JP2008075838A - Start friction element control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the degradation of durability of start friction elements by suppressing heat generation of the start friction elements even when a vehicle starts at a variable speed ratio on the higher side than the lowest due to the sudden stop or the like of the vehicle. <P>SOLUTION: A transmission controller sets a torque capacity coefficient τ of the start friction elements (a forward clutch and a reverse clutch) based on the input/output rotating speed ratio (e) of the start friction elements (S2, S3), makes an increase correction of the torque capacity coefficient τ when the variable speed ratio of a CVT in starting is on the higher side than the lowest (S4), computes a torque capacity command value Twc of the start friction elements based on the torque capacity coefficient τ after corrected and engine speed Ne (engine angular speed ωe) (S5), and controls the torque capacity of the start friction elements so that the torque capacity of the start friction elements is a torque capacity command value Twc. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to control of a starting friction element that is interposed between an engine and a continuously variable transmission and is fastened when starting.

  Instead of a torque converter, start friction elements such as clutches and brakes are interposed between the engine and the transmission, and at the time of start, the start friction elements are fastened in accordance with the increase in engine rotation speed. A smooth start is realized while preventing a drop in the rotational speed.

Patent Document 1 discloses a vehicle equipped with such a starting friction element. At the time of starting, a torque capacity coefficient is set in accordance with the ratio of the input / output rotational speed of the starting friction element, and the square of the engine rotational speed is set to this. The torque capacity of the starting friction element is determined by multiplying the value.
JP-A 63-305039

  By the way, in a vehicle equipped with a continuously variable transmission (hereinafter referred to as CVT), the CVT gear ratio is returned to the maximum Lo before the vehicle stops to improve the startability at the next start.

  However, when the vehicle suddenly stops, the gear ratio cannot be returned to the maximum Lo until the vehicle stops. In such a case, the vehicle will start at the gear ratio on the Hi side of the maximum Lo at the next start. Become. At this time, the rotational speed of the input side member of the starting friction element rises to a rotational speed corresponding to the torque capacity coefficient in the same manner as the engine rotational speed, whereas the output side of the starting friction element connected to the drive wheels via the CVT The rotational speed of the member does not increase easily, the rotational speed difference between the input side member and the output side member increases, the amount of heat generated by the starting friction element increases, and the durability of the starting friction element decreases.

  The present invention has been made in view of such technical problems of the prior art. Even when the vehicle suddenly stops, the start friction element generates heat even when starting at a gear ratio on the Hi side of the maximum Lo. The purpose is to suppress and prevent the durability of the starting friction element from being lowered.

  The present invention includes a starting friction element between an engine and a continuously variable transmission, and the starting friction element is fastened together with an increase in engine rotation speed when starting, and when the vehicle is stopped, And a torque capacity coefficient setting means for setting a torque capacity coefficient of the starting friction element on the basis of an input / output rotational speed ratio of the starting friction element. Torque capacity coefficient correction means for increasing the torque capacity coefficient when the transmission ratio of the continuously variable transmission is on the Hi side with respect to the maximum Lo, and the start based on the corrected torque capacity coefficient and the engine speed A torque capacity command value calculating means for calculating a torque capacity command value of the friction element; and a torque capacity of the starting friction element so that a torque capacity of the starting friction element becomes the torque capacity command value. Comprising a torque capacity control means for Gosuru, the.

  According to the present invention, when the speed ratio of the continuously variable transmission does not return to the maximum Lo due to a sudden stop of the vehicle or the like, and the speed ratio at the time of start is higher than the maximum Lo, the torque capacity coefficient τ is corrected to increase. Therefore, the torque capacity of the starting friction element can be increased to reduce the slip amount, the heat generation amount of the starting friction element can be reduced, and deterioration of the starting friction element due to overheating can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the small gear ratio side or the high speed side is expressed as “Hi side”, and the large gear ratio side or the low speed side is expressed as “Lo side”.

