JP5409560B2 - Thermal flow sensor - Google Patents

Description

  The present invention relates to a thermal flow sensor provided with a sensor element using a heating resistor as a detection unit to detect a flow rate of air or the like flowing through an intake passage of an in-vehicle internal combustion engine, and in particular, to improve flow measurement accuracy. The present invention relates to a thermal flow sensor.

  As a sensor for detecting a flow rate of an internal combustion engine mounted on an automobile or the like, a thermal type flow rate sensor that can directly measure a mass flow rate has become mainstream.

  In the field of automobile engine control, a flow sensor using a sensor element in which a flow rate of air supplied to an engine is manufactured on a semiconductor substrate such as silicon (SI) using a micromachining technique has been proposed. Such a sensor element can be placed in a stable flow in the flow range required for the engine to accurately detect the flow rate, improve accuracy due to manufacturing variations between solids in mass production, It is a problem to maintain the initial accuracy even in the use of the period.

  In response to such a problem, the thermal flow sensor is disposed as a sensor module in a main passage through which a fluid flows, and the sensor module is formed with a sub-passage that guides the fluid to the sensor element. For example, there is an invention described in Patent Document 1 below. The configuration described in this document includes a base member that fixes a circuit board and a housing member that is fitted to the base member, and a sub-passage is formed by bonding and fitting the base member and the housing member. A press-fitting pin and a press-fitting hole for inserting the press-fitting pin are provided in either of the base member and the housing member, and are disposed in the vicinity of the metal wire, thereby minimizing the relative thermal displacement between the housing member and the base member. Reduces wire degradation.

JP 2002-62174 A

  The sub-passage for arranging the sensor element is formed by two or more parts constituting the sensor module. Constituent members include a housing member, a base member, a cover member, and the like, and these parts are joined with an adhesive to form a sub-passage that guides fluid. When these members are fitted to each other, a press-fit pin and a press-fit pin receiving hole are formed as described in Patent Document 1.

  The parts that make up the sub-passage are made of the same material and have the same linear expansion coefficient and are effective against changes due to environmental temperature. In this case, it is desirable to use a resin material for all of them.

  However, if all the component parts are made of a resin material, there is a problem that a simple concave receiving hole cannot provide a sufficient holding force during fitting.

  When the press-fit pin is made of resin and the receiving hole is also made of a resin material, the press-in force collapses the pin, but the receiving hole is also deformed. Such deformation does not occur when the receiving hole is made of a metal material. If this holding force is insufficient, the initial fitting state cannot be maintained at the time of heat bonding, and the fitting state of the members constituting the sub-passage varies at the time of manufacture. Therefore, the effective cross-sectional area of the sub-passage where the sensor element is arranged will vary, and even if the flow of the main passage is constant, the flow velocity in the sub-passage will be different for each individual sensor module, Manufacturing variation of the flow sensor module occurs.

  However, the thermal flow sensor described in Patent Document 1 does not consider the variation in the effective cross-sectional area of the secondary passage due to the variation in fitting of the two members as described above.

  Therefore, the present invention has been made to solve the above-described conventional problems, and the object of the present invention is to reduce the variation in joining of the sub-passage where the sensor elements are arranged, and to solidify the flow sensor module. An object of the present invention is to provide a thermal flow sensor with reduced manufacturing variations.

  In order to achieve the above object, in the thermal flow sensor according to the present invention, the auxiliary passage is formed of two or more resin members, and a press-fit pin with a crushing margin is formed on one of the resin members, The other resin member is formed with a press-fit pin receiving hole for fitting with the resin member on which the press-fit pin is formed. The receiving hole is composed of two or more holes having different inner diameters, and the inner diameter is small. L1 <L2 where L1 is the length in the depth direction of the hole and L2 is the length of the area where the press-fit pin is crushed. With this configuration, the press-fit pin comes into contact with a hole having a small inner diameter when inserted, and the tip of the press-fit pin does not come into contact with the resin base member after press-fitting. When the adhesive is heat-cured in this state, the shape of the crushing margin is slightly recovered at the tip of the press-fit pin, and a stronger holding force is generated. As a result, the vertical positional relationship between the resin housing and the resin base is maintained during thermosetting, so that the accuracy after adhesive curing can be improved, and therefore the effective cross-sectional area of the sub-passage between the solids in mass production. Can be reduced.

