JPS63121536A - Control method for continuously variable transmission with direct coupling mechanism - Google Patents

Abstract

PURPOSE:To enable the deletion of a changeover shock by changing a continuously variable transmission to a target gear ratio only when the number of revolutions of an output shaft is over a predetermined value at the time of changeover from CVT drive to direct coupling drive. CONSTITUTION:Discrimination is made the operation or the non-operation of a direct coupling drive, depending upon whether a solenoid 48 for direct coupling control is turned ON or a solenoid 46 for start control turned OFF. When the direct coupling drive is under way, a car speed corresponding thereto is compared with a predetermined car speed V0. If V<V0, a continuously variable transmission 10 is maintained in the neighborhood of a direct coupling transmission ratio iD, and a process is returned to a start point. On the other hand, if V>=V0, the probability of changeover to a CVT drive is low and therefore said transmission 10 is changed over to an intermediate gear change ratio imid.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling a continuously variable transmission with a direct coupling mechanism, and more particularly to a method for controlling the gear ratio of a continuously variable transmission during direct coupling drive.

Conventional technology and its problems Conventionally, in belt-type continuously variable transmissions, in order to improve transmission efficiency during high-speed running, a continuously variable transmission has a direct drive path with a fixed transmission ratio between the input and output shafts, and a continuously variable transmission device. For example, the one provided in parallel with the speed change path is
It is stated in the No.

However, in the case of the above-mentioned continuously variable transmission with a direct coupling mechanism, the continuously variable transmission is stopped during direct coupling drive, so when switching from direct coupling drive to continuously variable transmission drive, the continuously variable transmission suddenly starts. This causes an extremely large shock and may lead to problems such as belt damage. This problem can be solved by cutting off the connection between the continuously variable transmission and the input shaft or the output shaft during direct drive, and by keeping the continuously variable transmission close to the direct drive transmission ratio (maximum speed ratio) and allowing it to idle. In other words, since the continuously variable transmission idles during direct drive, there is no shock and there is no risk of belt damage even if the drive is abruptly switched from direct drive to continuously variable drive.

However, if the continuously variable transmission is idle near the maximum speed ratio during direct drive, the direct drive time will occupy a large portion of the total driving time, so the torque loss of the continuously variable transmission during idle cannot be ignored, resulting in fuel efficiency. becomes worse. In particular, continuously variable transmissions tend to have the largest torque loss at the highest speed ratio.

In order to solve this problem, the present applicant controlled the continuously variable transmission to a target gear ratio lower than the direct coupling transmission ratio, for example, an intermediate gear ratio (gear ratio ', 1) during direct drive, and caused it to idle. Therefore, we would like to propose a method for reducing the loss torque of a continuously variable transmission during idling (Japanese Patent Application No. 61-63801). However, when the above control method is executed, the following problems may occur. In other words, when driving at relatively low speeds such as in urban areas, the throttle opening degree often changes frequently, so even if you switch from continuously variable transmission drive to direct drive, it will immediately switch back to continuously variable transmission drive. This may lead to a situation in which the system has to switch again, forcing frequent switching. In particular, when controlling the continuously variable transmission to an intermediate gear ratio and idling during direct drive as in the above method,
When switching from direct drive to continuously variable speed drive, the gear ratios of the direct drive path and continuously variable speed path are always different, so frequent direct drive changes cause a switching shock, which impairs driving feeling. Since the speed is changed compared to the intermediate speed every time the drive is switched to direct drive, problems arise in that the V-belt deteriorates more quickly due to frequent belt ratio changes and impact loads.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems.The purpose of the present invention is to control a continuously variable transmission to a target gear ratio and idle it in order to reduce torque loss during direct drive. It is an object of the present invention to provide a control method for a continuously variable transmission with a direct coupling mechanism, which can eliminate switching shock caused by frequent direct coupling switching in the range and prevent unnecessary shift control.

Composition of the Invention In order to achieve the above object, the present invention provides a direct drive path having a fixed transmission ratio and a continuously variable transmission path having a continuously variable transmission device in parallel between the input and output shafts. In a continuously variable transmission with a direct coupling mechanism that allows the continuously variable transmission to idle, when switching from continuously variable transmission drive to direct coupling drive,
When the output shaft rotational speed is equal to or higher than the set rotational speed, the continuously variable transmission is controlled to a target speed ratio that is lower than the final speed ratio when switching to direct drive.

