JP2004301230A - Slip detecting device for continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slip detecting device for a continuously variable transmission capable of correctly detecting slip of a continuously variable transmission. <P>SOLUTION: This slip detecting device is provided for a continuously variable transmission, in which the speed change ratio can be continuously variably changed. It is provided with an absolute value determining means (step S4) to determine an absolute value for a value obtained by comparing an actual value and a theoretical value related to the speed change ratio, and a slip determining means (step S4) to determine generation of slip based on the absolute value obtained by the absolute value determining means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for detecting slippage of a continuously variable transmission capable of continuously changing a gear ratio.
[0002]
[Prior art]
Conventionally, as a continuously variable transmission capable of continuously changing the gear ratio, by changing the groove width of the pulley around which the belt is wound, the belt winding radius with respect to the driving pulley and the driven pulley is continuously changed. And those in which the speed ratio is continuously changed by tilting a roller sandwiched between the disks on the input side and the output side. In these continuously variable transmissions, torque is transmitted using a frictional force generated between a belt and a pulley and a shearing force of an oil film interposed between a disk and a roller. Limited by forces and shear forces. Therefore, when a torque greater than the transmission torque capacity acts on the continuously variable transmission, slippage occurs between the belt and the pulley or between the disk and the roller.
[0003]
When excessive slippage occurs in the continuously variable transmission, there is a possibility that a torque transmission surface of a pulley, a disk, or the like may be damaged by wear or adhesion. Therefore, in order to avoid this kind of inconvenience, it is conceivable to increase the transmission torque capacity by increasing the clamping pressure for clamping the belt or the roller. However, when the clamping pressure is increased, the power transmission efficiency decreases, and for example, in a vehicle, the advantage of using a continuously variable transmission is impaired.
[0004]
Therefore, in the invention described in Patent Document 1, for a belt-type continuously variable transmission, the actual speed ratio is calculated based on the input speed and the output speed, and the change rate of the actual speed ratio is calculated. On the other hand, based on the speed ratio, the engine speed, the throttle opening, and the control amount of the speed change control valve, a theoretical speed change rate is obtained, and the actual speed ratio change rate is calculated as the theoretical speed change rate. It is configured to determine the occurrence of slip when the value is larger than the value.
[0005]
[Patent Document 1]
JP-A-6-11022 (paragraph (0129), FIGS. 6 to 12)
[0006]
[Problems to be solved by the invention]
In the invention described in Patent Literature 1, the slip is determined when the actual speed ratio change rate is greater than the theoretical speed change rate, but there are various modes in which slip occurs in the continuously variable transmission. When the continuously variable transmission slips, for example, when the accelerator pedal is depressed greatly to accelerate, the rotational speed of the input side member such as the drive pulley rapidly increases, and the speed ratio changes in the downshift direction. The slip ratio can be detected by the invention described in Patent Document 1 described above, but when the continuously variable transmission slips during engine braking or regenerative braking in a hybrid vehicle, the slip on the input side is reduced. The rotation speed of the rotating member decreases, and the speed ratio changes in the upshift direction, and the change becomes slow. That is, in such a slip at the time of deceleration, the actual speed ratio change rate does not always increase. Therefore, in the invention described in Patent Document 1 described above, the slip of the continuously variable transmission cannot always be detected accurately.
[0007]
Also, when supplying and discharging pressure oil so as to achieve a gear ratio based on a speed change command, the supply and discharge amount of pressure oil may vary from an assumed amount, and the response delay of hydraulic control may be a factor. As a result, the flow rate may vary. Furthermore, since pressure oil leakage may occur, the flow rate of the pressure oil in response to the shift command may not be uniquely determined. As a result, due to these error factors, the actual transmission ratio change rate and the theoretical A simple comparison between the speed ratio change rate and the slip ratio of the continuously variable transmission may not be accurately detected.
[0008]
The present invention has been made in view of the technical problem described above, and has as its object to provide a control device that can accurately detect slippage of a continuously variable transmission based on an actual measurement value and a theoretical value. Is what you do.
