JP3101534B2 - Flow meter rotation detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation detecting device for a flow meter provided with a gear rotor used for measuring a high-viscosity liquid such as a polymer resin liquid or a paint.

[0002]

2. Description of the Related Art Conventionally, as a flow meter for measuring a high-viscosity liquid, a positive displacement flow meter having two gear rotors has been devised in view of demands for high pressure of the liquid to be measured and high responsiveness. The flow meter has a main body that rotatably guides two gear rotors in the measuring chamber and a lid that closes the measuring chamber,
The liquid to be measured flowing from the inlet is discharged to the outlet with the volume surrounded by two adjacent teeth of the gear rotor and the inner wall of the measuring chamber as a unit volume.
The flow meter is provided with a rotation detecting device for counting the number of rotations of the gear rotor and measuring the flow rate. As the rotation detecting device, a magnet is embedded in the gear rotor and the rotation of the magnet is controlled by a reed switch. A device for detecting the flow rate of the liquid to be measured from the number of rotations by using a magnetic detection element or a magnetoresistive element, etc., is widely used.

[0003]

In this type of rotation detecting device, it is necessary to count the number of rotations of the gear rotor when measuring the liquid to be measured. However, even if the diameter of the gear rotor is increased, the size of each tooth is large. Since the size of the magnet cannot be increased so much, the magnet cannot be embedded in each tooth portion, and the number of magnets has to be reduced only by mounting magnets at several places of the gear rotor. Therefore, it is not possible to output a detection signal corresponding to the rotation of each tooth portion of the gear rotor, and although the gear rotor is used, not only the high-speed response cannot be improved so much, but also the resolution of the detection signal is hindered. And other drawbacks.

SUMMARY OF THE INVENTION The present invention has been made for the purpose of eliminating the above-mentioned drawbacks, and aims to provide a rotation detecting device for detecting the passage of each tooth of a gear rotor without embedding a magnet in each tooth of the gear rotor. It is.

[0005]

In the measuring chamber of the main body of the flow meter, two gear rotors are arranged so as to mesh with each other and rotate freely. With the rotation of the gear rotor, two gear teeth adjacent to each other and the measuring chamber of the measuring chamber are rotated. The liquid to be measured is discharged from the inlet side to the outlet side for each volume formed by the inner wall, and the flow rate of the liquid to be measured is measured from the rotation speed of the gear rotor.

At least a part of the teeth of the gear rotor is made of a magnetic material, and two magnets are arranged at a fixed distance from the movement path of the teeth of the gear rotor. Between the magnets and between the magnet and the gear rotor, a first detecting resistor that changes the resistance value for a magnetic field in a certain direction and does not change the resistance value for a magnetic field in a direction crossing the magnet. And a second detection resistor that changes the resistance value of the magnetic field in the direction that does not change the resistance value with respect to the magnetic field in the fixed direction but changes the resistance value with respect to the magnetic field in the direction that crosses the fixed direction. Further, a difference between the voltage applied to the first detection resistor and the voltage applied to the second detection resistor is extracted as an output signal of the magnetoresistive element, and from this output signal, the passage of the teeth of the gear rotor is detected. Is configured.

[0007]

In the above flowmeter, when the liquid to be measured flows into the measuring chamber, two gear rotors rotate according to the flow rate. As the gear rotor rotates, its teeth pass near the magnetoresistive element. During this time, since the teeth are made of a magnetic material, when two adjacent teeth are positioned to sandwich the two magnets, the lines of magnetic force from both magnets pass through the magnetoresistive element, and the first The resistance values of the detection resistor and the second detection resistor are each reduced equally, the equilibrium state is maintained, and there is no difference in the voltage generated between them, and they become zero. When one of the teeth of the gear rotor is rotated so as to reach the direction in which one of the magnets extends, the lines of magnetic force from the two magnets converge on the teeth of the gear rotor. Moreover,
The direction of the line of magnetic force, that is, the direction of the magnetic field and its strength change with the movement of the teeth, and when the direction of the magnetic field from the other magnet matches the direction of maximum sensitivity of the magnetoresistive element, the first detection resistor and the The voltage generated at each of the two detection resistors, that is, the output voltage of the magnetoresistive element changes to the maximum.

