JP2011069406A - Control device of vehicular driving system friction element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a vehicular driving system friction element achieving both improvement of durability of a friction element and improvement of accelerating performance of a vehicle. <P>SOLUTION: A friction element control part (Figure 4) is arranged between a driving source (Engine Eng) of the vehicle and driving wheels (left/right driving wheels LT, RT) for slip fastening the friction element (starting clutch CL1) which disconnects torque transmission. In the friction element control part, a limit value of clutch transmission torque is set so that the maximum energy obtained by a clutch heat radiation power calculation means (step S11), which is absorbed by the friction element, corresponds to energy obtained by a clutch absorbing power calculation part (step S12) which is absorbed by the friction element. As a difference rotation ΔN of the friction element CL1 obtained by a difference rotation calculation means (step S2) becomes smaller, the clutch transmission torque limit value is made higher. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle drive system friction element control device including a friction element control unit that slip-fastens a friction element disposed in a vehicle drive system.

  2. Description of the Related Art Conventionally, there is known a control device for a vehicle drive system friction element that slips a drive system friction element disposed between an engine and a continuously variable transmission when the vehicle starts (see, for example, Patent Document 1).

  In this vehicle drive system friction element control device, when the gear ratio of the continuously variable transmission at the time of starting is higher than the lowest gear ratio, the transmission torque of the friction element is corrected to increase so that the differential rotation of the friction element is reduced. Control to make it smaller.

JP 2008-75838 A

  By the way, in general, the engine needs to rotate at the engine stall avoidance lower limit rotational speed, that is, the so-called idling rotational speed. Therefore, in the conventional vehicle drive system friction element control device, when the transmission torque is increased and corrected so that the engine speed that decreases with the increase in the transmission torque of the friction element does not fall below the engine stall avoidance lower limit speed. The upper limit value is set.

  As a result, the upper limit value of the transmission torque of the friction element is limited, and accordingly, the differential rotation at the time of slip engagement is increased, the energy absorbed by the friction element is increased, and the durability of the friction element is deteriorated. In addition, by limiting the upper limit value of the transmission torque of the friction element, there is a problem that the transmission torque cannot be increased by the limited amount and the acceleration performance is not good.

  The present invention has been made paying attention to the above problems, and provides a vehicle drive system friction element control device capable of achieving both improvement in durability of the friction element and improvement in acceleration performance of the vehicle. Objective.

  In order to achieve the above object, in the vehicle drive system friction element control device of the present invention, a friction element control unit that slip-fastens a friction element that is disposed between a drive source of a vehicle and a drive wheel and that connects and disconnects torque transmission. Is provided. The friction element control unit transmits torque generated by the friction element so that the maximum energy that can be absorbed by the friction element obtained by the clutch heat dissipation power calculation means matches the energy that is absorbed by the friction element obtained by the clutch absorption power calculation unit. Is set, and the upper limit value is increased as the differential rotation of the friction element obtained by the differential rotation calculation means is smaller.

  In the control device for a vehicle drive system friction element according to the present invention, both the durability of the friction element and the acceleration performance of the vehicle can be improved by the above configuration.

1 is an overall system diagram illustrating a vehicle to which a control device according to a first embodiment is applied. It is a figure which shows an example of the shift diagram of the continuously variable transmission set to the integrated controller of Example 1. FIG. FIG. 3 is a control block diagram illustrating a vehicle control system at start included in the integrated controller according to the first embodiment. 3 is a flowchart illustrating a flow of a friction element control process (friction element control unit) executed by the integrated controller according to the first embodiment. It is an example of the map which shows the relationship between the gear ratio at the time of a stop, and clutch absorption power. It is an example of the map which shows the relationship between clutch differential rotation and a clutch transmission torque limit value. It is a time chart which shows each characteristic at the time of clutch power restriction start mode in vehicles to which a control device of Example 1 is applied, (a) shows characteristics of engine speed, primary speed, and vehicle speed, (b) shows the characteristics of the clutch transmission torque limit value / clutch transmission torque command value, and (c) shows the characteristics of the clutch transmission torque limit value / engine torque command value. FIG. 5 is a time chart showing characteristics in a normal start mode in a vehicle to which the control device of Embodiment 1 is applied, where (a) shows characteristics of engine speed, primary speed, and vehicle speed; ) Shows the characteristics of the clutch transmission torque limit value / clutch transmission torque command value, and (c) shows the characteristics of the clutch transmission torque limit value / engine torque command value.

  Hereinafter, the best mode for realizing an electric vehicle control apparatus of the present invention will be described based on Example 1 shown in the drawings.

First, the configuration will be described.
FIG. 1 is an overall system diagram illustrating a vehicle to which a control device according to a first embodiment is applied.

  As shown in FIG. 1, the drive system of the vehicle in the first embodiment includes an engine Eng, a starting clutch (friction element) CL1, a continuously variable transmission CVT, a final gear FG, a differential gear DE, and a left drive wheel. LT and right drive wheel RT are provided.

  The engine Eng is a gasoline engine or a diesel engine. Based on the engine torque command value from the integrated controller 1, the engine Eng is controlled by controlling the intake air amount by the throttle actuator, the fuel injection amount by the injector, and the ignition timing by the spark plug. The engine torque corresponding to the torque command value is output. In addition, engine start control, engine stop control, throttle valve opening control, fuel cut control, and the like are performed as necessary.

