Planetary gear transmission systems or components – Input from independent power sources – One-way clutch or brake in drive train
Reexamination Certificate
2001-05-25
2003-03-25
Estremsky, Sherry (Department: 3681)
Planetary gear transmission systems or components
Input from independent power sources
One-way clutch or brake in drive train
C475S010000, C475S269000, C475S324000, C475S325000
Reexamination Certificate
active
06537169
ABSTRACT:
TECHNICAL FIELD
This invention relates to an automatic transmission for vehicles which accomplishes non-stage transmission using a double pinion planetary gear.
BACKGROUND ART
An automatic transmission for vehicles has been provided which comprises a torque converter and a planetary gear combined with the torque converter. The torque converter increases the torque developed by an engine. However, a range of increase in the torque is so small that the automatic transmission is insufficient to be used singly in automobiles. Accordingly, in the practical use, the automatic transmission is combined with a plurality of planetary gears so that one of a plurality of reduction gear ratios for the planetary gears is automatically selected according to a driving condition.
However, since the reduction gear ratio is stepwise shifted according to the driving condition in the above-described automatic transmission, gear shift during acceleration results in a large shock and momentarily reduces the number of revolution of the engine. As a result, the vehicle cannot smoothly be accelerated. Further, the reduction gear ratio is suddenly increased when the automatic transmission is downshifted according to the operation of an accelerator so that the vehicle is accelerated. As a result, the vehicle body is shaken such that a driver and passengers may feel uncomfortable. Even when the accelerator is returned for deceleration, the automatic transmission is not downshifted but would sometimes be upshifted by contraries. As a result, the engine brake cannot effectively be applied.
Further, the torque converter disadvantageously has a large transmission loss, and in addition, the transmission loss is further increased since a plurality of planetary gears are used. Further, the overall automatic transmission has a complicated structure and is large in size and heavy in weight. Thus, the automatic transmission increases the weight of the vehicle and the size of a driving system thereof. Further, since the planetary gears are controlled by means of oil hydraulics, the loss resulting from production of oil pressure is large. Additionally, the oil pressure control is complicated and accordingly increases the cost and results in failure.
In addition, when a driving force of drive wheels is smaller than the current running resistance of the vehicle, the current number of revolution cannot be maintained or the engine causes knocking which results in uncomfortableness. Further, since the vehicle cannot be accelerated, the automatic transmission is controlled so that such a reduction gear ratio is selected that the vehicle runs under a condition where the driving force of the drive wheels is sufficiently large according to the speed of the vehicle relative to the running resistance. In other words, while the vehicle is running at a constant speed, the reduction gear ratio is larger than an optimum one at which the driving force of the drive wheels equilibrates the current running resistance, whereupon fuel is consumed uselessly.
On the other hand, a belt continuously variable transmission (CVT) utilizing pulleys and a belt has recently been put to practical use. In the belt CVT, the belt couples two pulleys and diameters of both pulleys are changed so that the reduction gear ratio is continuously variable. Accordingly, since non-stage transmission can be accomplished, gear shift results in no shock such that the vehicle can smoothly be accelerated. However, the belt has a low durability in the currently used belt CVT, whereupon it is difficult to apply the current belt CVT to high-powered engines. Further, since the diameters of the pulleys are varied by the oil hydraulics so that the reduction gear ratio is adjusted, an increase rate of the engine speed does not agree with an acceleration rate of the vehicle even though the engine speed is increased according to the operation of the accelerator. This results in a sense of physical disorder and a large loss in the engine revolution for production of oil pressure. Further, the belt which is originally annular is elastically deformed into an elliptic shape when attached to the pulleys. The slippage between the pulleys and the belt or the loss due to the aforesaid deformation is large. Further, the belt CVT results in a delay time between a sudden change of load or engine power and gear shift. As a result, the belt CVT is unsuitable for the sports driving. Further, even though the CVT can accomplish the non-stage transmission, it is controlled so that such a reduction gear ratio is selected that the vehicle runs under a condition where the driving force of the drive wheels is sufficiently large according to the speed of the vehicle relative to the running resistance, as in the same manner in the aforesaid automatic transmission. As a result, fuel is wasted.
On the other hand, no transmission is provided in electric railcars with an electric motor serving as a driving source and electric motorcars. In these vehicles, a motor voltage and a motor current are controlled by an inverter so that the motor torque and speed are controlled according to a running speed of the vehicle. However, the cost for such a control device is extremely high. Further, the control device carries out a control manner in which the driving force of the drive wheels becomes larger than the running resistance of the vehicle so that the vehicle can run smoothly. This results in waste of the electric power. Additionally, since the motor torque and speed are controlled according to the speed of the vehicle, the driving force of the drive wheels would become unsuitable depending upon load applied to the drive wheels or the motor would be overloaded.
Bicycles are provided with a transmission manually shifting a reduction gear ratio. The manual operation is troublesome and the transmission cannot generally be shifted while the bicycle is stopped. Thus, the transmission is not effectively used in the bicycle. Further, wind power generating systems are provided with no transmission. Accordingly, a generator is not rotated when torque due to wind power is smaller than a stationary force of the generator, so that no electric power is produced. Further, when the torque due to wind power is larger than a torque required to maintain the generation in the generator, the torque due to wind power cannot efficiently be transmitted to the generator, whereupon the generating efficiency is low.
DISCLOSURE OF THE INVENTION
Therefore, an object of the present invention is to provide an automatic transmission which has a small size and a simple construction, causes no shock due to gear shift, and can convert input rotation to output rotation at a maximum efficiency with no control.
The present invention provides an automatic transmission comprising an input first rotating member, an output second rotating member provided to be coaxial with the first rotating member, a third rotating member provided to be coaxial with the first rotating member, and a rotation transmitting element provided on the third rotating member to transmit rotation of the first rotating member to the second rotating member so that the second rotating member is rotated at a predetermined reduction ratio exceeding 1 in a direction of rotation of the first rotating member in a stopped state of the third rotating member. The reduction ratio is increased as a difference between rotational speeds of the first and third rotating members is rendered larger. In this construction, the third rotating member is bidirectionally rotatable. The second rotating member is automatically adjusted to a number of revolution at which an equilibrium is maintained between torque developed by the second rotating member and a load applied to the second rotating member when the third rotating member is in rotation at a number of revolution ranging between zero at which the third rotating member is stationary and a number of revolution at which the third rotating member is in rotation together with the first rotating member in one and the same direction.
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