JP2782241B2 - Hydraulic control device for continuously variable transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for electronically controlling a line pressure and a gear ratio in a vehicle belt-type continuously variable transmission, and more particularly, to a transient of a gear shift. Regarding measures to improve responsiveness.

[Conventional technology]

2. Description of the Related Art Conventionally, there is a prior art in Japanese Patent Application Laid-Open No. Sho 62-4958 regarding electronic shift control of this type of continuously variable transmission. Here, a shift control valve consisting of a two-position valve is connected to the cylinder of the primary pulley, and the pulse-like duty pressure generated by the duty solenoid valve acts on the shift control valve to adjust the primary pressure together with the flow rate of the primary cylinder. In addition, it shows that a shift control of an upshift or a downshift is performed.

[Problems to be solved by the invention]

By the way, in the above-mentioned prior art, since the shift control valve is a single shift control valve having a predetermined diameter and a stroke, there is a limit in the shift characteristic. That is, when the speed is controlled by adjusting the flow rate of the primary cylinder by the speed change control valve and the speed ratio change is small in a steady state, the smaller the valve diameter and stroke, the smaller the amount of oil drained from the valve. This is advantageous in that the convergence is improved and fine shift control can be performed. On the other hand, when the change in the gear ratio is large in the transient state of rapid acceleration / deceleration, the larger the diameter and the stroke of the valve, the larger the flow rate can be adjusted at one time, which is advantageous in terms of the responsiveness of the gear shift.

Therefore, it is difficult to satisfy both of these conflicting conditions with a single shift control valve.

Here, in ordinary city running, the vehicle is rarely rapidly accelerated / decelerated, the engine load is changed relatively slowly, and the transmission is shifted slowly. For this reason, if the shift control valve is configured to emphasize shift characteristics in a steady state, the shift during transition tends to lack responsiveness.

The present invention has been made in view of such a point, and an object of the present invention is to provide a continuously variable transmission capable of improving both the stability of a steady-state shift and the responsiveness of a transient shift. Another object of the present invention is to provide a hydraulic control device.

[Means for solving the problem]

In order to achieve the above object, a hydraulic control device for a continuously variable transmission according to the present invention is a hydraulic control device for a continuously variable transmission that performs a shift control by controlling a hydraulic pressure to a primary cylinder. A shift control solenoid valve that generates a pulse-shaped duty pressure in response to the shift control solenoid valve; and a steady-state shift control valve that operates at two positions of oil supply and oil discharge according to the pulse-shaped duty pressure from the shift control solenoid valve.
An orifice for smoothing a pulsed duty pressure from the shift control solenoid valve; and a transient shift control valve for determining a stroke position in accordance with the duty pressure smoothed by the orifice. The shift control valve and the transient shift control valve communicate in parallel with the primary cylinder.

[Action]

Based on the above configuration, the two shift control valves, the steady shift control valve and the transient shift control valve, operate with the duty pressure of one shift control solenoid valve to supply and discharge the primary cylinder, Shift control. In the steady state and the transient state, the duty ratio of the control signal output to the solenoid valve is adjusted, and the level of the duty pressure of the solenoid valve changes. It selectively operates and performs fine shift control in the steady state. On the other hand, in the transient state, a large amount of oil is supplied to and discharged from the primary cylinder by the transient shift control valve, so that the shift can be performed responsively.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 2, the outline of the control system according to the present invention will be described. First, as a drive system, the engine 1 has the clutch 2,
It is connected to a primary shaft 5 of a continuously variable transmission 4 via a forward / reverse switching device 3. In the continuously variable transmission 4, a secondary shaft 6 is disposed in parallel with a primary shaft 5, a primary pulley 7 is provided on the primary shaft 5, a secondary pulley 8 is provided on the secondary shaft 6, and a primary pulley 7 and a secondary pulley 8 are provided on the secondary pulley 8. The drive belt 11 is wound. The primary pulley 7 and the secondary pulley 8 are configured such that the other is movable in the axial direction with respect to one fixed side so that the pulley interval is variable, and has a primary cylinder 9 and a secondary cylinder 10 on the movable side.
Here, the pressure receiving area of the primary cylinder 9 is larger than that of the secondary cylinder 10, and the primary pressure changes the ratio of the winding diameter of the drive belt 11 to the primary pulley 7 and the secondary pulley 8 so that the stepless speed change is performed. It has become.