  The starting clutch CL1 is a friction element (clutch) that is disposed between the engine Eng and the continuously variable transmission CVT to connect and disconnect torque. The starting clutch CL1 is controlled based on the clutch transmission torque command value from the integrated controller 1 and is controlled for engagement / slip engagement (half-engagement) / release by a clutch control oil pressure generated by a hydraulic unit (not shown). The transmission torque corresponding to is output. As this starting clutch CL1, for example, a normally closed wet multi-plate clutch that is fully engaged by an urging force of a diaphragm spring and controlled from complete engagement to slip engagement to complete release by stroke control using a hydraulic actuator. Is used.

  The continuously variable transmission CVT has a continuously variable transmission function capable of continuously changing the gear ratio while setting the gear ratio continuously. In the first embodiment, the primary pulley PrP, the secondary pulley SeP, and the belt B Is a belt type continuously variable transmission. In this continuously variable transmission CVT, the distance between the primary pulleys PrP is changed to change the diameter of the contact circle of the belt B, and the distance between the secondary pulleys SeP is also changed in conjunction with this to change the diameter of the contact circle of the belt B. By changing the speed, the speed is continuously changed. Here, the primary pulley PrP is connected to the input shaft (primary shaft) IN and is connected to the engine Eng via the start clutch CL1. The secondary pulley SeP is connected to the output shaft OUT, and is connected to the left and right drive wheels LT and RT through the final gear FG and the differential gear DE in this order.

  FIG. 2 shows an example of a shift diagram of the continuously variable transmission CVT. In this shift diagram, the horizontal axis represents the vehicle speed, the vertical axis represents the engine speed, and the vehicle speed and engine speed are determined for each accelerator opening. Of the two straight lines going up to the right, the left straight line is the lowest gear ratio, and the right straight line is the highest gear ratio. The gear ratio in the continuously variable transmission CVT is determined by the accelerator opening, the vehicle speed, and the engine speed between these two lines.

  The integrated controller 1 outputs the engine torque command and the clutch transmission torque command corresponding to the accelerator opening as much as possible without impairing the durability of the starting clutch CL1, thereby accelerating the clutch durability and the acceleration request. It bears the function to make it compatible. The integrated controller 1 includes engine speed information from the engine speed sensor 2, primary pulley speed information from the primary pulley speed sensor 3, secondary pulley speed information from the secondary pulley speed sensor 4, accelerator The accelerator opening information from the opening sensor 5 is input, the engine torque command value is output to the engine Eng, and the clutch transmission torque command value is output to the starting clutch CL1.

  FIG. 3 is a control block diagram showing the vehicle control system at start included in the integrated controller 1.

  The integrated controller 1 includes a gear ratio calculation unit 1a, a vehicle speed calculation unit 1b, a clutch differential rotation calculation unit 1c, a clutch heat dissipation power calculation unit 1d, a required engine torque calculation unit 1e, a clutch temperature calculation unit 1f, Clutch overheat determination unit 1g, normal start permission determination unit 1h, vehicle stop determination unit 1i, clutch engagement determination unit 1j, start mode selection unit 1k, target engine speed calculation unit 1m, and engine speed feedback torque It has a calculation unit 1n, a clutch transmission torque limit value calculation unit 1p, a clutch transmission torque calculation unit 1q, and an engine torque calculation unit 1r.

  The gear ratio calculation unit 1 a inputs primary pulley rotation speed information from the primary pulley rotation speed sensor 3 and inputs secondary pulley rotation speed information from the secondary pulley rotation speed sensor 4. Then, the gear ratio of the continuously variable transmission CVT is calculated by dividing the secondary pulley rotation speed from the primary pulley rotation speed. The gear ratio information is output to the normal start possibility determination unit 1h. When the secondary pulley rotational speed is zero (immediately after starting), the previous gear ratio is maintained.

The vehicle speed calculation unit 1b inputs secondary pulley rotation speed information from the secondary pulley rotation speed sensor 4 and stores a preset differential gear ratio and tire moving radius. And vehicle speed is calculated by following formula (1), and vehicle speed information is output to the vehicle stop determination part 1i.
Vehicle speed [m / s] = (secondary pulley speed [rpm] / 60) × 2 × π
× Tire dynamic radius [m] × (1 / Differential gear ratio) ・ ・ （1）

  The clutch differential rotation calculation unit 1 c receives engine rotation speed information from the engine rotation speed sensor 2 and receives primary pulley rotation speed information from the primary pulley rotation speed sensor 3. Then, the clutch differential rotation ΔN of the starting clutch CL1 is calculated by subtracting the primary pulley rotational speed from the engine rotational speed. The clutch differential rotation information is output to the clutch temperature calculation unit 1f, the clutch engagement determination unit 1j, and the clutch transmission torque limit value calculation unit 1p.

The clutch heat dissipation power calculation unit 1d inputs start clutch temperature information, lubricating oil amount information, and oil temperature information from detection means (not shown). Then, the clutch heat dissipation power is calculated based on the starting clutch temperature, the amount of lubricating oil, and the oil temperature. The clutch heat dissipation power information is output to the clutch temperature calculation unit 1f and the clutch transmission torque limit value calculation unit 1p.
Here, the clutch heat dissipation power is the maximum energy that can be absorbed by the start clutch CL1 when the start clutch CL1 is engaged, and is the maximum temperature at which the start clutch CL1 does not deteriorate in durability. For simplification, the clutch heat dissipation power at which the start clutch temperature is saturated at the “maximum temperature at which the start clutch CL1 does not deteriorate durability” may be experimentally obtained.

  The requested engine torque calculation unit 1 e inputs accelerator opening information from the accelerator opening sensor 5. Then, the required engine torque is calculated according to the accelerator opening. The requested engine torque information is output to the clutch transmission torque calculator 1q and the engine torque calculator 1r. The relationship between the accelerator opening and the required engine torque may be set in advance in a map, and the required engine torque may be obtained using this map.

