JP2001214972A - Shift control system for continuously variable transmission with infinite transmission gear ratio - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate arbitrary creep torque in a continuously variable transmission with infinite transmission gear ratios. SOLUTION: A shift control unit 80 for controlling a continuously variable transmission with infinite transmission ratios determines a target rotational frequency of a unit input shaft 1, that is a target engine speed tNe, at least on the basis of an accelerator pedal stroke quantity APS and a vehicle speed VSP, and sets the target engine speed tNe under an idle speed Nidle if the accelerator pedal stroke quantity APS shows the released position of 0/8 and preset operation conditions are met.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a shift control device for a continuously variable transmission with an infinite speed ratio, which is employed in a vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, a belt-type or toroidal-type continuously variable transmission mechanism is known as a vehicle transmission. In order to further expand the speed change range of such a continuously variable transmission mechanism,
2. Description of the Related Art A continuously variable transmission with an infinitely variable transmission ratio capable of controlling the transmission ratio to infinity by combining a constant transmission mechanism and a planetary gear mechanism with a continuously variable transmission mechanism is known.
No. 456, and the like.

[0003] This is a half toroidal type continuously variable transmission mechanism capable of continuously changing the transmission ratio and a constant transmission mechanism (reduction mechanism) on a unit input shaft of a continuously variable transmission having an infinite transmission ratio connected to an engine. ) Are connected in parallel, and these output shafts are connected by a planetary gear mechanism. The output of the continuously variable transmission mechanism is connected to the sun gear of the planetary gear mechanism, and the output shaft of the constant transmission mechanism is connected via a power circulation mode clutch. Connected to the carrier of the planetary gear mechanism.

[0004] The output shaft of the continuously variable transmission mechanism connected to the sun gear is selectively coupled to the unit output shaft, which is the output shaft of the infinitely variable speed ratio transmission, via a direct connection mode clutch, while the planetary gear mechanism. Are coupled to the unit output shaft.

In such a continuously variable transmission with an infinite transmission ratio,
By disengaging the direct connection mode clutch while engaging the power circulation mode clutch, the unit speed ratio (hereinafter referred to as I) according to the difference in speed ratio between the continuously variable transmission mechanism and the constant transmission mechanism.
The shift control is continuously performed with the VT ratio ii including the unit input shaft rotation speed / the unit output shaft rotation speed from a negative value to a positive value including infinity (referred to as geared neutral point GNP when 1 / ii = 0). The power circulating mode and the direct circulating mode in which the power circulating mode clutch is disengaged and the direct coupling mode clutch is engaged to perform a shift control in accordance with the gear ratio ic of the continuously variable transmission mechanism are selectively used. Can be.

[0006]

However, in the above-described transmission control apparatus for a continuously variable transmission with an infinite transmission ratio, there is no starting element such as a torque converter between the transmission and the engine, and the setting of the transmission map is as shown in FIG. The target engine speed (APS = 0/8) when the accelerator pedal is released is
The engine is set to be higher than the engine idle speed, so when starting from the geared neutral point GNP or when driving at low speed, even when trying to generate creep torque, the accelerator is released when the target engine speed is the lowest. Is larger than the idle speed of the engine, there is a problem that creep torque cannot be generated.

That is, in FIG. 7, when the line (APS = 0/8) when the accelerator pedal is released in the shift map is higher than the idle speed, the shift command to the infinitely variable speed ratio transmission is At the vehicle speed V1 in FIG.
With respect to the point, the point B becomes a target value and is output so as to increase the engine speed, in other words, to shift the IVT ratio to the Lo side.

However, in the line at the time of release of the accelerator pedal, the engine speed does not increase unless the engine brake is effective, so that the vehicle speed is reduced by the shift to the Lo side. Then, even at the decreased vehicle speed V2, since the target value of the engine speed, which is higher than the idle speed A 'point, is the B' point, the IVT ratio is further shifted to the Lo side, and finally, the IVT ratio is shifted to the Lo side. The vehicle reaches the geared neutral point GNP without producing any creep torque and stops.

