JP2010276084A - Neutral control device of continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a neutral control device of a continuously variable transmission capable of improving fuel consumption, while restraining sliding of a transmission belt. <P>SOLUTION: A transmission ECU adjusts belt clamping force adjusting hydraulic pressure via control of a first hydraulic pressure adjusting means so that an output side variable pulley 37 of a shift mechanism part 19 sandwiches the transmission belt 38 by belt clamping force of not causing sliding in the transmission belt 38. When a vehicle 10 stops, neutral control is performed for putting an advance clutch 33 in a half-releasing state by adjusting clutch adjusting hydraulic pressure via control of a second hydraulic pressure adjusting means so that the speed ratio of rotation inputted to a torque converter 12 and rotation outputted from the torque converter 12 becomes the target speed ratio. In this neutral control, required belt torque capacity is determined so that the belt clamping force adjusting hydraulic pressure becomes a minimum value of not causing the sliding in the transmission belt 38 or a value corresponding to it, and the target speed ratio is determined based on the required belt torque capacity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a continuously variable transmission by controlling clutch adjustment hydraulic pressure so that a speed ratio of a torque converter becomes a target speed ratio in order to improve fuel efficiency when a vehicle equipped with a continuously variable transmission is stopped. The present invention relates to a neutral control device for a continuously variable transmission in which an internal clutch is in a half-released state.

  A continuously variable transmission that is interposed between a torque converter that transmits generated torque of a power source such as an engine by a fluid and a drive wheel of the vehicle and continuously (steplessly) rotates the power source. One is a belt type continuously variable transmission. This type of continuously variable transmission includes a transmission mechanism having a variable pulley and a clutch. The variable pulley is configured to vary the belt clamping pressure with respect to the transmission belt by the belt clamping pressure adjusting hydraulic pressure (secondary pressure) supplied from the pump and adjusted by the first hydraulic pressure adjusting means while the transmission belt is wound around the variable pulley. The clutch is engaged and released by a clutch adjustment oil pressure (clutch pressure) supplied from the pump and adjusted by the second oil pressure adjustment means, thereby connecting and disconnecting the torque converter and the transmission mechanism.

  In the belt type continuously variable transmission, the belt clamping pressure adjustment hydraulic pressure is adjusted through the control of the first hydraulic pressure adjusting means so that the variable pulley holds the transmission belt with the belt clamping pressure that does not cause the transmission belt to slip. At this time, the belt clamping pressure adjustment hydraulic pressure is adjusted so as not to be lower than a preset lower limit guard value, so that slippage of the transmission belt is reliably suppressed. As the lower limit card value, a value set on the basis of the time when the vehicle travels, in which a large driving force is applied, is used.

  On the other hand, as one of the control modes of the belt type continuously variable transmission, there is neutral control performed when the vehicle is stopped and the shift position is the traveling position (see Patent Document 1). The neutral control is performed for the purpose of reducing the load of the power source and improving the fuel consumption when the vehicle is stopped by setting the clutch in a half-released state. In this neutral control, the clutch adjustment hydraulic pressure is adjusted through the control of the second hydraulic pressure adjusting means so that the speed ratio between the rotation input to the torque converter and the rotation output from the torque converter becomes the target speed ratio. . Even during the neutral control, the belt clamping pressure adjustment hydraulic pressure is adjusted so as not to be lower than the lower limit guard value set on the basis of the above-described vehicle traveling time.

JP 2004-138198 A

  However, during the neutral control, the minimum value of the belt clamping pressure adjustment hydraulic pressure at which the transmission belt does not slip greatly deviates toward the low pressure side from the lower limit card value set based on the vehicle running. The actual belt clamping pressure adjustment hydraulic pressure guarded by the lower limit guard value is significantly higher than the minimum value. Therefore, the actual belt clamping pressure adjustment hydraulic pressure becomes too high during neutral control from the viewpoint of suppressing slippage of the transmission belt.