[0009]
Means for Solving the Problems and Their Functions
In order to achieve the above object, a first aspect of the present invention is to provide a slip detection device for a continuously variable transmission capable of changing a speed ratio steplessly by comparing an actual measurement value and a theoretical value of the speed ratio. Value detection means for obtaining an absolute value of a value obtained by the method, and slip detection means for determining occurrence of slip based on the absolute value obtained by the absolute value calculation means. Device.
[0010]
Therefore, according to the first aspect of the present invention, an actual measured value and a theoretical value of a speed ratio such as a speed ratio and a change ratio of a speed ratio are obtained, and a value based on a comparison between a difference between the actually measured value and the theoretical value and a ratio. Is obtained. Then, occurrence of slip is determined based on the absolute value. Therefore, not only slippage in which the rotation speed on the input side of the continuously variable transmission increases but also slippage in which the rotation speed on the input side decreases are accurately detected.
[0011]
In the invention of claim 2, the absolute value calculating means in the invention of claim 1 includes means for obtaining an absolute value of a difference between an actual speed ratio change rate and a theoretical speed ratio change rate, and the slip determination means The slip is determined based on the comparison result between the absolute value of the difference between the actual gear ratio change rate and the theoretical gear ratio change rate and a predetermined threshold, and if the threshold is different based on the gear ratio. A slip detection device characterized by including means for causing slippage.
[0012]
Therefore, according to the second aspect of the present invention, the absolute value of the difference between the actual speed ratio change rate and the theoretical speed ratio change rate is compared with a predetermined threshold value to determine slippage, and the threshold value is determined as the speed change rate. Different values are set based on the ratio. For example, the threshold value becomes smaller as the gear ratio becomes smaller. As a result, slip determination according to the actual number of slip rotations becomes possible. In other words, a slip whose influence on damage or durability or the like is not less than a certain value is accurately detected regardless of the magnitude of the gear ratio.
[0013]
Further, according to a third aspect of the present invention, in the first or second aspect of the invention, the continuously variable transmission is configured so that a transmission torque capacity changes in accordance with a squeezing force, and the slip determination means determines slip. The slip detecting device is provided with a slip response control means for increasing the clamping pressure in the case where the slip is detected.
[0014]
Therefore, according to the third aspect of the invention, when the occurrence of slippage is determined, the clamping pressure is increased and the transmission torque capacity of the continuously variable transmission is increased. That is, since slippage occurs due to the relatively low clamping force, the slipping is prevented or suppressed by increasing the clamping pressure.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described based on specific examples. First, a description will be given of a drive system and a control system thereof for a vehicle according to the present invention. FIG. 3 schematically shows a drive system including a belt-type continuously variable transmission 1 as a transmission. The machine 1 is connected to a power source 3 via a forward / reverse switching mechanism 2.
[0016]
The power source 3 includes an internal combustion engine, or an internal combustion engine and an electric motor, or an electric motor, and is essentially a driving member that generates motive power for traveling. In the following description, the power source 3 is referred to as an engine 3. Further, the forward / reverse switching mechanism 2 is a mechanism that is employed in accordance with the fact that the rotation direction of the engine 3 is limited to one direction, and outputs the input torque as it is and outputs it in reverse. It is configured as follows.
[0017]
In the example shown in FIG. 3, a double pinion type planetary gear mechanism is employed as the forward / reverse switching mechanism 2. That is, the ring gear 5 is arranged concentrically with the sun gear 4, and a pinion gear 6 meshed with the sun gear 4 and another pinion gear 7 meshed with the pinion gear 6 and the ring gear 5 are arranged between the sun gear 4 and the ring gear 5. The pinion gears 6 and 7 are held by the carrier 8 so as to rotate and revolve. Further, a forward clutch 9 for integrally connecting the two rotating elements (specifically, the sun gear 4 and the carrier 8) is provided, and by selectively fixing the ring gear 5, the direction of the output torque is provided. Reverse brake 10 is provided.