The present invention has been made in view of the above problems, and has as its object to generate an arbitrary creep torque when a creep torque is required in an infinitely variable transmission.

[0010]

According to a first aspect of the present invention, a continuously variable transmission mechanism capable of continuously changing a gear ratio and a constant transmission mechanism are connected to a unit input shaft, respectively. A continuously variable transmission with an infinite speed ratio in which the output shaft of the mechanism is connected to the unit output shaft via a planetary gear mechanism, a power circulation mode clutch and a direct connection mode clutch, and a target rotation of the unit input shaft according to the driving state of the vehicle A target input shaft rotation speed setting means for setting a speed, a speed ratio control means for changing a speed ratio of the continuously variable transmission mechanism based on the target rotation speed, an engine connected to the unit input shaft, When the operating condition is satisfied, in a transmission control device for an infinitely variable speed ratio transmission including an engine control unit that sets an engine rotation speed to an idle rotation speed, the transmission ratio control unit includes: At least the target rotation speed of the unit input shaft is determined based on the accelerator pedal depression amount and the vehicle speed VSP. When the accelerator pedal depression amount is in the released state and the operating conditions set in advance are set, the target rotation speed is set to the idle speed. A creep torque control means for setting the rotation speed to less than the rotation speed is provided.

According to a second aspect of the present invention, in the first aspect, the creep torque control means includes a unit which responds to a decrease in vehicle speed when the accelerator pedal depression amount is in a released state and a predetermined operating condition is reached. Set the target rotation speed of the input shaft to a small value.

In a third aspect based on the first aspect, the speed ratio control means is configured such that, even when the accelerator pedal depression amount is in a released state, if the operating condition does not match a preset operating condition, Stop the creep torque control means.

[0014] In a fourth aspect based on the first aspect, the creep torque control means is arranged such that when the depression amount of the accelerator pedal is in a released state and a predetermined operating condition is reached, the unit is controlled when the vehicle speed is zero. While the target speed of the input shaft is minimized, when the vehicle speed reaches a preset value, the target speed is set to be equal to or higher than the idle speed.

In a fifth aspect based on the first aspect, the creep torque control means learns the idle speed of the engine and corrects the target speed of the unit input shaft according to the learning result. I do.

[0015]

Accordingly, the first aspect of the present invention is to provide a continuously variable transmission with an infinite transmission ratio connected to an engine via a unit input shaft, even if there is no starting element such as a torque converter.
When the accelerator pedal depressed amount is in the released state and the operating conditions set in advance are satisfied, by setting the target rotation speed of the unit input shaft to be lower than the idle rotation speed, an arbitrary creep torque can be set according to the difference from the idle rotation speed. As a result, it is possible to easily perform low-speed traveling such as garage entry, and it is possible to greatly improve the operability of the continuously variable transmission with an infinite gear ratio.

According to a second aspect of the present invention, when a predetermined operation condition is satisfied with the accelerator pedal depression amount released, the target rotation speed of the unit input shaft is made smaller than the idle rotation speed in accordance with the decrease in vehicle speed. By setting
The lower the vehicle speed is, the larger the creep torque can be obtained. When starting from a stopped state, the creep torque is maximized, so that low-speed traveling such as garage parking can be easily performed. Drivability can be greatly improved.

According to a third aspect of the present invention, even when the accelerator pedal is depressed, the creep torque control is stopped when the predetermined operating condition is not met, thereby preventing unnecessary creep torque from being generated. For example, during braking, it is possible to prohibit the generation of creep torque and perform quick braking.

According to a fourth aspect of the present invention, the creep torque control means includes a step of setting the target rotation speed of the unit input shaft when the vehicle speed is 0 km / h when the accelerator pedal depression amount is in a released state and a predetermined operating condition is reached. On the other hand, when the vehicle speed reaches a preset value, the target rotation speed is set to be equal to or higher than the idle rotation speed, so that the maximum creep torque is generated at the time of starting, and when the predetermined vehicle speed is reached. By setting the creep torque to zero, a creep torque similar to that of an automatic transmission using a conventional torque converter can be generated, and the driver does not feel uncomfortable.

