JPS6253246A - Hydraulic control device for continuously variable transmission - Google Patents

Abstract

PURPOSE:To ensure the proper control of line pressure with duty pressure generated through a duty-controlled solenoid valve by smoothing pulsating oil pressure arising from said solenoid valve through an accumulator. CONSTITUTION:A belt type continuously variable transmission 4 is equipped with a secondary cylinder 10 fed with pressurized oil through an oil pump 21 and a primary cylinder 19 fed with pressurized oil through a line pressure control valve 40 and a speed change control valve 50. In this case, a solenoid valve 65 for line pressure control and an accumulator 66 are connected to a reducing pressurized oil circuit 33, and the solenoid valve 65 is actuated by an signal on a duty ratio depending upon target line pressure calculated with a control unit 70, thereby generating pulsating oil pressure. And this pulsating oil pressure is smoothed through the accumulator 66, thereby converting said oil pressure into duty pressure at a predetermined level, and the pressure so converted is applied to the line pressure control valve 40 for the control thereof.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a hydraulic control device for a belt-type continuously variable transmission for a vehicle, and more particularly to a hydraulic control system that electronically controls a line pressure control valve and a speed change control valve by operating a duty pressure generated by an electric signal. , regarding line pressure control. Regarding this type of hydraulic speed change control, for example, Japanese Patent Laid-Open No. 55
There is a basic hydraulic control system shown in Japanese Patent No. -65755. This operates to balance the gear ratio control valve based on the factors of accelerator depression amount and engine speed, and determines the gear ratio based on the relationship between the two, and the gear ratio is controlled. In addition, in order to obtain the force necessary for pressing the pulley to transmit torque, line pressure is controlled by operating a pressure regulating valve based on factors such as the amount of accelerator depression and the gear ratio. By the way, according to the above configuration, in the case of shift 11JIH,
Since the speed of change in the gear ratio (hereinafter referred to as the gear change speed) is uniquely determined, responsiveness is lacking in, for example, a transient state where the change in the gear ratio is large, causing hunting and overshoot. Furthermore, the characteristics of line pressure control are uniquely determined, making it difficult to take into account various conditions. For this reason, in recent years, when unifying speed changes or controlling line pressure, electronic
However, there is a tendency to perform optimal continuously variable transmission control.

