JP2001099302A - Controller for continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a driving belt and reduce driving loss of an oil pump by preventing slip of the driving belt disposed on a continuously variable transmission in stop. SOLUTION: When a shift lever is set to traveling ranges such as a D-drive and an R-drive, it is in brake operating condition or an acceleration pedal releasing condition, and speed is zero; it is judged that a vehicle is in a brake stop condition or a flat road condition, and line pressure is drained to generate belt cramp force supplied to a secondary pulley of a continuously variable transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a continuously variable transmission that drains the line pressure of the continuously variable transmission when the vehicle is stopped.

[0002]

2. Description of the Related Art In general, in a continuously variable transmission of this type, a line pressure is applied to a movable sheave of a secondary pulley on a wheel side of a pair of pulleys around which a drive belt such as a steel belt is wound, and a line pressure is applied to an engine side. A shift control pressure obtained by reducing the line pressure is applied to the movable sheave of the primary pulley, and the shift control pressure is adjusted to a value corresponding to a required gear ratio by a differential pressure between the shift control pressure and the line pressure. Thus, the winding ratio of both pulleys is varied in inverse proportion to control the speed ratio steplessly.

[0003] The line pressure is variably controlled by electrically operating a line pressure control valve interposed in an oil passage for supplying the line pressure.
When applying the belt clamping force required for power transmission,
The pressure is set to the minimum necessary pressure that does not cause belt slip.

For example, Japanese Unexamined Patent Publication No. Hei 7-317863 discloses that a line pressure at the time of stopping is prepared for a pressure corresponding to a minimum speed ratio, that is, a sudden input torque from an engine and a reverse driving force from wheels to generate a belt slip. Don't set the minimum line pressure.

[0005]

However, in the above prior art, even if the drive loss of the oil pump is reduced and the fuel efficiency is improved, the minimum line pressure that does not cause the belt slip due to the reversal of the uphill road. Therefore, there is a limit in reducing fuel pressure by lowering the line pressure and reducing the drive loss of the oil pump.

Further, since the accelerator pedal and the throttle valve are mechanically connected to each other, even when the line pressure is not sufficiently increased at the time of start, the accelerator pedal is depressed to rapidly change the engine to the continuously variable transmission. Since a large input torque is transmitted, belt slip is likely to occur. As a result, the line pressure at the time of stopping has to be secured to some extent in preparation for restarting, and it is difficult to greatly reduce the line pressure at the time of stopping.

In view of the above circumstances, the present invention makes it possible to drastically reduce the line pressure at the time of stopping without causing belt slip, and to reduce the drive loss of the oil pump by drastically reducing the line pressure. It is an object of the present invention to provide a control device for a continuously variable transmission which can reduce the fuel consumption and improve the fuel efficiency.

[0008]

In order to achieve the above object, a first continuously variable transmission control device according to the present invention uses a secondary pulley of a continuously variable transmission and an oil discharged from an oil pump as a base pressure. A control valve for regulating the operating pressure supplied to the primary pulley; and a friction clutch for intermittently connecting the engine and the continuously variable transmission. When the vehicle is stopped, the engine and the continuously variable transmission are connected via the friction clutch. The transmission is disconnected from the transmission, and the operating pressure is drained at the control valve.

The second continuously variable transmission control device is characterized in that in the first continuously variable transmission control device, the stop is a stop on a flat road and a stop with a brake applied. I do.

A third control device for the continuously variable transmission includes a control valve for adjusting the operating pressure supplied to the secondary pulley and the primary pulley of the continuously variable transmission using the oil discharged from the oil pump as a source pressure. A friction clutch for intermittently connecting the engine and the continuously variable transmission, and an electronically controlled throttle valve for electronically controlling a throttle opening degree in an intake system. The electronically controlled throttle valve shuts off the engine and the continuously variable transmission, drains the operating pressure at the control valve, connects the friction clutch when starting, and restores the operating pressure by the operation of the control valve. Is characterized in that the throttle opening is set according to the degree of return of the operating pressure.

That is, the first continuously variable transmission control device disconnects the engine and the continuously variable transmission by releasing the friction clutch when the vehicle is stopped, and drains the operating pressure supplied to the continuously variable transmission. As a result, the drive loss of the oil pump is reduced, and the fuel efficiency is improved.

