JP2001304306A - Clutch control device for belt-type continuously variable transmission for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excessive rotation from being inputted to an engine by abrupt down-shift, in the case of a gear ratio being held to a full-low stage by the abnormality of a belt-type continuously variable transmission. SOLUTION: This clutch control device for the belt-type continuously variable transmission detects the rotating speed Np of a primary shaft 14 by an ECU 50 and executes clutch control, on the basis of the rotating speed Np. In the state of a gear ratio being fixed in the full-low state due to generation of troubles, such as sticking of a shift control valve 42 of a hydraulic shift control system, the rotating speed Np of the primary shaft 14 is increased abruptly by the abrupt down-shift. When the rotating speed Np becomes a prescribed value N1 or more, the ECU 50 determines the abnormality of a shift mechanism and disengages a clutch 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt type continuously variable transmission for a vehicle, which is called a so-called CVT.
The present invention relates to a clutch control device for a belt-type continuously variable transmission for a vehicle for controlling a clutch connected to an engine.

[0002]

2. Description of the Related Art A belt-type continuously variable transmission of this type is connected to an engine via a clutch, and is capable of continuously changing the speed of rotation input through the clutch and outputting the rotation. Specifically, the belt-type continuously variable transmission includes, as its transmission mechanism, a primary pulley and a secondary pulley that wrap around a driving belt and hold the belt, and by adjusting the belt holding width between these pulleys, respectively. , The gear ratio is changed steplessly. Such adjustment of the belt holding width is performed, for example, by moving the movable sheave of each pulley toward and away from the fixed sheave, and increasing or decreasing the belt holding width of each pulley in accordance with the displacement amount.

While the vehicle is running, the speed change operation of the above-described belt-type continuously variable transmission is controlled according to a predetermined speed change pattern, and the speed ratio is obtained, for example, from the engine most efficiently according to the throttle opening. The rotational speed is obtained from a control map, and is continuously variably controlled to maintain the target rotational speed.

[0004]

However, if an abnormality occurs in the above-described transmission mechanism during running of the vehicle and the belt pulling width of the primary pulley suddenly shifts to the maximum side, the speed change is performed. The ratio is undesirably changed to the lowest speed side (full low) regardless of the vehicle speed condition and the like. Such a situation is the same as a sudden downshift operation of the gear ratio during traveling, and therefore, a sudden overspeed is input from the driving wheels to the engine through the transmission, In the worst case, the engine may be damaged.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a clutch control device for a belt type continuously variable transmission for a vehicle, which can execute clutch control assuming an abnormality of a transmission mechanism. It is.

[0006]

According to the present invention, a clutch control device for a belt-type continuously variable transmission for a vehicle according to the present invention detects an equivalent value of an input rotational speed transmitted through a clutch by detecting means. The above problem is solved by releasing the connection of the clutch by the clutch control means when the input rotation speed equivalent value becomes equal to or more than the predetermined value.

That is, when the gear ratio is forcibly changed to the low speed side due to the abnormality of the transmission mechanism described above, the input rotation speed of the transmission sharply increases due to the sudden downshift. Therefore, in the present invention, when the input rotation speed equivalent value becomes equal to or more than a predetermined value, it is determined that the transmission mechanism is abnormal, and the connection of the clutch is released to prevent the engine from being over-rotated.

When such clutch control is performed,
The engine rotates out of engagement with the belt-type continuously variable transmission, and is preferably stabilized at an idling rotational speed by a driver's full throttle operation. On the other hand, the vehicle coasts away from the driving force of the engine, and can preferably be decelerated by the driver's brake operation. In a more preferred embodiment,
It is assumed that the above-described clutch control means also executes control for re-engaging the clutch when the vehicle speed decreases to an extremely low speed. In this case, a value corresponding to the output rotation speed of the belt-type continuously variable transmission is further detected by the detection means, and when the output rotation speed equivalent value becomes equal to or less than a predetermined value in a low speed range, the clutch is re-engaged. And By performing such control, the vehicle can run in a low speed range even when an abnormality occurs in the transmission mechanism.

