JP2884899B2 - Running speed control method 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 method for controlling a traveling speed of a construction machine such as a crawler type hydraulic excavator.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram of a conventional traveling speed control circuit for a hydraulic shovel. In the figure, 1L and 1R denote a pair of left and right running levers (including a pedal), 2F and 3F.
Are left and right forward pilot valves, 2R and 3R are left and right reverse pilot valves, 4L and 4R are left and right traveling motors capable of 1-2 speed switching, 5 is an electromagnetic switching valve, and 6 is a 1-2 speed switching valve. Switches, 7L and 7R are pilot switching valves for controlling the traveling motors 4L and 4R, 8, 9 and 10 are pilot switching valves for controlling various working hydraulic actuators (not shown), 11 is a traveling straight valve, and 12 and 13. Are the first and second pumps, respectively, and 14 and 15 are the first pump 12 and the second pump, respectively.
Each of the regulators of the pump 13, 16 is a pilot pump, 17 is an engine, 18 is a governor of the engine 17, 19 is a controller, 20 is a work mode changeover switch, 21 is a control motor for adjusting and driving the governor 18, and symbols I, B -B, ha, ni are the pilot valve 2F,
The connection of the pilot pipeline which communicates 2R, 3F, 3R and pilot switching valves 7L, 7R is shown. FIG. 5 is a chart showing pump discharge amounts discharged from the first pump 12 and the second pump 13 in accordance with the operation of the traveling levers 4L and 4R.

In a conventional traveling speed control circuit, as shown in FIGS. 4 and 5, an engine 17 and first and second variable displacement pumps 12 and 13 driven by the engine 17 (hereinafter referred to as a first pump 12). And the second pump 13 are collectively referred to as a variable pump), and the flow rate of hydraulic oil from the variable pump is changed according to the displacement of the travel levers 1L and 1R (hereinafter simply referred to as the travel lever).
To supply it. That is, the pilot valves (2F, 2R, 3
The pilot secondary pressure corresponding to the operation displacement amount of the traveling lever is derived from one of the pilot valves F and 3R), and the pilot switching valves 7L and 7R are switched.
Since the traveling motors 4L and 4R rotate, the excavator moves forward or backward. By operating the switch 6 connected to the solenoid 22 of the electromagnetic switching valve 5 before starting the traveling, the rotation speed of the traveling motors 4L and 4R can be selected to be the first speed or the second speed. The traveling motor 4
L and 4R can be switched to 1-2 speed,
By switching the work mode changeover switch 20, the engine rotation is selected to a work mode of H (high speed rotation for heavy load), S (medium speed rotation for normal load), and FC (low speed rotation for fine operation work). Switching can be performed. In addition, when the operation is performed at D, the engine speed is reduced to a low speed, and a change in the traveling speed in the simultaneous operation of the work attachment and traveling of the excavator can be eliminated.

[0004]

When a crawler-type hydraulic excavator travels in a narrow place or on a site with poor scaffolding, it travels at a low speed to ensure safety. When traveling at this low speed, in the prior art, the operation angle of the traveling lever is kept in a fine operation range, or the engine speed is reduced to low speed by traveling speed setting means such as a work mode switch. Such operation methods and procedures are difficult and troublesome to operate. Further, when the engine speed is reduced to a low speed, the engine speed must be increased again when the operating speed of the work attachment is to be increased next time, which is troublesome and inconvenient. SUMMARY OF THE INVENTION An object of the present invention is to provide a traveling speed control method that does not hold a traveling lever in a fine operation range when a hydraulic excavator performs a low-speed traveling, and can eliminate a troublesome operation of switching an engine speed to a low speed. And

[0005]