Further, the fifth invention learns the idle speed of the engine and corrects the target speed of the unit input shaft so that the creep torque can be accurately determined irrespective of the fluctuation of the idle speed due to aging or the like. Can occur.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, a continuously variable transmission with an infinite speed ratio has a unit input shaft 1 connected to an engine.
In addition, a continuously variable transmission 2 whose gear ratio can be continuously changed, and a constant transmission 3 (reduction gear) composed of gears 3a and 3b.
And the output shafts 4, 3c
Is arranged coaxially with a unit output shaft 6 and connected by a planetary gear mechanism 5. The output shaft 4 of the continuously variable transmission 2 is connected to a sun gear 5 a of the planetary gear mechanism 5 and a direct coupling mode clutch 1.
0, and the output shaft 3c of the fixed transmission 3 is connected to the carrier 5b of the planetary gear mechanism 5 via the power circulation mode clutch 9.

The continuously variable transmission output shaft 4 connected to the sun gear 5a receives the driving force of the continuously variable transmission 2 from the sprocket 4a and the chain 4b and receives the driving force of the continuously variable transmission 2 with the infinite transmission ratio via the direct connection mode clutch 10. It is selectively coupled to a unit output shaft 6 which is an output shaft.

On the other hand, the carrier 5b selectively connected to the output shaft 3c of the fixed transmission 3 via the power circulation mode clutch 9 is connected to the unit output shaft 6 via the ring gear 5c.

The unit output shaft 6 is provided with a transmission output gear 7. The transmission output gear 7 meshes with a final gear 12 of a differential gear 8, and a drive shaft 11 connected to the differential gear 8 has a predetermined shape. The driving force is transmitted at the total reduction ratio.

As shown in FIG. 1, the continuously variable transmission 2 is a double-cavity half-toroidal type that sandwiches and presses the power rollers 20, 20 with two sets of input disks 21 and output disks 22, respectively. The output sprocket 2a interposed between the pair of output disks 22 is a sprocket 4a formed on the continuously variable transmission output shaft 4 of the unit output shaft 6 arranged in parallel with the unit input shaft 1 via a chain 4b. Connect with

The unit input shaft 1 and the CVT shaft 1b are connected in the rotational direction via a loading cam device (not shown).
And forms a gear 3a of the constant transmission 3, and the CVT shaft 1b has two sets of input disks 21, 2
1, the power rollers 20, 20 are pinched and pressed between the input and output disks by the axial pressing force generated by the loading cam device in accordance with the input torque from the unit input shaft 1.

In this infinitely variable transmission, the power circulation mode clutch 9 is disengaged while the direct coupling mode clutch 10 is engaged to change the transmission ratio ic (hereinafter C) of the continuously variable transmission 2.
VT ratio ic) and a direct connection mode in which the driving force is transmitted, and a power circulation mode clutch 9 is engaged, while the direct connection mode clutch 10 is released, so that the continuously variable transmission 2 and the constant transmission 3 are disengaged. The unit speed ratio ii (the speed ratio between the unit input shaft 1 and the unit output shaft 6; hereinafter, the IVT ratio ii)
And a power circulation mode in which control is performed almost continuously from a negative value to a positive value, including infinity.

Then, at the geared neutral point GNP in the power circulation mode where the IVT ratio ii becomes infinite, the vehicle can be started by changing the IVT ratio ii from the stopped state.

The switching between the power circulation mode and the direct connection mode is performed by setting the output shaft 4 of the continuously variable transmission 2 and the rotation speed of the output shaft 3c of the constant transmission 3 to coincide as shown in the shift map of FIG. This is performed at the rotation synchronization point RSP.

