JP2001324359A - Reverse flow detector for fluid circuit and mist lubrication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect reverse flow due to a defective check valve. SOLUTION: In a fluid circuit constructed by arranging a pipe 30 led from a fluid storage tank 10 to a predetermined fluid supply position (a venturi nozzle 20, for example) and provided with at least on check valve 31 (32) in this predetermined position and connecting a pump 40 to the pipe 30, a sensor 50 consisting of an electrical resistance element whose resistance value is changed when heat is taken away by fluid is arranged in the pipe 30, while a sensor output is monitored by an abnormal condition detecting means 60, and when the sensor output is detected during a stopping duration of the pump 40, an abnormal condition signal is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a backflow of a fluid circuit, and more particularly to a device for supplying a fluid such as lubricating oil to a predetermined location by a pump through a check valve. The present invention relates to a backflow detection device for a fluid circuit suitable for a mist lubrication device or the like, which detects a backflow of a fluid.

[0002]

2. Description of the Related Art Referring to FIG. 4, when lubricating oil in a tank T is pumped up by, for example, a piston pump P and supplied to a predetermined lubrication point, in most cases, the suction side and the discharge side of the piping are connected to each other. The check valves (check valves) CV1 and CV2 are respectively inserted into the power supply units.

That is, during the suction operation of the pump P, the suction side check valve CV1 is opened and the discharge side check valve CV2 is closed. On the other hand, at the time of the discharge operation of the pump P, the suction side check valve CV1 is closed, and the discharge side check valve CV2 is opened. Pump P
, Both check valves CV1 and CV2 are closed.

In this way, the backflow in the pipe is prevented. However, even when lubricating oil is continuously supplied by, for example, a gear pump or the like, a check valve is provided to prevent the backflow when the gear pump is stopped. May be used. In this case, the number of the check valve may be one, and the connection point of the gear pump may be either the suction side or the discharge side of the check valve.

[0005]

However, the check valve is not perfect. For example, due to deterioration of the mechanism and material, and the inclusion of foreign matter contained in the lubricating oil, etc.
In some cases, backflow is allowed.

[0006] When a backflow occurs in the check valve, particularly when the pump is operated intermittently, the lubricating oil in the pipe returns to the tank side, which seriously affects the lubrication at the lubricating point. Also, in the case where the lubricating oil is discharged from the distribution valve in a fixed amount, if the check valve is defective, the discharge amount decreases or does not come out, causing the same problem as described above.

[0007]

According to the present invention, a backflow due to a check valve failure can be reliably detected. The present invention is applicable to all fluid circuits having a check valve, but is suitable for a lubricating oil supply system, especially a mist lubricating device that atomizes lubricating oil and accurately supplies a certain amount of the atomized lubricating oil.

That is, the present invention has a pipe which is guided from a fluid storage tank to a predetermined fluid supply point, and has at least one check valve provided at the predetermined position,
In a backflow detecting device for detecting a backflow of the fluid circuit formed by connecting a pump to the pipe during the pump stop period, an electric resistance which is inserted into the pipe and whose resistance value changes due to heat being taken away by the fluid. A sensor comprising an element, and abnormality detection means for monitoring an output signal of the sensor and outputting an abnormality signal when the output signal appears within the pump stop period.

This type of sensor (electric resistance element) includes:
There is a thermistor well known as a negative characteristic resistance element. In this case, the thermistor is used by being connected to a constant current circuit. However, when heat is removed by the fluid, the resistance value increases, and the amount of self-heating changes accordingly. Since the self-heating amount is proportional to the flow rate of the fluid, an output voltage signal proportional to the flow rate of the fluid can be obtained by integrating the current required for the heat generation by the capacitor.

If the check valve is functioning normally,
While the pump is stopped, little fluid flows in the piping. However, if the check valve is defective,
Since the fluid continues to flow even while the pump is stopped, an output signal is output from the sensor, whereby it is determined that there is a backflow.

[0011] Even during the operation of the pump, an output signal is output from the sensor. Therefore, it is necessary to determine the output signal during the pump operation and the output signal due to the backflow. Therefore, the abnormality detecting means includes: a first pulse generation circuit that generates an operation interval pulse of the pump; a second pulse generation circuit that receives the operation interval pulse and provides a discharge operation time pulse to the pump; A third pulse generation circuit that outputs an inverted pulse in synchronization with the ejection operation time pulse, a comparison circuit that generates an output pulse when an output signal of the sensor exceeds a predetermined threshold level, It is preferable that the output pulse is ANDed to output an abnormal signal.

