JPH01283470A - Continuously variable transmission for vehicle - Google Patents

Abstract

PURPOSE:To enable the restraining of creep torque at a low level via simple control by setting a gear change limit region in the low gear ratio side of a continuously variable transmission device at least in a fine throttle opening or less. CONSTITUTION:In the gear change region of a continuously variable transmission device 20 set within an electronic control device 47, there is provided a gear change limit region shown by a hatching area A. As a result, the continuously variable transmission device 20 is unable to shift a gear from an intermediate gear ratio to a low gear ratio in a fine throttle opening, and as a throttle opening B increases, the gear change limit region gradually becomes small. Finally, it becomes possible to shift a gear over the entire range of a lowest gear ratio to a maximum gear ratio at the throttle opening of 2/4 or more. By setting the gear change limit region as aforementioned, the continuously variable transmission device 20 is maintained at an intermediate gear ratio during idling as in creeping, and creep torque generated by a torque converter 3 is not amplified by the continuously variable transmission device 20. Consequently, creep torque transmitted to an axle becomes small.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a continuously variable transmission for a vehicle, and particularly to a continuously variable transmission for a vehicle in which an engine output shaft is connected to the continuously variable transmission via a starting mechanism that generates creep force. This relates to a gear transmission.

[Prior art and its problems]

Conventionally, starting mechanisms that generate creep force include torque converters, fluid couplings such as fluid cup links, centrifugal clutches, and even automatic clutches that automatically control creep torque using hydraulic clutches! Two proposals have been made (for example, Japanese Patent Laid-Open No. 60-241530).

In this type of start-up, the creep torque of fluid couplings and centrifugal clutches changes in a quadratic manner depending on the engine speed, so there is a problem that the creep torque becomes excessive at high engine speeds such as when idling up. . Also, in the case of an automatic clutch, how can I keep the creep torque constant when idling up? 3 [91i] electronic control and hydraulic control are required, and various highly accurate sensors are required, which has the disadvantage of high cost.

In addition, when the vehicle is stopped, which generates creep torque, the continuously variable transmission is always maintained at the maximum gear ratio <m low speed ratio), so the creep torque generated by the starting mechanism is amplified by the continuously variable transmission and transmitted to the axle. This is one of the causes of large leap torque.

[Purpose of the invention]

The present invention has been made in view of the above problems, and an object thereof is to provide a continuously variable transmission for a vehicle that can suppress creep torque to a low level by simple control without controlling a starting mechanism.

[Structure of the invention]

In order to achieve the above object, the present invention provides a continuously variable transmission with the following features:
A speed change restriction area is provided on the low speed ratio side at least below the minute throttle opening.

[Effect]

That is, since the throttle opening is closed during idling in the driving range, the continuously variable transmission has a speed change control range on the low speed ratio side, in other words, it is maintained at an intermediate speed ratio. Therefore, the creep torque generated by the starting mechanism is not amplified by the continuously variable transmission, and no large leap torque is transmitted to the axle.On the other hand, when the throttle opening is opened to start, the continuously variable transmission does not respond to the low speed ratio as usual. , so starting performance is not impaired.

[Embodiment] FIG. 1 shows an example of a continuously variable transmission for a vehicle according to the present invention.

An output shaft 2 of the engine 1 drives a pump impeller 4 of a torque converter 3, which is an example of a side engine 1a, and a turbine runner 5 is connected to an input shaft 10. Further, the stator 6 is connected to a fixed portion 8 via a one-way clutch 7. A lock-up clutch 9 connected to one end of the input shaft 10 is disposed inside the torque converter 3.

At the other end of the input shaft 10 is a planetary gear type forward/reverse switching mechanism 11.
is provided. This forward/reverse switching mechanism 11 includes a ring gear 12 connected to an input shaft IO, a sun gear 13 connected to a drive shaft 21 of a continuously variable transmission 20 (described later), and a planetary gear 14 meshing with the ring gear 12 and the sun gear 13. Carrier 15 supporting planetary gear 14
A forward clutch 16 is disposed between the carrier 15 and the drive shaft 21, and a reverse brake 18 is disposed between the carrier 15 and the fixed portion 17. When the forward clutch 16 is engaged and the reverse brake 18 is released, the ring gear 12. Sun gear 13. When the carrier 15 rotates integrally and enters a forward drive state, and the forward clutch 16 is released and the reverse brake 18 is engaged, the ring gear 12 and sun gear 13 rotate in reverse, resulting in a backward drive state.

The continuously variable transmission 20 includes a drive-side boot IJ provided on the drive shaft 21.
22, a driven pulley 24 provided on the driven shaft 23, and a V-belt 25 wound between both pulleys.

