JPH08159833A - Flow measuring device - Google Patents

Abstract

PURPOSE: To provide a heating resistor type flow measuring device detecting an accurate flow rate even against a flow producing the pulsating flow accompanied by the reverse flow. CONSTITUTION: One pair of sub-paths 122, 123 are set inside a main path 8 so as to be approximately in parallel with the center axis of the main path 8 and open in a mutually reverse direction. The reverse side end portions of the respective sub-paths 122, 123 are respectively communicated with the vicinity of the opening portions of the other sub-paths 122, 123. Heating resistors 11, 12 are arranged between communicating portions. Since an air flow in the reverse direction against an air flow direction to be detected is not allowed to flow to the heating resistors 11, 12 in both sub-paths 122, 123, flow detection is accurately conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exothermic resistance type flow rate measuring device for measuring the flow rate of a fluid which flows in a forward direction and a reverse direction or a fluid which may cause a pulsating flow accompanied by a reverse flow,
For example, the present invention relates to a flow rate measuring device suitable for measuring the flow rate in various industrial facilities and air conditioning systems, measuring the intake air flow rate of an internal combustion engine, and particularly measuring the intake air flow rate of an automobile engine.

[0002]

2. Description of the Related Art As a flow rate measuring device capable of detecting a flow rate in the forward and reverse directions, USP. There is a flow measuring device described in the specification of 3147618 and the drawings. This flow rate measuring device includes a pair of temperature detecting elements (temperat)
ure sensing element) in the diametrical direction, insert a flat shield between both elements to divide the flow path into two parts, one element detects the forward flow rate, and the other element detects the reverse flow rate. It is designed to detect In this example, a plate is installed between the elements (heating resistors) so that the shield blocks a considerable area of the flow path.

[0003]

However, the plate must be arranged so as to block (divided into two) a considerable area of the flow path in this way, and naturally the flow resistance of the flow path becomes large. It is not suitable for a flow path where a decrease in inflow efficiency is a problem. Further, since a large eddy current is generated in the wake of the plate, there is a problem that the difference in the heat radiation amount of both heating resistors becomes unclear.

The present invention has been made in view of the above problems in the conventional example, and an object thereof is also for a flow which causes a pulsating flow accompanied by a backflow such as air sucked into an engine of an automobile. It is an object of the present invention to provide a flow rate measuring device capable of appropriately detecting a flow rate in the forward and reverse directions.

Various applications of such a flow rate measuring device are conceivable. Particularly, in the measurement of the intake air flow rate of an automobile engine, a pulsating flow accompanied by a backflow occurs near the throttle fully opening in a specific rotation speed range. An object of the present invention is to provide an air flow rate measuring device capable of eliminating a large plus error in time and achieving fuel control accurately in response to operating conditions.

In order to obtain a flow rate measuring device which achieves such an object, it is necessary to specifically solve the following individual problems.

(1) The flow (flow) resistance of the flow path should not increase.

(2) The flow rate detection accuracy is excellent.

(3) The ability to clearly discriminate between the forward and reverse flows.

(4) Capable of coping with a pulsating flow having a short cycle.

(5) It is possible to measure the entire flow rate range with a small heating resistor.

[0012]

One of the features of the present invention is as follows.
In a flow rate measuring device in which a sub passage is provided inside the main passage and a heating resistor is provided in the sub passage, the sub passage is a pair of sub passages that are substantially parallel to the central axis of the main passage and open in opposite directions. A passage portion is provided, and an end portion on the opposite side to the opening side of each sub passage portion communicates with the vicinity of the opening portion of the other sub passage portion,
The heating resistor is installed between the two communicating portions.

Another feature of the present invention is that in the air flow rate measuring device having a sub passage provided inside the main passage and a heating resistor provided in the sub passage, the sub passage has a central axis of the main passage. The sub-passages are located substantially parallel to each other and have, at both ends thereof, partial openings eccentric to the central axis of the sub-passage. The separating member for dividing into two is provided in a state of being separated from the both end faces.

