JPH03182644A - Motor-driven actuator - Google Patents

Abstract

PURPOSE:To keep the torque of an output shaft to the fixed value by forming the bottom of the circumferential groove of a circular lever for winding a cable variably so that the radius of the circumferential groove becomes smaller in inverse proportion as the tension of a cable becomes larger than the specified value. CONSTITUTION:Two discs 6, 7 are connected by a center member 4A for receiving an output shaft, and between these discs 6, 7, the bottom of a groove 9 for receiving a cable 2 is formed of a plate spring 8. One end 8A of the plate spring 8 is fixed, and the other end 8b is to be the free end. The plate spring 8 is supported by a pin 7A so as not to be bent excessively. The plate spring 8 is bent when load is applied to the cable 2, and its winding radius is reduced as the tension of the cable 2 is enlarged. Accordingly, even a compact motor- driven actuator can be controlled stably while the torque of the output shaft of a motor is kept to the fixed value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an electric actuator for a constant speed traveling device for an automobile or the like.

[Background Art] In recent years, with the development of expressway networks, there are many opportunities to drive at a constant speed for long periods of time. For this reason, a constant speed traveling device has been developed that allows a vehicle to continue running at the same speed even when the foot is off the accelerator pedal, by inputting a desired speed into a control device.

The constant speed traveling device will be schematically explained with reference to FIG. In the figure, (10) is an electric actuator, (1
1) is the accelerator pedal, (12) is the throttle valve,
(13) is an engine, (14) is a control unit, and (15) is a control switch for a constant speed traveling device.

A transmission (13A) is connected to the engine (13), and a drive wheel is connected to the output shaft of this transmission (13A). Information about the speed of the car is given. Carburetor (12A) that supplies fuel to the engine (13)
A throttle valve (12) provided therein opens and closes the passage. This throttle valve (1
2) is spring biased back to the passage closing position. To increase the speed of the vehicle, depress the accelerator pedal (11) and rotate the first link (12B) of the throttle valve (12) clockwise in the figure via the cable (IIA) to connect the carburetor (12A).
to open more passageways. Accelerator pedal (1
1) returns to its initial position by a spring when the pedal is released, and the throttle valve (12) narrows the passage of the carburetor (12A) to reduce the speed of the vehicle.

A second link (12C) for a constant speed traveling device is connected to this throttle valve (12).

This second link (12G) is connected to an electric actuator (10) via a cable (2). As shown in FIG.
A second link (12) is attached to this circular lever (3).
The cable (2) from C) is connected. Thus, when the electric motor (IOA) rotates the circular lever (3) in the direction of the arrow, the cable (2) becomes wound around the circular lever (3), so that the cable (2) The second link connected to the other end (
12G) is tilted clockwise in FIG. 5, and the passage of the carburetor (12A) is widened. circular lever (3
) is turned in the direction opposite to the arrow, the cable (2) is pulled back by the spring of the throttle valve (12). Thus, the passage of the carburetor (12A) is narrowed.

When the constant speed traveling device is turned on by the control switch (15) and a desired speed is input, the control unit (14) compares the speed information from the transmission (13A) with the desired speed and (
2) controls the electric actuator (10) to wind up and unwind the circular lever (3).

The conventional circular lever (3) will be explained in more detail with reference to FIGS. 3(a) and 3(b). Circular lever (3)
has a hole (4) in the center for receiving the output shaft (IOB) to prevent it from rotating, and a groove (5) for receiving the cable (2) on the outer periphery. It consists of a press-molded product. Further, a pair of holes (IA) are provided on both side walls of the groove (5) for locking the cable end (1) of the cable (2).

[Problem to be solved by the invention]

Now, the tension of the cable (2) is the throttle valve (12).
) is small in the initial position of the throttle valve (12
) is large at the maximum opening position. The reason for this is due to the spring biasing the throttle valve (12) to its initial position. Therefore, the electric actuator (10)
The electric motor (IOA) is made large enough to generate a torque that can be hoisted against the maximum tension of the cable (2), and a reduction gear corresponding to the torque is used. This provided redundant provisions for the minimum tension of the cable (2) and thus resulted in an overall large electric actuator. This saves space, saves resources,
This goes against energy conservation, etc.

The present invention was made to solve these problems, and an object of the present invention is to provide a small electric actuator that can wind up a cable even if the tension of the cable, which is a load, increases as the cable is wound up. shall be.

[Means for Solving the Problems J] The electric actuator according to the present invention changes the diameter of the lever's circumference according to the load when a force exceeding a certain load is applied to the circumferential portion of the circular lever around which the cable is wound. In order to reduce this, the groove on the circumference of the circular lever was made elastically variable.

[Function] In this invention, when a force exceeding a certain load is applied when winding up the cable, the radius of the bottom of the circumferential groove decreases in inverse proportion to the load, so the output shaft that drives the circular lever Winding can be continued with constant torque.