The clutch temperature calculation unit 1f receives clutch differential rotation information from the clutch differential rotation calculation unit 1c, receives clutch heat dissipation power information from the clutch heat dissipation power calculation unit 1d, and receives a clutch transmission torque command value from the clutch transmission torque calculation unit 1q. Enter. First, the clutch absorption power is calculated by multiplying the clutch differential rotation ΔN by the clutch transmission torque. Next, the clutch heat dissipation power is subtracted from the clutch absorption power and integrated to calculate the clutch temperature of the starting clutch CL1. The clutch temperature information is output to the clutch overheat determination unit 1g. A sensor for detecting the clutch temperature may be provided in the starting clutch CL1, and the clutch temperature may be detected by this sensor.
Here, the clutch absorption power is energy that the start clutch CL1 absorbs at the time of slip engagement. This clutch absorption power becomes a hyperbola when the clutch differential rotation ΔN is taken on the horizontal axis and the clutch transmission torque is taken on the vertical axis.

  The clutch overheat determination unit 1g receives clutch temperature information from the clutch temperature calculation unit 1f. Then, it is determined whether or not the clutch temperature exceeds a maximum temperature (hereinafter referred to as a boundary temperature α) at which the start clutch CL1 does not deteriorate in durability (is a clutch overheated state), and the determination result is sent to the start mode selection unit 1k. Is output. In the clutch overheat determination unit 1g, if the clutch temperature is equal to or higher than the boundary temperature α, the clutch is overheated. If the clutch temperature is lower than the boundary temperature α, the clutch overheat determination unit 1g is set to a non-overheated state.

The normal start permission / non-permission determination unit 1h receives the gear ratio information of the continuously variable transmission CVT from the gear ratio calculation unit 1a. Then, it is determined whether the speed ratio is higher or lower than the previously determined start threshold value β, and the determination result is output to the start mode selection unit 1k.
In this normal start possibility determination unit 1h, normal start is impossible if the gear ratio is higher than the start threshold β, and normal start is possible if the gear ratio is lower than the start threshold β.

The vehicle stop determination unit 1i inputs vehicle speed information from the vehicle speed calculation unit 1b. Then, it is determined whether or not the vehicle speed is equal to or less than a predetermined stop threshold value γ, and the determination result is output to the start mode selection unit 1k.
In the vehicle stop determination unit 1i, the vehicle is stopped if the vehicle speed is equal to or lower than the stop threshold γ, and the vehicle is not stopped if the vehicle speed is higher than the stop threshold γ.

The clutch engagement determination unit 1j receives the clutch differential rotation information of the starting clutch CL1 from the clutch differential rotation calculation unit 1c. Then, it is determined whether or not the clutch differential rotation ΔN is equal to or less than a predetermined clutch engagement threshold δ, and the determination result is output to the clutch transmission torque limit value calculation unit 1p.
In this clutch engagement determination unit 1j, if the clutch differential rotation ΔN is less than or equal to the clutch engagement threshold δ, the start clutch CL1 is in a fully engaged state, and if the clutch differential rotation ΔN is greater than the clutch engagement threshold δ, the start clutch CL1 is incomplete. Let it be a fastening state (a slip fastening state-an open state).

The start mode selection unit 1k receives the overheat determination information from the clutch overheat determination unit 1g, receives the determination information from the normal start possibility determination unit 1h, receives the stop determination information from the vehicle stop determination unit 1i, and engages the clutch. The fastening determination information is input from the determination unit 1j. Then, the start mode is selected based on each information, and the selection result is output to the target engine speed calculation unit and the clutch transmission torque limit value calculation unit.
In the start mode selection unit 1k, the normal start mode is selected when the vehicle stop is determined and the normal start is possible. In addition, in the case of vehicle stop determination and normal start impossible determination, the clutch power limit start mode is selected. Further, in the case of clutch overheat determination regardless of the vehicle stop determination, the clutch power limit start mode is selected.

The target engine speed calculation unit 1m inputs accelerator opening information from the accelerator opening sensor 5, and inputs mode selection information from the start mode selection unit 1k. Then, the target engine speed is calculated based on each information, and the target engine speed information is output to the engine speed feedback torque calculator 1n.
The target engine speed calculator 1m calculates a target engine speed corresponding to the accelerator opening when the normal start mode is selected. When the clutch power limit start mode is selected, the engine stall avoidance lower limit rotational speed is set as the target engine rotational speed. The relationship between the accelerator opening and the target engine speed may be set in advance in a map, and the target engine speed may be obtained using this map.

  The engine speed feedback torque calculation unit 1n receives engine speed information from the engine speed sensor 2, and receives target engine speed information from the target engine speed calculation unit 1m. Then, an engine torque adjustment torque (engine speed feedback torque) is calculated so that the target engine speed matches the actual engine speed, and the engine speed feedback torque information is output to the engine torque calculator 1r. . As this engine speed feedback torque calculation unit 1n, for example, a known PI feedback controller is used.

The clutch transmission torque limit value calculation unit 1p inputs the clutch differential rotation information of the start clutch CL1 from the clutch differential rotation calculation unit 1c, and inputs the clutch heat dissipation power information of the start clutch CL1 from the clutch heat dissipation power calculation unit 1d. Mode selection information is input from the mode selection unit 1k. Based on each information, a clutch transmission torque limit value, which is an upper limit value of the transmission torque by the starting clutch CL1, is calculated. The clutch transmission torque limit value information is output to the clutch transmission torque calculator 1q.
In the clutch transmission torque limit value calculation unit 1p, when the normal start mode is selected, the maximum torque that can be transmitted by design in the start clutch CL1 is set as the clutch transfer torque limit value. In addition, when the clutch power limit start mode is selected, a value obtained by dividing the clutch differential rotation ΔN from the clutch heat dissipation power is set as the clutch transmission torque limit value.