  This means that even if the clutch adjustment hydraulic pressure increases and the input torque of the belt-type continuously variable transmission increases, the transmission belt is less likely to slip. Therefore, it is not necessary to consider the belt clamping pressure adjusting hydraulic pressure when obtaining the target speed ratio of the torque converter.

  Here, a high belt clamping pressure adjustment hydraulic pressure is effective in suppressing the slippage of the transmission belt, but on the other hand, the work load of the pump increases in order to increase the belt clamping pressure adjustment hydraulic pressure. As a result, the output of the power source consumed for driving the pump increases, which is disadvantageous in terms of fuel consumption.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a neutral control device for a continuously variable transmission that can improve fuel efficiency while suppressing slippage of a transmission belt. .

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, as a transmission interposed between a torque converter for transmitting generated torque of a power source by a fluid and a drive wheel of a vehicle, a transmission belt is wound and supplied from a pump. And a transmission mechanism having a variable pulley that makes the belt clamping pressure variable by the belt clamping pressure adjustment hydraulic pressure adjusted by the first hydraulic pressure adjustment means, and supplied from the pump and adjusted by the second hydraulic pressure adjustment means A clutch that engages and disengages with clutch adjustment hydraulic pressure, and connects and disconnects between the torque converter and the transmission mechanism, so that the variable pulley sandwiches the transmission belt with a belt clamping pressure that does not cause the transmission belt to slip. Further, the present invention is applied to a belt type continuously variable transmission in which the belt clamping pressure adjustment hydraulic pressure is adjusted through the control of the first hydraulic pressure adjusting means. When the vehicle is stopped, the clutch adjustment hydraulic pressure is controlled through the control of the second hydraulic pressure adjustment means so that the speed ratio between the rotation input to the torque converter and the rotation output from the torque converter becomes a target speed ratio. A neutral control device for a continuously variable transmission including a neutral control means for adjusting the clutch to a semi-released state, wherein the neutral control means does not cause the belt clamping pressure adjustment hydraulic pressure to cause slippage in the transmission belt. The gist is to obtain a required belt torque capacity that becomes a minimum value or a value corresponding thereto, and to obtain the target speed ratio based on the required belt torque capacity.

  According to the above configuration, in the belt-type continuously variable transmission, the belt clamping pressure adjusting hydraulic pressure is controlled through the control of the first hydraulic pressure adjusting means so that the variable pulley clamps the transmission belt with the belt clamping pressure that does not cause the transmission belt to slip. Is adjusted.

  Further, when the vehicle is stopped, the clutch is controlled by the second hydraulic pressure adjusting means so that the speed ratio between the rotation input to the torque converter and the rotation output from the torque converter becomes the target speed ratio by the neutral control means. The clutch is brought into a half-released state by adjusting the adjustment hydraulic pressure.

  Further, in the neutral control means, a required belt torque capacity is obtained such that the belt clamping pressure adjustment hydraulic pressure becomes a minimum value that does not cause the transmission belt to slip or a value corresponding thereto, and the target speed ratio is determined based on the required belt torque capacity. Is required.

  Therefore, the belt clamping pressure adjustment hydraulic pressure is adjusted to the above minimum value or a value corresponding thereto, so that the belt clamping pressure adjustment hydraulic pressure becomes lower than the case where the lower limit guard value set on the basis of the vehicle running is used. As a result, the extra work of the pump is reduced, the output of the power source consumed for driving the pump is reduced, and the fuel efficiency is improved.

  In addition, by setting the target speed ratio to a value that does not exceed the required belt torque capacity, the input torque of the transmission mechanism section is not applied to the transmission mechanism section, and the transmission belt Slip is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the structure of the drive system of a vehicle about one Embodiment which actualized the neutral control apparatus of the continuously variable transmission of this invention. The block diagram which shows the hydraulic control circuit in the same embodiment. 5 is a flowchart showing a procedure for calculating a target speed ratio of a torque converter used for neutral control in the embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a drive system of the vehicle 10. The rotation of the engine 11 mounted on the vehicle 10 as a power source is transmitted to the differential gear device 16 via a torque converter (T / C) 12, a belt type continuously variable transmission (CVT) 14, and a reduction gear 15. The left and right drive wheels 17 are distributed.