[Embodiment] FIGS. 1 and 2 are diagrams for explaining a circular lever of an electric actuator according to an embodiment of the present invention. FIG. 1 is a partially cutaway perspective view of a circular lever;
FIG. 2 is a view showing the inside of the circular lever with one member removed and the radius of the groove on the circumference reduced.

In the figure, (2) is a cable, (4A) is a central member that receives the output shaft so that it does not rotate, (6) and (7) are disks connected by the central member (4A), and (8) is a A leaf spring (8) formed to form the bottom of a groove (9) for receiving the cable (2) between the two discs (6) and (7);
A) is the fixed end of the leaf spring (8), (8B) is the leaf spring (8)
The free end (7A) is a pin that supports the leaf spring (8) to prevent it from bending too much.

The leaf spring (8) is in the state shown in FIG. 1 under no load, and when loaded by the cable (2), bends as shown in FIG.

Of course, when the throttle valve (12) is brought to the open position by the accelerator pedal (11), the cable (
2) is substantially unloaded, so that when winding up such cable (2), the leaf spring (8) is not bent substantially as shown in FIG. This state occurs when the control switch (15) is turned on to switch to constant-speed traveling using the constant-speed traveling device after the accelerator pedal has been used to bring the vehicle almost to the desired speed.

Then, when the gas pedal is released, the cable (I
The tension in IA) is transferred to the cable (2) and the leaf spring (8)
is bent as shown in Figure 2. The control unit (14) compensates for the return of the throttle valve (12) according to the speed information from the transmitter (13A).

Now, the load torque applied to the output shaft (IOB) of the electric actuator from cable (2) is
The product T - r of the tension (T) and the radius (r) from the output shaft (IOB) to the point of application is the throttle valve. It goes without saying that (12) cannot be controlled, but since the radius (r) of the component of this torque T-r is smaller than the conventional one, according to the present invention, the electric motor (I
OA) and its reduction gear can be downsized as a whole.

In addition, in the present invention, the radius of the bottom of the groove (9) is made variable by the plate spring (8), so the versatility of this electric actuator is expanded. That is, it is widely used to wind cables with a lower maximum tension from a cable that produces the intended maximum tension.
It works in the optimum condition for the load. In other words, it can be driven with a constant output regardless of changes in the load.

In the conventional device, since the diameter of the groove in the circular lever was constant, the torque of the output shaft had to be increased as the load increased, resulting in poor controllability and durability.

A second embodiment of the invention will be described below. In this case, the leaf spring (8) is made of a bimetallic material made of two metal sheets. This bimetallic groove (9) increases when the ambient temperature increases.
) is bent in the direction that reduces the diameter. This is done in consideration of the characteristic that the output of the electric motor (IOA) decreases as the periodic temperature increases. In the past, a slightly larger electric motor was used in anticipation of a rise in temperature, but the present invention eliminates the need for such an increase in size.

[Effect of the invention 1] As explained above, in the present invention, the winding radius decreases as the cable tension increases, so the torque of the output shaft of the electric motor only needs to be constant, and even a small electric actuator can stably control it. There is an effect. Additionally, the winding radius decreases as the ambient temperature increases.
This has the effect of stably controlling even if the output of the motor decreases.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a circular lever of an electric actuator according to the present invention, and FIG. 2 is a partially cutaway perspective view of the circular lever of FIG. Figure 3 (a) shows a state in which the radius of the bottom of the
) is a partially cutaway perspective view of a circular lever of a conventional electric actuator, Figure 3(b) is a diagram showing a cable wound around the circular lever, and Figure 4 is a perspective view of a conventional electric actuator equipped with a circular lever. FIG. 5 is a perspective view showing the type actuator, and FIG. 5 is a schematic diagram for explaining the constant speed traveling device for an automobile. In the figure, (2) is a cable, (6) and (7) are disks connected by a central member (4A), (8) is a leaf spring,
(9) is a cable (2) between two discs (6) and (7).
) is the groove for receiving, (10) is the electric actuator,
(11) is an accelerator pedal, (12) is a throttle valve, (13) is an engine, (14) is a control unit, and (15) is a control switch.

Claims (2)

[Claims] (1) It has an output shaft that can be rotated forward and backward through a range of at most 360 degrees from an electric motor via a speed reducer, and has a circumferential groove around which a cable whose tension changes as it is wound is wound. In an electric actuator in which a circular lever is fixed to the output shaft, the radius of the circumferential groove of the circular lever around which the cable is wound becomes smaller in inverse proportion to the tension of the cable when it becomes larger than a predetermined value. An electric actuator characterized in that the bottom of the circumferential groove has a variable structure. (2) The electric actuator according to claim 1, wherein the variable structure of the groove is configured to reduce the radius of the circumferential groove in inverse proportion to an increase in ambient temperature.