Further, in the present invention, the predetermined value in the clutch control means is set to a value higher by a predetermined excess rotation speed than the limit rotation speed for preventing over-rev in the value corresponding to the rotation speed of the engine. (Claim 2). In this case, as the value corresponding to the input rotation speed of the belt-type continuously variable transmission increases, the rotation speed of the engine becomes the limited rotation speed,
That is, when the rev limit is reached, an increase in the rotational speed of the engine is usually suppressed due to cutoff of fuel supply to the engine. Therefore, the clutch control described above is not executed unless the engine rotation speed further increases, and the vehicle can be maintained in a travelable state while the clutch is continuously connected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be embodied, for example, as a clutch control device for a belt continuously variable transmission to be mounted on a vehicle equipped with an automatic transmission. A specific embodiment will be described below. Referring to FIG. 1, a drive system of a vehicle including a belt-type continuously variable transmission is schematically illustrated. The engine 2 of the vehicle is connected to a transmission case 4, and the engine 2 is connected to a torque converter 6 inside the transmission case 4. The pump impeller 8 of the torque converter 6 is connected to a crankshaft 10 of the engine 2, while its turbine runner 12 is connected to a belt-type continuously variable transmission. The belt-type continuously variable transmission has a primary shaft 14 and a secondary shaft 16, of which the primary shaft 14 is connected to the turbine runner 12 via a clutch 18. Primary axis 1
4 and the secondary shaft 16 are each a primary pulley 2
0, a secondary pulley 22, and an endless drive belt 24 is stretched between these pulleys 20 and 22.

The secondary shaft 16 has a transfer drive gear 26, and is connected from the transfer drive gear 26 to a differential 30 through a transfer shaft 28 and a gear train thereof. The drive shaft 32 is connected to the differential 30 and extends from the transmission case 4, and is connected to drive wheels W of the vehicle. As is well known, the belt-type continuously variable transmission has movable sheaves 34 and 36 on the primary pulley 20 and the secondary pulley 22 described above, respectively. 38,39
, And the width of the pulleys 20 and 22 for the drive belt 24 is varied.

Here, the belt-type continuously variable transmission shown in FIG. 1 has, for example, a hydraulic shift control system for operating its shift mechanism. Specifically, the hydraulic shift control system has a supply path for the pressure oil supplied from the hydraulic pump 40, and this supply path is connected to the primary pulley 20 and the secondary pulley 22, respectively. The pressure oil supplied to each of the pulleys 20 and 22 through the supply path is guided to a hydraulic chamber (not shown) to press the piston, thereby moving the movable sheaves 34 and 36 in a desired displacement amount in the axial direction. it can.

The hydraulic shift control system includes a pulley 2
There is a valve for controlling the supply and discharge of the pressure oil to and from the hydraulic pumps 0 and 22. Specifically, a shift control valve 42 and a line pressure control valve 44 are interposed in the supply path connected to the pulleys 20 and 22, respectively. Have been. These control valves 42,
Each of the control ports 44 is connected to a solenoid valve (not shown), so that the positions of the valve bodies 46 and 48 can be switched by receiving control hydraulic pressure from the corresponding solenoid valve.

The hydraulic shift control system has an electronic control unit (hereinafter simply referred to as an ECU) 50 at the control center.
The ECU 50 controls the switching of the control valves 42 and 44 using the above-described solenoid valve.
This is performed based on the control signal from. The ECU 50 controls the displacement of the movable sheaves 34, 36 as desired by controlling the position switching of the control valves 42, 44 to operate the transmission mechanism. Specifically, the line pressure control valve 44 controls the pressure oil discharged from the hydraulic pump 40 to an appropriate line pressure, and
Is always appropriately controlled. On the other hand, the transmission control valve 42 is
By changing the holding width at 0, the gear ratio is changed steplessly.

While the vehicle is running, the ECU 50 operates the hydraulic shift control system appropriately in accordance with a normal shift control program to perform a shift operation by the belt-type continuously variable transmission. For example, when setting the gear ratio to a low speed side, the ECU 50 opens the discharge port of the gear change control valve 42 to discharge the hydraulic oil from the primary pulley 20, and separates the movable sheave 34 from the fixed sheave 38. The movable sheave 34 is separated from the drive belt 2 by the primary pulley 20.
Since the holding width of the secondary pulley 20 is increased and the holding width of the secondary pulley 22 is reduced in conjunction with the expansion, the speed ratio between the primary and secondary pulleys 20 and 22 is increased, that is, changed to a lower speed.

