Pressure sensor and manufacturing method therefor

A pressure sensor comprises a sensor housing and a sensor header. The sensor housing includes a fastener adapted to be fastened to a pressure measurement target and a housing pathway extending through the fastener and adapted to guide a fluid flowing from the pressure measurement target. The sensor header includes a port pressed in and fixed to the housing pathway, a header pathway extending through the port and adapted to guide the fluid flowing from the housing pathway, and a diaphragm positioned at an end portion of the header pathway.

FIELD OF THE INVENTION

The present invention relates to a pressure sensor and, more particularly, to a pressure sensor including a sensor header pressed into a sensor housing.

BACKGROUND

A sensor, as is known in the art, senses or detects and measures a physical quantity of heat, light, temperature, pressure, or sound or a change therein. The sensor sends the corresponding information as a signal. A pressure sensor, for example, senses a pressure and transmits pressure information as a predetermined signal. Known pressure sensors, however, are difficult to manufacture.

SUMMARY

A pressure sensor comprises a sensor housing and a sensor header. The sensor housing includes a fastener adapted to be fastened to a pressure measurement target and a housing pathway extending through the fastener and adapted to guide a fluid flowing from the pressure measurement target. The sensor header includes a port pressed in and fixed to the housing pathway, a header pathway extending through the port and adapted to guide the fluid flowing from the housing pathway, and a diaphragm positioned at an end portion of the header pathway.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

A pressure sensor1according to an embodiment, as shown inFIGS. 1 and 2, may be fastened to a pressure measurement target to measure a pressure of a fluid flowing from the pressure measurement target and transmit the measured pressure to an external device. The pressure sensor1includes a sensor housing11, a sensor header12, a circuit board13, a connector14, a connecting terminal15, an inner O-ring16, and an outer O-ring17.

The sensor housing11, as shown inFIG. 2, includes a fastener111to be fastened to the pressure measurement target, and a housing pathway112shown inFIG. 4penetrating the fastener111to guide the fluid flowing from the pressure measurement target.

The sensor header12may be pressed in and fixed to the housing pathway112, as shown inFIG. 4. In an embodiment, the sensor housing11and the sensor header12may be coupled to each other in a press-in manner while being machined to be cut separately. The sensor header12is formed of a material having a higher yield stress than a material of the sensor housing11. A configuration and an assembling process of the sensor header12will be described in greater detail below with reference toFIGS. 3 and 4.

The circuit board13transmits the measured signal from the sensor header12to the external device through the connector14. The connector14transmits the signal received from the circuit board13to the external device. The connector14, as shown inFIG. 2, includes a connector housing141to be connected to the sensor housing11and a connection terminal142to be positioned in the connector housing141and electrically connected to the circuit board13.

The connecting terminal15, as shown inFIG. 4, is disposed between the circuit board13and the connection terminal142to electrically connect the circuit board13and the connection terminal142. The connecting terminal15has an elasticity in a direction perpendicular to the circuit board13. As shown in the embodiment ofFIG. 2, the connecting terminal15has a C-clip shape. By the above structure, even in a case in which there exists a manufacturing tolerance and an assembling tolerance of the circuit board13and/or the connection terminal142, an electrical contact state of the circuit board13and the connection terminal142may be stably secured.

The inner O-ring16, as shown inFIG. 4, is disposed between the connector housing141and the sensor housing11to maintain an airtightness between the connector housing141and the sensor housing11, thereby preventing an inflow of a foreign substance. In the shown embodiment, the inner O-ring16is disposed along an outer edge of the connector housing141and an inner edge of a portal of the sensor housing11.

The outer O-ring17is disposed in a circumferential direction around the fastener111of the connector housing141, as shown inFIGS. 1 and 4. The outer O-ring17may maintain an airtightness between the pressure measurement target and the sensor housing11, thereby preventing an inflow of a foreign substance.

As shown inFIGS. 3 and 4, the sensor header12is pressed in and fixed to the sensor housing11. The sensor header12and the sensor housing11may be formed of materials having different yield stresses, for example, metals having different yield stresses. In an embodiment, the sensor housing11may be formed of an aluminum alloy and the sensor header12may be formed of stainless steel having a higher yield stress than the aluminum alloy.

One of the sensor header12and the sensor housing11, the one formed of a material having a lower yield stress, is deformed during a process of pressing the sensor header12in the sensor housing11by applying a sufficient force thereto. A deformed portion of the sensor header12or the sensor housing11extends into an empty space of the other of the sensor header12and the sensor housing11formed of the material having a higher yield stress; the sensor header12and the sensor housing11are coupled and in close contact in shapes to be airtight without using a separate fastening element. That is, the sensor header12is coupled to and sealed with the sensor housing11without using a separate airtight device such as an O-ring. A volume may change slightly as the temperature changes and, consequently, a change in the airtightness level with respect to the temperature may be reduced. Further, the total number of parts constituting the pressure sensor1may be reduced, whereby the production cost may be reduced, and the manufacturing process may be simplified. In addition, an effect of a miscellaneous load generated during an assembling process on the pressure sensor1may be reduced.