  FIG. 1 is a schematic configuration diagram of a vehicle equipped with a belt type continuously variable transmission. In this vehicle, the engine 1 rotates with a torsional damper 3, a forward / reverse switching mechanism 6, a belt type continuously variable transmission (hereinafter referred to as CVT) 19, an output gear 12, a drive gear 13, a differential gear 14 and a drive shaft 15. And transmitted to the drive wheel 16.

  The torsional damper 3 is connected to an input side member connected to the output shaft 2 of the engine 1 and an output side member connected to the input shaft 5 of the forward / reverse switching mechanism 6 so as to be relatively rotatable via a torsion spring. Is done. A flywheel 4 that rotates integrally with the output side member is connected to the output side member. By interposing the torsional damper 3 between the engine 1 and the CVT 19, it is possible to reduce transmission of rotational fluctuations of the engine 1 to the CVT 19.

  The forward / reverse switching mechanism 6 includes a planetary gear 22, a forward clutch 20 (starting friction element when moving forward), and a reverse brake 21 (starting friction element when moving backward) fastened when moving backward. .

  The planetary gear 22 includes a sun gear 22s, a plurality of pinions 22p that mesh with the sun gear 22s, a ring gear 22r that meshes with the pinion 22p, and a carrier 22c that rotatably supports the pinion 22p. The sun gear 22s is connected to the driven side member and the primary pulley shaft 7 of the forward clutch 20, the carrier 22c is connected to the fixed side member of the reverse brake 21, and the ring gear 22r is connected to the drive side member of the forward clutch 20.

  The forward clutch 20 has a plurality of plates interposed between a drive side member connected to the input shaft 5 of the forward / reverse switching mechanism 6 and a driven side member connected to the primary pulley shaft 7. When the hydraulic pressure is applied to the piston that does not, the plates are pressed to enter a fastening state where power can be transmitted between the input and output, and when the hydraulic pressure acting on the piston is drained, the output side member cannot be transmitted.

  The reverse brake 21 has a plurality of plates interposed between an inner fixing member of the transmission case 23 and a fixed side member connected to the carrier 22c. When hydraulic pressure is applied to a piston (not shown), the plates are connected to each other. Is pressed and the carrier 22c is fixed to the fixed side member in a non-rotatable state, and when the hydraulic pressure acting on the piston is drained, the fixed side member and the carrier 22c are in a released state in which the carrier 22c can rotate.

  The CVT 19 is a stepless change of the gear ratio between the input and output rotations. The primary pulley 8 connected to the primary pulley shaft 7, the secondary pulley 10 connected to the secondary pulley shaft 11, the primary pulley 8, The belt 9 is provided between the secondary pulleys 10.

  The primary pulley 8 and the secondary pulley 10 have fixed sheaves 8a and 10a and movable sheaves 8b and 10b that approach and separate from the fixed sheaves 8a and 10a, respectively. A primary pulley oil chamber 33 and a secondary pulley oil chamber 34 are provided on the back surfaces of the movable sheaves 8b and 10b, respectively. By controlling the hydraulic pressure supplied to the pulley oil chambers 33 and 34 by the hydraulic control circuit 32, the movable sheaves 8b and 10b are moved closer to and away from the fixed sheaves 8a and 10a, and the belt 9 is wound around the pulleys 8 and 10. Shifting continuously without changing the arc diameter continuously.

  An output gear 12 is fixed to the secondary pulley shaft 11, and the output gear 12 is engaged with a drive gear 13 having a larger diameter than the output gear 12. A pinion of a differential gear 14 is fixed to the drive gear 13, and a side gear is engaged with the pinion from the left and right. A drive shaft 15 is connected to each side gear to drive the left and right drive wheels 16.

  The vehicle control system includes an engine controller 40 that controls the engine 1 and a transmission controller 41 that controls the forward / reverse switching mechanism 6 and the CVT 19 via a hydraulic control circuit 32.

  The engine controller 40 is connected to an engine rotation speed sensor 42 that detects the rotation speed Ne of the output shaft 2 of the engine 1 and an accelerator pedal position sensor 43 that detects the position APP of the accelerator pedal. Each pedal position information is input. These pieces of information are also input to the transmission controller 41 via the engine controller 40.