[0014]

When the flow in the main passage is in the forward direction, the sub-passage opening on the upstream side in the forward direction serves as the inlet of the sub-passage, and almost the entire amount of the flow flowing from the opening into the sub-passage is coaxial with the opening surface. It flows through the passage portion and flows out using the opening surface of the sub passage on the other side as an outlet. At this time, almost no flow occurs in the sub-passage portion different from the sub-passage portion. Further, since it does not serve as a flow separating portion, no large vortex is generated. On the contrary, with respect to the flow in the reverse direction, the opening on the other side, which serves as the outlet in the forward flow, serves as the inlet, almost the entire amount flows into the sub-passage different from the forward direction, and the outlet on the opposite side flows out as the outlet. Therefore, the heating resistor provided in one sub-passage can measure only the flow in either the forward direction or the reverse direction. Also, if heating resistors are provided in both sub-passages and the flow rate of each sub-passage is detected, it is possible to measure both the forward and reverse flow rates. The flow direction can be discriminated by comparing the flow rate detections.

[0015]

EXAMPLES In the examples of the present invention, the following measures are taken in order to solve the above problems.

(1) A mechanism for discriminating the flow in the forward direction and the flow in the reverse direction is formed in the sub passage to secure an effective area of the main passage.

(2) A pair of flow passages in the sub-passage are used as wide passages to reduce the fluid resistance to secure a diversion ratio to the sub-passage and to form a smooth flow passage without an extreme change in cross-sectional area. Stabilize the flow of.

(3) The sub-passage is composed of a pair of passages whose opening surfaces are eccentric, and the flow rate of the fluid flowing through the pair of passages is distinctly different depending on the flow direction of the fluid. Further, in order to prevent a large vortex from being generated in the setting portion of the heating resistor, the heating resistor has a structure that does not become a separation region with respect to both the forward flow and the backward flow.

(4) The main passage is a simple pipe, and the factor affecting the pressure change between the inlet and outlet of the sub passage due to the change of the flow in the forward and reverse directions is eliminated, and the flow in the sub passage becomes smooth. As a configuration, the switching time between the forward flow and the reverse flow is shortened.

(5) The opening of the sub-passage is formed into a contracted flow path or a saucer shape so that a wide range of air can be taken into the sub-passage to reduce the detection error due to the drift of the main passage.

Specific embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view of an air flow rate measuring device according to a first embodiment of the present invention. Air flows parallel to the X axis in the figure, and flows from the left to the right in the forward direction air flow 9
Then, the flow from the right side to the left side is defined as the backward air flow 10. 2 is a view of the air flow rate measuring device of FIG. 1 as viewed from the left side (the upstream side of the forward airflow 9). In this air flow rate measuring device, an insertion hole 3 is provided in a side wall (upper part) of a main body 1 forming a main passage 8 to communicate the main passage 8 with the outside, and a heating resistor 6 and a temperature sensitive resistor 7 are installed. Sub-passage 103,
The sub-passage body 101 forming 104 is the main body 1
Is inserted into the insertion hole 3 from outside and installed in the central portion of the main passage 8 by a holder 4 made of a non-conductive member, and the heating resistor 6 and the temperature sensitive resistor 7 are covered by the holder 4. This structure is electrically connected to the drive circuit built-in module 2 outside the main body 1 via the terminal 5 of the flexible member. Further, the mechanical coupling between the sub-passage body 101 and the drive circuit built-in module 2 is realized by adhesion or the like with the holder 4 of the non-conductive member interposed.

The sub-passage body 101 forms a pair of sub-passage portions 103 and 104 which are substantially parallel to the central axis of the main passage 8 and are eccentric in opposite directions. The sub-passage inlet 103a opens and the backward air flow 10
The sub-passage inlet 104a is opened, and the sub-passage portions 103, 104 are provided with end faces on the side opposite to the inlet, and communication passages 105 formed at two positions in a part between the end face and the inlet.
The structure 106 connects the two auxiliary passage portions 103 and 104 with each other. Then, the heating resistor 6 and the temperature sensitive resistor 7
Is arranged in the sub passage portion 103 between the communication passages 105 and 106 so that the back flow does not act.

With the auxiliary passage body 101 having such a structure, when the forward airflow 9 is generated in the main passage 8, most of the airflow in the auxiliary passage portions 103 and 104 enters from the auxiliary passage inlet 103a. After acting on the heat-generating resistor 6 and the temperature-sensitive resistor 7 in the sub passage portion 103, the sub passage inlet 104a merges with the main passage 8 via the communication passage 105 as an outlet. When the reverse airflow 10 is generated in the main flow path 8, most of the airflow in the sub passages 103 and 104 enters from the sub passage inlet 104 a, passes through the sub passage 104, and passes through the communication passage 106. The secondary passage inlet 103 is used as an outlet to join the main passage 8.