The sensor header12, as shown inFIG. 3, includes a port121, a diaphragm122, a flange123, a connecting neck124, a header pathway125, and a strain gauge SG.

As shown inFIG. 3, the header pathway125penetrates the port121. One end of the header pathway125fluidly communicates with the housing pathway112, as shown inFIG. 4, to guide the fluid flowing from the housing pathway112, and an opposite end of the header pathway125is covered by the diaphragm122. The diaphragm122has a shape of a thin plate to be deformed by the fluid flowing thereinto.

The strain gauge SG, as shown inFIG. 3, is attached to one surface, for example, a top surface, of the diaphragm122. The strain gauge SG converts a deformation level of the diaphragm122into an electrical signal and transmit the electrical signal to the circuit board13. The strain gauge SG may be formed of, for example, a silicon material.

The port121is pressed in and fixed to the housing pathway112as shown inFIG. 4. In an embodiment, the port121is formed of a material having a higher yield stress than the material of the sensor housing11. The port121includes an insert1211, a press-in part1222, and a fixing groove1223as shown inFIG. 3.

As shown inFIGS. 3 and 4, the insert1211is inserted into the housing pathway112. A diameter d1of the insert1211is less than or equal to a diameter d6of the housing pathway112.

The press-in part1222is positioned behind the insert1211based on a direction in which the port121is inserted into the housing pathway112. The press-in part1222is pressed in the housing pathway112. A diameter d2of the press-in part1222is greater than the diameter d1of the insert1211and greater than the diameter d6of the housing pathway112. Further, a yield stress of a material of the press-in part1222is higher than a yield stress of a material of an inner end portion of the housing pathway112. The inner end portion of the housing pathway112is deformed while the press-in part1222is being pressed in the housing pathway112. A portion deformed, at the inner end portion of the housing pathway112, is a deformed portion112a.

The fixing groove1223is recessed between the insert1211and the press-in part1222as shown inFIG. 3. A minimum diameter of the fixing groove1223is less than the diameter d6of the housing pathway112. The deformed portion112aof the housing pathway112fills the fixing groove1223while the press-in part1222is being pressed in the housing pathway112, thereby preventing a separation of the port121from the housing pathway112.

The flange123, as shown inFIG. 3, is positioned between the port121and the diaphragm122, and has a diameter d4greater than the maximum diameter d2of the port121and a maximum diameter d3of the diaphragm122. In a plane perpendicular to a longitudinal direction of the housing pathway112and/or the header pathway125, a cross-sectional area of the flange123excluding the header pathway125is greater than a maximum cross-sectional area of the port121excluding the header pathway125. In an embodiment, the cross-sectional area of the flange123excluding the header pathway125may be at least two times greater than the maximum cross-sectional area of the port121excluding the header pathway125. For a mechanical stress generated in a vicinity of the press-in part1222when the press-in part1222is completely pressed in the housing pathway112, the flange123having a relatively great cross-sectional area and volume disperses the mechanical stress, reducing an effect of the mechanical stress on an output of the pressure sensor1.

The connecting neck124is disposed between the flange123and the diaphragm122and, as shown inFIG. 3, has a diameter less than the diameter d3of the diaphragm122and the maximum diameter d2of the port121. Although a portion of the mechanical stress is dispersed while passing through the flange123, the mechanical stress may be completely dispersed while deforming the connecting neck124before being transmitted to the diaphragm122. Hence, a miscellaneous load to be transmitted to the diaphragm122is blocked.

The sensor housing11, as shown inFIG. 4, includes a receiver113having a diameter d7greater than the diameter d6of the housing pathway112. The receiver113receives the flange123. The sensor housing11has a seat portion114positioned above the receiver113, the seat portion114having a greater diameter than the receiver113. The seat portion114provides a space in which the circuit board13is seated. The receiver113includes a bottom surface113aconnected to the housing pathway112and an inner circumferential surface113bto enclose a circumference of the bottom surface113a.

When the sensor header12is completely fastened to the sensor housing11as shown inFIG. 4, the flange123is spaced apart by a distance L1from the bottom surface113aof the receiver113. In an embodiment, the distance L1is 0.5 millimeters (mm). Although the sensor header12and the sensor housing11formed of different materials expand by heat with different degrees in response to a change in the peripheral temperature, interference of the flange123with the bottom surface113aof the receiver113may be prevented. Hence, by the above structure, transmission of an undesired mechanical stress to the diaphragm122due to a volume change caused by the change in the peripheral temperature of the pressure sensor1is prevented, improving a measuring accuracy of the pressure sensor1.

