JPH0816621B2 - Engine intake air amount measuring device - Google Patents

Description

The present invention relates to a gas flow rate measuring device for measuring the flow rate of gas, for example, air flowing in a flow passage tube.

[Conventional technology]

2. Description of the Related Art Conventionally, in an engine for a vehicle, an air flow rate measuring device for measuring the air amount is mounted in order to supply the engine with a fuel amount corresponding to the air amount sucked into the engine.

In recent years, various measuring devices such as a vane type, a heating wire type, and a Karman vortex type have been developed for vehicles, and some of them are actually used.

The vane type air flow rate measuring device is, for example, as disclosed in Japanese Patent Publication No. 59-12865, a rectangular vane (cushion plate) which is set in a state of being swirlable across a rectangular flow path cross section. It was rotated by receiving the pressure difference caused by the flow, and the air flow rate was measured from this rotation angle.

[Problems to be solved by the invention]

However, in the above vane type air flow rate measuring device, as the air flow rate increases, the opening degree of the vane increases,
Since the vertical component of the pressure receiving surface where the vane receives pressure from the air flow is reduced, and the higher the air flow rate is, the less the ratio of the air flow pressure transmitted to the vane side is reduced. In the high air flow rate region, the change in the opening of the vane with respect to the change in the flow rate, that is, the change in the rotation angle of the vane is extremely small, and therefore, there is a problem that the measurement accuracy in the high air flow rate state is not sufficient.

Further, in the configuration disclosed in the above publication, in order to prevent the vane from vibrating due to the pulsation of the air flow and the vane from excessively changing due to a rapid change in the air flow rate, the vane is pushed to the side of the air passage. A fan-shaped chamber is formed, and a damping plate and a vane that swirl the chamber are connected to each other, and an air damping function of the chamber and the damping plate acts on the vane. However, the size (volume) of this fan-shaped chamber cannot be made very small in order to make its air damping function sufficient, and it is set so as to squeeze out to the side of the air passage. Therefore, there is a problem that the device itself becomes large and there are many restrictions when mounted on the vehicle, that is, the mountability on the vehicle is poor.

Further, as disclosed in Japanese Examined Patent Publication No. 28-6336, Japanese Utility Model Publication No. 57-72118, British Patent Application Publication No. 2123964, and Japanese Unexamined Patent Publication No. 53-100271, etc., along the flow direction of the fluid to be measured. Although there are many known flow rate measuring devices in which the moving member moves in the axial direction to measure the flow rate, these devices tend to have excessive reaction of the moving member to changes in the flow rate, and the displacement of the moving member may overshoot or undershoot. There was a problem that it was impossible to measure the flow rate accurately and stably by shooting. Such a problem has a problem that an unnecessary change in the measurement signal occurs in an engine, especially in an application in which the flow rate changes greatly such as an automobile engine.

Further, in the above-mentioned conventional technology, there is one in which the moving member moves to increase the flow passage cross-sectional area as the flow rate increases.
When the moving member moves greatly at high flow rate and the flow passage cross-sectional area opens greatly, it becomes impossible to obtain the required pressure difference between the upstream side and the downstream side of the moving member, and the displacement amount of the moving member in the high flow rate range becomes large. However, there was a problem in that it could not respond to changes in the flow rate.

Therefore, in view of the above problems, the present invention is suitable for a configuration in which a moving member moves along the flow direction of intake air, and in the configuration, excessive displacement of the moving member due to a sudden change in the intake air amount of the engine is simple. It is an object of the present invention to provide an intake air amount measuring device for an engine having a compact structure that can suppress the air flow rate and can reliably measure the air flow rate in a wide range from a low flow rate to a high flow rate.

[Means for solving problems]

In order to achieve the above object, the present invention provides an intake air amount measuring device for an engine, which measures an intake air amount of an engine, wherein the intake air amount measuring device is provided in a part of an intake pipe of the engine and allows the intake air to flow in an axial direction thereof. A flow channel pipe formed so that its flow channel cross-sectional area increases along a flow direction of the intake air in a predetermined range, and the flow channel pipe is located at a downstream side of the predetermined range of the flow channel pipe. A central member supported in the center, and provided in the flow path pipe with a predetermined range on the upstream side of the central member as a movement range, and linearly movable along the flow direction of the intake air by the central member. A moving member that is supported in a state in which the inside of the flow path pipe is substantially closed and is displaced downstream according to the amount of intake air, and a pressing force is applied to the moving member in a direction opposite to the flow direction of the intake air. Work A pressure member; and a conversion means for converting the displacement amount of the moving member into an electric signal. The moving member is provided with a first cylinder (3b) extending along the flow direction of intake air, The member is a cylinder that extends along the flow direction of the intake air, and is fitted to the outside of the first cylinder with a minute gap, and abruptly moves the moving member to the inside of both cylinders by air pressure. Second to form an air damper chamber that suppresses unnecessary movement
A cylinder (1b2) is provided, and when the moving member moves to the downstream side of the intake air, the moving member is provided with an inlet for the gap between the first cylinder and the second cylinder. A technical means called an intake air amount measuring device for an engine, which is characterized in that an outer edge portion (3a) projecting in an eaves-like shape is provided on the upstream side.