In this case, as described in the control device for the second continuously variable transmission, the stopping is limited to stopping on a flat road and stopping with the brakes applied, so that the vehicle can be stopped from the wheel side. The reverse driving force is not transmitted to the continuously variable transmission, and the slip of the drive belt wound between the two pulleys of the continuously variable transmission can be prevented.

The third continuously variable transmission control device disconnects the engine and the continuously variable transmission by releasing the friction clutch when the vehicle is stopped, drains the operating pressure supplied to the continuously variable transmission, and starts the vehicle. Sometimes, a friction clutch is connected, and the operation of the control valve gradually restores the operating pressure required for transmitting torque to both pulleys of the continuously variable transmission. At that time, the electronically controlled throttle valve arranged in the intake system By setting the throttle opening in accordance with the degree of return of the operating pressure, rapid transmission of torque to the continuously variable transmission is suppressed, and slip of the drive belt is prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the drive system and hydraulic control of the continuously variable transmission employed in the present embodiment.

In FIG. 1, reference numeral 1 denotes an engine. A throttle valve 10b connected to a throttle actuator 10a of an electronic control throttle valve 10 is interposed in an intake pipe 1a communicating with an intake port of the engine 1. The electronically controlled throttle valve 10 controls the engine output by driving a throttle actuator 10a based on an opening command from a control unit 16 to be described later and controlling the opening of the throttle valve 10b.

A crankshaft 1a of the engine 1 is connected to a forward / reverse switching device 4 provided in a power transmission device 3 via an electromagnetic clutch 2 which is an example of a friction clutch. , Continuously connected to the primary shaft 5 b of the continuously variable transmission 5.

The electromagnetic clutch 2 has a drive member 2a directly connected to the crankshaft 1a, and a driven member 2b having a built-in clutch coil 2c and directly connected to the output shaft 2d. Ic
Is supplied to the clutch coil 2c, the electromagnetic powder is magnetically coupled to the gap between the two members 2a, 2b in a chain-like manner and accumulated, and the clutch torque is transmitted by this coupling force. That is, when starting, the clutch current Ic according to the engine speed Ne is supplied to perform smooth clutch connection,
When the vehicle speed is equal to or less than the set vehicle speed, the clutch current Ic is reduced to generate the clutch disengagement or a predetermined drag torque.

The forward / reverse switching device 4 uses a well-known synchromesh mechanism or a planetary gear mechanism to determine the relationship between the output shaft 2d and the primary shaft 5b, the forward position where the output shaft 2d is directly connected to the primary shaft 5b, and the output shaft. The rotation position of 2d is reversed and switched to three positions, that is, a reverse position for transmitting to the primary shaft 5b with a predetermined speed reduction, and a neutral position for cutting both shafts 2d and 5b.

The output side of the forward / reverse switching device 4 is connected to a primary shaft 5b of the continuously variable transmission 5, and a secondary shaft 5c disposed in parallel with the primary shaft 5b.
Further, a drive shaft 7 on which a front or rear drive wheel 7a is mounted is continuously provided via a reduction gear train 6a and a differential device 6b of the final reduction device 6.

A primary pulley 5a and a secondary pulley 5d are mounted on both shafts 5b and 5c of the continuously variable transmission 5. A primary hydraulic chamber 5f and a secondary hydraulic chamber 5g are provided on the movable sheave side of the pulleys 5a and 5d. Is attached. The two pulleys 5a and 5d transmit and receive power via a driving belt 5e such as a steel belt, and the width of the pulley groove is set by the primary pressure Pp supplied to the primary hydraulic chamber 5f. The belt clamping force required for torque transmission is increased by the secondary pressure (line pressure Ps) supplied to the secondary pulley 5d.
To be given. The primary pressure Pp and the secondary pressure (line pressure Ps) are set in the control unit 16 described later based on the engine operating state.

Each of the pulleys 5a and 5d has a pulley 5a.
a primary rotation speed sensor 8 for detecting a primary rotation speed Np and a secondary rotation speed Ns, which are the rotation speeds a and 5d,
A secondary rotation speed sensor 9 is provided opposite. In this case, in the present embodiment, the vehicle speed is calculated from the secondary rotation speed Ne.

Next, the configuration of a hydraulic circuit for supplying a hydraulic pressure for controlling and operating the continuously variable transmission 5 will be described. Reference numeral 11 in FIG. 1 denotes an engine-driven or electric oil pump which sucks oil stored in an oil pan 12 and generates a high pump discharge pressure. A line pressure control valve 13, a shift control valve 14,
The secondary hydraulic chamber 5g provided adjacent to the secondary pulley 5d is connected via a line pressure oil passage 15, a line pressure oil passage 18, and a secondary pressure oil passage 17, respectively.