In other words, controlling the idling continuously variable transmission to the target gear ratio is effective only when the direct coupling state is maintained for a long time. M! In a low vehicle speed range (low output shaft rotational speed) where switching of 13 is frequently performed, control to the target gear ratio is not only unnecessary but also causes problems. Therefore, in a low vehicle speed range, even if switching to direct drive, control to the target gear ratio is not performed, thereby preventing frequent gear changes and switching shocks.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows a V-belt continuously variable transmission with a direct coupling mechanism, which is an example of the present invention, in which a crankshaft 2 of an engine 1 is connected to an input shaft 4 via a damper mechanism 3. A direct coupling clutch 5 consisting of a wet multi-plate clutch and a rotatable direct coupling drive gear 6 are provided on the input shaft 4.
The direct-coupling drive gear 6 is connected to the input shaft 4 during direct-coupling drive by a direct-coupling control valve 47, which will be described later.

An external gear 7 is fixed to the end of the input shaft 4 , and this external gear 7 meshes with an internal gear 8 fixed to the drive shaft 11 of the continuously variable transmission 10 to transfer the power of the input shaft 4 . The speed is decelerated and transmitted to the drive shaft 11.

The continuously variable transmission 10 includes a drive pulley 1 provided on a drive shaft 11.
2, a driven pulley 14 provided on the driven shaft 13, and a V-belt 15 wound between both pulleys. The drive pulley 12 has a fixed sheave '2a and a movable sheave 12b.
A torque cam device Wt16 and a compression spring 17 are provided behind the movable sheave 12b. The torque cam device 16 generates a thrust proportional to the input torque, and the compression spring 17 generates an initial thrust sufficient to prevent the V-belt 15 from loosening, and these thrusts provide the V-belt 15 with belt tension necessary for torque transmission. ing.

On the other hand, the driven pulley 14 also has a fixed sheave 14a and a movable sheave 14b, similar to the drive side boolean IJ12, and behind the movable sheave 14b is a hydraulic chamber 1 for controlling the gear ratio.
8 is provided. The hydraulic pressure to this hydraulic chamber 18 is controlled by a pulley control valve 43, which will be described later.

A hollow shaft 19 is rotatably supported on the outer periphery of the driven shaft 13, and the driven shaft 13 and the hollow shaft 19 are connected and connected by a starting clutch 20 consisting of a wet multi-disc clutch. The hydraulic pressure applied to the starting clutch 20 is controlled by a starting control valve 45, which will be described later. A forward gear 2 and a reverse gear 22 are rotatably supported on the hollow shaft 19, and a forward/reverse switching dog clutch 23 connects either the forward gear 21 or the reverse gear 22 to the hollow shaft 19. It is designed to be connected to The reverse gear 2 is attached to the reverse idler shaft 24.
A reverse idler gear 25 meshing with the reverse idler gear 26 and another reverse idler gear 26 are fixed. Further, the counter shaft 27 has a counter gear 28 that meshes with the direct drive gear 6, the forward gear 21, and the reverse idler gear 26 at the same time.
and the final reduction gear 29 are fixed, and the final reduction gear 2
9 meshes with the ring gear 31 of the differential device 30 and transmits power to the output shaft 32.

In the continuously variable transmission having the above structure, the direct coupling clutch 5, the direct coupling drive gear 6, the counter gear 28, the final reduction gear 29, and the differential device 3o constitute a direct coupling drive path, and the external gear 7, the internal gear 8, the continuously variable transmission The transmission 10, the starting clutch 20, the forward gear 21, the counter gear 28, the final reduction gear 29, and the differential device 30 constitute a continuously variable transmission path (at the time of forward movement). And the direct coupling transmission ratio i between the input shaft 4 and the output shaft 32 in the direct coupling drive path. is the maximum speed ratio 1oi between the input shaft 4 and the output shaft 32 in the continuously variable transmission path
The speed ratio is set slightly lower than n.

The pressure regulating valve 40 regulates the hydraulic pressure discharged from the oil reservoir 41 by the oil pump 42, and outputs it as line pressure to the pulley control valve 4.
31 is outputted to a start control valve 45 and a direct connection control valve 47. Pulley control valve 432 Start control valve 45 and direct control valve 4
7 has solenoids 44, 46, and 48, respectively, and the line pressure is controlled by a control signal input to each solenoid from the electronic control device 60, and the driven pulley 1
Control hydraulic pressure is output to the hydraulic chamber 4, the starting clutch 20, and the direct coupling clutch 5.

The specific structure of the control valves 43, 45, 47 may be, for example, a combination of a spool valve 49 and a solenoid valve 50 as shown in FIG. 2, or a ball-shaped valve body 51 as shown in FIG. 3 which selectively opens and closes the input boat 52 and the drain boat 53 and controls the output hydraulic pressure of the output boat 54.
It may be constructed with a single bolt type solenoid valve. In either case, if the control valves 43, 45, 47 are subjected to duty control, a control oil pressure proportional to the duty ratio can be output, so that the control valves 43, 45, 47 can output control oil pressure proportional to the duty ratio. Direct connection control can be performed freely. Note that since the direct coupling clutch 5 only performs on-off control, there is no need to perform duty control, and only 0N10FF control may be used.

