GB2278404A

GB2278404A - Method of preheating hydraulic fluid

Info

Publication number: GB2278404A
Application number: GB9413473A
Authority: GB
Inventors: Bong Dong Hoang; Jang Ug Jo; Sang-Tae Jeong; Chan-Hee Lee; Myeong-Hun Song; Jin-Han Lee
Original assignee: Samsung Heavy Industries Co Ltd
Current assignee: Samsung Heavy Industries Co Ltd
Priority date: 1990-11-13
Filing date: 1991-10-24
Publication date: 1994-11-30
Anticipated expiration: 2011-10-24
Also published as: GB2278465B; GB2278465A; GB9413473D0; GB9413474D0; GB2278404B

Abstract

In a system to preheat the hydraulic fluid of an actuator system eg of a heavy construction vehicle, valves in the hydraulic system are operated so that the temperature of the hydraulic fluid output by the main pumps is caused to rise by virtue of pressure loss occurring due to a resistance generated between the hydraulic fluid and relief valves as the hydraulic fluid passes through the relief valves. The preheating of the hydraulic fluid is only effected when the temperature of the hydraulic fluid T is below a set value and when no operation of the hydraulic system is being requested theta i = 0. Also disclosed is a system for automatically starting the engine of the construction vehicle (figure 6) and a system for controlling the temperature of the hydraulic fluid and engine coolant by regulating the engine speed in response to the measured temperatures of the hydraulic fluid and engine coolant (figure 3). <IMAGE>

Description

SYSTEM FOR AUTOMATICALLY CONTROLLING AN OPERATION OF A HEAVY CONSTRUCTION BACKGROUND OF THE INVENTION Field of The Invention The present inventing relates to a system for automatically controlling an operation of a heavy construction, such as an excavator and the like, and more particularly to a system for controlling an operation of the heavy construction in which a driving engine of the heavy construction is always optimally started, the hydraulic fluid for the actuators is automatically controlled in its temperature and also preheated in order to reach to a predetermined temperature, thereby improving the operational effect of the heavy construction.

Description of The Prior Art Conventionally, known heavy construction such as an excavator is provided with a plurality of hydraulic pumps which are driven by virtue of driving power from a diesel engine in order to output hydraulic fluid to a plurality of actuators. Thus, a desired operation by the heavy construction can be efficiently performed.

However, known heavy construction has the following disadvantages resulting in fatigue of the operator, said fatigue causing the operational effect of the heavy construction to be deteriorated, and causing the driving power of the engine to be lost and also the actuators to be broken and a safety accident to occur during the operations thereby.

First, driving engines of the known heavy constructions have to be generally so preheated before a normal starting thereof as engines of another types of equipments and vehicles have to be preheated in order to make the operational temperature thereof reach to a desired temperature.

Especially, the heavy construction has to be preheated before the normal starting in order to allow the hydraulic fluid, which is outputted from the hydraulic pumps to the actuators, to rise to a desired temperature.

However, the known heavy construction has no apparatus for sensing the temperature of the hydraulic fluid and making the temperature thereof reach to the desired temperature. In result, it is required that the operator judges by his experience the temperature of the hydraulic fluid upon taking account of the peripheral temperature of the heavy construction in order to preheat the hydraulic fluid of the heavy construction for a time, resulting in causing the temperature of the fluid to reach to the desired temperature.

Thus, the known heavy construction has disadvantage in that the preheating operation for the hydraulic fluid thereof can not be optimally and minutely performed, so that the preheating operation is occasionally carried out for a considerable time, resulting in driving power loss. On the contrary, if the preheating operation is not carried out for an enough time, the temperature of the hydraulic fluid can not reach to the desired temperature, resulting in making the engine of the heavy construction be overloaded due to the cold temperature of the hydraulic fluid.

Second, the known heavy construction such as an excavator is conventionally provided with a plurality of hydraulic pumps which are straightly connected to an output port of the engine thereof and also a plurality of actuators which are driven by virtue of the hydraulic fluid outputted from the hydraulic pumps thereto. In addition, the known heavy construction is provided with several operational modes, each previously programmed in a control circuit thereof, in order to allow the operator to select one of the programmed operational modes depending upon a given operational condition. Thus, the operational speed of the heavy construction efficiently varies depending on the operational condition.

For example, a known heavy construction such as disclosed in Korean Patent Application No. 90-15862, applied by the applicant of this invention, is provided with three operational modes each previously programmed in the control circuit thereof, a H operational mode in which a maximum quantity of fuel is supplied to the engine in order to drive the engine at a maximum rotative speed so that the operational speed of the heavy construction reaches to a maximum operational speed, a S operational mode in which the engine is driven at a normal rotative speed of 10-20% of the above maximum rotative speed in order to accomplish a normal speed operation, and a L operational mode in which the engine is driven at a lower rotative speed of 10-20% of the above normal speed in order to accomplish a silent operation.

During operating the above known heavy construction, the operator selects adjustable one of the programmed operational modes, the H, S and L operational modes, by means of an operational mode select switch provided in the control cab, upon taking account of an operational condition.

However, if the type of heavy construction has been operated for a long time upon selecting the H operational mode, the respective temperature of the engine coolant and the hydraulic fluid each considerably rises in order to exceed a predetermined maximum allowable overheat temperature. Hence, in case of requiring a long time operation under the H operational mode, the operator has to often checks the respective temperature of the engine coolant and the hydraulic fluid in order to reduce the engine speed, and furthermore temporarily stop the operation of the heavy construction in order to cool or change the overheated engine coolant and the hydraulic fluid with new coolant and new hydraulic fluid.

Therefore, the known heavy construction has disadvantage in that a continuous operation can not be accomplished due to such an overheat, thereby deteriorating the operational effect thereof and burdening the operator with changing the engine coolant and the hydraulic-fluid.