(Operation) According to the configuration of the present invention described above, the moving member is displaced in the flow path pipe along the flow direction of the intake air according to the intake air amount. Then, this displacement amount is converted into an electric signal by the conversion means and output.

In the configuration of the present invention, the first cylinder extending from the moving member,
A second cylinder extending from the central member is fitted with a minute gap, and an air damper chamber is formed inside both of these cylinders. Air pressure in the air damper chamber causes a sudden displacement of the moving member. Suppressed.

Moreover, since the second cylinder is located outside the first cylinder, the inlet of the gap between the first cylinder and the second cylinder is open toward the upstream side. The moving member is provided with an outer edge portion protruding like an eaves, and when the moving member moves to the downstream side, the outer edge portion is positioned on the upstream side of the inlet of the gap. Therefore, the negative pressure generated downstream of the outer edge portion protruding like an eaves is introduced from the inlet through the gap into the air damper chamber inside the first cylinder, which is the downstream side of the moving member, and even at a high flow rate. The pressure on the downstream side of the moving member can be lower than that on the upstream side of the moving member.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 to 5 show a configuration of an embodiment of an air flow measuring device for measuring a flow rate of air drawn into a vehicle engine, particularly an automobile engine,
In the figure, a flow passage pipe 1 constitutes a part of an intake pipe of an engine (not shown) and is composed of three housings 1a, 1b, 1c, and is arranged along the air flow direction of each housing 1a, 1b, 1c. The cross-sectional shape is circular, and the housings 1a, 1b, 1c are linearly arranged so as to have the same central axis. An air passage 2 through which air flows in the axial direction is formed inside the passage pipe 1 constituted by the housings 1a, 1b, 1c. In addition, each housing 1
a, 1b, 1c are securely sealed at each joint so that there is no flow of air to the outside, and each housing 1a, 1c
When b and 1c are made of a resin material, they are sealed by adhesion or welding.

In the air flow path 2, there is provided a moving member 3 made of a resin material that is set so as to be linearly movable along the air flow direction. On the other hand, it has a convex shape on the upstream side, and the surface of the convex shape forms a smooth curved surface centered on the central axis of the flow path tube 1.

The main part of the moving member 3 is set so as to move inside the housing 1a located on the most upstream side among the housings 1a, 1b, 1c constituting the flow path pipe 1, and the outer edge of the moving member 3 The housing 1a is so constructed that the annular air passage area (throttle area) formed between the member 3a and the inner peripheral wall surface 1a1 of the housing 1a increases as the moving member 3 moves downstream. The moving member 3 is formed such that its cross-sectional area becomes wider toward the downstream side in the range in which the main part of the moving member 3 moves. Moreover, the housing is adjusted so that the moving amount of the moving member 3 and the increase / decrease in the air passage area have a predetermined functional relationship.
The inner peripheral wall surface 1a1 of 1a is adjusted. The most downstream portion of the moving member 3 projects like an eaves outside the outer cylinder, and this projecting portion forms the outer edge member 3a.

Further, at the upstream air inlet end of the housing 1a, the position of the uppermost stream side of the moving member 3, that is, the outer edge portion of the moving member 3
A fully closed stopper 1a2 that regulates the fully closed position of the moving member 3 that minimizes the air passage area between the inner peripheral wall surface 1a1 of the housing 1a and the inner peripheral wall surface 1a1 of the housing 1a It is formed integrally with the housing 1a while being supported so as to be positioned on the central axis by three ribs 1a3 extending in the central axis direction (see FIG. 2). When the moving member 3 is in the fully closed position, the housing of the moving member 3
The apex set on the center axis of 1a is the fully closed stopper 1a
It comes into contact with 2. Note that each rib 1a3 has a streamline cross-sectional shape so as not to disturb the air flow.

Further, a bypass passage 1a4 that bypasses the moving member 3 of the air passage 2 is formed in the housing 1a, and a bypass screw 4 for adjusting the amount of bypass air passing through the bypass passage 1a4 is formed in the bypass passage 1a4. The bypass passage 1a4 is provided so as to be able to advance and retreat.
That is, the threaded portion 1a41 is provided on the inner wall surface of the bypass passage 1a4.
Is formed, and by screwing in or unscrewing the bypass screw 4, the bypass screw 4 moves back and forth in the bypass passage 1a4. An O-ring 5 is set between the bypass screw 4 and the inner peripheral wall surface of the bypass passage 1a4 in order to secure the seal at this portion. By adjusting the amount of air passing through the bypass passage 1a4, the air-fuel ratio of the air-fuel mixture supplied to the engine (not shown) during idling is adjusted.

