JP2001041204A - Hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of cavitation and deterioration of sealing members which caused by temperature variation of operation oil for actuating a hydraulic circuit. SOLUTION: A hydraulic circuit has a hydraulic pump for supplying operation oil to various actuators and an oil cooler 11 for cooling the operation oil. An oil temperature sensor 14 is arranged on an upstream side of the hydraulic pump 2 of the hydraulic circuit for sensing the temperature of the operation oil. In addition, a pressure sensor 15 is arranged on the upstream side of the oil cooler 11 for sensing the pressure of the operation oil. The respective sensed values are input to a controller 10. The controller 10 adjusts a discharge amount of the hydraulic pump 2 according to the sensed signals, and prevents occurrence of cavitation of the hydraulic motor 2 under a low temperature and deterioration of sealing under a high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit having a hydraulic pump for supplying hydraulic oil to an actuator and an oil cooler for cooling the hydraulic oil, and more particularly to a hydraulic oil for operating the hydraulic circuit. The present invention relates to a hydraulic circuit configured to prevent cavitation or the like due to a temperature change of a hydraulic circuit.

[0002]

2. Description of the Related Art As a construction machine, for example, a construction machine which drives a crawler by a hydraulic motor and runs by the rotational driving force of the crawler is known.

[0003] Hydraulic oil circulating in a hydraulic circuit of this type of construction machine shows good properties in a certain temperature range.
It does not correspond to low or high temperatures outside the range of use. Viscous resistance increases at low temperatures and volume expansion occurs at high temperatures. For this reason, in high-temperature environments such as cold regions and highlands, if high-speed operation is started immediately after the start of the engine, the hydraulic pump will not be able to sufficiently suck in hydraulic oil, and cavitation will occur, causing damage due to cavitation. May occur. In addition, if heavy work with a high load is continuously performed when the temperature is high, such as in summer, the oil temperature of the hydraulic oil increases, the pilot pressure decreases due to leaks, and the sealing material such as packing deteriorates. Sometimes. Although the hydraulic circuit of this type of construction machine is equipped with an oil cooler for cooling the hydraulic oil, the flow rate of the hydraulic oil increases according to the load, and the amount returned to the hydraulic oil tank becomes excessive. When the circuit pressure (return oil) increases, the hydraulic oil that should originally flow into the oil cooler bypasses the hydraulic oil tank through a check valve for protecting the oil cooler. Therefore, when heavy work is continued in a high-temperature environment, sufficient cooling becomes impossible, and a reduction in pilot pressure due to leakage or the like and deterioration of a sealing material such as packing are inevitable.

[0004] Therefore, there arises technical problems to be solved in order to prevent cavitation and deterioration of the sealing material caused by a change in the temperature of the hydraulic oil that operates the hydraulic circuit. The purpose is to solve the problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above object, and is intended to detect the oil temperature of hydraulic oil upstream of a hydraulic pump for supplying hydraulic oil to various actuators. A hydraulic circuit provided with oil temperature detecting means, and a controller for adjusting the discharge flow rate of the hydraulic pump based on the detection value of the oil temperature detecting means, and pressure detection for detecting the pressure of hydraulic oil upstream of the oil cooler Providing means,
It is an object of the present invention to provide a hydraulic circuit provided with a controller that operates an alarm unit based on a detection value of the pressure detection unit.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to a construction machine such as a crawler type traveling crane will be described below in detail with reference to FIGS. FIG. 1 shows a hydraulic circuit according to the present embodiment, and FIG. 2 shows a control device for controlling the hydraulic circuit. In FIG. 1, reference numeral 1 denotes an engine, 2 denotes a traveling hydraulic motor (not shown) for driving a crawler (not shown), and a variable displacement hydraulic pump (hereinafter, referred to as a hydraulic pump) for operating various actuators of a construction machine. Hydraulic pump). The hydraulic pump 2 is connected to the engine 1 and is driven by transmitting the driving force of the engine 1.
A suction strainer 4 is provided at the suction port 3 of the hydraulic pump 2,
A suction line 6 including a check valve 5 for pressurization is connected, and hydraulic oil is sucked from a hydraulic oil tank 7 and supplied to the hydraulic main circuit 8 to be connected to the hydraulic main circuit 8. Driving hydraulic motors and other actuators.

A regulator 9 is attached to the hydraulic pump 2, and controls the regulator 9 in accordance with an external input signal output from a controller 10 to control the discharge amount of the hydraulic pump 2. Reference numeral 11 denotes an oil cooler for cooling the hydraulic oil circulating between the hydraulic main circuit 8 and the hydraulic oil tank 7, and 12 denotes a check for pressure resistance protection provided in a bypass passage 13 bypassing the oil cooler 11. Show the valve. The valve opening pressure of the check valve 12 is set so as to open when the differential pressure between both ends (IN-OUT) of the oil cooler 11 becomes a predetermined value or more, and the hydraulic oil is bypassed to the hydraulic oil tank 7. The oil cooler 1
1 prevents overload and prevents a series of heat exchange pipes from bursting. 1 and 2, reference numeral 14 denotes an oil temperature sensor for detecting the temperature of hydraulic oil, reference numeral 15 denotes a pressure sensor for detecting pressure of hydraulic oil, and reference numeral 16 denotes an operation position of an operation lever of the various actuators. 3 shows an operation lever detector. As shown in FIG. 1, the oil temperature sensor 14 is arranged on the upstream side of the hydraulic pump 2, and the pressure sensor 15 is arranged on the upstream side of the oil cooler 11, and detects the oil temperature and pressure of the hydraulic oil, respectively. The operation lever detector 16 detects whether or not each actuator of a construction machine such as a crane, for example, an operation lever (not shown) for driving a hoisting / lowering drum of a suspended load is operated. It is configured. In the present embodiment, the operation lever detector 16 is constituted by, for example, a pressure switch provided in a hydraulic drive circuit (not shown) for driving a hoisting / lowering drum of a suspended load.

