JP2000018352A - Toroidal type continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toroidal type continuously variable transmission which can stabilize a pilot pressure by offsetting change in the pilot pressure mutually caused by the valve opening/closing operation of a pair of solenoid valves for supplying a control pressure to the control valve for controlling a speed change ratio. SOLUTION: In order to control the spool or sleeve position of a control valve for controlling the displacement of the slant rolling axis direction of a tranion for supporting the power roller of a toroidal type continuously variable transmission rotatably, the controlled pilot pressure Pp is supplied to both ends of the control valve by the duty signals Da, Db outputted to a pair of solenoid valves. By operating the start and finish point of time of the electrification of the duty signals Da, Db by which a pulse width is modulated substantially and simultaneously (t1, ta1,...) and the open valve and close valve reversely, the pilot pressure Pp is stabilized by offsetting the change in response to the open/close operation of the solenoid valve mutually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applicable to a power transmission section of a vehicle or the like, and is a toroidal in which the rotation of an input shaft is steplessly changed via a tiltable power roller and output to an output shaft. The present invention relates to a continuously variable transmission.

[0002]

2. Description of the Related Art Conventionally, as a toroidal type continuously variable transmission,
A set or a plurality of toroidal transmission units including an input disk driven by the input shaft, an output disk disposed opposite to the input disk and connected to the output shaft, and a power roller frictionally contacting both disks are provided on the same shaft. 2. Description of the Related Art Toroidal-type continuously variable transmissions arranged in sets are known.

As such a toroidal-type continuously variable transmission, as shown in FIGS. 3 and 4, for example, a so-called double-cavity toroidal-type continuously variable transmission in which two sets of toroidal transmission portions are arranged on the same shaft. There is something called a machine. FIG. 3 is a schematic view of a double-cavity toroidal type continuously variable transmission, and FIG. 4 is a diagram showing a speed ratio control hydraulic mechanism of the double-cavity toroidal type continuously variable transmission shown in FIG.

In the double-cavity toroidal type continuously variable transmission shown in FIG. 3, two sets of toroidal transmission portions 1 and 2 are symmetrically arranged on a main shaft 3. The toroidal transmission unit 1 is provided with an input disk 4, an output disk 5 arranged opposite to the input disk 4, and a friction member disposed between the input disk 4 and the output disk 5 and having a toroidal curved surface on both disks 4, 5. And a power roller 6 to be engaged. The toroidal transmission unit 2 includes an input disk 7, an output disk 8, and a power roller 9, similarly to the toroidal transmission unit 1. Each of the toroidal transmission units 1 and 2 is provided with two power rollers 6 and 9, respectively. Each of the power rollers 6 and 9 is rotatable about its own rotation axis 10, and is capable of tilting about a tilt axis 11 (perpendicular to the plane of FIG. 3) perpendicular to the rotation axis 10.

[0005] The input shaft 13 is arranged on the same axis as the main shaft 3, and power from the engine is input to the input shaft 13 via a torque converter (not shown). The input disk 4 can be displaced in the axial direction of the main shaft 3 via the ball spline 12 and can rotate integrally with the main shaft 3. The torque of the input shaft 13 generates a thrust force that presses the input disk 4 against the power roller 6 by the cam action of the cam roller 15 of the loading cam 14 disposed at the tip of the input shaft 13 in the toroidal transmission unit 1. When this thrust force is generated, the loading cam 14
The reaction causes the main shaft 3 via the thrust bearing 19.
Is pulled toward the input shaft 13. As a result, in the toroidal transmission 2, the input disk 7 connected to the main shaft 3 is pressed against the power roller 9. Therefore, the power rollers 6, 9 are sandwiched between the input disks 4, 7 and the output disks 5, 8, and contact portions between the power rollers 6, 9 and the input disks 4, 7, and the output disks 5, 8 are provided. Generates a frictional engagement force corresponding to the magnitude of the transmission torque. A part of the torque of the input shaft 13 is transmitted from the input disk 4 to the output disk 5 via the power roller 6, and the remainder is transmitted from the input disk 7 of the toroidal transmission unit 2 to the power roller via the ball spline 12 and the main shaft 3. 9 and transmitted to the output disk 8.

In the toroidal transmission units 1, 2, the power rollers 6, 9 are tilted around the tilt shaft 11, and the radius of the frictional contact point of the power rollers 6, 9 with the input disks 4, 7 and the output disk 5, , 8 changes the ratio of the radius of the frictional contact point to the radius of the frictional contact point, so that the rotation of the input disks 4, 7 is transmitted to the output disks 5, 8 while being steplessly shifted according to the tilt angle θ. The power rollers 6, 9 are rotatably and swingably supported by the trunnions 33, 37, and can cope with the axial displacement of the main shaft 3 caused by the thrust force. The flange portion 16 provided at the tip of the input shaft 13 and the loading cam 14 are connected by a meshing portion 17 formed by pawls. The distal end 18 of the input shaft 13 rotatably supports one end of the main shaft 3 via a bearing 29. Loading cam 1
A disc spring 21 for pressing the input disks 4 and 7 against the power rollers 6 and 9 even when no input torque is applied is disposed between the shaft 4 and the flange 20 provided at one end of the main shaft 3. ing.

The output disks 5 and 8 respectively have a hollow shaft portion 23 and a spline integrally extending from the gear body of the output gear 22 on both sides so as to transmit the torque from the power rollers 6 and 9 and rotate together. Mated. The output gear 22 is rotatably supported by a casing 25 via an angular bearing 24 and has a main shaft 3.
It is also arranged to be rotatable with respect to. The output disks 5 and 8 are provided with spacers 26 on the side surface on the output gear 22 side.
The position in the thrust direction is determined by abutting the inner ring of the angular bearing 24 through the shaft. The output gear 22 is taken out to a counter shaft (not shown) via a transmission (not shown) such as a chain transmission or a gear transmission. The axis directly connected to the main shaft 3 or the counter axis is
This is the output shaft of the toroidal type continuously variable transmission. The main shaft 3
There is an oil passage 27 formed to extend in the axial direction, and an oil passage 27 for supplying lubricating oil to each contact portion and rotating portion.
Oil passage 28 that penetrates radially from
Are formed.

[0008] The tilting of the power rollers 6, 9 around the tilt axis 11 is obtained by offsetting the power rollers 6, 9 in the axial direction of the tilt axis 11. That is, at the neutral position where the rotation axis 10 of the power rollers 6 and 9 intersects with the axis of the main shaft 3, the tilt angle θ of the power rollers 6 and 9 maintains the state at that time, and the gear ratio changes at that time. Maintained at the value. During the torque transmission, the trunnion 33,
When the roller 37 is offset in the axial direction of the tilt shaft 11 together with the power rollers 6, 9, the contact positions of the power rollers 6, 9 with the input disks 4, 7 and the output disks 5, 8 are displaced from the contact positions at the neutral position. Therefore, the power rollers 6, 9 are connected to the input disks 4, 7 and the output disks 5,
From 8, a tilting force to rotate around the tilting shaft 11 is received in a direction and a speed corresponding to the moving direction and the moving amount of the tilting shaft 11.

The tilting control of the power rollers 6 and 9 of the toroidal type continuously variable transmission 1 is performed by a gear ratio control hydraulic mechanism of the toroidal type continuously variable transmission by hydraulic pressure shown in FIG. The tilt control of the power rollers 6 and 9 is performed by controlling the trunnions 33 and 3 so that the target gear ratio is achieved, as described later.
7 is controlled by controlling the displacement of the tilting shaft 7 in the axial direction.
As shown in the figure, a pair of power rollers 6 and 9 are respectively provided with pivot shafts 35 and 39 oscillatingly provided on trunnions 33 and 37, and eccentric shafts 36 eccentric with respect to the pivot shafts 35 and 39, respectively. It is rotatably supported by rotating support shafts 34 and 38 having 40. In addition, trunnions 33, 37
Is provided so as to be movable in the axial direction of the tilt shaft 11 with respect to the casing 25 of the transmission and to be rotatable about the tilt shaft 11.

[0010] Hydraulic actuators 41 and 44 are disposed on the tilt shafts 11 of the trunnions 33 and 37, respectively. The hydraulic actuator 41 includes a piston 42 fixed to the trunnion 33. The casing 25 includes, in the casing 25, a cylinder composed of two cylinder chambers partitioned by the piston 42, ie, a cylinder chamber 43A on the deceleration side and a cylinder chamber 43B on the speed increasing side. A chamber 43 is formed. Similarly, the hydraulic actuator 44 is connected to the piston 4 fixed to the trunnion 37.
The casing 25 has two cylinder chambers defined by a piston 45, that is, a cylinder chamber 46 including a deceleration-side cylinder chamber 46A and a speed-increasing cylinder chamber 46B.

A control valve for controlling the speed ratio of the toroidal type continuously variable transmission is constituted by a spool valve 48.
Each of the cylinder chambers 43A and 43B of the cylinder chamber 43 is
7A and 47B communicate with the spool valve 48.
Spool 51 slidably disposed in spool valve 48
Is biased toward the other end by a spring 52 disposed between the valve case and one end. Spool valve 48 has S at one end
a port is formed, and an Sb port is formed at the other end.
The hydraulic pressure Pa is supplied to the port a through the solenoid valve 55A, and the hydraulic pressure Pb is supplied to the Sb port through the solenoid valve 55B. The spool valve 48 is connected to a PL port communicating with the hydraulic line, an A port communicating with the deceleration cylinder chamber 43A via the oil passage 47A, a B port communicating with the speed increasing cylinder chamber 43B via the oil passage 47B, and the reservoir. It has two communicating R ports. Spool valve 48
Has a sleeve 49 which is slidably disposed in the valve case and in which a spool 51 is slidably fitted. The position of the sleeve 49 is controlled according to the target gear ratio, as described later.

A precess cam 53 is connected to the tip of the tilting shaft 11, and one end of a lever 54 pivotally connected at the center abuts on the precess cam 53, and the other end of the lever 54 is the other end of the spool 51 of the spool valve 48. Is in contact with The precess cam 53 is displaced in accordance with the displacement amount Y of the tilt shaft 11 of the trunnion 33 in the tilt axis direction and is also displaced in accordance with the displacement amount θ around the tilt axis. The composite displacement of the displacement is detected. Spool 51
Is displaced in the spool valve 48 in accordance with the resultant displacement. The position of the spool 51 is feedback-controlled to match the position of the sleeve 49.

The controller 58 receives detection signals from various sensors such as an engine speed sensor 56 and an accelerator opening sensor 57. The controller 58 calculates a target gear ratio based on gear shift information signals such as an engine speed and an accelerator opening detected by these sensors, and outputs a control signal to the solenoid valves 55A and 55B, that is, outputs a duty signal to be described later. I do. The engine speed sensor 56 is a vehicle speed sensor, and the accelerator opening sensor 57
May be an accelerator pedal depression amount sensor or a throttle opening sensor.

The controller 58 controls the position of the sleeve 49 to a position corresponding to the target gear ratio calculated based on the driving state of the vehicle detected by various sensors. That is, the pressure Pa acting on the ports Sa and Sb of the spool valve 48,
The differential pressure ΔP of Pb is controlled by the solenoid valves 55A and 55B so as to have a value corresponding to the target gear ratio, and the sleeve 49 of the spool valve 48 and the differential pressure ΔP Springs 5 arranged at both ends
It moves to a position where the zero spring force is balanced. Pressure P
a and Pb are transmitted from the controller 58 to the solenoid valve 55
A and 55B are controlled by a pulse width modulation control signal having a duty signal outputted from each of the valves A and 55B, that is, a duty A and a duty B. That is, the connection between the drain port D connected to the reservoir and the pilot port E connected to the pilot pressure generation circuit with respect to the output port C of each of the solenoid valves 55A and 55B is switched based on the duty ratio. Since the average opening degree of the solenoid valves 55A and 55B is controlled, the pressures Pa and Pb appearing at the output port C become dut.
The pilot pressure Pp can be extracted from y (duty) A and dutyB. Duty refers to the ratio of the pulse width (ON time) to the pulse repetition period in the pulse width modulation control. That is, duty (%) is given by the following equation. duty = (one cycle of solenoid ON time / solenoid operation cycle) × 100

For example, when the gears are to be shifted to the speed increasing side when the trunnions 33 and 37 are at a certain neutral position,
The calculated duty A and duty B are the solenoid valve 5
As a result, the relationship between the hydraulic pressure Pa and the hydraulic pressure Pb acting on both ends of the spool valve 48 becomes Pa> Pb, and the sleeve 49 moves to the right in the drawing. As a result of this movement, the hydraulic line is connected to the oil passage 47 through the PL port.
B, the oil passage 47A communicates with the reservoir via the R port, and the pressure Pu of the oil passage 47B connected to the speed increasing side cylinder chambers 43B, 46B is reduced.
It becomes larger than the pressure Pd of the oil passage 47A connected to A (Pu> Pd). As a result, the cylinder chambers 43A, 43B
4, the trunnions 33 and 37 in FIG. 4 are displaced in the direction in which the displacement amount Y in the tilt axis direction is negative, that is, the trunnions 33 on the left side in the figure are displaced upward, and the trunnions 37 on the right side in the figure are displaced.
Is displaced downward. At this time, trunnions 33, 37
Is that the amount of displacement θ around the tilt axis is negative due to the tilt characteristics of the power rollers 6 and 9 (θ <0, the main shaft of the power roller 6 and the toroidal transmission unit 2 above the main shaft 3 of the toroidal transmission unit 1 in FIG. 3). The power roller 9 below 3 starts to tilt in the clockwise direction and the remaining power roller in the counterclockwise direction) (increasing side), and the speed change operation starts in the increasing speed side.

When the trunnions 33 and 37 continue to tilt, the displacement of the spool 51 to the right causes the pressure P in the oil passage 47A to increase.
The magnitude of d and the pressure Pu of the oil passage 47B are switched. That is, the hydraulic pressure of the hydraulic line entering the PL port acts on the deceleration-side cylinder chamber 43A, and the oil passage 47B connected to the speed-increase-side cylinder chamber 43B is communicated with the reservoir so that the trunnion 3
The direction of the tilt axis direction displacement of 3, 37 changes. When the displacement amount Y in the tilt axis direction becomes a positive value, the trunnions 33 and 37 start to tilt toward the deceleration side. The gear ratio converges to the target gear ratio by repeating the above gear shifting operation, and when the gear ratio reaches the target gear ratio, the displacement Y in the tilt axis direction of the trunnions 33 and 37 also becomes zero and the gear shifting operation ends. And the spool 51
And the sleeve 49 are aligned, and supply of hydraulic oil to the hydraulic actuators 41 and 44 is stopped.

FIG. 5 is a diagram showing another example including a gear ratio control hydraulic mechanism of a toroidal type continuously variable transmission. In the transmission ratio control hydraulic mechanism of the toroidal type continuously variable transmission shown in FIG. 5, the spool valve 60 constituting the control valve is of a type having no sleeve. Other basic configurations are
Since it is equivalent to the toroidal type continuously variable transmission shown in FIG. 4, the same reference numerals are given to the same elements and parts.
The outputs of the solenoid valves 55A and 55B are
Act directly on the end of the spool 61. Precess cam 5
The combined displacement amount of the displacement axis direction displacement amount Y and the displacement angle displacement amount θ of the trunnion 33 detected by the trunnion 33 is input to the potentiometer 64 via the lever 63. Potentiometer 6
4 converts the resultant displacement amount into a corresponding voltage value V and inputs it to the controller 58. On the other hand, the controller 58 obtains a target speed ratio based on the speed information input from the engine speed sensor 56 and the accelerator opening sensor 57, and calculates a target voltage value corresponding to the target speed ratio in a predetermined conversion table or the like. By means of Controller 58
Outputs a control signal to the solenoid valves 55A and 55B in the form of a signal (duty signal) in which the duty ratio is sequentially changed based on the voltage deviation between the voltage value and the target voltage value.

From the output ports C of the solenoid valves 55A and 55B, control oil pressures Pa and Pb corresponding to each duty are output to the Sa port and the Sb port of the spool valve 60.
The control oil pressure Pa supplied to the Sa port and the Sb port,
Pb is controlled so that the pressure difference between the two oil pressures is proportional to the voltage value deviation. As shown in FIG.
To move left and right, the PL port communicates with the A port or the B port, the oil passages 47A and 47B are connected to the PL port or the R port, and the operating oil pressures Pd and Pu of the oil passages 47A and 47B are connected.
And a differential pressure is created. The trunnions 33, 37 are displaced in the tilt axis direction according to the pressure difference between the cylinder chambers 43A, 43B and the pressure difference between the cylinder chambers 46A, 46B in the cylinder chambers 43, 46, and start the shifting operation. As the tilt angle approaches the target tilt angle and the voltage value approaches the target voltage value, the displacement Y in the tilt axis direction of each of the trunnions 33 and 37 approaches zero, and the actual gear ratio also approaches the target gear ratio. Go. Each time the sign of the voltage deviation is reversed, the above-described shift operation is repeated, and when the actual speed ratio matches the target speed ratio, both the displacement Y in the tilt axis direction of the trunnions 33 and 37 and the voltage deviation become zero. As a result, the power rollers 6, 9 return to the neutral position, and the shift operation ends.

The toroidal-type continuously variable transmission as described above has the following problems. This problem will be described with reference to FIG. 6 which shows an example of a duty signal and a pilot pressure to a solenoid valve operated in a conventional manner used in a toroidal type continuously variable transmission. When a normally open valve is used for both the solenoid valves 55A and 55B, the normal control method uses the start point of the duty cycle (at time t in FIG. 6) as shown in FIG.
c ₁₎ by a time corresponding to the duty ratio of each of the solenoid valves 55A, it is energized the solenoids of 55B.
That is, the signal Da shown by the solid line and the signal shown by the broken line are D
b is a duty signal to the solenoid valves 55A and 55B, respectively, and the graph shown at the top indicates a change in the pilot pressure Pp. Solenoid valves 55A, 55
Since B is a normally open valve, when energized tc ₁ , tc
When the hydraulic circuit is switched to c ₂ .
Since the connection with the pilot circuit is closed and the flow rate in the pilot circuit sharply decreases, the pilot pressure Pp sharply increases as shown by the peak Pc. Similarly, the solenoid valve 5
Time ta ₁ to 5A is de-energized, ta ₂ · ·, and the time tb ₁ the solenoid valve 55B is de-energized, t
In b ₂ ···, each solenoid valve is opened, the connection with the pilot circuit is opened, and the flow rate in the pilot circuit rapidly increases, so that the pilot pressure Pp becomes the peak Poa.
And Pob. The graph shown in FIG. 7 shows the duty signal and the pilot pressure P to the solenoid valves 55A and 55B when the duty ratios of the solenoid valves 55A and 55B are equal (50% each) in FIG.
It is a graph which shows p. In this case, the solenoid valve 55
A and 55B not only show a peak Pc at which the pilot pressure Pp suddenly rises and close simultaneously at times tc ₁ , tc ₂ ... _, But also open simultaneously at times to _1, to ₂ . and opening time (time ta _1, ta ₂ · ·, as shown in FIG. 6, the time tb _1, tb ₂ ·
・) Compared with peaks Poa and Pob when
This produces a sharper peak Po.

In the hydraulic mechanism for controlling the gear ratio of a toroidal type continuously variable transmission, as described above, the hydraulic pressure in the pilot circuit fluctuates rapidly due to the opening and closing of the solenoid valve. The negative pressure of the pressure Pp causes foaming of the working oil. In such a situation, the control pressure (Pa, Pb) of the solenoid valve using the pilot pressure Pp as the base pressure becomes the pilot pressure Pp.
Since it changes with the change of p, normal control cannot be performed. Although a buffer device such as an accumulator may be used to absorb a sudden change in the pilot pressure Pp, providing such a device results in an increase in cost.

A transmission control device of a toroidal type continuously variable transmission which controls a gear ratio to a target gear ratio by applying a pilot pressure controlled by a duty ratio of a solenoid valve to both ends of a spool of a spool valve is disclosed. It is disclosed in Japanese Unexamined Patent Publication No. Hei 8-233084. According to the transmission control device for a toroidal-type continuously variable transmission disclosed in this publication, when there is an error in the neutral position of the spool valve, the solenoid is operated in accordance with the time integrated value of the actual transmission ratio error with respect to the target transmission ratio. The valve duty ratio is corrected. The time integrated value of the speed ratio error approaches 0, and the neutral position of the spool valve is changed to the true neutral position by repeating the correction.

[0022]

Therefore, in the gear ratio control hydraulic mechanism of the toroidal type continuously variable transmission, the fluctuation of the pilot pressure has a peak in the opposite direction when the solenoid valve is opened and when the solenoid valve is closed. By controlling the operation of the solenoid valve so that the pilot pressure fluctuations cancel each other, the solution is to reduce pilot pressure fluctuations at low cost without using a buffer device such as an accumulator. There are issues to be addressed.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and to open and close a solenoid valve without fundamentally changing a conventional structure having two solenoid valves. Even if the operation of the valve is controlled or the structure of the solenoid valve is changed, only the type of the solenoid valve is changed. An object of the present invention is to provide a toroidal-type continuously variable transmission capable of suppressing fluctuations in pilot pressure to a minimum by canceling each other.

According to the present invention, there is provided an input disk and an output disk which are disposed opposite to each other, and a pair of powers for continuously changing the rotation of the input disk and transmitting the rotation to the output disk in accordance with a tilt angle with respect to the both disks. A pair of trunnions rotatably supporting the roller and the power roller and tilting about a tilt axis, a pair of hydraulic actuators having two cylinder chambers and displacing the trunnions in the tilt axis direction, respectively. A control valve for controlling the hydraulic pressure applied to each hydraulic actuator, a pair of solenoid valves for controlling a pilot pressure acting on both ends of the control valve, and a duty ratio corresponding to a target gear ratio or a deviation between the target gear ratio and an actual gear ratio. A controller for outputting a signal to the pair of solenoid valves, wherein the controller outputs a signal to each of the solenoid valves. About the toroidal type continuously variable transmission which comprises performing substantially simultaneously and opposite operation to each other and opening operation and closing operation of the respective solenoid valves by controlling the duty signal.

In the toroidal-type continuously variable transmission, both the pair of solenoid valves are normally open valves or normally closed valves, and the controller is configured to control the pulse of the duty signal output to one of the solenoid valves. The start time and the pulse end time are substantially coincident with the pulse end time and the pulse start time of the duty signal output to the other solenoid valve, respectively.

In this toroidal-type continuously variable transmission, one of the solenoid valves is a normally open valve and the other is a normally closed valve, and the controller outputs a signal to one of the solenoid valves. The pulse start point and the pulse end point of the duty signal are substantially coincident with the pulse start point and the pulse end point of the duty signal output to the other solenoid valve, respectively.

The control valve comprises a sleeve slidably provided in a valve case and a spool slidably inserted in the sleeve, and the control valve is provided with a relative displacement between the sleeve and the spool. A spool valve that shuts off a cylinder chamber or selectively communicates each of the cylinder chambers with a hydraulic pressure source and a reservoir. In this case, the controller determines the duty ratio of the duty signal based on the target gear ratio, and the pilot pressure output from the solenoid valve controlled by the duty ratio is applied to the spool or the sleeve. One of them acts on both ends thereof, and the combined displacement of the displacement of the trunnion in the tilt axis direction and the displacement about the tilt axis is fed back to the other displacement of the spool or the sleeve of the control valve. ing.

The control valve selectively shuts off the cylinder chamber when the spool is at the neutral position and selectively connects the cylinder chamber to a hydraulic pressure source and a reservoir when the spool is displaced from the neutral position. Is a spool valve that communicates with the In this case, the controller determines the duty ratio of the duty signal based on the target gear ratio and the combined displacement of the displacement of the trunnion in the tilt axis direction and the displacement of the trunnion around the tilt axis. The pilot pressure output from the solenoid valve controlled by the ratio acts on both ends of the spool.

Since the toroidal type continuously variable transmission according to the present invention is configured as described above, it operates as follows. That is, the controller outputs a duty signal corresponding to the target gear ratio or a deviation between the target gear ratio and the actual gear ratio to the pair of solenoid valves. The controller controls the duty signal to each solenoid valve to perform the valve opening operation and the valve closing operation of each solenoid valve substantially simultaneously and in reverse. Substantially at the same time as one of the solenoid valves performs the opening operation, the other solenoid valve performs the closing operation. Therefore, the pilot pressure acting on both ends of the control valve supplied by a pair of solenoid valves will be offset by the rise due to the closing of the solenoid valve and the decrease due to the opening of the solenoid valve, resulting in abnormal vibration of the pressure. Generation of bubbles and bubbles is suppressed, and fluctuation of the pilot pressure is suppressed. As a result, the operation of the control valve to which the pilot pressure acts and the hydraulic pressure to the hydraulic actuator controlled by the control valve are stabilized, the trunnion by the hydraulic actuator is displaced in the axial direction, and the tilt axis of the trunnion and the power roller is inclined. The tilting around is stabilized, and stable gear ratio control is performed.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a toroidal type continuously variable transmission according to the present invention will be described below with reference to the drawings. FIG. 1 is a graph showing a duty signal to a solenoid valve and a change in pilot pressure in one embodiment of a toroidal type continuously variable transmission according to the present invention. As the toroidal type continuously variable transmission, the structure of the conventional toroidal type continuously variable transmission shown in FIGS. 3, 4, and 5 can be adopted.
The same components will be described with the same reference numerals used in FIGS. 3, 4 and 5.

In the embodiment of the toroidal type continuously variable transmission according to the present invention shown in FIG. 1, the duty signal of the solenoid valve is a solenoid valve 55 for controlling the pilot pressure Pp.
A and 55B are duty signals when both are normally open valves. The duty signal to the solenoid valves 55A and 55B is a pulse width modulated frequency 50H.
This is a pulse width modulation signal of z (one cycle period is 20 msec). The duty ratio of the duty signal Da to the solenoid valve 55A shown by the solid line is 30%, and the duty ratio of the duty signal Db to the solenoid valve 55B shown by the broken line is complementary to the duty signal Da (that is, 1 in total).
00%), which is 70%. Time t ₁ , t
₃ ··· is the duty signal Da to the solenoid valve 55A
At the same time when the energization of the duty signal Db to the solenoid valve 55B ends. Times ta ₁ and ta ₂
Is the pulse end point at which the energization of the duty signal Da to the solenoid valve 55A ends, and also the pulse start point at which the energization of the duty signal Db to the solenoid valve 55B starts.

The total pulse width of the pulse width (duration time, for example, 6 msec) T ₁ of the duty signal Da and the pulse width (duration time) T ₂ of the duty signal Db is a pulse width modulation period T (for example, 20 msec). At the same time interval. The pulse start time t of the duty signal Db
_, T _4, ... Lag behind the pulse start times t ₁ , t _3, ... Of the duty signal Da by the pulse width T ₁ of the duty signal Da. Therefore, the solenoid valve 55
Since the opening operation and the closing operation of A and 55B are performed simultaneously and in reverse, even if the pilot pressure Pp increases when one solenoid valve is closed, the pilot pressure Pp tends to decrease when the other solenoid valve is opened. I do. As a result, the fluctuations of the pilot pressure Pp cancel each other and become small fluctuations as shown by P ₁ and P ₂ , and the fluctuations of the pilot pressure Pp can be reduced effectively. In the above embodiment, each solenoid valve is a normally open valve. However, it is apparent that each solenoid valve may be a normally closed valve.

FIG. 2 shows a duty signal to the solenoid valve and a change in pilot pressure in another embodiment of the toroidal type continuously variable transmission according to the present invention. In this embodiment, the solenoid valve 55A for controlling the pilot pressure Pp is a normally open valve,
5B is a normally closed valve. Time t ₁ , t ₃
Is the pulse start point at which the energization of the duty signal Da to the solenoid valve 55A is started and the pulse start point at which the energization of the duty signal Db to the solenoid valve 55B is started. Times t ₂ , t _4.
Is a pulse end point at which the energization of the duty signal Db to the solenoid valve 55B ends at the same time as a pulse end point at which the energization of the duty signal Db to the solenoid valve 55A ends. The pulse width of the duty signal Da (energization time, for example, 6 msec) and the duty signal D
The b pulse width (conduction time) is the same time width T _1. Thus, the same duty signal can be given to the solenoid valves 55A and 55B. At time t ₁ ,
At t ₃ ···, the solenoid valve 55A, which is a normally open valve, closes, so the pilot pressure Pp tends to increase, but the solenoid valve 55B, which is a normally closed valve, opens, so the pilot pressure Pp will decrease. And As a result, the fluctuation of the pilot pressure Pp becomes
As shown by P ₁ and P ₂ , the net pressure fluctuations are offset by each other and the fluctuations of the pilot pressure Pp can be effectively reduced. It is obvious that the solenoid valve 55A may be a normally closed valve and the solenoid valve 55B may be a normally open valve.

Further, the type of the toroidal type continuously variable transmission according to the present invention is not limited to the double cavity type toroidal type continuously variable transmission, but may be a toroidal type continuously variable transmission having a single toroidal transmission portion. It is obvious that, regardless of the type of the toroidal type continuously variable transmission, not only the spool valve having the sleeve shown in FIG. 4 but also the sleeve shown in FIG. Obviously, it can be applied to a spool valve which does not have a valve.

[0035]

As described above, in the toroidal type continuously variable transmission according to the present invention, the controller for outputting the duty signal to the pair of solenoid valves is controlled by controlling the duty signal to each solenoid valve. The valve opening operation and the valve closing operation are performed substantially simultaneously and in the opposite directions, so that fluctuations in the pilot pressure are canceled each other. Therefore, the hydraulic pressure in the pilot circuit does not suddenly fluctuate or become negative due to the opening and closing of the solenoid valve, and abnormal pilot pressure oscillations and air bubbles in the pilot oil are suppressed in the pilot circuit. it can. As a result, there is no need to provide a buffer device such as an accumulator in the pilot circuit, and a low-cost and stable pilot pressure can be supplied to the transmission ratio control mechanism of the toroidal-type continuously variable transmission.

[Brief description of the drawings]

FIG. 1 is a graph showing a duty signal to a solenoid valve and a change in pilot pressure in an embodiment of a toroidal type continuously variable transmission according to the present invention.

FIG. 2 is a graph showing a duty signal to a solenoid valve and a change in pilot pressure in another embodiment of the toroidal type continuously variable transmission according to the present invention.

FIG. 3 is a sectional view of a toroidal type continuously variable transmission of a double cavity type.

4 is a diagram showing an example of a gear ratio control hydraulic mechanism of the toroidal-type continuously variable transmission shown in FIG.

FIG. 5 is a diagram showing another example of the gear ratio control hydraulic mechanism of the toroidal type continuously variable transmission shown in FIG. 3;

FIG. 6 is a graph showing an example of a duty signal and a change in pilot pressure when a solenoid valve used in a toroidal type continuously variable transmission is operated in a conventional manner.

FIG. 7 is a graph showing a change in the pilot signal and a change in pilot pressure when the duty ratio of the duty signal to each solenoid valve in FIG. 6 is equalized.

[Explanation of symbols]

 1, 2 Toroidal transmission unit 3 Main shaft 4, 7 Input disk 5, 8 Output disk 6, 9 Power roller 11 Tilt axis 33, 37 Trunnion 43, 46 Cylinder chamber 45A, 45B Solenoid valve 48, 60 Spool valve (control valve) 49 Sleeve 51, 61 Spool 58 Controller Pp Pilot pressure Da, Db Duty signal Y Displacement in the tilt axis direction θ Displacement around the tilt axis

Continued on the front page F term (reference) 3J051 AA03 AA08 BA03 BB02 BD02 BE09 CA05 CB07 DA05 ED01 FA01 3J052 AA04 AA19 CA21 FB01 HA13 LA01

Claims (7)

[Claims] An input disk and an output disk disposed opposite to each other, and a pair of power rollers for continuously changing the rotation of the input disk and transmitting the rotation to the output disk according to a tilt angle with respect to the two disks; A pair of trunnions each rotatably supporting the power roller and tilting about a tilt axis, a pair of hydraulic actuators having two cylinder chambers and displacing the trunnions in the tilt axis direction, respectively, A control valve for controlling the hydraulic pressure applied to the actuator, a pair of solenoid valves for controlling a pilot pressure acting on both ends of the control valve, and a duty signal corresponding to a target gear ratio or a deviation between the target gear ratio and the actual gear ratio. A controller for outputting to the pair of solenoid valves, wherein the controller outputs the duty to each of the solenoid valves. A toroidal-type continuously variable transmission, wherein a valve opening operation and a valve closing operation of each of the solenoid valves are performed substantially simultaneously and in opposite directions by controlling a signal. 2. The controller according to claim 1, wherein the pair of solenoid valves are both normally open valves and normally closed valves, and the controller determines a pulse start time and a pulse end time of the duty signal output to one of the solenoid valves. 2. The toroidal-type continuously variable transmission according to claim 1, wherein the pulse end time and the pulse start time of the duty signal output to the other solenoid valve are substantially coincident with each other. 3. The solenoid valve of claim 1, wherein the one solenoid valve is a normally open valve and the other solenoid valve is a normally closed valve, and the controller is configured to determine when the pulse of the duty signal output to one of the solenoid valves starts. 2. The toroidal-type continuously variable transmission according to claim 1, wherein a pulse end point substantially coincides with a pulse start point and a pulse end point of the duty signal output to the other solenoid valve. 4. The control valve comprises a sleeve slidably provided in a valve case and a spool slidably inserted in the sleeve, and the control valve is provided with a relative displacement between the sleeve and the spool. A spool valve for shutting off a cylinder chamber or selectively communicating each of the cylinder chambers with a hydraulic source and a reservoir, respectively.
4. The toroidal-type continuously variable transmission according to any one of 3. 5. The controller according to claim 1, wherein the controller determines a duty ratio of the duty signal based on the target gear ratio, and the pilot pressure output from the solenoid valve controlled by the duty ratio is applied to the spool or the spool. Acting on either end of one of the sleeves, the combined displacement of the displacement of the trunnion in the axial direction and the displacement about the displacement axis causes a displacement of the spool of the control valve or the other of the sleeve. The toroidal-type continuously variable transmission according to claim 4, wherein the transmission is fed back. 6. The control valve selectively shuts off the cylinder chamber when the spool is in a neutral position and selectively connects the cylinder chamber to a hydraulic pressure source and a reservoir when the spool is displaced from the neutral position. The toroidal-type continuously variable transmission according to any one of claims 1 to 3, further comprising a spool valve that communicates with the toroidal type. 7. The controller according to claim 1, wherein the controller determines a duty ratio of the duty signal based on the target speed ratio and a combined displacement of the displacement of the trunnion in a tilt axis direction and a displacement of the trunnion. The toroidal-type continuously variable transmission according to claim 6, wherein the pilot pressure output from the solenoid valve controlled by the duty ratio acts on both ends of the spool.