[0018]
The continuously variable transmission 1 has the same configuration as a conventionally known belt-type continuously variable transmission, and each of a drive pulley 11 and a driven pulley 12 arranged in parallel with each other includes a fixed sheave and a hydraulic pulley. A movable sheave that is moved back and forth in the axial direction by actuators 13 and 14. Accordingly, the groove width of each of the pulleys 11 and 12 changes by moving the movable sheave in the axial direction, and accordingly, the winding radius of the belt 15 wound around each of the pulleys 11 and 12 (the effective diameter of the pulleys 11 and 12). ) Changes continuously, and the gear ratio changes steplessly. The drive pulley 11 is connected to a carrier 8 which is an output element of the forward / reverse switching mechanism 2.
[0019]
The hydraulic pressure (line pressure or its correction pressure) according to the torque input to the continuously variable transmission 1 is supplied to the actuator 14 of the driven pulley 12 via a hydraulic pump, a hydraulic control device, and the like (not shown). I have. Therefore, in this embodiment, each sheave of the driven pulley 12 sandwiches the belt 15 to apply tension to the belt 15 and secure a clamping force (contact pressure) between each of the pulleys 11 and 12 and the belt 15. It has become. On the other hand, the actuator 13 of the drive pulley 11 is supplied with pressure oil corresponding to a speed ratio to be set, and is set to a groove width (effective diameter) corresponding to a target speed ratio. The control of the supply and discharge of the pressure oil is performed by controlling a flow control valve (not shown) connected to the actuator 13.
[0020]
The driven pulley 12 is connected to a differential 17 via a gear pair 16, and outputs torque from the differential 17 to driving wheels 18.
[0021]
Various sensors are provided to detect the operation state (running state) of the vehicle equipped with the above-described continuously variable transmission 1 and the engine 3. That is, an engine speed sensor 19 that detects the speed of the engine 3 and outputs a signal, an input speed sensor 20 that detects the speed of the drive pulley 11 and outputs a signal, and detects a speed of the driven pulley 12. An output speed sensor 21 for outputting a signal is provided. Although not particularly shown, an accelerator opening sensor that detects the amount of depression of the accelerator pedal and outputs a signal, a throttle opening sensor that detects the opening of the throttle valve and outputs a signal, and a brake pedal are depressed. A brake sensor or the like that outputs a signal in the case is provided. Further, a hydraulic sensor 24 for detecting the pressure of the hydraulic actuator 14 on the driven pulley 12 side for setting the belt clamping pressure is provided.
[0022]
An electronic control unit for a transmission (CVT-ECU) for controlling the engagement and disengagement of the forward clutch 9 and the reverse brake 10, controlling the clamping force of the belt 15, and controlling the speed ratio. 22 are provided. The electronic control unit 22 is configured mainly by a microcomputer as an example, performs calculations in accordance with a predetermined program based on input data and data stored in advance, and various states such as forward, reverse or neutral, It is configured to execute control such as setting of a required squeezing pressure and setting of a gear ratio.
[0023]
Here, as an example of data (signal) input to the transmission electronic control unit 22, a signal of the input rotation speed Nin of the continuously variable transmission 1 and a signal of the output rotation speed Nout of the continuously variable transmission 1 are shown. Is entered. An engine electronic control unit (E / G-ECU) 23 for controlling the engine 3 outputs a signal of an engine speed Ne, a throttle opening signal, and an accelerator opening which is an amount of depression of an accelerator pedal (not shown). A signal or the like is being input.
[0024]
According to the continuously variable transmission 1, since the engine speed, which is the input speed, can be continuously controlled, the fuel efficiency of a vehicle equipped with the engine speed can be improved. For example, a target driving force is determined based on a required driving amount and a vehicle speed represented by an accelerator opening, and a target output required to obtain the target driving force is determined based on the target driving force and the vehicle speed. The engine speed for obtaining the target output at the optimum fuel efficiency is obtained based on a prepared map, and the gear ratio is controlled so as to become the engine speed.
[0025]
The control device according to the present invention for the above-described continuously variable transmission 1 is configured to detect slippage in the continuously variable transmission 1 and execute control according to the detection result. An example of the control is shown in FIG. 1. First, an inflow / outflow amount Q is calculated based on a shift command value (step S1). As described above, the gear ratio is basically controlled so that the engine 3 is operated at the optimum fuel efficiency. In addition, the gear ratio is controlled to a gear ratio in accordance with an acceleration request or a deceleration request, and further, the gear ratio is controlled. The speed (rate of change in gear ratio) is controlled. Therefore, the gearshift command value takes into account the target gear ratio and the gear speed. For example, the gear ratio to be finally set, or the gear ratio that changes transiently and sequentially after the first-order lag process or the smoothing process for the gear ratio. The ratio is included.
