JP3137921B2 - Travel speed control circuit for construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling speed control circuit for a construction machine, and more particularly to a traveling speed control circuit having two variable displacement traveling motors, such as a hydraulic shovel, for controlling the discharge amount of a hydraulic pump by a pump regulator. The present invention relates to an adjustable traveling speed control circuit for a construction machine.

[0002]

2. Description of the Related Art FIG. 8 shows a hydraulic circuit of a conventional hydraulic shovel, in which first and second variable displacement hydraulic pumps 11, 1 are provided.
2, a switching valve 14 for a left traveling motor 13, a switching valve 15 for a swing motor, and a switching valve 16 for an arm cylinder are provided downstream of the first hydraulic pump 11. 12, a switching valve 19 for the right traveling motor 18 and a switching valve 2 for the boom cylinder
0 is provided. First and second hydraulic pumps 11,
Negative control (hereinafter referred to as “negative control”) throttles 21 and 22 are provided at the most downstream of each of the twelve, and the negative control pressure generated in the negative control throttles 21 and 22 is caused to act on the left and right pump regulators 23 and 24, respectively. And the discharge amount of the second hydraulic pumps 11 and 12 is controlled.

The right and left traveling motors 13 and 18 are provided with tilting angle adjusting cylinders 25 and 26, and the tilting angles of the traveling motors 13 and 18 are adjusted by a pilot pressure supplied from a hydraulic source 27. An electromagnetic valve 28 is provided in the pilot oil passage from the hydraulic pressure source 27, and the speed changeover switch 2
By turning on 9, a control signal is output from the controller 30 to the solenoid valve 28, and the solenoid valve 28 is switched from the position (a) to the position (b).

As shown in the figure, when the solenoid valve 28 is in the position (a), the ports of the tilt angle adjusting cylinders 25 and 26 have the tank pressure, and the tilt angles of the traveling motors 13 and 18 are large. is there. Therefore, by switching the traveling switching valves 14 and 19 to supply the discharge oil of the first and second hydraulic pumps 11 and 12 to the traveling motors 13 and 18, the traveling motors 13 and 18 are driven at a low speed. The aircraft moves forward or backward at low speed. To increase the traveling speed of the aircraft, the speed switch 29 is turned on and the solenoid valve 28 is turned on (b).
And the pilot oil is supplied to the tilt angle adjusting cylinders 25, 26 to change the tilt angles of the traveling motors 13, 18 to small.

[0005]

In recent years, the traveling speed of a hydraulic shovel has been set to be relatively high in order to move within a wide work site in a short time. In a narrow work site, to reduce the traveling speed, the inclination angle of the traveling motor is adjusted to a large value to reduce the rotation of the traveling motor, but if the traveling speed of the aircraft is to be reduced below that, the accelerator lever is required. To reduce the engine speed.

However, when the engine is running at a low speed, the operation of the work actuator is slowed down. Therefore, it is necessary to increase the engine speed again when performing work. Therefore, when the traveling and the work of the aircraft are repeated or when the traveling and the work are performed in a combined manner, the operation of the operator becomes extremely complicated.

On the other hand, when a mode switch for selecting a traveling mode is provided, and the mode switch is turned on to cause the vehicle to travel, the electromagnetic switching valve is switched to the open oil passage position, and the pilot pressure of the hydraulic source is changed to the pump pressure. A traveling speed limiting circuit configured to act on a regulator to limit the maximum discharge amount of a hydraulic pump is also known (actually disclosed in Japanese Unexamined Utility Model Publication No.
No. 6837).

However, the limiting circuit described in this publication is provided with a detector for operating the vehicle and a detector for operating the working actuator, and processes signals from these detectors to issue a command to the electromagnetic switching valve. Since a controller for turning the signal on and off is required, the cost for constructing the circuit increases.

