JPH07145795A - Centrifugal blower with flow sensor and its drive device - Google Patents

Abstract

PURPOSE:To provide a centrifugal type ventilator which ventilates on the basis of an outside signal a discharge flow that is required that the precision improvement of the discharge flow may be able to be realized even against the effect of load change and change with the lapse of time in a centrifugal blower. CONSTITUTION:A centrifugal blower with a flow sensor and its drive device are a centrifugal ventilator consisting of a DC motor 2; a centrifugal fan 1; and a scroll type casing 6 having a suction opening 4 and a discharge opening 5, and by joining to the suction opening 4 of the scroll type casing 6 a sensor fitting pipe 14 made up by having a flow sensor 13 screw-fixed at its approximate center portion and at the same time fitting an air filter 12 to the atmosphere side end portion of the sensor fitting pipe 14, the discharge flow of the ventilator can be detected on the ventilator suction side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal blower and its drive unit, and by accurately detecting the discharge flow rate of the blower, in particular, it is connected to the discharge side of the blower due to unstable discharge flow rate of the blower. This is to prevent malfunction or failure of the combustion equipment, etc.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. Generally, the discharge pressure-discharge flow rate characteristic of a blower is shown in FIG.
In the case of the one-stage centrifugal blower, the curve becomes a downward-sloping gentle curve as shown by the characteristic curve A, and the characteristic curve A and the pressure loss characteristic of the upward-sloping load shown by the dotted line in the figure are The intersection H determines the discharge flow rate of the blower. However, in the case of the above-described one-stage centrifugal blower, the characteristic curve is gentle, so that the flow rate fluctuation is large even with a slight pressure fluctuation on the load side. Therefore, in order to reduce the flow rate fluctuation with respect to the pressure fluctuation, the conventional centrifugal blower uses a high-pressure type fan in which the discharge pressure is increased as shown by the characteristic curve B. As means for increasing the discharge pressure, a centrifugal blower is a two-stage type, a three-stage type, a four-stage type.
・ ・ By dealing with multiple stages Further, the optimum flow rate required by the combustion device connected to the blower was open-loop controlled by a drive voltage satisfying the required flow rate by experimentally determining the relationship between the drive voltage of the blower and the discharge flow rate.

FIG. 6 is a half sectional view of a conventional two-stage centrifugal blower composed of two centrifugal fans. As shown in this figure, the centrifugal blower includes a lower casing 6a having a DC motor 2, a motor base 3, and a discharge port 5, an upper casing 6b having a suction port 9, and upper and lower centrifugal fans 1.
b, 1a. In addition, 7 is a shaft of a DC motor for attaching the upper and lower centrifugal fans 1b and 1a, and 8 is the upper and lower casings 6 described above.
It is a return guide provided between b and 6a. Also,
10 is a plain washer and 11 is a snap ring. In such a conventional blower, when a drive voltage is applied to the DC motor 2, the upper centrifugal fan 1b is rotated to rotate the suction port 9 above.
More air is sucked in, and the air compressed here is efficiently sent to the lower casing 6a by the return guide 8 and further discharged by the lower centrifugal fan 1a in the outer peripheral portion of the lower casing 6a. It is ejected from 5.

[0004]

As described above, in the two-stage centrifugal blower, the consumption current increases due to an increase in the load of the DC motor, the weight increases due to the rigidity of the shaft of the motor, and the vertical axis of the shaft of the DC motor is increased. There are major problems such as an increase in processing cost and an increase in the number of parts due to the high precision required every time.

Further, by changing the centrifugal blower to the two-stage type, although the flow rate fluctuation is reduced with respect to the pressure fluctuation, the centrifugal blower is not limited to the one-stage type and the two-stage type, but is open loop control. Therefore, the discharge flow rate will naturally vary due to variations in the load on the blower side and the equipment connected to it.In addition, the discharge flow rate will increase due to the increase in the DC motor speed during operation, and the discharge flow rate will change over time. It is not suitable when the discharge flow rate accuracy is required for a long period of time. With respect to such problems, the present invention provides a centrifugal blower that blows a discharge flow rate based on an external signal so as to improve the accuracy of the discharge flow rate even with respect to the influence of load fluctuations and changes over time. The purpose is to provide a blower.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a scroll type casing 6 of a single-stage centrifugal blower instead of a two-stage type, a three-stage type, or a multi-stage type. By providing the flow rate sensor 13 on the suction port 4 side,
The flow rate that the blower is actually discharging is measured by the flow rate sensor 13
Is detected, the difference from the target discharge flow rate is compared and calculated, and so-called feedback control is performed to control the drive pulse duty ratio of the blower so that the target discharge flow rate is achieved.