The secondary shaft 6 has a set of reduction gears 12 and 1.
3 to the output shaft 14 and the drive gear 1 of the output shaft 14
5 is configured to transmit power to drive wheels 19 via final gear 16, differential gear 17, and axle 18.

The continuously variable transmission 4 includes a hydraulic circuit 20, a control unit 70
The hydraulic circuit 20 is operated by the line pressure from the control unit 70 and the duty signal for speed change control to control the hydraulic pressure of the primary cylinder 9 and the secondary cylinder 10.

Referring to FIG. 1, a hydraulic control system including a hydraulic circuit 20 will be described. An oil pump 21 driven by the engine 1 is provided, and a line pressure oil passage 22 on the discharge side of the oil pump 21 communicates with the secondary cylinder 10. Further, it communicates with the line pressure control valve 40 and the steady-state shift control valve 50, and the steady-state shift control valve 50 communicates with the primary cylinder 9 via the oil passage 23. The drain oil passage 24 from the steady-state shift control valve 50 communicates with the oil pan 26 with a check valve 25 for preventing the oil in the primary cylinder 9 from being completely drained and 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, and the oil passage 27 upstream of the lubrication valve 28 Of the lubrication nozzle 29. Further, a pre-filling oil passage 30 is communicated between the drain oil passages 24 and 27 upstream of the check valve 25 and the lubrication valve 28 by bypass.

The line pressure control valve 40 includes a valve body 41, a spool 42, a spool
There is provided a spring 43 for urging one of the ports 42. The spool 42 communicates the port 41a of the oil passage 22 with the port 41b of the drain oil passage 27 to regulate the pressure. A line pressure opposes a port 41c of the spool 42 adjacent to the port 41a by an oil passage 36 branched from the oil passage 22.

Here, an oil passage 31 branched from the line pressure oil passage 22 has an orifice 32 and communicates with the solenoid valve 60 in order to make the line pressure the original pressure of the duty pressure for line pressure control. Then, the solenoid valve 60 generates a pulse-shaped hydraulic pressure based on the duty signal from the control unit 70, and this generates
The duty pressure is smoothed to a predetermined level, and this duty pressure is supplied to the ports 41d and 41e of the line pressure control valve 40 via the oil passage 37, and the difference between the pressure receiving areas of the corresponding spools of the ports 41d and 41e. Acts in the direction of increasing the line pressure.

An opposite side of the spring 43 from the spool 42 is received by a movable bush 44, and an adjustment screw 47 of the sensor shoe 46 is in contact with an adjustment screw 45 screwed to the bush 44. The sensor shoe 46 is movably fitted by a hollow shaft 48 through which lubricating oil passes, and is arranged, for example, in parallel with the primary pulley 7, and the movable half 7a of the primary pulley 7
And the speed ratio is detected. And, by the sensor shoe 46 mechanically connected between the pulley movable half 7a and the spring 43, the spring load is increased at the low speed stage where the gear ratio is large, and the spring load is continuously reduced as the gear ratio becomes small. Has been reduced to.

The steady-state shift control valve 50 has a valve body 51 and a spool 52, and the port 51a of the oil passage 22 is
Oil supply position communicating with port 51b of oil passage 23, and port 51b
And a drain position communicating with the port 51c of the drain oil passage 24.

Here, an oil passage 33 branched from the line pressure oil passage 31 has an orifice 34, and communicates with a port 51d at the oil discharge side end of the spool 52 to apply the line pressure as it is. An oil passage 35 branching off from the oil passage 31 has an orifice 36, and is connected to a spool 5 via a shift control solenoid valve 62 and a duty pressure oil passage 38.
The second port 51e communicates with a port 51e at the end on the refueling side to apply a duty pressure using the line pressure of the shift control solenoid valve 62 as a source pressure. It should be noted that a spring 55 for initial setting is urged on the spool 52 at the port 51e.

In this manner, the line pressure is applied to one of the spools 52 of the steady-state shift control valve 50, and the pulse-shaped duty pressure of the shift control solenoid valve 62 using the line pressure is applied to the other spool 52. The shift control is performed by always reciprocating the spool 52 only by the duty ratio of the duty pressure without being affected by the change. Therefore, by changing the duty ratio, the cylinder inflow amount together with the oil supply time or the cylinder outflow amount together with the oil discharge time changes, so that it is possible to perform shift control while changing the shift speed.