FIG. 4 shows a block diagram of the electronic control device 60, and in the figure,
61 is a sensor that detects the engine rotation speed (the rotation speed of the input shaft 4), 62 is a sensor that detects the vehicle speed (the rotation speed of the output shaft 32), 63 is a sensor that detects the rotation speed of the driven shaft 13,
64 is a sensor that detects each shift position of P, R, N, D, L, 65 is a sensor that detects the throttle opening,
The engine speed sensor 61. Vehicle speed sensor 62. Driven shaft rotation speed sensor 63. Each signal from the shift position sensor 64 is input to an input interface 66, and the signal from the throttle opening sensor 65 is converted into a digital signal by an A/D converter 67.

68 is a central processing unit (CPU), 69 is a one-drive only memory (ROM) in which programs and data for controlling the pulley control valve 439, the starting control valve 45 and the direct connection control valve 47 are stored, and 70 is a memory that is sent from each sensor. Random access memory (RAM) 71 is an output interface for temporarily storing signals and parameters, and these CPU 68, ROM 69, RAM 70, output interface 71, input interface 66', and A/D converter 67 are connected to a bus. They are mutually connected by 72. The output of the output interface 71 is output as a duty control signal to the pulley control solenoid 4246 and the direct connection control solenoid 48 via the output driver buffer 3.

FIG. 5 shows a transmission diagram set in the electronic control device 60, in which i rsax is the lowest speed ratio, i min is the highest speed ratio, and 10 is the direct transmission ratio. Here, the operation from the start state to the running state will be explained with reference to FIG. First, when starting with a constant throttle opening,
The starting clutch 20 is disconnected until the engine speed reaches the target value (point A), and after reaching the point A, the starting clutch 2
0 is gradually engaged while performing slip control, and when reaching point B, the starting clutch 20 is fully engaged and the starting control shifts to shift control. In speed change control, first the lowest speed ratio 1
Accelerate along the straight line IIlax, and the engine speed is the target engine speed N according to the throttle opening at that time,
When the 0 point is reached, the engine shifts to a shift region and shifts toward a high speed ratio while maintaining the target engine speed. The gear ratio of the continuously variable transmission path is the direct transmission ratio i.

When the vehicle enters the vicinity of (point D), the starting clutch 20 is disconnected and the direct coupling clutch 5 is engaged to switch to direct coupling drive, and thereafter the vehicle travels along a straight line with a direct coupling transmission ratio of 10.

During direct drive, the continuously variable transmission 10 continues idling under no load, but the belt bending loss during idling is large at the highest and lowest speed ratios, and due to the balance between this bending loss and the gear ratio, the continuously variable transmission 10 continues to idle under no load. The loss torque when the transmission 10 is idling is the sixth
As shown in FIG. side target gear ratio, for example, intermediate gear ratio 1m1d
(i + * id = 1.0) and idle rotation to reduce torque loss. Note that the gear ratio control of the continuously variable transmission 10 during idling may be carried out by variable control of the boolean control valve 43 as in the case of continuously variable transmission driving, but since great precision is not required, it may be simply 0N10FF control. It's okay.

During direct drive, when the engine speed drops by more than a certain value than the target engine speed corresponding to the throttle opening, or when the target gear ratio determined by the throttle opening and vehicle speed deviates by more than a certain value. When this occurs, the direct coupling clutch 5 is disengaged, the starting clutch 20 is engaged, and the drive is switched to continuously variable speed drive.

In the above operation, when the gear ratio of the continuously variable transmission path enters a range close to the direct coupling transmission ratio io, the switch is made to the direct coupling drive, but at the same time as switching to the direct coupling drive, the continuously variable transmission 10 is shifted to the intermediate gear ratio i mid. When starting, you may encounter the following problems: In other words, when driving at relatively low speeds such as when driving around town, the throttle opening degree is often changed, so even if the vehicle switches to direct drive, it will immediately switch back to continuously variable speed drive. This is often the case. However, as described above, at the same time as switching to direct drive, the intermediate gear ratio i m of the continuously variable transmission 10
When shifting to ID is started, when switching again to continuously variable transmission drive, the gear ratios between the direct drive path and the continuously variable transmission path are different, causing a large switching shock and forcing frequent changes in the belt ratio. (2) The durability of the belt 15 will be impaired.