Then, the flow rate sensor 13 of the present invention described above.
Is mounted such that the position of the flow rate detecting sensor element 13a is offset by d [mm] from the center of the sensor mounting pipe 14, and the joint between the sensor mounting pipe 14 and the suction port 4 of the scroll type casing 6 is about 15 mm. By joining with a reduction taper of °, the rectifying grid, which is conventionally required in general, is not placed between the air filter 12 and the flow sensor 13, and the air flow is made into a laminar flow state, and the output signal of the flow sensor is It is characterized by stability.

That is, the structure of the centrifugal blower with a flow sensor of the present invention is the centrifugal blower comprising a DC motor 2, a centrifugal fan 1, and a scroll type casing 6 having a suction port 4 and a discharge port 5. To the suction port 4 of the scroll type casing 6, a sensor mounting pipe 14 having a flow rate sensor 13 provided at a substantially central portion is joined, and an air filter 12 is attached to an end of the sensor mounting pipe 14 on the atmosphere side. Is detected on the suction side of the blower.

Further, the drive device for a centrifugal fan with a flow sensor according to the present invention comprises a flow rate detecting means A by a flow rate sensor 13 provided on a suction port side of a scroll type casing 6 of the centrifugal blower, an operation of the blower and a required flow rate. A target discharge flow rate calculating means C for calculating a target discharge flow rate from a blower request signal B composed of an instruction signal, and a drive pulse duty ratio calculating means D for calculating a pulse duty ratio when driving the blower.
The blower driving means E for driving the blower with the pulse duty ratio drives the DC motor 2 of the centrifugal blower.

[0010]

According to the present invention, by detecting the discharge flow rate of the blower on the casing suction side, the actual discharge flow rate and the target flow rate are compared and calculated by the microcomputer, and the drive pulse duty ratio for the DC motor 2 of the blower is determined. Since the feedback is provided, the discharge flow rate of the blower becomes stable, and the equipment connected thereto can be prevented from being damaged. Also,
By forming the sensor mounting pipe 14 to have an inner surface shape in which the straight diameter is reduced and tapered, the flow of air can be made into a laminar flow state and the output signal of the flow rate sensor 13 can be stabilized, and the suction efficiency of the centrifugal blower can be improved. This can be made almost the same as the case where the conventional sensor mounting pipe 14 is not connected.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a centrifugal fan device with a flow sensor according to the present invention. The centrifugal blower is a one-stage centrifugal blower as shown in FIG. 2, and the centrifugal blower has a DC motor 2 having a centrifugal fan 1, a motor base 3, a discharge port 5 and a suction port as in the conventional product. And a casing 6 having 4. Further, 7 is a shaft of a DC motor for mounting the centrifugal fan 1. Also, 10
Is a plain washer, and 11 is a snap ring.

The sensor mounting pipe 14 of the present invention is mounted on the suction port side of a blower. An air filter 12 is mounted on the suction port opening end of the blower and the suction port 4 side of the casing 6 is tapered. (About 15), the flow of air becomes a laminar flow without providing a special rectifying grid between the air filter 12 and a flow sensor 13 described later. The flow rate sensor 13 is the sensor mounting tube 1
4 is attached to almost the center of the flow sensor 4. The flow rate sensor 13 includes a flow rate detecting sensor 13a and an air temperature sensor 13.
b is a hot-wire type flow sensor, which constitutes a bridge circuit with the HIC 25.

Next, the drive device of the centrifugal blower of the present invention will be described in detail with reference to FIGS. 1 and 2. The drive device of the present invention comprises a centrifugal blower, an electronic control unit 15, and a blower request signal B. The digital computers that are part of the electronic control unit 15 are ROMs that are interconnected by a bidirectional bus 28.
(Read-only memory) 16, RAM (write-only memory) 17, CPU (central information processing unit) 18, input port 19 and output port 20 are configured.

FIG. 1 is a block diagram showing a connected state of each part of a drive unit of a centrifugal blower, and A shown in this figure is a flow rate provided on a suction side of a scroll type casing 6 of the centrifugal blower shown in FIG. The flow rate sensor 1 is a flow rate detection unit including a sensor 13 and a HIC 25 forming a bridge circuit.
3 and the sensor output signal converted by HIC25 is A
It is output to the D converter 26 and stored in the RAM 17 from the input port 19 via the bidirectional bus 28. On the other hand, RO
M16 stores the sensor output signal and the discharge flow rate data as shown in FIG. 5 based on the result obtained by the experiment in advance, and stores the actual measured value stored in the RAM 17 and the ROM 16 in the ROM 16. The discharge flow rate is detected by the CPU 18 comparing and calculating the measured value.

