JP2016039428A - Imaging unit for on-vehicle camera and on-vehicle camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress positional deviation of an imaging element under use environment, by simplifying the structure.SOLUTION: An imaging unit 30 includes a circuit board 50 on which an imaging element 61 is mounted, a circuit board supporting panel 40 having an opening 41 in which the imaging element 61 is placed, and placed on one surface of the circuit board 50 where the imaging element 61 is placed, and a fixing mechanism for fixing the circuit board 50 and circuit board supporting panel 40. The fixing mechanism includes fastening means for fastening the circuit board 50 and circuit board supporting panel 40, and an adhesive 70 for bonding the circuit board 50 and circuit board supporting panel 40. The adhesive 70 has such physical properties that the temperature at the inflection point of elastic modulus reduction is equal to or higher than the maximum temperature of operation guarantee.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an in-vehicle camera imaging unit and an in-vehicle camera.

  The in-vehicle camera cannot obtain a clear image if the optical axis of the circuit board on which the image sensor is mounted and the imaging lens system are shifted. Therefore, the circuit board on which the imaging element is mounted and the imaging lens system are aligned with high accuracy during assembly. This alignment needs to have high reliability against environmental changes such as temperature.

Conventionally, the following structure is known as an imaging device.
The circuit board on which the image pickup device is mounted is disposed at the axial end of the cylindrical portion of the cylindrical lens cell holding the image pickup lens system so that the image pickup device is positioned on the optical axis. An intermediate member having two side pieces bent in an L shape is interposed so that one side piece faces the lens cell and the other side piece faces the circuit board. An adhesive is provided between one side piece and the lens cell and between the other side piece and the circuit board, and the lens cell and the circuit board are fixed via an intermediate member. Further, the circuit board is fixed onto one end of the lens cell by a fastening member (see, for example, Patent Document 1).

JP 2011-1888070 A

  The imaging apparatus described in Patent Document 1 has a complicated structure because an L-shaped intermediate member is interposed between a circuit board on which an imaging element is mounted and a lens cell. Further, when the imaging device is placed in a high temperature environment, the adhesive may be deformed, and the imaging device may be displaced from the optical axis.

An imaging unit for an in-vehicle camera according to the present invention has a circuit board on which an image sensor is mounted and an opening on which the image sensor is disposed, and is for supporting a circuit board disposed on one surface on which the image sensor on the circuit board is mounted. And a fixing mechanism for fixing the circuit board and the circuit board supporting panel. The fixing mechanism includes a fastening means for fastening the circuit board and the circuit board supporting panel, and a circuit board and the circuit board supporting panel. The temperature of the inflection point of the elastic modulus lowering of the adhesive is equal to or higher than the maximum temperature guaranteed for operation.
An in-vehicle camera according to the present invention includes the above-described in-vehicle camera imaging unit, an imaging lens system, a lens system holding case for holding the imaging lens system, and a mounting panel to which the lens system holding case and the in-vehicle camera imaging unit are attached. Prepare.

  According to the present invention, the structure is simplified. In addition, it is possible to suppress the displacement of the image sensor under the usage environment.

The disassembled perspective view which shows one Embodiment of the vehicle-mounted camera of this invention. FIG. 2 is a plan view of the imaging unit illustrated in FIG. 1. FIG. 3 is a rear view of the support panel illustrated in FIG. 2. IV-IV sectional view taken on the line of FIG. The temperature characteristic figure of the elasticity modulus and loss factor (tan-delta) of an adhesive agent. The figure which shows the amount of position shift after a temperature cycle test. Sectional drawing which shows Embodiment 2 of the unit for vehicle-mounted cameras of this invention.

Embodiment 1
[Overall structure of in-vehicle camera]
Hereinafter, an embodiment of an in-vehicle camera unit and an in-vehicle camera according to the present invention will be described with reference to the drawings.
FIG. 1 is an exploded perspective view showing an embodiment of an in-vehicle camera according to the present invention.
The in-vehicle camera 1 includes an exterior panel (mounting panel) 10, an imaging lens system 21, a lens system holding case 22, a rear case 25, and an imaging unit 30.
The lens system holding case 22 has a cylindrical shape, and the imaging lens system 21 is built in the lens system holding case 22. A male screw portion 23 is formed on the rear side of the lens system holding case 22.
The exterior panel 10 is integrally formed with a cylindrical portion 12 having a through hole 11 through which the lens system holding case 22 is inserted.

