JPH0254460B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a continuously variable transmission.

An object of the present invention is to use a variable displacement pump as a hydraulic power source for controlling a continuously variable transmission, control the pump discharge flow rate by a set circuit pressure that can be arbitrarily set using a linear solenoid, and discharge only the minimum necessary flow rate. This is to improve energy efficiency.

In the hydraulic system of conventional continuously variable transmissions, the hydraulic pump always discharges a predetermined amount Q, but it actually works effectively when the speed change cylinder is displaced in some way. When other shift cylinders are maintained at a certain position with a certain pressing force, the hydraulic pump bypasses the relief valve to maintain the required pressure P even though the shift cylinders are not performing any work. It does work (P×Q) for the flow rate, and all of it is converted into energy such as heat and wasted, resulting in a very wasteful state in terms of energy efficiency.

The present invention has solved such conventional problems, and its feature, as described above, is that a variable displacement pump is used as the hydraulic source, and the pump discharge amount is controlled by a circuit pressure that can be set arbitrarily by a linear solenoid. That's true. Hereinafter, specific embodiments of the present invention will be described based on the drawings.

In Figure 1, 1 is the primary pulley on the input side, 2
is the secondary pulley on the output side. The primary pulley 1 has a conical fixed belt pulley 9a on an input shaft 3 driven by an engine or the like, and a movable belt pulley 9a integrated with the primary transmission cylinder 5, which is relative to the fixed belt pulley 9a only in the axial direction. A piston 7 is provided at the end of the input shaft 3 and is displaceably fitted into the primary transmission cylinder 5 .

One secondary pulley 2 has a conical fixed belt pulley 10a on the output shaft 4, and a movable belt pulley 10b integrated with the secondary transmission cylinder 6 and a fixed belt pulley 10a.
A piston 8 is provided at the end of the output shaft so as to be relatively displaceable only in the axial direction. and,
A V-belt 1 is installed between the primary pulley 1 and the secondary pulley 2.
1 is multiplied and rotational force is transmitted from the input side to the output side, and the movable belt pulleys 9b and 10b are mutually displaced in the axial direction by the primary and secondary transmission cylinders 5 and 6, respectively, so that the transmission ratio can be changed steplessly. to control.

Reference numeral 12 denotes a variable displacement pump of a hydraulic source that controls the continuously variable transmission having the above-mentioned configuration, and is driven by the input shaft 3, but can also be driven by the output shaft 4. The discharge port of this variable displacement pump 12 is connected to the primary and secondary speed change cylinders 5 and 6, and the electromagnetic flow valve 13 is provided in the connection circuit of the primary speed change cylinder 5. In this _IA control of the electromagnetic flow valve 13, pressure oil is supplied to the primary transmission cylinder 5, which has a larger pressure receiving area, so that the piston 7 moves to the left, and accordingly, the piston 8 also moves to the left to reduce the gear ratio. In the _IB control, the primary transmission cylinder 5 is communicated with the tank, so that the pistons 8 and 7 move to the right to increase the transmission ratio.

As shown in FIG. 2, the variable displacement pump 12 has a plurality of vanes 15 in a pump casing (not shown), a rotor 14 that is rotationally driven by the input shaft 3 or the output shaft 4, and the rotor 14. surrounding the
A radially movable cam ring 16 and a first balance spring 18 biasing the cam ring 16 to a maximum eccentric position ε with respect to the rotor 14.
and a balance piston 20, which is provided with a second balance spring 19 that presses the cam ring 16 in opposition to the bias of the first balance spring 18, and which moves forward and backward in contact with the cam ring 16. . 17 is a support pin of the cam ring 16, 2
5 is a discharge port, and 26 is a suction port. This discharge port 25 is connected to the primary and secondary transmission cylinders 5 and 6 of the continuously variable transmission.

Further, the front chamber 21a of the balance piston 20
and the rear chamber 21b and the discharge port 25 are connected,
An orifice 22 is provided in the circuit connected to the front chamber 21a. Further, a pilot relief valve 23 is provided in the exhaust circuit of the front chamber 21a to set the circuit pressure by a linear solenoid 24 to which a control current according to the gear ratio of the continuously variable transmission is applied.