The clutch transmission torque calculation unit 1q receives the request engine torque information from the request engine torque calculation unit 1e, receives the clutch engagement information from the clutch engagement determination unit 1j, and receives the clutch transmission torque limit from the clutch transmission torque limit value calculation unit 1p. Enter value information. Then, a clutch transmission torque command value is calculated based on each information, and the clutch transmission torque command value information is output to the starting clutch CL1 and the clutch temperature calculation unit 1f.
The clutch transmission torque calculation unit 1q calculates a clutch transmission torque command value according to the required engine torque when the normal start mode is selected when the clutch is not engaged. In addition, when the clutch power limit start mode is selected during the clutch non-engagement determination, a clutch transmission torque command value is calculated according to the clutch transmission torque limit value, and when the clutch transmission torque limit value reaches the required engine torque, the required engine torque is calculated. The clutch transmission torque command value is calculated accordingly. Furthermore, when determining whether the clutch is completely engaged, the torque (for example, the maximum torque that can be transmitted by design) that allows the start clutch CL1 to be completely engaged is used as the clutch transmission torque command value.

The engine torque calculation unit 1r receives request engine torque information from the request engine torque calculation unit 1e, receives clutch engagement information from the clutch engagement determination unit 1j, and receives engine rotation rate feedback torque from the engine rotation number feedback torque calculation unit 1n. Enter information. Then, an engine torque command value is calculated based on each information, and the engine torque command value information is output to the engine Eng.
In the engine torque calculator 1r, the engine speed feedback torque is used as the engine torque command value when the clutch is not engaged. Further, at the time of clutch complete engagement determination, an engine torque command value is calculated according to the required engine torque. Here, since the clutch transmission torque is limited when it is determined that the clutch is not engaged, the engine speed feedback torque information from the engine speed feedback torque calculator 1n is also automatically adjusted.

  FIG. 4 is a flowchart illustrating a flow of a friction element control process (friction element control unit) executed by the integrated controller of the first embodiment. Hereinafter, each step of FIG. 4 will be described.

  In step S1, it is determined whether or not the starting clutch CL1 is in a fully opened state. If YES (fully opened), step S1 is repeated, and if NO (not fully opened), the process proceeds to step S2. To do. Here, the state of the starting clutch CL1 is determined based on the magnitude of the clutch control hydraulic pressure.

  In step S2, following the determination that the starting clutch CL1 is not completely released in step S1, the primary pulley rotational speed is subtracted from the engine rotational speed to calculate the clutch differential rotation ΔN of the starting clutch CL1, and the process proceeds to step S3. This step S2 corresponds to differential rotation calculation means for obtaining the clutch differential rotation ΔN when the start clutch CL1 is slip-engaged.

  In step S3, it is determined whether or not the starting clutch CL1 is in a completely engaged state, that is, whether or not the clutch differential rotation ΔN obtained in step S2 is equal to or less than a predetermined clutch engagement threshold δ. If δ or less = completely engaged state), the process proceeds to step S4. If NO (greater than the clutch engagement threshold δ = incompletely engaged state; slip engaged state), the process proceeds to step S7.

  In step S4, following the determination that the start clutch CL1 is completely engaged in step S3, the clutch complete engagement torque, for example, the maximum torque that can be transmitted by design in the start clutch CL1, is set as the clutch transmission torque command value. The torque command value is output to the starting clutch CL1, and the process proceeds to step S5.

  In step S5, the required engine torque is calculated according to the accelerator opening, and the process proceeds to step S6.

  In step S6, based on the determination that the starting clutch CL1 is completely engaged in step S3, the required engine torque obtained in step S5 is set as the engine torque command value, and this engine torque command value is output to the engine Eng to the end. Then, the friction element control process is terminated.

  In step S7, following the determination that the starting clutch CL1 is not completely engaged (slip engagement) in step S3, the vehicle speed is calculated by the above equation (1) from the secondary pulley rotation speed, the differential gear ratio, and the tire radius. The process proceeds to step S8.

  In step S8, it is determined whether or not the vehicle is in a stopped state, that is, whether or not the vehicle speed calculated in step S7 is equal to or less than a predetermined stop threshold γ, and YES (vehicle speed ≦ stop threshold γ; vehicle stop) ), The process proceeds to step S9. If NO (vehicle speed> stop threshold γ; vehicle non-stop), the process proceeds to step S11.

  In step S9, following the determination that the vehicle is stopped in step S8, the gear ratio of the continuously variable transmission CVT is calculated by dividing the secondary pulley rotation speed from the primary pulley rotation speed, and the process proceeds to step S10. When the secondary pulley rotational speed is 0 rpm, the gear ratio calculated immediately before is maintained. This step S9 corresponds to a gear ratio calculating means for obtaining the gear ratio of the continuously variable transmission CVT.

  In step S10, it is determined whether or not the vehicle can normally start, that is, whether or not the speed ratio calculated in step S9 is higher or lower than the start threshold value β, and YES (normal start possible = speed ratio low side). If NO, the process proceeds to step S11. If NO (normal start is impossible = transmission ratio high side), the process proceeds to step S14. This step S10 is based on the speed ratio of the continuously variable transmission CVT when the vehicle is stopped, and the maximum torque that can be absorbed by the start clutch CL1 is equal to the energy absorbed by the start clutch CL1. This corresponds to control mode determination means for determining whether or not to set an upper limit value.

