Adjustment Device for Rotary Angle Adjustment

The invention is based on an adjustment device of the type described by the preamble to the main claim. Adjustment devices of this kind, in known forms of embodiment, are realized as reversable electromotors having a subsequent gear drive and a potentiometer for the detection of the adjustment angle as a feedback value for a followup amplifier, which furnishes the supply voltage for the electromotor. If a throttle device in a bypass around the throttle valve of an internal combustion engine is to be adjusted with an adjustment device of this kind, for instance to effect closed-loop control of the idling rpm of the engine, then at the present time not only are strict demands placed on the electric/electronic portion of the adjustment device but the control of the bypass cross section must be made as precise as possible, because regulations concerning exhaust composition are becoming more and more stringent and the need to conserve fuel is ever more apparent.

The adjustment device according to the invention having the characteristics of the main claim has the advantage over the prior art that a very precise control can be attained for the cross section of the bypass.

As a result of the characteristic disclosed in the dependent claim, an advantageous modification of and improvement to the adjustment device disclosed in the main claim can be attained. As a result, the infiltrated-air component is kept as small as possible by simple means.

The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment taken in conjunction with the drawings.

FIG. 1 shows in schematic form an adjustment device disposed in a bypass around the throttle valve in the intake tube of an internal combustion engine;

FIG. 2 is a longitudinal cross-sectional view taken through an adjustment device; and

FIG. 3 is a cross-sectional view taken along the line III--III of FIG. 2.

In FIG. 1, air for combustion flows in the direction of the arrow through an intake tube 1 past a throttle valve 2 to an internal combustion engine, not shown. A bypass line 3 communicates with the intake tube 1, bypassing the throttle valve 2; the passageway cross section of this bypass line 3 is variable by means of an adjustment device 4, which actuates a throttle device 5. The adjustment device 4 is triggered by an electronic control device 6 having various inputs applied at the following locations: the supply voltage is applied at 7; the signal for the rpm, which is picked up by the ignition distributor, is applied at 8; the signal for the engine temperature is applied at 9; and a voltage characterizing the position of the throttle valve 2, supplied for example by a potentiometer connected to the throttle valve 2, is applied at 10.

In FIG. 2, the adjustment device 4 is shown in section. The adjustment device 4 is provided with a cap 13, which axially limits the adjustment device 4 at one end and is embodied as an integrally cast part together with a portion 14 of the bypass line 3 with the portion 14 arranged to surround the corresponding portion of the bypass 15. The other end of the adjustment device 4 remote from the cap 13 is limited by a cover cap 16. A tubular housing 17 furnishes the connection between the cap 13 and the cover cap 16. A shaft 21 is rotatably supported on one end in a slide bushing 19 in the portion 14 of the bypass line and on the other end in a slide bushing 20 in the cover cap 16. This shaft 21 is firmly connected with an armature 22 of the servomotor of the adjustment device 4. In order to cause the revisible 90.degree. rotary movement, two coils 24, 25 are provided in the grooves 23 of the armature 22, the coils 24, 25 being displaced by 90.degree. from one another and being wound in opposite directions. The two coils 24, 25 are triggered by the control device 6 in a known manner by direct-current pulses whose variable pulse ratios have a certain relationship to one another, so that the armature 22 assumes a position, in the magnetic field produced by two segmental permanent magnets 26, which corresponds to the pulse ratio. The adjustment device 4 is connected to an electric source by means of a flat plug 28 having three insertion prongs 29. The insertion prongs 29 are connected by strips 30 with flat plugs 31 at the circumference of an insulation carrier 32, which is guided in the housing 17 in a non-rotationally fixed manner. One flexible conductor loop 33 is connected with each of the three flat plugs 31, which are displaced relative to one another by 120.degree. each. The conductor loops 33 each lead in a radial direction to a coil body 34 and are in electrical contact there with a fork-like contact shoe 35. The coil body 34 is firmly connected with the shaft 21. The contact shoes 35 are connected on the other end with the ends of the coils 24, 25. As a result of the cyclic triggering of the adjustment device 4, frictional resistance is reduced.

The throttle device 5, embodied as a rotary slide, is firmly connected with the shaft 21 and, with one control portion 37 each, passes with limited play through the cap 13 and the bypass 15. Depending on the position of the rotary slide 5, the control portion 37 opens the bypass 15 to a greater or lesser extent.

The interior of the housing 17 communicates with the atmosphere. Because the play between the rotary slide 5 and the bore 40 in the cap 13 or the bypass line 14 cannot be made arbitrarily small, infiltrated air flows through this area of play when the engine is in operation, as a result of the pressure drop between the atmospheric pressure in the housing 17 and the underpressure downstream of the rotary slide 5. This infiltration of air causes an undesired impairment of the control process. In order to keep this infiltrated-air component as small as possible, a sealing disc 41 having an aperture 42 is loosely guided on the shaft 21 between the armature 22 and the rotary slide 5; the diameter of the sealing disc 41 is larger than the diameter of the rotary slide 5. A sealing face 43 is machined into the cap 13 against which the sealing disc 41 can rest with its face oriented toward the rotary slide 5. Now, if during operation of the engine an underpressure prevails in the bypass portion downstream of the rotary slide 5, then this underpressure is extended, via the play between the bore 40 and the circumference of the rotary slide 5, into a chamber 45 located between the rotary slide 5 and the sealing disc 41. Thus a pressure drop prevails between the chamber 45 and the interior of the housing 17 which presses the sealing disc 41 against the sealing face 43; as a result, leakage air can enter only through the substantially smaller leakage cross section between the circumference of the shaft 21 and the aperture 42 in the sealing disc 41.

The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other embodiments and variants thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.