WO2020095742A1 - Control device for continuously variable transmission - Google Patents

Abstract

Provided is a control device for a belt continuously variable transmission (CVT) comprising a variator (4) and a CVT control unit (8). The CVT control unit (8) has: a hydraulic pressure feedback control unit (8a) which adjusts gear shift hydraulic pressure in the variator (4) by means of a hydraulic pressure feedback control comprising an integral term (I) obtained from the deviation between a target value and an actual value; and, a feedback minimum value setting unit (8b) which sets a first feedback minimum value (Plow 1 (F/B)) limiting a reduction in post-feedback command pressure (Psec (F/B)). The feedback minimum value setting unit (8b) sets the first feedback minimum value (Plow 1 (F/B)) to a value which was obtained by adding hydraulic pressure (A) required for torque capacity to securely hold a belt (44), and a margin which accounts for secondary pressure (Psec (Real)) undershoot during recovery from an adjustment defect.

Description

Controller for continuously variable transmission

The present invention relates to a control device for a continuously variable transmission mounted on a vehicle.

Conventionally, there has been disclosed a control device for a continuously variable transmission in which an operating state is set by a hydraulic pressure regulated by feedback control including an integral operation based on a deviation between a target value and an actual value (for example, Patent Document 1). 1). The conventional device is configured to increase the value of the integral term in the integral operation while the pressure regulation failure detection unit that detects a fault in the hydraulic pressure regulation and the faulty pressure regulation is detected by the pressure regulation failure detection unit. And limiting means for limiting.

In the above conventional device, since the integral term in the so-called abnormal state does not increase, the integral term in the so-called steady state returned from the pressure regulation failure does not become excessive, and as a result, the poor regulation of the hydraulic pressure is recovered. It is possible to improve the response of the hydraulic pressure afterwards. However, there is a problem that the lower limit of the operation amount by the hydraulic pressure feedback control of the secondary pressure may fall below the belt capacity when recovering from poor pressure regulation, and belt slippage may occur due to insufficient belt capacity.

The present invention has been made in view of the above problems, and it is an object of the present invention to prevent belt slippage by avoiding capacity shortage due to hydraulic pressure feedback control of secondary pressure when recovering from poor regulation.

JP, 2005-351334, A

To achieve the above object, a control device for a continuously variable transmission according to the present invention includes a continuously variable transmission mechanism and a transmission controller.
The transmission controller has a hydraulic pressure feedback control unit that regulates the shift hydraulic pressure of the continuously variable transmission mechanism by hydraulic pressure feedback control including an integral term based on a deviation between a target value and an actual value. Further, the transmission controller has a feedback lower limit value setting unit that sets a feedback lower limit value that limits a decrease in the secondary instruction pressure due to the hydraulic pressure feedback control.
The feedback lower limit value setting unit is a value obtained by adding the feedback lower limit value to the required hydraulic pressure for the torque capacity to secure the belt clamping and the margin considering the undershoot of the secondary actual pressure at the time of recovery from poor regulation. Set to.

Therefore, at the time of recovery from poor pressure regulation, it is possible to prevent the occurrence of belt slip by avoiding the capacity shortage due to the hydraulic pressure feedback control of the secondary pressure.

FIG. 1 is an overall system diagram showing a drive system and a control system of an engine vehicle to which a hydraulic control device for a belt type continuously variable transmission according to a first embodiment is applied. FIG. 9 is a shift schedule diagram showing an example of a D range continuously variable shift schedule used when the continuously variable shift control in the automatic shift mode is executed by the variator. FIG. 1 is a schematic configuration diagram showing a hydraulic control system for a belt type continuously variable transmission according to a first embodiment. 6 is a flowchart showing a flow of feedback lower limit value setting and hydraulic pressure feedback control processing executed by a CVT control unit. It is a characteristic view which shows each characteristic of the secondary instruction | indication pressure, secondary actual pressure, and post-F / B instruction | indication pressure at the time of returning after a secondary pressure solenoid valve becomes a pressure regulation failure. FIG. 6 is an explanatory diagram showing how to determine a first feedback lower limit value and a second feedback lower limit value in the first embodiment. 7 is a time chart showing respective characteristics of a secondary indicated pressure, a secondary actual pressure, and a post-F / B indicated pressure when belt slippage occurs when returning from poor pressure regulation in a comparative example. 5 is a time chart showing respective characteristics of a secondary designated pressure, a secondary actual pressure, and a post-F / B designated pressure when belt slippage is suppressed when recovering from poor pressure regulation in the first embodiment.

Hereinafter, a mode for carrying out a control device for a continuously variable transmission according to the present invention will be described based on Embodiment 1 shown in the drawings.

The control device in the first embodiment is applied to an engine vehicle with an idle stop function equipped with a belt type continuously variable transmission including a torque converter, a forward / reverse switching mechanism, a variator, and a final reduction mechanism. Hereinafter, the configuration of the first embodiment will be described with reference to an "overall system configuration", a "detailed configuration of a hydraulic control system for a belt type continuously variable transmission", a "feedback lower limit value setting and a hydraulic feedback control processing configuration", and a "feedback lower limit value setting". The configuration will be described separately.

[Overall system configuration]
FIG. 1 shows a drive system and a control system of an engine vehicle to which a shift control device for a continuously variable transmission according to a first embodiment is applied. The overall system configuration will be described below with reference to FIG.

As shown in FIG. 1, a drive system of an engine vehicle includes an engine 1, a torque converter 2, a forward / reverse switching mechanism 3, a variator 4, a final reduction mechanism 5, and drive wheels 6 and 6. There is. Here, the belt type continuously variable transmission CVT is configured by incorporating a torque converter 2, a forward / reverse switching mechanism 3, a variator 4, and a final reduction mechanism 5 in a transmission case (not shown).

The engine 1 can control the output torque by an engine control signal from the outside, in addition to the control of the output torque by the accelerator operation by the driver. The engine 1 has an output torque control actuator 10 that controls torque by opening / closing a throttle valve, retarding an ignition timing, and cutting a fuel. For example, the fuel cut control is executed during coast running by the accelerator foot release operation. Further, when the vehicle is stopped and a predetermined condition is satisfied, idle stop control for stopping the engine 1 is executed.

