FR2800462A1 - Fabrication of automobile dashboard instrumentation panel with instruments controlled by step by step motor whose field winding is positioned so that during soldering heat does not effect synthetic resin teeth on a reduction gear - Google Patents

Abstract

The rotor (40d) of the step by step motor is positioned on the rear side of the circuit card (30). Its poles (46b,47b) extend from the magnet cores (46) through the circuit card to face the rotor (40d). Soldering of the field winding onto the circuit card is done by a 'refusion' or 'wave' method. The dashboard includes: (a) a graduated plaque (10); (b) a pointer finger (50) rotated on an axis (45a); (c) a drive (40) designed to rotate the pointer finger, which includes a step by step motor; (d) a circuit card (30) designed to electrically connect the motor field winding (48,49), positioned on the rear side of the plaque so that an interior space is formed between the plaque and the circuit card; (e) the field winding (48) and the magnetic cores (46) are supported by the circuit card. The field winding is electrically connected to the circuit card by soldering.

Description

BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates to a dashboard having a motor-driven needle for use in a motor vehicle. or other devices.

2. Description of the Related Art An example of this type of dashboard is described in JP-A-9-21655. In the dashboard described therein, a device for driving a needle is installed behind a printed circuit board and is electrically connected to the circuit board by soldering. Another example is shown in JP-A-8-233611. The dashboard present therein comprises a stepper motor for driving a needle through a gear reducer gear. The toothed elements constituting the reduction gear train are made of synthetic resin in order to suppress gear noise and to reduce the mass.

The toothed elements made of synthetic resin, however, are not very resistant to the heat that is generated by a brazing process such as wave soldering reflow soldering. The toothed elements tend to be heat damaged by a soldering process. SUMMARY OF THE INVENTION The present invention has been made in view of the above mentioned problem, and an object of the present invention is to provide an improved dashboard which is readily manufactured without causing damage to sensitive components. heat by heat of brazing.

A dashboard such as a dial unit intended for use in a motor vehicle comprises one or more needles driven by a motor such as a stepper motor. The instrument panel consists of a front panel with graduations and numbers printed on it, a rotatable needle, a motor not intended to drive the needle, a gear train reducer disposed between the needle and the motor to reduce the rotation angle of the motor, and a circuit board for electrically connecting a field coil of the motor and other components. The circuit board is positioned behind the front panel, leaving some space between them. The gear reducer comprises a plurality of toothed elements made of synthetic resin, which is resistant and heat sensitive. The terminals of the field coil are bridged on the circuit board by a reflow soldering or wave soldering process.

In order to protect the resin tooth elements sensitive to the heat of soldering heat, the components such as the field coil are first deposited on the circuit board and soldered thereon. After the brazing temperature has dropped, the gear reducer gear having heat sensitive resin gear teeth is mounted on the circuit board. The stator of the motor having the field coil can be placed on the front side of the circuit board, and the motor rotor as well as the gear reducer gear can be placed on the rear side. An entire motor including its rotor can be placed on the front side of the circuit board and only the gear reducer gear can be placed from the rear side.

Alternatively, an integral drive comprising the motor and the reduction gear can be positioned on the rear side of the circuit board, as long as the field coil is brazed to the circuit board first, and Then gear reducer gear is mounted on the circuit board after the soldering heat has dissipated. In this structure, a wide space is available on the front side of the circuit board. Accordingly, other components such as a source of illumination light, are readily arranged on the front side.

A light conducting plate having a cut aperture may be attached to the rear surface of the front panel. In this case, the components such as the stator, placed on the front side of the circuit board, can be positioned in the cut-out opening to reduce the dashboard thickness.

The heat-sensitive resin tooth members are protected against brazing heat in accordance with the present invention. In addition, an automatic reflow soldering or wave soldering process can be used to reduce manufacturing costs.

Other objects and features of the present invention will become more apparent from a better understanding of preferred embodiments described below with reference to the accompanying drawings.