  The torque converter 12 includes a pump impeller 22 connected to the output shaft 21 of the engine 11, and a turbine impeller 24 connected to a belt type continuously variable transmission (CVT) 14 via a turbine shaft (output shaft) 23. The rotation transmission between the pump impeller 22 and the turbine impeller 24 is performed via the fluid. In other words, the torque converter 12 transmits the torque generated by the engine 11 by fluid. A mechanical oil pump 25 is connected to the pump impeller 22. The oil pump 25 is driven based on the rotation of the pump impeller 22 (engine rotation), and discharges oil for hydraulically driving the belt type continuously variable transmission 14. Note that the oil discharge pressure of the oil pump 25 increases as the torque of the output shaft 21 of the engine 11 (engine torque TE) increases.

  The belt type continuously variable transmission 14 is hydraulically driven by controlling the hydraulic pressure acting on the belt type continuously variable transmission 14 through a hydraulic pressure control circuit 26 (see FIG. 2). The belt-type continuously variable transmission 14 includes a forward / reverse switching device 18 and a transmission mechanism 19. The forward / reverse switching device 18 reverses the input rotation of the speed change mechanism 19 between forward rotation and reverse rotation by hydraulic drive, or interrupts the rotation input to the speed change mechanism 19. Further, the speed change mechanism unit 19 changes a gear ratio, which will be described later, or adjusts a belt clamping pressure by hydraulic drive.

  The forward / reverse switching device 18 meshes with the sun gear 27 that is connected to the turbine shaft 23 so as to rotate integrally, a ring gear 28 that is rotatably supported concentrically with the sun gear 27, and rotates between the sun gear 27 and the ring gear 28. And a plurality of planetary gears 29. The planetary gears 29 are connected to each other by a carrier 32 connected to the input shaft 31 of the speed change mechanism unit 19, and rotate integrally along the outer periphery of the sun gear 27 and the inner periphery of the ring gear 28.

  The forward / reverse switching device 18 also allows or prohibits rotation of the forward gear 33 and the ring gear 28 that are engaged and released to connect and disconnect the turbine shaft 23 and the carrier 32 (input shaft 31). A reverse brake 34 that is engaged and released is provided. The forward clutch 33 and the reverse brake 34 are driven and engaged and released based on the operation of a shift lever (not shown) by the driver.

  For example, when the shift position is set to the forward travel position by operating the shift lever, the forward clutch 33 is engaged and the turbine shaft 23 and the carrier 32 are directly connected, and the reverse brake 34 is released to rotate the ring gear 28. Is allowed. Therefore, as the sun gear 27 rotates, each planetary gear 29 (carrier 32) rotates in the same direction as the sun gear 27, and the input shaft 31 of the speed change mechanism unit 19 rotates in the forward rotation direction.

  When the shift position is changed to the reverse travel position by operating the shift lever, the forward clutch 33 is released, the direct connection between the turbine shaft 23 and the carrier 32 is released, and the reverse brake 34 is engaged to engage the ring gear 28. Rotation is prohibited. Therefore, as the sun gear 27 rotates, each planetary gear 29 (carrier 32) rotates in the opposite direction to the sun gear 27, and the input shaft 31 of the transmission mechanism unit 19 rotates in the reverse rotation direction.

  Further, when the shift position is set to the neutral position by operating the shift lever and both the forward clutch 33 and the reverse brake 34 are released, the rotation of the sun gear 27 is transmitted as the rotation of the ring gear 28 via each planetary gear 29. Therefore, the carrier 32 is not rotated, and the input shaft 31 of the speed change mechanism unit 19 is not rotated by transmission of engine rotation. This state is generally called a neutral state.