  According to the present invention, in the process of forming the sub-passage in which the sensor element is arranged, the press-fit pin is inserted into the receiving hole, so that the joining accuracy in the surface direction of the resin housing member and the resin base member can be improved. it can. Further, by obtaining a holding force that does not change the bonding state during adhesive curing, the bonding accuracy in the height direction can be improved. Thereby, the sensor module which reduced the dispersion | variation between solids in mass production can be provided.

  Furthermore, even in the complicated sub-passage that changes the direction of flow, by improving the joining accuracy, variation between solids in mass production is reduced, and sensor elements are destroyed by dust, fouling substances, and water, and characteristics are changed. Can be provided.

The cross-sectional view which shows the flow sensor of embodiment of this invention. AA sectional drawing of FIG. The enlarged view of the press-fit pin of one Embodiment of this invention. BB sectional drawing of FIG. The enlarged view of the receiving hole of one Embodiment of this invention. CC sectional drawing of FIG. The enlarged view in which the press-fit pin of one Embodiment of this invention was inserted in the receiving hole. The enlarged view of the receiving hole of one Embodiment of this invention. BB sectional drawing of FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a partial cross-sectional view showing a state in which a flow sensor 1 according to an embodiment of the present invention is installed in a main passage, and FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 shows a sectional view of the press-fit pin of the resin housing member and the receiving hole of the resin base member. FIG. 4 is a cross-sectional view taken along the line BB in FIG.

  In general, the semiconductor type sensor element 2 includes a thin film portion formed on a silicon substrate and a heating resistor 3 formed on the thin film portion. The material of the heating resistor 3 is formed of single crystal silicon doped with impurities, polycrystalline silicon, a metal material, or the like. The substrate may be formed using a ceramic or metal material.

  The sensor element 2 formed on a semiconductor substrate such as a silicon substrate is adhesively mounted on a multilayer ceramic support 17 formed of a plurality of ceramic substrates. The multilayer ceramic support 17 forms a rectangular depression 18 using a part of the layers, and the sensor element 2 is mounted in the depression 18. By being mounted in the depression 18 in this way, the flow is stable and flows on the surface of the sensor element 2, so that a stable flow rate signal can be obtained. The multilayer ceramic support 17 forms a circuit conductor in its interior, and an adjustment LSI 19 and a chip component 24 necessary for driving the sensor element 2 are mounted on the surface. The sensor element 2 is electrically connected to a circuit board mounted on the multilayer ceramic support 17 by wire bonding. The adjustment LSI 19 is also electrically connected to the multilayer ceramic support 17 by wire bonding. Thereby, since a support body and a circuit can be integrated, adhesive mounting can be decreased and reliability can be improved. The multilayer ceramic support 17 on which the sensor element is mounted is mounted on the resin base member 4 with a silicone-based thermosetting adhesive 6. The resin base member and the resin housing member are joined to form a secondary passage, and the sensor element is disposed in the secondary passage.

  Here, a throttle portion 13 for reducing the flow is formed at a position on the sensor element 2 of the resin housing member 14. The throttle unit 13 can obtain a state in which the disturbance of the fluid is reduced on the sensor element 2, and stable flow rate measurement is possible.

  However, if the alignment accuracy in the surface direction of the sub-passage 7 is insufficient, manufacturing variations occur in the positions of the throttle portion 13 and the sensor element 2 formed in the resin housing member 14, and this variation causes the flow rate measurement. It affects the error.

  Therefore, in the present embodiment, as shown in FIG. 2, the press-fit pin 21 shown in FIGS. 3 and 4 is provided in the resin housing member 14. FIG. 5 shows the shape of the receiving hole 20. The receiving hole 20 is provided in the resin base member 4, and the press-fit pin 21 of the resin housing member 14 matches the receiving hole 20 of the resin base member 4. In this manner, the resin housing member 14 is fitted.

  Further, when the accuracy in the height direction of the resin base member 4 and the resin housing member 14 is insufficient, variations in the cross-sectional area of the sub passage 7 and variations in the distance between the throttle portion 13 and the sensor element 2 occur.

  However, by installing the two press-fit pins 21 and the receiving holes 20 in the sub-passage 7 region, positional accuracy in the surface direction can be obtained by the press-fit pins and the receiving holes.

  Next, the shape of the press-fit pin 21 and the receiving hole 20 will be described with reference to FIGS. 6 is a cross-sectional view taken along the line C-C in FIG. 5, and FIG. 7 is a view showing a state where the press-fit pin 21 is inserted into the receiving hole 20.