The check valve may allow backflow due to an accidental element, for example, bubbles or accidental dust adhering to the lubricating oil. It is preferable that such a one-time cause be overlooked. for that reason,
In the present invention, a first counting circuit that counts the number of appearances of the abnormal signal is connected to the output stage of the AND circuit, and when the number of occurrences exceeds a first reference count value set in advance, An abnormal signal is generated for the first time.

The abnormality detecting means monitors the output signal of the sensor over the entire period during which the fluid circuit is operating. As described above, the first abnormality signal is overlooked and the abnormal signal is counted for a predetermined number of times. If a true abnormal signal is output when the operation is performed, it is necessary to reset the pump once when the number of times of operation of the pump reaches a predetermined number.

Therefore, in the present invention, the second counting circuit for counting the operation interval pulse and the first counting circuit when the count value of the second counting circuit reaches a preset second reference count value. And a reset circuit for applying a reset pulse for clearing the respective count values to the second counting circuit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described. FIG. 1 schematically shows a mist lubricating apparatus to which the present invention is applied.

The mist lubricating apparatus basically includes a tank 10 for storing lubricating oil, a Venturi nozzle 20 for atomizing the lubricating oil, a pipe 30 extending from the tank 10 to the Venturi nozzle 20, and a pipe 30. And a pump 40 connected thereto.

The pipe 30 is provided with check valves 31 and 32 on the suction side and the discharge side, respectively, and the pump 40 is connected to a pipe portion between the check valves 31 and 32. In this example, a piston pump that repeats suction and discharge is used as the pump 40.

The venturi nozzle 20 includes an inner cylinder nozzle 21 to which lubricating oil is supplied from a pipe 30 and an inner cylinder nozzle 2.
And an outer cylinder nozzle 22 arranged to surround the outer cylinder 1, and compressed air is supplied to the outer cylinder nozzle 22 from a pressurized air source (not shown). The outer cylinder nozzle 22 is the inner cylinder nozzle 21.
A throat portion 221 is provided near the lower end of the throat, and a diffusion chamber 222 having a large number of ejection holes is continuously provided below the throat portion 221.

By the operation of the pump 40, the lubricating oil in the tank 10 is supplied to the inner cylinder 21 of the venturi nozzle 20 via the pipe 30. The oil droplet dropped from the inner cylinder nozzle 21 is converted into a mist in the throat portion 221,
The gas is discharged from the diffusion chamber 222 into the upper space of the tank 10 and sent from the tank chamber to a refueling point via a predetermined pipe 11. The large mist is returned into the tank 10 through a discharge hole formed in the bottom surface of the diffusion chamber 222.

The mist lubricating apparatus includes a sensor 50 for detecting a flow (flow rate) of the lubricating oil in the pipe 30 and an abnormality detecting means for detecting a reverse flow based on an output signal of the sensor 50 to generate an abnormal signal. 60 are provided. In this example, the sensor 50 is composed of a thermistor and is inserted into a pipe between the discharge side check valve 32 and the venturi nozzle 20.

That is, as shown in FIG. 2, the sensor 50 is located in the flow of the lubricating oil in the pipe 30. An output circuit 51 is connected to the sensor 50. Although not shown, the output circuit 51 includes a sensor 50.
A constant current circuit that supplies a constant current to the power supply, a capacitor that integrates the current required for self-heating of the thermistor, and the like are provided, and an output voltage signal is transmitted from the capacitor.
The output voltage signal is proportional to the lubricating oil flow rate as described above.

Referring to FIG. 2, the abnormality detecting means 60 operates the pump 40 intermittently so as to generate a pump operation interval pulse (see FIG. 3A). A generation circuit) 61 and a pump operation time adjustment circuit (second pulse generation circuit) 62 that supplies a discharge operation time pulse (see FIG. 3C) to the pump 40 every time the operation interval pulse is issued. Have.

In this example, since the pump 40 is a piston type pump that repeats suction and discharge, no flow occurs in the pipe 30 beyond the discharge side check valve 32 during the suction operation, and only during the discharge operation. Occurs. The discharge operation time pulse set by the pump operation time adjustment circuit 62 is this discharge operation time, and the suction operation time is allocated to other times.

A signal inverting circuit (third pulse generating circuit) 63 for outputting an inverted pulse thereof (see FIG. 3D) in synchronization with the discharge operating time pulse is provided at an output stage of the pump operating time adjusting circuit 62. Is connected.