  The transmission mechanism 19 includes an input side variable pulley 35 provided on the input shaft 31, an output side variable pulley 37 provided on the output shaft 36, and a transmission belt 38 wound around both the variable pulleys 35, 37. It has. The transmission belt 38 transmits power through frictional forces between the variable pulleys 35 and 37. The input-side variable pulley 35 changes the distance from the center of rotation to the transmission belt 38 to continuously change the speed ratio (= input shaft rotational speed / output shaft rotational speed) of the speed change mechanism unit 19. 31 is displaced in the axial direction. The output side variable pulley 37 is displaced in the axial direction of the output shaft 36 so as to adjust the belt clamping pressure so that the transmission belt 38 does not slip with respect to both the variable pulleys 35 and 37.

  In addition, as shown in FIG. 2, the vehicle 10 has an electronic transmission control device (hereinafter referred to as a transmission) for controlling the hydraulic control circuit 26 based on various signals including detection signals from various sensors. ECU 41) is provided. The various signals include, for example, the shift lever operating position (shift position), the engine rotational speed NE, the rotational speed of the turbine shaft 23 that is the output shaft of the torque converter 12, the rotational speed of the input shaft 31 of the transmission mechanism 19, and the accelerator. Examples include the amount of pedal depression (accelerator opening), the amount of brake pedal depression, and the vehicle speed.

  The transmission ECU 41 is configured around a microcomputer, and a central processing unit (CPU) performs arithmetic processing according to a control program, initial data, a control map, etc. stored in a read-only memory (ROM). Various controls are executed based on the calculation result. The calculation result by the CPU is temporarily stored in a random access memory (RAM).

  Here, the hydraulic control circuit 26 to be controlled by the transmission ECU 41 will be described. The oil passage 42 of the hydraulic control circuit 26 supplies oil for engaging and releasing the forward clutch 33. The oil passage 42 supplies oil for adjusting the belt clamping pressure to the output side variable pulley 37. The oil passage 42 supplies oil to various parts other than the forward clutch 33 and the output side variable pulley 37. As the oil, oil discharged from the oil pump 25 is used.

  The hydraulic control circuit 26 includes a primary regulator valve 43 that adjusts the oil discharge pressure of the oil pump 25 to a line pressure PL that is a hydraulic pressure used for the hydraulic drive of the belt-type continuously variable transmission 14, and the line pressure PL. A pulley control valve 44 that acts on the output side variable pulley 37 and adjusts the belt clamping pressure adjusting hydraulic pressure (secondary pressure) PS is provided. The primary regulator valve 43 and the pulley control valve 44 are driven and controlled by a signal pressure (hydraulic pressure) output from a common linear solenoid valve SLS. Excess oil is drained in the primary regulator valve 43. The drive control of the linear solenoid valve SLS is performed by the transmission ECU 41. The transmission ECU 41 controls the hydraulic pressure (belt) acting on the output side variable pulley 37 so that the belt clamping pressure by the output side variable pulley 37 becomes a value at which no slip occurs between the transmission belt 38 and the variable pulleys 35, 37. The linear solenoid valve SLS is driven and controlled to adjust the clamping pressure adjusting hydraulic pressure. In the present embodiment, the first hydraulic pressure adjusting means is configured by the pulley control valve 44 and the linear solenoid valve SLS described above.

  The hydraulic control circuit 26 is provided with a clutch control valve 45 that adjusts the line pressure PL to a clutch adjustment hydraulic pressure (clutch pressure) PC that is a hydraulic pressure for driving the forward clutch 33. The clutch control valve 45 is driven and controlled by a signal pressure (hydraulic pressure) output from a linear solenoid valve SLT provided separately from the linear solenoid valve SLS. The drive control of the linear solenoid valve SLT is also performed by the transmission ECU 41. In this embodiment, the clutch control valve 45 and the linear solenoid valve SLT constitute second hydraulic pressure adjusting means.