In such a heating resistance type air flow rate measuring device, by devising the sub passages 103 and 104, the air flow in the sub passages 103 and 104 depends on the direction of the air flow in the main passage 8. As a result, the heating resistor 6 has a high detection sensitivity to the forward airflow 9 in the main flow path 8 and flows in the reverse direction. It is possible to reduce the detection sensitivity for the air flow 10.

FIGS. 3 and 4 show a heating resistance type air flow rate measuring device which is a second embodiment in which the structure of the sub-passage body in the first embodiment is changed, and FIG. 3 is a longitudinal sectional view. ,
FIG. 4 is a left side view thereof. The same components as those in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The feature of this second embodiment with respect to the first embodiment is that a sub-passage formed in the sub-passage body 111 is eccentric with respect to the central axis and partially opened at both ends of the sub-passage. In this structure, the passage inlets 112a and 113a are formed, and the separating member 115 is provided so as to divide the inside of the sub passage into two sub passage portions 112 and 113. Separation member 1
Both ends of 15 are positioned so as not to contact both end surfaces of the sub passage, and secure a communication passage that communicates both the sub passage portions 112 and 113. The separating member 115 is the auxiliary passage body 111.
It may be integrally molded with the above or a separate member. In addition, the heat generating resistor 6 and the temperature sensitive resistor 7 are installed at a separating member 11
Set within the length range of 5.

Further, each sub passage portion 11 is located in the vicinity of each sub passage inlet 112a, 113a of the sub passage body 111.
Inclined surfaces 111a, 111 forming the end portions of 2, 113
b stabilizes the flow of the fluid in the sub-passage portions 112 and 113 and reduces the pressure loss in the main passage 8 due to the sub-passage body 111. In addition, the sub passage body 111
As shown in FIG. 3, in the separating member 115 arranged in the above, the sub-passage portions 112 and 113 have inlets 112a and 113, respectively.
It is inclined so that the cross-sectional area gradually increases from the opening surface of a toward the opposite end (back), so that the detection sensitivity of the heating resistor 6 is mainly It becomes higher for the air flow in one direction in the passage 8 and becomes more blunt for the flow in the opposite direction.

FIG. 5 is a vertical cross-sectional view of a heating resistance type air flow measuring device which is a third embodiment in which the installation structure of the heating resistor in the air flow measuring device of the second embodiment is modified. The same components as those in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The basic structure of the sub passage body 121 is similar to that of the second embodiment, and the sub passage body 1
The heating resistor 1 is provided in each of the two auxiliary passage portions 122 and 123 formed by dividing the inside of 21 by the separating member 125.
1, 12 are arranged. Accordingly, when the forward airflow 9 is generated in the main passage 8, a part of the airflow flowing into the sub-passage body 121 from the sub-passage inlet 122a mainly flows through the sub-passage portion 122 in the sub-passage body 121. It flows and acts strongly on the heat generating resistor 11 to increase the detection sensitivity of the heat generating resistor 11, and makes the detection sensitivity of the heat generating resistor 12 installed in the sub-passage portion 123 dull. On the contrary, when the reverse airflow 10 is generated in the main passage 8, a part of the airflow flowing into the auxiliary passage body 121 from the auxiliary passage inlet 123a mainly flows in the auxiliary passage portion 123 in the auxiliary passage body 121. It strongly acts on the heating resistor 12 to increase the detection sensitivity of the heating resistor 12, and weakens the detection sensitivity of the heating resistor 11 installed in the sub-passage portion 122b.

Therefore, the direction of the air flow in the main passage 8 is determined by the magnitude of the flow rate detection signal using the heating resistors 11 and 12, and the larger value of the flow rate detection signal is output as the flow rate detection signal. By doing so, it becomes possible to measure the flow direction of the air flow and its flow rate.

FIG. 6 shows the flow rate detection signal voltage using the heating resistors 11 and 12 in the third embodiment of the present invention. In the state where the forward airflow 9 is generated in the main passage 8, the detection signal by the heating resistor 11 is large and the detection signal by the heating resistor 12 is small. In this embodiment, when the forward airflow 9 having a flow rate of 60 kg / h is generated in the main passage 8, the magnitude of the flow rate detection signal by the heating resistor 12 is about 1/5 of the flow rate detection signal by the heating resistor 11. It was

The sub-passage body 121 makes the central axes of the sub-passage portion 122 and the sub-passage 123 substantially coincide with the centers of the openings of the inlets 122a, 123a, thereby smoothing the air flow and reducing the pressure loss in the sub-passage. Can be reduced. In addition, the cross-sectional areas of the communication portions 126 and 127 that communicate between the sub passage portions 122 and 123 are determined by the sub passage inlet 122a,
Making the cross-sectional area larger than 123a is also effective in reducing the pressure loss in the auxiliary passage.