  The lens system holding case 22 is fitted into the through hole 11 of the cylindrical portion 12 so that the front surface of the imaging lens system 21 protrudes to the front surface side of the exterior panel 10. At this time, the male screw portion 23 of the lens system holding case 22 protrudes from the rear end surface of the cylindrical portion 12. The rear case 25 has a cylindrical shape having an opening 25a at the bottom, and has a female screw portion 26 formed therein. The rear case 25 is attached to the lens system holding case 22 by screwing a female screw part 26 into the male screw part 23 of the lens system holding case 22 protruding from the cylindrical part 12. When attached to the lens system holding case 22, the center of the opening 25 a of the rear case 25 is located on the optical axis of the imaging lens system 21.

The imaging unit 30 includes a support panel (circuit board support panel) 40 and a circuit board 50 on which an imaging element 61 such as a CMOS or a CCD is mounted. The imaging unit 30 is attached to the exterior panel 10 by a fastening member (not shown). As will be described later, the circuit board 50 is fixed to the support panel 40, and the imaging unit 30 is fixed to the exterior panel 10 by fastening the support panel 40 to the exterior panel 10. An opening 41 into which the rear case 25 is fitted is formed in the support panel 40, and the image sensor 61 mounted on the circuit board 50 is disposed in the opening 41 of the support panel 40. The imaging unit 30 is attached to the exterior panel 10 so that the center of the imaging region (not shown) of the imaging element 61 is located on the optical axis of the imaging lens system 21.
Although not shown, a connection member such as a wire harness connected to the monitor display is connected to the circuit board 50, and an optical image read by the image sensor 61 is displayed on the monitor display.

[Structure of imaging unit]
2 is a plan view of the image pickup unit (vehicle-mounted camera unit) shown in FIG. 1, FIG. 3 is a back view of the support panel shown in FIG. 2, and FIG. 4 is an IV of FIG. FIG.
The support panel 40 is made of a metal such as aluminum or an aluminum alloy (aluminum-based metal), or a ceramic smith or a synthetic resin.
The support panel 40 is a substantially rectangular plate-like member, and an opening 41 is formed in a substantially central portion. A plurality (three in the embodiment) of female threads (fixing holes) 42 are formed on the peripheral edge of the opening 41. A plurality of (three in the embodiment) mounting holes 43 for inserting fastening members that fix the support panel 40 to the exterior panel 10 are formed in the side edge portion of the support panel 40.

  The back surface (the surface facing the circuit board 50) of the support panel 40 is a substantially flat surface, and a plurality of (six in the embodiment) grooves 45 are formed on the back surface. The groove 45 is provided at the peripheral edge of the opening 41, and is arranged in an annular shape at a position equidistant from the center of the opening 41 of the support panel 40, one to two between each female screw part 42. The center O of the opening 41 of the support panel 40 is disposed on the optical axis of the imaging lens system 21.

  A through hole 51 (see FIG. 4) is formed in the circuit board 50 at a position corresponding to the female screw portion 42 of the support panel 40. As described above, the image sensor 61 is mounted on the circuit board 50. On one side of the circuit board 50 facing the support panel 40, a wiring pattern (not shown) and connection terminals are formed, and the image sensor 61 is disposed in the opening 41 of the support panel 40, The terminals are bonded to the connection terminals of the circuit board 50.

  An adhesive 70 is filled in each groove 45 of the support panel 40. The circuit board 50 and the support panel 40 are bonded by an adhesive 70. The circuit board 50 is fixed to the support panel 40 with a fastening member 63 such as a bolt or a screw while being bonded to the support panel 40.

[Assembly method of imaging unit]
A method for assembling the imaging unit 30 will be described.
First, the support panel 40 and the circuit board 50 are washed with an organic solvent and dried. The surfaces to be cleaned may be the entire surfaces of the support panel 40 and the circuit board 50 or only the surfaces of the support panel 40 and the circuit board 50 facing each other.
A predetermined amount of adhesive 70 is filled in each groove 45 of the support panel 40. For filling the adhesive 70, for example, an application method using a dispenser can be applied. However, the present invention is not limited to this method, and other methods such as printing and transfer may be used. The physical properties of the adhesive 70 will be described later, and examples thereof include a thermosetting epoxy resin system. The filling amount of the adhesive 70 is set such that the upper surface of the adhesive 70 slightly rises from the same surface as the back surface of the support panel 40.