The pump pressure of the oil pump 11 is regulated by the line pressure control valve 13 to a line pressure Ps corresponding to the gear ratio, supplied to the secondary hydraulic chamber 5g, and a belt necessary for transmitting torque to the secondary pulley 5d. Apply clamping force. At the same time, this line pressure Ps is
Supply to

The transmission control valve 14 reduces the line pressure Ps, generates a primary pressure Pp corresponding to the transmission ratio, supplies it to the primary hydraulic chamber 5f, and varies the groove width of the primary pulley 5a to change the transmission ratio. Control.

The line pressure control valve 13 and the speed change control valve 14
Secondary solenoid 1 that operates according to the control duty ratio or control current value output from control unit 16
3a, operated by the primary solenoid 14a.

The line pressure oil passage 15 has an actual line pressure P
A line pressure sensor 21 for directly detecting s is provided.

Next, the configuration of the electronic control system of the continuously variable transmission will be described. The input side of the control unit 16 includes a primary rotational speed sensor 8 for detecting a primary rotational speed Np, a secondary rotational speed sensor 9 for detecting a secondary rotational speed Ns, a line pressure sensor 21, and an opening degree of an accelerator pedal 22 (an accelerator opening degree). θacc), a brake switch 24 that is turned ON by depressing a brake pedal, and a shift lever position (D, R,
A shift position sensor 25 for detecting P, N, etc.), an engine speed sensor (not shown) for detecting an engine speed Ne from an ignition pulse or the like, and the like, and a secondary solenoid 13a and a primary solenoid on the output side. Solenoid 14a, throttle actuator 10a of electronically controlled throttle valve 10, and electromagnetic clutch 2
Are connected.

The control unit 16 performs line pressure control of the hydraulic circuit, shift control, throttle opening control for the throttle actuator 10a, and the like based on the parameters detected by the sensors and switches.

In the line pressure control in the hydraulic circuit, the actual speed ratio i is calculated by i = Np / Ns based on the primary speed Np and the secondary speed Ns, and the engine operating state (the engine speed Ne and the target The engine torque Te is estimated based on the throttle opening θth and the like.

Then, from the required line pressure Psu per unit torque calculated based on the actual speed ratio i and the engine torque Te, a required line pressure Pd corresponding to the transmission torque is calculated by Pst = Psu · Te. A solenoid current Is is determined according to the line pressure Pd, and the solenoid current Is is used as a secondary solenoid 13a for driving the line pressure control valve 13.
To the oil pump 11 by the line pressure control valve 13.
The line pressure Ps is generated using the pump discharge pressure of FIG.

When the vehicle is stopped on a flat road or stopped with a brake applied, the line pressure control valve 13 is opened to allow the line pressure Ps to be fully drained.

In the shift control, based on the secondary rotation speed Ns and the target throttle opening degree θth, a target primary rotation speed Npd is set by a map search or the like in a relation of Ns−θth, and the target primary rotation speed Npd and the secondary rotation speed are set. Based on the number Ns, the target gear ratio is is calculated by is = Npd / Ns. In this way, the optimum target gear ratio is set according to each driving and running condition by the elements of the secondary rotation speed Ns, the actual gear ratio i, and the target throttle opening degree θth.

Based on the actual speed ratio i, the target speed ratio is, the engine torque Te, the required line pressure Psu and the line pressure Ps per unit torque at each speed ratio, the maximum torque (Ps) that can be transmitted at the current line pressure Ps. / Psu) and the torque ratio Kt between the engine torque Te and Kt = Te / (Ps / Psu), and the hydraulic pressure ratio Kp is determined by Kp = f (Kt / i).

Then, the required primary pressure Ppd required to maintain the current actual speed ratio i is obtained by Ppd = Kp · Ps.

Further, a feedback correction amount ΔPp corresponding to a deviation between the target speed ratio is and the actual speed ratio i is obtained, and a target primary pressure Pps is calculated from the required primary pressure Ppd and the feedback correction amount ΔPp according to Pps = Ppd ± ΔPp. I do.

Then, the solenoid current Ip is calculated as Ip = f
(Pps), and this solenoid current Ip is used as the primary solenoid 14a for driving the shift control valve 14.
And the transmission control valve 14 generates a primary pressure Pp using the line pressure Ps as the original pressure.