[0026]
Therefore, the supply and discharge of the pressure oil to and from the actuator 13 on the drive pulley 11 side and the flow rate thereof are controlled based on the shift command value. In other words, the shift command value and the flow rate of the pressure oil for controlling the speed ratio are determined in a predetermined relationship according to the configuration of the control device such as the flow rate control valve. Is theoretically obtained based on the shift command value.
[0027]
Next, the theoretical speed ratio change rate Δγs is calculated using the inflow / outflow amount Q calculated in step S1 (step S2). The speed ratio change rate is a change amount of the speed ratio per unit time, and the speed ratio changes according to the amount of pressure oil flowing into or out of the actuator 13 on the drive pulley 11 side. The change rate Δγs can be obtained as the amount of the inflow / outflow amount Q obtained in step S1 per unit time.
[0028]
On the other hand, the actual speed ratio change rate Δγr is calculated (step S3). Although this calculation is described in FIG. 1 as being performed after step S2, it may be performed in parallel with the calculation of the theoretical speed ratio change rate Δγs, and the order is not limited. The actual gear ratio change rate Δγr is, for example, the rotation speed of the driving pulley 11 detected by the input rotation speed sensor 20 and the rotation speed of the driven pulley 12 detected by the output rotation speed sensor 21. Can be obtained as the amount of change per unit time of the ratio. Alternatively, the actual gear ratio change rate Δγr can be obtained as the difference between the gear ratio before a predetermined time and the gear ratio at the current time.
[0029]
Next, it is determined whether or not the absolute value (| Δγs−Δγr |) of the difference between the theoretical gear ratio change rate Δγs and the actual gear ratio change rate Δγr is larger than a predetermined value (that is, a threshold value) (step). S4). Here, the predetermined value is a value that is set to a minimum value that does not cause an erroneous determination in consideration of various variations including a response delay in the inflow / outflow amount Q used when the theoretical speed ratio change rate Δγs is calculated. is there.
[0030]
In addition, slippage in the belt-type continuously variable transmission generally occurs on the pulley side where the belt winding radius is small. Therefore, if the speed ratio immediately before the occurrence of slippage (that is, the initial speed ratio: initial γ) is different, even if the absolute value is the same, the actual slip rotation speed (the difference between the belt speed and the pulley rotation speed) is reduced. ) Will be different. Specifically, assuming that the absolute values are the same, the smaller the speed ratio, the higher the number of slip rotations. Therefore, the predetermined value used in step S4 is set to a smaller value as the initial speed ratio is smaller, as shown in FIG.
[0031]
If slippage occurs in the continuously variable transmission 1 during acceleration, a downshift is instructed based on the acceleration request, and the slippage causes the rotational speed of the drive pulley 11 to increase. The speed ratio change rate Δγr increases. When the continuously variable transmission 1 slips at that time during deceleration, when the continuously variable transmission 1 slips, the rotational speed of the drive pulley 11 decreases, so that the actual speed ratio changes to the upshift side, and The rate of change changes. In either case of these downshifts and upshifts, since the above-described absolute value becomes large, the determination is affirmative in step S4. Conversely, if no slippage has occurred, the absolute value is equal to or less than the predetermined value, and a negative determination is made in step S4.
[0032]
That is, if a positive determination is made in step S4, it is determined that slippage has occurred in the continuously variable transmission 1. Therefore, in this case, a process corresponding to the determination of belt slippage is performed ( Step S5). This process is a process for preventing or suppressing belt slippage, and specifically, a control for increasing the clamping force of the continuously variable transmission 1. In addition to this, it is possible to execute control for temporarily reducing input torque to the continuously variable transmission such as engine torque. On the other hand, if a negative determination is made in step S4, it means that the slip determination of the continuously variable transmission 1 has not been established, and the routine in FIG. 1 is once terminated without performing any particular control.