  Next, the circuit board 50 on which the image sensor 61 is mounted is disposed on the back surface of the support panel 40. The circuit board 50 aligns each through-hole 51 with the corresponding female screw portion 42 of the support panel 40 and closely contacts the back surface of the support panel 40. In this state, the fastening member 63 is inserted into the through hole 51 of the circuit board 50 and fastened to the female screw portion 42 of the support panel 40. Thereafter, the adhesive 70 is thermally cured. As a result, the support panel 40 and the circuit board 50 are bonded together by the adhesive 70 interposed between the two members and fixed in a state of being fastened by the fastening member 63.

In the case where the thermosetting adhesive 70 is used, it is preferable that the temperature at which the adhesive 70 is thermoset is equal to or higher than the maximum temperature that guarantees the operation of the imaging unit 30. By setting the adhesive 70 to be equal to or higher than the maximum temperature for guaranteeing the operation of the imaging unit 30, moisture contained in the adhesive 70 is released at the time of thermosetting, and imaging is performed with a gas released from the adhesive 70 in a use state. The risk that the element 61 is contaminated can be reduced.
Next, the physical properties of the adhesive 70 will be described.

[Physical properties of adhesive]
The adhesive 70 (hereinafter, simply referred to as “adhesive” as appropriate) is a material whose temperature at which the loss factor obtained from the dynamic viscoelasticity measurement is 0.05 is equal to or higher than the maximum temperature for guaranteeing the operation of the imaging unit 30. It is formed by. The imaging unit 30 is installed in a high-temperature environment at about 105 ° C., for example. The adhesive softens with increasing temperature and the elastic modulus decreases. If the temperature at which the loss factor obtained from the dynamic viscoelasticity measurement of the adhesive is 0.05 is less than the maximum temperature guaranteed for the operation of the imaging unit 30, the position of the circuit board 50, in other words, the deformation of the adhesive. The position of the imaging region of the imaging element 61 is shifted. For this reason, the position of the captured image cannot be accurately displayed.

FIG. 5 shows a temperature characteristic diagram of the elastic modulus and loss factor (tan δ) of the adhesive.
The loss factor (tan δ) of the adhesive has an inflection point at which the elastic modulus changes rapidly at a predetermined temperature. The elastic modulus of the adhesive rapidly decreases at the inflection point of the elastic modulus. In FIG. 5, the temperature indicated by the dotted line is the inflection point at which the elastic modulus decreases, and in this example, the temperature at the inflection point at which the elastic modulus decreases in the adhesive 70 (tan δ rise temperature) is tan δ is 0.05. It is about 124 ° C. When the guaranteed temperature of the imaging unit 30 is about 105 ° C., the temperature of the inflection point of the elastic modulus reduction of the adhesive 70 is higher than the guaranteed temperature of the imaging unit 30. The top of the tan δ curve is the glass transition point.

An example of a conventional adhesive tan δ curve is indicated by a two-dot chain line. In the conventional adhesive, the temperature of the inflection point at which the elastic modulus decreases is about 100 ° C., which is lower than the guaranteed temperature of the imaging unit 30 of about 105 ° C. As described above, the adhesive whose temperature at the inflection point of lowering the elastic modulus is lower than the maximum temperature for guaranteeing the operation of the imaging unit 30 is greatly deformed near the maximum temperature for the guarantee of the imaging unit 30, and the imaging element. 61 misalignment occurs.
On the other hand, if an adhesive having an inflection point at which the elastic modulus lowers is equal to or higher than the maximum temperature for guaranteeing the operation of the image pickup unit 30, for example, deformation of the adhesive even under a high temperature environment of 105 ° C. Can be suppressed, and displacement of the image sensor 61 can be suppressed.

[Reliability evaluation]
The reliability test evaluation performed on the imaging unit 30 will be described.
The reliability test evaluation was performed by a method in which a temperature cycle impact test was performed and a positional deviation amount of the circuit board 50 with respect to the support panel 40 was measured after the test. In the temperature cycle impact test, a thermal shock test was performed for 200 cycles, in which the thermal shock step of leaving the imaging unit 30 at −40 ° C. and 105 ° C. for 30 minutes was one cycle.
FIG. 6 is a diagram showing the amount of misalignment after the temperature cycle test.
In FIG. 6, in the example, the temperature at which the loss factor of the elastic modulus is 0.05 is 140 ° C., an adhesive having a glass transition point of 160 ° C. is used, and the screw (fastening member) 63 is used for fastening. The structure.
A fixing structure in which only the screws 63 are fastened without using an adhesive is used as a conventional example. Also, a structure in which an adhesive having an elastic modulus loss coefficient of 0.05 at a temperature of 100 ° C. and a glass transition point of 110 ° C. and fastened by a screw 63 was used as a comparative example.