Since the present invention is configured as described above, when the pilot relief valve 23 is fully closed, the same pressure oil is guided to the front and rear chambers 21a and 21b of the balance piston 20, so that the cam ring 16 is connected to the balance springs 18 and 19. It is at the maximum eccentric position of the balance point, and the maximum discharge flow rate occurs. From this state, when the set pressure according to the control current of the linear solenoid 24 is reached, a certain flow is generated in the orifice 22 due to the leakage of pressure oil from the pilot relief valve 23, and the front chamber 21a of the balance piston 20 is correspondingly increased. pressure decreases, balance piston 2
0 reduces the amount of eccentricity of the cam ring 16 according to the differential pressure. As a result, the discharge flow rate of the variable displacement pump decreases, and the driving force due to the differential pressure of the balance piston 20 and the balance springs 18 and 19 are balanced and stopped at a new balance point. Further, the increase or decrease of the gear ratio of the continuously variable transmission is performed by controlling I _A and I _B of the electromagnetic flow valve 13.

In this state, the variable displacement pump maintains the required pressure by discharging the amount corresponding to the leakage from each part and the relief flow rate from the pilot relief valve 23. Furthermore, when the primary and secondary pistons 7 and 8 move forward, the consumption flow rate increases temporarily, but
At that time, as the pistons 7 and 8 move forward, the circuit pressure decreases and the relief flow rate decreases, so the differential pressure between the front and rear chambers 21a and 21b of the balance piston 20 decreases, and the eccentricity of the cam ring 16 increases. Therefore, the pump discharge flow rate increases and the circuit pressure is compensated. When the pistons 7 and 8 complete their movement, they return to the original balanced position and the pump discharge flow rate decreases.

As described above, according to the present invention, regardless of the rotational speed of the variable displacement pump, at any rotational speed, the minimum pump discharge is sufficient to generate the necessary pressure in the hydraulic circuit that controls the continuously variable transmission. It controls the flow rate, and has the effect of providing energy-efficient continuously variable transmission control, and also has the effect of arbitrarily controlling the circuit pressure using a linear solenoid.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a diagram of a continuously variable transmission and its control circuit, and FIG. 2 is a main structural diagram of a variable displacement pump. 1...Primary pulley, 2...Secondary pulley, 3...
Input shaft, 4... Output shaft, 5, 6... Speed change cylinder, 7, 8... Piston, 11... V-belt, 1
2... Variable displacement pump, 13... Electromagnetic flow valve, 14... Rotor, 15... Vane, 16...
Cam ring, 18, 19... Balance spring, 20... Balance piston, 22... Orifice, 23... Pilot relief valve, 24...
Linear solenoid, 25...Discharge port, 26...
...Intake port.

Claims (1)

[Claims] 1 It has a primary pulley on the input side and a secondary pulley on the output side, power is transmitted between these conical belt wheels by a V belt, and the conical belt wheels are connected to each other by the primary and secondary speed change cylinders, respectively. It consists of a continuously variable transmission that continuously controls the gear ratio by displacing in the direction, and a variable displacement pump that supplies pressure fluid to the primary and secondary transmission cylinders of this continuously variable transmission. A rotor having a plurality of vanes and rotationally driven by the input or output shaft of the continuously variable transmission, a cam ring that surrounds the rotor and is movable in the radial direction, and the cam ring is placed at a maximum eccentric position with respect to the rotor. a first balance spring that biases; a balance piston that moves the cam ring forward and backward in opposition to the bias of the first balance spring; and a balance piston that acts on the balance piston to bias the first balance spring. a second pressing the cam ring in the opposite direction;
a balance spring, which connects the discharge port of the variable displacement pump to the primary and secondary transmission cylinders of the continuously variable transmission, and connects the discharge port to the front and rear chambers of the balance piston, respectively; An orifice is arranged in a circuit connecting the front chamber of the chamber and the discharge port,
A continuously variable transmission characterized in that a front chamber of the balance piston is communicated with a tank via a pilot relief valve whose relief pressure is set by a linear solenoid controlled according to a gear ratio of the continuously variable transmission. Control device.