In the present invention, in order to solve this problem, when switching from continuously variable transmission drive to direct drive, the vehicle speed (output shaft rotation speed) at that time is disabled in the low vehicle speed range where the vehicle speed (output shaft rotation speed) is below the set vehicle speed (set rotation speed). The continuously variable transmission 10 is maintained near the direct transmission ratio iD without shifting to the intermediate gear ratio i mid, and conversely, in a high vehicle speed range above the vehicle speed setting, the continuously variable transmission 10 is immediately shifted to the intermediate gear ratio i mid. It is designed to change gears. In this way, even if a situation arises in which it is necessary to switch to continuously variable transmission drive immediately after switching to direct transmission drive in a low vehicle speed range, the gear ratio of continuously variable transmission 10 will still be in the vicinity of direct transmission ratio 10. Since the speed is maintained, there is no switching shock even when switching to continuously variable speed drive, and the running feeling is not impaired, and unnecessary speed changes are prevented, so ■ The durability of the belt 15 is not impaired. .

FIG. 7 is a flowchart showing a specific example of the control method of the present invention, and this control method will be specifically explained below.

First, when the control starts, it is first determined whether or not direct drive is in progress (80). Specifically, this determination is made whether the direct drive control solenoid 48 is ONL or the start control solenoid 46 is OFF. You can tell by whether or not you are doing so. If it is not in direct drive, it means that it is in continuously variable speed drive, so it is returned as is. On the other hand, if direct drive is in progress, then the vehicle speed V at that time is the set vehicle speed V. (
For example, 40 km/h) (81). If V<Vo, it means that the vehicle is running in a low speed range, and in this case, there is a high probability that it will immediately switch to continuously variable transmission drive.
The gear ratio immediately before switching the continuously variable transmission 10, that is, the direct transmission ratio i. 82) and return it. - way,
If V≧v0, it means that the vehicle is running in a high speed range, and in this case, the probability of immediately switching to continuously variable transmission drive is low, so the continuously variable transmission 10 is shifted to the intermediate gear ratio in+id. (83).

In the present invention, the target gear ratio of the continuously variable transmission during idling is an intermediate gear ratio of 1 m1d as in the embodiment.
The target speed ratio is not limited to (isid = 1), but may be set to another constant speed ratio, or the target speed ratio may be changed depending on various factors such as vehicle speed and throttle opening.

Furthermore, the switching clutch between the continuously variable speed drive and the direct drive is not limited to the wet type clutch as in the embodiment, but may also be used as a dry type clutch, an electromagnetic clutch, or a dog clutch.

Furthermore, the continuously variable transmission is not limited to the V-belt type continuously variable transmission, and other types of continuously variable transmissions, such as traction drive type continuously variable transmissions, can also be used. The direct coupling mechanism is not limited to a gear mechanism, but may also be a chain mechanism.

Effects of the Invention As is clear from the above explanation, according to the present invention, when switching from continuously variable transmission drive to direct drive, the continuously variable transmission is activated only when the output shaft rotational speed at that time is equal to or higher than the set rotational speed. Since the gear ratio is changed to the target gear ratio, even if it is necessary to switch to continuously variable transmission drive again immediately after switching to direct drive, such as in a low vehicle speed range, frequent gear changes are prevented and the continuously variable transmission It is possible to prevent deterioration of the transmission system, and also eliminate switching shock caused by the difference in gear ratio between the direct drive path and the continuously variable transmission path.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an example of a continuously variable transmission with a direct coupling mechanism to which the present invention is applicable, Figs. 2 and 3 are specific structural diagrams of a control valve, and Fig. 4 is a block diagram of an electronic control device. , FIG. 5 is a shift diagram, FIG. 6 is a loss torque characteristic diagram when the continuously variable transmission is idling, and FIG. 7 is a flowchart of an example of the control method of the present invention. ■... Engine, 4... Input shaft, 5... Directly coupled clutch, 6... Directly coupled drive gear, 10... Continuously variable transmission, 18... Hydraulic chamber, 20... Starting clutch , 32・
...Output shaft, 43...Pulley 11i1J control valve, 45.
...Start control valve, 47...Direct connection control valve, 60...Electronic control device. Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 1 Figure 2 Figure 3 Figure 4 b//l Ir Figure 5 Figure 6 Mugi&l:t. Figure 7

Claims (1)

[Claims] (1) A direct drive path with a fixed transmission ratio and a continuously variable transmission path with a continuously variable transmission are provided in parallel between the input and output shafts, and the continuously variable transmission is idled during direct drive. In a continuously variable transmission with a mechanism, when switching from continuously variable speed drive to direct drive, if the output shaft rotation speed is higher than the set rotation speed, the continuously variable transmission will be lower than the final gear ratio at the time of switching to direct drive. A control method for a continuously variable transmission with a direct coupling mechanism, characterized by controlling to a target gear ratio on the ratio side.