JP2001193530A - Control device for vehicle with continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a vehicle with a continuously variable transmission capable of certainly controlling speed of a belt type continuously variable transmission at all times, in a vehicle provided with the belt type continuously variable transmission for controlling a speed ratio by using discharge pressure from an oil pump driven by an internal combustion engine, and for conducting fuel cut. SOLUTION: After fuel feeding is cut by a fuel cut means, usually if the rotational speed of an internal combustion engine detected by an engine rotational speed detecting means becomes smaller than a specified rotational speed threshold value Ne0, fuel feeding is re-started by a fuel returning means (a broken line). However, if a steep decelerating state of the vehicle is determined by a driving state determining means, the specified rotational speed threshold value is changed to a high rotation side by a threshold value changing means to re-start fuel feeding (a solid line).

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 vehicle with a continuously variable transmission, and more particularly, to a belt type continuously variable transmission which controls a shift by a discharge pressure from an oil pump driven by an internal combustion engine. The present invention relates to a control technique for a vehicle that is provided and that stops fuel for an internal combustion engine during deceleration.

[0002]

2. Related Background Art In recent years, vehicles equipped with a belt-type continuously variable transmission (CVT) capable of steplessly controlling a gear ratio using a discharge pressure from an oil pump driven by an internal combustion engine have been developed and put into practical use. Has been In addition, for the purpose of improving fuel efficiency, for example, the fuel supply to the internal combustion engine (engine) is stopped during deceleration without performing an acceleration operation (fuel cut).
A technology that combines this technology and the above-mentioned CVT has also been developed.

[0003] In a vehicle that performs such a fuel cut, when the vehicle is decelerated and the rotational speed of the internal combustion engine is reduced to a certain degree, fuel supply is restarted, thereby reducing the so-called engine stall while improving fuel efficiency. Also try to prevent it.

[0004]

By the way, in a vehicle that performs fuel cut, when the fuel supply is restarted,
Since the actual fuel injection is delayed with respect to the fuel return command, there is a problem that the rotation speed of the internal combustion engine drops and undershoot occurs. In the case of a vehicle in which a fluid coupling with a direct coupling clutch is interposed between the internal combustion engine and the CVT,
The fuel cut is performed when the direct coupling clutch is in the direct coupling state, so that the fuel cut state is maintained until the vehicle speed becomes as low as possible.On the other hand, in order to prevent a shock due to fuel return, the direct coupling of the direct coupling clutch is However, in such a vehicle, the rotational speed of the internal combustion engine undershoots as described above immediately after the direct coupling of the direct coupling clutch is released. Problem.

If the rotational speed of the internal combustion engine undershoots, the oil pump is driven by the internal combustion engine as described above. , There is a possibility that the problem that the CVT cannot be shifted properly can occur. As described above, when the CVT cannot be favorably shifted, particularly when the vehicle suddenly decelerates, the speed ratio of the CVT cannot be switched to the lowest gear (full low) before the vehicle reaches a stop after deceleration. This is not preferable because the vehicle may stop halfway and the CVT connected to the wheels can no longer be shifted, and restart may be difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and an object of the present invention is to provide a belt type control apparatus for controlling a gear ratio by using a discharge pressure from an oil pump driven by an internal combustion engine. It is an object of the present invention to provide a control device for a vehicle with a continuously variable transmission capable of always and surely controlling the speed of a belt-type continuously variable transmission in a vehicle having a continuously variable transmission and performing fuel cut.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a belt-type continuously variable transmission for controlling a speed ratio by using a discharge pressure from an oil pump driven by an internal combustion engine. After the fuel supply is stopped by the fuel stopping means, the rotation speed of the internal combustion engine normally detected by the engine rotation speed detection means becomes equal to or less than a predetermined rotation speed threshold value in the vehicle having the engine and performing the fuel cut by the fuel stopping means. Then, the fuel supply is restarted by the fuel return means, but when the driving state determination means determines that the vehicle is rapidly decelerating, the predetermined rotation speed threshold is changed to the high rotation side by the threshold changing means.

