Throttle valve control apparatus using DC torque motor

Details Throttle valve control apparatus using DC torque motor Throttle valve control apparatus using DC torque motor

2000-10-13

2001-11-20

Waks, Joseph (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Oscillating

C310S254100, C251S129120

Reexamination Certificate

active

06320285

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a small-sized, light-weight DC torque motor which has good response characteristics and is simple to control, a drive control apparatus using the DC torque motor and a throttle valve control apparatus for an internal combustion engine.
2. Description of the Related Art
Conventionally, there has known a torque motor being rocked within a predetermined working angle range. For example, as shown in
FIG. 11
, Japanese Unexamined Patent Publication 6-6964 discloses a DC torque motor
100
consisting of a needle
101
rockable around axis
103
and a generally U-shaped stator
102
with a cavity disposed between them, wherein the needle
101
is composed of a soft iron core
104
and two permanent magnets
105
,
106
fixedly attached to the periphery of the core
104
, and the stator
102
has polarity portions
109
,
110
facing to each other and coil
112
is wound around the proximal portion of the stator
102
(the upper part in FIG.
11
).
In the above-specified DC torque motor and the like, torque is designed to be almost constant irrespectively of degree of angle within a predetermined angle range on condition that the current flowing in the coil is set constant. That is, the torque is designed to be flat to any angles within the predetermined angle range. For example, the above-mentioned publication discloses a DC torque motor capable of securing constant torque with constant flowing of current at almost entire ratable positions for the needle.
However, section area of the stator
102
(section area of magnetic path) needs to be large so as to achieve such characteristics. The stator
102
is affected by magnetic fields of the permanent magnets
105
,
106
fixedly attached to the needle
101
and a magnetic field generated by current flowing in the coil
112
. However, directions of the above-stated magnetic fields may sometimes coincide with each other, which depends on angle a of the needle
101
. Under such a condition, since the stator
102
is made of soft magnetic material such as soft iron, once fluxoid quantum is saturated, the fluxoid quantum does not increase greatly even when current flows in the coil. As a result, torque becomes low in proportion to a variation of the fluxoid quantum. Therefore, section area of magnetic path needs to be made large to avoid saturation of the fluxoid quantum.
However, as the section area of magnetic path for the stator
102
is enlarged, dimensions, volume, weight of the stator
102
increase proportionally. Further, in case that a DC torque motor is controlled by angle of its shaft (rocking angle) &agr;, large torque is required at the initial rocking so that the DC torque motor can be rocked within a large angle range to obtain high response characteristics. However, large torque is not required at the near-to-end rocking. Further, considerably high torque is not required for the DC torque motor to be rocked by a small angle.
SUMMARY OF THE INVENTION
The present invention has been made in light of the above problems. Therefore, an object of the present invention is to provide a small-sized, light-weight DC torque motor with good responsibility characteristics, a drive control apparatus using the same and a throttle valve control apparatus for use in, for example, an internal combustion engine.
To obtain the above-stated object, a moving magnet type DC torque motor rocked in a predetermined working angle range according to the present invention, is preferably characterized in that, while it is assumed that current, angle and torque satisfy the following relationship that: if current in positive direction is applied, the direction of angle at which the DC torque motor is rocked is positive and the direction of torque developed at this moment is positive; and if current in negative direction is applied, the direction of angle at which the DC torque motor is rocked is negative and the direction of torque developed at this moment is negative; wherein the motor has following angle-torque characteristics that positions of torque peaks among the torque in positive direction developed by the constant current in the positive direction spread in a low angle region among the working angle range, and positions of torque peaks among the torque in negative direction developed by the constant current in the negative direction spread in a high angle region among the working angle range.
The DC torque motor having the above-stated structure according to the present invention (to be simply referred to as ‘motor’ hereinafter) has the following angle-torque characteristics if the directions of the current, angle and torque are set as described above.
First, a case where the motor is rocked in (positive) direction in which angle increases is considered. In this case, if the motor is rocked greatly, that is, if the motor is rocked from a low angle &thgr;1 to a high angle &thgr;2 (&thgr;1<<&thgr;2) as in a case where the motor is rocked from the lower limit of the working angle range to the upper limit thereof, positions of torque peaks unevenly spread in the low angle region. Due to this, at a low angle, i.e., at the beginning of the motor operation, high torque can be obtained and the motor can be promptly accelerated. In addition, if angle increases, i.e., the motor is near to a stop position, the torque thus developed is lower. In other words, although the motor is rocked by high angle (&thgr;2−&thgr;1), the motor can be rocked to a desired angle &thgr;2 promptly and smoothly.
Meanwhile, if the motor is to be rocked to a less degree, an angular variation is small and response speed is not so influential. Accordingly, high torque is not required. Therefore, if the motor is to be rocked from a high angle &thgr;3 to a slightly higher angle &thgr;4 (&thgr;3<&thgr;4), torque peaks unevenly spread in the low angle region, which does not, however, adversely affect control operation.
Next, a case opposite to the above case, i.e., a case where the motor is to be rocked in (negative) direction at which angle decreases.
In this case, if the motor is rocked to a large degree, i.e., if the motor is rocked from a high angle &thgr;5 to a low angle &thgr;6 (&thgr;5>>&thgr;6) as in a case where the motor is rocked from the upper limit of the working angle range to the lower limit thereof, torque peaks unevenly spread in a high angle region. Due to this, at high angle &thgr;, that is, at the beginning of motor operation, high torque can be obtained and the motor can be, thereby, accelerated promptly. Also, if angle decreases, that is, if the motor is near the stop position, the torque thus developed is lower. In other words, although the motor is rocked by high angle (&thgr;5−&thgr;6), the motor can be rocked to a desired angle &thgr;6 promptly and smoothly.
Meanwhile, if the motor is to be rocked to a less degree, high torque is not required and an angular variation is small. Accordingly, response speed is not so influential. Due to this, if the motor is to be rocked from a low angle &thgr;7 to a slightly lower angle &thgr;8 (&thgr;7>&thgr;8), positions of torque peaks unevenly spread in the high angle region, which does not, however, adversely affect control operation.
In other words, if angle is to be changed greatly, high torque sufficient to accelerate the motor can be developed and good response characteristics can be obtained. If angle is changed less greatly, torque developed may be low. The low torque does not, however, adversely affect control operation.
To obtain the above-stated object, in the inventive DC torque motor comprising a stator with coil wound therearound, and a needle including permanent magnets, the needle being rocked within a predetermined working angle range, it is preferable that magnetic path is formed within the stator, fluxoid quantum the permanent magnets and current flowing in the coil generate within the stator is not saturated while the working angle of the needle is in a repulsion region where the needle repuls

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