps and improve operability.

[Means for Solving the Problems] The present invention comprises a set of two variable displacement hydraulic pumps and a hydraulic motor driven to rotate by the discharge oil of each of the hydraulic pumps. At the same time, by operating the respective remote control valves, control pressure oil is guided to the positive control line of the pump regulator of each of the hydraulic pumps, and the hydraulic oil is In a speed control circuit of a construction machine that adjusts the discharge amount of a pump and controls the rotational speed of each of the hydraulic motors, each of the positive control pipes is short-circuited to each other by a shuttle function valve in a short-circuit pipe to prevent backflow. , an adjustable pressure regulator is provided between the shuttle function valves in the short circuit line.

[Function] Therefore, by just adjusting the pressure of one pressure regulator, the maximum discharge amount of each hydraulic pump is adjusted at the same time, and the maximum speed setting of each hydraulic motor is also performed at the same time.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 1, the same reference numerals as in FIG. 2 indicate the same parts.

As shown in FIG. 1, the positive control conduit 12a
, 12b are short-circuited in the short-circuit conduit 18, and the short-circuit conduit 1
A check valve L9a is provided in the middle of the positive control line 12a to allow pressure oil to flow only from the positive control line 12a side to the positive control line L2b side. The positive control line 12 on the side
A check valve 19b is provided that allows pressure oil to flow only from the b side to the positive control pipe 12a side.

An outflow pipe 20 leading to the oil tank is provided between the check valves 19a and 19b, branching off from the short circuit pipe 18, and a pressure-adjustable relief valve 21 is provided in the outflow pipe 20.
will be established. Furthermore, the positive control line 12
a, 12b and check block lla,
llb, orifices 22a, respectively.

22b is provided. Each orifice 22a, 22b is
The pump regulator 1 has a required passage area.
The hydraulic pressure of the pressure oil flowing into the positive control ports of pump regulators 13a and 13b
The value is sufficient to control the

Next, the operation of this embodiment will be explained.

When the driver tilts the operating levers 17a and 17b of the remote control valves 10a and 10b by a full stroke in the direction of the arrow, the hydraulic pressure of the control hydraulic line 9 acts to the maximum on the pilot pipes 7a and 7b, respectively, and the direction is changed. Valve 3a
, 3b are switched to position A, and the hydraulic pressure acts on the positive control lines 12a, 12b via the check blocks ILa, Ilb. At this time,
Since the resistance of the positive control conduits 12a, 12b is increased by the orifices 22a, 22b, the hydraulic pressure acting on the positive control conduits 12a, 12b is kept to the minimum level necessary to control the pump regulators 13a, 13b. limited to.

The pressure oil that has passed through the orifices 22a, 22b is diverted to the short-circuit pipe 18, and after passing through the check valves 19a, 19b,
It flows into the outflow pipe 20. Here, when the operator adjusts the set pressure of the relief valve 21, the pressure in the positive control pipes 12a, 12b is maintained at the set pressure, and the pump regulators L3a, 13b operate the hydraulic pumps 2a, 2b to the maximum level. The discharge amount is limited, and the hydraulic motors 4a, 4b rotate in the direction of the arrow at a speed corresponding to the maximum discharge amount. Incidentally, even when the relief valve 21 operates at the set pressure, orifices 22a and 2 are provided in the positive control conduits 12a and 12b upstream of the short-circuit conduit 18, respectively.
2b, the pilot pipe 7a,
The pressure inside the operating lever 17a is not reduced.
.

The hydraulic pressure is maintained in accordance with the amount of tilting of 17b. Also, for example, when only one remote control valve LOa is operated, the pressure oil that has passed through one check valve L9a is
It is blocked by the other check valve 19b and does not flow into the other positive control conduit 12b.

Regarding the rotation of the hydraulic motors 4a, 4b in the direction opposite to the arrow, the maximum speed of the hydraulic motors 4a, 4b is set in the same manner as described above by tilting the operating levers 17a, L7b in the direction opposite to the arrow.

In this way, when the driver only adjusts the set pressure of one relief valve 21, the maximum discharge amount of the hydraulic pumps 2a, 2b when the operating levers Ha, 17b are tilted to a full stroke is limited, and the hydraulic motors 4a, 4b can be set at the same time, when the left and right crawlers are driven by the aforementioned hydraulic circuit to travel, it is possible to prevent meandering caused by the speed difference between the left and right crawlers. On the other hand, when the above-mentioned hydraulic circuit is used for hoisting the main hoist and auxiliary hoist winches, it is possible to prevent the packet from opening during hoisting, which occurs due to the speed difference of each wire rope when the main hoist and auxiliary hoist winches simultaneously hoist. .

Incidentally, instead of the relief valve 21, it is also possible to use a pressure regulator such as a pressure reducing valve, a sequence valve, a throttle valve, etc., and the pair of check valves 19a.

In place of 19b, each positive control conduit 12a,
It is also possible to use a shuttle function valve that irreversibly shorts 12b to each other. Furthermore, in the above embodiment, two check valves are used as check blocks lla and llb, respectively.
Although the check blocks 11a and 11b are opposed to each other, it goes without saying that one shuttle valve may be used for each of the check blocks 11a and llb. In addition, instead of using the hydraulic pressure in the control hydraulic line 9 as pilot pressure to switch the directional control valves 3a and 3b, the remote control valve 10a and the fob operating lever 1 are used instead.
7a.

The tilting operation of the directional control valves 17b can be performed mechanically using a link mechanism or the like or electrically using a micro switch or the like.
Alternatively, the directional control valves 3a and 3b may be switched.

[Effects of the Invention] As described above, according to the present invention, the maximum discharge amount of each hydraulic pump can be adjusted simultaneously by adjusting the pressure of one relief valve, that is, the maximum speed of each hydraulic motor can be set at the same time, resulting in improved operability. In addition to this, an excellent effect can be achieved in that it is possible to prevent meandering during travel, opening of the packet during winding, etc.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram showing a conventional example. 2a, 2b are hydraulic pumps, 3a, 3b are directional valves, 4
a, 4b are hydraulic motors, 9 is a control hydraulic line, and 10a. 10b is a remote control valve, L2a and L2b are positive control lines, 13a and '13b are pump regulators, 18 is a short circuit line, and 21 is a relief valve.

Claims (1)

[Claims] 1) Equipped with a set of two variable displacement hydraulic pumps and a hydraulic motor driven to rotate by the discharge oil of each hydraulic pump,
At the same time, the directional control valve on the discharge side of each of the hydraulic pumps is switched by operating a remote control valve, and at the same time, the control pressure oil is transferred to the positive control pipe of the pump regulator of each of the hydraulic pumps by operating the remote control valve. In a speed control circuit of a construction machine that adjusts the discharge amount of each of the hydraulic pumps and controls the rotational speed of each of the hydraulic motors, each of the positive control pipes is connected to each other by a shuttle function valve through a short-circuit pipe. 1. A speed control circuit for construction machinery, characterized in that the circuit is short-circuited to prevent reverse flow, and an adjustable pressure regulator is provided between a shuttle function valve in the short-circuit conduit.