Further, the sub-passage body 121 is made point-symmetrical with respect to the midpoint 13 of the sub-passage so that the two sub-passages have the same shape and promote the improvement of productivity. It is valid.

Furthermore, in order to reduce the noise mixed in the flow rate detection signal due to the turbulence of the air flow, the auxiliary passage body 1
21 to the sub-channel inlets 122a and 123a
It is effective to form a and 121b.

7 and 8 show a heating resistance type air flow rate device showing a fourth embodiment of the present invention. FIG. 7 is a longitudinal sectional view and FIG. 8 is a left side view thereof. The same components as those in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The feature of this embodiment is that the auxiliary passage body 131 is provided.
The sub-flow path inlets 132a, 133a of the compressed flow paths 132b, 1
33b is provided to reduce the occurrence of a measurement error due to a change in the diversion ratio of the airflow flowing into the sub passage when a drift occurs in the main passage 8. This sub-flow passage body 131 is installed in the central portion of the main passage 8 by the holder 4 inserted from the insertion hole formed in the side wall (lateral portion) of the main body 1, and the heat-generating resistance installed in the sub-passage portions 132 and 133. It has bodies 11 and 12. Then, the heating resistors 11 and 1
2 is electrically connected to the drive circuit built-in module 2.

9 and 10 show a heating resistance type air flow rate measuring device which is a fifth embodiment in which the structure of the sub-passage body in the fourth embodiment is changed, and FIG. 9 is a longitudinal sectional view. FIG. 10 is a left side view thereof. The same explanations are omitted for the components common to the above-described embodiment.

The feature of this embodiment is that the contraction passages 132b, 133b in the fourth embodiment are further expanded to form the pan-shaped ovals 142c, 143c.
By setting 41, the influence of uneven flow in the upstream is reduced. 11 to 13 show a heating resistance type air flow rate measuring device according to a sixth embodiment of the present invention, wherein FIG. 11 is a longitudinal sectional view, FIG. 12 is a left side view thereof, and FIG. 13 is a separating member thereof. FIG.

In this embodiment, the sub passage body 151 in which the flow rate detecting portion is installed is integrally formed with the main body 21 forming the main passage 20. Separation member 22 for dividing the inside of the sub passage body 151 into two sub passage portions 152 and 153.
Is integrally formed with the module portion 23 having a built-in drive circuit, and penetrates the main body 21 and the sub passage body 151 and is inserted into the sub passage body 151 to be installed.

As shown in FIG. 13, the separating member 22 is a separating member in which a heating resistor layer 22b is formed on the surface of an insulating substrate 22a and a heating resistor for flow rate detection is integrated.

FIG. 14 shows a modified example of the separating member 22. In this modified example, the heating resistors 22b and 22c are formed in a film shape on both surfaces of the insulating substrate 22a to form two sub passage portions 152, It enables to detect the flow rate at 153. In this embodiment, by deforming the separating member 22 in this way, it is possible to obtain the same function as in the third embodiment.

FIG. 15 shows an embodiment of an electronic circuit in the heating resistance type air flow rate measuring device according to the present invention. The circuit that controls the heating of the two heating resistors is independent.
Configure one bridge circuit. The forward flow control detection circuit 30 is a bridge circuit including a heating resistor for detecting the flow rate in the forward flow direction. The bridge circuit controls the heating temperature of the heating resistor and the forward flow rate detection signal V.
_{Get 01} . The backflow control detection circuit 31 has exactly the same configuration as the forward flow side, controls the heating temperature of the heating resistor that detects the flow rate in the backflow direction, and outputs the backflow direction flow rate detection signal V ₀₂ . The flow rate signal switching circuit 32 compares the magnitudes of the forward flow rate detection signal V ₀₁ and the reverse flow rate detection signal V ₀₂ , and outputs the larger signal as the flow rate detection signal V ₀ . Flow direction determination circuit 33
Compares the magnitudes of the forward flow and reverse flow flow rate detection signals V ₀₁ and V _02. For example, when the forward flow rate detection signal V ₀₁ is large, D =
The direction detection signal D that clearly indicates the flow direction is output such that a constant value of 5 V is output and D = 0 V is output when the backflow flow rate detection signal V ₀₂ is large.