In order to reduce the running speed of the construction machine, a control circuit capable of automatically lowering the running speed without adjusting the engine speed is constructed, and the control circuit is provided at a low cost. A technical problem to be solved arises, and an object of the present invention is to solve this problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above-mentioned object, and comprises a first and a second hydraulic pump of a variable displacement type, wherein each of the pump regulators is provided with a pilot pump. A discharge valve is controlled by applying pressure, a switching valve for one traveling motor and a switching valve for at least one work actuator are provided downstream of the first hydraulic pump, and a second hydraulic pump is provided. In a hydraulic circuit of a construction machine in which a switching valve for the other traveling motor and a switching valve for another work actuator are arranged downstream of
The switching valves for the two traveling motors are provided with an auxiliary valve for communicating the pilot oil of the pilot pump to the tank when the spool is in the neutral position, and for shutting off the pilot pump and the tank when the spool is switched. A throttle is provided between the auxiliary valve near the pilot pump and the pilot pump, and an oil passage is branched from the latter stage of the throttle to the maximum discharge amount restriction port of the pump regulator. And the solenoid valve can be switched in conjunction with the on / off operation of the ultra-low speed changeover switch. When the ultra-low speed changeover switch is on, the electromagnetic valve opens from a position where the oil passage is shut off. And the pilot pressure of the pilot pump is applied to the maximum discharge amount restriction port of the pump regulator to control the maximum discharge amount of the hydraulic pump. The speed control circuit of the arrangement the construction machine so as to there is provided.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a side view of a hydraulic excavator 40. An upper swing body 42 is mounted on a lower traveling body 41, and a boom 43, an arm 44, and a bucket 45 are attached to a front portion of the upper swing body 42, and a boom cylinder 46, Work actuators such as an arm cylinder 47 and a bucket cylinder 48 are mounted.

FIG. 2 is a circuit diagram of a traveling speed control circuit according to the present invention. The same components as those of the conventional circuit are denoted by the same reference numerals and description thereof is omitted. As shown in the drawing, the oil passage 52 from the pilot pump 51 is connected to the left and right traveling switching valves 14 and 1.
The tandem connection is made to the auxiliary valves 54 and 59 provided in 9. The switching valves 14,
When the spool No. 19 is in the neutral position, the oil passage 52 is opened and the pilot oil of the pilot pump 51 is stored in the tank 60.
Opening positions 54a, 59a for communicating with the pilot pump 51 and shutoff positions 54b, 54c, 59b, for closing the oil passage 52 and shutting off the pilot pump 51 and the tank 60 when the spool is switched to one of the left and right running positions. 59c.

A throttle 61 is provided between the pilot pump 51 and the auxiliary valve 59 near the pilot pump 51,
An oil passage 62 is branched from a stage subsequent to the throttle 61 to the maximum discharge amount restriction ports 23a, 24a of the pump regulators 23, 24. An electromagnetic valve 63 is provided in the middle of the oil passage 62, and an excitation circuit including an ultra-low speed changeover switch 64 and a power supply 65 is connected to a solenoid of the electromagnetic valve 63.

If the ultra-low speed changeover switch 64 is off, the solenoid valve 63 holds the position (c) and the maximum discharge amount restriction ports 23a, 24 of the pump regulators 23, 24.
Since a is the tank pressure, the first and second hydraulic pumps 1
The maximum discharge amounts of 1, 12 are not limited. That is, the discharge amounts of the first and second hydraulic pumps 11 and 12 can be varied from a minimum to a maximum according to the operation amount of each switching valve.

In the initial state shown in FIG. 2, the solenoid valve 28 is in the position (a) and the tilt angle adjusting cylinders 25, 26
Port becomes the tank pressure, and the tilting angles of the traveling motors 13 and 18 are large.
By switching 19 to the travel position, the aircraft will travel at low speed. In order to increase the traveling speed of the airframe, as shown in FIG. 3, the switching valves 14 and 19 for traveling are switched to the traveling position, and the speed switching switch 29 is turned on to move the solenoid valve 28 to the position (b). Switch. Even in this state, since the maximum discharge amount restriction ports 23a and 24a are tank pressures,
The maximum discharge amounts of the first and second hydraulic pumps 11 and 12 are not limited. Therefore, the tilt angle adjusting cylinders 25, 26
, The inclination angle of the traveling motors 13 and 18 is changed to a small value, and the traveling motors 13 and 18 are driven at a high rotation speed.