The torque converter 2 is a starting element with a fluid coupling having a torque amplification function and a torque fluctuation absorption function. When the torque amplification function and the torque fluctuation absorption function are not required, the engine output shaft 11 (= torque converter input shaft) and the torque converter output shaft 21 have a lockup clutch 20 that can be directly connected. The torque converter 2 includes a pump impeller 23, a turbine runner 24, and a stator 26 as constituent elements. The pump impeller 23 is connected to the engine output shaft 11 via the converter housing 22. The turbine runner 24 is connected to the torque converter output shaft 21. The stator 26 is provided in the transmission case via the one-way clutch 25.

The forward / reverse switching mechanism 3 is a mechanism that switches the input rotation direction to the variator 4 between the forward rotation direction when traveling forward and the reverse rotation direction when traveling backward. This forward / reverse switching mechanism 3 has a double pinion type planetary gear 30, a forward clutch 31 formed of a plurality of clutch plates, and a reverse brake 32 formed of a plurality of brake plates. The forward clutch 31 is hydraulically engaged by the forward clutch pressure Pfc when the forward traveling range such as the D range is selected. The reverse brake 32 is hydraulically engaged by the reverse brake pressure Prb when the reverse traveling range such as the R range is selected. The forward clutch 31 and the reverse brake 32 are both released by draining the forward clutch pressure Pfc and the reverse brake pressure Prb when the N range (neutral range) is selected.

The variator 4 includes a primary pulley 42, a secondary pulley 43, and a belt 44, and a continuously variable transmission that continuously changes a gear ratio (ratio between variator input rotation and variator output rotation) by a change in belt contact diameter. Equipped with mechanical capabilities. The primary pulley 42 is composed of a fixed pulley 42 a and a slide pulley 42 b that are arranged coaxially with the variator input shaft 40, and the slide pulley 42 b slides by the primary pressure Ppri guided to the primary pressure chamber 45. The secondary pulley 43 is composed of a fixed pulley 43a and a slide pulley 43b arranged coaxially with the variator output shaft 41, and the slide pulley 43b slides by the secondary pressure Psec introduced into the secondary pressure chamber 46. The belt 44 is stretched around the V-shaped sheave surface of the primary pulley 42 and the V-shaped sheave surface of the secondary pulley 43. This belt 44 is formed by two sets of laminated rings in which a plurality of annular rings are superposed from the inside to the outside and a punched plate material, and is attached by being laminated along the two sets of laminated rings in an annular shape by sandwiching them. It is composed by. The belt 44 may be a chain type belt in which a large number of chain elements arranged in the pulley traveling direction are connected by a pin penetrating in the pulley axial direction.

The final deceleration mechanism 5 is a mechanism that decelerates the variator output rotation from the variator output shaft 41 and imparts a differential function to the left and right drive wheels 6 and 6. The final reduction gear mechanism 5 is, as a reduction gear mechanism, an output gear 52 provided on the variator output shaft 41, an idler gear 53 and a reduction gear 54 provided on the idler shaft 50, and a final gear provided on an outer peripheral position of the differential case. And a gear 55. Further, as a differential gear mechanism, it has a differential gear 56 interposed between the left and right drive shafts 51, 51.

As shown in FIG. 1, the control system of the engine vehicle includes a hydraulic control unit 7, a CVT control unit 8 (abbreviation “CVTCU”), and an engine control unit 9 (abbreviation “ECU”). The CVT control unit 8 and the engine control unit 9, which are electronic control systems, are connected by a CAN communication line 13 capable of exchanging information with each other.

The hydraulic control unit 7 controls the primary pressure Ppri guided to the primary pressure chamber 45, the secondary pressure Psec guided to the secondary pressure chamber 46, the forward clutch pressure Pfc to the forward clutch 31, the reverse brake pressure Prb to the reverse brake 32, and the like. It is a unit that regulates pressure. The hydraulic control unit 7 includes an oil pump source 70, and a hydraulic control circuit 71 that regulates various control pressures based on the discharge pressure from the oil pump source 70.

The oil pump source 70 includes a mechanical oil pump 70a driven by the engine 1, an electric oil pump 70c driven by an electric motor 70b, and one-way valves 70d, 70e provided in a pump discharge oil passage. Have. The hydraulic control circuit 71 includes a line pressure solenoid valve 72, a primary pressure solenoid valve 73, a secondary pressure solenoid valve 74, a select solenoid valve 75, and a lockup pressure solenoid valve 76. The solenoid valves 72, 73, 74, 75, 76 perform pressure adjustment operation according to a control command value (instruction current) output from the CVT control unit 8.

The line pressure solenoid valve 72 regulates the discharge pressure from the oil pump source 70 to the commanded line pressure PL according to the line pressure command value output from the CVT control unit 8. The line pressure PL is an original pressure when adjusting various control pressures, and is a hydraulic pressure that suppresses belt slip and clutch slip with respect to the torque transmitted through the drive system.

The primary pressure solenoid valve 73 adjusts the primary pressure command value output from the CVT control unit 8 to the commanded primary pressure Ppri using the line pressure PL as the source pressure. The secondary pressure solenoid valve 74 reduces and adjusts the secondary pressure command value output from the CVT control unit 8 to the commanded secondary pressure Psec using the line pressure PL as the source pressure.

The select solenoid valve 75 adjusts the pressure to the forward clutch pressure Pfc or the backward brake pressure Prb commanded with the line pressure PL as the original pressure in accordance with the forward clutch pressure command value or the backward brake pressure command value output from the CVT control unit 8. To do.

The lockup pressure solenoid valve 76 regulates the LU command pressure Plu that engages / disengages / releases the lockup clutch 20 according to the command current Alu output from the CVT control unit 8.

