Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2000-04-21
2001-12-25
Dolinar, Andrew M. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S030000
Reexamination Certificate
active
06334085
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a data processing unit for a construction machine for collecting and processing data on the load condition of the engine of a construction machine.
BACKGROUND ART
It is very important for construction machines such as hydraulic shovels and bulldozers to accurately estimate a timing of engine overhaul, that is, the operation life of the engine in order to carry out engine maintenance and inspection in accordance with a set schedule. However, there are difficulties in individually estimating the engine life of vehicles, because the engine life of construction machines varies significantly depending on their working situations and operating conditions even if they are of the same type and have the same type engines.
One attempt was previously made in which data on the load condition of an engine are collected over a long period of time and engine life is estimated from changes with time in the load condition. This method is effective where the engine is continuously operated under a constant load, but it has encountered considerable difficulties when applied to cases where engine load changes with time.
The present applicant has proposed one solution to the above problem in a previous invention (entitled “A device for estimating the life of a machine having an engine and heat source”, Japanese Patent Publication (KOKAI) Gazette No. 11-211622 (1999)). In this prior invention, the values of operation parameters indicative of the load imposed on an engine are classified into a plurality of levels thereby setting a load map; the time of detecting a parameter value belonging to each level of the load map is accumulated; the actual amount of damage to the engine is calculated based on the accumulated time; and the engine life corresponding to the calculated amount of damage is obtained from preset data indicative of the relationship between the degree of damage and the length of life. As the operation parameters mentioned herein, the rotational speed of an engine, output torque (or the amount of fuel injection) and the like are selected.
In the previous invention, while detection data from an engine rotational speed sensor mounted for controlling basic performance can be utilized in the detection of the rotational speed of the engine, a specialized sensor such as a rack position sensor or pump swash plate sensor needs to be newly adapted for the detection of output torque. This results in increased cost.
On the other hand, there is a technique for estimating output torque without addition of a specialized sensor. Concretely, a nominal line in an engine output characteristic graph such as shown in FIG.
9
(
a
) is stored in the controller beforehand, and an output torque T′ is estimated from an actual rotational speed Na detected by an engine rotational speed sensor. This estimation technique however has revealed a difficulty in ensuring detection accuracy because there occurs reversal in the relationship between detected load and actual load such as shown in FIG.
9
(
b
). More specifically explaining with reference to FIG.
9
(
b
), when comparing the two engine data represented by chain lines A and B which vary in regulation relative to the ideal line represented by solid line, the relationship between actual torque T(A) and actual torque T(B) relative to engine rotational speeds Na(A) and Na(B) is represented by T(A)>T(B), whereas the relationship between estimated torque T′(A) and estimated torque T′(B) is represented by T′(A)<T′(B). As understood from this, the actual torque relationship is opposite to the estimated torque relationship.
The invention has been directed to overcoming the above problems and a primary object of the invention is therefore to provide a data processing unit for a construction machine, the unit being capable of storing data on load condition independently of variations in engine output torque and performing data processing such as estimation of the operation life of an engine based on the stored data, without additionally incorporating a sensor which entails increased cost.
DISCLOSURE OF THE INVENTION
The above object can be achieved by a data processing unit for a construction machine according to the invention, which collects and processes data on the load condition of an engine of the construction machine, the unit comprising:
(a) detecting means for detecting the rotational speed of the engine when no load is imposed on the engine and the actual rotational speed of the engine;
(b) load map setting means for setting a load map based on the rotational speed when no load is imposed and the actual rotational speed which have been detected by the detecting means, by dividing combinations of first parameter values and second parameter values into a plurality of regions, the first parameter values being the values of the rotational speed when no load is imposed while the second parameter values being the values of the difference between the rotational speed when no load is imposed and the actual rotational speed; and
(c) calculating and storing means for accumulating the time of detecting the first parameter value and second parameter value of each region in the load map set by the load map setting means until a certain time elapses and for storing the result of the accumulation for each region in the load map.
According to the invention, the rotational speed of the engine when no load is imposed on the engine and the actual rotational speed of the engine are detected by the detecting means. Based on these detected rotational speeds, combinations of first parameter values and second parameter values are divided into a plurality of regions according to levels in order to set a load map representative of the load condition of the engine. The first parameter values are the values of the rotational speed of the engine when no load is imposed thereon, whereas the second parameter values are the values of the difference between the rotational speed of the engine when no load is imposed thereon and the actual rotational speed of the engine. The detecting time of the first parameter value and the second parameter value of each region in the load map is accumulated until a certain period of time elapses. The result of this accumulation for every region of the load map is stored. In the invention, sensors such as an engine rotational speed sensor and governor position sensor which are conventionally used for basic performance control can be utilized for obtaining the first and second parameters, so that data on the load condition of the engine can be obtained without adaptation of an additional sensor which entails increased cost. Unlike the conventional techniques, the invention does not detect the absolute value of engine load (output horse power), but is designed to store, as a load map, the relationship between the rotational speed when no load is imposed and the difference between the rotational speed when no load is imposed and the actual rotational speed and to allow the load map to be recognized as a pattern. Therefore, the load condition of the engine can be stored without being affected by detection accuracy and the reversal phenomenon in a plurality of data pieces can be prevented.
According to the concept of the invention, point P
1
(high throttle and high load), point P
2
(high throttle and low load), point Q
1
(low throttle and high load) and point Q
2
(low throttle and low load) in the graph of engine rotational speed (Na) versus torque (T) such as shown in FIG.
1
(
a
) are phase-shifted to points P
1
′, P
2
′, Q
1
′, and Q
2
′ in the load map (shown in FIG.
1
(
b
)) showing the relationship between the rotational speed when no load is imposed and the difference between the rotational speed when no load is imposed and the actual rotational speed. Therefore, even if the output torque of the engine varies, only the absolute values of N
0
-Na and N
0
change but the map pattern does not change so that there does not arise the problem of the prior
Haga Seiya
Kawamura Koichi
Armstrong, Westerman, Hattori, McLeland & Naughton, LLP.
Dolinar Andrew M.
Komatsu Ltd
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