On the other hand, if the ultra-low speed switch 64 is turned on in the initial state shown in FIG. 2, as shown in FIG.
3 is switched from the position (c) to the position (d), and the oil passage 62 is opened. When the switching valves 15, 16, 26 for operations other than traveling are operated in this state, the pilot oil of the pilot pump 51 is moved to the open position 59 of the auxiliary valve 59.
a through the opening position 54a of the auxiliary valve 54 and the tank 60
, The maximum discharge amount restriction ports 23a and 24a of the pump regulators 23 and 24 become tank pressure, and the first and second hydraulic pumps 11 and 1 are connected in the same manner as described above.
2 is not limited. That is, the discharge amounts of the first and second hydraulic pumps 11 and 12 are controlled by the switching valve 1 for work.
It can be varied from the minimum to the maximum according to the operation amounts of 5, 16, and 26.

When one or both of the traveling switching valves 54 and 59 are switched to the traveling position in order to travel the body in this state, either one of the auxiliary valves 54 or 59 or both of the auxiliary valves 54 and 59 are switched. Spool is in open position 54a
(59a) to the blocking position 54b or 54c (59b or 59c). For example, as shown in FIG.
When the left and right traveling switching valves 14 and 19 are switched to the traveling position with the ultra low speed switch 64 turned on, the auxiliary valves 54 and 59 move to the shutoff positions 54b and 59b, and the pilot pump 51 and the tank 60 are moved. Is shut off.

For this reason, the pilot oil of the pilot pump 51 flows into the oil passage 62 from the latter stage of the throttle 61, passes through the position (d) of the solenoid valve 63, and passes through the pump regulator 2.
It is led out to the maximum discharge amount restriction ports 23a and 24a of the third and the fourth discharge amount. By applying pilot pressure to the maximum discharge amount restriction ports 23a and 24a, the maximum discharge amounts of the first and second hydraulic pumps 11 and 12 are restricted. That is, if the aircraft is run with the ultra low speed switch 64 turned on,
The flow rates of the traveling motors 13 and 18 are further reduced, and the aircraft enters an ultra-low speed running slower than a normal low speed running.

When any one of the operation switching valves 15, 16, and 20 is operated in order to carry out the operation while the body is running with the ultra-low speed switching switch 64 turned on, the switching valve 15, 16, When the pilot pressure applied to the valves 16 and 20 is detected, the straight travel valve 17 switches from the position (e) to the position (f). For example, when the switching valve 20 for the boom is operated, as shown in FIG. 6, the straight traveling valve 17 is switched to the position (F) with the operation of the switching valve 20, and the first hydraulic pump 11 Since the discharge oil is diverted to the left and right traveling motors 13 and 18, the traveling speed of the body is inevitably reduced by half.

Next, when the vehicle is stopped and the operation is performed with the ultra-low speed switch 64 turned on, the auxiliary valve is moved as the traveling switching valves 14 and 19 move to the neutral position. The valves 54, 59 return to the communication positions 54a, 59a,
The pilot pump 51 and the tank 60 communicate with each other, and the maximum discharge amount limiting port 23 of the pump regulators 23 and 24 is connected.
Since a and 24a are the tank pressures, the limitation on the maximum discharge amount of the first and second hydraulic pumps 11 and 12 is released. That is, working actuators such as the boom 43 and the arm 44 are operated at a predetermined high speed.

When the hydraulic excavator 40 works in a large work site, the ultra-low speed switch 64 is turned off and the speed switch 29 is turned on, as shown in FIG. As shown in FIG.
Holds the position (c), the maximum discharge amounts of the first and second hydraulic pumps 11 and 12 are not limited even if each switching valve is operated, and the tilt angles of the traveling motors 13 and 18 are small. , The work speed can be increased and the work can be performed efficiently.

