JPS60101351A - Control device of continuously variable transmission - Google Patents

Abstract

PURPOSE:To prevent overrun in a simple structure by operating a ratio control valve in direction of decreasing a torque transmission ratio by overrun preventing means when an engine rev count is more than a preset value. CONSTITUTION:A belt type continuously variable transmission mechanism 6 has a torque transmission ratio change fluid actuator 10 comprising cylinders 7, 8 mounted on input and output pulleys 1, 3. The discharged oil of a fluid pump 9 is supplied to one cylinder 7 through pressure regulating valves 11, 14. A signal fluid from a ratio control valve 15 for controlling the supply of pressurized oil to the cylinder 7 is applied to the pressure regulating valve 14 to work in direction of decreasing a torque transmission ratio. A car velocity signal fluid PG from an overrun preventing valve 16 is applied to the valve 15 in direction of decreasing a torque transmission ratio, and the valve 16 is adapted to open when a car velocity signal fluid PG is more than a designated value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a continuously variable transmission mounted on a vehicle, and particularly to measures to prevent engine overrun.

(Prior art) Conventionally, the continuously variable transmission of this scale was developed in JP-A-52-9.
As disclosed in Japanese Patent No. 8861, a continuously variable transmission mechanism of a bell 1 set that transmits power between input and output shafts and whose torque transmission ratio changes steplessly, and a fluid that changes the torque transmission ratio of the continuously variable transmission mechanism. a hydraulic actuator, and a ratio control valve to which a signal fluid is applied without indicating the running state of the vehicle and which adjusts the supply of working fluid to the hydraulic actuator,
It is known that the torque transmission ratio is continuously and variably controlled depending on the driving condition of the vehicle.

By the way, the continuously variable transmission as described in -1- is equipped with an overrun prevention mechanism to prevent the engine from being rotated by the driving wheels and overrunning at a predetermined rotation speed when traveling in both directions on a downhill slope. There is a need.

Therefore, as in the case of a stepped automatic transmission, by detecting the engine overrun state and controlling the 1st torque transmission ratio to a smaller value (shifting the gear ratio to the higher gear side),
It is possible to prevent engine overrun. However, in this case, if the overrun prevention is performed mechanically or by separately providing a hydraulic control mechanism, the mechanism will be complicated.

(Object of the Invention) In view of the above, an object of the present invention is to detect an engine overrun state while utilizing as much as possible the existing control mechanism that variably controls the torque transmission ratio of a continuously variable transmission. The goal is to control the torque transmission ratio to a small value, which is a relatively simple method to prevent engine overrun.

(Structure of the Invention) In order to achieve the above object, the structure of the present invention includes a continuously variable transmission groove in which transmission is transmitted between the input and output shafts and the torque transmission ratio changes steplessly as described above, and a continuously variable transmission mechanism. It consists of a hydraulic actuator that changes the torque transmission ratio, and a ratio control one-roll valve that is supplied with a signal fluid indicating the running state of the vehicle and adjusts the supply of working fluid to the hydraulic actuator,
In a continuously variable transmission in which the torque transmission ratio is variably controlled according to the vehicle's driving conditions, it detects that the engine speed has reached a set value and acts on the ratio control valve to reduce the torque transmission ratio. The engine overrun prevention means is equipped with an engine overrun prevention means for raising the signal fluid, and when the engine speed reaches a set value, the engine overrun prevention means operates the ratio control valve in the direction of decreasing the torque transmission ratio. .

(Effects of the Invention) Therefore, according to the present invention, when the engine speed reaches the set value, the existing ratio control valve operates in the direction of decreasing the torque transmission ratio, thereby preventing engine overrun. Engine overrun prevention can be reliably performed with a relatively simple configuration without complicating the hydraulic control circuit for variable torque transmission control, etc., thereby improving the reliability of engine overrun prevention and reducing costs. ()l I! It is something that can be achieved.

(Example) Hereinafter, embodiments of the present invention will be briefly described with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a belt type continuously variable transmission A. In the figure, 1 is a primary pulley that is provided on the input shaft 2 and is composed of a fixed flange 1a and a movable flange 1b that is movable in the axial direction with respect to the fixed flange 1a, and 3 is a primary pulley that is provided on the output shaft 4. The secondary pulley is provided with a fixed flange 3a and a movable flange 3b which is movable in the axial direction with respect to the fixed flange 3a. A transmission metal belt means 5 is wound around these primary and secondary pulleys 1 and 3.
A belt-type continuously variable transmission mechanism 6 is constructed in which the torque is transmitted between the input and output shafts 2.4 by the belt means 5, and the torque transmission ratio changes steplessly.

A fluid cylinder 7.8 is formed at the back of the movable flange 1b, 3b of each of the pulleys 1, 3, and each of the fluid cylinders 7.8 is connected to a fluid pump 9. By supplying working fluid to each fluid cylinder 7.8 and moving the movable flanges 1b, 3b of each pulley 1, 3, the effective pitch diameter of each pulley 1, 3 is made variable, and the continuously variable transmission mechanism 6 is A fluid actuator 1o configured to change the torque transmission ratio is configured.