  As one of the controls executed by the transmission ECU 41, there is a neutral control (N control) that is performed when the vehicle 10 is stopped and the operation position (shift position) of the shift lever is the travel position. The neutral control is performed for the purpose of improving fuel efficiency by reducing the load on the engine 11 by suppressing the forward clutch 33 in a half-released state, and suppressing fuel consumption when the vehicle is stopped. In this neutral control, the linear solenoid valve SLT is drive-controlled to adjust the pressure (clutch adjustment hydraulic pressure) related to the engaged state of the forward clutch 33 so that the speed ratio of the torque converter 12 becomes the target speed ratio TR. The speed ratio of the torque converter 12 is the speed ratio between the rotation input to the torque converter 12 and the rotation output from the torque converter 12, and is the ratio between the engine rotation speed NE and the rotation speed of the turbine shaft 23. .

  When the speed ratio of the torque converter 12 is set to a value near the target speed ratio TR, the forward clutch 33 is changed from the fully connected state to the half-released state. The half-released state is a state in which slip occurs between the upstream side (engine 11 side) and the downstream side (counter engine 11 side) in the forward clutch 33, and the driving force generated by the engine 11 is almost equal in the forward clutch 33. This is a connection state in which the return to the fully connected state that is completely transmitted can be performed with good response. In this half-released state, slight power transmission is performed in the forward clutch 33. That is, in the half-released state, the load on the engine 11 becomes smaller than in the fully connected state, and fuel efficiency can be improved.

Next, the content of the process for calculating the target speed ratio TR used for this neutral control will be described with reference to the target speed ratio calculation routine shown in the flowchart of FIG.
First, in step 110, the transmission ECU 41 determines whether or not neutral control is being executed. This determination is performed based on, for example, whether or not a neutral control execution condition is satisfied. As the execution condition of the neutral control, for example, the shift position is in the traveling position, the accelerator opening is zero, the brake is depressed, and the vehicle speed is equal to or less than a predetermined value (for example, zero). It is done. Note that the above four conditions are the minimum necessary, and other conditions may be included.

  If the determination condition of step 110 is satisfied, whether or not the neutral control is stable in step 120, that is, the actual speed ratio of the forward clutch 33 is the first target speed ratio set at the start of the neutral control. It is determined whether or not it is in the vicinity of TR (for example, a value corresponding to the idle rotation speed). Here, the engine rotation speed NE decreases as the vehicle 10 stops, and then converges to the idle rotation speed. Further, immediately after the vehicle 10 stops and before the neutral control is started, the turbine shaft 23 of the torque converter 12 stops rotating, and the rotational speed thereof is lower than the idle rotational speed of the engine 11. A big difference. Thereafter, when neutral control is started, the clutch adjustment hydraulic pressure PC is adjusted so that the speed ratio becomes the target speed ratio TR, whereby the forward clutch 33 is brought into a half-released state, and the turbine shaft of the torque converter 12 is set. The rotational speed of the engine 23 increases, approaches the idle rotational speed of the engine 11, and the difference between the rotational speeds becomes smaller. This state is a state in which neutral control is stable.

  If the determination condition of step 120 is satisfied, in step 130, a required belt torque capacity is obtained such that the belt clamping pressure adjusting hydraulic pressure PS becomes a minimum value that does not cause the transmission belt 38 to slip or a value corresponding thereto.

  Here, when the belt clamping pressure adjusting hydraulic pressure PS is lowered, the belt clamping pressure of the output side variable pulley 37 is lowered. When the belt clamping pressure adjustment hydraulic pressure PS becomes lower than a certain value, the transmission belt 38 starts to slide with respect to the output side variable pulley 37. In the output-side variable pulley 37, the belt clamping pressure adjusting hydraulic pressure PS that generates the minimum belt clamping pressure that does not cause the transmission belt 38 to slip is the minimum value that does not cause the transmission belt 38 to slip. The value corresponding to the minimum value is a value higher than the minimum value and close to the minimum value.