Third, the known heavy construction conventionally adopts a starting manner for the diesel engine in which a fuel supply control valve (a throttle valve) is first positioned at the starting position, and an engine starting switch (an engine starting key) is then shifted from stop position to starting position in order to start the engine, and the engine starting switch last automatically returns to the stop position after accomplishing the starting state of the engine. However, the known heavy construction has disadvantage in that the starting for the engine is not often accomplished such as due to an occurrence of a breakdown in a start motor or a problem of a battery, thereby resulting in requiring a few times retry for the starting. In addition, the diesel engine of the known heavy construction requires the cold start in case of starting under a cold temperature.In the cold start, the engine is first preheated for a time before the normal starting in order to make the temperature of the engine reach to a desired temperature, or first supplied with an additive such as an ether before the starting. Therefore, the known heavy construction has a disadvantage in that it can not provide a reliability and also requires a considerable time in starting of the engine thereof.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a system for automatically controlling an operation of a heavy construction in which the above disadvantage can be overcome and temperature of hydraulic fluid of the hydraulic pumps is automatically and efficiently preheated in order to reach to a desired temperature in a relatively short time, thereby removing a waste of energy and time due to an excessive preheating.

It is another object of this invention to provide a system for automatically controlling an operation of a heavy construction to which sensors are provided for sensing respective temperature of the hydraulic fluid and engine coolant in case of occurrence of overheating temperature exceeding respective predetermined overheat reference temperature due to lasting a high speed operational mode for a long time, alarming the operator to the occurrence of the overheat and automatically changing the operational mode into a relatively low speed operational mode in order to cool the engine coolant and the hydraulic fluid, thereby efficiently preventing the engine coolant and the hydraulic fluid from being overheated and proving a continuous operation.

It is still another object of this invention to provide a system for automatically controlling an operation of a heavy construction in which the engine is always optimally started irrespective of peripheral condition, thereby improving the starting reliability of the heavy construction.

In one aspect, the above objects of this invention can be accomplished by providing a control apparatus for automatically controlling the operation of a heavy construction comprising an engine; a plurality of actuators; an electronic controller for controlling the operation of said actuators; main hydraulic pumps for supplying hydraulic fluid for said actuators; a sub-hydraulic pump for supplying pilot hydraulic fluid; positional sensors provided at respective actuators in order to sense positional displacement values of said actuators; a directional control valve block connected to said main hydraulic pumps and said electronic controller for controlling operational direction of said actuators and also quantity of said hydraulic fluid flow; wobbling angle control valves disposed between the controller and the main pumps for controlling wobbling angles of the main hydraulic pumps in order to control said quantity of hydraulic fluid flow outputted therefrom; control levers/pedals for outputting respective electric signals corresponding to handling values for actuators to the controller; an amplifier disposed between the controller and said wobbling angle control valves for amplifying an electric signal outputted from the controller to the wobbling angle control valves; relief valves disposed at a hydraulic passage between the directional control valve block and the main hydraulic pumps for preventing said hydraulic passage from being overloaded; directional control solenoid valves each connected to the directional control valve block; a solenoid valve disposed among the controller, the directional control solenoid valves and the relief valves for selectively controlling each preset pressure of the directional control solenoid valves and the relief valves; the control apparatus further comprising: means for sensing respective temperature of a coolant of the engine and the hydraulic fluid, said means disposed at the engine and the hydraulic pumps, respectively; means for alarming the operator to occurrence of overheat in accordance with a control signal from the controller in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, said means electrically connected to the controller; means for accelerating and reducing a rotative speed of the engine, said means relatively reducing said rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, and then accelerating the rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is lower than each predetermined safety operational temperature, said means electrically connected to the controller; wherein each operational temperature of the coolant of the engine and the hydraulic fluid is automatically controlled.

In another aspect, the above objects of this invention can be accomplished by providing a control method for controlling a control apparatus for automatically controlling the operation of a heavy construction, said control apparatus comprising an engine; a plurality of actuators; an electronic controller for controlling the operation of said actuators; main hydraulic pumps for supplying hydraulic fluid for said actuators; a sub-hydraulic pump for supplying pilot hydraulic fluid; positional sensors provided at respective actuators in order to sense positional displacement values of said actuators; a directional control valve block connected to said main hydraulic pumps and said electronic controller for controlling operational direction of said actuators and also quantity of said hydraulic fluid flow; wobbling angle control valves disposed between the controller and the main pumps for controlling wobbling angles of the main hydraulic pumps in order to control said quantity of hydraulic fluid flow outputted therefrom; control levers/pedals for outputting respective electric signals corresponding to handling values for actuators to the controller; an amplifier disposed between the controller and said wobbling angle control valves for amplifying an electric signal outputted from the controller to the wobbling angle control valves; relief valves disposed at a hydraulic passage between the directional control valve block and the main hydraulic pumps for preventing said hydraulic passage from being overloaded; directional control solenoid valves each connected to the directional control valve block; a solenoid valve disposed among the controller, the directional control solenoid valves and the relief valves for selectively controlling each preset pressure of the directional control solenoid valves and the relief valves; means for sensing respective temperature of a coolant of the engine and the hydraulic fluid, said means disposed at the engine and the hydraulic pumps, respectively; means for alarming the operator to occurrence of overheat in accordance with a control signal from the controller in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, said means electrically connected to the controller; means for accelerating and reducing a rotative speed of the engine, said means relatively reducing said rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, and then accelerating the rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is lower than each predetermined safety operational temperature, said means electrically connected to the controller, the control method comprising the steps of: upon receiving each temperature of the coolant and the hydraulic fluid from the means for sensing the temperature and also receiving an initial operational mode of the heavy construction, comparing each said temperature with each predetermined reference overheat temperature in order to output an alarm signal to said means for alarming; upon receiving each present temperature of the coolant and the hydraulic fluid from the means for sensing the temperature and also receiving a present operational mode of the heavy construction, comparing each said present temperature with each predetermined safety operational temperature and comparing said present operational mode with said initial operational mode; wherein each operational temperature of the coolant of the engine and the hydraulic fluid is automatically controlled.