The output circuit 51 of the sensor 50 has a comparison circuit 6 for generating an output pulse (see FIGS. 3E and 3F) when the output voltage signal exceeds a predetermined threshold level.
The output of the comparison circuit 64 and the output of the signal inversion circuit 63 are supplied to a two-input AND circuit 65.

An abnormal signal from the AND circuit 65 (FIG. 3)
(See (g)). According to this example, the AND circuit 65 is connected to the abnormal signal counting circuit 66 for counting the abnormal signal. In this example, the abnormal signal is counted twice. Then, an abnormal signal is sent from the abnormal signal counting circuit 66 to a lubrication system control means (not shown).

The abnormality detecting means 60 includes an operation number counting circuit 67 for counting the operation interval pulse generated from the pump operation interval setting circuit 61, and a count value of the operation number counting circuit 67 which is a predetermined reference number. And a reset circuit 68 that outputs a reset signal (see FIG. 3B) to the number-of-operations counting circuit 67 and the abnormal signal counting circuit 66 when the number of times has reached. In this example,
The reference number set in the reset circuit 68 is five.

Next, the backflow detecting operation by the abnormality detecting means 60 will be described with reference to the timing chart of FIG. First, a regular operation interval pulse A is emitted from the pump operation interval setting circuit 61 as an operation basic clock as shown in FIG.

At the same time as the rise of the first (first) operation interval pulse A, the reset circuit 68 instructs the operation number counting circuit 67 and the abnormal signal counting circuit 66 to operate as shown in FIG.
As shown in (b), a reset signal B is issued, and both circuits are cleared.

At each rising time of the operation interval pulse A, the pump operation time adjusting circuit 62 outputs the discharge operation time pulse C as shown in FIG. 3C, and the signal inversion circuit 63 outputs the discharge operation time pulse C as shown in FIG. ), An inverted pulse D is output. This inversion pulse D is a discharge operation time pulse C
Is "0" when is "1", and becomes "1" when the ejection operation time pulse C is "0".

The discharge operation of the pump 40 causes a flow of lubricating oil in the pipe 30. Therefore, an output voltage signal E synchronized with the ejection operation time pulse C is output from the output circuit 51 of the sensor 50 as shown in FIG. The output voltage signal E is input to the comparison circuit 64, and is compared with a predetermined threshold level R (a chain line level in FIG. 3E) set in advance.

Since the threshold level R is set to a value that does not pick up fine noise-like pulsation of the lubricating oil in the pipe 30, the output voltage signal E that appears with the discharge operation of the pump 40 is Well above the threshold level R. Therefore, the output pulse F synchronized with the ejection operation time pulse C is output from the comparison circuit 64 as shown in FIG.

The output pulse F from the comparison circuit 64 is:
The inversion pulse D from the signal inversion circuit 63 and the AND circuit 6
5, the output pulse F and the inversion pulse D are in an inversion relationship, so that the logical output is "0" and no abnormal signal is output from the AND circuit 65.

Here, assuming that a reverse flow occurs when the discharge of the pump 40 is stopped (when the pump including the suction cycle is stopped) due to a functional failure (valve failure) of the discharge side check valve 32, the output circuit 51 of the sensor 50 outputs An output voltage signal e corresponding to the reverse flow is output.

If the output voltage signal e is large exceeding the threshold level R, the output pulse f
And the output pulse f is applied to one input terminal of the AND circuit 65. At this time, the signal inversion circuit 63
Since the inverted pulse D applied to the other input terminal of the AND circuit 65 is in the state of "1", the abnormal signal G is output from the AND circuit 65 as shown in FIG. .

The abnormal signal G is counted by an abnormal signal counting circuit 66 at the next stage. In this example, when the abnormal signal G is counted twice by the abnormal signal counting circuit 66 in consideration of the possibility of one-time backflow due to an accidental factor, the lubrication system control means (not shown) is abnormal. A signal indicating the presence is output.

In parallel with this, the operation interval pulse A is counted by the operation number counting circuit 67, and when the count value reaches five, at the rising point of the sixth operation interval pulse A to be output next. Then, a reset signal B is output from the reset circuit 68 to the operation number counting circuit 67 and the abnormal signal counting circuit 66 to return to the initial state. Thereafter, this is repeated.

By providing the sensor 50 between the suction-side check valve 31 and the discharge-side check valve 32, it is possible to detect a backflow due to a failure of the suction-side check valve 31. That is, the sensor 50 is connected to the pipe 30
Where to put in is a matter that can be appropriately selected.