The CVT control unit 8 performs line pressure control, shift control, forward / reverse switching control, lockup control, and the like. In the line pressure control, a command value for obtaining a target line pressure according to the accelerator opening etc. is output to the line pressure solenoid valve 72. In the speed change control, when the target speed ratio (target primary speed Npri ^* ) is determined, a command value for obtaining the determined target speed ratio (target primary speed Npri ^* ) is output to the primary pressure solenoid valve 73 and the secondary pressure solenoid valve 74. .. In the forward / reverse switching control, a command value for controlling engagement / disengagement of the forward clutch 31 and the reverse brake 32 is output to the select solenoid valve 75 according to the selected range position. In the lockup control, a command current Alu for controlling the LU command pressure Plu for engaging / slip-engaging / releasing the lockup clutch 20 is output to the lockup pressure solenoid valve 76.

The sensor information and the switch information from the primary rotation sensor 90, the vehicle speed sensor 91, the secondary pressure sensor 92, the oil temperature sensor 93, the inhibitor switch 94, the brake switch 95, and the turbine rotation sensor 96 are input to the CVT control unit 8. Further, sensor information from the secondary rotation sensor 97, the primary pressure sensor 98, the wheel speed sensor 99, etc. is input.

The sensor information from the engine rotation sensor 12, the accelerator opening sensor 14, etc. is input to the engine control unit 9. When the CVT control unit 8 requests the engine rotation information and the accelerator opening information to the engine control unit 9, the CVT control unit 8 receives the information on the engine speed Ne and the accelerator opening APO via the CAN communication line 13. Further, when requesting the engine torque information to the engine control unit 9, the information of the actual engine torque Te estimated and calculated in the engine control unit 9 is received via the CAN communication line 13.

FIG. 2 shows an example of a D range continuously variable shift schedule used when the variator 4 executes the continuously variable shift control in the automatic shift mode when the D range is selected.

The "D range shift mode" is an automatic shift mode in which the gear ratio is automatically changed steplessly according to the vehicle operating state. The shift control in the "D range shift mode" is performed at the operating point (on the D range continuously variable shift schedule of Fig. 2 specified by the vehicle speed VSP (vehicle speed sensor 91) and the accelerator opening APO (accelerator opening sensor 14). VSP, APO) determines the target primary speed Npri ^* . Then, the actual primary rotation speed Npri from the primary rotation sensor 90 is set to a pulley hydraulic pressure target value that matches the target primary rotation speed Npri ^*, and hydraulic feedback control is performed to match the actual pulley hydraulic pressure value to the pulley hydraulic pressure target value. The speed ratio is represented by the slope of the speed ratio line drawn from the zero operating point, as is clear from the lowest speed ratio line and the highest speed ratio line of the D range continuously variable speed change schedule. Therefore, determining the target primary rotation speed Npri ^{* according} to the operating point (VSP, APO) determines the target gear ratio of the variator 4.

That is, the D-range continuously variable shift schedule used in the "D-range shift mode" is, as shown in FIG. 2, a gear ratio range of the lowest Low gear ratio and the highest High gear ratio depending on the operating point (VSP, APO). It is set to continuously change the gear ratio within the range. For example, when the vehicle speed VSP is constant, when the accelerator is depressed, the target primary speed Npri ^* increases and shifts in the downshift direction. When the accelerator is released, the target primary speed Npri ^* decreases and the target primary speed Npri ^* increases. Shift in the shift direction. When the accelerator opening APO is constant, the vehicle shifts in the upshift direction when the vehicle speed VSP increases, and shifts in the downshift direction when the vehicle speed VSP decreases.

[Detailed configuration of hydraulic control system for belt type continuously variable transmission]
FIG. 3 shows a hydraulic control system of the belt type continuously variable transmission CVT. Hereinafter, the detailed configuration of the hydraulic control system of the belt type continuously variable transmission CVT will be described with reference to FIG. Note that “feedback” is abbreviated as “F / B”.

As shown in FIG. 3, the drive system to which the hydraulic control system is applied includes an engine 1 (driving drive source), a torque converter 2, a forward / reverse switching mechanism 3, a variator 4, a final reduction gear mechanism 5, and And a drive wheel 6. The engine 1 drives a mechanical oil pump 70a. The torque converter 2 has a lockup clutch 20. The forward / reverse switching mechanism 3 has a forward clutch 31 and a reverse brake 32. The variator 4 has a primary pulley 42, a secondary pulley 43, and a belt 44.

As shown in FIG. 3, the hydraulic control system to which the hydraulic control system is applied includes an oil pump source 70, a hydraulic control circuit 71, a line pressure solenoid valve 72, a primary pressure solenoid valve 73, and a secondary pressure solenoid valve 74. And are equipped with.

The electronic control system to which the hydraulic control system is applied includes a CVT control unit 8, an engine control unit 9, and a CAN communication line 13, as shown in FIG. Information from the vehicle speed sensor 91, the inhibitor switch 94, the turbine rotation sensor 96, the wheel speed sensor 99, etc. is input to the CVT control unit 8. Information from the engine rotation sensor 12, the accelerator opening sensor 14, etc. is input to the engine control unit 9. Here, the engine control unit 9 has an idle stop control section 9a that performs idle stop control for stopping the operation of the engine 1 when a predetermined condition is satisfied when the vehicle is stopped. It should be noted that when the operation of the engine 1 is stopped by the idle stop control, the amount of oil discharged from the mechanical oil pump 70a is lost, so the electric oil pump 70c is driven to secure the amount of oil discharged.

The CVT control unit 8 includes a hydraulic pressure feedback control unit 8a, a feedback lower limit value setting unit 8b, an idle stop control during determination unit 8c, and a feedback OFF determination unit 8d.

The hydraulic pressure feedback control unit 8a regulates the shift hydraulic pressure (primary pressure Ppri, secondary pressure Psec) of the variator 4 (stepless speed change mechanism) by hydraulic pressure feedback control including an integral term I depending on the deviation between the target value and the actual value. Ordinary hydraulic pressure feedback control is so-called PID control using a proportional term P, an integral term I, and a differential term D with respect to the deviation.