In another aspect, the above objects of this invention can be accomplished by providing a control method for controlling a control apparatus for automatically controlling the operation of a heavy construction comprising the steps of: upon receiving a temperature of the hydraulic fluid from said means for sensing temperature and also receiving manipulating values for the actuators from the control levers/pedals, comparing said temperature of the hydraulic fluid with a predetermined allowable minimum temperature and determining whether said manipulating values are zero; in case that the temperature of the hydraulic fluid is lower than said predetermined allowable minimum temperature and also the manipulating values are zero, outputting a control signal to the wobbling angle control valves in order to maximize the quantity of the hydraulic fluid simultaneously with outputting control signals to the directional control solenoid valves and the solenoid valve, thereby allowing a temperature of the hydraulic fluid outputted from the main hydraulic pumps to rise by virtue of pressure loss occurring due to a resistance generated between the hydraulic fluid and the relief valves as the fluid passes through the relief valves; upon comparing a temperature of the hydraulic fluid rising as passing through the relief valves with a predetermined adjustable operational temperature, shutting off said control signals having been applied to the wobbling angle control valves and the solenoid valves in case that said temperature of the fluid is higher than said predetermined adjustable operational temperature; wherein the temperature of the hydraulic fluid is automatically preheated in order to reach to the predetermined adjustable operational temperature.

In another aspect, the above objects of this invention can be accomplished by providing a control method for controlling a control apparatus for automatically controlling the operation of a heavy construction comprising the steps of; upon detecting that said engine ON/OFF switch is positioned at an ON position, driving said throttle motor in order to set said throttle valve of the governor to a starting position simultaneously with turning on said fuel supply control valve; upon detecting that said engine ON/OFF switch is positioned at a START position, determining whether the control levers/pedals are positioned at neutral positions; in case that the control levers/pedals are positioned at neutral positions, turning on said start motor in order to start the engine, thereafter determining whether a rotative speed of the engine is over than a predetermined rotative speed; in case that said rotative speed of the engine is over than said predetermined rotative speed, turning off the start motor in order to stop the starting operation; upon detecting that the engine is not started, restarting the engine two or three times and also turning on said preheater in case that a temperature of the coolant of the engine is lower than a predetermined temperature.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a partial schematic circuit diagram showing a basic hydraulic circuit connected to a control system for operation of a heavy construction in accordance with the present invention; FIG. 2 is a flow chart showing a control method for automatically controlling a preheating operation for the heavy construction in accordance with this invention; FIG. 3 is a flow chart showing a control method for automatically controlling respective temperature of an engine coolant and a hydraulic fluid of the heavy construction in accordance with this invention;; FIG. 4 is a schematic block diagram showing a construction of a control apparatus for automatically and optimally controlling a starting operation for the engine of the heavy construction in accordance with this invention; FIG. Sa is a flow chart showing a control method for automatically and optimally controlling the starting operation in case of shifting the engine ON/OFF switch from an OFF position to an ON position; FIG. 5b is a flow chart showing a preheating sub-routine of FIG. 5a; FIG. 6 is a flow chart showing a control method for automatically and optimally controlling the starting operation in case of shifting the engine ON/OFF switch from the ON position to a START position; and FIG. 7 is a flow chart showing a control method for automatically and optimally controlling the starting operation in case of shifting the engine ON/OFF switch from the ON position to the OFF position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 which is a partial schematic circuit diagram showing a basic hydraulic circuit connected to a control system for operation of a heavy construction in accordance with the present invention, the hydraulic circuit is provided with a diesel engine 1, a pair of main hydraulic pumps, a first pump 2 and a second pump 3, each straightly connected to an output port la of the engine 1 in order to output hydraulic fluid to each actuator of the heavy construction. In addition, the second main hydraulic pump 4 is straightly connected to a sub-hydraulic pump, a third pump 4, for outputting a pilot hydraulic fluid for controlling quantity of the hydraulic fluid flow outputted from the main pumps 2 and 3 and a flow direction of the fluid.A directional control valve block 5 is connected to the main pumps 2 and 3 and comprises a plurality of directional control valves each for controlling the quantity of the hydraulic fluid flow from the main pumps 2 and 3 and a flow direction of the fluid for each actuator. The directional control valve block 5 is directly connected to a pair of logic valves 6 and a pair of solenoid valves 7 in order.

Additionally, the third hydraulic pump 4 is connected to a pair of wobbling angle control valves 2b and 3b so that the hydraulic fluid outputted from the third hydraulic pump 4 is applied to the control valves 2b and 3b in order to allow a pair of wobbling angle control members 2a and 3a to control the wobbling angles of the main hydraulic pumps 2 and 3. The hydraulic circuit of this invention is also provided with a solenoid valve 14 which is electrically connected to an output port of the controller 9 for controlling preset pressure of a pair of relief valves 8 each connected between the directional control valve block 5 and the main hydraulic pumps 2 and 3.

The relief valves 8 are adapted for preventing the hydraulic passage formed between the main pumps 2 and 3 and the directional control valve block 5 from being overloaded.

The controller 9 is electrically connected to the wobbling angle control valves 2b and 3b so that it outputs electric control signals to the solenoid control valves 2b and 3b in order to control the wobbling angles of the main pumps 2 and 3. The controller 9 is also electrically connected at its input port to a plurality of control levers/pedals 10 which allows the operate to manipulate them in order to control the operation of the actuator and outputs an electric signal corresponding to the manipulation values to the controller 9. An amplifier 11 is electrically connected between the controller 9 and the wobbling angle control valves 2b and 3b for amplifying an electric control signal, said signal having been operated in the controller 9 in accordance with the manipulation values of the control levers/pedals 10 and then outputted from the controller 9 to the control valves 2b and 3b.The controller 9 is electrically connected to a pair of temperature sensors, a first sensor 12a disposed at the diesel engine 1 for sensing a temperature of the engine coolant and a second sensor 12b disposed at the hydraulic pumps for sensing a temperature of the hydraulic fluid of the hydraulic pumps 2, 3 and 4.

On the other hand, the controller 9 is electrically connected at its output port to an alarm device 13 so that the controller 9 outputs an electrical alarm signal to the alarm device 13 upon having received an electric signal of each low temperature of the engine coolant and the hydraulic fluid from the temperature sensors 12a and 12b, thereby making the alarm device 13 to alarm the operator to the occurrence of low temperature, said temperature lower than a predetermined allowable minimum temperature. The solenoid valve 14 is electrically connected to the output port of the controller 9 so that it selectively controls respective preset pressure of the solenoid valves 7 and the relief valves 8.