  The transmission controller 41 includes an inhibitor switch 44 that detects the position of the select lever, a primary rotational speed sensor 45 that detects the rotational speed Npri of the primary pulley 8, and a secondary rotational speed sensor 46 that detects the rotational speed Nsec of the secondary pulley 10. From these, select lever position information, primary pulley rotation speed information, and secondary pulley rotation speed information are input.

  Hydraulic fluid is pumped from the oil tank 30 to the hydraulic control circuit 32 from the oil tank 30, and the transmission controller 41 is provided with a shift control valve provided in the hydraulic control circuit 32 so that a desired gear ratio is realized. Thus, the hydraulic pressure supplied to the primary pulley oil chamber 33 is controlled, and similarly, the hydraulic pressure supplied to the secondary pulley oil chamber is controlled by a solenoid valve provided in the hydraulic pressure control circuit 32. Further, when the vehicle stops, the hydraulic pressure supplied to the primary pulley oil chamber 33 is decreased and the secondary pulley oil chamber is supplied to the primary pulley oil chamber 33 in order to return the transmission ratio of the CVT 19 to the maximum Lo until the vehicle stops completely. Increase supply hydraulic pressure.

  The transmission controller 41 controls the hydraulic pressure supplied to the forward clutch 20 and the reverse brake 21 by a solenoid valve provided in the hydraulic pressure control circuit 32. At the time of forward start, the hydraulic pressure is supplied to the forward clutch 20 to fasten the forward clutch 20, and the hydraulic pressure to the reverse brake 21 is drained to release the reverse brake 21. On the contrary, at the time of reverse start, the transmission controller 41 supplies hydraulic pressure to the reverse brake 21 to fasten the reverse brake 21, drains the hydraulic pressure to the forward clutch 20, and releases the forward clutch 20.

  During forward start, the transmission controller 41 calculates the speed ratio e (= Npri / Ne) of the forward clutch 20 based on the engine rotational speed Ne and the primary rotational speed Npri, and sets the torque capacity coefficient τ based on this. Then, the transmission controller 41 corrects the torque capacity coefficient τ by multiplying the torque capacity coefficient τ by the correction coefficient k.

  The correction coefficient k is used to make the amount of heat generated by the forward clutch 20 constant at the time of starting regardless of the gear ratio of the CVT 19 at the time of starting. The correction coefficient k is set to a larger value as the gear ratio of the CVT 19 at the time of starting is on the Hi side. Is done. However, in order to prevent the engine rotational speed Ne at the start from becoming equal to or less than the engine limit rotational speed (for example, 900 rpm), an upper limit value kmax is set for the correction coefficient k, and a correction coefficient k larger than the upper limit value kmax is set. Never set.

  Further, when the speed ratio at the time of starting is larger than a predetermined Lo-side speed ratio, for example, 2, for example, heat generation of the forward clutch 20 at the time of starting does not become a problem. Therefore, the correction coefficient k is set to 1 and the torque capacity coefficient τ Do not make corrections.

  The transmission controller 41 calculates the torque capacity command value Twc based on the corrected torque capacity coefficient τ and the engine speed Ne, and controls the hydraulic pressure supplied to the forward clutch 20 so that the torque capacity command value Twc is realized. To do. Thereby, at the time of forward start, the forward clutch 20 is fastened according to the increase in the engine rotational speed Ne.

  During reverse start, the transmission controller 41 performs similar control on the reverse brake 21. However, since the reverse speed of the reverse brake 21 is always zero and the speed ratio of the reverse brake 21 cannot be calculated, the forward / reverse switching mechanism 6 is replaced with an equivalent reduction reverse gear and clutch. A value corresponding to the speed ratio is calculated, and the above processing is performed based on this value.

  FIG. 2 is a flowchart showing the contents of control when the hydraulic pressure supplied to the forward clutch 20 is controlled at the time of forward start, and is executed by the transmission controller 41 at predetermined time intervals. Although explanation is omitted here, it is assumed that the same control is performed on the reverse brake 21 at the time of reverse start.

