Motor vehicles – Power – Electric
Reexamination Certificate
1999-01-13
2001-05-15
Mai, Lanna (Department: 3619)
Motor vehicles
Power
Electric
C180S907000, C180S065510, C318S060000, C318S445000
Reexamination Certificate
active
06230831
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a power-assisted wheelchair wherein the assist power commensurate with the human power applied to right and left wheels is applied to each wheel so that the wheel is driven for rotation with the sum of the human power and the assist power.
TECHNICAL BACKGROUND
Such a power-assisted wheelchair is situated between the manual wheelchair and the motor-operated wheelchair. The human power applied intermittently to the paired right and left wheels is detected, and assist power commensurate with the detected human power is added respectively to the right and left wheels to alleviate the physical effort of the rider.
Here, with this kind of power-assisted wheelchair, the assist power is supplied intermittently every time the human power applied to each wheel is detected. After the human power is removed, the assist power is caused to attenuate with the lapse of time to provide the wheelchair rider with a coasting impression (Refer to the JP(A) Hei-
8-168506
).
However, the conventional power-assisted wheelchair so far has had problems: the time-attenuation rate of the assist power is set to be always constant irrespective of the magnitude of the human power and the running speed or the running direction (forward or reverse). As a result, on a road surface having a small running resistance, the running continues more than expected when the coasting amount is too great for example, and the turning radius cannot be made small for the small indoor movements. When the coasting amount is insufficient on the contrary, running is not easy on the road having a large running resistance or on a steep slope.
Also there are cases in which, when the wheelchair negotiates a step or the like, the wheelchair ends up in coasting farther than expected.
Furthermore, coasting of the wheelchair in the reverse direction causes unnecessary impression of fear to the rider. When the coasting amount is insufficient on the contrary, even if human power is applied to the wheels in the reverse direction or to counter the wheel rotation on a steep downhill for example with the intention of producing brake forces, stabilized brake forces may not be produced.
Therefore, the object of this invention is to provide a power-assisted wheelchair capable of making small radius indoor running, comfortable outdoor running, easy uphill running, stabilized downhill running, and eliminating the impression of fear during a reverse running.
SUMMARY OF THE INVENTION
To accomplish the above-described object, the invention of claim
1
is directed to a power-assisted wheelchair having an electric motor for producing assist power, means for detecting the human power applied to the right and left wheels, and means for controlling the electric motor according to the human power detected with the human power detecting means, the assist power commensurate with the human power detected with the human power detecting means being applied to each wheel to drive the wheel for rotation, characterized in that the control means controls the electric motor to produce the assist power when the human power is detected with the human power detecting means and at the same time to attenuate the assist power with the lapse of time, with the time-attenuation rate of the assist power changed according to running conditions.
The invention of claim
2
according to claim
1
is characterized in that the time-attenuation rate of the assist power is changed according to the magnitude of the human power.
The invention of claim
3
according to claim
2
is characterized in that the time-attenuation rate of the assist power is set to be greater as the human power is smaller, and to be smaller as the human power is greater.
The invention of claim
4
according to claim
2
or
3
is characterized in that the time-attenuation rate of the assist power may be optionally adjusted with an adjustment switch.
The invention of claim
5
according to claims
1
through
4
is characterized in that the power-assisted wheelchair is provided with means for detecting the running speed and means for detecting the running direction and that the time-attenuation rate of the assist power at least during the forward running is changed according to the magnitude of the running speed.
The invention of claim
6
according to claim
5
is characterized in that the time-attenuation rate of the assist power during the forward running is set to be greater as the running speed is smaller, and to be smaller as the running speed is greater.
The invention of claim
7
according to claim
5
or
6
is characterized in that the time-attenuation rate of the assist power in the reverse direction during the reverse running is set to be equal to or greater than that in the forward direction during the forward running.
The invention of claim
8
according to claim
5
,
6
, or
7
is characterized in that the time-attenuation rate of the assist power in the reverse direction during the forward running is set to be smaller than that of the assist power in the reverse direction during the reverse running.
The invention of claim
9
according to claims
1
through
8
is characterized in that the power-assisted wheelchair is provided with means for detecting the running speed, means for detecting the running direction, and speed deviation detecting means for storing the running speed at the time of the removal of the human power applied to the wheel and comparing it with a current running speed to detect a deviation between the two speeds, and that the time-attenuation rate of the assist power is changed according to at least one of the speed deviation and the time-integrated value of the speed deviation.
The invention of claim
10
according to claim
9
, characterized in that the time-attenuation rate of the assist power is set to be greater as at least one of the speed deviation and the time-integrated value of the speed deviation is greater, and is set to be smaller as the value is smaller.
Therefore, with the invention of claims
1
through
4
, a required coasting amount is secured according to the running condition of the wheelchair. Specifically, since the time-attenuation rate of the assist power is made greater as the human power is smaller, the coasting amount of the wheelchair is kept small for the small indoor-movements for example, small-indoor movements with a small turning radius are possible, and the convenience for the rider is improved. Also, since the time-attenuation rate of the assist power is made smaller as the human power is greater, a sufficient coasting amount is secured for the outdoor running, so that a comfortable running on a level road is made possible and at the same time a steep uphill running is made easy to alleviate the physical effort of the rider.
With the invention of claim
1
,
5
, or
6
, a necessary coasting amount is secured according to the running condition of the wheelchair. Specifically, since the time-attenuation rate of the assist power is set to be greater as the running speed is smaller, and to be smaller as the running speed is greater, the coasting amount of the wheelchair is kept small for the small-indoor movements for example, small indoor movements with a small turning radius are possible, and the convenience for the rider is improved. At the same time, a comfortable outdoor running is possible with sufficient coasting amount being secured. Furthermore, in the case the wheelchair negotiates a step or the like, since the running speed is low, the time-attenuation rate increases. As a result, the wheelchair is prevented from coasting farther than anticipated after the negotiation and the rider is provided with an impression of stability.
With the invention of claim
7
, since the time-attenuation rate of the assist power in the reverse direction during the reverse running is set to be equal to or greater than that in the forward direction during the forward running, the wheelchair does not coast excessively and no unnecessary impression of fear is caused to the rider.
With the invention of claim
Ogata Hiroaki
Tokura Kenji
Beutler Ernest A.
Mai Lanna
Olson & Bear LLP
Restifo Jeffrey
Yamaha Hatsudoki Kabushiki Kaisha
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