Device for contact-connecting a circuit board

In a device (23) for contact-connecting two circuit boards (17, 18) for a control device of a throttle valve of an internal combustion engine of a motor vehicle, contacts (24, 25) of one of the circuit boards (17) are arranged on a holding part (20). The holding part (20) is prestressed toward contacts (25) of the other circuit board (18). The holding part (20) is connected to said one circuit board (17) via elastic connecting lines (22). Tolerance compensation is provided as a result of this. Furthermore the circuit boards (17, 18) are reliably contact-connected to one another.

BACKGROUND OF THE INVENTION
 The invention relates to a device for contact-connecting a circuit board of
 an electronic control device of an actuator, in particular of a throttle
 valve of an internal combustion engine of a motor vehicle, the control
 device and the actuator forming a structural unit with contacts arranged
 on a first structural part and with contacts which are connected to a
 second structural part and are conductively connected to the contacts of
 the first structural part.
 In the case of throttle valves used to regulate the power of the internal
 combustion engine of motor vehicles, usually one or a plurality of circuit
 boards of the electronic control device are arranged in a pot-shaped
 housing. The housing is produced in one piece with a throttle valve
 connector bearing the throttle valve and is closed off by a cover. The
 throttle valve connector has a flange for direct screwing to the internal
 combustion engine. Terminal contacts for the on-board electrical system
 and for signal lines are arranged in the cover. This results in a very
 compact construction for the throttle valve connector with all the
 structural parts required for regulating the power, such as the circuit
 boards and the cover with the terminal contacts.
 At their contacts, the circuit boards and the terminal contacts of the
 cover are electrically contact-connected to one another and to a
 servomotor for the throttle valve. Since the contact connection has to
 withstand high temperatures and vibrations, particularly in the case of
 the circuit boards which are fixed in the throttle valve connector, the
 contacts are usually connected to one another by laser welding. However,
 laser welding is very costly and leads to very cost-intensive assembly of
 the throttle valve connector.
 SUMMARY OF THE INVENTION
 The invention is based on the problem of configuring a device of the type
 mentioned in the introduction in such a way that the electrical connection
 of the contacts becomes as cost-effective as possible and that the
 connection subsequently withstands high temperatures and vibrations in a
 particularly reliable manner.
 This problem is solved according to the invention by virtue of the fact
 that the contacts of the second structural part are arranged on a holding
 part, that the holding part is prestressed toward the first structural
 part, and that the second structural part is connected to the holding part
 via elastic connecting lines.
 By virtue of this configuration, the circuit board is contact-connected in
 a region in which no mechanical loads act on the connection point.
 Therefore, vibrations do not lead to friction between the contacts and
 thus do not lead to the destruction of said contacts. Tolerances between
 the structural parts and movements of the structural parts relative to one
 another are compensated for by the connecting lines. As a result, the
 contact-making device according to the invention has particularly high
 reliability. Since no soldering points are necessary for the
 contact-making device according to the invention, said device is
 particularly suitable for use in internal combustion engines of motor
 vehicles.
 The prestressing of the holding part could be effected for example by a
 clamp arranged on the first structural part. However, fastening the clamp
 on the holding part necessitates an additional work operation when the
 structural parts are joined together. In accordance with an advantageous
 development of the invention, the prestressing of the holding part is
 effected without any additional outlay on assembly when the structural
 parts are joined together, if a spring element for prestressing the
 holding part toward the first structural part is arranged between the
 second structural part and the holding part.
 The device according to the invention becomes particularly cost-effective
 if the elastic connecting lines are formed by conductor tracks printed
 onto a sheet.
 The production of the holding part as a separate structural part leads only
 to an insignificant increase in the production costs of the device
 according to the invention if the holding part and the second structural
 part are produced from the same plastic and are connected to one another
 via a web which is thin in relation to their material thicknesses. In this
 case, the web may optionally serve as a desired breaking point between the
 second structural part and the holding part or be configured in an elastic
 fashion enabling the structural parts to move relative to one another.
 In accordance with another advantageous development of the invention, a
 movement of the holding part relative to the first structural part can be
 avoided in a simple manner if the holding part has guide pins and the
 first structural part has holes corresponding to the guide pins.
 In accordance with another advantageous development of the invention, the
 holding part is reliably prestressed toward the first structural part if
 the second structural part has a guide element for the spring element.