  This will be described. First, in step S1, the accelerator pedal position APP, the engine rotational speed Ne, and the primary rotational speed Npri are read.

  In step S2, the engine rotational speed Ne and the primary rotational speed Npri are regarded as the input rotational speed and the output rotational speed of the forward clutch 20 respectively, and the speed ratio e of the forward clutch 20 is calculated (e = Npri / Ne).

  In step S3, the map shown in FIG. 3 is searched to set the torque capacity coefficient τ according to the accelerator pedal position APP and the speed ratio e.

  According to the map shown in FIG. 3, when the accelerator pedal position APP is larger than 4/8, the engine speed Ne increases and the torque capacity increases. The torque capacity of the forward clutch 20 is prevented from becoming excessively smaller than when it is between / 8. Further, when the accelerator pedal position APP is 0, the torque capacity coefficient τ is made smaller than when the accelerator pedal position APP is between 0 and 4/8, and the forward clutch 20 is slid so that the accelerator pedal position APP is zero. This reduces the shock caused by the engine torque dropping. Further, when the accelerator pedal position APP is between 0 and 4/8, the slip amount of the forward clutch 20 is reduced to improve fuel efficiency.

  When the speed ratio e is close to 1, the torque capacity coefficient τ is decreased as the speed ratio e approaches 1, and the minimum value is taken when the speed ratio e is 1. This is to suppress the occurrence of shock by reducing the transmission torque when the forward clutch 20 changes from the slip state to the complete engagement state.

  In step S4, with reference to the table shown in FIG. 4, a correction coefficient k corresponding to the gear ratio ip of the CVT 19 at the start is set, and the torque capacity coefficient τ set in step S3 is multiplied by this correction coefficient k to generate torque. The capacity coefficient τ is corrected. The gear ratio ip of the CVT 19 at the time of start is obtained, for example, by storing the primary rotational speed Npri and the secondary rotational speed Nsec immediately before the vehicle stops in a memory in the transmission controller 41 and calculating from these values. do it.

  In step S5, the torque capacity coefficient τ corrected in step S4 is multiplied by the square value of the engine angular speed ωe (= (2π / 60) · Ne) to calculate a torque capacity command value Twc.

  In step S6, the hydraulic pressure supplied to the forward clutch 20 is controlled by the hydraulic pressure control circuit 32 so that the torque capacity of the forward clutch 20 becomes the torque capacity command value Twc corrected in step S5.

  Next, a method for setting the correction coefficient k used for correcting the torque capacity coefficient τ in step S4 will be described.

  As described above, the correction coefficient k is set so that the amount of heat generated by the forward clutch 20 at the start is constant regardless of the gear ratio of the CVT 19 at the start. The amount of heat generated by the forward clutch 20 at the time of starting is a value obtained by multiplying the transmission torque of the forward clutch 20 by the angular speed difference between the input side member and the output side member of the forward clutch 20 until the angular speed difference becomes zero after starting. It is proportional to the integrated value.

Here, the transmission torque of the forward clutch 20 will be considered. When the torque capacity coefficient becomes a steady state engine angular velocity is increased to Omegai0 when tau, the transmission torque of the forward clutch 20 at this time is τ · ωe0 ^2. Furthermore, when the torque capacity coefficient is corrected to k · τ, the engine angular velocity is lower than ωe0 (1 / √k) at ωe0, so that the transmission torque of the forward clutch 20 at this time is k · τ · {(1 / √k) ωe0} ² = τ · ωe0 ² That is, there is no change in the transmission torque of the forward clutch 20 before and after the correction of the torque capacity coefficient.

  Therefore, in order to make the heat generation amount of the transmission torque 20 at the start constant regardless of the gear ratio of the CVT 19 at the start, the angular speed difference between the input side member and the output side member of the forward clutch 20 is zero, and the angular speed difference from the start is zero. It is sufficient that the time-integrated value is constant regardless of the gear ratio of the CVT 19 at the time of starting.

  FIG. 5 shows the engine angular speed ωe (= forward clutch) when the gear ratio ip of the CVT 19 at the start is Lo (ip = ip0, solid line) and Hi (ip = ip1 <ip0, broken line). 20) and the primary pulley angular velocity ωpri (= the angular velocity of the output side member of the forward clutch 20).