Further, a pressure regulating valve 11 is interposed between the fluid cylinder 8 of the secondary pulley 3 and the fluid pump 9,
The pressure regulating valve 11 receives a vehicle speed signal fluid P from a governor valve 12 that generates a vehicle speed signal fluid Pc that changes depending on the vehicle speed.
C, and from the throttle 1 health opening sensor valve 13 which detects the engine load by the throttle opening in opposition to the vehicle speed signal fluid Pc and generates a load signal fluid that changes according to the engine load. A load signal fluid PT is added, and the pressure of the working fluid supplied to the fluid cylinder 8 of the secondary pulley 3 is adjusted according to the running condition of the vehicle (II speed and engine load). 1 to control the tension of the means 5. In addition, vehicle speed signal fluid Pc
, may be a signal fluid that changes depending on the engine speed. Further, a pressure regulating valve 14 is interposed between the pressure nof adjustment 'jt11 and the fluid cylinder 7 of the primary pulley 1.
Ratio control valve 15 which regulates the supply of working fluid to the fluid cylinder 7 of the primary pulley 1 via the 4 force)
These signal fluids are added so as to act in the direction of decreasing the torque transmission ratio. Furthermore, while the vehicle speed signal fluid Pc from the Ganokusu valve 12 is applied to the ratio control valve 15 in the direction of reducing the torque transmission ratio (high gear side), the vehicle speed Continuously variable transmission in which a signal fluid P'T indicating the driving condition is applied to the low gear side (to increase the torque transmission ratio), thereby variably controlling the changes transmitted by torque according to the driving condition of the vehicle. Machine A is configured.

As a feature of the present invention, the vehicle speed signal from the engine overrun prevention valve 1G that allows or blocks the flow of the vehicle speed signal fluid Pc is transmitted in the direction (high gear side) in which the torque loss transmission ratio of the ratio control valve 15 is reduced (i.e., to the high gear side). Fluid P(,
has been added to make it work. As shown in detail in FIG. 2, the engine overrun prevention valve 1G is configured such that the vehicle speed signal fluid Pc is supplied to the inlet boat 17 and also opposes one spring that urges the spool 18 to the left in the figure. 2. When the skew signal fluid Pc is acting on the spool 18 and the medium speed signal fluid Pc is at a pressure value other than PGMAX corresponding to the maximum vehicle speed VO, the spool 18
The land 18a closes the inlet port 17 to cut off the flow of the vehicle speed signal fluid Pc, and allows the exit boat 20a to pass through the discharge port 21). On the other hand, vehicle speed signal fluid Pc
When is at the pressure value PGMAX corresponding to the maximum medium speed VO, conversely, the pressure PC, MAX moves the spool 1B to the right in the figure against the biasing force of one spring,
The land 18a closes the discharge boat 21 and connects the inlet boat 17 to the outlet port 20b. ! By allowing the flow of Shintan fluid PGMAX, it is detected that the engine speed has reached the setting 1*Ro corresponding to the maximum vehicle speed vO as shown in the shift characteristics in Figure 3, and the ratio control valve 15 is The engine overrun prevention means 22 is configured to raise the signal fluid that acts in the direction of reducing the torque transmission ratio.

Therefore, in the above embodiment, the vehicle speed is the highest value Vo
When the engine speed reaches the set value Ro, the engine overrun prevention valve 16 causes the car communication signal fluid PGMAX to act on the ratio control valve 15, and the ratio control valve 15 reduces the torque transmission ratio. By operating the high gear side), the gear ratio shifts to the high gear side and engine overrun is prevented.

Here, the existing ratio control valve 15 is used as a means for shifting the gear ratio to the high gear side, and the only new means to be provided is the engine overrun prevention valve 16, which leads to complication of the hydraulic side 611 circuit, etc. Therefore, the overrun prevention mechanism can be constructed relatively easily, thereby improving operational reliability and reducing costs.

Incidentally, in the above embodiment, the case where the belt-type continuously variable transmission is applied is described, but the present invention is also applicable to various other continuously variable transmissions such as the IQ single-type transmission.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall schematic diagram, FIG. 2 is a specific circuit diagram of the main parts, and FIG. 3 is a vehicle speed-engine rotation speed diagram showing shift characteristics. △...Continuously variable transmission, 2...Input shaft, 4...Output shaft, 6...Continuously variable transmission base, 10...Fluid actuator, 15...Register A"control valve , 22...
Engine overrun prevention means.

Claims (1)

[Claims] (1) A continuously variable transmission mechanism that transmits power between the input and output shafts and whose torque transmission ratio changes steplessly, a fluid actuator that changes the torque transmission ratio of the continuously variable transmission mechanism, and a signal that indicates the running state of the vehicle. In a continuously variable transmission, which includes a ratio control valve to which fluid is added and which adjusts the supply of working fluid to the hydraulic actuator, the torque transmission ratio is variably controlled depending on the vehicle running condition. A control device for a continuously variable transmission, comprising engine overrun prevention means that detects that a set value has been reached and increases a signal fluid that acts on the ratio control valve in a direction to reduce the torque transmission ratio.