[0033]
Therefore, according to the slip detection device of the present invention which executes the control shown in FIG. 1, the absolute value of the comparison result between the actually measured value and the theoretical value of the gear ratio, specifically, the actual gear ratio change rate and the theoretical gear ratio change Since slippage is determined based on the absolute value of the difference from the rate, even if the slippage occurs during engine braking or regenerative braking in a hybrid vehicle, and the gear ratio changes in the upshift direction, it is continuously variable. The slip generated in the transmission 1 can be accurately or reliably detected. Also, instead of simply comparing the actual measurement value with the theoretical value, if a configuration is adopted in which a comparison is made with a predetermined threshold value as described above, the variation in hydraulic pressure and response delay are reflected in the threshold value. The slip can be determined more accurately. Further, if the threshold value is set to a different value according to a speed ratio such as an initial speed ratio, a slip determination can be performed in consideration of an actual slip rotation speed or a slip speed which does not appear in the absolute value. Damage to the step transmission 1 and slippage of a certain degree or more with respect to durability can be detected.
[0034]
Here, the relationship between the above specific example and the present invention will be briefly described. The functional means in step S4 shown in FIG. 1 corresponds to the absolute value calculating means and the slip determining means in the present invention, and The functional means corresponds to the slip control means in the present invention.
[0035]
The continuously variable transmission targeted by the present invention is not limited to the belt-type continuously variable transmission shown in FIG. 3, and may be a traction-type continuously variable transmission. Further, the measured value and the theoretical value related to the speed ratio in the present invention may be a speed ratio other than the above-described speed ratio change rate.
[0036]
【The invention's effect】
As described above, according to the first aspect of the present invention, the occurrence of slippage is determined based on the absolute value of a value obtained by comparing a difference between a measured value and a theoretical value, such as a speed ratio or a speed ratio change rate, and a theoretical value, or a ratio. Therefore, it is possible to individually detect slips in different modes in various driving states, such as slips in which the input-side rotational speed of the continuously variable transmission increases, as well as slips in which the input-side rotational speed decreases. it can.
[0037]
According to the second aspect of the present invention, the absolute value of the difference between the actual gear ratio change rate and the theoretical gear ratio change rate is compared with a predetermined threshold value, and the threshold value is used as the gear ratio. Because different values are set based on the actual slip speed, slip judgment can be made according to the actual slip rotation speed.In addition, slip with a certain effect on damage or durability can be accurately detected regardless of the gear ratio. Can be detected.
[0038]
Further, according to the third aspect of the invention, when the occurrence of slip is determined, the clamping pressure is increased and the transmission torque capacity of the continuously variable transmission is increased. Damage to the machine and reduction in durability can be prevented.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating an example of control by a slip detection device according to the present invention.
FIG. 2 is a diagram conceptually showing a relationship between a threshold value for determining slip and an initial speed ratio immediately before the start of slip.
FIG. 3 is a diagram schematically showing a drive system including a continuously variable transmission targeted by the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Continuously variable transmission, 11 ... Drive pulley, 12 ... Driven pulley, 15 ... Belt, 18 ... Drive wheel, 22 ... Transmission electronic control unit (CVT-ECU).

Claims (3)

In a slip detection device of a continuously variable transmission capable of changing a speed ratio steplessly,
Absolute value calculating means for calculating an absolute value of a value obtained by comparing an actual measurement value and a theoretical value of the speed ratio,
And a slip determining means for determining occurrence of slip based on the absolute value obtained by the absolute value calculating means. The absolute value calculating means includes means for calculating an absolute value of a difference between the actual speed ratio change rate and the theoretical speed ratio change rate,
The slip determining means determines slip based on a comparison result between an absolute value of a difference between the actual speed ratio change rate and the theoretical speed ratio change rate and a predetermined threshold value, and sets the threshold value to a speed change. 2. The slip detecting device for a continuously variable transmission according to claim 1, further comprising means for making the ratio different based on the ratio. The continuously variable transmission is configured such that the transmission torque capacity changes in accordance with the squeezing pressure, and a slip response control means for increasing the squeezing pressure when the slip is determined by the slip determination means is provided. The slip detection device for a continuously variable transmission according to claim 1 or 2, wherein

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