The control system having the above mentioned construction provides a method for automatically preheating the engine coolant and the hydraulic fluid before normally starting the engine 1 in order to allow the temperature of the engine coolant and the hydraulic fluid to rise to respective desired temperature in a relatively short time. The method for preheating is described in detail in a flow chart of FIG.

2.

As described in the flow chart, the controller 9 receives at a step 30 a signal corresponding to temperature T of the hydraulic fluid of the pumps 2, 3 and 4 from the second temperature sensor 12b and then at a step 31 another signal corresponding to manipulation values el for the actuators from the control levers/pedals 10. Thereafter, the controller 9 performs an inquiry step 32 wherein it is determined whether the temperature T of the hydraulic fluid is lower than an allowable minimum temperature, 505C. If the temperature T is higher than or equal to the allowable minimum temperature 50'C, the process returns to the start step.However, if the temperature T is lower than the allowable minimum temperature 50'C, the controller 9 performs a next inquiry step 33 wherein it is determined whether the manipulation values ei of the control levers/pedals 10 is zero. If the values Gi of the control levers/pedals 10 is not zero, it is considered that the temperature T of the hydraulic fluid is so relatively lower as the operation of- the actuators according to the manipulation values ei can not be efficiently carried out.

Thus, the controller 9 outputs at a step 40 an electric alarm signal Ic to the alarm device 13 in order to alarm the operator to the lower temperature.

On the contrary, if the values ei of the control levers/pedals 10 is zero, the process simply proceeds to a next step 34 wherein a maximum control signal Imax is outputted from the controller 9 to the wobbling angle control valves 2b and 3b in order to allow the wobbling angles of the main pumps 2 and 3 to be changed in maximum. Thus, the main hydraulic pumps 2 and 3 output respective maximum quantity of hydraulic fluid flow Qlmax and Q2max. Thereafter, the controller 9 performs a step 36 wherein the controller 9 outputs respective electric signals Ia and Ib to the solenoid valves 7 and 14, respectively. Upon receiving the signal Ia, the solenoid valves 7 prevents the hydraulic fluid outputted from the main pumps 2 and 3 from draining into the drain tanks 15.On the other hand, the other solenoid valve 14 upon receiving the signal Ib from the controller 9 controls the preset pressure of the relief valves 8 to be equal to 80kg/cm2 so that the temperature of the hydraulic fluid from the main pumps 2 and 3 rises by virtue of pressure loss thereof occurring when it passes through the relief valves 8.

Upon having received an electric signal corresponding to a changing temperature T' of the hydraulic fluid from the sensor 12b at a step 36, the controller 9 performs a next inquiry step 36 wherein it is determined whether the changing temperature T' is equal to or higher than an adjustable operational temperature 55 C. If the changing temperature T' is lower than the adjustable temperature 55 C, the process returns to the step 34 in order to repeat the steps 34 to 36 until the temperature T' of the hydraulic fluid reaches to the adjustable temperature 55 C. However, if the changing temperature T' is equal to or higher than the adjustable operational temperature 55 C, the controller 9 performs continuous steps 38 and 39 in order to shut off the outputting of the electric signals Ia, Ib and Imax, thereby making the hydraulic circuit of this invention return to its original state.

As described above, the control system of this invention provides a method for automatically and optimally preheating the engine coolant and the hydraulic fluid of the heavy construction before a normal starting operation, thereby providing an advantage in that the engine coolant and the hydraulic fluid can be optimally preheated in order to reach to an adjustable operational temperature in a relatively short time.

In addition, the control system of this invention provides a method and an apparatus for automatically sensing respective temperature of the hydraulic fluid and engine coolant in case of occurrence of overheat exceeding respective predetermined overheat reference temperature, then alarming the operator to the occurrence of the overheat simultaneously with automatically changing the operational mode into another operational mode of relatively lower speed in order to cool the engine coolant and the hydraulic fluid, thereby efficiently preventing the engine coolant and the hydraulic fluid from being overheated and proving a continuous operation. The method and apparatus for controlling respective temperature of the coolant and the hydraulic fluid will be described in conjunction with the accompanying drawings.

As shown in FIG, 1, the controlling apparatus is provided with a speed control device for accelerating or reducing the driving speed of the engine 1. The device comprises an engine governor 17 provided in the engine 1, controlling the quantity of the fuel supplied to the engine 1, and a governor motor 18 connected between the engine governor 17 and the output port of the controller 9. The governor motor 18 comprises a DC motor or a step motor which can be driven at a rotative speed according to a current of a control signal applied from the controller 9 thereto.

In addition, the controller 9 is electrically connected to a select switch panel 20 for allowing the operator to select an operational mode and a speed sensing device 16 disposed at the output port la of the engine 1 for sensing an output rotative speed of the engine 1, said speed sensing device 16 electrically connected to the input port of the controller 9.

The switch panel 20 is provided with an operational mode select switch for selecting an operational mode depending upon a operational condition, an up/down switch for allowing the rotative speed of the engine 1 to be accelerated or reduced as required, an automatic reduction switch for reducing the rotative speed of the engine to a specific speed (for example, an idling speed) and another switches, each said switch orderly arranging on the switch panel 20. On the other hand, the speed sensing device 16 comprises a sensor such as a gear sensor which can detect signals each generating at every revolutions of a fly wheel of the engine 1 in order to output a signal corresponding tb the rotative speed of the engine 1 to the controller 9 after amplifying the signal.

Therefore upon receiving a signal, corresponding to a selected operational mode, and another signals from the select switch panel 20, the controller 9 operates the received values and then outputs an electric control signal to the governor motor 18 in order to control the quantity of the fuel supplied to the engine 1 by means of the engine governor 17. On the other hand, the controller 9 calculates a difference between an output rotative speed of the engine 1, outputted from the speed sensing device 16, and a preset objective reference speed in each operational mode. Thereafter, the controller 9 outputs a control signal to the wobbling angle control valves 2b and 3b by way of the amplifier 11 in order to control the wobbling angles of the main pumps 2 and 3, thereby always controlling the quantity of the hydraulic fluid flow.