As shown in FIG. 2, the detection values of the oil temperature sensor 14, the pressure sensor 15, and the operation lever detector 16 are as follows.
Each is converted into an electric signal and output to the controller 10, and when the operation lever detector 16 detects a preset pressure, it outputs a corresponding electric signal to the controller 10.

[0009] The controller 10 is constituted of a microcomputer, the oil temperature sensor 14, and outputs an operation signal q _L to the regulator 9 based on the detection signal of the pressure sensor 15 and the operation lever detector 16, the alarm device 1
7, an operation signal I is output.

That is, the controller 10 reads the detection signal θ of the oil temperature sensor 14 and generates the detection signal θ.
When θ <θ _L (θ _L is a predetermined value), a “low temperature alarm signal” I is output to the alarm device 17 and a pump minimum discharge signal q _L of the hydraulic pump 2 is output to the regulator 9. Of course, the predetermined value θ _L is set to a lower limit temperature at which cavitation does not occur when the hydraulic pump 2 sucks.

For this reason, when the temperature of the hydraulic oil is θ <θ _L , the hydraulic pump 2 sucks the hydraulic oil of the minimum flow rate from the hydraulic oil tank 7 and supplies it to the hydraulic main circuit 8. Become. Accordingly, high-speed operation immediately after starting at low temperature is automatically prevented, and the hydraulic pump 2 due to viscous resistance at low temperature is prevented.
Cavitation is prevented.

The oil temperature of the hydraulic oil rises, and the oil temperature becomes θ _L ≦ θ <
When it becomes θ _H (θ _H is a predetermined value), the output of the “low temperature alarm signal” I and the pump minimum discharge signal q _L by the controller 10 is released, and the normal operation is performed. At this time, in a hydraulic motor drive system in which the discharge amount of the hydraulic pump 2 is freely controlled by an external potentiometer, this system is effective and the discharge amount of the hydraulic pump 2 is controlled.

After the start, if the temperature of the hydraulic oil exceeds θ <θ _L , heavy work becomes possible.

Heavy work is continuously performed, the oil temperature rises,
When θ> θ _H (θ _L > θ _H ), the controller 10 reads the detection signal p of the pressure sensor 14.

At this time, if the pressure of the hydraulic oil is p <p _H (p _H
Is a predetermined value), the controller 10 outputs a “high temperature alarm signal” to the alarm device 17 to temporarily suspend the work or perform an operation for cooling the hydraulic oil (neutralize the operation lever to lower the pump flow rate). To do). Therefore, by setting the predetermined pressure p _H to the valve opening pressure and the pressure of the check valve 12 for breakdown voltage protection, and overload of the oil cooler 11, according to the alarm device 17 and a "high-temperature alarm signal" I is notified to the operator Will be. Therefore, if the operator interrupts the operation at this time, deterioration of the seal under a high load can be prevented, and overheating of the engine due to overload can be prevented.

Further, as described above, the operating lever detector 1
6, the controller 10 is provided with an operation lever.
-Operation to operate various actuators by the detector 16
When the lever is moved to the neutral position, the hydraulic
Pump 2 minimum discharge signal q _LOutput to turn off the hydraulic oil.
It flows into the ircooler 11. Of course, in this case, before
Even if the operating lever is other than neutral,
The work may be hindered by lowering the pump flow rate in Step 2.
Hydraulic oil may be cooled so as not to do so.

As described above, the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

[0018]

As described in detail in the above embodiment, the present invention detects, for example, the temperature of hydraulic oil upstream of a hydraulic pump and the pressure of hydraulic oil upstream of an oil cooler, so that the oil temperature is less than a predetermined value. In the case of controlling the discharge flow rate of the hydraulic pump to a minimum,
When the oil temperature exceeds the predetermined value and the oil pressure exceeds the predetermined value, the alarm means is activated, so that cavitation due to the low oil temperature of the hydraulic oil is prevented, and the oil temperature of the hydraulic oil becomes high. Thus, the present invention has an extremely significant effect, for example, it is possible to prevent the deterioration of the seal at the time of a high load caused by the above.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an embodiment of the present invention and illustrating a configuration of a control circuit. FIG.

[Explanation of symbols]

 2 Hydraulic pump 10 Controller 11 Oil cooler 14 Oil temperature sensor (oil temperature detecting means) 15 Pressure sensor (pressure detecting means)

Claims (2)

[Claims] An oil temperature detecting means is provided upstream of a hydraulic pump for supplying hydraulic oil to various actuators, for detecting an oil temperature of the hydraulic oil, and the hydraulic pump is provided based on a detected value of the oil temperature detecting means. A hydraulic circuit, comprising: a controller for adjusting a discharge flow rate of the hydraulic fluid. 2. The hydraulic circuit according to claim 1, further comprising: a pressure detecting means provided upstream of the oil cooler for detecting the pressure of the hydraulic oil; and a controller activating alarm means based on a detected value of the pressure detecting means.