 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view showing a dashboard for use in a motor vehicle. Fig. 2 is a cross-sectional view showing dashboard as a first embodiment of the present invention. 3 is a plan view showing a stepper motor used in the dashboard shown in FIG. 2; FIG. 4 is a cross-sectional view showing a table of FIG. as a second embodiment of the present invention, taken along the line similar to that of FIG. 2; FIG. 5 is a cross-sectional view showing a dashboard as a third embodiment of the present invention, taken along the line VV in Fig. 6; Fig. 6 is a plan view showing a stepping motor used in the dashboard shown in FIG. Fig. 5; Fig. 7 is a cross-sectional view showing; a casing of the third embodiment, in which a reduction gear train and a rotor are provided, and Fig. 8 is a side view showing a stator used in the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to Figs. 1 to 3. Fig. 1 shows a front view of a dashboard for use in a form automobile. a dial block. The instrument panel U comprises a front panel 10 on which a graduated plate 10a intended to indicate the speed of the vehicle (speedometer) and another graduated plate intended to indicate the rotational speed of the engine (revolutions of the engine) are arranged. On each graduated plate 10a, 10b, an arcuate transparent portion 11, 12 having graduations and figures made. The vehicle speed and the engine rotational speed are indicated by respective hands 50. Each needle driven by a respective stepper motor installed behind the front panel 10. The front panel also comprises a portion of indicators 10c which indicates the positions. speeds of an automatic transmission. An edge plate 70 is disposed at the periphery of the front panel 10.

Referring to Figure 2, which is a cross-sectional view of the dashboard taken along the line II-II in Figure 1, the dashboard structure will be described. Since the structure of the speedometer (left dial in FIG. 1) and that of the engine tachometer (rightmost dial in FIG. 1) are substantially the same, the structure of one speedometer will be described here. below as a representative structure of the two indicators. A light conducting plate 20 made of transparent acrylic resin, polycarbonate resin or the like is attached to the rear surface of the front panel 10. An opening 21 facing the vicinity of a through hole 13 through which an axis of the needle 45a for driving the needle 50 extends is formed in the plate leading the light 20. A reflective film is formed on the rear surface of the light-conducting plate 20. Behind the light-conducting plate 20, a circuit board printed 30 is disposed. A housing 40a containing most elements of a driving device 40 for driving the needle 50 is attached to the rear surface of the circuit board 30.

Now, the drive device 40 will be described in detail with reference to FIGS. 2 and 3. The housing 40a includes a first wall 41a attached to the rear circuit board surface 30 and a second wall 41b facing the first wall 41a. . The drive device 40 comprises a step motor M and a reduction gear train 40b. The stepper motor M is composed of a rotor 40d made of a magnet and a stator 40c. The reduction gear train 40b and the rotor 40d are disposed in the housing 40a, while the stator 40c is disposed in a space between the front panel 10 and the circuit board 30.

The reduction gear train 40b is comprised of four serrated gear elements 42 to 45. The gear 42 is connected to the rotor 40d and attached to a pinion shaft 42a which is rotatably supported between the first and second walls 41a. , 41b. The spur gear 43 engaging gear pinion 42 is attached to pinion shaft 43a together with pinion 44, and pinion shaft 43a is rotatably supported between the first and second walls 41a. , 41b. The spur gear 45 engaging the pinion 44 is attached to an axis of the needle 45a which is rotatably supported between the first and second walls 41a, 41b.

The axis of the needle 45a further extends towards the front surface of the dashboard via a through hole 31 formed in the circuit board 30 and a through hole 13 formed in the front panel 10. The axis of the needle 45a is connected to the needle 50 at a barrel 51 of the needle 50. The diameter of the wheel 43 is greater than that of the pinions 42 and 44, and the The diameter of the wheel 45 is greater than that of the pinion 44. The rotation angle of the rotor 40d is reduced by means of the reduction gear train 40b and the needle 50 is rotated by the reduced angle. All toothed elements 42 to 45 are made of synthetic resin (eg soft resin) in order to reduce the gearing noises generated by the rotating engagement between the toothed elements. .