  As the minimum value of the belt clamping pressure adjusting hydraulic pressure PS, in a separately executed routine, a speed ratio that is an index indicating the speed change state of the belt type continuously variable transmission 14 and a standard value when the forward clutch 33 is neutrally controlled. In this state, a value calculated based on the input torque input from the engine 11 side to the input shaft 31 of the belt type continuously variable transmission 14 is used. In this calculation, for example, a map obtained by experimentally determining the relationship between the input torque, the transmission gear ratio, and the minimum value of the belt clamping pressure adjustment hydraulic pressure PS is referred to. From this map, the minimum value of the belt clamping pressure adjustment hydraulic pressure PS corresponding to the input torque and the gear ratio at that time is obtained.

  As the input torque, for example, the one calculated based on the engine output torque determined from the engine rotational speed NE and the engine load and the performance (original) of the torque converter 12 is used.

  Further, when the input torque of the speed change mechanism 19 is increased, the transmission belt 38 does not slip when the input torque is low. However, when the input torque exceeds a certain value, the transmission belt 38 starts to slide with respect to the output side variable pulley 37. The maximum value of the input torque that does not cause slippage in the transmission belt 38 is the required belt torque capacity.

  Accordingly, the minimum value at which the belt clamping pressure adjusting hydraulic pressure PS does not cause the transmission belt 38 to slip or a value corresponding thereto and the required belt torque capacity have a one-to-one correspondence with only a different expression. Therefore, the minimum value of the belt clamping pressure adjusting hydraulic pressure PS or a value corresponding thereto is converted into the required belt torque capacity by using a predetermined conversion formula.

  Next, in step 140, a target speed ratio TR of the torque converter 12 is calculated based on the rotational speed (engine rotational speed NE) input to the torque converter 12 and the required belt torque capacity.

  In calculating the target speed ratio TR, for example, a target speed ratio calculation map using the engine speed NE and the required belt torque capacity as calculation parameters is referred to. In this target speed ratio calculation map, a target speed ratio TR is set such that the torque input to the transmission mechanism unit 19 becomes the required belt torque capacity from the engine speed NE and the specifications of the torque converter 12. Yes. Then, from this target speed ratio calculation map, the target speed ratio TR corresponding to the engine rotational speed NE at that time and the necessary belt torque capacity obtained in step 130 is determined.

  Here, when the shift position is set to the neutral position, the forward clutch 33 is in a state in which almost no power transmission is performed (a state in which the power transmission amount is smaller than that in the half-released state). The ratio NR is close to the maximum value (ideally 1.0) that can be taken for control. However, the maximum value is slightly smaller than 1.0 in consideration of the influence of oil drag and the like. If the target speed ratio TR obtained in step 140 is an appropriate value, this maximum value should not be exceeded.

  Therefore, in consideration of this point, guard processing for the target speed ratio TR is performed. Specifically, in step 150, it is determined whether the target speed ratio TR obtained in step 140 is equal to or less than a value obtained by subtracting a predetermined value α from the speed ratio NR when the shift position is the neutral position. If this determination condition is satisfied, in step 160, a value obtained by subtracting the predetermined value α from the speed ratio NR is set as the final target speed ratio TR. The predetermined value α is an influence of dragging by oil on the speed ratio NR when the forward clutch 33 is in the above state, and is a constant value here. On the other hand, if the determination condition is not satisfied, in step 170, the target speed ratio TR in step 140 is set as the final target speed ratio TR. Therefore, a value larger than the value obtained by subtracting the predetermined value α from the speed ratio NR is not set as the final target speed ratio TR. The target speed ratio TR is the same as that obtained by subtracting the predetermined value α from the speed ratio NR even when the largest value is set.

  Then, after the processing of steps 160 and 170, the target speed ratio calculation routine is terminated. It should be noted that when the determination condition of step 110 described above is not satisfied (when the neutral control is not being executed) and when the determination condition of step 120 is not satisfied (the neutral control is being executed, the control is If it is not stable, the target speed ratio calculation routine is terminated without passing through the processing of steps 130-170.