FIG. 16 shows an example of the output signal from the electronic circuit shown in FIG. 15, and shows the output signal when the pulsating flow accompanied by backflow is being measured. The forward flow rate detection signal V ₀₁ and the reverse flow rate detection signal V ₀₂ are selected by the flow rate signal switching circuit 32 and one flow rate detection signal V _{0 is selected.}
Is output as Therefore, in the pulsating flow accompanied by the backflow, as shown in FIG. 16, the mountain-shaped waveform flow rate detection signal V ₀ corresponding to the two detection signals of the forward flow and the backflow per period is output. At the same time, the flow direction determination circuit 33 outputs a direction detection signal D for distinguishing between forward flow and reverse flow.

The control system determines whether the flow rate measured based on these two detection signals V ₀ and D is forward flow or reverse flow, and performs control suitable for that state. For example, measuring the flow rate of air drawn into an automobile engine,
In a control system that controls the fuel amount according to the air flow rate, the air flow rate that is actually taken into the engine is the amount obtained by subtracting the backward flow rate from the forward flow rate measured by the flow rate measuring device. By subtracting the backward flow rate integrated value per cycle from the forward flow rate integrated value per cycle to obtain the air flow rate taken into the engine per cycle, and controlling the fuel amount according to the air flow rate, Appropriate air-fuel ratio control is performed even in a pulsating flow accompanied by backflow.

FIG. 17 shows a flow rate detection signal in a modified example in which the electronic circuit shown in FIG. 15 is modified. In this modified example, the flow direction determination circuit 33 is omitted, and the flow rate signal switching circuit 32 uses a forward flow rate detection signal V ₀₁ and a reverse flow rate detection signal V.
₀₂ , a certain regulation level is set as an output signal level at a flow rate of 0 (zero), and when the forward flow rate is larger than the reverse flow rate, the signal is output as a forward flow rate detection signal that changes in the positive direction from the regulation level, while the reverse flow rate is output. When the flow rate is greater than the forward flow rate, the forward flow rate detection signal and the backward flow rate signal are output even in the pulsating flow accompanied by the backward flow by outputting as a backward flow rate detection signal that changes in the negative direction inverted with respect to the regulation level. It is possible to output a signal to one output line.

According to this modification, the flow direction discrimination signal 3
The flow rate in the forward and reverse directions can be measured without using 3.
Even in a control system for an automobile engine as described above, the air flow rate taken into the engine is calculated by simply integrating the flow rate detection signals in both directions and setting the regulation level to 0 (zero) to obtain the total flow rate. It can be obtained while eliminating the error due to backflow.

Further, the air flow rate measuring device according to the present invention is
In the electronic circuit shown in FIG. 15, the flow rate signal switching circuit 32 may be omitted, and the electronic circuit shown in FIG. 15 may be applied to a control system that uses only the direction detection signal output from the flow direction determination circuit 33. Furthermore, the flow rate signal switching circuit 32 and the flow direction determination circuit 33 are omitted, and the present invention can be applied to a control system that directly uses the forward flow rate detection signal Vo1 and the reverse flow rate detection signal Vo2.

FIG. 18 shows output signal (voltage) characteristics of the air flow measuring device according to the present invention and the conventional air flow measuring device. The engine speed is taken as a parameter, and the output voltage V ₀ (average value) of the air flow rate measuring device with respect to the engine suction negative pressure ΔP is shown. In the conventional air flow rate measuring device, when the engine speed is 2000 rpm, a jump phenomenon occurs in which the output voltage rapidly increases near the engine suction negative pressure of 0 (zero). This is
As shown in 9, a flow rate detection signal of reverse flow heating resistor is detected by counting the positive value, it to output the actual average output voltage V ₀ output voltage V ₀ which higher than (a) (b) It is caused by.

However, according to the air flow rate measuring device of the present invention, the reverse flow rate is not erroneously detected as the forward flow rate, and the reverse flow rate is measured and subtracted from the forward flow rate. Near average output voltage V
It becomes possible to output ₀ (a).

Although the sub-passage body in each of the above-mentioned embodiments is configured so that the inlet of each sub-passage portion is offset with respect to the ventilation axis of the main passage, it may be opened coaxially. .