  In step S11, following the determination that the vehicle is not stopped in step S8 or the normal start is possible in step S10, the maximum energy that can be absorbed by the starting clutch CL1 is determined from the clutch temperature, the lubricating oil amount, and the oil temperature. The clutch heat dissipation power of a certain starting clutch CL1 is calculated, and the process proceeds to step S12. For simplification, the clutch heat dissipation power at which the start clutch temperature is saturated at the “maximum temperature at which the start clutch CL1 does not deteriorate durability” may be experimentally obtained. This step S11 corresponds to clutch heat radiation power calculating means for obtaining the maximum energy that can be absorbed by the starting clutch CL1.

In step S12, the clutch differential rotation ΔN of the start clutch CL1 obtained in step S2 is multiplied by the maximum clutch transmission torque in the start clutch CL1, and the clutch absorption power, which is the energy that the start clutch CL1 absorbs at the time of slip engagement, is calculated. The process proceeds to step S13. This step S12 corresponds to a clutch absorption power calculation means for obtaining energy that the start clutch CL1 absorbs at the time of slip engagement.
The “clutch transmission maximum torque” is the maximum torque that can be transmitted in the starting clutch CL1. Here, when obtaining the clutch absorption power, it is not always necessary to use the “clutch transmission maximum torque”. For example, it is generally possible to define an acceleration necessary for vehicle start, obtain a required driving torque based on this acceleration, and use a clutch transmission torque calculated in consideration of the gear ratio at that time.

  In step S13, the clutch heat dissipation power obtained in step S11 is subtracted from the clutch absorption power obtained in step S12, and further integrated to calculate the clutch temperature of the starting clutch CL1, and the process proceeds to step S14. Note that the clutch temperature of the starting clutch CL1 may be detected using a sensor that detects the temperature.

  In step S14, it is determined whether or not the starting clutch CL1 is in an overheated state, that is, whether or not the clutch temperature obtained in step S13 exceeds the boundary temperature α (the maximum temperature at which the starting clutch CL1 does not deteriorate in durability). If (clutch overheat state = clutch temperature> boundary temperature α), the process proceeds to step S15. If NO (clutch non-overheat state = clutch temperature ≦ boundary temperature α), the process proceeds to step S16.

  In step S15, the start mode is set to “clutch power limited start mode” following either the determination that normal start is impossible in step S10 or the determination that the start clutch CL1 is overheated in step S14. Control goes to step S17.

  In step S16, following the determination that normal start is possible in step S10 and the determination that the start clutch CL1 is not overheated in step S14, the start mode is set to “normal start mode”, and the process proceeds to step S17.

In step S17, a clutch transmission torque limit value which is an upper limit value of the transmission torque by the starting clutch CL1 is calculated, and the process proceeds to step S18.
Here, when the clutch power limit start mode is set in step S15, the clutch transmission torque limit value is obtained by dividing the clutch differential rotation ΔN determined in step S2 from the clutch heat dissipation power determined in step S11. Ask. Thus, the clutch transmission torque upper limit value increases as the clutch differential rotation ΔN decreases. When the value obtained by dividing the clutch differential rotation ΔN from the clutch heat dissipation power exceeds the maximum torque that can be transmitted in the design of the starting clutch CL1, this maximum torque is set as the clutch transmission torque limit value.
When the clutch temperature of the starting clutch CL1 obtained in step S13 is lower than a preset allowable temperature (<boundary temperature α), the clutch transmission torque limit value may be set slightly larger to increase acceleration. Alternatively, the clutch transmission torque limit value may be set slightly smaller in consideration of the safety factor.
When the normal start mode is set in step S16, the maximum torque that can be transmitted by design in the start clutch CL1 is set as the clutch transfer torque limit value. That is, when the normal start mode is set, the clutch transmission torque limit value is not substantially set.

  In step S18, the required engine torque is calculated according to the accelerator opening, and the routine proceeds to step S19.

In step S19, a clutch transmission torque command value is set based on the clutch transmission torque limit value obtained in step S17 and the required engine torque obtained in step S18, and this clutch transmission torque command value is set to the start clutch CL1. The process proceeds to step S20.
Here, when the clutch power limit start mode is set in step S15, in order to limit the clutch transmission torque command value with the clutch transmission torque limit value, the clutch transmission torque limit value is first set to the clutch transmission torque command value.
If the normal start mode is set in step S16, the required engine torque is set to the clutch transmission torque command value from the beginning. At this time, the clutch maximum transmission torque may be the clutch transmission torque command value.

In step S20, the target engine speed is calculated, and the process proceeds to step S21.
Here, when the clutch power limit start mode is set in step S15, the engine stall avoidance lower limit rotational speed (idle rotational speed) is set to the target engine rotational speed.
When the normal start mode is set in step S16, the target engine speed corresponding to the accelerator opening is calculated. The relationship between the accelerator opening and the target engine speed may be set in advance in a map, and the target engine speed may be obtained using this map.

  In step S21, based on the target engine speed obtained in step S20 and the actual engine speed, the engine speed that is the engine torque adjustment torque so that the target engine speed matches the actual engine speed. The feedback torque is calculated, and the process proceeds to step S22. As an implementation of step S21, for example, a PI feedback controller is used.

In step S22, when the clutch is not engaged, an engine torque command value is set based on the requested engine torque obtained in step S18 and the engine speed feedback torque obtained in step S21. The value is output to the engine Eng, and the process moves to the end to end the friction element control process.
When the normal start mode is set in step S16, the required engine torque is set to the engine torque command value in step S22.