FIG. 1B is a blower request signal composed of the blower operation instruction signal 21 and the target discharge flow rate signal 22 shown in FIG. 2, and the blower request signal B is inputted via the AD converters 23 and 24, respectively. Connected to port 19. In addition,
The blower operation instruction signal 21 is a Hi or Lo signal indicating whether or not the centrifugal blower is operated, and
As the target discharge flow rate instruction signal 22, the target discharge flow rate value (for example, 0 to 150 l / min) is converted into a voltage signal (for example, 0 to 5).
V).

FIG. 1C shows a target for calculating the ON / OFF of the operation and the target discharge flow rate from the voltage level of the blower request signal B (both the blower operation instruction signal 21 and the target discharge flow rate signal 22 shown in FIG. 2). It is a discharge flow rate calculating means, and stores the output states of the blower operation instruction signal 21 and the target discharge flow rate signal 22 in the RAM 17, while in the ROM 16,
The above-described relationship between the discharge flow rate instruction signal (for example, 0 to 5 V) and the target discharge flow rate (for example, 0 to 150 l / h) is stored in advance, and the CPU 18 compares the values of the ROM 16 and the RAM 17 to determine the operation. ON, OFF, and target discharge flow rate are calculated.

1D is a pulse duty ratio calculating means for driving the blower by the flow rate detecting means A and the target discharge flow rate calculating means C, and the CPU 18 shown in FIG. The pulse duty ratio for driving the blower is calculated from the relationship between the discharge flow rate and the drive pulse duty ratio shown in FIG. 4, which is experimentally obtained in advance for the device connected to the centrifugal blower stored in the ROM 16. Further, according to the result obtained by the CPU 18 of the deviation between the discharge flow rate when the blower is actually driven by the flow rate detection means A and the target discharge flow rate calculation means C,
The so-called feedback control is also performed, which also corrects the drive pulse duty ratio.

In FIG. 1E, the pulse duty signal calculated by the drive pulse duty ratio calculating means D is stored in the CPU.
8 is an output port, and DRIVE 27 is a blower drive means for driving a centrifugal blower with the pulse duty ratio signal.

Next, the operation of the electronic control unit 15 will be described with reference to FIG.
It will be specifically described with reference to the flowchart shown in FIG. First, at step 29, the arithmetic processing is started according to the program stored in the ROM 16. Next, the routine proceeds to step 30 to check the input states of the blower operation instruction signal 21 and the target discharge flow rate instruction signal 22 which are the blower request signals B input to the electronic control unit 15 from the outside. Then, the routine proceeds to step 31 and determines whether or not to drive the centrifugal blower. Here, the centrifugal blower is operated only when both the blower operation instruction signal 21 and the target discharge instruction signal 22 are in the input state A
It is an ND circuit. If YES is determined to operate the centrifugal blower, the routine proceeds to the next step 32.
Proceed to. If it is determined NO in step 31, that is, if the centrifugal blower is not operated, the routine proceeds to step 30.
Return to.

Next, at step 32, it is judged whether or not the operation instruction of the centrifugal blower is the first signal. If it is determined here that this is the first operation instruction, the routine proceeds to the next Step 33. Subsequently, in step 33, the drive pulse duty ratio of the centrifugal blower that satisfies the target discharge flow rate is calculated. Here, regarding the relationship between the discharge flow rate and the drive pulse duty ratio for the device connected to the centrifugal blower, the data of FIG. 4 obtained in advance by experiment is stored in the ROM 16.

Next, in step 34, the DRI is calculated with the drive pulse duty ratio obtained in step 33.
The centrifugal blower is driven through the VE 27. continue,
The routine proceeds to step 35. Here, the discharge flow rate driven by the centrifugal blower is measured by the hot wire flow sensor 13 and the HI.
Although it is detected by C25, it usually takes 2 to 3 seconds to stabilize the discharge flow rate of the centrifugal blower, and the response of the heat wire type flow sensor is about 1
Since it is second, to detect the flow sensor output signal,
It is necessary to consider these times. The relationship between the output signal of the flow rate sensor and the discharge flow rate is stored in the ROM 16 as shown in FIG.

Next, the routine proceeds to 36 and calculates the difference between the actual discharge flow rate and the target discharge flow rate from the flow rate sensor output signal. If the deviation is zero here, the routine returns to step 30. Then, if NO in step 36, that is, if the deviation is not zero, the routine proceeds to step 37. Here, the correction of the pulse duty ratio for driving the centrifugal blower is calculated so that the target discharge flow rate is achieved according to the deviation calculated in step 36.