  The target speed ratio TR thus obtained is used when driving and controlling the linear solenoid valve SLT for adjusting the hydraulic pressure (clutch adjustment hydraulic pressure PC) acting on the forward clutch 33 in the neutral control. The clutch adjustment hydraulic pressure PC is adjusted through control of the linear solenoid valve SLT so that the speed ratio of the torque converter 12 becomes the target speed ratio TR.

  Accordingly, the target speed ratio TR is set to a value such that the input torque of the transmission mechanism 19 does not exceed the required belt torque capacity, so that an excessively large input torque that causes the transmission belt 38 to slip is the same. There is no input to the transmission mechanism 19.

Further, the belt clamping pressure adjustment hydraulic pressure PS is adjusted to the above minimum value or a value corresponding thereto, so that the belt clamping pressure adjustment hydraulic pressure PS becomes lower than the case where the lower limit guard value set on the basis of the vehicle running is used.
In the present embodiment, the transmission ECU 41 and the following processing executed by the transmission ECU 41 correspond to the neutral control means. Corresponding processing by the transmission ECU 41 includes processing for calculating the target speed ratio TR in the target speed ratio calculation routine (steps 130 and 140) and linear solenoid so that the actual speed ratio becomes the calculated target speed ratio TR. This is a process for bringing the forward clutch 33 into a half-released state by adjusting the clutch adjustment hydraulic pressure PC through the control of the valve SLT.

According to the embodiment described in detail above, the following effects can be obtained.
(1) In the neutral control, a required belt torque capacity is obtained such that the belt clamping pressure adjusting hydraulic pressure PS becomes a minimum value or a value corresponding to the minimum value that does not cause the transmission belt 38 to slip (step 130). Based on this, the target speed ratio TR of the torque converter 12 is obtained (step 140).

  Therefore, by adjusting the belt clamping pressure adjustment hydraulic pressure PS to the minimum value or the equivalent value, the belt clamping pressure adjustment hydraulic pressure is higher than the case where the lower limit guard value set with reference to the traveling time of the vehicle 10 is also used in the neutral control. PS can be lowered. By reducing the belt clamping pressure adjustment hydraulic pressure PS, the extra work of the oil pump 25 can be reduced, and accordingly, the output of the engine 11 consumed for driving the oil pump 25 can be reduced to improve the fuel efficiency. it can.

  Further, by setting the target speed ratio TR to a value such that the input torque of the speed change mechanism unit 19 does not exceed the required belt torque capacity, the clutch adjustment hydraulic pressure PC is adjusted to be excessively high, and an excessively large input torque is shifted. It is possible to prevent the transmission belt 38 from slipping so as not to be applied to the mechanism portion 19.

Thus, according to the present embodiment, it is possible to improve fuel efficiency while suppressing slippage of the transmission belt 38.
(2) If a configuration is adopted in which signal pressure is supplied from a common linear solenoid valve to a pulley control valve 44 for adjusting the belt clamping pressure adjustment hydraulic pressure PS and a clutch control valve 45 for adjusting the clutch adjustment hydraulic pressure PC, The signal pressure is set with one of the control valves 44 and 45 as a reference. In this case, the signal pressure may not be optimal for the other of the control valves 44 and 45.

  In this regard, in the present embodiment, a linear solenoid valve that supplies a signal pressure to the pulley control valve 44 that adjusts the belt clamping pressure adjustment hydraulic pressure PS is a linear solenoid valve that supplies a signal pressure to the clutch control valve 45 that adjusts the clutch adjustment hydraulic pressure PC. A solenoid valve (linear solenoid valve SLS) different from the solenoid valve SLT is used. Therefore, by controlling these linear solenoid valves SLS and SLT separately, an appropriate signal pressure can be supplied to the control valves 44 and 45, and the belt clamping pressure adjusting hydraulic pressure PS as described in (1) above. In addition, the clutch adjustment hydraulic pressure PC can be adjusted to an appropriate value.