Next, the operation will be described.
First, “conventional vehicle drive system friction element control and its problems” will be described, and then “durability and acceleration improvement coexistence effect” in the vehicle drive system friction element control device of the first embodiment will be described. explain.

[Conventional vehicle driveline friction element control and its problems]
2. Description of the Related Art Conventionally, a vehicle is known in which a friction element such as a start clutch CL1 that connects and disconnects torque transmission is arranged between a drive source (such as an engine and a motor) and a drive wheel. Here, the friction element is slip-engaged in a transitional period of connection / disconnection or when a transmission torque is adjusted. At the time of this slip engagement, heat due to friction, that is, clutch absorption power is generated in the friction element. When this clutch absorption power is large, adverse effects such as early deterioration of the friction element occur.

  Here, in the conventional vehicle drive system friction element control, the clutch transmission torque is set larger as the gear ratio of the continuously variable transmission disposed downstream of the friction element becomes higher. That is, in order to increase the clutch transmission torque, the engagement hydraulic pressure of the friction element is increased and the clutch differential rotation is decreased. This suppresses generation of frictional heat, that is, clutch absorption power, and ensures the durability of the friction element.

  By the way, when the fastening hydraulic pressure of the friction element becomes high, it becomes a load of engine rotation, so that the engine speed decreases. Here, in order to prevent engine stall, it is necessary that the engine speed does not fall below the engine stall avoidance lower limit engine speed. In other words, the engine idling speed must be secured. Therefore, the upper limit value of the clutch transmission torque is set to ensure the necessary engine speed.

  That is, when the clutch transmission torque obtained according to the gear ratio of the continuously variable transmission exceeds the upper limit value, the upper limit value is used for limiting. As a result, the clutch transmission torque necessary for suppressing the clutch absorption power cannot be generated, and the clutch differential rotation is increased. Therefore, although engine stall can be avoided, there is a problem that the clutch absorption power increases due to the large clutch differential rotation, and the durability of the friction element deteriorates.

  Furthermore, since the clutch transmission torque cannot be increased by the amount limited by the upper limit value, there is a problem that the acceleration performance is not good.

[Durability and acceleration improvement compatibility]
In the vehicle to which the vehicle drive system friction element control device of the first embodiment is applied, for example, when starting from a vehicle stop state, in the flowchart shown in FIG. 4, step S 1 → step S 2 → step S 3 → step S 7 → The process proceeds from step S8 to step S9. In step S9, the gear ratio of the continuously variable transmission CVT is calculated, and the process proceeds to step S10.

  In step S10, the start mode is selected depending on whether the transmission gear ratio calculated in step S9 is higher or lower than the start threshold β. If the gear ratio is higher than the start threshold value β and it is determined in step S10 that normal start is impossible, the process proceeds to step S15 to set the clutch power limit start mode. If the gear ratio is lower than the start threshold β and it is determined that normal start is possible in step S10, the clutch heat dissipation power, which is the maximum energy that can be absorbed by the start clutch CL1, is obtained in step S11. Proceed to step S12. Then, by multiplying the clutch transmission maximum torque by the clutch differential rotation ΔN that changes from moment to moment, a clutch absorption power that is energy that the start clutch CL1 absorbs at the time of slip engagement is obtained. Then, the process proceeds from step S13 to step S14, and if the clutch temperature of the start clutch CL1 is overheated, the process proceeds to step S15 to set the clutch power limit start mode. If the clutch temperature of the starting clutch CL1 is not overheated, the routine proceeds to step S16 and the normal starting mode is set.

  Here, the energy (clutch absorption power) absorbed by the start clutch CL1 between the start of the vehicle and the complete engagement of the start clutch CL1 is obtained for each gear ratio at the time of stopping (see FIG. 5).

  In calculating the clutch absorption power, it is not always necessary to use the clutch transmission maximum torque. For example, an acceleration generally required for starting may be defined, a driving torque required for starting may be obtained based on this acceleration, and a clutch transmission torque obtained in consideration of a gear ratio at the time of stopping may be used.

  However, if the clutch transmission torque is lower than the maximum clutch transmission torque, the time until the start clutch CL1 is completely engaged becomes longer, and the energy consumed by the running resistance increases, so the vehicle starts with the maximum clutch transmission torque. The energy (clutch absorption power) absorbed by the starting clutch CL1 will increase.

  Here, since it is impossible to predict how much the driver actually depresses the accelerator, that is, how large the required torque will be, the start threshold β for switching between the normal start mode and the clutch power limit start mode is the clutch transmission maximum. It can be arbitrarily set between the threshold obtained using the torque and the lowest gear ratio.

  Generally, in the continuously variable transmission CVT, when the primary pulley rotation speed and the secondary pulley rotation speed are low, there is a concern about belt slipping, and thus no gear shift is performed. However, when the speed ratio at the time of stopping is close to the highest level, the driving force is insufficient, the vehicle speed does not increase, and it takes time until the starting clutch CL1 is completely engaged. Therefore, when the shift to the low side becomes possible, the energy (clutch absorption power) absorbed by the starting clutch CL1 can be reduced by actively shifting to the low side. Therefore, the clutch absorption power may be calculated on the basis of the clutch differential rotation ΔN considering the shift.

  When the start mode is set in step S15 or step S16, the process proceeds to step S17 to calculate a clutch transmission torque limit value.

  Here, as described above, the clutch absorption power is obtained by multiplying the clutch differential rotation ΔN in the start clutch CL1 by the clutch transmission torque, so if the clutch differential rotation ΔN is taken on the horizontal axis and the clutch transmission torque is taken on the vertical axis, the clutch absorption power is obtained. Becomes a hyperbola.