Here, as shown in FIG. 2, the shift control is performed by a shift control control unit 80 mainly composed of a microcomputer. The shift control control unit 80 operates based on the shift map shown in FIG. The IVT ratio ii is set according to the state, and as described later, a creep torque is generated at the time of starting or at a low vehicle speed such as when entering a garage.

Therefore, the transmission control control unit 80 includes an output from an input shaft rotation speed sensor 81 for detecting the rotation speed Ni of the unit input shaft 1, ie, the engine rotation speed Ne, and an output shaft rotation of the continuously variable transmission mechanism 2. The output from the CVT output shaft speed sensor 82 for detecting the number Nco, the output from the vehicle speed sensor 83 for detecting the speed of the unit output shaft 6 as the vehicle speed VSP, the accelerator pedal depression amount APS
An accelerator operation amount sensor 85 for detecting (or a throttle opening TVO) and an output BRK from a brake switch 84 for detecting that a brake pedal is depressed are input.

The vehicle speed VSP is calculated by multiplying the detected rotation speed of the unit output shaft 6 by a predetermined constant.

The shift control control unit 80 processes the detected values of these various sensors as operating conditions, and based on the accelerator pedal depression amount APS and the vehicle speed VSP,
For example, a target engine speed tNe (= target input shaft speed) is obtained from the shift map shown in FIG.
The target IVT ratio iit is determined from the SP and the continuously variable transmission 2
A step motor 36 for controlling the speed change mechanism is driven.

The engine 91 is controlled by the engine control unit 90, and controls the fuel injection amount and the ignition timing in accordance with the accelerator pedal depression amount APS and the engine speed Ne. When the amount APS is 0/8 and the vehicle speed VSP or the engine speed Ne falls below a preset value, a predetermined idle speed Nidle is set so as to be a predetermined idle speed Nidle.
Perform idle speed control.

Then, the transmission control control unit 8
0 indicates that when a preset operating condition is satisfied, FIG.
In the shift map, the IVT ratio ii is set such that the target engine speed tNe according to the creep torque control line is obtained.
The creep torque control is performed by the control of. The operating conditions for performing the creep torque control include, for example, the vehicle speed VS
When P is equal to or less than a predetermined value, the accelerator pedal depression amount APS =
0/8 and output BRK of brake switch 84 is OFF
It is when it becomes.

Here, the shift control unit 8
An example of the shift control performed at 0 will be described in detail below with reference to the flowchart of FIG. This control is executed every predetermined time, for example, every 10 msec.

First, in step S1, the accelerator pedal depression amount APS and the vehicle speed VS detected by the above-mentioned sensors are determined.
P, engine speed Ne, CVT output shaft speed Nco,
Each detection value indicating an operation state such as a signal BRK from the brake switch 84 is read.

Next, in step S2, it is determined whether or not the accelerator pedal depression amount APS = 0/8. If the accelerator pedal depression amount APS = 0/8, the process proceeds to step S3, where the creep torque is determined. While it is determined whether an operating condition for performing control is satisfied, if the accelerator pedal depression amount APS> 0/8, the process proceeds to step S5 to perform normal shift control.

In step S3, the vehicle speed VSP is
It is determined whether or not the pressure is equal to or less than 3 and the brake switch 84 is OFF, and it is determined whether or not the operating condition for performing the creep torque control is satisfied. The predetermined value V3 is, for example, 1
It is set in a low vehicle speed range such as 0 km / h.

When the operating condition for performing the creep torque control is satisfied, the routine proceeds to step S4, and in order to generate the creep torque, the target engine speed tNe is determined according to the creep torque control line shown in the map of FIG.

On the other hand, if it is determined in step S3 that the operating conditions for creep torque control are not satisfied, the process proceeds to step S5, where the accelerator pedal depression amount APS shown in the map of FIG. 8 and the vehicle speed VSP, the target engine speed tNe is calculated.

