JP2005076683A - Hydraulic pump output control circuit of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit obtainable of sufficient traveling speed at the time of climbing and applicable to a hydraulic circuit with one or two hydraulic pumps. <P>SOLUTION: The hydraulic circuit of a construction machine selects set torque of the hydraulic pump among a plurality of work modes and allows operation of the work machine at the set torque of the selected mode. A means for detecting traveling operation is provided. When the traveling operation is detected by the detection means during working in one of the work modes, the set torque is increased so that a power control staring pressure of the hydraulic pump agrees with a power control staring pressure in a maximum set torque mode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to the technical field of an output control device for a hydraulic pump in a construction machine such as a hydraulic excavator. More specifically, the present invention relates to a hydraulic pump output control circuit in uphill traveling.

A construction machine such as a hydraulic excavator may be required to climb a slope with a certain slope. Therefore, these construction machines are provided with an output control circuit of a hydraulic pump that can climb the engine without falling into an overload state. As an example of such a hydraulic circuit, there is a hydraulic circuit described in Patent Document 1 (FIG. 5). This hydraulic circuit (hereinafter referred to as the conventional circuit 1) is a hydraulic circuit in which the output of the hydraulic pump is increased only during traveling single operation to prevent engine overload and to improve the climbing ability. The outline of this circuit will be described below.
Japanese Patent Laid-Open No. 200-317471

  A specific configuration is shown in FIG. 5, and the gist of the configuration of the present invention is as follows. That is, left and right traveling hydraulic motors (not shown), an upper swinging body hydraulic motor (not shown), and a front working machine drive hydraulic cylinder (not shown) are provided. In order to supply oil, the engine 30, at least three or more (four) variable displacement hydraulic pumps 32 to 35 driven by the engine 30, and each of these hydraulic pumps 32 to 35 are connected to each other. The hydraulic excavator is provided with control valve units 36 to 39 in which the direction switching valves are unitized, and one of the three or more control valve units 36 to 39 has a left or right control valve unit 38. There is provided a first traveling switching valve for controlling driving of one of the traveling hydraulic motors, and another control valve unit. 9 is provided with a second travel switching valve for controlling driving of either the left or right traveling hydraulic motor, and pilot valves 44, 45 for operating these left and right traveling hydraulic motor operating pilot valves 46 and other hydraulic actuators. The pressure detection means 47 and 48 are provided to generate pressure on the pilot valve 46 side for operating the traveling hydraulic motor, and no pressure is generated on the pilot valves 44 and 45 side for operating other hydraulic actuators. When the detection means 49, 50 detect this, the output torque of each of the hydraulic pumps 32-35 is increased by the horsepower increase means 52a-55a.

  In the above-described conventional circuit 1, (1/4) of the total output torque of the engine 30 acts on each of the hydraulic pumps 32 to 35 when the traveling operation and the operation of the working machine are performed, and the entire output is performed during the traveling single operation. (1/2) of the torque acts. However, this conventional circuit 1 has a problem that, for example, when the pressure detection means 48 is not operating normally, the engine 30 is overloaded, causing a failure. There is also a problem that it cannot be applied to a hydraulic excavator provided with only two hydraulic pumps.

  Also, in a conventional hydraulic excavator, etc., a plurality of work modes such as a heavy excavation mode (H mode), a standard mode (S mode), and a finishing mode (L mode) are prepared, and an operator can respond to the work. Some of them are equipped with a hydraulic circuit (referred to as the conventional circuit 2) that can be selected from the above modes. This is configured to change the engine speed by changing the input shaft torque of the hydraulic pump (also referred to as the set input torque of the hydraulic pump, hereinafter simply referred to as the set torque) in accordance with the mode. is there. FIG. 6 shows a characteristic curve of the hydraulic pump of the conventional circuit 2.

  In the conventional circuit 2, the horsepower control start pressure of the hydraulic pump (referred to as pump discharge pressure when the output horsepower of the hydraulic pump becomes a constant horsepower) changes to P1, P2, and P3 depending on the H mode, S mode, and L mode. The set torque of the hydraulic pump also changes from Tmax to Tmin. However, in the conventional circuit 2, the mode is not automatically changed even when the traveling operation is started. Therefore, when the S mode, particularly the L mode is selected, there is a problem that the traveling speed is suddenly reduced when traveling from a flat ground to a steep uphill traveling unless the mode selection is changed. Further, it is troublesome to change the mode selection during traveling, and there is a problem in traveling work.