  As shown in FIG. 6, the receiving hole 20 is a two-stage hole having different inner diameters. As shown in FIG. 7, when the length of the press-fit pin 21 is L2, the receive hole that the press-fit pin 21 comes into contact with. The depth of 20 is L1, and L2> L1. Thus, since the tip of the press-fit pin 21 is opened, the crushing allowance 22 that has been crushed at the time of insertion is released slightly, so that it slightly recovers and generates a holding force. Thereby, since the positional relationship in the vertical direction between the resin housing member 14 and the resin base member 4 is kept constant during thermosetting, the accuracy after adhesive curing can be improved, and the secondary passage between solids in mass production It is possible to reduce the variation in the effective area of 7.

  Further, when the thickness of the resin base member 4 is L3, the length L2 of the press-fit pin 21 is configured to satisfy L2 <L3, and the tip of the press-fit pin 21 does not protrude from the resin base member 4. It has become. With this configuration, the tip of the press-fit pin 21 does not jump out from the surface opposite to the resin-base joining, so that stable transportation in the manufacturing process and transportation after the manufacturing can be performed.

  Further, as shown in FIG. 8, a depression 23 is formed around the press-fit pin 21 so that the surface on which the press-fit pin 21 is formed is at a position lower than the surrounding surface. With this configuration, when the resin housing member 14 is press-fitted into the resin base 4, the crushing allowance 22 of the press-fit pin 21 is crushed. Since the crushing allowance of the crushing pin 21 is accumulated in the recess 23, the resin housing When the member 14 and the resin base 4 are fitted, it is possible to prevent the fitting accuracy from being deteriorated by entering the gap.

  Next, another embodiment will be described.

  The resin housing member 14 is joined to the resin base member 4 by heating. Silicone gel is injected into the area of the adjustment LSI 19 for protection. An epoxy thermosetting adhesive is applied to the resin housing member 14, and the cover member 25 is mounted. The cover member 25 is joined by heating to form a sensor module.

  Here, the flow direction of the fluid flowing in from the inlet is changed by 180 degrees between the sub-passage 7 shown in FIG. With this configuration, dust, fouling substances, water, and the like contained in the fluid collide with the wall of the sub-passage due to inertial force and lose kinetic energy. Thereby, the direct collision with a sensor element can be reduced significantly, and reliability can be improved.

  The flow in the sub-passage is divided by the multilayer ceramic support 17 into a flow on the front surface sensor element 2 side and a flow on the back surface. Here, by adopting a configuration in which the flow velocity on the back surface side is faster than the flow velocity on the front surface side, dust, fouling substances, water, etc. contained in the fluid mainly flow into the back surface side due to inertial force. Therefore, the direct collision with the sensor element 2 can be greatly reduced, and the reliability can be improved. However, with this configuration, the passage width in the vicinity of the sensor element is ½ or less compared to the inflow port, and a throttle portion is formed on the upper surface of the sensor element. Therefore, the distance between the sensor element 2 and the diaphragm 13 is very narrow.

  Accordingly, the press-fit pins 21 and the receiving holes 20 in the present embodiment can maintain the positional accuracy of the resin housing member 14 and the resin base member 4 in the vertical direction. That is, the distance between the sensor element 2 and the diaphragm 13 is also configured with high accuracy.

  Furthermore, other preferred embodiments are described.

  The sub-passage 7 changes the flow direction from the inlet of the flow rate to the position of the sensor element 2 or changes the flow direction so as to generate an inertia effect, thereby causing contamination of dust or carbon contained in the air flow rate. The material is configured not to directly collide with the sensor element 2. With this configuration, even when used for a long period of time, it is possible to prevent the detection element from being deteriorated or broken due to contamination. However, such a sub-passage 7 complicates the internal flow, so that it is difficult to suppress solid variation in mass production.

  Therefore, by applying the above-described configuration of the press-fit pin 21 and the receiving hole 20, it is possible to provide a highly accurate and reliable flow rate sensor.

  Furthermore, other preferred embodiments are described.