Note that the solenoid valve 60 is configured to drain oil when the duty signal is on, and therefore the duty pressure is reduced as the duty ratio increases. Thus, the line pressure has a characteristic changed as a decreasing function with respect to the duty ratio.

On the other hand, since the shift control solenoid valve 62 has the same configuration, when the duty ratio is large, the time required to switch the steady-state shift valve 50 to the refueling position is increased to shift up,
In the opposite case, the time for switching to the oil discharge position becomes longer and the gear shifts down. Then, as the deviation between the target speed ratio is and the actual speed ratio i is larger, the change in the duty ratio is larger, so that the speed of shifting up or down is controlled to be larger.

By the way, the above-mentioned steady-state shift control valve 50 has a valve diameter,
It has a small stroke and functions as a two-position valve, and reciprocates between a refueling position and a draining position in response to a duty pressure pulse output from a shift control solenoid valve 62. It is suitably configured, but has another transient transmission control valve 50 '.

The structure of the shift control valve 50 'for transition is exactly the same as that of the shift control valve 50 for steady state, and the valve diameter and stroke are larger than those of the shift control valve 50 for steady state and function as a stroke valve, and are suitable for shift characteristics in a transient state. It has become. And spool
The load of one spring 55 'of 52' is set large,
The width of the groove 52'a of the spool 52 'is formed to be narrow, and the oil passage branched from the oil passage 22 to each port similarly to the normal speed change control valve 50.
The oil passage 22 ', the oil passage 23' branched from the oil passage 23, the oil passage 24 'branched from the oil passage 24, and the oil passage 33' branched from the oil passage 31 communicate with each other.
Further, the duty pressure of the duty pressure oil passage 38 from the shift control solenoid valve 62 is sufficiently attenuated by the orifice 39 to operate.

In this manner, the two steady-state shift control valves 50 and the transient shift control valve 5 are controlled by the duty pressure of one shift control solenoid valve 62.
0 'is operated. In this case, the duty pressure with respect to the duty ratio by the shift control solenoid valve 62 is as shown in FIG. That is, when the duty ratio is too small, the level of the duty pressure becomes high due to the small drainage of the shift control solenoid valve 62, and the ports 51'b and 51'c are communicated with the transient shift control valve 50 '. Stroke can be performed to the set oil discharge position. Conversely, if the duty ratio becomes excessive, the drain increases and the level of the duty pressure decreases, and the transient shift control valve 50 'makes a slot talk to the refueling position communicating the ports 51'a and 51'b. At an intermediate duty ratio, the spool 52 'can be held in the closed position as the neutral position. From this, in the case of a downshift or upshift in a transient state, a large flow rate is ensured by changing the duty ratio of the shift control solenoid valve 62 to a small value or a large value as described above,
Speed changes with good response.

Describing the electronic control system, reference numeral 70 denotes a control unit, which inputs the engine speed, the speeds of the primary pulley and the secondary pulley, the throttle opening θ of the throttle opening sensor 69, and the like. Further, the control unit 70
It has a line pressure control unit 71 that determines a line pressure according to the transmission torque in each operation state. The line pressure control unit 71 outputs a line pressure control duty signal to the solenoid valve 60.
Further, the control unit 70 has a shift control unit 72 that determines a gear ratio from a running state, and an operation mode determination unit 73 that determines a transient state of steady and sudden acceleration / deceleration based on a change in the throttle opening θ. The duty ratio of the shift control duty signal output from 72 to the shift control solenoid valve 62 is
The duty ratio adjuster 74 corrects each mode.

Next, the operation of the thus configured hydraulic control device will be described.

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 to the secondary cylinder 10, so that a low speed stage having the maximum speed ratio is established. At this time, the line pressure is guided to both the solenoid valves 60 and 62, so that the duty pressure can be generated using the line pressure as the original pressure.

Therefore, when the gear ratio is maximum when the vehicle is idling or starting, the load of the spring 43 in the line pressure control valve 40 is set to be the largest by the sensor shoe 46, and the line pressure that balances this spring load is also determined to be large. Then, as the speed ratio decreases after the start of the speed change, the spring load also decreases, so that the line pressure decreases. Thus, the line pressure is controlled in an increasing function with respect to the speed ratio.

The line pressure is always supplied to the secondary cylinder 10 and always applies a pulley pressing force according to the transmission torque. In this state, the steady-state shift control valve 50 or the transient shift control valve 50 ′ applies the pressure to the primary cylinder 9. Gear change is controlled by supplying and discharging oil to change the primary pressure. The operation mode determination unit 73 of the control unit 70 determines the operation mode based on the change in the throttle opening θ.