In the conventional circuit 1, when the pressure detection means 48 does not operate | move normally, the engine 30 will be in an overload state and there exists a subject that it causes a failure. There is also a problem that it cannot be applied to a hydraulic excavator provided with only two hydraulic pumps. Further, in the conventional circuit 2, when the S mode, particularly the L mode is selected, unless the mode selection is changed, there is a problem that the traveling speed is drastically reduced when traveling from a flat ground to a steep uphill traveling. It was.
The present invention has been made in view of the above-described facts, and it is a hydraulic circuit that does not rapidly reduce the traveling speed without changing the mode selection, that is, does not feel power shortage, and uses one or two hydraulic pumps. It is an object to provide a hydraulic circuit that can also be applied to a hydraulic circuit.

The present invention employs the following configuration as means for solving the above-described problems. That is,
According to the first aspect of the present invention, in the hydraulic circuit of the construction machine, the traveling operation is performed in the hydraulic circuit of the construction machine in which the set torque of the hydraulic pump is selected from a plurality of work modes and the work machine can be operated with the set torque of the selected mode. When a means for detecting is provided and a traveling operation by the detecting means is detected during work in any one of the work modes, the horsepower control start pressure of the hydraulic pump matches the horsepower control start pressure in the maximum set torque mode. This is characterized in that the set torque is increased.

  According to a second aspect of the present invention, in the hydraulic circuit of the construction machine, the output torque of the hydraulic pump is selected from a plurality of work modes, and the work machine can be operated with the set torque of the selected mode. A means for detecting an operation is provided, and when a traveling operation is detected by the detecting means during work in any one of the work modes, the set torque is increased to an allowable maximum torque.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the hydraulic circuit includes an inverse proportional solenoid valve connected to a torque setting port of a regulator that adjusts a discharge amount of a hydraulic pump having a variable discharge amount. Connect the secondary port, connect the pilot hydraulic pump and oil tank to the primary port of the inverse proportional solenoid valve, connect the controller output terminal to the solenoid of the inverse proportional solenoid valve, and input the controller input terminal And the output of the travel operation detection device and the output of the work mode changeover switch are connected to the controller, and when the controller receives a travel operation detection signal when any of the work modes is selected, the set torque is the predetermined torque. A solenoid current that satisfies the relationship is output.

  When a traveling operation by the detecting means is detected during work in any work mode, the horsepower control start pressure of the hydraulic pump matches the horsepower control start pressure of the maximum set torque mode without changing the mode. Alternatively, since the torque is increased to the maximum allowable torque, the vehicle can smoothly travel when climbing from a flat ground. Therefore, the effect that the work on the undulating land can be performed smoothly is obtained.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a circuit diagram of an embodiment of the present invention, and FIG. 3 shows a characteristic curve in this embodiment. In FIG. 1, a hydraulic pump 10 having a variable discharge amount is driven by an engine 11. The discharge amount of the hydraulic pump 10 is controlled by a regulator 12. The port 12a of the regulator 12 is a control port, and the horsepower is controlled to be constant by applying the discharge pressure of the hydraulic pump to the control port 12a. The port 12b is a control port for increasing / decreasing the set horsepower, and is set so that the horsepower increases when the applied signal oil pressure (Pf) is decreased. A travel switching valve 15 and a switching valve 16 for controlling other actuators are connected to the center oil passage 14 of the hydraulic pump 10. A travel hydraulic motor 15a is connected to the secondary side (output side) of the travel switching valve 15 as an actuator.

  On the other hand, a mode selection switch 21 and a travel detection means 22 are connected to the input side of the controller 20. The selection switch 21 is a changeover switch and can select a plurality of work modes such as H mode (high horsepower mode or heavy excavation mode), S mode (medium horsepower mode or standard mode), and L mode (small horsepower mode or finishing mode). It has become. The traveling detection means 22 includes a check valve 22a for detecting the maximum pressure of the left and right pilot pressures of the traveling operation remote control valve 17, and a pressure switch 22b for checking whether or not the input pressure exceeds a predetermined pressure. . Connected to the output side of the controller 20 is a solenoid 23a of an inverse proportional solenoid valve 23 for controlling the signal oil pressure (Pf) applied to the control port 12b. A pilot hydraulic pump 23b and an oil tank T are connected to the primary port of the inverse proportional solenoid valve 23, and a hydraulic pipe for transmitting signal oil pressure is connected to the secondary port.