  (3) A guard process for the target speed ratio TR is performed (steps 150 to 170). Therefore, even if a target speed ratio TR larger than an appropriate value is calculated in step 140, the target speed ratio TR can be prevented from being used for neutral control.

Note that the present invention can be embodied in another embodiment described below.
When the target speed ratio calculation map used in step 140 of FIG. 3 is created, an upper limit value (= NR−α) that can be taken by the target speed ratio TR is set, and a value that exceeds the upper limit value as the target speed ratio TR The upper limit value may be set as the target speed ratio TR. In this way, the guard process in steps 150 to 170 can be omitted.

  The predetermined value α used in steps 150 to 170 in FIG. 3 may vary depending on individual differences, model differences, and the like of the torque converter 12. Therefore, the predetermined value α is stored and updated (learned) as needed. And you may make it use predetermined value (alpha) after learning for the process of steps 150-170. In this way, it is possible to reduce the influence of individual differences, model differences, etc., and obtain a more accurate value as the target speed ratio TR.

  In addition, a standard target speed ratio calculation map in which the maximum value of the target speed ratio TR is the speed ratio NR (= 1.0) is created in advance. Then, the predetermined value α is learned as described above, and for the target speed ratio TR on the target speed ratio calculation map, a value larger than the upper limit value (= NR−α), this upper limit value (= NR− You may make it rewrite to (alpha).

  The present invention can be applied to a vehicle including an electric motor as a power source instead of the engine 11.

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 11 ... Engine (power source), 12 ... Torque converter, 14 ... Belt type continuously variable transmission, 17 ... Drive wheel, 19 ... Transmission mechanism part, 25 ... Oil pump (pump), 33 ... Forward clutch ( Clutch), 37 ... output side variable pulley (variable pulley), 38 ... transmission belt, 41 ... transmission ECU (neutral control means), 44 ... pulley control valve (first hydraulic pressure adjusting means), 45 ... clutch control valve (first) 2 hydraulic adjustment means), PC ... clutch adjustment hydraulic pressure, PS ... belt clamping pressure adjustment hydraulic pressure (secondary pressure), SLS ... linear solenoid valve (first hydraulic adjustment means), SLT ... linear solenoid valve (second hydraulic pressure adjustment means), TR: Target speed ratio.

Claims (1)

As a transmission interposed between a torque converter for transmitting generated torque of a power source by a fluid and drive wheels of a vehicle,
A transmission belt is wound around, and a transmission mechanism having a variable pulley that is supplied from a pump and variable in belt clamping pressure by a belt clamping pressure adjusting hydraulic pressure adjusted by a first hydraulic pressure adjusting means, and supplied from the pump And a clutch that connects and disconnects between the torque converter and the transmission mechanism by the clutch adjustment hydraulic pressure adjusted by the second hydraulic pressure adjustment means, and the variable pulley slips on the transmission belt. Is applied to a belt-type continuously variable transmission in which the belt clamping pressure adjustment hydraulic pressure is adjusted through the control of the first hydraulic pressure adjusting means so as to clamp the transmission belt with a belt clamping pressure that does not cause
When the vehicle is stopped, the clutch adjustment hydraulic pressure is controlled through the control of the second hydraulic pressure adjustment means so that the speed ratio between the rotation input to the torque converter and the rotation output from the torque converter becomes a target speed ratio. A continuously variable transmission neutral control device comprising neutral control means for adjusting the clutch to a half-released state,
The neutral control means obtains a required belt torque capacity such that the belt clamping pressure adjustment hydraulic pressure becomes a minimum value that does not cause slippage of the transmission belt or a value corresponding thereto, and the target speed based on the required belt torque capacity is obtained. A neutral control device for a continuously variable transmission characterized by obtaining a ratio.

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