The feedback lower limit value setting unit 8b sets a first feedback lower limit value Plow1 (F / B) that limits a decrease in the secondary indicated pressure Psec (F / B) that is the secondary indicated pressure due to the hydraulic pressure feedback control. Here, the first feedback lower limit value Low1 (F / B) is set to a value obtained by adding the required oil pressure A for the torque capacity, the correction amount B for the undershoot, and the correction amount C for the steady deviation. .. The required oil pressure A corresponding to the torque capacity refers to the required oil pressure corresponding to the torque capacity according to the safety factor 1 for securing the holding of the belt 44. The correction amount B for the undershoot is a correction amount for the undershoot when the secondary actual pressure Psec (Real) decreases at the time of recovery from poor pressure regulation. The correction amount C for the steady deviation refers to the correction amount for the steady deviation between the secondary actual pressure Psec (Real) and the post-F / B instruction pressure Psec (F / B).

The idle-stop-control-in-progress determination unit 8c determines whether or not the idle stop control is in progress. The feedback lower limit value setting unit 8b does not need to set the first feedback lower limit value Low1 (F / B) when the idle stop control determination unit 8c determines that the idle stop control is being performed. When the idle stop control determination unit 8c determines that the idle stop control is being performed, the hydraulic feedback control unit 8a holds the integral term I of the feedback operation amount (PID operation amount) at the previous value before the start of the idle stop control. Leave it alone.

The feedback-off determination unit 8d determines whether to turn off the hydraulic feedback control. The feedback lower limit value setting unit 8b does not need to set the first feedback lower limit value Low1 (F / B) when it is determined by the feedback OFF determination unit 8d to turn off the hydraulic pressure feedback control. The hydraulic pressure feedback control unit 8a sets the feedback operation amount (PID operation amount) to zero when the feedback OFF determination unit 8d determines to turn off the hydraulic pressure feedback control.

When the setting of the first feedback lower limit value Low1 (F / B) is unnecessary, the feedback lower limit value setting unit 8b subtracts the fixed value due to the steady deviation variation from the secondary indicated pressure Psec (ins). Set to the value Low2 (F / B).

[Feedback lower limit value setting and hydraulic feedback control processing configuration]
FIG. 4 shows a flow of feedback lower limit value setting and hydraulic pressure feedback control processing executed by the CVT control unit 8 of the first embodiment. Hereinafter, each step of FIG. 4 will be described. The "idle stop" is abbreviated as "IS".

In step S1, following the start, it is determined whether or not the secondary pressure F / B control is in a prohibited region. If YES (secondary pressure F / B control prohibited area), the process proceeds to step S2. If NO (secondary pressure F / B control permitted area), the process proceeds to step S4.
Step S1 corresponds to the feedback off determination unit 8d that determines whether to turn off (prohibit) the hydraulic pressure feedback control. For example, when the hydraulic control function failure, extremely low temperature, or extremely low rotation speed of the oil pump, it is determined that the secondary pressure F / B control is prohibited.

In step S2, following the determination of YES in S1, the second feedback lower limit value Low2 (F / B) is calculated, and the process proceeds to step S3.
Here, the “second feedback lower limit value Low2 (F / B)” is calculated by subtracting a fixed value due to the steady deviation variation from the secondary command pressure Psec (ins).

In step S3, following S2, at least the secondary pressure Psec hydraulic feedback control of the pulley hydraulic pressure adjustment control is turned off, and the process proceeds to return.

▽ In step S4, following the judgment of NO in S1, it is judged whether or not idling stop control is in progress. If YES (the idling stop control is being performed), the process proceeds to step S5, and if NO (the idling stop control is not being performed), the process proceeds to step S7. Step S4 corresponds to the idle stop control in-progress determination unit 8c that determines whether or not the idle stop control is in progress. Whether or not the idle stop control is being performed is determined by whether or not the idle stop control flag obtained from the idle stop control section 9a of the engine control unit 9 via the CAN communication line 13 is set.

In step S5, following the determination of YES in S4, the second feedback lower limit value Low2 (F / B) is calculated, and the process proceeds to step S6. The specific calculation method of the second feedback lower limit value Low2 (F / B) in S5 is the same as in S2.

In step S6, following S5, control is performed to hold the integral term I of the secondary pressure F / B control at the previous value before the start of idle stop control, and the process returns.

In step S7, the required oil pressure A is calculated from the input torque and the winding diameter (= the gear ratio of the variator 4) following the determination of NO in step S4, and the process proceeds to step S8.
Here, the "necessary hydraulic pressure A" refers to the secondary pressure Psec required to obtain a torque capacity equivalent to a safety factor of 1 for securing the belt 44 (a state in which the transmission torque and the torque capacity are equal).

In step S8, the correction amount B for the undershoot is calculated from the oil temperature table, following step S7, and the process proceeds to step S9.
Here, the “correction amount B for undershoot” means the undershoot amount when the secondary actual pressure Psec (Real) decreases at the time of recovery from poor regulation.

In step S9, following step S8, the correction amount C for the steady deviation is calculated from the oil temperature and the oil temperature zone map, and the process proceeds to step S10.
Here, the “steady deviation correction amount C” refers to a correction amount for a steady deviation between the secondary actual pressure Psec (Real) and the post-F / B instruction pressure Psec (F / B).

In step S10, following S9, the first feedback lower limit value Low1 (F / B) is calculated, and the process proceeds to step S11.
Here, the first feedback lower limit value Low1 (F / B) is
Required oil pressure A + (correction amount B for undershoot) + (correction amount C for steady-state deviation)
It is calculated by the formula.

In step S11, following S10, normal secondary pressure F / B control by PID control is executed, and the process proceeds to return.
When the secondary pressure F / B control in step S11 is executed, the decrease in the post-F / B command pressure Psec (F / B) is limited by the first feedback lower limit value Plow1 (F / B) calculated in S10. To be done. In other words, the post-F / B instruction pressure Psec (F / B) does not become a value lower than the first feedback lower limit value Plow1 (F / B) even during pressure regulation failure.