BACKGROUND ART 1 Conventionally, as for the electronic control of the above-mentioned continuously variable transmission, there is a system in which valves are directly operated using a torque motor, as shown in, for example, Japanese Patent Laid-Open No. 58-88252. Further, for example, in Japanese Patent Application Laid-open No. 59-159456, a gear ratio changing directional switching valve, which changes hydraulic oil with a solenoid valve,
It is shown that the speed change speed is controlled by operating the speed ratio change speed control valve. (Problems to be Solved by the Invention) By the way, according to the former of the conventional prior art described above, since it is a direct operation method using a torque motor, a large-scale actuator called a torque motor is required, and the drive source of the hydraulic valve is It is desirable to use hydraulic pressure.Also,
According to the latter of the prior art, line pressure control is still performed using gear ratio pressure and throttle pressure. Since two types of valve devices are used for the speed change control (2), there are problems such as a complicated structure and complicated control. Here, in order to perform electronic control of line pressure control, as in the latter shift speed control of the above-mentioned prior art, the duty pressure generated by draining oil from the solenoid valve is operated by acting on the line pressure control valve. is possible. Incidentally, the duty pressure in this case is a pulse-like one that changes between a constant pressure and zero as shown in Φ) in FIG. 3(c) according to the duty signal in FIG. 3(c). Therefore, if this duty pressure is applied directly to the line pressure control valve, the line pressure will pulsate and belt torque transmission will become unstable.
Damage to durability and vibration. It is also unfavorable in terms of noise. The present invention has been made in view of the above points, and an object of the present invention is to provide a hydraulic control device for a continuously variable transmission that smoothly controls line pressure using duty pressure generated by a duty signal. It is said that [Means for Solving the Problems 1] In order to achieve the above object, the present invention generates line pressure by regulating the pump oil pressure with a line pressure control valve, and divides the line pressure into two positions: oil supply and oil drain. In a hydraulic control device that supplies a primary cylinder with a variable speed control valve that controls the flow rate, or discharges the primary pressure of the cylinder to control the variable speed, the duty ratio according to the target line pressure calculated by the control unit. This signal is input to the line pressure control solenoid valve to generate a pulse-like hydraulic pressure, which is smoothed by an accumulator and turned into duty pressure at a predetermined level.The duty pressure is applied to the line pressure control valve to control the line pressure. and is configured to control pressure. [Operation 1] Based on the above configuration, the pulsed hydraulic pressure generated in the solenoid valve by the duty signal is smoothed by the accumulator and acts on the line pressure control valve, thereby suppressing pulsations in the line pressure. The duty ratio makes it possible to accurately control the line pressure. [Embodiments] Hereinafter, embodiments of the present invention will be described based on the drawings. Referring to FIG. 1, the outline of the control system according to the present invention will be explained. First, as a transmission system, the engine 1 is connected to the clutch 20.
Connected to the main shaft 5 of the continuously variable transmission 4 via front and rear appropriate replacement [3]. In the continuously variable transmission 4, a subshaft 6 is arranged parallel to the main shaft 5, a primary pulley 7 is provided on the main shaft 5, a secondary pulley 8 is provided on the subshaft 6, and a drive belt 11 is connected to both pulleys γ, 8. It is wrapped. Each of the pulleys 1, 8 is configured such that one of the pulleys is fixed and the other is moved in the axial direction so that the interval between the pulleys can be varied, and has a hydraulic cylinder 9, 10 on the movable side. Here, the primary cylinder 9 has a larger pressure receiving area than the secondary cylinder 10, and due to the primary pressure, the winding of the drive belt 11 around the pulley 7° 8 changes the ratio of the diameters so that the speed is continuously variable. ing. Further, the subshaft 6 is connected to the output shaft 14 via a set of glue reduction gears 12 and 13, and the drive gear 1 of the output shaft 14 is
5 is final gear 171G, differential gear ψ
17. Power is transmitted to drive wheels 19 via an axle 18 . The continuously variable transmission lI4 includes a hydraulic circuit 20. a control unit 70 and line pressure from the control unit 70; The hydraulic circuit 20 is operated by the duty signal for speed change control, and the primary and secondary cylinders 9 are
．． It is configured to control 10 hydraulic pressures. In FIG. 2, a hydraulic control system including a hydraulic circuit 20 will be described. It has an oil pump 21 driven by the engine 1, and a line pressure oil passage 22 on the discharge side of the oil pump 21 communicates with the secondary cylinder 10. , even more line pressure! II passes through the till valve 40 and communicates with a speed change control valve 50, and this speed change control valve 50 connects to the oil passage 23.
It communicates with the primary cylinder 9 via. A drain oil passage 24 from the speed change control valve 50 communicates with an oil pan 26 through a check valve 25 that completely drains the oil in the primary cylinder 9 and prevents air from entering. Further, the drain oil passage 27 from the line pressure control valve 40 has a lubrication valve 28 to generate a constant lubricating pressure.
The upstream side thereof communicates with the oil passage 23 to the primary cylinder 9 via the side groove nozzle 29 of the drive bell 1-11 and the brie filling valve 30, respectively. The line pressure control valve 40 has a valve body 41. Spool 42. It has a spring 43 that biases one side of the spool 42, and the spool 42 connects the port 41a of the oil passage 22 to the drain oil passage 2.
The pressure is regulated by communicating with the port 41b of No.7. The opposite side of the spring 43 from the spool 42 is received by a block 45 having an adjustment screw 44, and by adjusting the set load of the spring 43, it is possible to adjust the relationship between the duty ratio and line pressure due to variations in each component. In addition, line pressure is applied to the port 41c of the spool 42 on the opposite side to the spring 43 by an oil passage 36 branching from the oil passage 22, and the port 41c on the spring 43 side
d, a duty pressure for line pressure control is applied through the oil passage 37 in a direction to increase the line pressure. As a result, line pressure PL, its effective area SL, duty pressure Pd
, its effective area Sd, and spring load Fs, the following relationship holds true. FS +Pd -8d -PL -5LPL -(Pd
-8d +Fs )/SL From this, Figure 4 (2
), the line pressure PL is controlled in proportion to the duty pressure Pd. The variable speed control valve 50 has a valve body 51 . It has a spool 52, and by moving the spool 52 left and right, the port 5 of the oil passage 22 is
1a to a port 51b of the oil passage 23;
It operates between the port 51b and the oil drain position communicating with the port 51c of the drain oil passage 24. A constant reducing pressure acts on the port 51d at the oil supply side end of the spool 52 through the oil passage 53, and a duty pressure for speed change control acts on the port 51e at the chaff oil side end through the oil passage 54. , and the spool 5 at port 51e.
2 is biased by a spring 55 for initial setting. Here, the duty pressure changes between the same pressure as the reducing pressure PR and zero, and this on/off ratio (
