This invention is directed to electromagnetic solenoid actuators, and more particularly to improvements in both rotary and linear actuators having either fixed or variable axes.

Objects of the present invention are to provide improvements in construction of solenoid actuators of both rotary and linear types, and of both variable axis and fixed axis types, which achieve improved efficiency as compared with rotary and linear actuators characteristic of the prior art by minimizing inductance losses in the actuator structure, improving heat dissipation characteristics, and/or increasing the ampere-turn/ copper-mass ratio and thereby achieving a given power output using less copper material than in the prior art.

Another object of the invention is to provide rotary and linear actuators which achieve reduced size and cost for a given output power and stroke requirement as compared with prior art devices.

A further object of the invention is to provide improvements in rotary and linear actuators which achieve enhanced operating speed and efficiency as compared with the prior art by eliminating any requirement for electromagnetic flux reversals in the actuator stator and armature structures, and/or by reducing or eliminating parasitic eddy currents.

Yet another object of the invention is to provide variable axis solenoid actuators of either the rotary or linear type which achieve high power or torque output at the beginning of the armature stroke as is typically desirable for efficient operation of external devices, and/or substantially uniform output power during the remainder of the stroke.

This invention is directed to electromagnetic solenoid actuators, and more particularly to improvements in actuators having either fixed or variable axis.

In general, solenoid actuators which are characteristic of the prior art possess either fixed or variable air gaps between the associated stator and armature structures. For example, the above-noted parent and copending applications of the inventor herein disclose a number of fixed and variable axis actuators in which air gap, i.e. the distance between the associated armature and stator structures, varies with armature stroke. The solenoid actuators so disclosed are very efficient in terms of output force versus actuator weight and/or versus input power. However, the characteristic or function of actuator output force versus stroke distance is not as constant as desired in these and other variable air gap actuators.

U.S. Pat. No. 4,097,833 discloses a number of solenoid actuators in which the air gap between the armature and stator poles remains constant with armature stroke due to the fact that the opposing stator and armature faces are parallel to the stroke direction. However, the solenoid actuators so disclosed are not as efficient as desired, and the force versus stroke characteristic thereof undesirably decreases at the end of the armature stroke.

It is therefore an object of the present invention to provide improvements in construction of solenoid actuators which achieve improved efficiency in terms of reduced size and cost for a given output power or stroke requirement as compared with actuators characteristic of the prior art.

Another and more specific object of the invention is to provide solenoid actuators which exhibit high output power at the ends of the armature stroke as is typically desirable for efficient operation of external devices, and which exhibits a substantially constant power versus stroke characteristic for the remainder of the stroke.

The present invention is directed to actuators for obtaining linear motion at an output shaft or the like, and more particularly to linear actuators for obtaining incrementally indexed motion over long strokes in one or both axial directions.

BACKGROUND AND OBJECTS OF THE INVENTION

Linear indexers, also known as linear stepper motors, have heretofore been proposed in the art for obtaining precisely incrementally controlled linear motion at an output shaft or the like. In particular, electromagnetic actuators of the described character have comprised a shaft carrying a series of magnets and cooperating with a series of stator assemblies for electromagnetically incrementing or indexing the magnets and shaft through the stator assemblies. Linear indexers of this type are expensive to fabricate and assemble. Moreover, the length of stroke is necessarily limited by the number of magnets and stator assemblies, with cost and size increasing rapidly with stroke length. Holding power, which is a function of electromagnetic attraction between the magnets and energized stator assemblies, has severely limited application of this technology.

It is a general object of the present invention to provide a linear actuator, particularly an actuator for obtaining incrementally indexed linear motion, which is inexpensive to manufacture and implement, which can be readily and accurately controlled over an unlimited length of stroke, and which obtains high holding power with limited energy input. A further and more specific object of the invention is provide an electromagnetic linerally indexing actuator of reduced cost and size, and suitable for use in precision control of electronic functions in an automotive vehicle, such as precision control of the pintle in an EGR valve of a vehicle emission system, or in power-assisted electronic vehicle applications such as power steering or braking.

SUMMARY OF THE INVENTION

In general, the foregoing and other objects of the invention are obtained by providing a linear actuator which includes a shaft mounted for linear motion in the direction of its axis. A disc is slidably mounted on the shaft and carries a pivotal latching mechanism which has a central aperture embracing the shaft. Mechanism is provided for incrementally moving the disc in the direction of the shaft axis, during which motion the latch is pivoted with respect to the shaft axis so that the aperture which embraces the shaft effectively grips the shaft and moves the shaft axially conjointly with the disc. A spring, specifically a pair of spring washers, surround the shaft between the indexer and disc, with the concave side facing the disc and the convex side engaging the indexer for applying uniform force on the central portion of the indexer and thereby assisting the pivoting and shaft-gripping action thereof. An abutment is positioned on a side of the latch opposed to the disc, and the spring washers urge the latch against the abutment in the de-energized or deactivated positions of the disc and latch. The latch surface opposing the abutment is sloped to accommodate pivotal motion of the latch during initial disc motion without interference with the abutment.

In an actuator for obtaining incrementally indexed linear motion, a pair of such discs and latches, with associated abutments and spring washers, are mounted in tandem along the shaft. The discs are alternately energized, with one disc remaining energized for latching the shaft in position while the other disc is de-energized, returned to its initial position, and then re-energized for incrementing shaft position. Mechanism for returning the shaft to its initial position may comprise a coil spring against which the discs and latches operate, or a second pair of oppositely acting discs and latches for incrementing shaft position in the opposite direction.

In the preferred embodiments of the invention, the discs comprise armatures in a pair of electromagnetic actuator assemblies positioned serially of the shaft. A coil spring urges each armature/disc and its associated latch against the opposing latch abutment. The coils of the stator assemblies are connected to energizing electronics which are responsive to pulsed input command signals for alternately energizing the stator coils. The coil-drive electronics include facility for sensing current in each stator coil, and for energizing the other coil when the actuator associated with the first coil moves to its fully-energized position. In this way, maximum velocity consistent with shaft load is obtained. In an alternative embodiment of the invention, a fluid actuator includes pistons having the latch-carrying discs forming parts thereof. The fluid cylinder is coupled to a controlled fluid supply for incrementally activating the pistons and indexing the shaft in either direction.