JPH022909Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a main bearing monitoring device for an internal combustion engine such as a diesel engine.

For example, a conventional method often used to monitor the main bearings of diesel engines is to measure the temperature of the bearings and determine whether there is an abnormality in the main bearings based on temperature abnormalities. However, this method requires at least as many sensors as there are bearings (usually it is necessary to install sensors at several locations on one bearing), and has the disadvantage that the installation and wiring work is extremely complicated.

Furthermore, as a device for detecting an abnormality in a bearing of a motor or the like, a method using electrical resistance has conventionally been used. However, this device determines an abnormality based on the magnitude of the resistance value itself, and is not suitable as a method of abnormality detection for something that is constantly subjected to a synchronously fluctuating load, such as the main bearing of a diesel engine.

Therefore, this invention was devised to eliminate the above-mentioned drawbacks, and by measuring and processing the electrical resistance between the crankshaft and the crankcase, the main bearing, which is subject to constantly fluctuating loads, can be easily An object of the present invention is to provide a main bearing monitoring device for an internal combustion engine that can monitor abnormalities in the engine.

Therefore, in order to achieve this objective, the main bearing monitoring device for an internal combustion engine of this invention includes a means for measuring and processing the electrical resistance waveform between the main shaft and the main shaft case of the internal combustion engine, and a means for measuring the electrical resistance waveform between the main shaft and the main shaft case of the internal combustion engine. The time ratio between the time T of one cycle every two rotations and the total time T _N of the waveform portion of the electrical resistance waveform subjected to the waveform processing whose resistance value is less than a certain resistance value in this one cycle time ξ = T _N /T and determines whether there is an abnormality in the main bearing based on the magnitude of the time ratio;
It is characterized by having the following.

This invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a block diagram showing the main bearing monitoring device of this invention. 1 is an internal combustion engine, for example a 4-cycle diesel engine (hereinafter referred to as engine),
A load L such as a generator is connected to a crankshaft 2 which is the main shaft of the engine 1.

From the crankshaft 2 and crankcase 3,
Signal line to obtain electrical resistance waveform RW ₀ between the two
SL ₁ and SL ₂ are derived and connected to the amplification circuit 4. This amplification circuit 4 is connected to a comparator circuit 6 via a low-pass filter circuit 5.

Further, a constant voltage circuit 8 is connected to the signal line SL ₁ on the crankshaft 2 side via a reference resistor 7.
This constant voltage circuit 8 is connected to the comparator 6 via a set voltage circuit 9 for setting a voltage corresponding to an arbitrary set resistance value R ₀ . This comparator 6 compares the set resistance value R ₀ with the electric resistance shaping waveform RW ₂ outputted from the low-pass filter circuit 5, and generates a comparator waveform RW ₃ that is only less than the set resistance value R ₀ .

On the other hand, a signal line SL ₃ is led out from a rotation sensor 10 that detects the rotation of the crankshaft 2.
The configuration is such that a pulsed rotation detection signal _S1 is obtained at intervals of one period T [sec] every rotation or every two rotations. Then, in the rotation acquisition circuit 11 connected to this signal line SL ₃ , the rotation detection signal
_S1 is pulse-shaped into a rotation detection signal _S2 of one period T [sec].

Counter circuits 12 and 13 are connected to the latter stages of the comparator circuit 6 and rotation acquisition circuit 11, respectively, and both counter circuits 12 and 13 have a system clock that provides a clock signal Cp for synchronization. A power supply circuit 14 is connected thereto.
A calculation and determination circuit 15 and a circuit 16 that issues an alarm when the calculation and determination circuit 15 determines that an unillustrated bearing of the crankshaft 2 is abnormal are connected to the downstream of the counter circuits 12 and 13. As shown in FIGS. 1 and 2, the counter circuit 12 operates only during times T ₁ , T ₂ , ..., Tn of each waveform component of the comparator waveform RW ₃ generated by the comparator circuit 6. , the input clock signal Cp of the system clock circuit 14 is counted. In addition, counter circuit 1
3 is designed to count the clock signal Cp during one cycle T of the rotation detection signal _S2 generated from the rotation acquisition circuit 11.

Further, the calculation determination circuit 15 calculates the count number Ncp counted by the counter circuit 13 in one period T [sec] and the count number Ncp counted by the counter circuit 12 in one period T [sec].
T _N of comparator waveform RW ₃ during [sec] =
Number of counts to be counted in time T ₁ +T ₂ +……+Tn
n _cp and the time ratio ξ is obtained by the following formula,
Comparing this time ratio ξ with a preset limit value (experimentally determine the limit value of the time ratio at which the bearing of the crankshaft 2 becomes abnormal), the time ratio ξ > the limit value. In the case of the condition, it is determined that the bearing is abnormal, and an alarm signal S _A is output to the alarm circuit 16.