In the present embodiment, the speed changeover switch 29 or the ultra-low speed changeover switch 6 provided in the excitation circuit is provided.
When the solenoid valve 28 is turned on, the solenoid is energized and the solenoid valve 28 or 63 is switched. As shown in FIG. To the speed switch 29 or the ultra-low speed switch 6
When the switch 4 is on, the controller 30 outputs a control signal to the solenoid valve 28 or 63 to switch the solenoid valve 28 to the position (b) or switch the solenoid valve 63 to the position (d). You can also.

Thus, the present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modifications.

[0024]

As described above, in the present invention, when the ultra-low speed switch is on, the solenoid valve is switched, and the pilot valve is connected to the maximum discharge amount limiting port of the pump regulator in conjunction with the operation of the switching valve for the traveling motor. Since the pressure acts, the maximum discharge amount of the hydraulic pump can be limited. Therefore, when the construction machine travels on a narrow work site, or when descending on a steep slope or loading on a trailer, the traveling speed can be automatically reduced without adjusting the engine rotation, In addition, an extremely low speed running slower than the normal low speed running becomes possible.

Further, it is not necessary to provide a controller for processing signals from the traveling operation detector and the work operation detector and for turning on and off a command signal to the solenoid valve based on the signals. No detector is needed,
Cost can be reduced when constructing the control circuit.

[Brief description of the drawings]

FIG. 1 is a side view of a hydraulic excavator according to an embodiment of the present invention.

FIG. 2 shows an embodiment of the present invention and is a traveling speed control circuit diagram in an initial state.

FIG. 3 shows the embodiment of the present invention and is a traveling speed control circuit diagram in a high-speed traveling state.

FIG. 4 shows the embodiment of the present invention, and is a traveling speed control circuit diagram when an ultra-low speed changeover switch is in an ON state.

FIG. 5 shows the embodiment of the present invention, and is a traveling speed control circuit diagram when a traveling switching valve is operated with an ultra-low speed switching switch being on.

FIG. 6 shows the embodiment of the present invention, and is a traveling speed control circuit diagram when a traveling switching valve and a work switching valve are combinedly operated with an ultra-low speed switching switch being on.

FIG. 7 shows another embodiment of the present invention, and is a driving speed control circuit diagram having a configuration in which a solenoid valve is controlled by a controller.

FIG. 8 is a hydraulic circuit diagram showing a conventional technique.

[Explanation of symbols]

 11, 12 Hydraulic pump 14, 19 (for traveling) switching valve 15 (for turning) switching valve 16 (for arm) switching valve 20 (for boom) switching valve 23, 24 Pump regulator 23a, 24a Maximum discharge amount restriction port 51 Pilot Pump 54, 59 Auxiliary valve 60 Tank 61 Throttle 62 Oil path 63 Solenoid valve 64 Ultra low speed switch

Claims (1)

(57) [Claims] A variable displacement type first hydraulic pump and a second hydraulic pump are provided. A pilot pressure is applied to each of the pump regulators to control a discharge amount, and a downstream side of the first hydraulic pump is provided. A switching valve for one traveling motor and a switching valve for at least one work actuator are provided, and a switching valve for the other traveling motor and a switching valve for another work actuator are provided downstream of the second hydraulic pump. In the hydraulic circuit of the construction machine disposed, the switching valves for both of the traveling motors communicate pilot oil of the pilot pump to the tank when the spool is in the neutral position, and when the spool is switched. An auxiliary valve for shutting off the pilot pump and the tank is provided.A throttle is provided between the auxiliary valve near the pilot pump and the pilot pump. The oil passage to the maximum discharge amount restriction port of the pump regulator is branched, and a solenoid valve is interposed in the middle of the oil passage, and the solenoid valve can be switched in conjunction with the on / off operation of the ultra-low speed changeover switch. When the low-speed changeover switch is on, the solenoid valve switches from a position where the oil passage is shut off to a position where the oil passage is opened, and the pilot pressure of the pilot pump is applied to the maximum discharge amount limiting port of the pump regulator to cause the hydraulic pump to operate. A travel speed control circuit for a construction machine, wherein the travel speed control circuit is configured to limit a maximum discharge amount.