On the other hand, when shifting to a high speed side, the ECU 5
0 is the primary pulley 20 through the transmission control valve 42.
And the movable sheave 34 is brought closer to the fixed sheave 38. Such a movable sheave 3
4, the holding width of the primary pulley 20 is reduced, while the holding width of the secondary pulley 22 is increased in conjunction therewith. In this case, the speed ratio is changed to a higher speed.

The ECU 50 of the hydraulic shift control system
Has a function of detecting the input / output rotational speed of the belt-type continuously variable transmission. Specifically, rotational speed sensors 52 and 54 are arranged in the transmission case 4.
These rotation speed sensors 52 and 54 output rotation angle pulses of the primary shaft 14 and the secondary shaft 16 to the ECU 50 as sensor signals thereof, respectively. The ECU 50 receives the sensor signals from the rotation speed sensors 52 and 54,
Rotational speed Np of primary shaft 14 and secondary shaft 16
Can be detected (detection means).

Here, the rotation speed Np of the primary shaft 14
Is detected as a value (equivalent value) corresponding to the input rotational speed of the belt-type continuously variable transmission. In the present invention, instead of the rotational speed Np, for example, the rotational speed of the clutch 18 or the rotational speed of the turbine runner 12 is used. The speed may be detected as an input rotation speed equivalent value. Further, the input rotation speed equivalent value may be obtained from the engine rotation speed, and the present invention does not particularly limit a specific detection value of the input rotation speed. Similarly, the rotation speed Ns of the secondary shaft 16
Is detected as a value corresponding to the output rotation speed of the belt-type continuously variable transmission, and the detected value is the rotation speed Ns
Other values may be used.

The ECU 50 of the hydraulic shift control system also has a function of controlling the operation of the clutch 18 described above. That is, a hydraulic path (not shown) is connected to the clutch 18, and the engagement hydraulic pressure can be supplied to and discharged from the clutch 18 through this hydraulic path. The ECU 50 controls the supply and discharge of the engagement hydraulic pressure to and from the clutch 18 so that the connection and disconnection can be controlled as desired. While the vehicle is running, E
The CU 50 executes the speed change control using the above-described hydraulic speed change control system, holds the clutch 18 in the connected state, inputs the output from the engine 2 to the belt type continuously variable transmission, and transmits the output to the drive system through the speed change mechanism. Output is enabled.

The above is a description of the ECU 50 of the hydraulic shift control system.
In addition, in the present embodiment, the ECU 50 also executes control on the clutch 18 when an abnormality occurs in the transmission mechanism due to a trouble in the hydraulic transmission control system.

[0021]

[Embodiment] The ECU 50 will be described below with reference to a specific embodiment.
The contents of the clutch control by will be described. FIG. 2 shows a flowchart of a clutch control routine executed by the ECU 50 as one embodiment, and a specific procedure will be described with reference to this flowchart.

The ECU50 is first determined rotation speed Np of the primary shaft 14 is whether or not the predetermined value N ₁ or more (Np ≧ N ₁₎ in step S10 of the control routine.
If the hydraulic shift control system is normal, this determination is not made (No), and the clutch control routine is normally returned in step S10. FIG. 3 shows an example of a shift map defined from the relationship between the rotation speed Np of the primary shaft 14 and the rotation speed Ns of the secondary shaft 16. In a belt-type continuously variable transmission, it is theoretically possible to set the speed ratio in a region between a curve (full low) shown by a solid line and a curve shown by a two-dot line in the figure, but the actual speed ratio can be set. In the speed change control, for example, an optimum speed ratio is set so that an engine output corresponding to the throttle opening can be exhibited at the most efficient rotation speed. In the example of FIG. 3, the actual operation point P is set in the gear ratio (Np ₀ / Ns ₀ ), and the hydraulic transmission control system changes the gear ratio of the belt-type continuously variable transmission to the operation point P in accordance with a normal control program. Control according to.