This prevents the rotational speed of the internal combustion engine from undershooting even during rapid deceleration, so that the discharge pressure of the hydraulic oil discharged from the oil pump can always be sufficiently ensured. In addition, the speed ratio of the belt-type continuously variable transmission can always be reliably switched to the lowest speed (full low) before the vehicle stops after deceleration, and the poor startability at the time of restarting is suitably eliminated. .

According to a second aspect of the present invention, in a vehicle having a fluid coupling with a direct coupling clutch between an internal combustion engine and a belt-type continuously variable transmission, the predetermined rotation speed threshold is directly coupled to the direct coupling clutch by threshold changing means. The rotation speed is changed to the high rotation speed in response to the state release command. This also prevents an undershoot in the rotation speed of the internal combustion engine due to the release of the direct connection, and ensures that the discharge pressure of the hydraulic oil discharged from the oil pump can always be sufficiently ensured. The transmission ratio of the belt-type continuously variable transmission can always be switched to the lowest speed (full low) reliably, and fuel cut is maintained to the last minute to improve fuel efficiency, but also startability at restart. The defect is suitably eliminated.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Referring to FIG. 1, there is shown a schematic configuration diagram of a control device for a vehicle with a continuously variable transmission according to the present invention, and the configuration of the control device for a vehicle with a continuously variable transmission will be described below. The drive shaft 2 of the engine (internal combustion engine) 1 has a fluid coupling 4, a forward / reverse switching clutch 6, and an input shaft (primary shaft).
A belt-type continuously variable transmission (CVT) 10 is connected to the output shaft (secondary shaft) 30 of the CVT 10 via a gear 32, a differential gear unit 34, and an axle 36. 38 are connected.

The engine 1 is, for example, a water-cooled gasoline engine. The fluid coupling 4 is a well-known torque converter, has a lock-up clutch (direct-coupled clutch) 5, and can switch between direct-coupled (lock-up) and non-direct-coupled according to the driving condition of the vehicle. ing. The clutch 6 is a friction clutch, and is disconnected when the engine 1 is brought into the neutral state mainly at the time of starting or the like. The description of the forward / reverse switching mechanism of the clutch 6 is omitted.

Further, an oil pump 42 capable of generating high-pressure oil pressure is connected to the drive shaft 2 via a transmission member 40 such as a gear unit or a chain.
An oil passage 46 is connected to 2. That is, when the engine 1 is driven and the oil pump 42 operates, the oil pump 42 changes the oil (operating oil) stored in the oil pan 44 to a high oil pressure and discharges the oil to the oil passage 46.

The CVT 10 is configured such that an endless V-belt 27 is wound around a primary pulley unit 12 and a secondary pulley unit 20, and the drive shaft 2 is connected to the primary pulley unit 12. More specifically, the primary pulley unit 12 and the secondary pulley unit 20 each have a fixed sheave 14 whose contact surface with the V-shaped both sides of the V-belt 27 is tapered so as to be along the both sides of the V-shaped belt. And a movable sheave 16, a fixed sheave 22, and a movable sheave 24. A hydraulic actuator 18 is provided on the movable sheave 16 on the primary side, and a hydraulic actuator 26 is provided on the movable sheave 24 on the secondary side. The movable sheave 16 and the movable sheave 24 are respectively operated by the hydraulic actuator 18 and the hydraulic actuator 26. When slid along the input shaft 8 and the output shaft 30, the groove width of the primary pulley unit 12 and the secondary pulley unit 20, that is, V
The effective diameter of the belt 27 changes, so that the speed ratio of the CVT 10 changes to perform the speed change.

More specifically, the oil passage 46 is connected to the hydraulic actuator 26 on the secondary side, and a spool branched from the oil passage 46 and driven and controlled by an electromagnetic solenoid 51 is connected to the hydraulic actuator 18 on the primary side. The oil passage 48 provided with the valve 50 is connected. That is, the oil amount adjusted by the spool valve 50 for gear ratio control is supplied to the hydraulic actuator 18 on the primary side.