As a result of the evaluation after the temperature cycle impact test, in the conventional and comparative examples, as shown in FIG. 6, the positional deviation amount of the circuit board 50 with respect to the support panel 40 was 0.9 μm.
On the other hand, in the embodiment of the present invention, the amount of displacement of the circuit board 50 with respect to the support panel 40 was less than 0.4 μm.
Thereby, it was confirmed that the structure of the example suppresses the amount of displacement of the circuit board 50 with respect to the support panel 40 as compared with the conventional and comparative examples.

The imaging unit 30 according to the first embodiment has the following effects.
(1) The circuit board 50 and the support panel 40 are interposed between the circuit board 50 and the support panel 40 in a state where the support panel 40 is disposed on one surface of the circuit board 50 on which the imaging element 61 is mounted. The adhesive 70 and the fastening member 63 that fastens the circuit board 50 to the support panel 40 were fixed. Thus, since it is a structure which does not require a joining intermediate member between the circuit board 50 and the support panel 40, a structure is simple and an assembly | attachment is easy.

(2) As the adhesive 70 for bonding the circuit board 50 and the support panel 40, a material having a physical property in which the temperature at the inflection point of the decrease in elastic modulus is equal to or higher than the maximum temperature for guaranteeing the operation of the imaging unit 30 is used. For this reason, it is possible to suppress the displacement of the circuit board 50 on which the imaging element 61 is mounted with respect to the support panel 40, which is caused by the deformation of the adhesive 70 within the operation guarantee range of the imaging unit 30.

(3) Using an adhesive 70 having a physical property that has a thermosetting temperature equal to or higher than the maximum temperature guaranteed for the operation of the imaging unit 30, the circuit board 50 is fastened to the support panel 40 by the fastening member 63, and then the adhesive 70 is imaged. The unit 30 was thermally cured at a temperature higher than the maximum temperature guaranteed for operation. For this reason, the moisture etc. which are contained in the adhesive 70 at the time of thermosetting are discharged | emitted, and the risk that the image pick-up element 61 will be contaminated by the gas released from the adhesive 70 in use can be reduced.

(4) The groove 45 is provided in the support panel 40 and the adhesive 70 is filled in the groove 45. As a result, it becomes easy to make the application amount of the adhesive 70 for bonding the circuit board 50 and the support panel 40 constant, variation in adhesive force can be reduced, and reliability can be improved.

(5) The groove 45 of the support panel 40 to which the adhesive 70 is applied is formed at a position equidistant from the center of the opening 41 of the support panel 40 located on the optical axis of the imaging lens system 21. For this reason, the stress which acts on the circuit board 50 by the thermal expansion / contraction of the adhesive 70 becomes symmetric, and the positional deviation amount of the circuit board 40 can be reduced.

Embodiment 2
FIG. 7 is a sectional view showing Embodiment 2 of the on-vehicle camera unit of the present invention.
The imaging unit 30A illustrated in FIG. 7 is different from the imaging unit 30 according to the first embodiment illustrated in FIG. 2 in that the support panel 40A includes one female screw portion 42 and two pin holes 46. Is different. The circuit board 50A of the second embodiment is not shown, but of the three female screw portions 42 in the circuit board 50 of the first embodiment, the two female screw portions 42 are pin holes having the same diameter as the pin holes of the support panel 40A. Has been replaced.

As in the first embodiment, the circuit board 50A is attached to the support panel 40A by bonding the support panel 40A and the circuit board 50A with an adhesive, and inserting the fastening member 63 into the through hole 51 of the circuit board 50A. Fastened to the female screw portion 42 of 40A. Then, a pin (not shown) having a head is inserted through the pin hole of the circuit board 50A and the pin hole 46 of the support panel 40A. Since the pins are used for temporary fixing for positioning the support panel 40A and the circuit board 50A, it is not necessary to crimp the pins on the side opposite to the insertion side. Thereafter, the adhesive 70 is thermally cured. Then, after thermosetting the adhesive 70, the pin is removed.
The pins may be inserted into the pin holes of the circuit board 50A and the pin holes 46 of the support panel 40A and caulked on the side opposite to the insertion side.

Other configurations of the second embodiment are the same as those of the first embodiment.
Therefore, the second embodiment also has the same effect as the first embodiment. In addition, the pins have a smaller diameter than bolts and screws, and the fixing or temporary fixing with the pins simplifies the structure. For this reason, according to the second embodiment, the structure is further simplified, and the imaging unit 30A can be downsized.