On the other hand, for example, when a trouble occurs in the hydraulic shift control system, and the trouble causes the speed change mechanism of the belt-type continuously variable transmission to move to the lowest speed side, that is, a situation where the speed change mechanism is fixed to full low during traveling. In this case, the rotational speed N of the primary shaft 14 is reduced due to the sudden downshift of the gear ratio.
p ₀ sharply rises to the curve shown by the solid line in FIG.

The troubles that cause such a situation include, for example, a mechanical valve stick of the shift control valve 42 and a state in which the shift control valve 42 is held at the discharge side due to an abnormality of the solenoid valve. is assumed. When any of these troubles occurs, an abnormality occurs in which the speed ratio of the belt-type continuously variable transmission remains fixed at the low speed side.
Is rapidly increased. Therefore, when an abnormality is assumed to occur based on the rotation speed Np of the primary shaft 14, the control routine proceeds to step S10.
Is satisfied (Yes), and the ECU 50 proceeds to the next step S12.

[0025] Here, the predetermined value N ₁ for performing the determination in step S10, when viewed as a value corresponding to the rotational speed on the engine speed, overspeed serving as a providing an excessive load on the engine 2 It is set as a determination threshold for defining the speed. Preferably, when the limit rotational speed set for Obarebu prevention of the engine 2 as viewed in FIG. 3 and Reburimitto Nlim, predetermined value N ₁ is set to as high a value predetermined excess speed Nov than rev limit Nlim. The specific value of the rev limit Nlim can be arbitrarily set according to the specifications of the engine 2.
In addition, the value of the excessive rotation speed Nov can be individually and specifically set in consideration of the durability of the engine 2, experimental data, and the like.

In the next step S12, the secondary shaft 1
Speed Ns of 6 is equal to or a predetermined value N ₂ or more (Ns ≧ N _2), if the determination is satisfied step S
Proceed to 14. The predetermined value N _2, for example, can be set as a determination threshold value for defining the upper limit of the normal vehicle speed range of the vehicle to hold the transmission ratio as Fururo. By performing the determination in step S12, the control routine returns when the vehicle speed is in the low speed range (No), and the reliability of the control is improved without unnecessary execution of the control. .

The above-described steps S10 and S1
If the determination at 2 is satisfied, then step S14 is executed, and the ECU 50 disconnects the clutch 18 here, that is, releases its connection (clutch control means). For this reason, the hatched area (Np ≦ N ₁ and Ns ≦ N ₂ ) in FIG. 3 is defined as the clutch cut area by executing this control routine.

Referring to FIG. 1, disconnection of the clutch 18 releases the connection of the engine 2 to the belt-type continuously variable transmission. Therefore, after this, the engine 2 is stabilized at the idle speed by, for example, releasing the accelerator pedal of the driver. On the other hand, the vehicle is released from the driving force of the engine 2 and enters a coasting state. For example, the vehicle can be decelerated and stopped by a driver's brake operation.

After releasing the clutch connection as described above, the ECU 50 releases the secondary shaft 1 in the next step S16.
It is determined whether or not the rotation speed Ns 6 has decreased to a predetermined value N ₃ or less (Ns ≦ N ₃ ). The predetermined value N _3, when viewed as a rotation speed corresponding to the rotational speed to the vehicle speed, is set as the determination threshold for defining the upper limit of extremely low speed region (e.g. 5km / h). The specific value of the predetermined value N _3, for example, can be set based on the specifications of the speed reduction ratio and a final reduction ratio of the drive system connected to the transfer drive gear 26.

The determination in step S16 is not satisfied (N
During the period o), the step S14 is repeatedly executed, during which the clutch 18 remains disconnected. When the vehicle speed decreases to the extremely low speed range, the determination in step S16 is established (Yes), and the ECU 50 then proceeds to step S18.
In step S18, the ECU 50 re-engages the clutch 18. As a result, the vehicle can start from an extremely low speed range. After performing the engagement process of the clutch 18, the ECU 50 ends the execution of the clutch control routine.

[0031] As described above, in a situation in which abnormality in the speed change mechanism is assumed, since the rotational speed Np of the primary shaft 14 is connected to the clutch 18 when it becomes a predetermined value N ₁ or more is released, the engine 2 prevents excessive rotation from being input beyond the rev limit Nlim. Further, since an excessive load is not applied to the belt-type continuously variable transmission, the drive belt 24 does not break.