The areas S _A and S _{B of the} hatched areas A and B in the figure are the time integral of the angular velocity when the speed ratio ip at the start is Lo side or Hi side, so the amount of heat generated by the transmission torque 20 at the start In order to make it constant regardless of the transmission ratio of the CVT 19, the correction coefficient k may be set so that the areas S _A and S _{B of} both regions are equal.

  First, consider the region A where the gear ratio of the CVT 19 at the start is ip0 on the Lo side. The primary pulley angular velocity ωpri after starting is expressed by the following equation (1), where t is the elapsed time from starting.

Can be expressed as α is a constant determined by the mass of the vehicle, the final gear ratio, the tire radius, and the starting clutch transmission torque capacity.

  If the engine angular velocity ωe increases to ωe0 and reaches a steady state when the torque capacity coefficient is τ, the time t0 until the primary pulley angular velocity ωpri reaches ωe0 and the angular acceleration difference becomes zero is expressed by the following equation (2 ),

It can ask for.

Therefore, the area S _{A of the} region A can be calculated by the following equation (3) if the rising delay of the engine angular velocity ωe immediately after the start is ignored.

It can ask for.

  Similarly, considering the region B where the gear ratio of the CVT 19 at the start is ip1 on the Hi side, the primary pulley angular speed ωpri after the start is expressed by the following equation (4), where t is the elapsed time from the start:

Can be expressed as When the torque capacity coefficient is corrected to k · τ by the correction coefficient k, the engine angular velocity ωe settles to (1 / √k) ωe0 lower than ωe0, so the primary pulley angular velocity ωpri reaches (1 / √k) ωe0 and the angular velocity. The time t1 until the difference becomes zero is expressed by the following equation (5),

It can ask for.

Therefore, the area S _B of region B, neglecting the rise delay of the engine angular velocity ωe immediately after starting, the following equation (6),

It can ask for.

Therefore, the correction coefficient k for equalizing the area S _A of the region _A and the area S _{B of the} region B is obtained from the equations (3) and (6):

It can be asked.

  In the above embodiment, the heat generation amount of the forward clutch 20 when the speed ratio ip at the start is 2 is the reference heat generation amount, and the heat generation amount of the forward clutch 20 is the reference heat generation even if the speed ratio ip at the start is smaller than this. The following equation (8) obtained by substituting ip0 = 2 and ip1 = ip into equation (7) so as to be a quantity:

Thus, the correction coefficient k is calculated.

  If the correction coefficient k is obtained for each speed ratio ip using equation (8), the table shown in FIG. 4 can be created.

  However, when the correction coefficient k is increased, the corrected torque capacity coefficient τ is increased and the engine rotational speed Ne is decreased. When the engine rotational speed Ne is lower than the engine limit rotational speed (for example, 900 rpm), the engine 1 can be stalled. There is sex. For this reason, an upper limit value kmax is set for the correction coefficient k so that the engine rotational speed Ne does not become lower than the engine stall limit rotational speed. .

  Further, when the start gear ratio ip is larger than a predetermined Lo-side gear ratio, for example, 2, for example, the heat generation of the forward clutch 20 at the start is not a problem, so the correction coefficient k is set to 1 and the torque capacity coefficient The correction of τ is not performed.

  Then, the effect of this invention by performing the said control is demonstrated.

  According to the present invention, the transmission controller 41 sets the torque capacity coefficient τ of the starting friction element based on the input / output rotational speed ratio e of the starting friction element (the forward clutch 20 and the reverse brake 21) (S2, S3, FIG. 3) The torque capacity coefficient τ is increased and corrected when the gear ratio ip of the CVT 19 at the start is on the Hi side with respect to the maximum Lo (S4), and the corrected torque capacity coefficient τ and the engine speed Ne (engine angular speed ωe) are corrected. ) To calculate the torque capacity command value Twc of the starting friction element (S5), and control the torque capacity of the starting friction element so that the torque capacity of the starting friction element becomes the torque capacity command value Twc (S6, claim 1). Invention described in 1.).