By the way, the moving member 3 is set so as to be housed in the outer cylinder 3b and the outer cylinder 3b which extends in the downstream direction along the air flow direction and has an outer diameter smaller than the diameter of the cylindrical outer edge portion 3a. The inner cylinder 3c is integrally formed. Both the outer cylinder 3b and the inner cylinder 3c are centered on the central axis of the housing 1a, and a predetermined space is set between the outer cylinder 3b and the inner cylinder 3c. Also, the outer cylinder 3b and the inner cylinder 3c
The upstream end is closed by the moving member 3 and the downstream end is open.

Further, a shaft 3d extending in the downstream direction, which coincides with the central axis of the housing 1a, is integrally connected and fixed to the moving member 3.

Next, the housing 1b has four ribs 1b1 (third rib) extending from the inner wall surface of the housing 1b in the central axis direction of the housing 1b.
(See the drawing), the cylindrical large diameter cylindrical portion 1b2 supported by the rib 1b1, the intermediate cylindrical portion 1b3 provided so as to be housed in the large diameter cylindrical portion 1b2, and the intermediate cylindrical portion 1b3. The small-diameter cylindrical portion 1b4 thus provided is integrally formed. The large-diameter cylindrical portion 1b2, the intermediate cylindrical portion 1b3, and the small-diameter cylindrical portion 1b4 are all formed around the central axis of the housing 1b, and the inner diameter of the large-diameter cylindrical portion 1b2 is the outer diameter of the outer cylinder 3b of the moving member 3. Slightly larger than that, the outer diameter of the intermediate cylindrical portion 1b3 is smaller than the inner diameter of the outer cylinder 3b of the moving member 3, the inner diameter is larger than the outer diameter of the inner cylinder 3c of the moving member 3, and the outer diameter of the small-diameter cylindrical portion 1b4. Is smaller than the inner diameter of the inner cylinder 3c of the moving member 3. These large-diameter cylindrical parts 1b2
The intermediate cylindrical portion 1b3 and the small-diameter cylindrical portion 1b4 form a central member supported substantially at the center of the flow path pipe 1, and the central member is supported by the four ribs 1b1.

The small-diameter cylindrical portion 1b4 communicates in the axial direction, and the shaft 3d penetrates on the central axis thereof. In this small-diameter cylindrical portion 1b4, two sets of bearing portions 6a and 6b made of ball bearings are held by a retainer 7 and fixed to the inner peripheral side thereof,
3d is bearings 6a, 6b, cage 7, and small diameter cylindrical part 1b4
It is movably supported in the direction of the central axis by a bearing 8 composed of, for example. In this bearing 8, the bearing portion 6
a and 6b are set in the cage 7 in series, and the bearings 6a and 6b are urged in opposite directions by a spring set between the bearings 6a and 6b. And the bearing portion 6b is held by abutting against the ring-shaped holder 9 engaged with the retainer 7.

The large-diameter cylindrical portion 1b2 and the outer cylinder 3b of the moving member 3 are separated from each other by a predetermined appropriate clearance, that is, a minute gap.
3b is set to be fitted in the large-diameter cylindrical portion 1b2, and the outer cylinder 3b moves in the large-diameter cylindrical portion 1b2 according to the movement of the moving member 3 from the fully closed state to the fully opened state. It is configured. The downstream side of the large diameter cylindrical portion 1b2 is sealed to the air passage 2 by a cover 1c1 which is integrally formed with a housing 1c described later, and thus the large diameter cylindrical portion 1b2 is formed.
The space formed by the outer cylinder 3b and the outer cylinder 3b communicates with the air passage 2 only through the clearance between the large-diameter cylinder portion 1b2 and the outer cylinder 3b, and the moving member 3 due to the pulsation of the air flow or the sudden change of the air flow rate.
The air damper chamber 10 is configured to stabilize the fluctuation of

In the air damper chamber 10, the moving member 3 is in the fully closing direction,
That is, the coil spring 11 that presses in the direction opposite to the air flow direction is set, and one end of the spring 11 abuts the bottom of the annular groove between the outer cylinder 3b and the inner cylinder 3c of the moving member 3, The other end is in contact with an annular slider 12 set between the intermediate cylindrical portion 1b3 and the small diameter cylindrical portion 1b4.
The spring 11 is guided by the outer peripheral wall surface of the inner cylinder 3c. By the way, a screw portion 1b41 is formed on the outer peripheral wall surface of the small-diameter cylindrical portion 1b4, and the slider 12 is engaged with the screw portion 1b41. By adjusting the position of the slider 12, the spring 11 with respect to the moving member 3 is adjusted. The pressing force is adjusted. And to adjust the pressing force of the spring 11,
On the downstream side surface of the slider 12, a plurality of holes 12a are formed in an annular shape at regular intervals, and the large diameter cylindrical portion 1b2 and the intermediate cylindrical portion 1b are formed.
3, A window 1b51 for communicating the partition wall 1b5 in an arc shape corresponding to the hole 12a with the partition wall 1b5 formed at each downstream end of the small diameter cylindrical portion 1b4.
Has been set (see FIG. 3). For adjustment, a jig (not shown) is fitted into the hole 12a through the window 1b51, and the slider 1
This is performed by rotating 2 to move the slider 12 forward and backward along the screw portion 1b41. An O-ring 13 for fixing the position of the slider 12 is set between the slider 12 and the intermediate cylindrical portion 1b3.