[Feedback lower limit setting configuration]
FIG. 5 shows the secondary instruction pressure Psec (ins), the secondary actual pressure Psec (Real), and the F / B post-instruction pressure Psec (F / B) when the secondary pressure solenoid valve 74 returns after the pressure adjustment failure. Each characteristic is shown. FIG. 6 shows how to determine the first feedback lower limit Plow1 (F / B) and the second feedback lower limit Plow2 (F / B). The setting configuration of the feedback lower limit value will be described below with reference to FIGS. 5 and 6.

First, as shown in FIG. 6, the first feedback lower limit value Low1 (F / B) is based on the required hydraulic pressure A based on the torque capacity (safety factor 1), and the required hydraulic pressure A is corrected by the correction amount B for the undershoot. Is calculated by adding the correction amount C for the steady deviation.

The "required hydraulic pressure A" is calculated based on the input torque and the winding diameter (= the gear ratio of the variator 4), and is the secondary pressure Psec required for the torque capacity corresponding to the safety factor of 1 for securing the belt 44. Is defined.

Here, the “input torque” is the input torque to the variator 4, and is the engine torque Te when the lockup clutch 20 and the forward clutch 31 are engaged. When the lockup clutch 20 is in the released state or the slip engaged state, the input torque is calculated using the torque ratio obtained from the speed ratio of the torque converter 2 and the engine torque Te.

Then, the belt holding torque capacity corresponding to the input torque to the variator 4 and the gear ratio becomes the torque capacity based on the safety factor 1 for securing the holding of the belt 44. Therefore, a value obtained by converting the minimum torque capacity required to hold the belt 44 without slipping into the secondary pressure Psec is the "required hydraulic pressure A".

The “undershoot correction amount B” is calculated based on the oil temperature table, and is the undershoot amount when the secondary actual pressure Psec (Real) decreases at the time of recovery from poor regulation, as shown in FIG. Is defined.

Here, the "oil temperature table" acquires the undershoot amount at the time of a hydraulic pressure gradient in which the secondary actual pressure Psec (Real) decreases when returning from poor pressure regulation when the oil temperature is changed by a number of experiments, Create based on the acquired undershoot amount data.

Note that the relationship between the oil temperature of the transmission hydraulic oil and the undershoot amount is that the higher the oil temperature and the lower the oil viscosity, the higher the hydraulic response and the larger the undershoot amount. Therefore, the "correction amount B for undershoot" is given as a larger value as the oil temperature is higher. In addition, the higher the secondary actual pressure Psec (Real) at the time of recovery from poor regulation, the larger the value will be.

The “correction amount C for steady-state deviation” is calculated based on the oil temperature and the hydraulic pressure zone map, and as shown in FIG. 5, the secondary actual pressure Psec (Real) and F after the transition from the return transient state to the steady state is performed. / B Defined by steady-state deviation of indicated pressure Psec (F / B) after B.

Here, the "oil temperature and hydraulic zone map" divides the secondary pressure Psec into multiple hydraulic zones from the low pressure zone to the high pressure zone. Then, when the oil temperature is changed for each hydraulic pressure band, steady deviations of the secondary actual pressure Psec (Real) and the post-F / B indicated pressure Psec (F / B) are acquired by many experiments, and the steady deviations obtained are acquired. Create based on the data of.

Note that the relationship between the oil temperature of the transmission hydraulic oil and the steady-state deviation is that the higher the oil temperature, the higher the match between the secondary actual pressure Psec (Real) and the post-F / B indicated pressure Psec (F / B) and the steady-state deviation. Get smaller. Regarding the relationship between the hydraulic pressure band and the steady deviation, the higher the hydraulic pressure band, the larger the steady deviation. Therefore, the “correction amount C for steady-state deviation” is given as a smaller value as the oil temperature is higher, and as a larger value as the oil pressure is higher.

As described above, the first feedback lower limit value Low1 (F / B) given by (required oil pressure A + correction amount B + correction amount C) is, as shown in FIG. It has the meaning of B lower limit.

Next, as shown in FIG. 6, the “second feedback lower limit value Low2 (F / B)” is calculated by subtracting the fixed value due to the steady deviation variation from the secondary indicated pressure Psec (ins).

Here, for the "fixed value", the steady-state deviation between the secondary indicated pressure Psec (ins) and the secondary actual pressure Psec (Real) when the oil temperature and hydraulic pressure conditions are varied is acquired by numerous experiments. Then, the value of the maximum value of the steady deviation variation is determined based on the acquired steady deviation data. That is, the “fixed value” is a value that prevents the secondary instruction pressure Psec (ins) <secondary actual pressure Psec (Real) from being satisfied when the steady deviation is in the maximum range.

Thus, the "second feedback lower limit value Low2 (F / B)" given by (secondary indicated pressure Psec (ins) -fixed value) is the F / B lower limit that guarantees the hydraulic pressure variation, as shown in FIG. It has the meaning of value.

Next, the operation of the first embodiment will be described by dividing it into "background technology and problems", "problem solving means and problem solving operation", and "secondary pressure F / B control operation".

[Background Technology and Issues]
In controlling the pulley hydraulic pressure in the belt type continuously variable transmission, hydraulic F / B control is built on the assumption that the pressure regulation in the hydraulic control circuit is normal. Therefore, the F / B operation amount is stored insignificantly when a pressure regulation failure occurs in the hydraulic control circuit.

Then, in order to satisfy the necessary function that is determined by the fuel consumption requirement that does not worsen friction, the upper and lower limits of the F / B operation amount are set in consideration of the variation in hydraulic pressure. For this reason, the lower limit of the F / B operation amount may fall below the belt capacity, which promotes that the secondary actual pressure becomes equal to or less than the belt capacity when the secondary pressure solenoid valve recovers from poor pressure regulation.