Therefore, in a steady state in which the change in the throttle opening θ is small, the duty ratio from the transmission control unit 72 is adjusted to an intermediate value by the duty ratio adjustment unit 74, and a duty signal corresponding thereto is transmitted to the transmission control solenoid valve 62. Input, thereby keeping the transient shift control valve 50 'closed. On the other hand, the pulse-shaped duty pressure generated by the shift control solenoid valve 62 in accordance with the duty ratio is equal to the steady-state shift control valve.
When the duty ratio is small, the operation time at the oil discharge position is lengthened and the primary cylinder 9 is drained, thereby shifting down. Further, when the duty ratio is large, the operation time at the refueling position becomes longer, whereby the primary pressure becomes higher due to refueling and shifts up. Thus, the steady-state shift control valve 50 having a small valve diameter and a small stroke performs fine shift control by following the pulse of the duty pressure well.

Next, at the time of rapid acceleration, the duty ratio is temporarily adjusted to be excessively small by the duty ratio adjusting unit 74, whereby the level of the duty pressure of the solenoid valve 62 is increased. Therefore,
The spool 52 'of the transient speed change control valve 50' is stroked and held at the oil discharge position, and a large amount of oil is discharged from the primary cylinder 9 by this valve diameter, thus shifting down quickly. On the other hand, in the case of rapid deceleration, the duty ratio is adjusted to be excessively large, and the duty pressure level is reduced accordingly, and the spool 52 'of the transient shift control valve 50' is stroked and held at the refueling position, and a large amount of refueling is performed. And shift up in the same way. Thus, in the transient state of rapid acceleration / deceleration, the flow rate of the primary cylinder 9 is controlled in a large amount by the stroke of the transient shift control valve 50 ', and the shift is performed responsively. And the actual speed ratio i is the target speed ratio is
Is reached, the duty ratio is controlled again so that the duty pressure falls in the steady region, and the shift control by the steady-state shift control valve 50 is performed.

Although the embodiment of the present invention has been described above, the present invention is not limited to this.

〔The invention's effect〕

As described above, according to the present invention, in the electronic shift control of the continuously variable transmission, there are two shift control valves for the steady state and the transient state, and the selective operation is performed in each operation mode. It is possible to satisfy both fine shift control with good stability in the state and shift control with good responsiveness in the transient state.

Since the configuration is such that the duty ratio of one solenoid valve is adjusted and selected for the two shift control valves for steady and transient use, the hydraulic control system is simplified.

[Brief description of the drawings]

FIG. 1 is a hydraulic and electrical circuit diagram showing an embodiment of a hydraulic control device for a continuously variable transmission according to the present invention. FIG. 2 is a configuration diagram showing a drive system of the continuously variable transmission to which the present invention is applied. FIG. 3 is a characteristic diagram of the duty pressure. 4 ... continuously variable transmission, 9 ... primary cylinder, 20 ...
Hydraulic circuit, 38: Duty pressure oil passage, 39: Orifice, 50: Normal speed shift control valve, 50 '... Transient speed change control valve, 62: Shift control solenoid valve, 70: Control unit, 72: Shift control unit, 73: Operation mode determination unit, 74:
... Duty ratio adjustment unit

Claims (2)

(57) [Claims] A hydraulic control device for a continuously variable transmission that controls a shift by controlling a hydraulic pressure applied to a primary cylinder, comprising: a shift control solenoid valve for generating a pulse duty pressure in response to a duty signal from a control unit; A stationary shift control valve that operates at two positions of oil supply and oil discharge according to a pulse duty pressure from the shift control solenoid valve; and an orifice that smoothes the pulse duty pressure from the shift control solenoid valve. And a transient shift control valve whose stroke position is determined according to the duty pressure smoothed by the orifice. The stationary shift control valve and the transient shift control valve are connected in parallel to the primary cylinder. A hydraulic control device for a continuously variable transmission, wherein the hydraulic control device is in communication. 2. The transient shift control valve according to claim 1, wherein when the duty ratio of the duty signal from the control unit is larger than a first predetermined value and smaller than a second predetermined value, supply and discharge of the primary cylinder are performed. The hydraulic control device for a continuously variable transmission according to claim 1, wherein