An intake air temperature sensor 14 is set on the rib 1b1,
A metal cap 14 that is integrally molded so that the spherical tip projects toward the upstream side when molding the housing 1b.
It is housed in a and is connected to the lead wire 14b.

Further, a connector 1b6 is formed on the housing 1b, and a plurality of conductor pins 15 for taking out signals are provided on the pin holding member 15a so that one end thereof projects into the connector 1b6.
At the same time, they are fixed by a mold via the inside of the rib 1b1. The other end of the pin 15 is connected to the lead wire 14b of the intake air temperature sensor 14 and detects the displacement amount of the moving member 3 described later,
It is also connected to a sensor (potentiometer 18) for converting into an electric signal. The pin 15 is first molded and fixed to a pin holding member 15a made of resin in an L-shape, and the pin 15 held by the pin holding member 15a is fixed by molding at the time of molding the housing 1b or the like so as to interpose the inside of the rib 1b1. .

The lead wire 15b of the intake air temperature sensor 14 is the intake air temperature sensor 1
A rubber-made lead wire holding member 14b1 is provided corresponding to the rib 1b1 so as not to play in the rib 1b1 set at 4. Further, the lead wire 14b is formed on the downstream side surface of the partition wall 1b5 so as to be integrally formed with the housing 1b when the housing 1b is formed.
It is guided by a groove 16 formed between 7 and the annular raised portion 1b8 and connected to one end of the pin 15. A part of the lead wire holding member 14b1 is fitted in the raised portion 1b8, and is guided to the groove 16 portion by the lead wire holding member 14b1.

Further, the stud bolt 17 is attached to the partition wall 1b5 at the tip thereof.
Molded so as to project to the downstream side surface of b5, a metal potentiometer holder 19 holding a potentiometer 18 is fixed to this stud halt 17 via a plurality of washers 21 by a nut 20 (Fig. 4). reference).

The potentiometer 18 is held on a holder 19 so as to be parallel to the axis 3d of the moving member 3. By the way, the holding of the potentiometer 18 on the holder 19 is performed by setting a double-sided tape 18a between the potentiometer 18 and the holder 19 so that the potentiometer 18 and the holder 19 are bonded together.
It is held by three protrusions 19a formed on 19 and a U-shaped leaf spring 22 fitted in a hole 19b formed at a position facing the protrusion 19a. The potentiometer 18 is pressed in the direction of the protrusion 19a to hold it in the horizontal direction, and the push-back portion 22a of the leaf spring 22 holds it in the vertical direction.

A predetermined circuit pattern is set on the surface of the potentiometer 18, and this circuit pattern is electrically connected to one end of the pin 15.

A slider 24, to which a brush 23 that slides in accordance with the displacement of the shaft 3d on the circuit pattern of the potentiometer 18, that is, the movement of the moving member 3 is fixed, is provided at the end of the shaft 3d that penetrates the bearing 8. (See FIG. 4). And the axis
The end portion of the portion of the 3d moving member 3 that penetrates the bearing 8 when fully closed and projects to the downstream side is threaded and double chamfered, and the slider 24 follows the double chamfer. The stopper plate 25 set on the upstream side of the slider 24 of the shaft 3d, the spring 26 set between the stopper plate 25 and the slider 24, and the nut 27 set on the downstream side of the shaft 3d. This allows the position of the slider 24 on the axis 3d to be adjusted.

Since the brush 23 of the slider 24 is slid on the circuit pattern of the potentiometer 18 to detect the movement amount of the moving member 3 as described above, it is necessary to prevent the moving member 3 from rotating with respect to the central axis. is there. Therefore, the end of the rivet 28 provided by fitting or screwing to the tip of the projection 7a extending upstream from the end of the retainer 7 holding the bearings 6a, 6b is inside the inner cylinder 3c of the moving member 3. Guide groove 3c1 formed on the peripheral wall in a straight line along the moving direction
By being configured to slide inside, rotation of the moving member 3 is prevented.