As shown in FIG. 1, a spool valve 52 driven and controlled by an electromagnetic solenoid 53 is interposed in the oil passage 46. The spool valve 52 adjusts the oil pressure in the oil passage 46, that is, the magnitude of the line pressure supplied to the hydraulic actuator 26 on the secondary side. The excess oil regulated by the spool valve 52 needs lubrication. To be sent to other parts.

Since the CVT 10 is a known one, its detailed structure is not described here.
In the vicinity of the drive shaft 2 of the engine 1, the rotation of the drive shaft 2 causes the engine rotation speed (engine rotation speed detection means) Ne.
Is provided with an engine rotation sensor 60 for detecting
In the vicinity of the primary pulley unit 12, a CVT 10
A primary rotation sensor 62 for detecting the rotation speed of the input shaft 8, that is, the primary rotation speed Np.
In the vicinity of the gear 32 connected to the output shaft 30, CVT1
A secondary rotation sensor 64 is provided to detect the rotational speed of the secondary pulley unit 20, ie, the secondary rotational speed Ns, and also to detect the vehicle speed V. Further, a hydraulic pressure sensor 66 for detecting the hydraulic pressure in the oil passage 46 is provided near the hydraulic actuator 26 in the oil passage 46.

Electronic control unit (ECU) 70
Is a main control device which comprises a central processing unit (CPU) and controls various types of vehicles such as the engine 1. The input side of the main control device includes the above-described engine rotation sensor 60, primary rotation sensor 62, and secondary rotation sensor 64. , Oil pressure sensor 6
6 are connected, and furthermore, an accelerator position sensor (APS) 74 for detecting an operation amount of an accelerator pedal 72 for adjusting the output of the engine 1, that is, an accelerator opening θacc, a vehicle braking operation, That is, a brake switch (brake SW) 78 for detecting an operation (ON or OFF) of a brake pedal 76 for operating a brake (not shown) is connected.

On the other hand, the output side of the ECU 70 is connected to an electromagnetic throttle valve and an ignition coil (both not shown) of the engine 1 and the electromagnetic solenoids 51 and 53 and the like. Hereinafter, the operation of the thus-configured control device for a vehicle with a continuously variable transmission according to the present invention will be described. In the vehicle with a continuously variable transmission, when the vehicle is running stably, the lock-up clutch 5 is in a directly connected state, and under this directly connected state, the primary rotation sensor 62, the secondary rotation sensor 64, the APS 74 Based on the above, there is no acceleration instruction (the engine torque is on the negative side), and
When the deceleration is equal to or more than a predetermined value (operating state determining means), the fuel supply to the engine 1 is stopped, that is, the fuel is cut off (fuel stopping means). As a result, fuel consumption is reduced, fuel efficiency is improved, and exhaust gas is reduced.

This fuel cut is performed at a vehicle speed V
At the time when the engine speed Ne decreases to a certain level and becomes equal to or lower than a predetermined value Ne0 (predetermined rotation speed threshold value), that is, the fuel supply is restarted (fuel recovery) (fuel recovery). means). At this time, in order to prevent the vibration generated when the fuel supply is restarted from being transmitted to the wheels 38, the directly connected lock-up clutch 5 has the vehicle speed V, the deceleration rate, the gear ratio, and the like. The direct connection is released accordingly. Further, when the degree of deceleration is large, rapid deceleration is determined, and the direct connection of the lock-up clutch 5 is released earlier when the primary rotational speed Np and, consequently, the engine rotational speed Ne are large.