FIG. 3 shows a flow chart of a method for controlling the overheated engine coolant and the overheated hydraulic fluid, said method performed by the control apparatus of FIG. 1.

As shown in the flow chart of FIG. 3, the controller 9 receives at first step 50 respective temperature TC and TH of the engine coolant and the hydraulic fluid from the temperature sensors 12a and 12b simultaneously with receiving a selected initial operational mode Mi from the select switch panel 20. Thereafter, the controller 9 performs continuous inquiry steps 51 and 52 wherein it is determined whether the respective temperature TC and TH each is higher than each overheat reference temperature, that is a reference temperature TA (85'C) for the coolant and the other reference temperature T8 (85' C) for the hydraulic fluid.If the respective temperature TC and TH each is not higher than each overheat reference temperature TA and Tg, it is considered that the operation of the heavy construction is normally carried out without occurrence of overheat. Thus, the process returns to the start step without controlling the temperature of the engine coolant and the hydraulic fluid. However, if even one of the respective temperature TC and TH is higher than the overheat reference temperature TA and TE, it is considered that the selected operational mode of the heavy construction is not adjustable, resulting in occurrence of overheat.Thus, the process proceeds to a next step 53 wherein the controller 9 outputs to the alarm device 13, such as an alarm lamp, an alarm buzzer or the like, in order to alarm the operator to the occurrence of the overheat in the engine coolant or the hydraulic fluid.

Then, the process proceeds to next continuous inquiry steps 54 and 55 wherein the controller 9 determines whether the respective temperature TC and TH each is higher than each allowable overheat temperature, that is an allowable temperature TAX (95'C) for the coolant and the other allowable temperature TeX (95'C) for the hydraulic fluid. If the respective reference temperature TC and TH each is not higher than each allowable overheat temperature TAX and T8x, it is considered that the operation of the heavy construction can be carried out somehow without occurrence of breakdown. Thus, the process returns to the start step without controlling the temperature of the engine coolant and the hydraulic fluid.

However, if even one of the respective temperature TC and is higher than the allowable overheat temperature TAX and TBX, it is considered that the selected operational mode of the heavy construction must be checked. Accordingly, the controller 9 performs a next inquiry step 56 wherein it is determined whether the present operational mode M is a L mode, a relatively lower speed operational mode. If the present operational mode M is not the L mode, the controller 9 performs continuous steps 57 and 58 in order to change the present operational mode into the L mode and then output an electric signal 1L to the governor motor 18 so as to control the engine governor 18 to reduce the quantity of the fuel for the engine, resulting in reducing the rotative speed of the engine 1.On the contrary, if the present operational mode M is the L mode, the process simply proceeds to a step 59.

Here, the controller 9 can output respective control currents corresponding to respective operational modes H, S and L, said currents resulting from a preset program thereof.

Therefore, the controller 9 outputs an electric control signal depending on the operational mode to the governor motor 18 so as to control the engine governor 18 to control the quantity of the fuel for the engine 1.

Owing to processing at steps 57 and 58, the rotative speed of the engine 1 is gradually reduced, thereby causing the temperature of the engine coolant and the hydraulic fluid to gradually lower. Therefore upon repeatedly checking the present operational temperature of the engine coolant and the hydraulic fluid until the present temperature lowers below a predetermined temperature, the controller 9 outputs an electric signal to the governor motor 18 in order to return the operational mode to the original mode. In other words, each lowered temperature Tc', TH' of the coolant and the hydraulic fluid is received at a step 59 by the controller 9, said temperature Tc', TH' is outputted as an electric signal from the temperature sensor 12a, 12b. At the same time, an electric signal corresponding to the present operational mode M is also received by the controller 9. Thereafter, the controller 9 performs next inquiry steps 60 and 61 wherein it is determined whether the respective temperature Tc' and TH' each is equal to or lower than each safety operational temperature, that is a safety temperature TSA (80 C) for the coolant and the other reference temperature TSe (95 C) for the hydraulic fluid. If even one of the respective temperature Tc' and TN' is higher than each safety temperature TSA, Ts, the controller e r 9 controls the governor motor 18 in order to continue the present operational mode, that is the L mode.

However, if the respective temperature Tc' and TH' each is equal to or lower than each safety temperature Ts, TS8, the controller 9 performs a next inquiry step 62 wherein it is determined whether the present operational mode M is the initial operational mode Mi. If the present operational mode M is not the initial operational mode Mi, at a step 63 the controller 9 changes the present operational mode M into the initial mode Mi. The controller 9 then controls at a step 64 the governor motor 18 in order to accelerate the rotative speed of the engine 1.

Here, upon receiving an electric control signal IL' from the controller 9, said control signal 11' corresponding to the initial operational mode Mi, the governor motor 18 controls the governor 17 in order to reduce the quantity of the fuel for the engine, thereby resulting in accelerating the rotative speed of the engine and returning the operational mode M to the initial mode Mi.

As described above, the control system of this invention provides an advantage in that the it automatically checks the operational temperature of the engine coolant and the hydraulic fluid by means of temperature sensors, and alarms the operator to the occurrence of overheat by means of an alarm device in case of detecting an overheat of the coolant and the hydraulic fluid, and also automatically controls the operational mode in order to remove the overheat, thereby efficiently preventing the temperature of the engine coolant and the hydraulic fluid from rising over a predetermined temperature.

Additionally, the control system of the present invention provides a method and an apparatus for automatically controlling the engine of the heavy construction in order to be always optimally started. The control method and apparatus will be described in detail in conjunction with the accompanying drawings.

FIG. 4 is a schematic block diagram showing a construction of the control apparatus for automatically and optimally controlling a starting operation for the engine of the heavy construction in accordance with this invention.

The controller 9 comprises a CPU 77, an input portion and an output portion. The input portion of the controller 9 comprises a pair of analog/digital signal converters 78 and 80 for converting input signals applied from the control levers/pedals 10 and the temperature sensors 12 to the controller 9, respectively, an analog/digital signal converter and counter 81 for converting and counting an input signal applied from the speed sensor 16 of the engine 1, and an input interface electrically connected to an engine ON/OFF switch 70. On the other hand, the output portion of the controller 9 comprises a ROM 82, a RAM 83, a pair of output interfaces, a first output interface 84 electrically connected to a first and second driving portions 85 and 86, a second output interface 87 electrically connected to a relay ay block 88.