The housing 1c is integrally formed with a cover 1c1 that houses the potentiometer 18 and the like set on the downstream side of the partition wall 1b5 and a rib 1c2 that supports the cover 1c1. The cover 1c1 has a bell shape with an open upstream side, and is shaped so as not to disturb the flow of passing air as much as possible. The upstream opening 3 of the cover 1c1 is located in the housing 1b.
It has an inner diameter that is substantially the same as the outer diameter of the raised portion 1b8 formed on the side, a step portion 1c11 is formed on the inner diameter side of the opening end, and the raised portion 1b8 and the opening portion of the cover 1c1 An annular space is provided in which an O-ring 29 for securing a seal is set. The rib 1c2 extends in the central axis direction of the housing 1c and is smoothly connected to the outer peripheral surface of the cover 1c1. The rib 1c2 is the rib 1 set on the housing 1b.
Four ribs are formed corresponding to b1 and ribs of the housing 1b
The downstream side surface of 1b1 and the upstream side surface of the rib 1c2 of the housing 1c are aligned so that the cross-sectional shape of the assembly of both ribs 1b1 and 1c2 is streamlined (see FIG. 5) to maximize the air flow. I try not to disturb.

Therefore, the cover 1c1 is configured with a potentiometer chamber 30 in which the potentiometer 18 and the like are housed, and in the potentiometer chamber 30, the end of the shaft 3d having the slider 24 provided with the brush 23 that slides on the circuit pattern of the potentiometer 18. The part is displaced along the central axis in accordance with the movement of the moving member 3. Then, one end of the pin 15, that is, the end of the intake temperature sensor 14 on the side electrically connected to the lead wire 14b and the potentiometer 18 projects into the potentiometer chamber 30.

In order to improve the accuracy of assembly of the housing 1b and the housing 1c in the rotational direction, a protrusion 1c3 is set on one of the ribs 1c2 of the housing 1c on the end surface side of the rib 1c2 that is connected to the housing 1c on the side of the housing 1c. And also housing 1b
The groove 1b9 corresponding to the protrusion 1c3 is connected to the housing 1c on one of the ribs 1b1 of the housing 1b.
The rib 1b1 is formed along the inner peripheral wall surface.

In the air flow rate measuring device having the above configuration, when a predetermined air flow rate Q flows in the air flow path 2, a pressure difference is generated in the upstream and downstream of the moving member 3, and the moving member 3 resists the pressing force of the spring 11. , Linearly moving in the downstream direction from the fully closed position regulated by the fully closed stopper 1a2 to widen the air passage area between the outer edge portion 3a of the moving member 3 and the inner peripheral wall surface 1a1 of the housing 1a,
The moving member 3 moves to a position where the pressure received by the upstream side surface of the moving member 3 which is the air passage area required for the air flow rate Q to flow and the pressing force of the spring 11 are balanced. In accordance with the movement of the moving member 3, the shaft 3d connected to the moving member 3 is displaced downstream on the central axis by the distance moved by the moving member 3, and the downstream end of the shaft 3d by this displacement amount χ. The brush 23 of the slider 24 set in the section is the potentiometer 18
The displacement amount χ is converted into an electric signal by the potentiometer 18 and is output to the outside via the pin 15. Here, the air flow rate Q and the air passage area have a predetermined functional relationship, and a predetermined functional relationship is established between the air passage area and the moving amount of the moving member 3, that is, the moving distance of the moving member 3. Since the peripheral wall surface 1a1 of the housing 1a is adjusted, the potentiometer 18
The electric signal converted by means of represents the air flow rate Q.

Further, in the above configuration, the ventilation of air between the inside and outside of the air damper chamber 10 is performed by the outer cylinder 3b of the moving member 3 and the housing.
Since it is only the clearance portion with the large cylindrical portion 1b2 fixedly set to 1b, the moving member 3 due to the pulsation of the air flow
Of the moving member 3 is suppressed and the fluctuation of the moving member 3 is stabilized against the stepwise change of the air flow rate.
Behaviors such as excessive overshoot of are suppressed.

Therefore, according to the above configuration, since the movement of the moving member 3 is linear and parallel to the air flow in the air flow path 2, the pressure receiving area of the moving member 3 does not change even if the flow rate changes. Therefore, it is extremely easy to set the movement amount of the moving member 3 from the low flow rate region to the high flow rate region, that is, the change in the displacement amount of the shaft 3d to be uniform, and it is constant regardless of the change in the flow rate state. Measurement accuracy can be obtained.

Further, the displacement amount of the shaft 3d connected to the damper mechanism and the moving member 3 for suppressing vibration due to pulsation of the air flow of the moving member 3 and excessive overshoot at the time of sudden change of the air flow rate is converted into an electric signal. Since the potentiometer 18 is set in the flow path pipe 1, it can be made sufficiently smaller and more compact than the vane type, so that the mountability on the vehicle is improved.