Thereafter, when the teeth further rotate and rotate toward the position closest to the magnetoresistive element, the magnetic field from the two magnets is applied to the magnetoresistive element, but the output voltage of the magnetoresistive element is reduced. The change gradually decreases, and when the tooth reaches the position closest to the magnetoresistive element, the output voltage of the magnetoresistive element does not change and becomes zero.

When the tooth portion further rotates so as to reach the direction in which the other magnet extends, the polarity of the tooth portion is reversed from that in the case where the tooth portion rotates toward the above-mentioned magnet, and the directions of the magnetic fields from the two magnets and their strengths are reversed. When the magnetic field from one magnet coincides with the direction of maximum sensitivity of the magnetoresistive element, the output voltage of the magnetoresistive element changes to the maximum. As the tooth further rotates, the tooth reaches a position sandwiching the two magnets together with the following tooth, and the output voltage of the magnetoresistive element returns to zero.

Therefore, a passage detection signal of each tooth portion of the gear rotor is obtained from the output voltage of the magnetoresistive element, which is counted, and the flow rate of the liquid to be measured is accurately measured from the counted value.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3, reference numeral 1 denotes a flow meter, and two gear rotors 3 mesh with each other and rotate about a rotor shaft 4 in a measuring chamber 2 c of a main body 2 having an inlet 2 a and an outlet 2 b. It is configured to be. The rotor shaft 4 is implanted in the main body 2, and an upper portion thereof is configured to be held by a lid 5 that closes the measuring chamber 2 c.

The gear rotor 3 has teeth 3a extending on its outer circumference and over the entire length thereof, and the teeth 3a rotate close to the inner wall of the measuring chamber 2c of the main body 2, and rotate. The liquid to be measured flowing from the inlet 2a is discharged to the outlet 2b side for each volume formed by the two teeth 3a and the inner wall of the measuring chamber 2c. The gear rotor 3 has at least a tooth portion 3a made of a magnetic material. When the tooth portion 3a passes near a magnetoresistive element 6 described later, a first magnet 7 described later on the tooth portion 3a is formed.
The magnetic field lines from the second magnet 8 converge and the direction and strength of the magnetic field around the magnetoresistive element 6 change.

On the other hand, the lid 5 is made of a non-magnetic material, and is configured so that lines of magnetic force from the first magnet 7 and the second magnet 8 can converge on the teeth 3a. The lid 5 is provided with a sensor storage hole 5a. The sensor storage hole 5a is separated from the moving path of the tooth portion 3a by a fixed distance via a mounting plate 9a of the rotation detecting device 9 and is fixed at a certain distance from each other. The first magnet 7 and the second magnet 8 are disposed apart from each other. Moreover, the poles of the magnets 7, 8 are arranged so as to face in the same direction, and the distance between the magnets 7, 8 is shorter than the distance between two adjacent teeth 3a of the gear rotor 3. .

The mounting plate 9a is located at an intermediate position between the first magnet 7 and the second magnet 8 and between the magnets 7, 8 and the gear rotor 3.
The magneto-resistive elements 6 are arranged so that the magneto-resistive elements 6 can detect a change in the direction of a magnetic field formed by lines of magnetic force from the first magnet 7 and the second magnet 8 and a change in the strength of the magnetic field. Is configured. The magnetoresistive element 6 has a first detection resistor 6a and a second detection resistor 6b which are connected in series as shown in FIG. The first detection resistor 6a
Is hardly changed by the magnetic field from the first magnet 7 toward the tooth 3a when the tooth 3a of the gear rotor 3 is positioned in the direction in which the first magnet 7 extends, and the magnetic field in the direction crossing the tooth 3a It is configured to change. Further, the resistance value of the second detection resistor 6b changes due to the magnetic field from the second magnet 8 toward the tooth portion 3a when the tooth portion 3a of the gear rotor 3 is located in the direction in which the second magnet 8 extends, and intersects with this. It is configured so that it hardly changes depending on the magnetic field in the direction.