Here, the engine ON/OFF switch 70 is adapted for allowing the operator to start or stop the operation of the engine 1 and outputting a signal corresponding to the starting or the stopping for the engine 1 to the controller 9. Also, the temperature sensor 12 senses a temperature of the coolant of the engine 1.

On the other hand, the first driving portion 85 of the controller 9 is electrically connected to a start motor 72 for starting the engine 1 in accordance with the starting signal outputted from the engine ON/OFF switch 70, while the second driving portion 86 is electrically connected to the governor motor 18, that is a throttle motor, for controlling a throttle valve of the governor 17 of the engine 1. Also, the relay block 88 of the controller 9 is electrically connected to a fuel supply control valve 74 controlling the quantity of the fuel supplied from a fuel tank to the governor 17, a D.C power supply 75 for supplying the D.C power to respective electric system of the engine 1, a preheater 76 for preheating the engine 1, and the alarm device 13 for alarming the operator to occurrence of problem in the control system.

In operation of the control apparatus of the above construction, upon manipulating the engine ON/OFF switch 70 in order to make the switch 70 shift from the Off position to the ON position, the throttle motor 18 is driven so as to set the throttle valve of the governor 17 to a start position simultaneously with turning on the fuel supply control valve 74 in order to allow the load on the engine 1 to be minimized, thereby accomplishing a preparation for starting.

Thereafter, upon shifting the engine ON/OFF switch from ON position to a START position, the controller 9 determines whether the control levers/pedals 10 each is positioned at the neutral position. If the control levers/pedals 10 each is not positioned at the neutral position, the controller 9 outputs an alarm control signal to the alarm device 13 in order to allow the operator to manipulate the control levers/pedals 10 from the present operational positions to the neutral positions. Upon detecting the manipulation of the control levers/pedals 10 from the operational positions to the neutral positions, the controller 9 starts the engine 1 by means of the start motor 72. At this time, if the engine 1 is not started at once, the controller 9 controls the start motor 72 in order to restart the engine 1 two or more times.In addition, in case that the engine 1 is not started due to a lower temperature of the coolant of the engine 1, the controller 9 outputs a signal to the preheater 76 by way of the second output interface 87 and the relay block 88 in order to preheat the coolant of the engine 1 until the temperature of the coolant reaches to a desired temperature, and then restarts the engine 1. The above-mentioned starting control method of this invention will be described in conjunction with flow charts of FIGS. 5 and 6.

First, a control method in case of shifting the engine ON/OFF switch 70 from the OFF position to the ON position will be described in conjunction with FIGS. 5a and 5b.

As shown in the flow chart of FIG. 5a, upon shifting the engine ON/OFF switch 70 from the OFF position to the ON position, the controller 9 turns on at a step 90 a relay 88 for the D.C power supply 75 by means of the second output interface 87, thereby turning on the D.C power supply 75. In result, the electric system of the engine 1 is applied with the D.C power from the power supply 75. Thereafter, a relay 88 for the fuel supply control valve 74 is turned on at a step 91 by means of the second output interface 87 of the controller 9 so that the fuel supply control valve 74 is opened in order to allow the fuel to be supplied from the fuel tank to the governor 17. Thereafter, the controller 9 performs an inquiry step 92 wherein, upon receiving a signal corresponding to a rotative speed of the engine 1 from the speed sensor 71 by way of the analog/digital signal converter and counter 81, it is determined whether the engine 1 is now driven. If the engine 1 is cfr i ven , the control process proceeds to the end step. However, if the engine 1 is not driven, the controller 9 performs a next step 93 wherein a pulse type of D.C voltage corresponding to the starting position is outputted from the CPU 77 to the first output interface 84 and the second driving portion 86 in order to drive the throttle motor 73 such as the step motor, thereby positioning the governor controlling throttle valve at the starting position.Thereafter, the controller 9 performs at a step 94 a subroutine for preheating the engine 1 such as described in a flow chart of FIG. 5b, and then ends the control process.

As described in the flow chart of FIG. 5b, the controller 9 first determines at a step 100 whether the start motor 72 is driven. If the start motor 72 is driven, the controller 9 performs a step 105 wherein the preheater 76 is turned off in order to end the control process. However, if the start motor 72 is not driven, the controller 9 performs a step 101 wherein it is determined whether the engine 1 is driven. If the engine 1 is driven, the controller 9 turns off the preheater 76 at the step 105 in order to end the control process.

However, if the engine 1 is not driven, the controller 9 receives at a next step 102 a signal corresponding to a temperature of the coolant of the engine 1 from the temperature sensor 12a. Upon receiving the signal of the coolant temperature from the sensor 12a, the controller determines whether the temperature of the coolant is equal to or lower than a predetermined temperature, -10-C. If the temperature is higher than the temperature of -10iC, the controller 9 performs the step 105 in order to end the control process. However, if the temperature of the coolant is equal to or lower than the temperature of -10 C, at a step 104 the controller 9 turns on the preheater 76 in order to preheat the engine 1, and then ends the preheating control process.

FIG. 6 is a flow chart showing a control process for automatically and optimally controlling the starting operation in case of shifting the engine ON/OFF switch 70 from the ON position to a START position.

Referring to the flow chart, the controller 9 first checks at a step 110 a signal corresponding to manipulation values of the control levers/pedals 10 having been received by the analog/digital signal converter 78 in order to determine whether the control levers/pedals 10 are positioned at the neutral positions. If the control levers/pedals 10 are not positioned at the neutral positions, it is considered that, in case of starting the engine 1, the engine 1 will be overloaded due to the quantity of the hydraulic fluid which will be outputted from the hydraulic pumps 2 and 3 to respective actuators as the engine 1 is started. Thus, the controller 9 outputs at a step 111 an alarm control signal to the alarm device 13 in order to alarm the operator to the necessity of shifting the control levers/pedals 10 from the operational positions to the neutral positions.