According to each of the embodiments described above, after all, a pair of sub-passage portions that are substantially parallel to the central axis of the main passage are opened so as to be opposite to each other, and the end portion on the side opposite to the opening surface is closed. With the sub-passage structure connected near the opening of the sub-passage, when the flow of the main passage is in the forward direction, the sub-passage part opening surface on the upstream side in the forward direction becomes the inlet of the sub-passage, Almost all of the flow that has flowed into the sub-passage flows through the sub-passage portion that is coaxial with the opening face, and flows out through the opening face of the other sub-passage as the outlet. At this time, almost no flow is generated in the sub-passage portion different from the sub-passage portion, and the sub-passage portion does not serve as a flow separating portion, so that no large vortex is generated. On the other hand, for the flow in the reverse direction, the opening surface that became the outlet in the forward flow becomes the inlet, and almost the entire amount flows in the sub-passage part different from the forward direction, and the opening surface on the opposite side flows out as the outlet. Therefore, if a heating resistor is provided in one sub passage to detect the flow rate, only the flow in either the forward direction or the reverse direction can be measured. In addition, if heating resistors are installed in both sub-passages and the flow rate of each sub-passage is detected, it is possible to measure both the forward flow rate and the reverse flow rate. It is possible to determine the flow direction by comparing

The reason why the two sub-flow passages are expanded passages from the opening toward the opposite end is to reduce the fluid resistance of the sub-passage and obtain a sufficient diversion ratio to the sub-passage. At the same time, the flow that flows in from the opening part easily flows to the sub-passage part that is a wide passage with a small fluid resistance. On the other hand, the other sub-passage becomes a compressed flow path, which increases the fluid resistance and makes it difficult to flow. This is to further increase the difference in flow rate between the two auxiliary passage portions depending on the direction.

The function of the sub-passage is to partially provide an opening eccentric with respect to the central axis of the sub-passage on both end faces of one sub-passage, and to provide a separating member for dividing the sub-passage on both end faces. This can be achieved by a structure provided so as not to contact with each other, and a simple and small auxiliary passage structure can be obtained. The function is more exerted when the center axis of each of the bisected flow passages and the center of the opening surface are substantially aligned with each other. If the auxiliary passage has a shape symmetrical with respect to the midpoint of the auxiliary passage, The flow and the flow in the opposite direction can be measured under the same conditions. Further, by setting the separating member in an inclined manner, each of the two divided passages can be expanded to be a passage. Further, the flow passage can be smoothed by inclining the end surface portion other than the opening surface.

As described above, since it is possible to provide a comparatively small auxiliary passage with a measurable mechanism for separating the flow in the forward direction and the flow in the reverse direction, the main passage can be a simple pipe passage and is sufficiently effective. Since the area can be secured, the flow rate can be detected in the forward and reverse directions without increasing the fluid resistance of the flow rate measuring device. Further, since the flow in the sub passage is smooth and a sufficient diversion ratio can be obtained, it is possible to prevent the detection accuracy from deteriorating.

Further, as a means for stabilizing the flow in the sub-passage, improving detection accuracy and reducing output noise, there is a structure in which a straight pipe is provided in the opening surface to rectify the flow flowing into the sub-passage to some extent. In addition, since a wide range of flow can be introduced into the sub-passage by providing a constricted flow path in the opening or by making the opening into a saucer shape, the flow distribution ratio to the sub-passage when a non-uniform flow occurs in the main passage. It is possible to reduce the measurement error due to the change of

Most of the structure of the sub-passage can be molded or cast integrally with the member forming the main passage, and the passage can be completed by joining different members. That is, the main passage and the sub passage can be integrally formed. Further, the sub passage may be fixed to and integrated with a circuit module having an electronic circuit for controlling heating of the heating resistor or performing signal processing. With such a configuration, since the circuit module can have most of the functions of the heat generation resistance type flow rate measuring device other than the main passage, the circuit module can be handled as one product, and the fluid to be measured can be handled on the side of use. The flow rate can be detected by inserting and attaching the sub passage portion in the flow passage.

On the other hand, in the sub-passage structure, if a plate-shaped resistor formed in a film shape on one side or both sides of the insulating substrate is used as the heating resistor, the insulating substrate can be used as the separating member for the sub-passage. Therefore, the configuration of the sub passage can be further simplified.