On the other hand, the fuel return is performed when the engine rotation speed Ne becomes equal to or less than the predetermined value Ne0 even during the rapid deceleration. Due to the difference between Ne and the predetermined value Ne0, the fuel supply is not restarted immediately after the direct connection of the lock-up clutch 5 is released, and the engine speed N
e will drop significantly. Further, since there is a delay from the fuel supply command to the actual supply of fuel, even if the fuel supply command is output when the engine rotation speed Ne becomes equal to or less than the predetermined value Ne0, the engine is deactivated due to this delay during rapid deceleration. The decrease in the rotation speed Ne may be promoted, and the engine rotation speed Ne may undershoot significantly.

That is, referring to FIG. 2, the time change of the engine rotation speed Ne and the presence or absence of fuel supply at the time of rapid deceleration is shown in a time chart, but after the direct connection release command of the lock-up clutch 5 is output. When a predetermined delay time t0, which is inevitably determined by mechanical elements, elapses and the direct connection of the lock-up clutch 5 is actually released, the engine speed Ne greatly decreases as shown by a broken line in FIG. Further, when the engine rotational speed Ne becomes equal to or less than the predetermined value Ne0, a fuel supply command is also output as shown by a broken line, but the actual fuel supply is delayed by a predetermined delay time t1 which is necessarily determined by mechanical elements. As a result, the drop is promoted and an undershoot occurs.

As described above, if the engine speed Ne undershoots greatly, the driving force of the oil pump 42 is reduced and the line pressure is reduced as described above, and the CVT 10 cannot be shifted sufficiently. . Therefore, in the present invention, a decrease in the line pressure caused by such a large engine rotation speed Ne and an undershoot is prevented.

That is, in the present invention, the fuel supply command is output earlier as the vehicle is in a sudden deceleration state. Specifically, the direct connection of the lock-up clutch 5 is actually released after a lapse of a predetermined delay time t0 after the output of the direct connection release command of the lock-up clutch 5, and after the lapse of the predetermined delay time t1 since the fuel supply command is output. In view of the fact that fuel is actually supplied, in the present invention,
As shown in FIG. 2, when a predetermined time t2 (t0-t1 = t2), which is a difference between the predetermined delay time t0 and the predetermined delay time t1, has elapsed since the direct connection release command was output, that is, the engine speed Ne. At the time when the value Ne1 becomes a value Ne1 on the higher rotation side than the predetermined value Ne0, a fuel supply command is output to return the fuel (threshold changing means).

Therefore, even when the vehicle is suddenly decelerating, not only the decrease in the engine speed Ne due to the release of the direct connection of the lock-up clutch 5 but also the promotion of the decrease due to the delay in fuel supply is eliminated. As shown by the solid line in FIG. 2, undershoot of the engine rotation speed Ne is suitably prevented. Therefore, the driving force of the oil pump 42 does not inadvertently decrease during the rapid deceleration of the vehicle, and the line pressure does not decrease, so that the CVT 10 can always be surely shifted.

Thus, even if the time required for the vehicle to stop after a sudden deceleration is short, the speed ratio of the CVT 10 can be reliably shifted to the lowest gear (full low). The poor startability is suitably eliminated. Also,
The direct connection release command signal is output when the sudden deceleration judgment indicates that "maintaining the direct connection state may cause engine stall" .If this command signal is used as a trigger, the fuel cut state will be maintained as long as possible. You can also improve fuel economy.

Further, the fuel supply may be restarted at the time when the direct connection release command is output, without waiting for a predetermined time t2 to elapse after the output of the direct connection release command.
In the above embodiment, when a predetermined time t2 has elapsed since the direct connection release command was output, that is, the engine speed Ne
Is restarted at the time when the value Ne1 is higher than the predetermined value Ne0, but the engine speed N at which the fuel supply is restarted regardless of the output time of the direct connection release command.
e may be set in advance by experiments or the like. That is,
The value Ne1 at which the fuel supply is restarted may be set as the predetermined value Ne1 in advance to a higher rotation side than the predetermined value Ne0.