Here, the creep torque control line is shown in FIG.
As shown in FIG. 5, the target engine speed tNe is set to be smaller than the idle speed Nidle at a predetermined value V3 or less. For example, as the vehicle speed VSP approaches 0 km / h, the target engine speed tNe decreases. Is set to

In FIG. 5, at a vehicle speed V3 or lower at which the creep torque control is performed, the target engine speed tNe becomes smaller than the idle speed Nidle, and the idle speed N
The difference α between the idle and the target engine speed tNe is the difference between the engine speed Ne that determines the creep torque.

That is, as described above, when the accelerator pedal depression amount APS = 0/8 and the vehicle speed VSP is equal to or less than the predetermined value, the engine control control unit 90 performs the idle speed control, and performs the engine speed Ne.
Is maintained at the predetermined idle speed Nidle, but if the engine speed Ne is going to be smaller than the idle speed Nidle, the idle speed Nidle
In order to maintain the engine speed Ne.

However, since the IVT ratio ii is set along the creep torque control line, it is not possible to increase the engine speed Ne while maintaining a certain vehicle speed. Therefore, the vehicle speed VSP must be increased. As a result, even if the accelerator pedal depression amount APS is 0/8, a driving force and a creep torque for propelling the vehicle are generated.

When the target engine speed tNe determined by the creep torque control line is set so as to decrease as the vehicle speed VSP decreases, as in the present embodiment,
The generated creep torque is, as shown in FIG.
The maximum value is obtained when SP = 0 km / h, and decreases as the vehicle speed VSP increases and approaches a predetermined value V3. At the vehicle speed V3, the creep torque becomes 0, and the creep by the torque converter used in the conventional automatic transmission. The same characteristics as the torque can be obtained, and the starting characteristics of the continuously variable transmission with the infinite speed ratio can be made close to those of the conventional automatic transmission, so that a comfortable driving sensation can be obtained. The brake switch 8
At the time of braking when 4 is ON, rapid deceleration can be performed without generating creep torque.

After the target engine speed tNe according to the operating conditions is obtained in step S4 or S5, the process proceeds to step S6, where the target IVT ratio iit, the actual IVT ratio iir, the target CVT ratio ict, and the actual Is calculated.

The reciprocal 1 / it of the target IVT ratio ii is obtained by changing the vehicle speed VSP (output shaft speed) to the target engine speed tNe.
Is multiplied by a predetermined constant K.

Also, the reciprocal 1 / i of the actual IVT ratio iir
ir is a value obtained by dividing a vehicle speed VSP (output shaft speed) by an actual engine speed Ne and multiplying by a predetermined constant K. The constant K is a value determined according to the tire radius, the reduction ratio of the differential gear, and the like.

Similarly, the target CVT ratio ict is obtained by dividing the target engine speed tNe by the CVT output shaft speed Nco, and the actual CVT ratio icr is the engine speed Nec.
Is divided by the CVT output shaft rotation speed Nco.

Next, in step S7, the target C is obtained by feedback control of the gear ratio (for example, PI control).
After calculating the proportional component (P component) and the integral component (i component) according to the deviation between the VT ratio ict and the actual CVT ratio icr, the output step number STEP to the step motor 36 is calculated by the following equation, for example. .

STEP = G × ict + Gp × P + Gi × i where G, Gp, and Gi are gains.

The number of output steps STE thus obtained
P is output in step S8 to drive the transmission mechanism of the continuously variable transmission 2.

As described above, a creep torque control line is provided in a shift map set in advance, and when predetermined operating conditions are satisfied, the target engine speed tNe determined by the creep torque control line is changed to the idle speed. Nidl
e, the idle speed Ni
It is possible to generate the creep torque arbitrarily and easily according to the difference from dle, and it is possible to easily perform low-speed traveling such as garage parking, greatly improving the operability of the continuously variable transmission with infinite gear ratio. Can be improved.