Next, the routine proceeds to step 38 to drive the centrifugal blower with the pulse duty calculated in step 37. When this step 38 is completed, the routine returns to step 30, and so-called feedback control is carried out. On the other hand, if NO in step 32, that is, if it is determined that it is not the first operation instruction signal, the routine proceeds to step 39 and determines whether or not the target discharge flow rate value is updated. Here, in the case of YES, the above-described steps 33 to 36 or steps 33 to 38 are executed. If NO, that is, if the target discharge flow rate value has not been updated, steps 33 and 3 are executed.
4 is skipped, the process proceeds to step 35, and the following routines are operated as described above.

[0024]

As described above, according to the present invention, the centrifugal blower can be changed from the two-stage type to the one-stage type, so that the current consumption is reduced and the number of parts is reduced, and the machining and assembling accuracy is reduced. Can be simplified. Further, since the present invention has the flow rate feedback control means, it is possible to directly detect and control the flow rate, which is a physical quantity to be actually controlled, and therefore, it is possible to provide an extremely safe blower,
Highly practical. In addition, since the flow rate is detected on the suction side of the casing, the air flow is less likely to be turbulent than when it is detected on the discharge side, and a rectifying grid is required because the inner surface shape of the sensor mounting pipe 14 is tapered. This has the advantage that the flow rate can be detected easily. On the other hand, the blower driving means is provided with a switching circuit for controlling the pulse duty ratio of the on-time and is executed, so that power saving can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram of a centrifugal fan with a flow sensor according to the present invention.

FIG. 2 is an overall view of a centrifugal fan with a flow sensor according to the present invention.

FIG. 3 is a flowchart of the present invention.

FIG. 4 is a relationship diagram of a pulse duty ratio and a blower discharge flow rate under a certain load.

FIG. 5 is an output signal characteristic diagram of the hot-wire flow sensor.

FIG. 6 is a semi-longitudinal sectional view of a conventional two-stage centrifugal blower.

FIG. 7 is a general discharge pressure-discharge flow rate characteristic diagram of a centrifugal blower.

[Explanation of symbols]

1 Centrifugal fan. 1a Centrifugal fan (lower). 1b
Centrifugal fan (upper). 2 DC motor. 3 Motor base. 4 Suction port. 5 outlets. 6
Scroll type casing. 6a Casing (bottom). 6b Casing (upper). 7 DC motor shaft. 8 Return guide. 9 Casing (upper) suction port. 10 flat washers. 11 Snap ring. 12 Air filter. 13 Hot wire type flow sensor. 14 Sensor mounting tube. 15 Electronic control unit. 1
6 ROM. 17 RAM. 18 C
PU. 19 input ports. 20 output ports.
21 Blower operation instruction signal. 22 Target discharge flow rate instruction signal. 23, 24, 26 AD converter. 25 HIC.
27 DRIVE. 28 Bidirectional bus.
29-38 Each routine of the flowchart. A Flow rate detection means. B Blower request signal. C Target discharge flow rate calculation means. D Pulse duty ratio calculation means. E Blower drive means.

Claims (3)

[Claims] 1. A centrifugal fan comprising a DC motor 2, a centrifugal fan 1, and a scroll type casing 6 having a suction port 4 and a discharge port 5, wherein the suction port 4 of the scroll type casing 6 has a substantially central portion. A sensor mounting pipe 14 provided with a flow sensor 13 is joined to the sensor mounting pipe 14 and an air filter 12 is attached to the atmospheric side end of the sensor mounting pipe 14 to detect the discharge flow rate of the blower on the blower suction side. Centrifugal blower with flow sensor. 2. The flow rate detecting sensor element 13 is mounted such that the position of the flow rate detecting sensor element 13a is offset by d [mm] from the center of the sensor mounting tube 14, and the sensor mounting tube 14 and the scroll type casing. 6
By joining the joint portion with the suction port 4 with a reduction taper of about 15 °, the air flow can be eliminated without disposing a rectifying grid, which is conventionally required, between the air filter 12 and the flow rate sensor 13. The centrifugal blower with a flow sensor according to claim 1, characterized in that the output signal of the flow sensor is stabilized in a laminar flow state. 3. A target discharge flow rate is calculated from a flow rate detection means A by a flow rate sensor 13 provided on a suction port side of a scroll type casing 6 of a centrifugal blower, and a blower request signal B composed of a blower operation and a required flow rate instruction signal. Target discharge flow rate calculation means C and drive pulse duty ratio calculation means D for calculating the pulse duty ratio when driving the blower
2. The drive device for a centrifugal blower with a flow sensor according to claim 1, wherein the blower drive means E for driving the blower with a pulse duty ratio drives the DC motor 2 of the centrifugal blower.