However, if the control levers/pedals 10 are positioned at the neutral positions, the controller 9 performs a next step 112 wherein the controller 9 turns on the start motor 72 such as the D.C motor by way of the first output interface 84 and the first driving portion 85 thereof. Thereafter, upon having received a signal corresponding to the rotative speed of the engine 1 from the seep sensor 16 of the engine 1, the controller 9 determines at a step 113 wherein it is determined whether the rotative speed of the engine 1 is equal to or over than a predetermined speed, 600rpm. If the rotative speed of the engine 1 is equal to or over than the speed of 600rpm, the start motor 72 is turned off at a step 114. Thereafter, the controller 9 performs a step 115 wherein it is determined whether the preheater 76 is turned on.If the preheater 76 is turned on, the controller 9 turns off the preheater 76 at a step 116 and then ends the process, while the controller 9 simply ends the process if the preheater 76 is turned off.

On the other hand, if the rotative speed of the engine 1 is lower than the speed of 600rpm, the controller 9 performs a step 117 wherein it is determined whether 5 seconds have been lapsed under the condition that the rotative speed of the engine 1 is continuously lower than 600rpm. If the rotative speed of the engine 1 after lapsing of 5 seconds is equal to or over than 600 rpm, the controller 9 repeatedly performs the step 113, while the controller 9 performs a next step 118 if the 5 seconds have been lapsed under the condition that the rotative speed of the engine 1 is continuously lower than 600rpm. Upon restarting the engine 1 two or three times, the controller 9 determines at the step 118 whether the rotative speed of the engine 1 is equal to or over than the speed of 600 rpm by virtue of restarting three times.If the rotative speed of the engine 1 is equal to or over than the speed of 600 rpm after restarting of three times, the start motor 72 is turned off at a step 120. Thereafter, the controller 9 determines at a next inquiry step 121 wherein 25 seconds have been lapsed after turning off the start motor 72. If the 25 seconds have been lapsed, the process returns to the step 112.

However, if the 25 seconds have not been lapsed, the step 121 is repeatedly performed until the 25 seconds have been lapsed.

On the other hand, if the result rotative speed of the engine 1 is lower than the speed of 600 rpm even though the engine 1 has been repeatedly restarted three times, the controller 9 outputs at a step 119 an alarm control signal to the alarm device 13 in order to cause the alarm device 13 to alarm, and then the controller 9 performs the step 120.

FIG. 7 is a flow chart showing a control method for the starting operation in case of shifting the engine ON/OFF switch 70 from the ON position to the OFF position. As represented in this flow chart, at a first step 130 the controller 9 turns off the D.C power supply 75. Thereafter, the fuel supply valve 74 is turned off at a step 131 in order to stop the operation of the engine 1. As described above, the control system of this invention provides advantages in that the engine of the heavy constriction automatically controlled in order to be always optimally started. Although the preferred embodiments of the present invention have been disclosed for illustrative purpose, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A control method for controlling a control apparatus for automatically controlling the operation of a heavy construction, said control apparatus comprising an engine; a plurality of actuators, an electronic controller for controlling the operation of said actuators; main hydraulic pumps for supplying hydraulic fluid for said actuators; a sub-hydraulic pump for supplying pilot hydraulic fluid; positional sensors provided at respective actuators in order to sense positional displacement values of said actuators; a directional control valve block connected to said main hydraulic pumps and said electronic controller for controlling operational direction of said actuators and also quantity of said hydraulic fluid flow; wobbling angle control valves disposed between the controller and the main pumps in order to control said quantity of hydraulic fluid flow outputted therefrom; control levers/pedals for outputting respective electric signals corresponding to handling values for actuators to the controller; an amplifier disposed between the controller and said wobbling angle control valves for amplifying an electric signal outputted from the controller to the wobbling angle control valves; relief valves disposed at a hydraulic passage between the directional control valve block and the main hydraulic pumps for preventing said hydraulic passage from being overloaded; directional control solenoid valves each connected to the directional control valve block; a solenoid valve disposed among the controller, the directional control solenoid valves and the relief valves for selectively controlling each preset pressure of the directional control solenoid valves and the relief valves; means for sensing respective temperature of a coolant of the engine and the hydraulic fluid, said means disposed at the engine and the hydraulic pumps, respectively, said control method comprising the steps of: upon receiving a temperature of the hydraulic fluid from said means for sensing temperature and also receiving manipulating values for the actuators from the control levers/pedals, comparing said temperature of the hydraulic fluid with a predetermined allowable minimum temperature and determining whether said manipulating values are zero;; in case that the temperature of the hydraulic fluid is lower than said predetermined allowable minimum temperature and also the manipulating values are zero, outputting a control signal to the wobbling angle control valves in order to maximise the quantity of the hydraulic fluid simultaneously with outputting control signals to the directional control solenoid valves and the solenoid valve, thereby allowing a temperature of the hydraulic fluid outputted from the main hydraulic pumps to rise by virtue of pressure loss occurring due to a resistance generated between the hydraulic fluid and the relief valves as the fluid passes through the relief valves;; upon comparing a temperature of the hydraulic fluid rising as passing through the relief valves with a predetermined adjustable operational temperature, shutting off said control signals having been applied to the wobbling angle control valves and the solenoid valves in case that said temperature of the fluid is higher than said predetermined adjustable operational temperature; wherein the temperature of the hydraulic fluid is automatically preheated in order to reach to the predetermined adjustable operational temperature.