Further, the engine control may be the same as the conventional one, and a creep torque control line is added to the shift map, and only when the operation condition of the creep torque control is satisfied when the accelerator pedal depression amount APS = 0/8. Simply determine the target engine speed tNe from the creep torque control line, and smoothly switch to the normal speed ratio control.
In addition, it can be easily performed, and the reduction of the manufacturing cost can be promoted.

In the above-described embodiment, the creep torque control line is set so as to decrease as the vehicle speed VSP decreases, but may be a fixed value.

Since the idle speed Nidle may fluctuate due to deterioration with time, the idle speed Nidle is learned and the target engine speed tNe determined by the creep torque control line is corrected.
It is possible to improve the control accuracy of the creep torque.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a continuously variable transmission with an infinite gear ratio showing an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a control device for a continuously variable transmission with an infinite speed ratio.

FIG. 3 is a flowchart illustrating an example of a shift control.

FIG. 4 shows a shift map, showing a target engine speed tNe according to an accelerator pedal depression amount APS and a vehicle speed VSP.
(Target input shaft speed).

FIG. 5 is an enlarged view of the shift map, showing a shift line for an accelerator pedal depression amount APS = 0/8 and a creep torque control line.

FIG. 6 is a graph showing a relationship between vehicle speed VSP and creep torque.

FIG. 7 shows a conventional shift map, showing a shift line with an accelerator pedal depression amount APS = 0/8, and an idle speed Ni.
This shows the relationship of dle.

[Explanation of symbols]

 Reference Signs List 1 unit input shaft 2 stepless speed change mechanism 3 constant speed change mechanism 5 planetary gear mechanism 36 step motor 80 speed change control unit 81 input shaft speed sensor 90 engine control unit 91 engine

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Claims (5)

[Claims] 1. A continuously variable transmission mechanism capable of continuously changing a gear ratio and a constant transmission mechanism are respectively connected to a unit input shaft, and an output shaft of the continuously variable transmission mechanism and the constant transmission mechanism are connected to a planetary gear mechanism and a power source. A continuously variable transmission with an infinite speed ratio connected to the unit output shaft via a circulation mode clutch and a direct connection mode clutch, and a target input shaft speed setting for setting a target speed of the unit input shaft according to the driving state of the vehicle Means, a speed ratio control means for changing a speed ratio of the continuously variable transmission mechanism based on the target speed, an engine connected to the unit input shaft, and an engine speed when predetermined operating conditions are satisfied. A transmission control device for an infinitely variable gear ratio continuously variable transmission, comprising: an engine control means for setting the speed to an idle speed. Based on the write amount and the vehicle speed VSP, and determines a target rotational speed of the unit input shaft, when it becomes an operating condition the accelerator pedal depression amount is set in advance in the release state,
A shift control device for a continuously variable transmission with an infinite speed ratio, comprising a creep torque control means for setting the target speed to be lower than the idle speed. 2. The creep torque control means sets a target rotation speed of a unit input shaft to a small value in accordance with a decrease in vehicle speed when an accelerator pedal depression amount is in a released state and a predetermined operating condition is reached. The shift control device for a continuously variable transmission with an infinite gear ratio according to claim 1. 3. The creep torque control unit according to claim 1, wherein the gear ratio control unit stops the creep torque control unit even if the accelerator pedal depression amount is in a released state if the operation condition does not match a preset operating condition. Item 3. The speed change control device for an infinitely variable speed ratio transmission according to item 1. 4. The creep torque control means, when the accelerator pedal depression amount is in a released state and a predetermined operating condition is satisfied, when the vehicle speed is 0, the target rotation speed of the unit input shaft is minimized, The transmission control device for an infinitely variable speed ratio transmission according to claim 1, wherein the target rotation speed is set to be equal to or higher than an idle rotation speed when the rotation speed reaches a preset value. 5. The transmission according to claim 1, wherein the creep torque control means learns the idle speed of the engine and corrects the target speed of the unit input shaft according to the learning result. Transmission control device for a continuously variable transmission with infinite ratio.