  FIG. 2 is a diagram showing the relationship between the solenoid current value I output from the controller 20 to the solenoid 23a and the secondary pressure Pf of the inverse proportional solenoid valve 23, and the relationship between the secondary pressure Pf and the set torque of the hydraulic pump 10. is there. It is in inverse proportion to the secondary pressure Pf within a certain range (Imin to Imax) of the current value I. That is, when the current value I is increased, the secondary pressure Pf decreases in inverse proportion. Further, the secondary pressure Pf and the set torque T of the hydraulic pump 20 are in an inversely proportional relationship. Therefore, the current value I and the set torque T of the hydraulic pump 20 are in a proportional relationship.

  As shown in FIG. 3, the controller 20 detects the horsepower control start pressure, that is, the hydraulic pump pressure regardless of the mode selected by the selection switch 21 when the travel operation is detected by the travel detection means 22. The pump discharge pressure at which the output horsepower becomes constant horsepower is controlled so as to coincide with the horsepower control start pressure (pump discharge pressure P1 in FIG. 3) in the H mode. As a result, the output torque of the hydraulic pump 20 in each mode (here, the S mode and the L mode) is increased from the state indicated by the one-dot chain line in FIG. 3 to the state indicated by the solid line even without mode switching.

  Since this embodiment is configured as described above, it functions as follows. In other words, when the driving operation is not detected, the same torque output as that of the conventional circuit 2 is obtained, and when the driving operation is detected, the horsepower corresponding to each mode is increased, and the mode is not changed. The running speed in climbing is not reduced suddenly. Therefore, even when climbing, smooth climbing can be performed without feeling power shortage.

  FIG. 4 shows an example in which the output torque during traveling when the S mode and L mode are selected is increased to the output torque when the H mode is selected, as compared to the above embodiment. In this embodiment, as shown in FIG. 4, the horsepower control start pressure during running when the S mode is selected is P4 (P1 <P4), and the horsepower is increased as shown by the solid line in the figure. In addition, when the L mode is selected, the horsepower control start pressure during travel is P5 (P1 <P4 <P5), and a significant increase in horsepower is performed. Therefore, it is easier to travel uphill than in the above embodiment.

  Although the embodiment of the present invention has been described in detail with reference to the drawings, the technical scope of the present invention is not limited to this. For example, the horsepower control start pressure is set to an allowable discharge pressure different from that of the above embodiment. You may raise and increase the horsepower in the run at the time of climbing.

The circuit structure of embodiment which implemented this invention is shown. The relationship between the solenoid current of a reverse proportional solenoid valve and pump setting torque is shown. The characteristic curve of the hydraulic pump of embodiment is shown. The hydraulic pump characteristic curve of other embodiment is shown. The circuit structure of a conventional apparatus is shown. The circuit structure of another conventional apparatus is shown.

Explanation of symbols

10 Hydraulic pump 12 Discharge rate regulator
15 Travel switching valve 16 Other (working) switching valve
17 Traveling remote control valve 20 Controller 21 Mode changeover switch 22 Traveling detection means 23 Inverse proportional solenoid valve

Claims (3)

In the hydraulic circuit of the construction machine in which the set torque of the hydraulic pump is selected from a plurality of work modes and the work machine can be operated with the set torque of the selected mode, a means for detecting a traveling operation is provided, When the traveling operation by the detecting means is detected during the work in the work mode, the set torque is increased so that the horsepower control start pressure of the hydraulic pump matches the horsepower control start pressure of the maximum set torque mode. A hydraulic pump output control circuit for construction machinery. In the hydraulic circuit of the construction machine in which the output torque of the hydraulic pump is selected from a plurality of work modes and the work machine can be operated with the set torque of the selected mode, a means for detecting a traveling operation is provided, A hydraulic pump output control circuit for a construction machine, wherein a set torque is increased to an allowable maximum torque when a traveling operation is detected by the detecting means during work in the work mode. The hydraulic circuit connects a secondary port of an inverse proportional solenoid valve to a torque setting port of a regulator that adjusts the discharge amount of a hydraulic pump having a variable discharge amount, and a pilot hydraulic pump connected to a primary side port of the inverse proportional solenoid valve And an oil tank, an output terminal of the controller is connected to the solenoid of the inverse proportional solenoid valve, an output of the traveling operation detection device and an output of the work mode changeover switch are connected to the input terminal of the controller. 3. The solenoid current according to claim 1, wherein a set torque outputs a solenoid current satisfying the predetermined relationship when a detection signal of a traveling operation is received when the work mode is selected. The hydraulic pump output control circuit of the construction machine according to claim 1.

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