When the vehicle is stopped on a flat road or stopped with the brakes applied, the line pressure control valve 13 is opened and the line pressure Ps is in a full drain state, so the primary pressure Pp is not set. .

On the other hand, the throttle opening control for the throttle actuator 10a mainly includes the accelerator opening θac
The base value θo is corrected based on the secondary rotation speed Ne and ON / OFF of the brake switch 24 to set the target throttle opening θth. Further, at the time of starting, the target throttle opening θth is corrected in accordance with the return rate x of the line pressure Ps, thereby suppressing an increase in engine output and preventing the drive belt 5e from slipping.

The line pressure control when the vehicle stops and the throttle opening control when the vehicle starts moving are processed in accordance with the flowcharts shown in FIGS. In the stop determination routine shown in FIG.
First, in step S1, the set position of the shift lever is set to D, based on the output signal from the shift position sensor 25.
It is determined whether the vehicle is set in the stop range such as R or the stop range of P and N. If the stop range is set, the process jumps to step S6.

If the select lever is set to the travel range, the process proceeds to step S2, and the process proceeds to step S2.
In S4, it is determined whether the vehicle is in a stopped state, that is, in step S2, the output signal of the brake switch 24 is read, and it is determined whether the brake pedal is depressed. In step S3, the accelerator opening is determined. θacc is read, and it is determined whether or not the accelerator pedal 22 is depressed. In step S4, the secondary rotation speed Ns is read to determine whether or not the vehicle is stopped.

When the brake switch 24 is OFF and the brake is released and the accelerator pedal is depressed, or when the vehicle is in a normal running state where Ns ≠ 0, the process proceeds to step S5 to execute the above-described normal line pressure control. And exit the routine.

In a stationary state where the shift lever is set to the P and N stop ranges, or when the shift lever is set to the drive range and the accelerator pedal painter is in an illegal state,
When it is determined that the vehicle is stopped on a flat road with Ns = 0 or the brake is in the ON state with the brake switch 24 and the brake is on with Ns = 0, and the process proceeds to step S6, the line pressure drain control is executed. Exit the routine.

When the vehicle is at a stop with Ns = 0, the power supply to the clutch coil 2c of the electromagnetic clutch 2 is interrupted, and the electronic clutch 2 is released.

In the line pressure drain control executed in step S6, a drain signal is output to a secondary solenoid 13a for driving the line pressure control valve 13 and supplied to the line pressure control valve 13 via the line pressure oil passage 15. The discharge pressure of the oil pump 11 is drained.

Then, the secondary hydraulic chamber 5g connected to the secondary pulley d via the secondary hydraulic oil passage 17
The line pressure Ps supplied as the secondary pressure and the primary pressure Pp regulated by the shift control valve 14 using the line pressure Ps as the original pressure are drained to a maximum of zero. As a result, the driving loss of the oil pump 11 when the vehicle is stopped is reduced, and the fuel efficiency is improved. When the vehicle is stopped, the driving force of the engine 1 is not transmitted to the continuously variable transmission 5 because the electromagnetic clutch 2 is released.
e improves the durability without slipping.

When the vehicle is stopped, the accelerator pedal 22 is turned off.
When the vehicle is restarted by stepping on, the process proceeds from step S3 to step S5, and shifts to normal line pressure control.

At this time, since the line pressure Ps has a value close to zero, the opening of the electronic control throttle valve 10 is controlled until the required line pressure Pd is restored, and the output torque of the engine 1 is limited. Thus, the slip of the drive belt 5e is prevented.

The opening control of the electronically controlled throttle valve 10 is performed according to a starting control routine shown in FIG.

In this routine, first, in step S11
Thus, the minimum required line pressure Pd required at the time of starting, that is, the minimum line pressure Ps at which no slip occurs on the drive belt 5e even when a sudden torque is input from the engine 1 at the time of starting, is set.

Next, in step S12, the actual line pressure Pst detected by the line pressure sensor 21 is read, and in step S13, the required line pressure Pd is compared with the actual line pressure Pst.

Immediately after the accelerator pedal is depressed, the line pressure Ps has not yet risen sufficiently, so that Pd> Pst, so that the routine proceeds to step S14, where the line pressure return rate x is calculated based on the following equation. x = (Pst / Pd) · 100

Thereafter, the process proceeds to step S15, in which a target throttle opening degree θth is set by multiplying a basic value θo mainly set based on the accelerator opening degree θacc by a line pressure return rate x (θth = θo × x /). 100).