Thus, in the above embodiment, the engine 1
Although the fluid coupling 4 having the lock-up clutch 5 is interposed between the fluid coupling 4 and the CVT 10, the present invention is not limited to this, and the present invention can be suitably applied to a type having no lock-up clutch 5. Applicable. In addition, it is needless to say that the present invention is also applicable to a type having no fluid coupling 4 or a configuration in which the fluid coupling 4 is interposed downstream of the CVT 10.

[0028]

As described above in detail, according to the control apparatus for a vehicle with a continuously variable transmission according to the first aspect of the present invention, the gear ratio is determined by using the discharge pressure from the oil pump driven by the internal combustion engine. In a vehicle having a belt-type continuously variable transmission for controlling the fuel supply and performing a fuel cut by a fuel stopping means, after the fuel supply is stopped by the fuel stopping means, usually, the rotation speed of the internal combustion engine becomes equal to or less than a predetermined rotation speed threshold value. The fuel supply is restarted by the fuel return means, but when the sudden deceleration state of the vehicle is determined, the predetermined rotation speed threshold is changed to the high rotation side.

Therefore, even during rapid deceleration, the rotation speed of the internal combustion engine can be prevented from undershooting, and the discharge pressure of the hydraulic oil discharged from the oil pump can always be sufficiently ensured. The speed ratio of the belt-type continuously variable transmission can always be reliably switched to the lowest speed (full low) before decelerating to a stop. As a result, poor startability at the time of restart can be suitably solved.

According to the control device for a vehicle with a continuously variable transmission according to the second aspect, the predetermined rotation speed threshold value is changed to the rotation speed on the high rotation side in response to a release command of the direct connection state of the direct connection clutch. I have. Therefore, it is possible to prevent the undershoot of the rotation speed of the internal combustion engine due to the release of the direct connection and to always sufficiently secure the discharge pressure of the hydraulic oil discharged from the oil pump. The speed ratio of the continuously variable transmission can always be reliably switched to the lowest speed (full low). As a result, the fuel cut can be maintained to the last and fuel efficiency can be improved, and the poor startability at the time of restarting can also be suitably solved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a control device for a vehicle with a continuously variable transmission according to the present invention.

FIG. 2 is a time chart showing a time change of the engine rotation speed Ne and the presence or absence of a fuel supply command at the time of rapid deceleration.

[Explanation of symbols]

Reference Signs List 1 engine (internal combustion engine) 4 fluid coupling 5 lock-up clutch (directly-coupled clutch) 10 belt-type continuously variable transmission (CVT) 42 oil pump 60 engine rotation sensor (engine rotation speed detecting means) 62 primary rotation sensor 64 secondary rotation sensor ( Operating state determining means) 70 Electronic control unit (ECU) 74 Accelerator position sensor (APS, operating state determining means)

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Claims (2)

[Claims] An oil pump driven by an internal combustion engine that drives a vehicle; a belt-type continuously variable transmission capable of controlling a gear ratio by using a discharge pressure of hydraulic oil discharged from the oil pump; Operating state determining means for determining an operating state; fuel stopping means for stopping fuel supply to the internal combustion engine when the operating state determining means determines that the vehicle is in a predetermined deceleration state; An engine rotational speed detecting means for detecting a rotational speed, and when the rotational speed of the internal combustion engine detected by the engine rotational speed detecting means becomes equal to or less than a predetermined rotational speed threshold after the fuel supply is stopped by the fuel stopping means. A fuel return means for resuming fuel supply; and a threshold changing means for changing the predetermined rotation speed threshold to a high rotation side when the driving state determination means determines a rapid deceleration state of the vehicle. A control device for a vehicle with a continuously variable transmission, comprising: a step; 2. A fluid coupling with a direct coupling clutch is provided between the internal combustion engine and the belt-type continuously variable transmission, and the threshold value changing unit is configured to control the predetermined rotational speed in response to a release command of a direct coupling state of the direct coupling clutch. The control device for a vehicle with a continuously variable transmission according to claim 1, wherein the threshold value is changed to a high rotation side.