The drive pulley 22 has a fixed sheave 22a and a movable sheave 22.
A gear ratio control oil chamber 26 for controlling the gear ratio is provided behind the movable sheave 22b. On the other hand, similarly to the driving pulley 22, the driven pulley 24 has a fixed sheave 24a and a movable sheave 24b, and behind the movable sheave 24b is a load thrust that provides the V-belt 25 with the thrust necessary for torque transmission. A control oil chamber 27 is provided. The oil pressure in the gear ratio control oil chamber 26 and the load thrust control oil chamber 27 is controlled by control valves 40 and 41, which will be described later.

A reduction gear 28 is fixed to the end of the driven wheel 23,
This reduction gear 28 is connected to a ring gear 33 of a differential device 32 via a gear 30.31 of a countershaft 29, and the differential device 32 transmits power to two output shafts 34.35.

The speed change control valve 40 and the load thrust control valve 41 have TH and S
Signal oil pressures P□, P are input from the IT valves 42 and 43, and the oil pressures p, , according to the signal oil pressures P□, P are input to the gear ratio control oil chamber 26 and the load thrust control oil chamber 27. It supplies p8. The oil pump 44 discharges the hydraulic oil sucked from the oil reservoir 45 to the regulator valve 46, and the regulator valve 46 regulates the discharge pressure to the line pressure PL, and controls the control valves 40, 41 and T! It is output to 1 magnetic valve 42 and 43. The electromagnetic valves 42, 43 are duty-controlled by the electronic control device 47, and adjust the output oil pressures P, , P2 of the control valves 40, 41 by continuously changing the signal oil pressure P□+P11 according to the duty ratio. , controls the gear ratio and load thrust of the continuously variable transmission 20.

In the above configuration, the electronic control device 47 is set with a shift control pattern according to each driving range and mode.
A target value for the engine speed or gear ratio is determined in accordance with driving signals such as throttle opening and vehicle speed, and the gear change control solenoid valve 42 is controlled so that the actual engine speed or gear ratio approaches the target value. It is outputting a signal.

FIG. 2 shows the speed change range of the continuously variable transmission 20 set within the electronic control unit 47. As shown in FIG. That is, the shaded area in the figure is the speed change restriction area, and the continuously variable transmission 20 cannot shift from the intermediate speed ratio to the lower speed ratio at a minute throttle opening, and as the throttle opening increases, the speed change restriction area gradually narrows. When the throttle opening degree is 274 or more, the speed can be changed over the entire range from the lowest speed ratio (Low) to the highest speed ratio (Illight).

By setting the speed change range in this way, the continuously variable transmission 20 is maintained at an intermediate gear ratio during idling such as during creep, and the creep torque generated by the torque converter 3 is amplified by the continuously variable transmission 20. First, the creep torque transmitted to the axle is small, so even if the torque converter 3 generates a large torque such as when idling up, problems such as the vehicle jumping out can be eliminated.

In addition, in FIG. 2, the speed change restriction area may be provided only below the minute throttle opening, but in this case, the gear ratio of the continuously variable transmission 20 may change greatly due to a slight change in the throttle opening. Therefore, as shown in FIG. 2, the speed change limit range is set to change gradually according to the throttle opening.

Fig. 3 shows a shift diagram when traveling is started according to the shift range shown in Fig. 2. In Fig. 0, if the throttle opening θ is less than 2/4, starting is started from an intermediate gear ratio. Therefore, the engine starts slowly and the throttle opening θ is 274.
In the above case, since the vehicle starts starting from the lowest speed ratio (Low) as before, it is possible to realize an agile start. In this way, the starting characteristics can be changed by changing the throttle opening.

In addition, in the above embodiment, a torque converter was used as the starting mechanism, but a fluid coupling was used instead.

Centrifugal clutch or intransitive? A hydraulic clutch may be used.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, the continuously variable transmission device has a speed change restriction region on the low speed ratio side at a minute throttle opening or less. When the range is idling, the continuously variable transmission maintains a gear ratio smaller than the lowest gear ratio.
Since the creep torque generated by the starting mechanism is not amplified by the continuously variable transmission and no large leap torque is transmitted to the axle, it is possible to prevent the vehicle from jumping out even when idling up.

[Brief explanation of the drawing]

FIG. 1 is a skeleton diagram showing the configuration of the continuously variable transmission for a vehicle according to the present invention, FIG. 2 is a diagram showing the shift range set in the electronic control device, and FIG. 3 is a shift diagram in the present invention. . l...engine, 2...engine output shaft, 3...
Torque converter, 11... Forward/forward switching mechanism, 20.
... Continuously variable transmission, 40... Speed change control valve, 42...
Solenoid valve, 47...electronic control device. Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 2 Figure 3 Hosoku

Claims (1)

[Claims] A continuously variable transmission for a vehicle in which an engine output shaft is connected to a continuously variable transmission via a starting mechanism that generates a creep force, wherein the continuously variable transmission A continuously variable transmission for a vehicle, characterized by having a speed change limit region on the low speed ratio side.