As described above, since the passage structure capable of measuring the forward flow rate and the reverse flow rate is obtained, each of the forward flow rate detection signal and the backward flow rate detection signal is detected as the detection output of the flow rate measuring device. If output, the control system can determine the actual flow and perform appropriate control. Also, if the electronic circuit of the flow rate measuring device compares the flow rates in the forward direction and the reverse direction and always outputs the one with the higher flow rate, a single flow rate detection signal will pass through the flow rate measuring device regardless of the flow direction. The flow rate can be represented, and a signal for discriminating the flow direction between the forward direction and the reverse direction can be output. Further, if the flow rate detection signal in the forward direction is set to a certain level or more, for example, 0 (zero) level or more, that is, a positive output, and the flow rate signal in the reverse direction is set to a certain level or less, for example, a negative output, the integration of both signals is performed. The value is the total forward flow rate value.For example, when measuring the flow rate of air drawn into an internal combustion engine, even if the flow is a pulsating flow with backflow, the flow rate detection signal obtained by subtracting the backflow component from the forward flow rate is used. Since the flow rate measuring device outputs, its output signal becomes equal to the air flow rate actually taken into the internal combustion engine. Therefore, even in an automobile engine or the like, a positive error due to a discrepancy between the flow rate detection signal of the flow rate measuring device due to the backflow and the air flow rate actually sucked into the engine does not occur under the operating condition of the pulsating flow accompanied by the backflow,
Proper fuel control is always possible.

[0059]

According to the present invention, the sub-passage is divided into two sub-passage portions which are less affected by the flow in the forward and reverse directions,
By installing an element for detecting the air flow rate in the sub-passage portion, it becomes possible to detect the flow rate with less influence of backflow. Further, there is an effect that it is possible to provide a highly accurate flow rate measuring device capable of measuring a reverse flow rate of a reverse flow and performing measurement close to an actual flow rate.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view of an air flow rate measuring device showing a first embodiment of the present invention.

FIG. 2 is a left side view of the air flow rate measuring device shown in FIG.

FIG. 3 is a vertical cross-sectional side view of an air flow rate measuring device showing a second embodiment of the present invention.

FIG. 4 is a left side view of the air flow measuring device shown in FIG.

FIG. 5 is a vertical cross-sectional side view of an air flow rate measuring device showing a third embodiment of the present invention.

FIG. 6 is an output characteristic diagram of the air flow rate measuring device according to the third embodiment shown in FIG.

FIG. 7 is a vertical sectional side view of an air flow measuring device showing a third embodiment of the present invention.

8 is a left side view of the air flow measuring device shown in FIG.

FIG. 9 is a vertical sectional side view of an air flow measuring device showing a fourth embodiment of the present invention.

FIG. 10 is a left side view of the air dragon utilization measuring device shown in FIG.

FIG. 11 is a vertical cross-sectional side view of an air flow rate measuring device showing a fifth embodiment of the present invention.

12 is a left side view of the air flow measuring device shown in FIG.

FIG. 13 is a vertical sectional side view of a separating member in the air flow rate measuring device shown in FIGS. 11 and 12.

FIG. 14 is a vertical cross-sectional side view of a modified example of the separating member in the air flow rate measuring device shown in FIGS. 11 and 12.

FIG. 15 is an electronic circuit diagram for control in the air flow rate measuring device according to the present invention.

16 is an output characteristic diagram of the air flow rate measuring device according to the present invention using the electronic circuit shown in FIG.

17 is an output characteristic diagram of the air flow rate measuring device according to the present invention, which is used by modifying the electronic circuit shown in FIG.

FIG. 18 is a comparative example of the output characteristics of the air flow measuring device according to the present invention and the conventional air flow measuring device.

FIG. 19 is an explanatory diagram of output characteristics of the air flow measuring device.

[Explanation of symbols]

 1 Main Body 2 Module with Built-in Drive Circuit 4 Holder 5 Terminals 6, 11, 12 Heat Generation Resistor 7 Temperature Sensitive Resistor 8 Main Passage 9 Forward Air Flow 10 Reverse Air Flow 101,121 Sub-passage Body 103,104,122, 123 Sub-passage part 103a, 104a, 122a, 123a Sub-passage inlet 105, 106, 126, 127 Communication part 125 Separation member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinya Igarashi 2471 Kashima Yatsu, Hitachi Takanaka City, Ibaraki Pref. 3 Hitachi Automotive Engineer Ring Co., Ltd. (72) Inventor Chihiro Kobayashi 2520 Takaba, Hitachinaka City, Ibaraki Prefecture Incorporated company Hitachi Ltd. Automotive Equipment Division (72) Inventor Tadao Suzuki 2520 Takaba, Hitachinaka City, Ibaraki Prefecture Incorporated Hitachi Ltd. Automotive Equipment Division (72) Mitsuru Tsumaga 2520 Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi, Ltd. Automotive Equipment Division