The stepping motor M, as shown in FIGS. 2 and 3, consists of the rotor 40d disposed in the housing 40a and the stator 40c disposed in the space between the circuit board 30 and the front panel 10. The stator 40c consists of a pair of yokes 46, 47 mounted on the circuit board 30 and a pair of field coils 48, 49 wound around the yokes, as best seen in FIG. 3. The yoke 46 comprises a U-shaped yoke body 46a and a pair of poles 46b bent from the end portions of the bolt body. Similarly, the yoke 47 has a U-shaped head body 47a and a pair of poles 47b bent from the end portions of the bolt body. The two yokes 46, 47 are placed symmetrically with each other with respect to a line connecting the pinion axis 42a and the axis of the needle 45a, as shown in FIG. of yokes 46a, 47a having the field coils 48, 49 are positioned in the space between the circuit board 30 and the front panel 10 so that they are partly accommodated in the opening 21 of the light-conducting plate 20, as shown in FIG. 2. The poles 46b, 47b of the respective yokes 46, 47 extend into the interior of the housing 40a through through holes 32 formed in the circuit board 30, so that the poles 46b, 47b are facing the rotor 40d disposed in the housing 40a with an air gap between them.

A pair of terminals 48a of the field coil 48 and a pair of terminals 49a of the field coil 49 are respectively soldered to terminals formed on the front surface of the circuit board 30 by reflow soldering. An electric current is supplied from a power source to the two field coils 48, 49 via the soldered terminals on the circuit board 30. A magnetic circuit is formed by the two yokes 6, 47 and the rotor 40d, and as a result, the rotor 40d is driven. The rotation of the rotor 40d is transferred to the axis of the needle 45a through the gear reduction gear 40b. The stepping motor M for driving the pointer of the speedometer 50 rotates in accordance with the speed of the vehicle, while the stepper motor M for driving the tachometer needle of the motor 50 rotates according to at engine rotation speed.

A light source 60 for illuminating either the needle 50 or the graduated plate 10a, 10b or both is mounted and soldered to the front surface of the circuit board 30 as shown in FIG.

The drive device 40 comprising the reduction gear train 40b and the stepper motor M is assembled and electrically connected to the circuit board 30 in the following manner. First, the housing 40a containing the gear reduction gear 40b and the rotor 40d therein, the stator 40c and the circuit board 30 having the illumination source 60 are prepared separately. Then, the poles 46b, 47b bent from the respective yokes 46, 47 are inserted into the through holes 32 formed in the circuit board 30 to thereby support the yokes 46, 47 along the front surface of the circuit board 30. The field coil terminals 48a, 49a are also inserted into the terminal holes formed on the front surface of the circuit board 30. Thereafter, the terminals 48a, 49a are brazed to the circuit board 30 by a reflow soldering process. . Thus, the field coils 48, 49 are electrically connected to the circuit board 30. After the heat generated by a reflow soldering process has dropped, the case 40a is connected to the rear surface of the circuit board 30, so that the axis of one needle 45a extends towards the front side through the through hole 31, and that the poles 46b, 47b extend into the interior of the housing 40a through the through holes 32 formed in the first wall 41a.

Then, the circuit board 30 is assembled on the light conducting plate 20 so that the circuit board 30 is supported on the back surface of the light conducting plate 20 with a predetermined distance therebetween. The axis of the needle 45a extends to the front side of the front panel 10 through the through hole 13 formed in the front panel 10. The yoke bodies 46a, 47a having the field coils 48, 49 wound around these are positioned in the opening 21 of the light-conducting plate 20 in the space between the circuit board 30 and the front panel 10. Thus, the driving device 40 and the circuit board 30 are assembled and electrically connected. -.