Time ratio ξ=n _cp /Ncp =T ₁ +T ₂ +...+Tm/T=T _N /T Next, the operation of the apparatus with the above configuration will be explained.

Electrical resistance waveform between the crankshaft 2 and crankcase 3 of the engine 1 that rotationally drives the load L
RW ₀ is input to the amplification circuit 4 through the signal lines SL ₁ and GL ₂ and its amplitude is amplified, resulting in an electric resistance waveform RW ₁
Furthermore, the high frequency component is cut off at a predetermined cut-off frequency by the low-pass filter 5, and the waveform is shaped into an electrical resistance shaping waveform _RW2 , which is then input to the comparator circuit 6. In this comparator circuit 6, the electrical resistance shaping waveform RW ₂
is compared with an arbitrary setting resistance value R ₀ set in the setting voltage circuit ₉ , and as shown in _FIG . It is input to the 12 side. Then, in the counter circuit 12, for example, taking advantage of the periodicity, the times T ₁ , T ₂ , . . . of each waveform component of each comparator waveform RW ₃ are determined.
The clock signal Cp input only during the total time T _N of ..., T _o is counted.

On the other hand, from the rotation sensor 10, the crankshaft 2
A rotation detection signal S 1 is obtained at an interval of one period T [sec] every one or two rotations of , and is captured as a rotation detection signal _{S 2 in} the rotation acquisition circuit 11 and inputted to the counter circuit 13 . Ru.

In the counter circuit 13, the clock signal Cp during one period T is counted to obtain a count number.
Becomes NCP.

Therefore, in the arithmetic judgment circuit 15, the counter circuit 13 calculates the count number Ncp counted in one period T, and the counter circuit 12 calculates the count number Ncp counted in one period [sec].
_{T N} of comparator waveform RW ₃ between
The time ratio ξ=n _cp /Ncp is calculated from the number of counts n _cp counted during the time T ₂ +...+T _o .

At this time, if an abnormality occurs such as damage to the bearing of the crankshaft 2, the chances of metal contact between the crankshaft 2 and the crankcase 3 increase, and the crankshaft 2
The electrical resistance between and crankcase 3 changes,
The time ratio ξ=n _cp /Ncp becomes greater than or equal to a predetermined limit value.

In this case, an alarm signal is sent from the arithmetic judgment circuit 15.
S _A is output to activate the alarm circuit 16 and issue an alarm.

By the way, the crankshaft 2 is subjected to varying loads due to explosive force and inertial force during operation of the engine 1, but if an abnormality is determined based on the magnitude of the electrical resistance value itself as in the past, it is easy to make an error in the determination. However, in this invention, one period T of one or two rotations of the crankshaft 2 is set as the denominator, and the total time T _N of each waveform component of the comparator waveform RW ₃ in one period T is set as the numerator. Since the abnormality of the bearing is determined based on the magnitude of the time ratio ξ calculated from both, bearings can be easily monitored without causing errors in abnormality judgment even if the engine 1 receives a large fluctuating load during operation. can. In the above-mentioned embodiment, the main bearing monitoring of a diesel engine was described, but it goes without saying that the present invention is not limited to this and can be applied to other types of engines such as gasoline engines.

As explained above, according to this invention, the periodic electrical resistance waveform between the main shaft (crankshaft) and the main shaft case (crankcase) can be measured and processed simply by simple wiring. It has an excellent effect of monitoring abnormality and normality of the main bearing, which is constantly subjected to periodic and fluctuating loads. It goes without saying that this device can be made practical even without a rotation sensor by arbitrarily setting the time of one cycle T to be relatively long regardless of rotation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main bearing monitoring device of this invention, and FIG. 2 is a diagram showing comparator waveforms. 1... Diesel engine, 2... Crankshaft, 3
... Crank case, L ... Load, 6 ... Comparator circuit, 12, 13 ... Counter circuit, 15
...Arithmetic judgment circuit.

Claims (1)

[Claims for Utility Model Registration] Means for measuring and processing the electrical resistance waveform between the main shaft and the main shaft case of an internal combustion engine, the time T of one cycle for every one or two rotations of the engine, and the time T of one cycle for each revolution of the engine, and the length of this one cycle. Calculate the time ratio ξ=T _N /T between the total time T _N of the waveform component whose resistance value is less than a certain resistance value of the electrical resistance waveform processed, and depending on the magnitude of this time ratio, the main bearing A main bearing monitoring device for an internal combustion engine, comprising: arithmetic and determining means for determining an abnormality.