The output voltage of the magnetoresistive element 6 is the difference between the voltage generated at the first detection resistor 6a and the voltage generated at the second detection resistor, and the teeth 3a extend the first magnet 7. The maximum sensitivity when the magnetic field from the first magnet is in a direction in which the magnetic field from the first magnet reduces the resistance value of the first detection resistor of the magnetoresistive element to a maximum and the direction of the magnetic field from the second magnet intersects at approximately 45 degrees. When in the direction, the output voltage is configured to be maximum. Also,
When the tooth portion 3a is positioned in the direction in which the second magnet 8 extends, that is, when the magnetic field from the second magnet decreases the resistance value of the second detection resistor of the magnetoresistive element to the maximum, When the direction of the magnetic field from one magnet is the maximum sensitivity direction crossing at approximately 45 degrees, the output voltage is configured to have the maximum value in the (-) direction, that is, the minimum. Further, the output voltage of the magnetoresistive element 6 is not only when the teeth 3a reach an intermediate position between the first magnet 7 and the second magnet 8, but also two adjacent teeth 3a sandwich the magnets 7,8. In such a configuration, the resistance values of the first detection resistor and the second detection resistor are reduced equally, so that there is no difference between the voltages generated in the respective detection resistors, and these are maintained in a balanced state. Have been. In addition, two magnetic resistance elements 6 are provided, and two first detection resistances 6a and two second detection resistances 6 are provided.
b, a bridge circuit may be formed so that the output voltage of the magnetoresistive element 6 is extracted by a differential amplifier (not shown) or the like.

The output voltage of the magnetoresistive element 6 is sent to a pulse generator (not shown), and a pulse signal is output from the pulse generator. The pulse signal is counted by a counter (not shown). The flow rate of the liquid to be measured according to the numerical value is calculated.

In the flow meter described above, when the liquid to be measured flows into the measuring chamber 2c from the inflow port 2a, the gear rotor 3 starts to rotate, and accordingly, the two adjacent teeth 3a and the measuring chamber 2c are rotated.
The measured liquid flows out of the outlet 2 for each volume formed by the inner wall of
It is discharged to the b side. With the rotation of the gear rotor 3, the teeth 3a pass near the magnetoresistive element 6, but since the teeth 3a of the gear rotor 3 are made of a magnetic material, they are adjacent as shown in FIG. When the tooth portion 3a is at the position sandwiching the magnetoresistive element 6, the lines of magnetic force from the first magnet 7 and the second magnet 8 converge on the nearby tooth portions 3a and 3b, respectively, and a magnetic field in that direction is generated. At this time, a part of the lines of magnetic force from the magnets 7 and 8 pass above the magnetic detection element 6, but the magnetic field formed by the magnetic field is weak, and the first detection resistance and the second detection resistance of the magnetic detection element respectively. Does not change, and the difference, that is, the output voltage becomes zero. From this state, one of the adjacent tooth portions 3a moves to rotate in the direction in which the first magnet 7 extends, while the other tooth portion 3b moves to the second magnet 8
From the second magnet 8, the line of magnetic force from the second magnet 8 converges on the approaching tooth portion 3a, the direction of the magnetic field from the second magnet 8 changes, and the magnetic field on the magnetoresistive element 6 also increases. Further, as shown in FIG.
a reaches the direction in which the first magnet 7 extends, that is, the direction of the magnetic field of the first magnet does not change the resistance value of the first detection resistor 6a, and the direction of the magnetic field from the second magnet 8 changes in the direction of the second detection resistor. The output voltage of the magnetoresistive element 6 becomes maximum when the resistance value of the resistor 6b is in the maximum sensitivity direction.

When the tooth portion 3a further rotates toward the intermediate position between the magnets 7 and 8, the direction of the magnetic field changes as shown in FIG. Become equal. Accordingly, the resistance values of the first detection resistor 6a and the second detection resistor 6b of the magnetoresistive element 6 become equal, and the output voltage of the magnetoresistive element 6, which is the difference between the voltages generated at the respective detection resistors 6a and 6b, becomes It gradually decreases from the maximum value, reaches an equilibrium state, and becomes zero.