SUMMARY OF THE INVENTION The present invention comprises an engine and a variable pump driven by the engine, and supplies a flow rate of hydraulic oil from the variable pump to a travel motor in accordance with a displacement of a travel lever. In the traveling speed control method for a construction machine, the pump discharge amount of the variable pump increases as the pilot pressure derived in response to the operation of the traveling lever increases from a predetermined low pressure to a predetermined high pressure, and at each traveling speed, By storing a pump characteristic that reaches the maximum pump discharge amount in the storage unit of the controller and sending a command signal from the traveling speed setting operation unit to the controller, the pump characteristic corresponding to any traveling speed in the storage unit is stored. This is to drive the traveling motor selectively. In the above configuration, when traveling the construction machine, if a predetermined traveling speed in the storage unit is selected by operating the traveling speed setting operation unit, the variable pump for driving the traveling motor is operated with the corresponding pump characteristics. Therefore, it is necessary to prevent the shock such as rapid start from occurring even if the traveling lever is inadvertently operated at a large angle without exceeding the set maximum pump discharge rate. Can be.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a driving speed control circuit diagram according to the present invention. In the figure, the same reference numerals are given to components using the same components as the conventional technology. 14 'and 15' are regulators of a first pump 12 'and a second pump 13' (hereinafter referred to as variable pumps), 19 'is a controller, 23 is a memory (ROM) of the controller 19', 2
4 is an electromagnetic proportional pressure reducing valve as an electro-oil converter, 25 and 26 are potentiometers for detecting displacement amounts of the traveling levers 1L and 1R, and 27 is a traveling which can adjust and set a required traveling speed steplessly or stepwise. It is a speed setting operation unit. Note that, instead of the potentiometers 25 and 26, a detecting means such as a pressure sensor (not shown) that can detect the operation displacement amount of the traveling lever may be provided. FIG. 2 and FIG.
3 is a chart showing a relationship between a pilot secondary pressure derived from a pilot valve and a pump discharge amount, respectively.

Next, a traveling speed control method according to the present invention will be described with reference to FIGS.
Referring to FIG. In the present invention, the traveling levers 1L, 1
Potentiometers 25 and 26 for detecting the amount of operation displacement of R (hereinafter referred to as a traveling lever) are provided, and a displacement detection signal from the potentiometers 25 and 26 is sent to a controller 19 '.
The maximum pump discharge amount at each set speed is set by operating the traveling speed setting operation section 27. That is, the pump speed characteristic curves a, b, and
One of c and d is set, and the values of the pump characteristic curves a, b, c, and d at the maximum value Pmax of the pilot secondary pressure Pi by operating the traveling lever are set as the maximum pump discharge amount. The maximum pump discharge amount and the pump discharge amount increase as the pilot secondary pressure derived in response to the operation of the travel lever increases from a predetermined low pressure to a predetermined high pressure, and each reaches the set maximum pump discharge amount. Such pump characteristics (the pump characteristics shown in FIG. 2 and indicated by reference numeral E in FIG. 1) are stored in the memory (RO) of the controller 19 ′.
M) 23. When the hydraulic excavator travels in this state, first, the work mode changeover switch 20, the traveling motors (4L and 4R) 1-
The second speed switch 6 and the traveling speed setting operation unit 27 are operated. By inputting a signal from the work mode changeover switch 20 to the controller 19 ', the target rotation speed of the engine 17 is determined. Next, when the operation of the travel lever is started, displacement detection signals from the potentiometers 25 and 26 are input to the controller 19 '. In the controller 19 ′, the displacement detection signal, the set speed signal from the traveling speed setting operation unit 27, and the pump characteristics corresponding to the current set speed stored in the memory 23 (the pump characteristic curves in FIGS. 1 and 2). The determination is made based on the storage of pump characteristics corresponding to any of the set speeds a, b, c, and d, and a pump displacement amount command signal is output to the electromagnetic proportional pressure reducing valve 24. The pilot pressure corresponding to the pump displacement amount command signal is supplied from the electromagnetic proportional pressure reducing valve 24 to the regulator 14 ′.
And 15 ', so that the variable pump discharges the pump discharge at the set pump characteristic,
The pump displacement is adjusted. Thus, the traveling lever can be operated at substantially the same angle regardless of the required set speed (regardless of high speed, medium speed, low speed, or low speed), and the vehicle can travel at the required set speed. This will be described with reference to FIG. Pump characteristic curves a, b,
The purpose of c and d is to indicate the maximum pump discharge amount, and the path until reaching the maximum pump discharge amount for the pump characteristic curves b, c and d is exactly as shown in FIG. That is, in the traveling speed control range, the pump characteristic curve b increases along with the pump secondary pressure Pi along the pump characteristic curve a (the inclined straight line drawn upward in FIG. 3), and the pump discharge amount Q increases. When the secondary pressure is P ₁ pump discharge amount becomes maximum becomes Q _1, the pump discharge amount even pilot secondary pressure rises further to the Q
_The broken line that keeps ₁ (ie, the pump characteristic curve b) is a broken line that rises linearly rightward and then extends horizontally. When Accordingly pilot secondary pressure reaches P _1, more to be engineered travel lever (be thereby increasing the pilot secondary pressure) pump discharge quantity does not increase, the running speed of the machine is constant Will be kept. The pump characteristic curve c pump discharge quantity Q increases with increasing pilot secondary pressure Pi along the pump characteristic curve a, the pump discharge quantity when the pilot secondary pressure is P ₂ is Q ₂
Next, the pump discharge amount even pilot secondary pressure rises further to become polygonal line such that while maintaining a Q _2.
When Accordingly pilot secondary pressure reaches P _2, the pump discharge quantity does not increase even by operating the driving lever more than that, the running speed of the machine will be kept constant. Furthermore the pump characteristic curve d the pump discharge quantity Q increases with increasing pilot secondary pressure Pi along the pump characteristic curve a, the pilot secondary pressure is P ₃ pump discharge amount is Q _3, and the
More pump discharge amount even pilot secondary pressure is increased to become polygonal line such that while maintaining a Q _3. When Accordingly pilot secondary pressure reaches P _3, the pump discharge quantity does not increase even by operating the driving lever more than that, the running speed of the machine will be kept constant. In the case of the pump characteristic curve a, the pilot secondary pressure rises to Pmax in accordance with the operation of the operation lever within the traveling speed control range, as shown by the solid line in FIG. Also rises to Qmax.