That is, in the secondary pressure F / B control in the belt type continuously variable transmission of the comparative example, the lower limit value for limiting the decrease of the post-F / B instruction pressure is uniformly set to the second feedback lower limit value (secondary instruction pressure-fixed value). ) Is given at the lower limit. In this case, as shown in the time chart of FIG. 7, defective pressure regulation occurs at time t1, and the secondary actual pressure increases toward time t2. When the secondary actual pressure rises, the deviation between the secondary instruction pressure and the secondary actual pressure increases, so the post-F / B instruction pressure in the secondary pressure F / B control decreases so as to eliminate the increasing deviation. When the post-F / B instruction pressure reaches the lower limit value at time t3, the post-F / B instruction pressure maintains the lower limit value after time t3.

At time t4, when recovering from poor pressure regulation, the rising secondary actual pressure suddenly drops toward the post-F / B indicated pressure.At time t5, the secondary actual pressure becomes greater than the post-F / B indicated pressure. Undershoot occurs, which is low. When the undershoot of the secondary actual pressure occurs, the secondary actual pressure falls below the belt capacity and belt slippage occurs.

On the other hand, as a measure to realize the necessary function determined by the component protection requirement of suppressing belt slippage, the fixed value should be set to a small value so that the lower limit value (= secondary indicated pressure-fixed value) of the comparative example becomes a large value. There is candidate 1 to do. However, in the case of the measure candidate 1, since there is a unit whose friction increases in the entire area, it is not possible to meet the fuel consumption requirement.

There is also Candidate 2 that prepares two lower limit values of different sizes, detects pressure regulation defects, and selects a higher lower limit value only when necessary. However, in the case of the countermeasure candidate 2, it is difficult to detect that the pressure regulation is poor and the recovery from the poor pressure regulation, and the difficulty in mounting the vehicle on the vehicle becomes high.

In this way, it is possible to suppress the occurrence of belt slippage when recovering from poor pressure regulation, while satisfying both fuel consumption requirements and component protection requirements, without increasing the difficulty when mounting on a vehicle. Is an issue.

[Problem solving means and problem solving action]
In view of the above problems, the present invention sets the feedback lower limit value that limits the reduction of the secondary instruction pressure to a value that satisfies both the fuel consumption requirement and the component protection requirement regardless of whether there is a pressure regulation failure. As a means for solving the problem, the CVT control unit 8 includes a feedback lower limit value setting unit 8b that sets a first feedback lower limit value Low1 (F / B) that limits a decrease in the post-F / B indicating pressure Psec (F / B). Have. The feedback lower limit value setting unit 8b sets the first feedback lower limit value Low1 (F / B) to the required hydraulic pressure A for the torque capacity according to the safety factor 1 for securing the belt 44, and the secondary pressure at the time of recovery from poor regulation. The means to set the value which added the margin considering the undershoot of the actual pressure Psec (Real) and was adopted.

That is, in the secondary pressure F / B control in the belt type continuously variable transmission CVT of the first embodiment, the first feedback lower limit value Low1 (F / B) that limits the decrease of the post-F / B instruction pressure Psec (F / B). Is given by a value obtained by adding the required oil pressure A and the margin, as shown in FIG. In this case, as shown in the time chart of FIG. 8, poor pressure regulation occurs at time t1, and the secondary actual pressure Psec (Real) increases toward time t2. When the secondary actual pressure Psec (Real) increases, the deviation between the secondary indicated pressure Psec (inc) and the secondary actual pressure Psec (Real) increases, so the F / B post indicated pressure Psec (F / B) decreases so as to eliminate the expanding deviation. When the F / B post-instruction pressure Psec (F / B) reaches the first feedback lower limit value Low1 (F / B) at time t3, after the time t3, the F / B post-instruction pressure Psec (F / B). ) Maintains the first feedback lower limit value Low1 (F / B).

After recovering from poor pressure regulation at time t4, the rising secondary actual pressure Psec (Real) suddenly drops toward the post-F / B indicated pressure Psec (F / B), so that the secondary pressure at time t5 Undershoot occurs when the actual pressure Psec (Real) becomes lower than the post-F / B indicated pressure Psec (F / B). However, even if the secondary actual pressure Psec (Real) undershoots, the F / B post-instruction pressure Psec (F / B) maintains the first feedback lower limit value Low1 (F / B). Absorbed in minutes. In other words, the secondary actual pressure Psec (Real) does not fall below the belt capacity (required hydraulic pressure A), and a capacity that does not cause belt slipping at time t5 is secured.

As a result, when the secondary pressure solenoid valve 74 recovers from the poor pressure regulation, it is possible to prevent the occurrence of belt slippage by avoiding the capacity shortage due to the secondary pressure F / B control. In addition, the first feedback lower limit value Low1 (F / B) is set to a value that satisfies both the fuel consumption requirement and the component protection requirement by the margin considering the required hydraulic pressure A and the undershoot. Therefore, it is possible to meet not only the component protection request but also the fuel consumption request. Further, since it is not necessary to detect the pressure regulation failure of the secondary pressure solenoid valve 74, it is possible to suppress the occurrence of belt slip at the time of recovery from the pressure regulation failure without increasing the difficulty in mounting the secondary pressure solenoid valve 74 on the vehicle. ..

[Secondary pressure F / B control action]
First, the secondary pressure control operation by the hydraulic pressure feedback control will be described based on the flowchart of FIG.

For example, when the oil temperature of the transmission hydraulic oil is extremely low, etc., and it is determined that the secondary pressure F / B control is prohibited, the flow proceeds to S1 → S2 → S3 in the flowchart of FIG. Is repeated. At S2, the second feedback lower limit value Low2 (F / B) is calculated by subtracting the fixed value due to the steady deviation variation from the secondary instruction pressure Psec (ins). In S3, a control for turning off the hydraulic pressure F / B control of at least the secondary pressure Psec in the pressure regulation control of the pulley hydraulic pressure is executed.

As described above, in the case where the secondary pressure F / B control is prohibited, the first feedback lower limit value Low1 is set because the post-F / B indicated pressure Psec (F / B) does not decrease even if there is a pressure regulation failure. No need to set (F / B). Further, in the pressure regulation control of the secondary pressure Psec, since the secondary pressure Psec rises slowly due to low temperature, etc., the secondary pressure F / F control (F / F control) that continues to output the instruction to match the actual value with the target value (= Feedforward control) will be executed.