  Here, if the clutch absorption power is made smaller than the clutch heat dissipation power, the temperature of the starting clutch CL1 does not rise, so that the durability does not deteriorate. However, if the clutch transmission torque is reduced in order to reduce the clutch absorption power, the starting acceleration is also reduced, leading to deterioration in acceleration performance. For this reason, the clutch transmission torque should be increased as much as possible to increase the clutch absorption power.

  Therefore, if the clutch heat dissipation power is set to the upper limit, the clutch transmission torque decreases when the clutch differential rotation ΔN is large, but the clutch transmission torque increases when the clutch differential rotation ΔN is small. It can be enlarged (see FIG. 6).

  From the above, when the start clutch CL1 is slip-engaged, the clutch transmission torque is limited with the clutch heat dissipation power as the upper limit, that is, the maximum energy that can be absorbed by the start clutch CL1 (clutch heat dissipation power) and the energy that the start clutch CL1 absorbs ( The clutch transmission torque limit value, which is the upper limit value of the transmission torque, is set so that the clutch absorption power) matches. The clutch transmission torque limit value is increased as the clutch differential rotation ΔN is smaller. As a result, the required torque of the driver is generated as much as possible to improve the acceleration, and the durability of the clutch can be prevented from being deteriorated, and both the improvement of the durability and the improvement of the acceleration can be achieved.

  In particular, in the vehicle drive system friction element control apparatus according to the first embodiment, the continuously variable transmission CVT is disposed between the starting clutch CL1 and the drive wheels LT and RT, and the gear ratio of the continuously variable transmission CVT is determined in step S9. Ask for. In step S10, the maximum energy that can be absorbed by the start clutch CL1 (clutch heat dissipation power) and the energy that the start clutch CL1 absorbs (clutch absorption power) based on the gear ratio of the continuously variable transmission CVT when the vehicle is stopped. It is determined whether or not the clutch transmission torque limit value, which is the upper limit value of the transmission torque by the starting clutch CL1, is set so as to match.

  For this reason, the clutch transmission torque command value and the engine torque command value are limited according to the gear ratio of the continuously variable transmission CVT when the vehicle is stopped. Can be prevented. Moreover, even if a restriction is necessary, the greatest possible acceleration can be obtained. This will be described below using a time chart.

  FIG. 7 is a time chart showing each characteristic in the clutch power limit start mode in a vehicle to which the control device of the first embodiment is applied. FIG. 7A shows the engine speed, the primary speed, and the vehicle speed. (B) shows the characteristics of the clutch transmission torque limit value / clutch transmission torque command value, and (c) shows the characteristics of the clutch transmission torque limit value / engine torque command value.

  In this clutch power limited start mode, the speed ratio of the continuously variable transmission CVT when the vehicle is stopped is higher than the start threshold β, so the driving force is insufficient and the vehicle speed does not increase, and the start clutch CL1 is fully engaged. It takes time to complete. That is, as shown in FIG. 7 (a), it takes time to increase the primary pulley rotational speed with respect to the engine rotational speed. In FIG. 7 (a), ΔN is the clutch differential rotation.

  Therefore, a clutch transmission torque limit value is set to limit the clutch transmission torque command value and the engine torque command value to be smaller than the required engine torque. As a result, the clutch absorption power does not become larger than the clutch heat dissipation power, and an increase in the clutch temperature is suppressed, and the durability of the start clutch CL1 can be improved.

  Further, the clutch transmission torque limit value is set so that the clutch absorption power and the clutch heat dissipation power coincide with each other, and increases as the clutch differential rotation ΔN decreases.

  For this reason, the clutch transmission torque command value and the engine torque command value also gradually increase in accordance with the clutch transmission torque limit value that increases as the clutch differential rotation ΔN decreases. Then, when they coincide with the required engine torque at time t1, the values are set to the required engine torque thereafter.

  As a result, the required engine torque of the driver can be generated as much as possible, and a large acceleration can be obtained while preventing the start clutch CL1 from deteriorating.

  FIG. 8 is a time chart showing characteristics in the normal start mode in a vehicle to which the control device of the first embodiment is applied. FIG. 8A shows the characteristics of the engine speed, the primary speed, and the vehicle speed. (B) shows the characteristics of the clutch transmission torque limit value / clutch transmission torque command value, and (c) shows the characteristics of the clutch transmission torque limit value / engine torque command value.

  In this normal start mode, the gear ratio of the continuously variable transmission CVT at the time of stopping is lower than the start threshold β, so that it is possible to secure the driving force required at the start and the vehicle speed increases at a predetermined gradient. . Therefore, the time until the start clutch CL1 is completely engaged does not increase, and the clutch temperature of the start clutch CL1 does not rise more than necessary. In FIG. 8 (a), ΔN is the clutch differential rotation.

  Therefore, the clutch transmission torque limit value is set to the maximum torque that can be generated in the starting clutch CL1, and the clutch transmission torque command value and the engine torque command value are not substantially limited. As a result, the clutch transmission torque command value and the engine torque command value can be set in accordance with the required engine torque, and the driver's required engine torque can be generated immediately after starting to obtain a large acceleration. For this reason, the fall of acceleration property can be prevented.

  Further, in the vehicle drive system friction element control device of the first embodiment, in step S17, the clutch transmission torque limit value of the start clutch CL1 is obtained by dividing the clutch differential rotation ΔN from the clutch heat dissipation power. Based on the clutch transmission torque limit value thus obtained, a clutch transmission torque command value for the start clutch CL1 is set in step S19.

  As a result, the clutch transmission torque limit value can be easily obtained, and control processing in a short time becomes possible.

Next, the effect will be described.
In the control apparatus for an electric vehicle according to the first embodiment, the following effects can be obtained.