The pump discharge amount determined by the pilot secondary pressure derived in accordance with the operation of the travel lever and the pump discharge amount determined by the speed setting of the travel speed setting operation section 27 are compared with each other, and the smaller pump discharge amount is compared. The discharge amount was suppressed. Accordingly, when the required traveling speed υ1 (shown in FIG. 3) is set and operated in the traveling speed setting operation unit 27, the traveling lever is derived according to the displacement amount of the traveling lever when the traveling lever is tilted from the neutral position. When the pilot secondary pressure from the pilot valve reaches the pressure P1, the pump discharge rate also increases to Q1. However, even if the travel lever is tilted further than the above time, the pump tilt amount is not adjusted. That is, the traveling lever is further tilted further to increase the pilot secondary pressure derived from the pilot valve to P2
, P3──Pmax and the pump discharge amount remains at Q1 even when the pressure is increased to a high pressure. Therefore, the traveling speed setting operation unit 2
For example, when the speed 7 is set to a considerably low speed, even if the traveling lever is inadvertently tilted to a large angle, the hydraulic excavator does not start quickly, which is safe.

[0009]

According to the structure of the present invention, when the construction machine travels, by operating the traveling speed setting operation section and selecting a predetermined traveling speed in the storage section of the controller, the variable pump for driving the traveling motor is operated. Will operate with the corresponding pump characteristics, so that it will not exceed the set maximum pump discharge rate, so that even if the travel lever is inadvertently operated at a large angle, a shock such as a rapid start will occur. This can be reliably prevented from occurring.

[Brief description of the drawings]

FIG. 1 is a traveling speed control circuit diagram of a hydraulic shovel according to the present invention.

FIG. 2 is a table showing a relationship between a pilot secondary pressure from a travel lever pilot valve and a pump discharge amount.

FIG. 3 is a table showing a relationship between a pilot secondary pressure from a travel lever pilot valve and a pump discharge amount.

FIG. 4 is a circuit diagram of a traveling speed control circuit of a conventional hydraulic excavator.

FIG. 5 is a table showing a relationship between a pilot secondary pressure from a travel lever pilot valve and a pump discharge amount.

[Explanation of symbols]

 1L, 1R Travel lever 4L, 4R Travel motor 6 (for 1-2 speed switching) Switch 12, 12 'First pump 13, 13' Second pump 14, 14 ', 15, 15' Regulator 17 Engine 19, 19 ' Controller 20 Work mode selector switch 24 Proportional pressure reducing valve 25, 26 Potentiometer 27 Travel speed setting operation unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F15B 11/00-11/04 E02F 9/22

Claims (1)

(57) [Claims] An engine and an engine driven by the engine
Equipped with a variable pump, and the pressure oil flow from the variable pump
Is supplied to the travel motor according to the travel lever displacement.
In the traveling speed control method for a construction machine,
The pilot pressure derived according to the operation of the lever
As the pressure rises from a low pressure to a predetermined high pressure,
Pump discharge increases and the maximum
Controller for pump characteristics to reach pump discharge rate
Command signal from the traveling speed setting operation unit.
By sending the number to the controller,
Select the pump characteristic corresponding to one of the traveling speeds
A traveling speed control method for a construction machine, wherein a traveling motor is driven .