On the other hand, when it is determined that the idling stop control is being performed, the flow of proceeding from S1 → S4 → S5 → S6 is repeated in the flowchart of FIG. In S5, the second feedback lower limit value Low2 (F / B) is calculated by subtracting the fixed value due to the steady deviation variation from the secondary instruction pressure Psec (ins). In S6, a control for holding the integral term I of the secondary pressure F / B control at the previous value before the start of the idle stop control is executed.

In this way, since the previous value of the integral term I is held during the idling stop control, unnecessary accumulation of the integral term I is prevented when the engine 1 returns from the stopped state to the operation of the engine 1. Further, during idling stop control, it is not necessary to consider belt slippage, and thus the first feedback lower limit value Low1 (F / B) need not be set. Further, since it is not desired to adjust the secondary pressure Psec, the secondary instruction pressure will continue to output the maximum value instruction.

When it is determined that the secondary pressure F / B control is not in the prohibited area and the idling stop control is not performed, the flow proceeds to S1 → S4 → S7 → S8 → S9 → S10 → S11 in the flowchart of FIG. Is repeated. In S7, the required hydraulic pressure A is calculated from the input torque and the winding diameter (= the gear ratio of the variator 4). In S8, the correction amount B for the undershoot is calculated from the oil temperature table. In S9, the correction amount C for the steady deviation is calculated from the oil temperature and the oil temperature zone map. In S10, the first feedback lower limit value Low1 (F / B) is the first feedback lower limit value Low1 (F / B) = required hydraulic pressure A + (correction amount B for undershoot) + (correction amount C for steady deviation) It is calculated by the formula. In S11, normal secondary pressure F / B control by PID control is executed.

Thus, when the secondary pressure F / B control is executed in S11, the decrease in the post-F / B command pressure Psec (F / B) is caused by the first feedback lower limit value Plow1 (F / B) calculated in S10. Will be limited by. In other words, the post-F / B indicating pressure Psec (F / B) does not become lower than the first feedback lower limit value Plow1 (F / B) even if the pressure adjustment is inadequate, and the post-F / B indicating pressure Psec (Fsec) By limiting the lower limit of (F / B), belt slip is reliably prevented when returning from poor pressure regulation.

As described above, in the control device for the belt type continuously variable transmission CVT of the first embodiment, the effects listed below can be obtained.

(1) A continuously variable transmission mechanism which is interposed between a driving source for driving (engine 1) and driving wheels 6 and has a primary pulley 42, a secondary pulley 43, and a belt 44 stretched over both pulleys 42, 43 ( Variator 4),
A transmission controller (CVT control unit 8) for controlling the shift hydraulic pressure of the continuously variable transmission mechanism (variator 4);
In a control device for a continuously variable transmission (belt type continuously variable transmission CVT) including:
In the transmission controller (CVT control unit 8),
A hydraulic feedback control section 8a for adjusting the hydraulic pressure of the continuously variable transmission mechanism (variator 4) by hydraulic feedback control including an integral term based on a deviation between a target value and an actual value;
A feedback lower limit value setting unit that sets a feedback lower limit value (first feedback lower limit value Plow1 (F / B)) that limits a decrease in secondary indicated pressure (post-F / B indicated pressure Psec (F / B)) due to hydraulic feedback control 8b and
The feedback lower limit value setting unit 8b determines the feedback lower limit value (first feedback lower limit value Plow1 (F / B)) from the necessary hydraulic pressure A for the torque capacity with a safety factor of 1 for securing the belt 44 and poor pressure regulation. Set to a value obtained by adding a margin that takes into consideration the undershoot of the secondary actual pressure Psec (Real) at the time of return of.
Therefore, at the time of recovery from poor pressure regulation, it is possible to prevent the occurrence of belt slippage by avoiding the capacity shortage due to the hydraulic pressure feedback control of the secondary pressure Psec.

(2) The feedback lower limit value setting unit 8b sets the margin considering the undershoot to the correction amount B for the undershoot when the secondary actual pressure Psec (Real) decreases at the time of recovery from poor regulation, and the secondary actual pressure. The correction amount C for the steady deviation between Psec (Real) and the secondary indicated pressure (the indicated pressure after F / B Psec (F / B)) by the hydraulic feedback control is set to a value obtained by adding.
Therefore, the feedback lower limit value (first feedback lower limit value Plow1 (F / B)) can be set to a value that has the best component protection performance among the settings that satisfy the fuel consumption requirement.
That is, the added value of the required oil pressure A and the correction amount B for the undershoot shares the component protection performance by preventing the belt slippage. Then, the smaller the correction amount added to the added value of the required hydraulic pressure A and the correction amount B, the higher the fuel consumption performance for suppressing friction. At this time, the correction amount to be added to the added value of the required hydraulic pressure A and the correction amount B is not the fixed value that absorbs the hydraulic pressure variation but the correction amount C for the steady deviation for each unit. It can be a quantity C.

(3) The drive source for traveling is the engine 1 that stops the operation by idle stop control when the vehicle is stopped,
The transmission controller (CVT control unit 8) includes an idle stop control during-determination unit 8c that determines whether or not idle stop control is in progress,
The feedback lower limit value setting unit 8b does not need to set the feedback lower limit value (first feedback lower limit value Plow1 (F / B)) when the idle stop control determination unit 8c determines that the idle stop control is being performed.
When the idle stop control determination unit 8c determines that the idle stop control is being performed, the hydraulic feedback control unit 8a keeps the integral term I of the feedback operation amount at the previous value before the start of the idle stop control.
Therefore, when the operation of the engine 1 is restored from the stopped state of the engine 1, unnecessary accumulation of the integral term I can be prevented. In addition, during idling stop control, it is possible to stop setting the feedback lower limit value (first feedback lower limit value Low1 (F / B)) because the vehicle is stopped without consideration of belt slippage.