 Since the housing 40a containing the heat-sensitive resin gear members therein is connected to the rear surface of the circuit board 304 after the heat of reflow soldering in the circuit board 30 has dissipated, the elements Resin gears are not damaged by reflow soldering heat. Therefore, brazing on the circuit board can be achieved by an automatic reflow soldering process without worrying about damage to the resin gear elements. Thus, the dashboard can be manufactured at a low cost. Further, since the stator 40c is positioned in the space within the aperture 21 of the light-conducting plate 20, the thickness of the dashboard can be made smaller. In addition, since the circuit board 30 is commonly used to assemble the light source 60 and to electrically connect the field coils 48, 49, the dashboard structure is simplified.

second embodiment of the present invention will be described with reference to FIG. 4. The second embodiment is the same as the first embodiment except that the rotor 40d is disposed in front of the circuit board 30, and not in the case 40a. The poles 46b, 47b of the yokes 46, 47 do not need to extend into the housing 40a. The rotor 40d is positioned in a recessed space 33 in front of the circuit board 30 and is rotatably supported by the axis of the pinion 42a at the same time as pinion 42.

The circuit board 30 and the driving device 40 are assembled in a manner similar to that of the first embodiment. That is, the field coil terminals 48a, 49a are electrically connected to the circuit board 30 by reflow soldering process. After soldering heat has dissipated, the housing 40a containing the heat-sensitive resin gear members therein is attached to the rear surface of the circuit board. As a result, the toothed resin elements are not damaged by the heat of the soldering.

A third embodiment of the present invention will be described with reference to Figs. 5 to 8. In this embodiment, the first mode driving device 40. A motor Ma including its rotor 70d and a reduction gear train 70b are all disposed in a housing 70a. The drives for the engine speedometer and tachometer have a similar structure in this embodiment, too. As a result, the drive device 70 for the speedometer is described as a representative device of the two drive devices. The housing 70a housing the drive device 70 therein connected to the rear surface of the circuit board 30. As shown in FIG. 5, the housing 70a includes an inner wall 71b, a rear wall 7 and a circular wall . The circular wall 72 is formed at a position corresponding to the graduated plate 10a on the front panel 10. A pair of flexible projections 72b extend from the circular wall 72, which are inserted into engagement holes. 33 is formed in the circuit board 30 to connect the housing 70a to the circuit board 30. The stator 70c stepper motor Ma is disposed in a space limited by an inner wall 71b and the circular wall 72. The gear train Reducer 70b is installed in a space between the inner wall 71b and the rear wall 71c. A cylindrical space is also formed in the housing 70a, in which the rotor 70d is disposed.

The reduction gear train 70b consists of four toothed elements 73a, 73b, 73c and 73d. The pinion 73a connected to the rotor 70d is fixed to a pinion shaft 74a which is rotatably supported between the rear wall 71c and a bottom wall of the cylindrical space 71a. The gear 73b engaging the gear 73a is connected to the gear 73c and fixed to a pinion axis 74b which is rotatably supported between the rear wall 71c and the inner wall 71b. The gear 73d engaging the gear 73c is fixed to an axis the needle 74c which is rotatably supported between the rear wall 71c and the inner wall 71b. The axis of the needle 74c further extends towards the front panel 10 to be connected to the needle 50.

The diameter of the gear 73a engaging with the gear 73b is smaller than that of the gear 73b. The diameter of the gear 73c engaging the gear 73d is smaller than that of the gear 73d. The rotation angle of the motor Ma is transferred to the axis of the needle 74c via the reduction gear train 70b at a predetermined reduction rate. All toothed elements 73a to 73d are made of synthetic resin which is heat-sensitive.

As shown in FIGS. 5 and 6, the stepper motor Ma consists of a stator 70c and a rotor 70d. The stator 70c is disposed on the circuit board 30 within the circular wall 72, and the rotor 70d is rotatably supported in the cylindrical space 71a.

The stator 70c comprises a pair of yokes 75, 76 and field coils 77, 78 wound around the respective yokes, as shown in FIG. 6. The yokes of the pair of yokes 75, 76 are arranged symmetrically one of the yokes 75, 76. the other with respect to a line connecting the pinion axis 74a and the axis of the needle 74c, as shown in FIG. 6. The yoke 75 has a U-shape and comprises a bolt body 75a and poles 75b which face the rotor 70d with an air gap between them. Similarly, the yoke 76 has a U shape and has a yoke body 76a and poles 76b which face the rotor 70d with an air gap between them.