2. A control method for controlling a control apparatus for automatically controlling the operation of a heavy construction, said control apparatus comprising an engine; a plurality of actuators; an electronic controller for controlling the operation of said actuators; main hydraulic pumps for supplying hydraulic fluid for said actuators; a sub-hydraulic pump for supplying pilot hydraulic fluid; positional sensors provided at respective actuators in order to sense positional displacement values of said actuators; a directional control valve block connected to said main hydraulic pumps and said electronic controller for controlling operational direction of said actuators and also quantity of said hydraulic fluid flow; wobbling angle control valves disposed between the controller and the main pumps for controlling wobbling angles of the main hydraulic pumps in order to control said quantity of hydraulic fluid flow outputted therefrom; control levers/pedals for outputting respective electric signals corresponding to handling values for actuators to the controller; said controller electrically connected to an engine ON/OFF switch for outputting a signal corresponding to starting and stopping of operation of the engine, a start motor for driving the engine in accordance with the starting signal outputted from said ON/OFF switch, a throttle motor for controlling a throttle valve of a governor of the engine, means for sensing a rotative speed of the engine, means for sensing a temperature of a coolant of the engine, a fuel supply control valve for controlling the fuel supplied from a fuel tank to said governor of the engine, a D.C. power supply for supplying D.C. power to an electric system of the engine, a preheater for preheating the engine, and an alarming device for alarming the operator to a state of problem, said control method comprising the steps of;; upon detecting that said engine ON/OFF switch is positioned at an ON position, driving said throttle motor in order to set said throttle valve of the governor to a starting position simultaneously with turning on said fuel supply control valve; upon detecting that said engine ON/OFF switch is positioned at a START position, determining whether the control levers/pedals are positioned at neutral positions; in case that the control levers/pedals are positioned at neutral positions, turning on said start motor in order to start the engine, thereafter determining whether a rotative speed of the engine is over than a predetermined rotative speed; in case that said rotative speed of the engine is over than said predetermined rotative speed, turning off the start motor in order to stop the starting operation;; upon detecting that the engine is not started, restarting the engine two or three times and also turning on said preheater in case that a temperature of the coolant of the engine is lower than a predetermined temperature.

3. A control apparatus for automatically controlling the operation of a heavy construction comprising an engine; a plurality of actuators; an electronic controller for controlling the operation of said actuators; main hydraulic pumps for supplying hydraulic fluid for said actuators; a sub-hydraulic pump for supplying pilot hydraulic fluid; positional sensors provided at respective actuators in order to sense positional displacement values of said actuators; a directional control valve block connected to said main hydraulic pumps and said electronic controller for controlling operational direction of said actuators and also quantity of said hydraulic fluid flow; wobbling angle control valves disposed between the controller and the main pumps for controlling wobbling angles of the main hydraulic pumps in order to'control said quantity of hydraulic fluid flow outputted therefrom; control levers/pedals for outputting respective electric signals corresponding to handling values for actuators to the controller; an amplifier disposed between the controller and said wobbling angle control valves for amplifying an electric signal outputted from the controller to the wobbling angle control valves; relief valves disposed at a hydraulic passage between the directional control valve block and the main hydraulic pumps for preventing said hydraulic passage from being overloaded; directional control solenoid valves each connected to the directional control valve block; a solenoid valve disposed among the controller, the directional control solenoid valves and the relief valves for selectively controlling each preset pressure of the directional control solenoid valves and the relief valves; the control apparatus further comprising: means for sensing respective temperature of a coolant of the engine and the hydraulic fluid, said means disposed at the engine and the hydraulic pumps, respectively; means for alarming the operator to occurrence of overheat in accordance with a control signal from the controller in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, said means electrically connected to the controller;; means for accelerating and reducing a rotative speed of the engine, said means relatively reducing said rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, and then accelerating the rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is lower than each predetermined safety operational temperature, said means electrically connected to the controller; wherein each operational temperature of the coolant of the engine and the hydraulic fluid is automatically controlled.

4. A control apparatus for automatically controlling the operation of a heavy construction according to claim 3, wherein said means for accelerating and reducing the rotative speed of the engine comprises a motor electrically connected to the controller and adapted for being driven in accordance with a control signal outputted from the controller, and a governor disposed at the engine and electrically connected to said motor for controlling the quantity of a fuel supplied to the engine in order to accelerating or reducing the rotative speed of the engine.

5. A control method for controlling a control apparatus for automatically controlling the operation of a heavy construction, said control apparatus comprising an engine; a plurality of actuators; an electronic controller for controlling the operation of said actuators; main hydraulic pumps for supplying hydraulic fluid for said actuators; a sub-hydraulic pump for supplying pilot hydraulic fluid; positional sensors provided at respective actuators in order to sense positional displacement values of said actuators; a directional control valve block connected to said main hydraulic pumps and said electronic controller for controlling operational direction of said actuators and also quantity of said hydraulic fluid flow; wobbling angle control valves disposed between the controller and the main pumps for controlling wobbling angles of the main hydraulic pumps in order to control said quantity of hydraulic fluid flow outputted therefrom; control levers/pedals for outputting respective electric signals corresponding to handling values for actuators to the controller; an amplifier disposed between the controller and said wobbling angle control valves for amplifying an electric signal outputted from the controller to the wobbling angle control valves; relief valves disposed at a hydraulic passage between the directional control valve block and the main hydraulic pumps for preventing said hydraulic passage from being overloaded; directional control solenoid valves each connected to the directional control valve block; a solenoid valve disposed among the controller, the directional control solenoid valves and the relief valves for selectively controlling each preset pressure of the directional control solenoid valves and the relief valves; means for sensing respective temperature of a coolant of the engine and the hydraulic fluid, said means disposed at the engine and the hydraulic pumps, respectively; means for alarming the operator to occurrence of overheat in accordance with a control signal from the controller in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, said means electrically connected to the controller; means for accelerating and reducing a rotative speed of the engine, said means relatively reducing said rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is higher than each predetermined reference overheat temperature, and then accelerating the rotative speed of the engine in case that each temperature of the coolant and the hydraulic fluid is lower than each predetermined safety operational temperature, said means electrically connected to the controller, the control method comprising the steps of:: upon receiving each temperature of the coolant and the hydraulic fluid from the means for sensing the temperature and also receiving an initial operational mode of the heavy construction, comparing each said temperature with each predetermined reference overheat temperature in order to output an alarm signal to said means for alarming; upon receiving each present temperature of the coolant and the hydraulic fluid from the means for sensing the temperature and also receiving a present operational mode of the heavy construction, comparing each said present temperature with each predetermined safety operational temperature and comparing said present operational mode with said initial operational mode; wherein each operational temperature of the coolant of the engine and the hydraulic fluid is automatically controlled.

6. A control apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.