Further, in the above configuration, the inner peripheral wall surface of each housing 1a, 1b, 1c (particularly the inner peripheral wall surface 1a1 of the housing 1a), the outer cylinder 3b for forming the moving member 3 and the air damper chamber 10, and the large diameter cylindrical portion 1b2. Has a circular cross-sectional shape, it is possible to secure sufficient dimensional accuracy by molding as compared with a shape such as a prism, so that additional work after molding is unnecessary and the number of manufacturing steps can be reduced.

Further, in the above configuration, since the assembly of the ribs 1b1 and 1c2 of the housings 1b and 1c is formed in a streamline shape, the ribs 1b1 and 1c2 are sufficiently suppressed from disturbing the air flow.

Further, in the above configuration, since the potentiometer 18 is housed in the potentiometer chamber 30 by the cover 1c1 so that the air flow does not come into direct contact with the potentiometer 18, foreign matter in the air, adhesion of moisture, etc., to the potentiometer 18 does not occur. In particular, in the above embodiment mounted on the engine, the fuel, oil, carbon, etc. from the engine are prevented from adhering to the potentiometer 18, and the change in measurement accuracy and durability is prevented and the long-term Thus, the initial characteristics can be sufficiently maintained.

By the way, in the above configuration, the outer cylinder 3b of the moving member 3 is set to be fitted inside the large-diameter cylindrical portion 1b2 with a minute gap. This is because the negative pressure generated by the moving member 3 is sufficiently applied to the inside of the air damper chamber 10 through the minute gap, which will be described with reference to the explanatory views (FIGS. 8 to 11). (Note that in FIGS. 8 to 11, the negative pressure region N
Is indicated by a dot).

In the embodiment of the present invention, air is discharged from the damper chamber 10 to the air flow path 2 through a discharge opening 10a having a minute gap opening in the air passage 2.

If the outer cylinder 3b is set as a comparative example such that the large-diameter cylindrical portion 1b2 is fitted into the outer-cylinder 3b on the outside of the large-diameter cylindrical portion 1b2 via a minute gap, in this comparative example, Since the minute gap is formed between the outer outer cylinder 3b and the inner large-diameter cylindrical portion 1b2, the discharge opening 10a is on the downstream tip side of the outer cylinder 3b, and depending on the movement of the moving member 3 to the downstream side. The discharge opening 10a comes to be displaced (FIGS. 10 and 11).

On the other hand, whether in such a comparative example or the above-mentioned embodiment,
In the pressure state on the downstream side of the outer edge portion 3a of the moving member 3, the displacement amount of the moving member 3 is small when the air flow rate is relatively small, so the outer edge portion 3a of the moving member 3 and the inner peripheral wall surface 1a of the housing 1a.
Although the air passage area due to 1 is small, and the entire downstream side from the outer edge portion 3a is in the negative pressure region (Figs. 8 and 10), the air passage area becomes large when the air flow rate is high, so The generated region is limited only to the immediately downstream portion of the outer edge portion 3a, and the pressure is restored to a pressure state substantially the same as the upstream side pressure of the moving member 3 in the downstream region slightly apart from the moving member 3 (9th embodiment). (Fig. 11, Fig. 11).

Therefore, in the comparative example, when the tip of the outer cylinder 3b is displaced to the area where this pressure is restored (Fig. 11), this pressure is applied to the air damper chamber 10 through the minute gap, and the pressure of the air damper chamber 10 body and the moving member. The pressure in the air damper chamber 10 becomes almost equilibrium with the pressure on the upstream side of 3 and the air in the air damper chamber 10 and the large-diameter cylindrical portion 1b.
Even if the air flow rate increases further, the moving member 3 cannot move, and measurement becomes impossible in a high air flow rate state.

However, in the configuration of the above-described embodiment, the outer cylinder 3b is fitted inside the large-diameter cylindrical portion 1b2, and the outer cylinder 3 inside is fitted in the minute gap.
Since the discharge opening 10a is formed between b and the large-diameter cylindrical portion 1b2 on the outer side, the discharge opening 10a is fixed at the upstream tip side of the large-diameter cylindrical portion 1b2. Therefore, when the moving member 3 moves to the downstream side as the air flow rate increases, the outer edge portion 3a of the moving member 3 and the large-diameter cylindrical portion.
The discharge opening 10a on the upstream front end side of 1b2 approaches.

On the other hand, although the air passage area formed by the outer edge portion 3a and the inner peripheral wall surface 1a1 increases with the movement of the moving member 3 to the downstream side, the outer edge portion 3a generates a negative pressure exceeding the pressure increment to be restored. Therefore, the discharge opening 10a is always located in the negative pressure region N generated at the outer edge portion 3a of the moving member 3 regardless of the air flow rate (FIG. 9).

If the moving member 3 is not provided with the outer edge portion 3a protruding like an eaves unlike the above-described embodiment, negative pressure cannot be generated on the downstream side of the moving member 3, that is, in the air damper chamber 10. Since this air does not escape to the air flow path 2, the movement of the moving member 3 is hindered by the air present in the air damper chamber 10. Therefore, the brush cannot be displaced on the circuit pattern of the potentiometer, and the measurement becomes impossible.