The pins of a pair of terminal pins 77a connected to the field coil 77 wound around the bolt body 75a are inserted into holes formed in the circuit board 30 (see FIG. 8). Similarly, the pins of a pair of terminal pins 78a connected to the field coil 78 wound around the bolt body 76a are inserted into holes formed in the circuit board 30. The terminal pins 77a, 78a are brazed on the circuit board 30 by a reflow soldering process, making soldered portions 34 on the front surface of the circuit board 30, as shown in FIG. 5.

An electric current is applied to the two field coils 77, 78 from the circuit board 30 via the terminal pins 77a, 78a to generate a magnetic field in a magnetic circuit formed by the two yokes 75, 76 and the 70d rotor. The rotor 70d consisting of a magnet is rotated in the magnetic field generated by the field coils 77, 78. The axis of the needle 74c driven by the motor Ma via the reduction gear train 70b extends to the front surface of the front panel 10 and is connected to the needle 50, in the same manner as in the first embodiment.

Referring to Figures 7 and 8, a method of mounting and brazing the drive device 70 will be described. Firstly, the housing 70a in which the reduction gear train 70b and the rotor 70d are installed (as shown in Fig. 7), the stator 70c (as shown in Fig. 8) and the circuit board 30 including the illumination light source 60 are prepared. Then, the terminal pins 77a, 78a of the stator 70c are inserted into the holes formed in the circuit board 30 to support the stator 70c the rear surface of the circuit board 30. Next, the terminal pins 77a, 78a are connected electrically to the circuit board 30 by reflow soldering, forming the brazed portions 34 on the front surface of the circuit board 30.

After the heat generated by a reflow soldering process has dissipated, the circuit board 30 on which the stator 70c is mounted is connected to the housing 70a which houses the reduction gear train 70b and the rotor 70d into the gearbox 70b. this. The axis of the needle 74c extends forward into through hole 31 formed in the circuit board 30, and the poles 75b, 76b of the yokes face the rotor 70d with air gaps between them. The housing 70a is mechanically fixed to the circuit board 30 by inserting the flexible protrusions 72b into the engaging holes 33 formed in the circuit board 30. Next, the circuit board 30 to which the driver 70 is connected and the plate leading to the light 20 having the front panel 10 is mounted together in the same manner as in the first embodiment. The axis of the needle 74c extends through the through hole 13 formed on the front panel 10, is connected to the needle 50.

Since, in the third embodiment, all the components constituting the driving device 70 are positioned on the rear side of the circuit board 30, there is sufficient space available to mount other necessary components on the front surface of the circuit board 30. circuit board 30. The stator 70c which requires brazing is first connected to the circuit board 30, and then, after the heat generated by a reflow soldering process has dissipated, the housing 70a which houses the Heat-resistant resin denier elements are attached to the circuit board 30. As a result, the resin gear teeth are not damaged by the heat generated by a brazing process. Although the rotor 70d is positioned on the rear side of the circuit board 30 in the third embodiment, it is also possible to position the rotor 70d on the front side of the circuit board 30 as in the second embodiment.

The brazing is carried out by a reflow soldering process in the embodiments described above, it is also possible to use a wave soldering process. The dashboard according to the present invention is not limited to use in automobiles, but can be used on motorcycles and other equipment.

Although the present invention has been presented and described with reference to the foregoing preferred embodiments, it will be apparent to those skilled in the art that changes in form and detail can be made to it without departing of the scope of the invention as defined in the appended claims.

Claims (10)