  In each of the above embodiments, the fastening member 63 such as a bolt or a screw is exemplified as a structure that is fastened to the female screw portion 42 provided on the support panel 40. However, the female screw portion 42 of the support panel 40 may be a through hole through which the fastening member 63 is inserted, and a nut may be fastened to the fastening member 63 inserted through the through hole.

  In the said embodiment, it illustrated as a structure which used the circuit board 50 as the single layer. However, the circuit board 50 may be a laminated board. By using the circuit board 50 as a laminated board, the area of the circuit board 50 can be reduced. If the support panel 40 has a small area corresponding to the circuit board 50, the area of the imaging unit 30 can be reduced, and the imaging unit 30 can be installed in a narrow space.

  In the above embodiment, the groove 45 for applying the adhesive 70 to the support panel 40 is formed, but the groove 45 is not necessarily required.

  In addition, the present invention can be variously modified within the scope of the invention. In short, the present invention includes a fixing mechanism for fixing the circuit board and the circuit board supporting panel, and the fixing mechanism is a circuit board. Fastening means for fastening the circuit board support panel to the circuit board, and an adhesive for bonding the circuit board and the circuit board support panel. Any material having a physical property equal to or higher than the temperature may be used.

1 In-vehicle camera 10 Exterior panel (panel for mounting)
21 imaging lens system 22 lens system holding case 25 rear case 30, 30A imaging unit 40, 40A support panel (panel for circuit board support)
41 Opening 42 Female thread (fixing hole)
45 groove 46 pin hole 50, 50A circuit board 51 through-hole 61 imaging element 63 fastening member 70 adhesive

Claims (10)

A circuit board on which an image sensor is mounted;
A circuit board support panel disposed on one surface of the circuit board on which the image sensor is mounted; and an opening in which the image sensor is disposed;
A fixing mechanism for fixing the circuit board and the circuit board support panel;
The fixing mechanism is
Fastening means for fastening the circuit board and the circuit board support panel; and an adhesive for bonding the circuit board and the circuit board support panel;
The imaging unit for in-vehicle cameras, wherein the temperature of the inflection point of the elastic modulus lowering of the adhesive is equal to or higher than the maximum temperature guaranteed for operation. The in-vehicle camera imaging unit according to claim 1,
The in-vehicle camera imaging unit, wherein the temperature at the inflection point of the elastic modulus reduction of the adhesive is a temperature at which the loss coefficient obtained from the dynamic viscoelasticity measurement is 0.05. The in-vehicle camera imaging unit according to claim 2,
The maximum temperature for the operation guarantee is 105 ° C. or higher, and an imaging unit for an in-vehicle camera. The in-vehicle camera imaging unit according to claim 1,
The adhesive is a thermosetting resin having a thermosetting temperature higher than the maximum temperature of the operation guarantee, and is thermoset before fastening the circuit board and the circuit board supporting panel by the fastening means. In-vehicle camera imaging unit. The in-vehicle camera imaging unit according to claim 1,
The circuit board supporting panel is an in-vehicle camera imaging unit formed of an aluminum-based metal. The in-vehicle camera imaging unit according to claim 1,
An in-vehicle camera imaging unit in which a groove is formed in a portion of the circuit board support panel that is bonded to the circuit board by the adhesive, and the adhesive is filled in the groove. The in-vehicle camera imaging unit according to claim 1,
The fastening means includes
A plurality of fixing holes formed at the peripheral edge of the opening of the circuit board support panel;
A plurality of through holes formed in the circuit board corresponding to each of the fixing holes;
An in-vehicle camera imaging unit including the through hole and a fastening member inserted into each of the fixing holes corresponding to the through hole. The in-vehicle camera imaging unit according to claim 7,
A female thread portion is formed in each of the fixing holes of the circuit board support panel,
An on-vehicle camera imaging unit, wherein each of the fastening members is formed with a male screw portion fastened to the female screw portion. The in-vehicle camera imaging unit according to claim 7,
An internal thread portion is formed in at least one of the plurality of fixing holes,
At least one of the plurality of fastening members is formed with a male screw portion fastened to the female screw portion,
At least another one of the plurality of fastening members is an in-vehicle camera imaging unit, which is a pin inserted through the through hole and the fixing hole. An imaging unit for a vehicle-mounted camera according to any one of claims 1 to 9,
An imaging lens system;
A lens system holding case for holding the imaging lens system;
A vehicle-mounted camera comprising the lens system holding case and a mounting panel to which the vehicle-mounted camera imaging unit is mounted.

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