Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1985-01-17
1987-03-03
Garrett, Robert E.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
91376A, 91459, F15B 907
Patent
active
046466215
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a hydraulic rotary actuator to be used for various kinds of industrial machines, instruments, and robots, and the use of this actuator can provide very compact driving parts for wrists (hands) and fingers of robots having such functions as selective positioning and control over power.
2. Background Art
With the prevalence of industrial robots in recent years, the application range of robots has become wider, and now intended is the use of robots for assembling operations with high precision and intricacy which has so far been deemed possible only by skilled workers.
However, an indispensable requisite for this purpose is to provide a manipulator possessing such functions as positioning and clamping with a high degree of freedom and high precision.
When an electrically driven actuator (DC servo, AC servo) is used, assembling of, for example, wrists and fingers having a high degree of freedom at the end of a multijoint arm of the robot is difficult because of the small power/weight ratio of a motor including reduction gears.
A hydraulic driving method using servo valves has widely been employed in the industrial field in the past but requires the provision of a pair of servo valves for each actuator.
Further, actuating oil must be separately fed to actuators and servo valves from the supply source and the structure of hydraulic pipe lines is complicated when a wrist with a high degree of freedom is provided.
When respective servo valves are provided in the body proper of a robot for reducing the weight thereof, pipe lines extending between hydraulic actuators incorporated in the wrist parts of the robot and servo valves are made very long. As a result, the servo system is unstable due to swelling of the pipes which are usually composed of resilient material, thereby causing a problem that loop gain governing the function of servo system cannot be made large.
A rotary actuator employing mechanical servos for controlling displacement, velocity, and power of the output shaft of the actuator pursuant to input signals has hitherto been used.
FIGS. 1a and 1b show a conventional type rotary actuator as mentioned above, having parts as follows:
input shaft 1; output shaft 2; guide valve sleeve 3; guide valve 4 comprising the abovesaid parts 1 and 3; setting piece 5; rotor vane 6; housing 7; supply and discharge openings for actuating oil; and packing 9 for sealing.
As shown in the drawing, the input shaft 1 is slidably received within the output shaft 2 and the guide valve 4 is formed between grooves on the surface of the input shaft 1 and other grooves on the inner surface of the guide valve sleeve 3 secured to the output shaft 2. When an angular deviation takes place between the input shaft 1 and the output shaft 2 of said actuator, the guide valve 4 opens by an amount proportional to the angular deviation and the motor generates torque in the direction in which deviation is compensated.
Then, the output shaft 2 revolves pursuant to rotation of the input shaft 1. When it is attempted to reduce the abovesaid rotary actuator in size for application thereof to, for example, a wrist and finger having a high degree of freedom, the following problems arise.
For miniaturization of the actuator, the configuration and size of the guide valve 4 composed of the input shaft 1 and the guide valve sleeve 3 must be reduced and, therefore, the groove of guide valve 4 which exerts a great influence on characteristics of the servo system is difficult to form.
A conventional structure similar to that as shown in FIGS. 1a and 1b, in which the input shaft 1 is contained within the output shaft 2 and the end of the input shaft 1 on one side extends outside the actuator, has had a problem that the sliding torque of the sealing packing 9 for prevention of oil leakage is large and miniaturization of the motor (not shown) for driving the input shaft 1 is impossible.
Further, an arrangement of uncovered piping for actuating oil to be fed to actuators causes problems, as in the case o
REFERENCES:
patent: 2917079 (1959-12-01), Verbrugge
patent: 2988059 (1961-06-01), Wysong, Jr.
patent: 4177713 (1979-12-01), Lewis et al.
patent: 4458580 (1984-07-01), Masuda et al.
Maruyama Teruo
Sekiguchi Takuya
Garrett Robert E.
Matsushita Electric - Industrial Co., Ltd.
Williamson Mark A.
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