An instrument panel comprising a graduated plate (10a, 10b) having numbers and graduations thereon, a needle (50) rotatable on a front side of the graduated plate, the needle being connected to an axis of the needle (45a), a driving device (40) for driving in rotation axis of the needle, the driving device comprising: a stepping motor (M) consisting of a stator (40c) comprising a field coil (48, 49) wound around a yoke 47) and a rotor (40d) having a magnet, and a gear reduction gear (40b) having a plurality of gear elements in synthetic resin (42 to 45) operatively connected between the rotor of the stepper motor and the axis of the needle, and a circuit board (30) for electrically connecting the field coil, positioned on the back side of the the graduated plate to form an interior space between the graduated plate and the circuit board, wherein the field coil (48, 49) and the yoke (46,) are supported by the circuit board (30) and positioned in the interior space, the field coil being electrically connected to the circuit board by brazing, and the gear reducer gear (40b) is positioned on the rear side of the circuit board. 2. A dashboard according to claim 1, wherein the rotor (40d) of the stepper motor is positioned on the rear side of the circuit board (30), poles (46b, 47b) extend from the cylinder head (46), 47) through the circuit board and face the rotor (40d) with an air gap, brazing of the field coil on the circuit board is accomplished by a reflow soldering or soldering process. the wave. The instrument panel of claim 1, wherein the rotor (40d) is positioned on the front side of the circuit board (30), and brazing the field coil on the circuit board is realized by a process of reflow soldering or wave soldering. The instrument panel according to claim 1, further comprising a light-conducting plate (20) disposed in the interior space in contact with the graduated plate (10a, 10b), the light-conducting plate having a cut-out aperture ( 21), wherein the axis of one needle (45a) extends forwardly from the driver (40) through the circuit board, the plate opening leading the light and the graduated plate and the yoke 6, 47) and the stator field coil (48, 49) are positioned in the opening of the light conducting plate. An edge panel comprising a graduated plate (10a, 10b) having numbers and graduations thereon, and a needle (50) rotatable on a front side of the graduated plate, the needle being connected to an axis of the needle (74c), a driving device (70) for driving in rotation the axis of the needle, the driving device comprising. a stepper motor (Ma) consisting of a stator (70c) comprising a field coil (77, 78) wound around a yoke (75, 76) and a rotor (70d) comprising a magnet and a train gearbox gear (70b) having a plurality of synthetic resin gearwheels (73a to 73d) operatively connected between the rotor dtf-stepper motor axis of the needle, and a circuit board ( 30), for electrically connecting the field coil, positioned on the rear side of the graduated plate to form an interior space between the graduated plate and the circuit board, where all the components of the driving device (70). are disposed on the rear side of the circuit board (30) and supported by the circuit board, and the field winding terminals (77, 78) are pulled out from the front side of the circuit board (30) and brazed on the surface before the circuit board. 6. Instrument panel according to claim 5, wherein the soldering of the terminals is carried out by a reflow soldering or wave soldering process. The dashboard of claim 1, further comprising a light source (60) for illuminating either the needle or the graduated plate, or both, the light source being supported on the circuit board (30). and electrically connected thereto. The dashboard of claim 5, further comprising a light source (60) for illuminating either the needle or the graduated plate, or both, the light source being supported on the circuit board (30). and electrically connected to it. 9. A method of manufacturing a dashboard comprising a needle (50), a motor (M) for driving the needle, a reduction gear train of synthetic resin (40b) disposed between the needle and the motor, and a circuit board <B> (30) </ B> for electrically connecting a field coil (48, 49) of a stator component of the motor, the method comprising separately preparing the train of gear reducer (40b), circuit board (30), and stator (40c). having the field coil, the stator deposition (40c) having the field coil on a front surface of the circuit board, brazing the field coil terminals (48, 49) on the front surface of the field board circuit (30), cooling the circuit board (30) to dissipate heat generated by brazing, and mounting the reduction gear train (40b) on the rear surface of the circuit board (30). 10. A method of manufacturing a dashboard comprising a needle (50), a motor (Ma) for driving the needle, a reduction gear train synthetic resin (70b) disposed between the needle and the motor, and a circuit board (30) for electrically connecting a field coil (77, 78) of a motor stator (70c), the method comprising separately preparing the gear reducer gear (70b). ), the circuit board (30) and the stator (70c) having the field coil, the stator deposition (70c) having the field coil on a rear surface of the circuit board, guiding the terminals of the field coil (77, 78) from the rear surface to the front surface of the circuit board (30), soldering terminals of the field coil on the front surface of the circuit board (30), cooling the circuit board (30) to dissipate the heat generated by brazing, and the generating the reduction gear train (70b) on the rear surface of the circuit board (30).