Further, as described above, if the set a predetermined value N ₁ in the judgment of step S10 to a value higher than Reburimitto Nlim of the engine 2, typically fuel when the rotational speed of the engine reaches the rev limit Nlim Since the supply is cut, an increase in rotation of the engine 2 is suppressed. In this case, the rotation speed of the engine 2 is set to the rev limit N
If further increases beyond lim, the rotational speed Np of the primary shaft 14 does not reach the predetermined value N _1, step S
The determination at 10 is not established (No). Therefore, when suppression of rotation by the engine 2 can be expected, the clutch 18
Is maintained as it is, it is possible to prevent the over-rev of the engine 2 and the breakage of the drive belt 24 while keeping the vehicle in a running state as much as possible.

Further, in the present control routine, after the clutch 18 is disengaged, the clutch 18 is re-engaged in accordance with a decrease in the vehicle speed, so that security that enables the vehicle to travel after the control is completed is guaranteed. In this case, the vehicle can be moved for ensuring safety, or can be driven to a service factory by itself. In the extremely low speed range, the clutch 18
Is recombined, so that the shock during the connection is reduced.

In the above-mentioned embodiment, troubles of the transmission control valve 42 and the solenoid valve of the hydraulic transmission control system are cited as causes of the abnormality of the transmission mechanism.
It goes without saying that this clutch control functions effectively not only in the case of the trouble of the hydraulic transmission control system but also in the situation where the gear ratio is maintained on the low speed side due to other troubles.

The settings of the predetermined values N ₁ , N ₂ , N _3, etc. used in the clutch control routine of FIG. 2 can be appropriately rewritten by the ECU 50, and these values are not particularly limited. Further, when the determination in step S12 is not necessary in the clutch control routine, the execution of step S12 can be omitted. In addition, the embodiment of the present invention is not limited to the configuration of the belt-type continuously variable transmission and the drive system illustrated in FIG. 1, and the specific configuration can be variously changed or replaced.

[0036]

According to the clutch control apparatus for a belt-type continuously variable transmission for a vehicle according to the present invention, overspeeding of the engine and overloading of the transmission due to abnormality of the transmission mechanism can be effectively prevented. Therefore, these damages can be reliably avoided. In addition, if the control is executed appropriately in accordance with the overrev prevention function of the engine (claim 2), the function of clutch control can be effectively exerted while maintaining the original running state of the vehicle as much as possible. Its operation is very reasonable.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a vehicle drive system including a belt-type continuously variable transmission according to an embodiment of the present invention.

FIG. 2 is a flowchart of a clutch control routine executed by an ECU 50 in FIG.

FIG. 3 is a diagram for explaining the content of clutch control according to the embodiment in correspondence with a gear ratio map.

[Explanation of symbols]

 2 Engine 18 Clutch 20 Primary Pulley 22 Secondary Pulley 24 Drive Belt 50 ECU (Clutch Control Unit) 52 Rotation Speed Sensor (Detection Unit)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F16D 25/14 640W F term (reference) 3J050 AA02 AB07 BA03 BB13 DA01 3J057 AA03 BB03 GA02 GA49 GB13 HH01 JJ01 3J552 MA07 MA12 NA01 NB01 PA23 PA51 PB06 QA14C QA24C QB02 QC08 RA06 RC08 RC09 SA34 SA53 TA06 TB11 UA03 VA11Z VA32W VA37Z VA74W VB01Z VC01W VC03Z

Claims (2)

[Claims] Claims: 1. An engine connected via a clutch,
In a vehicle belt-type continuously variable transmission capable of continuously changing a gear ratio, detection means for detecting an input rotation speed equivalent value of the belt-type continuously variable transmission transmitted through the clutch, and A clutch control device for a belt-type continuously variable transmission for a vehicle, comprising: clutch control means for releasing the connection of the clutch when the value corresponding to the input rotation speed becomes a predetermined value or more. 2. The method according to claim 1, wherein the predetermined value is set to a value that is higher than a limit rotation speed set for preventing overrev by a predetermined excess rotation speed when viewed from a value corresponding to a rotation speed of the engine. The clutch control device for a vehicle belt-type continuously variable transmission according to claim 1.