However, in the above embodiment, since the negative pressure by the moving member 3 is always introduced into the air damper chamber 10 in a sufficient and stable state, the moving member 3 is changed from the low air flow rate state to the high air flow rate state. The characteristic of the amount of movement with respect to the flow rate change can be sufficiently obtained.

FIG. 6 shows another embodiment of the present invention, in which the same parts as those in the above embodiment are designated by the same reference numerals and the description thereof is omitted.

In this embodiment, the fully closed stopper 31 that regulates the fully closed position of the moving member 3 is fitted into the stopper plate 25 fixed to the shaft 3d on the downstream side of the bearing 8 of the shaft 3d, and the fully closed stopper 31 is made of an elastic material. It consists of The end surface of the bearing 8 on the downstream side of the bearing cage 7 serves as a stop surface.

With this configuration, the flow of the air hitting the upstream side surface of the moving member 3 can be obtained smoothly, the movement of the moving member 3 can be stabilized, and the pressure loss of the air flow can be reduced.

The fully closed stopper 31 may be fixed to the shaft 3d on the upstream side of the stopper plate 25 instead of being fitted into the stopper plate 25. Further, if the fully closed stopper 31 is fixed so as to be movable back and forth with respect to the shaft 3d, the fully closed position of the moving member 3 can be finely adjusted.

FIG. 7 shows a main part of another embodiment of the present invention, and shows a clearance portion between the outer cylinder 3b of the moving member 3 and the large diameter cylindrical portion 1b2 of the housing 1b.
In this configuration, a portion of a predetermined width which faces the inner peripheral wall surface of the large-diameter cylindrical portion 1b2 when the moving member 3 on the outer peripheral wall surface on the downstream side of the outer cylinder 3b is in the fully closed state is larger than the outer peripheral wall surface of the outer cylinder 3b. Diameter cylindrical part 1b
The clearance surface 32 is used to set the clearance between the inner peripheral wall surface and the inner peripheral wall surface 2. That is, the outer cylinder 3b having a predetermined width on the outer peripheral wall surface on the downstream side of the outer cylinder 3b forming the clearance surface 32.
The outer diameter of the outer peripheral wall is larger than that of the other outer peripheral wall, and only the clearance surface 32 is formed with sufficiently higher dimensional accuracy than the other outer peripheral wall.

With this configuration, it is possible to reduce the clearance between the outer cylinder 3b and the large-diameter cylindrical portion 1b2, which determines the damping characteristics of this device, and the guaranteed range of the dimensional accuracy of the outer cylinder 3b. Is very easy to obtain. Further, even if foreign matter in the air enters between the intermediate cylinder 3b and the large-diameter cylindrical portion 1b2, the clearance surface 32
Since the width of the outer cylinder is sufficiently smaller than the size of the outer cylinder 3b, the foreign matter that has entered is easily removed according to the fluctuation of the outer cylinder 3b, and the movement of the moving member 3 may be impaired due to the foreign matter being caught. The sex is extremely low.

The clearance surface 32 may be set on the large diameter cylindrical portion 1b2 side.

Further, in the above embodiment, the potentiometer 18 was used to convert the displacement amount of the shaft 3d into an electric signal, but another sensor may be used as long as it can convert the displacement amount of the shaft 3d into an electric signal. Alternatively, for example, a differential transformer or an optical non-contact displacement detection sensor can be used.

Further, although the above-mentioned embodiment describes the case where the air flow rate is measured by mounting on the automobile engine, the measuring apparatus of the present invention can measure other gas flow rates.

〔The invention's effect〕

As described above, according to the present invention, the gas flow path through which the measured gas flows in the axial direction, and the gas flow path in a state where the gas can be moved linearly along the flow direction of the measured gas A flow member formed inside and a moving member set therein, and having a flow passage cross-sectional area increasing along the flow direction of the gas to be measured at least in the moving range of the moving member. A channel pipe, an axis extending along the flow direction of the gas to be measured from the moving member, fixedly set in the gas flow channel with the flow channel tube, and moving the axis according to the movement of the moving member. A bearing that supports the movable member in a possible state, a pressing member that exerts a pressing force on the moving member in a direction opposite to the flow direction of the gas to be measured, a conversion unit that converts the displacement amount of the shaft into an electric signal, The moving member closes one end and opens the other end. A first cylinder extending along the flow direction of the gas to be measured, fixedly set in the gas flow path with the flow path tube, closed at one end and open at the other end, and the first cylinder is Since the gas flow rate measuring device is provided with the second cylinder fitted inside through the minute gap, the pressure receiving area of the moving member is constant regardless of the flow rate of the gas to be measured. Therefore, the degree of change in the displacement of the shaft extending from the moving member can be extremely easily set to be uniform from the low flow rate range to the high flow rate range,
There is an excellent effect that a constant measurement accuracy can be ensured regardless of the change of the flow rate state, and the movement of the moving member causes the first cylinder to move the second cylinder through the minute gap to the second cylinder. Since it is displaced along the cylinder, the damping function acts on the moving member due to the configuration of the first cylinder and the second cylinder, and the vibration due to the pulsation of the gas flow of the moving member and the gas flow rate. It is possible to suppress excessive overshoot and the like due to a sudden change in, and since this configuration is set in the gas flow path,
There is also an excellent effect that the device can be made small and compact.