 The device according to the invention becomes particularly simple in
 structural terms if the spring element is a helical spring and the guide
 element is a sleeve.
 By way of example, the contacts could be configured as contact laminae in
 each case. For the purpose of contact connection, mutually opposite
 contact laminae could be perpendicularly prestressed toward one another.
 However, in order to avoid friction between the contacts, this
 configuration requires very high prestressing forces and particularly
 accurate guidance of the holding part relative to the first structural
 part. Friction between the contacts would lead to the electrically
 conductive connection being destroyed. However, in accordance with another
 advantageous development of the invention, friction between the contacts
 can be avoided in a simple manner if the contacts of the second structural
 part are in pin form and the contacts of the first structural part are
 prestressed laterally toward the contacts of the second structural part.
 The lateral prestressing can be effected in a very simple manner by virtue
 of appropriate shaping of the contacts of the first structural part.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 FIG. 1 shows a throttle valve connector 1 with a load adjusting apparatus
 2. The load adjusting apparatus 2 has an actuating shaft 4 penetrating
 through a duct 3. A throttle valve 5 serving to regulate a free
 cross-sectional area of the duct 3 is fastened on the actuating shaft 4.
 The actuating shaft 4 is swiveled by an actuating gear mechanism 7
 arranged in a pot-shaped housing 6 of the throttle valve connector 1.
 Furthermore, a control device 8 for driving an electric motor (not
 illustrated) is arranged in the housing 6. The electric motor enables the
 actuating gear mechanism 7 to be driven and thus the actuating shaft 4 to
 be swiveled. The pot-shaped housing 6 of the throttle valve connector 1 is
 closed off by a cover 9.
 The throttle valve connector 1 has two bearings 10, 11 for the actuating
 shaft 4. An actuating lever 12 is fastened to that end of the actuating
 shaft 4 which is opposite to the actuating gear mechanism 7. An emergency
 running spring 13 and a restoring spring 14 are arranged concentrically
 around the bearing 11 of this end of the actuating shaft 4. The restoring
 spring 14 and the emergency running spring 13 are each configured as leg
 springs and arranged in a well-like housing 15. The housing 15 is closed
 off by a cover 16.
 The control device has two circuit boards 17, 18 arranged one above the
 other. Arranged in the cover 9 is a socket 19 by means of which the
 control device 8 is connected to an on-board electrical system (not
 illustrated) of the motor vehicle for power supply and/or for data
 exchange purposes (for example via a CAN bus). The two circuit boards 17,
 18 are electrically connected to one another by means of a device 23
 according to the invention. A holding part 20 is arranged between the two
 circuit boards 17, 18. The holding part 20 is prestressed by a spring
 element 21--designed as a helical spring--toward the upper circuit board
 18 and is connected to the lower circuit board 17 by means of elastic
 connecting lines 22.
 FIG. 2 illustrates the device 23 according to the invention in a greatly
 enlarged manner in a partial section through the holding part 20 and a
 partial region of the upper circuit board 18. The electrical connecting
 lines 22 are routed as far as contacts 24 arranged on the holding part 20.
 The contacts 24 of the holding part 20 are connected to contacts 25 of the
 upper circuit board 18. In this case, the contacts 25 of the upper circuit
 board 18 are prestressed laterally toward the contacts 24 of the holding
 part 20. Furthermore, FIG. 2 shows that the spring element 21 is guided
 vertically by a guide element 26 designed as a sleeve. The holding part 20
 has guide pins 27 and the first structural part or circuit board 18 has
 holes corresponding to the guide pins 27.
 It goes without saying that the device according to the invention can also
 be used to contact-connect the socket 19 illustrated in FIG. 1 to the
 electronic control unit 8.
 LIST OF REFERENCE SYMBOLS
 1. Throttle valve connector
 2. Load adjusting apparatus
 3. Duct
 4. Actuating shaft
 5. Throttle valve
 6. Housing
 7. Actuating gear mechanism
 8. Electronic control unit
 9. Cover
 10. Bearing
 11. Bearing
 12. Actuating lever
 13. Emergency running spring
 14. Restoring spring
 15. Housing
 16. Cover
 17. Circuit board
 18. Circuit board
 19. Socket
 20. Holding part
 21. Spring element
 22. Connecting line
 23. Device
 24. Contact
 25. Contact
 26. Guide element
 27. Guide pin