Then, the process proceeds to a step S17, in which a throttle opening signal corresponding to the target throttle opening θth is outputted to the throttle actuator 10a of the electronically controlled throttle valve 10, and the routine is exited.

When the actual line pressure Pst reaches the required line pressure Pd (Pd.ltoreq.Pst), the process branches from step S13 to step S16, and the target value is set based on the basic value .theta.o set mainly based on the accelerator opening .theta.acc. The throttle opening .theta.th is set, and the routine proceeds to step S17, in which a throttle opening signal corresponding to the target throttle opening .theta.th is output to the throttle actuator 10a of the electronically controlled throttle valve 10, and the routine exits.

As a result, as shown in FIG. 4, the target throttle opening θth gradually increases as the line pressure return rate x increases, and the normal control is performed at a line pressure return rate of 100%.
At that time, in a state where the line pressure Ps in the initial stage of the start is not yet sufficiently increased, the opening degree control of the throttle valve 10
Since the output torque of the engine 1 is set according to the degree of return of the line pressure Ps, even if the accelerator pedal 22 is depressed at the time of starting, abrupt engine torque is not transmitted to the continuously variable transmission 5 and the drive is performed. The slip of the belt 5e is prevented, and the durability of the drive belt 5e is improved.

The present invention is not limited to the above embodiment. For example, when the oil pump is electrically driven, the oil pump is stopped when the line pressure Ps is fully drained when the vehicle is stopped on a flat road or when the brake is stopped. Therefore, the driving loss of the oil pump can be further improved, and the fuel efficiency can be further improved.

[0057]

According to the first aspect of the invention, when the vehicle is stopped, the operating pressure supplied to the continuously variable transmission is drained, so that the driving loss of the oil pump is reduced and the fuel efficiency is improved. it can.

In this case, the stop pressure is limited to stoppage on a flat road and stoppage with a brake applied, so that the operating pressure supplied to the continuously variable transmission is drained. Even if it does, the reverse driving force from the wheel side will not be transmitted to the continuously variable transmission, and the slip of the drive belt wound between both pulleys of the continuously variable transmission can be prevented, and the drive belt The durability is improved.

According to the third aspect of the invention, in addition to the effect of the first aspect, at the time of starting, the throttle opening is controlled according to the degree of return of the operating pressure supplied to the continuously variable transmission. Accordingly, abrupt engine torque is not transmitted to the continuously variable transmission, the slip of the drive belt at the time of starting can be prevented, and the durability of the drive belt is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a drive system and a hydraulic control of a continuously variable transmission.

FIG. 2 is a flowchart showing a stop determination routine;

FIG. 3 is a flowchart showing a start control routine;

FIG. 4 is a characteristic diagram showing a relationship between a line pressure return rate and a target throttle opening.

[Explanation of symbols]

 Reference Signs List 1 engine 2 friction clutch (electromagnetic clutch) 5 stepless transmission 5a primary pulley 5d secondary pulley 10 electronic control throttle valve 11 oil pump 13, 14 control valve (line pressure control valve, shift control valve) Ps, Pp operating pressure (line Pressure, primary pressure)

Claims (3)

[Claims] 1. A control valve for adjusting an operating pressure supplied to a secondary pulley and a primary pulley of a continuously variable transmission using an oil discharged from an oil pump as a base pressure, and a control valve for controlling an engine and the continuously variable transmission. A step of intermittently interrupting the friction between the engine and the continuously variable transmission via the friction clutch when the vehicle is stopped, and the control valve drains the operating pressure. Transmission control device. 2. The stop according to claim 1, wherein the stop is a stop on a flat road and a stop with a brake applied.
The control device for a continuously variable transmission according to any one of the preceding claims. 3. A control valve for adjusting an operating pressure supplied to a secondary pulley and a primary pulley of a continuously variable transmission using oil discharged from an oil pump as a base pressure, and a control valve for controlling an engine and the continuously variable transmission. It has a friction clutch that intermittently intermittents, and an electronically controlled throttle valve that electronically controls the throttle opening in the intake system. When the vehicle is stopped, the engine and the continuously variable transmission are disconnected via the friction clutch. At the same time, the operating pressure is drained by the control valve, and at the time of starting, the friction clutch is connected and the operating pressure is restored by the operation of the control valve. A control device for a continuously variable transmission, wherein a throttle opening is set.