(4) The transmission controller (CVT control unit 8) has a feedback-off determination unit 8d that determines whether to turn off the hydraulic feedback control,
The feedback lower limit value setting unit 8b does not need to set the feedback lower limit value (first feedback lower limit value Low1 (F / B)) when the feedback off determination unit 8d determines to turn off the hydraulic feedback control.
The hydraulic pressure feedback control unit 8a sets the feedback operation amount to zero when the feedback OFF determination unit 8d determines to turn off the hydraulic pressure feedback control.
Therefore, when the hydraulic pressure feedback control is being determined to be off, the secondary pressure control can be performed with the feedback operation amount set to zero. In addition, during the hydraulic feedback control OFF determination, the feedback operation amount is zero even if pressure regulation fails, so it is not necessary to set the feedback lower limit value (first feedback lower limit value Low1 (F / B)). be able to.

(5) When the feedback lower limit value based on the required hydraulic pressure A for the torque capacity for securing the belt 44 (the torque capacity according to the safety factor 1) is referred to as the first feedback lower limit value Low1 (F / B),
When the setting of the first feedback lower limit value Low1 (F / B) is unnecessary, the feedback lower limit value setting unit 8b subtracts the fixed value due to the steady deviation variation from the secondary indicated pressure Psec (inc), and the second feedback lower limit value Low2. Set to (F / B).
In this way, since the first feedback lower limit value Low1 (F / B) and the second feedback lower limit value Low2 (F / B) are set as the feedback lower limit value, it is possible to achieve both the component protection requirement and the fuel consumption requirement. it can.
That is, the first feedback lower limit value Low1 (F / B) suppresses belt slippage at the time of recovery from poor pressure regulation and protects the components of the continuously variable transmission mechanism (variator 4). On the other hand, the second feedback lower limit value Low2 (F / B) prevents the secondary actual pressure Psec (Real) from exceeding the secondary instruction pressure Psec (inc) and does not worsen the friction, so that the required fuel efficiency performance can be obtained. Secure.

The control device for the continuously variable transmission according to the present invention has been described above based on the first embodiment. However, the specific configuration is not limited to the first embodiment, and design changes and additions are allowed without departing from the gist of the invention according to each claim of the claims.

In the first embodiment, as the feedback lower limit value setting unit 8b, a value obtained by adding the first feedback lower limit value Low1 (F / B) to the necessary hydraulic pressure A, the correction amount B for the undershoot and the correction amount C for the steady deviation. The example of setting to. However, the feedback lower limit value setting unit may set the first feedback lower limit value to a value obtained by adding the required hydraulic pressure and the correction amount for the undershoot. Further, the first feedback lower limit value may be set to a value obtained by adding the necessary oil pressure, the correction amount for undershoot, and the fixed correction amount.

In the first embodiment, an example in which the control device of the present invention is applied to an engine vehicle with an idle stop function equipped with a belt type continuously variable transmission CVT is shown. However, the control device of the present invention may be applied to a vehicle equipped with a continuously variable transmission mechanism with an auxiliary transmission. Further, the applicable vehicle is not limited to an engine vehicle with an idle stop function, but can be applied to a hybrid vehicle having an engine and a motor as a drive source for traveling.

Claims (5)

A continuously variable transmission mechanism having a primary pulley, a secondary pulley, and a belt stretched over both pulleys, which is interposed between a traveling drive source and drive wheels,
A transmission controller for controlling the shift hydraulic pressure of the continuously variable transmission mechanism,
In a control device for a continuously variable transmission including
In the transmission controller,
A hydraulic feedback control unit that regulates the shift hydraulic pressure of the continuously variable transmission mechanism by a hydraulic feedback control including an integral term based on a deviation between a target value and an actual value;
A feedback lower limit value setting unit that sets a feedback lower limit value that limits a decrease in the secondary instruction pressure due to the hydraulic pressure feedback control,
The feedback lower limit value setting unit sets the feedback lower limit value to a necessary hydraulic pressure for a torque capacity for securing the belt clamping, and a margin considering an undershoot of the secondary actual pressure at the time of recovery from poor pressure regulation. A control device for a continuously variable transmission that sets the added value. The control device for a continuously variable transmission according to claim 1,
The feedback lower limit value setting unit adjusts the margin considering the undershoot by a correction amount for the undershoot when the secondary actual pressure decreases at the time of recovery from poor regulation, the secondary actual pressure and the hydraulic pressure feedback control. A control device for a continuously variable transmission, which sets a value obtained by adding a correction amount corresponding to a steady-state deviation from a secondary instruction pressure. A control device for a continuously variable transmission according to claim 1 or 2,
The drive source for traveling is an engine that stops operation by idle stop control when the vehicle is stopped,
The transmission controller has an idle stop control determination unit that determines whether or not idle stop control is in progress,
The feedback lower limit value setting unit makes it unnecessary to set the feedback lower limit value when it is determined by the idle stop control during determination unit that the idle stop control is being performed,
When the idle stop control during-judgment unit determines that the idle stop control is being performed, the hydraulic pressure feedback control unit maintains the integral term of the feedback operation amount at the previous value before the start of the idle stop control. Transmission control device. A control device for a continuously variable transmission according to any one of claims 1 to 3,
The transmission controller has a feedback off determination unit that determines whether to turn off the hydraulic pressure feedback control,
The feedback lower limit value setting unit does not need to set the feedback lower limit value when the feedback OFF determination unit determines to turn off the hydraulic pressure feedback control,
The control device for a continuously variable transmission, wherein the hydraulic feedback control unit sets the feedback operation amount to zero when the feedback OFF determination unit determines to turn off the hydraulic feedback control. In the control device for the continuously variable transmission according to claim 3 or 4,
When the feedback lower limit value based on the necessary hydraulic pressure for the torque capacity for securing the belt is referred to as a first feedback lower limit value,
When it is unnecessary to set the first feedback lower limit value, the feedback lower limit value setting unit sets the second feedback lower limit value obtained by subtracting a fixed value due to the steady deviation variation from the secondary instruction pressure. Control device.

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