(1) Friction element control unit for slip-engaging a friction element (starting clutch CL1) that is arranged between the vehicle drive source (engine Eng) and the drive wheels (left and right drive wheels LT, RT) and that connects and disconnects torque transmission ( 4), the friction element control unit (FIG. 4) includes clutch heat radiation power calculating means (step S11) for obtaining the maximum energy that can be absorbed by the friction element CL1. Clutch absorption power calculation means (step S12) for obtaining the energy absorbed by the friction element CL1 during slip engagement, and differential rotation calculation means (step S2) for obtaining the clutch differential rotation ΔN during slip engagement of the friction element. And the frictional element CL1 is capable of absorbing the frictional element CL1 so that the maximum energy that can be absorbed by the frictional element CL1 and the energy absorbed by the frictional element CL1 coincide with each other. An upper limit value (clutch transmission torque limit value) of the transmission torque by the element CL1 is set, and the upper limit value (clutch transmission torque limit value) is increased as the clutch differential rotation ΔN is smaller.
For this reason, it is possible to achieve both improvement in the durability of the friction element CL1 and improvement in the acceleration performance of the vehicle.

(2) A continuously variable transmission CVT is disposed between the friction element (starting clutch CL1) and the driving wheels (left and right driving wheels LT, RT), and a transmission ratio for obtaining a transmission ratio of the continuously variable transmission CVT. The friction element control unit (FIG. 4) has a calculation means (step S9), and the friction element CL1 absorbs the maximum energy (clutch heat radiation) that can be absorbed by the friction element CL1 based on the gear ratio of the continuously variable transmission CVT when the vehicle is stopped. Control for determining whether or not to set the upper limit value (clutch transmission torque limit value) of the torque transmitted by the friction element CL1 so that the energy absorbed by the friction element CL1 (clutch absorption power) matches. The mode judgment means (step S10) is provided.
For this reason, the clutch transmission torque command value and the engine torque command value are limited according to the gear ratio of the continuously variable transmission CVT when the vehicle is stopped. The fall of property can be prevented. Moreover, even if a restriction is necessary, the greatest possible acceleration can be obtained.

(3) The friction element control unit (FIG. 4) is configured so that the maximum energy (clutch heat dissipation) that the friction element CL1 can absorb the upper limit value (clutch transmission torque limit value) of the transmission torque by the friction element (starting clutch CL1). (Power) is obtained by dividing the differential rotation ΔN, and the transmission torque command value of the friction element CL1 is set based on the upper limit value (clutch transmission torque limit value).
For this reason, the clutch transmission torque limit value can be easily obtained, and control processing in a short time becomes possible.

  As mentioned above, although the control apparatus of the drive-system friction element for vehicles of this invention has been demonstrated based on Example 1, it is not restricted to this Example 1 about a concrete structure, Each claim of a claim Design changes and additions are permitted without departing from the spirit of the invention according to the paragraph.

  In the first embodiment, the start clutch CL1 disposed between the engine Eng and the continuously variable transmission CVT is used as the friction element. However, an example of using a clutch provided between the continuously variable transmission CVT and the left and right drive wheels LT, RT as a friction element, or a stepped automatic transmission instead of the continuously variable transmission CVT is provided. Examples include diverting clutches and brakes built into automatic gear transmissions. That is, the friction element may be arranged in the vehicle drive system and slip-fastened when the fastening is released.

  In Example 1, the example which uses a belt-type continuously variable transmission as the continuously variable transmission CVT was shown. However, any automatic transmission that can change the gear ratio steplessly may be used.

  In the first embodiment, an application example to a so-called engine vehicle having only the engine Eng as a drive source has been shown. However, the present invention can also be applied to a hybrid vehicle that uses both an engine and a motor as a drive source, an electric vehicle that uses only a motor as a drive source, a fuel cell vehicle, and the like.

Eng engine
CL1 Starting clutch (friction element)
CVT continuously variable transmission
LT Left drive wheel
RT Right drive wheel 1 Integrated controller

Claims (3)

In a vehicle drive system friction element control device including a friction element control unit that slips and fastens a friction element that is arranged between a drive source and a drive wheel of a vehicle and connects and disconnects torque transmission,
The friction element control unit includes a clutch heat dissipation power calculation means for obtaining maximum energy that can be absorbed by the friction element, a clutch absorption power calculation means for obtaining energy absorbed by the friction element during slip engagement, and slip engagement of the friction element. Differential rotation calculation means for obtaining a differential rotation at the time,
The upper limit value of the torque transmitted by the friction element is set so that the maximum energy that can be absorbed by the friction element coincides with the energy that the friction element absorbs when the friction element slips, and the differential rotation is small. The vehicle drive system friction element control device is characterized in that the upper limit value is increased. In the control device for a vehicle drive system friction element according to claim 1,
A continuously variable transmission is disposed between the friction element and the drive wheel, and has a gear ratio calculating means for obtaining a gear ratio of the continuously variable transmission,
The friction element control unit uses the friction element so that the maximum energy that can be absorbed by the friction element matches the energy that the friction element absorbs based on the gear ratio of the continuously variable transmission when the vehicle is stopped. A control device for a vehicle drive system friction element, comprising control mode determination means for determining whether or not to set an upper limit value of a transmission torque. In the vehicle drive system friction element control device according to claim 1 or 2,
The friction element control unit obtains an upper limit value of the transmission torque by the friction element by dividing the differential rotation from the maximum energy that can be absorbed by the friction element, and based on the upper limit value, a transmission torque command of the friction element A control device for a vehicle drive system friction element, wherein a value is set.

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