  Further, at the time of adhesive mounting, a plate-like flow rate sensor using the sensor element 2 manufactured using a micromachining technique on a semiconductor substrate is adhesively mounted on the plate-like multilayer ceramic support 17, and this multilayer ceramic support 17 is bonded and mounted on a resin base. Then, the resin housing member 14 is mounted by bonding. This adhesive mounting is all configured in one direction, for example, the vertical direction. The sensor element 2 manufactured using the micromachining technology has a small heat capacity, can respond to the flow rate at high speed, and the adhesive mounting that is laminated in one direction facilitates the manufacture. Can do. The plate-shaped multilayer ceramic support 17 is arranged near the center of the sub-passage, and the fluid flows to the front surface where the sensor element 2 is arranged and the rear surface where the sensor element 2 is not arranged. It is desirable to increase the flow rate. With this configuration, dust, fouling substances, and water introduced together with the fluid in the sub-passage mainly pass through the back side, and such substances hardly flow on the front side, thereby preventing collision with the sensor element 2. Can do. However, this laminated adhesive mounting adds all the tolerances and adhesive tolerances of each component, and divides the flow in the vicinity of the sensor element 2 into two. Therefore, the added tolerance is relative to the flow path width on the surface of the sensor element 2. Therefore, the balance between the flow velocity on the front surface side of the sensor element 2 and the flow velocity on the rear surface side of the sensor element 2 is lost, and the effect of allowing the dust, fouling substances, and water to pass through the back surface of the sensor element is reduced. It may happen.

  However, by applying the press-fit pin 21 and the receiving hole 20 described above, the vertical accuracy of the sub-passage 7 can be maintained, and a flow sensor that achieves both high-speed response, high reliability, and easy manufacturing can be obtained. .

  Furthermore, other preferred embodiments are described.

  The press-fit pin 21 and the receiving hole 20 are disposed in a region constituting a wall that constitutes the sub-passage 7 of the resin housing member 14 and the resin base member 4. The resin housing member 14 is formed by insert-molding a metal part that transmits an electrical signal, and the linear expansion coefficient of the metal part and the resin part is different. Therefore, when the adhesive 6 is thermally cured, the resin housing member 14 is caused by the difference in the linear expansion coefficient. In some cases, a force that causes a shift in the positional relationship between the resin 14 and the resin base member 4 is generated. In this case, if the press-fit pin 21 and the receiving hole 20 are arranged in a region where the auxiliary passage 7 is formed, even if such a force is generated between the resin housing member 14 and the resin base member 4, the auxiliary passage 7. This region is characterized in that the positional relationship in the vertical direction is maintained. Since the auxiliary passage 7 defines the flow rate at the position of the sensor element 2, the manufacturing accuracy of the auxiliary passage 7 affects the accuracy of the sensor module. Here, at the time of fitting, the press-fit pin 21 is inserted into the receiving hole 20 to determine the position of the sub-passage 7 in the surface direction. Further, since the resin housing member 14 and the resin base member 4 are held by the crushing allowance 22 of the press-fit pin 21, the position in the height direction is also determined, and the bonding state of the two members is maintained during bonding and curing. Can do. As a result, the two members can be bonded and cured with high precision both in the surface direction and in the height direction.

DESCRIPTION OF SYMBOLS 1 Flow rate sensor 2 Sensor element 3 Heating resistor 4 Resin base member 5 Recess 6 Adhesive 7 Sub-passage 8 Measurement passage part 9 Diaphragm 10 Main passage 12 Opening part 13 Restriction part 14 Resin housing member 15 Circuit board 16 Wire bonding 17 Lamination Ceramic support 18 Rectangular recess 19 Adjustment LSI
20 receiving hole 21 press-fit pin 22 crushing allowance 23 depression 24 on press-fit pin forming surface chip component 25 cover member

Claims (4)

In a flow sensor having a sub-passage that is arranged in an intake passage and takes in a part of an air flow flowing in the intake passage, and a sensor element that detects a fluid flow rate arranged in the sub-passage,
The sub passage is formed of two or more resin members,
One of the resin members is formed with a press-fit pin with a crushing margin,
On the other side of the resin member, a receiving hole for the press-fit pin for fitting with the resin member on which the press-fit pin is formed is formed.
The receiving hole is composed of two or more holes having different inner diameters,
A flow rate sensor characterized by L1 <L2, where L1 is a length in a depth direction of a hole having a small inner diameter, and L2 is a length of a region having a crushing margin of a press-fit pin. The flow sensor according to claim 1,
A flow rate sensor characterized in that L1 <L2 <L3, where L3 is a thickness of the resin member in which the receiving hole is formed. The flow sensor according to claim 1 or 2,
The resin member in which the press-fit pin is formed has a recess in a part thereof, and the press-fit pin is formed in the recess. The flow sensor according to any one of claims 1 to 3,
The flow rate sensor, wherein the press-fit pin and the receiving hole are formed in a region where the auxiliary passage is formed.

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