Refueling and lubricating time by changing the duty ratio)
That is, the inflow and outflow flow conditions change, making it possible to control the speed change. That is, the shift speed di/dt is a function of the flow rate Q of the primary cylinder 9, and the flow rate Q is equal to the duty ratio. Since it is a function of line pressure PL and primary pressure Pp, the following equation holds true. di/dt= h (Q) = fx (D, PL
, pp) Here, the line pressure PL is equal to the gear ratio 1. Since the primary pressure Pp is controlled by the engine torque T and is determined by the line pressure PL and the gear ratio I, di/dt=fs (D, i). on the other hand,
The gear shift speed d t / d t is the target gear ratio i in steady state.
Since it is determined based on the deviation between s and the actual gear ratio 1, the following equation holds true. di/dt=k (is −i) From this, if the target speed ratio IS is determined at the actual speed ratio i and the speed change speed di/dt is determined, then from the relationship between the speed change speed dl/dt and the speed change ratio 1, Find the duty ratio. Therefore, it can be seen that if the shift control valve 50 is operated 1J with this duty ratio, the shift speed can be controlled over the entire shift range. Next, a circuit for generating duty pressure for controlling each of the valves 40 and 50 will be explained. First, an oil passage 31 branches from the line pressure oil passage 22 as a circuit that applies a constant base pressure, and this oil passage 31 has an orifice 32 that limits the flow rate and communicates with the reducing valve 60.Reducing valve 60 has a spring 63 biased to one side of the valve body 61, spool 62, and spool 62;
Inlet port 61a and outlet port 1-6 communicating with oil passage 31
1b and a drain boat 61c, the reducing pressure oil passage 33 from the outlet port 61b communicates with the boat 61d on the opposite side of the spring 63 of the spool 62. Further, the reducing pressure can be adjusted by moving a block 64 that receives one of the springs 63 using an adjustment screw or the like to change the spring load. In this way, the line pressure is being supplied to the boat 61a while being restricted by the orifice 32, and when the reducing pressure in the reducing pressure oil passage 33 decreases, the spool 62 communicates with the boats 61a and 61b by the spring 63 and introduces line pressure. do. Then, the spool 62 is returned by the upper limit of the oil pressure of the boat 61d, communicating the boats 61b and 61c, and reducing the reducing pressure. By repeating this operation, the line pressure is replenished by the amount of the decrease in the reducing pressure. At the same time, a constant reducing pressure that matches the setting of the spring 63 is obtained. The reducing pressure oil passage 33 communicates with a line pressure control solenoid valve 65 and an accumulator 66, and an oil passage 37 branches off from the downstream side of the A relief 34 in the middle of the reducing pressure oil passage 33. Thus, the orifice 34
On the downstream side of , a solenoid valve 65 intermittently discharges a constant reducing pressure in response to a duty signal to generate a pulse-like oil pressure, which is smoothed by a 7-cumulator 6G to become a duty pressure at a predetermined level, and the duty pressure oil is Line 37 supplies line pressure control valve 40 . Here, the accumulator 66 has a natural frequency higher than the frequency of the solenoid valve 65. and solenoid valve 6
When solenoid valve 5 is turned on and oil is drained, it is replenished by accumulator 66 to suppress the drop in duty pressure, and solenoid valve 6
5 is turned off to supply oil, the accumulator 6G absorbs it and suppresses the increase in duty pressure, thus making the pulsed oil pressure constant as shown in FIG. 3(C). Further, an oil passage 53 branches from the upstream side of the orifice 34 of the reducing pressure oil passage 33, and a solenoid valve 67 for speed change speed control is connected to the downstream side of the orifice 35 of the duty pressure oil passage 54, which branches from the middle of the oil passage 53. It goes through. In this way, a constant reducing pressure is supplied to the variable speed control valve 50 through the oil passage 53, and furthermore, the solenoid valve 67 is operated by the duty signal on the downstream side of the orifice 35, thereby generating a pulsed duty pressure, which is then maintained as it is. It comes to be supplied to the variable speed control valve 50. Here, the solenoid valve 65 is configured to drain oil when the duty signal is on, and therefore, the greater the duty ratio, the smaller the duty pressure is as shown in FIG. 4(b). As a result, the line pressure for the duty ratio is 0 in the same figure.
It becomes a characteristic that changes as a decreasing function like . On the other hand, since the solenoid valve 67 has a similar configuration, when the duty ratio is large, it takes a long time to switch the speed change control valve 50 to the oil supply position to shift up, and in the opposite case, it takes a long time to switch it to the oil drain position. It gets longer and shifts down. When the deviation of 1s-1 is large, the change in duty ratio is large, so the speed at which the shift up or down is controlled greatly. Furthermore, to explain the electric control system including the IIJIII unit 70, the primary boolean rotation speed sensor size is 71 degrees, the secondary boolean rotation speed sensor 72. Throttle rotation sensor 73. It has an engine rotation speed sensor 74, and these sensor signals are input to the control unit 70. The control unit 70 provides a duty ratio signal to the solenoid valve 65 mainly in accordance with a target line pressure determined based on the engine torque T. In addition, the shift speed di/dt is determined based on the deviation between the target speed ratio is and the actual speed ratio 1, and a duty ratio signal determined based on the relationship between these di/dt and l is given to the solenoid valve 67. ing. Next, the operation of the hydraulic control device configured as described above will be explained. First, the oil pump 21 is driven by the operation of the engine 1, and the line pressure of the oil passage 22 is supplied only to the secondary cylinder 10, and the gear ratio is set to the maximum low gear. At this time,
A constant reducing pressure is taken out by the reducing valve 60 using line pressure, and this is applied to each solenoid valve 65.
．． 67, and duty pressure can be generated. Therefore, when the gear ratio is maximum and the throttle rotation is large especially when starting, a signal with a small duty ratio is input from the control unit 70 to the solenoid valve 65 to reduce the II oil drop, thereby increasing the duty pressure. Largely determined. Then, this duty pressure enters the boat 41d of the line pressure control valve 40 and acts in a direction to increase the line pressure, thereby setting the line pressure high. Then, as the gear ratio becomes smaller or the engine torque decreases, the duty ratio becomes larger and the 11 oil M of the solenoid valve 65 increases.
increases, the duty pressure decreases and the line pressure also decreases. In this way, the line pressure is controlled by the duty signal. On the other hand, after starting, a signal of the duty ratio in the relationship between the shift speed old/dt and i by +8-i is input from the control unit 70 to the solenoid valve 67 to generate duty pressure, which operates the shift speed control valve 50. Primary cylinder 9
The line pressure is supplied and drained at the specified flow rate. Therefore, the gears are shifted at the target gearshift speed, and as in a transient state,
The larger s-1 is, the faster the gear shifting speed is. Although one embodiment of the present invention has been described above, the on/off relationship of the solenoid valve can also be reversed.