The diameter d7of the receiver113is a distance L2greater than the diameter of the flange123. When the sensor header12is completely fastened to the sensor housing11as shown inFIG. 4, the flange123is spaced apart by the distance L2from the inner circumferential surface113bof the receiver113. In an embodiment, the distance L2is 1 mm. By the above structure, although the sensor header12and the sensor housing11formed of different materials expand by heat with different degrees in response to a change in the peripheral temperature, interference of the flange123with the inner circumferential surface113bof the receiver113may be prevented. Hence, by the above structure, transmission of an undesired mechanical stress to the diaphragm122due to a volume change caused by the change in the peripheral temperature of the pressure sensor1is prevented, improving the measuring accuracy of the pressure sensor1.

The circuit board13is seated in the seat portion114of the sensor housing11, as shown inFIG. 4. The circuit board13has a sensor hole131formed to have a diameter greater than the diameter of the diaphragm122. When the circuit board13is seated in the seat portion114, the diaphragm122is positioned at a center of the sensor hole131. By the above structure, the strain gauge SG and the circuit board13are electrically connected easily, while the sensor header12and the circuit board13are sequentially assembled with the sensor housing11. In an embodiment, the strain gauge SG and the circuit board13are connected to each other by wire bonding.

A process of pressing the sensor header12in the sensor housing11using a jig2according to an embodiment is shown inFIG. 5.

The jig2, as shown inFIG. 5, applies pressure to the flange123without applying pressure to the diaphragm122of the sensor header12. The jig2includes a pressurizing plate21and a pressurizing protrusion22. The pressurizing plate21is spaced apart from the diaphragm122when the jig2is in contact with the flange123. In an embodiment, the pressurizing plate21has a flat top surface such that a pressurizing device to pressurize the jig2provides a uniform pressure to the jig2.

The pressurizing protrusion22protrudes from the pressurizing plate21and has a protruding length greater than a distance from a top surface of the flange123to a top surface of the diaphragm122in the embodiment ofFIG. 5. The pressurizing protrusion22has a symmetric shape about a center of the pressurizing plate21, for example, a hollow cylindrical shape. The shape of the pressurizing protrusion22is not limited to the cylindrical shape. In other embodiments, the pressurizing protrusion22may have a shape of a plurality of columns disposed along an edge of the pressurizing plate21. A distance from the center of the pressurizing plate21to an inner wall of the pressurizing protrusion22may be greater than a distance from the center of the diaphragm122to an edge of the diaphragm122. By the above shape, interference of the jig2with the diaphragm122while the jig2is pressurizing the flange123is prevented and transmission of a mechanical stress to the diaphragm122is prevented.

A method of manufacturing the pressure sensor1is shown inFIG. 6. The method includes a first operation91of aligning the sensor header12with the sensor housing11, a second operation92of pressing the sensor header12in using the jig2, a third operation93of assembling the circuit board13with the sensor housing11, a fourth operation94of electrically connecting the diaphragm122and the circuit board13, and a fifth operation95of assembling the connector14with the sensor housing11.

First, in the first operation91, the port121of the sensor header12is aligned with the housing pathway112of the sensor housing11. The insert1211and the fixing groove1223each having the diameter less than or equal to the diameter of the housing pathway112, among the port121of the sensor header12, are inserted into the housing pathway112, and the press-in part1222having the diameter greater than the diameter of the housing pathway112is aligned while being stopped by the housing pathway112.

Next, in the second operation92, the port121is pressed in the housing pathway112by applying pressure to the flange123of the sensor header12. In an embodiment, a worker may apply pressure to the flange123using the jig2shown inFIG. 5. The worker applies pressure to the jig2using a pressurizing device capable of position control and/or load sensing, for example, a servo press. By the above method, the worker may control the flange123to be stopped at a position spaced apart from the bottom surface113aof the receiver113based on a predetermined value. Further, the worker may easily perform quality control based on a load pattern during pressurization and a pressurizing depth of the sensor header12.

Next, in the third operation93, the circuit board13is seated in the sensor housing11. The circuit board13transmits a signal measured from the strain gauge SG disposed on the diaphragm122of the sensor header12to an external device. While the circuit board13is seated in the sensor housing11, the circuit board13and the strain gauge SG are connected to each other by wire bonding.

After the wire bonding of the circuit board13and the strain gauge SG, the connector14including the connection terminal142to be electrically connected to the circuit board13is assembled with the sensor housing11in the fourth operation94. After the third operation93and before the fourth operation94, the connecting terminal15is installed on the circuit board13. The connecting terminal15electrically connects the connection terminal142and the circuit board13.