In the above embodiment, since the piston type pump 40 is used, two check valves 31 and 32 are inserted in the pipe 30. However, when a continuous supply type pump such as a gear pump is used, the check valve is used. A single valve may be used, in which case the gear pump may be connected either upstream or downstream of the check valve.

Further, in the above embodiment, the AND circuit 65
Thus, the output voltage signal of the sensor obtained at the time of pump discharge operation and the output voltage signal of the sensor obtained at the time of reverse flow are determined, but the present invention is not limited to this.

For example, the signal inverting circuit 63 and the comparing circuit 64
The logic circuit can be changed depending on the pulse form of the pulse of the above. In short, if the logic circuit can determine the sensor output voltage signal at the time of pump discharge operation and at the time of backflow,
An equivalent technique is included in the present invention. Further, in the embodiment, a negative characteristic thermistor is used for the sensor 50, but a positive characteristic thermistor may be used.

[0042]

As described above, according to the present invention,
In a fluid circuit which is guided from a fluid storage tank to a predetermined fluid supply point and has at least one check valve provided in the predetermined portion, and a fluid circuit including a pump connected to the same pipe, a fluid is provided in the pipe. A sensor consisting of an electric resistance element whose resistance changes when heat is taken away is provided, and the sensor output is monitored by abnormality detection means. If the sensor output appears during the pump stop period, an abnormality is detected. By generating a signal, a backflow due to a check valve failure can be reliably detected.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a mist lubrication device to which the present invention is applied.

FIG. 2 is an electrical block diagram showing an example of an abnormality detection unit according to the present invention.

FIG. 3 is a timing chart for explaining the operation of the abnormality detecting means.

FIG. 4 is an explanatory diagram for pointing out a problem of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lubricating oil storage tank 20 Venturi nozzle 21 Inner cylinder nozzle 22 Outer cylinder nozzle 221 Throat part 222 Diffusion chamber 30 Piping 31, 32 Check valve 40 Pump 50 Sensor (thermistor) 51 Output circuit 60 Abnormality detection means 61 Pump operation interval setting circuit 62 Pump operation time adjustment circuit 63 Signal inversion circuit 64 Comparison circuit 65 AND circuit 66 Abnormal signal counting circuit 67 Number of operation count circuit 68 Reset circuit

Claims (5)

[Claims] 1. A fluid circuit, comprising: a pipe that is guided from a fluid storage tank to a predetermined fluid supply location and has at least one check valve provided at the predetermined location, and a pump connected to the pipe. A backflow detecting device for detecting a backflow during a pump stop period, wherein a sensor comprising an electric resistance element which is inserted into the pipe and whose resistance value changes due to heat being removed by a fluid, and an output signal of the sensor are monitored. And a failure detection means for outputting a failure signal when the output signal appears during the pump stop period. A first pulse generating circuit for generating an operation interval pulse of the pump; and a second pulse generating circuit for receiving the operation interval pulse and providing a discharge operation time pulse to the pump. A third pulse generation circuit that outputs an inverted pulse thereof in synchronization with the ejection operation time pulse, a comparison circuit that generates an output pulse when the output signal of the sensor exceeds a predetermined threshold level,
2. The backflow detecting device for a fluid circuit according to claim 1, further comprising: an AND circuit that outputs a logical product of the inverted pulse and the output pulse to output an abnormal signal. 3. An output stage of the AND circuit is connected to a first counting circuit for counting the number of occurrences of the abnormal signal, and the number of occurrences exceeds a first reference count value set in advance. The backflow detecting device for a fluid circuit according to claim 2, wherein an abnormal signal is generated at a point in time. 4. A second counting circuit for counting the operation interval pulse, and when the count value of the second counting circuit reaches a second reference count value set in advance, the first and second count circuits.
4. The backflow detecting device for a fluid circuit according to claim 3, further comprising: a reset circuit for applying a reset pulse for clearing each of the count values to the count circuit. 5. A pipe which is led from a lubricating oil storage tank to a venturi nozzle and has a pipe provided with at least one check valve at a predetermined portion thereof, and a pump is connected to the pipe. In a mist lubrication device that pumps up the lubricating oil inside and supplies it to the Venturi nozzle, and supplies the mist lubricating oil to a predetermined lubrication point, the lubricating oil is inserted into the piping and heat is taken by the fluid. A sensor comprising an electric resistance element whose resistance value changes by being monitored, and abnormality detection means for monitoring an output signal of the sensor and outputting an abnormality signal when the output signal appears within the stop period of the pump. A mist lubrication device comprising: