JPS63172075A - Oil pressure controlling method by solenoid valve - Google Patents

Abstract

PURPOSE:To securely carry out an oil pressure control in a low duty ratio zone by setting the operating time per one period at a defined time larger than the operation limit time of a solenoid valve and changing the period or nonoperating time of a duty control signal. CONSTITUTION:A pulley control valve 43 and a starting control valve 45 operate solenoids 44, 46 by means of a duty control signal outputted from an electronic control device 60. The operating time per one period is set at a defined time larger than the operation limit time of a solenoid valve, and a duty ratio call be varied by changing the period or nonoperating time. Thereby, a valve body can be securely operated even in a low duty ratio zone, e.g., below 20 %, generating an output oil pressure. Also, by changing the periods of the duty control signal at random, the resonance of a mechanical system and a hydraulic system can be securely prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a hydraulic control method using a solenoid valve, and more particularly to a duty control method.

BACKGROUND OF THE INVENTION Conventionally, as hydraulic control devices for automobile transmissions and clutches, devices are known that control electromagnetic valves using pulse width modulation control (PWM) using a computer to achieve precise hydraulic control.

The above pulse width modulation control is also called duty control, and by changing the ratio of the operating time to the cycle of the duty control signal input to the solenoid valve (this is called the duty ratio), the duty ratio can be adjusted as shown in Fig. 5. This system generates an output oil pressure approximately proportional to.

Generally, the frequency used for duty control is several 11z ~
The frequency is approximately several hundred Hz, but the duty frequency must be set low (if this happens, the output hydraulic pressure will pulsate greatly and accurate hydraulic control will not be possible, so the duty frequency must be increased. However, the characteristics of the duty ratio and output hydraulic pressure depend on the duty frequency. For example, at a low duty frequency of several Hz, good characteristics are obtained in which the duty ratio and output oil pressure are almost proportional in the entire duty ratio range as shown in Fig. 5A, whereas at a duty frequency of several hundred Hz, At higher frequencies, almost no output oil pressure is generated in the low duty ratio region as shown in Figure 5B. This is because there is a minimum operating time), and as the duty ratio changes, if the operating time per cycle becomes shorter than the operating limit time, the valve body will no longer be able to operate.

Purpose of the Invention The present invention has been made in view of such conventional problems.
The purpose is to provide a hydraulic control method using a solenoid valve that can reliably control hydraulic pressure in a low duty ratio range.

Structure of the Invention In order to achieve the above object, the present invention provides a hydraulic control method for controlling output hydraulic pressure by changing the ratio of the operating time to the cycle of the duty control signal input to a solenoid valve. The operating time per cycle is set to a fixed time longer than the operating limit time of the solenoid valve, and the ratio of the operating time to the cycle is variable by changing the cycle or non-operating time of the duty control signal. be.

In other words, no matter how low the duty ratio becomes, the operating time per cycle is always equal to or longer than the solenoid valve's operating limit time, so the solenoid valve can operate reliably and the hydraulic characteristics in the low duty ratio range are the same as in the past. can prevent deterioration.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an example of a V-belt type continuously variable transmission for using the hydraulic control method of the present invention.
is connected to the input shaft 4 via the damper mechanism 3. An external gear 5 is fixed to the end of the input shaft 4, and this external gear 5 meshes with an internal gear 6 fixed to the drive shaft 11 of the continuously variable transmission 10 to transfer the power of the input shaft 4. The speed is decelerated and transmitted to the drive shaft 11.

The continuously variable transmission 10 includes a drive pulley 1 provided on a drive shaft 11.
2, a driven pulley 14 provided on the driven shaft 13, and a V-belt 15 wound between both pulleys. The drive pulley 12 has a fixed sheave 12a and a movable sheave 12b.
A torque cam device 16 and a compression spring 17 are provided behind the movable sheave 12b.

The torque cam device 16 generates a thrust proportional to the input torque, and the compression spring 17 generates an initial thrust sufficient to prevent the V-belt 15 from loosening.
5 is given the belt tension necessary for torque transmission. On the other hand, similarly to the driving pulley 12, the driven pulley 14 has a fixed sheave 14a and a movable sheave 14b, and a hydraulic chamber 18 for speed ratio control is provided behind the movable sheave 14b. The hydraulic pressure to this hydraulic chamber 18 is controlled by a pulley control valve 43, which will be described later.

A hollow shaft 19 is rotatably supported on the outer periphery of the driven shaft 13, and the driven shaft 13 and the hollow shaft 19 are connected and connected by a starting clutch 20 consisting of a wet multi-disc clutch. The hydraulic pressure applied to the starting clutch 20 is controlled by a starting control valve 45, which will be described later. The hollow shaft 19 has a forward gear 21 and a t&
A forward gear 22 is rotatably supported, and either the forward gear 21 or the reverse gear 22 is connected to the hollow shaft 19 by a forward/reverse switching dog clutch 23 . A reverse idler gear 25 that meshes with the reverse gear 22 and another reverse idler gear 26 are fixed to the reverse idler shaft 24. Further, the counter shaft 27 is provided with the forward gear 21 and the reverse idler gear 2.
6 and a final reduction gear 29 are fixed, and the final reduction gear 29 meshes with a ring gear 31 of a differential device 30 and transmits power to an output shaft 32.

The pressure regulating valve 40 regulates the hydraulic pressure discharged from the oil reservoir 41 by the oil pump 42, and outputs it as line pressure to the pulley control valve 4.
3 and the start control valve 45. Pulley control valve 4
3 and the start control valve 45 actuate the solenoids 44 and 46 in accordance with the duty control signal output from the electronic control device 60, and control the line pressure to control the driven pulley 14, respectively.
Control hydraulic pressure is output to the hydraulic chamber 18 and the starting clutch 20. The specific structure of the control valves 43 and 45 includes, for example, a combination of a spool valve 50 and a solenoid valve 52 as shown in FIG. A three-bottom solenoid valve 53 that selectively opens and closes the boat 56 and outputs control hydraulic pressure to the output boat 57.
It may be configured by a single unit.

The control valves 43 and 45 are replaced by a spool valve 50 as shown in FIG.
and a signal oil pressure generation solenoid valve 52, and assuming that the duty ratio of the signal input to the solenoid valve 52 is , the output oil pressure P1 of the solenoid valve 52 is given by the following equation.

P arr= P :n X (1-D+)
-(11 In the above equation, P in is the input oil pressure (for example, line pressure).

The output oil pressure P1 is input as a signal oil pressure to the right end chamber of the spool 50, and the control oil pressure PC output from the spool valve 50 is given by the following equation.

P.

Further, when the control valves 43, 45 are constructed of a single electromagnetic valve 53 as shown in FIG. 3, the output oil pressure PU is given by the following equation, assuming that the duty ratio of the signal input to the coil is D2.

Prm=P:nXD2 ---
(31. In the above embodiment, a normally closed type solenoid valve is used, but a normally open type may be used.

In addition, depending on the type of solenoid valve and how it is used, D2 can also be turned ON with respect to the cycle of the duty control signal.
In addition to the time ratio (ON duty), OF
It is also possible to use the ratio of F times (OFF data).

In the V-belt continuously variable transmission with the above configuration, when the operating frequency of the duty control signal input to the solenoid valve is increased to perform precise hydraulic control, the cycle becomes shorter, so at a low duty ratio, Operating time (O in the example)
N time) becomes shorter.

When the operating time becomes less than the operating limit time of the electromagnetic valve, the valve body becomes inoperable and no output oil pressure is generated at low duty ratios as shown in FIG. 5B.

In the present invention, in order to solve such problems, - the operating time per cycle is set to a fixed time longer than the operating limit time of the solenoid valve, and the cycle or non-operating time (in the embodiment, the OFF time) is changed. The ratio is variable.

Figure 4 is a diagram of each signal waveform of the present invention when the duty ratio is 25%, 50%, and 70%. In any signal waveform, the operating time (ON time) T is constant, and the value T is the value of the solenoid valve. It is set slightly longer than the operating limit time. The operating limit time of a solenoid valve varies depending on the type and type of the solenoid valve.
In case 3, the valve body 54 does not slide on the valve body, so the second
Compared to the electromagnetic valve 52 using a needle-shaped valve body as shown in the figure, the operating limit time is shorter, on the order of several milliseconds. therefore,
If the operating time T is set to a value slightly larger than the operating limit time of the solenoid valve and the period or non-operating time is changed, 2
Even in a low duty ratio range of 0% or less, the valve body can operate reliably to generate output oil pressure, and good characteristics similar to those shown in FIG. 5A can be obtained. Furthermore, as the duty ratio increases, the frequency also increases, so pulsations in the output oil pressure are also eliminated.

In addition, in general solenoid valves, the operating limit time is not constant due to variations in parts such as the spring force of the spring, the number of turns of the coil, and the extension of the coil.As a result, the rising point of the characteristics shown in Figure 5, that is, the output oil pressure occurs. The minimum duty ratio is also not constant. On the other hand, in the present invention, by setting the operating time to a constant value equal to or longer than the operating limit time taking into account variations in parts, the above-mentioned variations in the rise point of the output oil pressure can be eliminated.

Furthermore, in the present invention, the operating time is fixed and the duty ratio is made variable by changing the cycle or non-operating time, so that the duty control signal is frequency modulated, so to speak, and the following effects can be expected. That is,
Conventionally, when the duty frequency is constant, vibration sources of mechanical systems such as engines, which cause resonance when the frequency matches the natural frequency of the engine or the natural frequency of the hydraulic circuit, are Resonance can be prevented by setting a duty frequency that is different from the vibration frequency, but since the natural frequency of vibration in the hydraulic system varies depending on the input oil pressure and temperature, under certain conditions the duty frequency of the hydraulic system may change Even if a different duty frequency is set, resonance may occur if the input oil pressure or temperature changes. On the other hand, in the hydraulic control method of the present invention, the period of the duty control signal is changed randomly, so resonance with the mechanical system and the hydraulic system can be reliably prevented. Furthermore, in duty control, high-frequency noise is generated because the valve body collides with the valve seat in a short period.In particular, in conventional control, since the period is constant, the number of collisions per unit time is constant, resulting in a sharp sound pressure peak. However, in the present invention, by randomly changing the period of the duty control signal, the sound pressure peak is effectively alleviated.

Effects of the Invention As is clear from the above explanation, according to the present invention, the operating time per cycle of the duty control signal is set to a constant time longer than the operating limit time of the valve body of the solenoid valve, and the duty control signal is Since the duty ratio is made variable by changing the cycle or the non-operating time, the solenoid valve can operate reliably even in the low duty ratio range, and it is possible to prevent deterioration of hydraulic characteristics in the low duty ratio range as in the prior art. Also,
- By setting the operating time per cycle to a value that takes into account component variations, it is possible to eliminate variations in the rise point of output oil pressure based on component variations. Since frequency modulation is performed to obtain a high frequency in the range, resonance with the mechanical system and hydraulic system can be prevented, and noise generation and hydraulic pulsation can be eliminated.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an example of a belt-type continuously variable transmission to which the present invention is applied; Figures 2 and 3 are specific structural diagrams of a control valve;
FIG. 4 is a signal waveform diagram of the duty control signal of the present invention, and FIG. 5 is a characteristic diagram of the duty ratio and output oil pressure at low and high frequencies. 1... Engine, 10... Continuously variable transmission, 20...
・Starting clutch, 43...Booty control valve, 45...
Start control valve, 52° 53... Solenoid valve, 60... Electronic control device. Figure 1 Figure 2 Figure 3 Figure 3 ('/,)

Claims (1)

[Claims] In a hydraulic control method that controls output oil pressure by changing the ratio of the operating time to the cycle of the duty control signal input to the solenoid valve, the operating time per cycle of the duty control signal is greater than or equal to the operating limit time of the solenoid valve. A hydraulic control method using a solenoid valve, characterized in that the ratio of the operating time to the cycle is made variable by setting the duty control signal to a constant time and changing the cycle or non-operating time of the duty control signal.