Claims (21)

[Claims] 1. A flow measuring device having a sub-passage inside a main passage and a heating resistor in the sub-passage, wherein the sub-passages are substantially parallel to a central axis of the main passage and opposite to each other. A pair of sub-passage portions that open are provided, and the ends of the sub-passage portions on the opposite side to the opening side communicate with the vicinity of the opening of the other sub-passage portion, respectively, and the heating resistor is provided between the two communication portions. A flow rate measuring device characterized by being installed. 2. The pair of sub-passage portions are in contact with each other, and the end portion on the opposite side to the opening side is communicated by a hole provided in a wall surface in contact with the pair of sub-passage portions. Flow measuring device. 3. The pair of sub-passage portions are passages of a divergent shape whose cross-sectional area increases from the respective opening sides toward the opposite end portions, respectively. Flow rate measuring device. 4. An air flow rate measuring device having a sub-passage inside a main passage and a heating resistor inside the sub-passage, wherein the sub-passage is positioned substantially parallel to a central axis of the main passage, At both ends thereof, a partial opening eccentric to the central axis of the sub passage is provided, and in the sub passage, a separating member that divides the sub passage into two substantially parallel to the central axis of the sub passage is provided. A flow rate measuring device characterized in that it is provided in a state of being separated from both end faces. 5. The center axis of each passage in the sub passage divided into two parts by the separating member and the center axes of the eccentric openings at both ends of the sub passage are substantially coincident with each other. The flow rate measuring device described in. 6. The flow rate measurement device according to claim 4, wherein the separating member is inclined so that a cross-sectional area of each passage portion formed by separating the sub passage is gradually increased. apparatus. 7. The opening surfaces at both ends of the sub passage are perpendicular to the central axis of the sub passage, and the end surfaces other than the opening surface form a surface inclined with respect to the central axis of the sub passage. The flow rate measuring device according to any one of claims 4 to 6, characterized in that. 8. The flow rate measuring device according to claim 1, wherein the auxiliary passage has a symmetrical shape with respect to a midpoint of the auxiliary passage. 9. The flow rate measuring device according to claim 1, wherein a straight pipe path is provided in both or one of the openings of the sub-passage. 10. The flow rate measuring device according to claim 1, wherein a contraction flow channel is formed in both or one of the openings of the sub-passage. 11. The flow rate measuring device according to claim 1, wherein both or one of the openings of the sub passage is formed in a saucer shape. 12. The sub passage is integrally formed with a member forming the main passage.
1. The flow rate measuring device according to any one of 1. 13. The member forming the sub-passage is fixed so as to be integrated with a circuit module having an electronic circuit for controlling heating of the heating resistor or performing signal processing. Any one from 1 to 11
The flow rate measuring device described in. 14. The flow rate measuring device according to claim 1, wherein a heat generating resistor for flow rate detection is installed in each of the pair of passage portions of the sub passage. 15. The heating resistor is formed in a film shape on an insulating substrate, and is set in the sub passage so as to function as the separating member, and divides the sub passage. The flow rate measuring device according to any one of 4 to 13. 16. The flow rate measuring device according to claim 15, wherein the heating resistor is formed in a film shape on both surfaces of the insulating substrate. 17. An electronic circuit for controlling heating of the heating resistors arranged in the pair of passages and detecting a flow rate of fluid flowing through the passages.
6. The flow rate measuring device according to any one of 6 above. 18. The flow rate measuring device according to claim 17, wherein the electronic circuit compares the flow rates of the fluids flowing through the pair of passage portions and outputs a flow rate detection signal having a larger flow rate. 19. The electronic circuit outputs a flow rate detection signal having a larger flow rate of the fluid flowing through the pair of passage portions and a determination signal indicating which passage portion has a larger flow amount. Item 18. The flow rate measuring device according to item 18. 20. The electronic circuit sets the flow rate detection signal of one side of the flow rate flowing through the pair of passage portions to a signal higher than a prescribed level, and sets the flow rate detection signal of the flow rate of the other side passage portion to the prescribed level. The flow rate measuring device according to claim 17, wherein the flow rate measuring device outputs as a smaller inverted signal. 21. The flow rate according to claim 1, wherein the constituent means other than the main passage is integrated and is inserted into a flow path through which a fluid to be measured flows to detect the flow rate. measuring device.