【Effect of the invention】

As described above, according to the present invention, in a system in which a duty signal is input to a solenoid valve to generate duty pressure, and the line pressure is controlled by this duty pressure, the pulsed hydraulic pressure generated by the solenoid valve is transmitted to the Akicomulator. Since the line pressure is smoothed and converted into a duty pressure at a predetermined level, the line pressure control valve statically generates line pressure, which has no problem with pulsating pressure. The line pressure can be accurately controlled by the duty ratio.

[Brief explanation of drawings]

Fig. 1 is a block diagram schematically showing an embodiment of the hydraulic control system of the present invention, Fig. 2 is a circuit diagram showing the hydraulic control system in detail, and Fig. 3 is a circuit diagram showing the hydraulic control system in detail.
The figure is a waveform diagram of duty pressure, and FIG. 4 is a characteristic diagram of line pressure control. 4...Continuously variable transmission, 9...Primary cylinder, 1
0... Secondary cylinder, 22... Line pressure oil path, 31... Duty pressure oil path, 40... Line pressure control valve, 50... Shift speed control valve, 65... Line pressure control solenoid valve, 66... Akicom regulator, 70
···Controller unit. Mouth spasm "-Li-:,,5・1 Closed 1 stiff

Claims (1)

[Claims] Pump oil pressure is regulated by a line pressure control valve to generate line pressure, and the line pressure is supplied to the primary cylinder by a variable speed control valve that has two positions, oil supply and oil discharge, and controls the flow rate. Or, in a hydraulic control device that controls the speed change by discharging the primary pressure of the cylinder, a signal with a duty ratio corresponding to the target line pressure calculated by the control unit is input to the line pressure control solenoid valve and pulsed. A hydraulic control device for a continuously variable transmission, which is configured to generate a hydraulic pressure, smooth the hydraulic pressure with an accumulator to convert it into a duty pressure at a predetermined level, and apply the duty pressure to a line pressure control valve to control the line pressure. .