From this state, as shown in FIG. 5 (d), when the tooth portion 3a further rotates in the direction in which the second magnet 8 extends, the direction of the magnetic field also changes with this. The resistance value of the second detection resistor 6b does not change due to the magnetic field from the second magnet 8, and when the direction of the oblique magnetic field from the first magnet 7 reaches the maximum sensitivity direction, the output voltage of the magnetoresistive element 6 becomes It becomes the maximum in the (-) direction, that is, the minimum.

Further, when the tooth portion 3a rotates in a direction to reach a position sandwiching the magnetoresistive element 6 together with a subsequent tooth portion (not shown), the magnetoresistive element 6 is in the aforementioned weak magnetic field state and the first detection. The resistance values of the resistor 6a and the second detection resistor 6b are reduced equally, and the output voltage of the magnetoresistive element 6 returns to zero. Accordingly, the magnetoresistive element 6 can output the output voltage shown in FIG. 6 while one tooth passes.

The output voltage is sent to a pulse generator.
The pulse generator outputs a pulse signal, which is counted by the counter as a tooth passage detection signal. Therefore, the flow rate of the liquid to be measured according to the count value is calculated, and the flow rate of the liquid to be measured is measured. Note that the output voltage of the magnetoresistive element 6 may be sent to a full-wave rectifier (not shown) so that two pulse signals are transmitted while one tooth 3a of the gear motor 3 passes.

[0022]

As described above, according to the present invention, at least a part of the teeth of the gear rotor is made of a magnetic material.
Two magnets are arranged at a fixed distance from the movement path of the tooth portion of the gear rotor, a magnetoresistive element is arranged at an intermediate position between these magnets and between the magnet and the gear rotor, and an output signal of the magnetoresistive element is used. Since the configuration is such that the flow of the liquid to be measured is measured by detecting the passage of the teeth of the gear rotor, the passage of the teeth can be detected regardless of the size of the teeth of the gear rotor. And a highly responsive rotation detection device suitable for a vehicle. Further, according to the present invention, two pulse signals can be output as one tooth passes, rotation detection with high resolution can be performed, and extremely accurate measurement of the liquid to be measured can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a main part of a flow meter according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged sectional view of a main part along line BB of FIG. 1;

FIG. 4 is an explanatory diagram of a magnetoresistive element according to the present invention.

5 (a), 5 (b), 5 (c), 5 (d) are explanatory diagrams illustrating the operation of the present invention.

FIG. 6 is a waveform diagram of an output voltage of the magnetoresistive element according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow meter 2, Main body 2a Inflow port 2b Outflow port 2c Metering chamber 3 Gear rotor 3a, 3b Teeth part 4 Rotor shaft 5 Cover part 5a Sensor accommodation hole 6, Magnetic resistance element 6a First detection resistor 6b Second detection resistor 7 First Magnet 8 Second magnet 9 Rotation detector 9a Mounting plate

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 3/10 G01D 5/245 G01D 5/245 102 G01P 3/488

Claims (1)

(57) [Claims] The present invention comprises two gear rotors rotatably arranged in mesh with each other in a measuring chamber of a main body, and each of two volumes formed by two adjacent tooth portions and an inner wall of the measuring chamber as the gear rotor rotates. In a flowmeter configured to discharge the liquid to be measured from the inlet side to the outlet side to detect the flow rate of the liquid to be measured from the rotation speed of the gear rotor, at least a part of the teeth of the gear rotor is made of a magnetic material. At the same time, two magnets are arranged at a fixed distance from the movement path of the tooth portion of the gear rotor, and a resistance value is set between the magnet and the gear rotor at a middle position between the magnets and a magnetic field in a fixed direction. The first detection resistor which does not change the resistance value with respect to the magnetic field in the direction intersecting with the first detection resistor and the magnetic field in the direction intersecting with the magnetic field in the fixed direction without changing the resistance value. A magnetoresistive element having a second detection resistor for changing a resistance value is disposed in the field, and a difference between a voltage applied to the first detection resistor and a voltage applied to the second detection resistor is determined by an output signal of the magnetoresistive element. A rotation detection device for detecting passage of a tooth portion of the gear rotor from the output signal.