  Therefore, when the speed ratio of the CVT 19 does not return to the maximum Lo due to a sudden stop of the vehicle or the like and the speed ratio at the time of start is higher than the maximum Lo, the torque capacity coefficient τ is corrected to increase. By increasing the torque capacity, the amount of slip can be reduced, the amount of heat generated by the starting friction element can be reduced, and deterioration of the starting friction element due to overheating can be prevented.

  To increase the torque capacity coefficient τ, for example, a larger correction coefficient k is set as the gear ratio of the CVT 19 at the time of starting becomes Hi (FIG. 4), and the torque capacity coefficient τ is multiplied by the torque capacity coefficient τ. τ is corrected (the invention according to claim 2). At this time, if the correction coefficient k is set so that the heat generation amount of the starting friction element at the time of starting is constant regardless of the speed ratio of the CVT 19 at the time of starting, even when starting at the Hi side speed ratio, The amount of heat generated by the starting friction element at the time of starting, that is, the degree of deterioration of the starting friction element can be made the same as when starting at the Lo side gear ratio (the invention according to claim 3).

  Further, an upper limit value kmax of the correction coefficient k is set so that the engine rotational speed Ne at the time of start does not become lower than the engine limit rotational speed (the invention described in FIG. 4 and claim 4). As a result, it is possible to prevent the engine 1 from stalling due to an excessively large torque capacity due to an excessively large correction coefficient k in order to suppress the amount of heat generated by the starting friction element.

  The embodiment of the present invention has been described above, but the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. is not.

It is a schematic block diagram of the vehicle carrying a belt type continuously variable transmission. It is the flowchart which showed the control content when a transmission controller controls the hydraulic pressure supplied to a forward clutch at the time of forward start. It is a map for setting a torque capacity coefficient according to an accelerator pedal position and a speed ratio. It is a table for setting the correction coefficient k from the gear ratio at the time of start. It is a figure for demonstrating the setting method of the correction coefficient k which makes the calorific value of the forward clutch at the time of start constant.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 6 Forward / reverse switching mechanism 16 Drive wheel 19 Belt type continuously variable transmission (CVT)
20 Forward clutch (starting friction element)
21 Reverse brake (starting friction element)
40 Engine controller 41 Transmission controller 43 Accelerator pedal position sensor 44 Inhibitor switch 45 Primary rotational speed sensor 46 Secondary rotational speed sensor

Claims (4)

A starting friction element is provided between the engine and the continuously variable transmission. When starting, the starting friction element is fastened in accordance with an increase in engine rotational speed, and when the vehicle is stopped, the speed ratio of the continuously variable transmission is set to Lo. In the vehicle starting friction element control device to return to the side,
Torque capacity coefficient setting means for setting a torque capacity coefficient of the starting friction element based on an input / output rotational speed ratio of the starting friction element;
Torque capacity coefficient correction means for increasing and correcting the torque capacity coefficient when the speed ratio of the continuously variable transmission at the time of starting is on the Hi side from the maximum Lo;
Torque capacity command value calculating means for calculating a torque capacity command value of the starting friction element based on the corrected torque capacity coefficient and the engine speed;
Torque capacity control means for controlling the torque capacity of the starting friction element so that the torque capacity of the starting friction element becomes the torque capacity command value;
A starting friction element control device comprising:   The torque capacity coefficient correction means sets a larger correction coefficient as the gear ratio of the continuously variable transmission at the time of starting becomes Hi, and corrects the torque capacity coefficient by multiplying the torque capacity coefficient by the correction coefficient. The starting friction element control device according to claim 1.   The torque capacity coefficient correction means sets the correction coefficient so that the amount of heat generated by the starting friction element at the time of starting is constant regardless of the gear ratio of the continuously variable transmission at the time of starting. The starting friction element control device according to claim 2.   4. The starting friction element according to claim 3, wherein the torque capacity coefficient correction means sets an upper limit value of the correction coefficient so that the engine speed at the time of starting does not become lower than the engine limit speed. Control device.