Furthermore, since the first cylinder is provided in the second cylinder, the first cylinder and the second cylinder are fixed from the tip of the second cylinder fixedly set in the flow path pipe. The pressure is introduced into the space formed by the cylinder and the moving member approaches the tip side of the second cylinder as the gas flow rate increases, so that the tip of the second cylinder is moved to the moving member. Therefore, the negative pressure generated by the moving member is always sufficiently and stable in the space formed by the first cylinder and the second cylinder. Since it is introduced, there is also an effect that the characteristics of the moving amount of the gas to be measured against the flow rate change of the moving member can be sufficiently ensured from the low flow state to the high flow state.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an air flow rate measuring device showing an embodiment of the present invention, FIG. 2 is a view in the direction of arrow A of the configuration shown in FIG. 1, and FIG. 3 is a housing 1c having the configuration shown in FIG. 1 removed. B in the closed state
FIG. 4 is a partial cross-sectional view taken along the line CC of the structure shown in FIG. 1, FIG. 5 is a cross-sectional view taken along line D-D of FIG. 4, and FIGS. It is sectional drawing which shows the Example of. FIG. 8 is an explanatory view showing a pressure state at a low flow rate according to the embodiment of the present invention,
FIG. 9 is an explanatory view showing a pressure state at a high flow rate of the embodiment of the present invention, FIG. 10 is an explanatory view showing a pressure state at a low flow rate of the comparative example, and FIG. 11 is a comparative example at a high flow rate. It is explanatory drawing showing a pressure state. 1 ... flow path tube, 1a, 1b, 1c ... housing, 2 ... air flow path,
3 ... Moving member, 3b ... Outer cylinder, 3d ... Shaft, 8 ... Bearing, 10 ...
… Air damper chamber, 11 …… Spring, 18 …… Potentiometer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Matsuura 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Akira Muramatsu 1-1-1-1 Showa town, Kariya city, Aichi prefecture Nidec Corporation Co., Ltd. (72) Inventor Rei Nagasaka 1-1, Showa-cho, Kariya city, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor, Toshio Tanahashi 1-1-Chome, Showa town, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. ( 56) References Japanese Unexamined Patent Publication No. 53-100271 (JP, A) Actually opened 57-72118 (JP, U) Actually opened 57-115146 (JP, U) JP-B 28-6336 (JP, B1)

Claims (4)

[Claims] 1. An intake air amount measuring device for an engine for measuring an intake air amount of an engine, wherein the intake air amount measuring device is provided in a part of an intake pipe of the engine, and allows the intake air to flow in an axial direction thereof. A flow channel pipe formed so that its flow channel cross-sectional area increases along the flow direction, and a center located at the downstream side of the predetermined range of the flow channel pipe and supported at substantially the center of the flow channel pipe. A member, provided in the flow path pipe with the predetermined range on the upstream side of the central member as a movement range, and supported by the central member in a linearly movable state along the flow direction of the intake air, A moving member that is displaced toward the downstream side in accordance with the amount of intake air from a state where the inside of the flow path pipe is substantially closed; a pressing member that exerts a pressing force on the moving member in a direction opposite to the flow direction of the intake air; Moving part Of the displacement of the intake air to an electric signal, the moving member is provided with a first cylinder (3b) extending along the flow direction of the intake air, and the central member is provided with a flow of the intake air. An air damper chamber extending in the direction, the air damper chamber being fitted to the outside of the first cylinder with a minute gap and suppressing the abrupt movement of the moving member by the air pressure inside the both cylinders. And a second cylinder (1b2) that forms a space between the first cylinder and the second cylinder when the moving member moves to the downstream side of the intake air. An intake air amount measuring device for an engine, characterized in that an outer edge portion (3a) projecting in an eaves-like shape is provided on an upstream side of an inlet to the gap. 2. The moving member is provided so as to penetrate the central member along the flow direction of intake air, and is supported by the central member so as to be linearly movable along the flow direction of intake air. The intake air amount measuring device for an engine according to claim 1, further comprising a shaft. 3. The conversion means is provided on the downstream side of the central member, and converts the displacement amount of the shaft penetrating the central member into an electric signal.
Intake air amount measuring device for an engine according to paragraph. 4. The intake air amount measuring apparatus for an engine according to claim 3, wherein the central member includes a cover that covers the converting means.