JP2004125015A - Hydraulic pressure control device for belt type continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the generation of overshoot of a secondary pressure in transition for changing a change gear ratio in steps, for example, in quickly pushing the pedal. <P>SOLUTION: A target secondary pressure Tsec corresponding to the torque capacity in a target change gear ratio on the basis of the change of a throttle opening TVO is raised in steps, and an actual hydraulic pressure estimated target value PSsec with time constant of primary delay based on an engine rotating speed as a parameter, is determined as a target in a process to the target secondary pressure, to perform the feedback control, when the difference between PTsec and the actual secondary pressure Prsec is more than a specific value. As the PSsec approximately meets the actual secondary pressure Prsec, and the deviation therebetween is small, the overshoot of the hydraulic pressure by the accumulation of deviation can be prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydraulic control device for a belt-type continuously variable transmission for a vehicle.
[0002]
[Prior art]
Conventionally, as an automatic transmission mounted on a vehicle, there is a V-belt type continuously variable transmission (hereinafter, belt CVT). In this belt CVT, a V-belt is stretched between a primary pulley and a secondary pulley whose groove width is variably controlled based on hydraulic pressure to form a transmission mechanism, and power is transmitted by a contact friction force of the V-belt held between the pulleys. We are communicating.
The primary pulley and the secondary pulley are supplied with the hydraulic pressure adjusted by using the line pressure as the original pressure. During shifting, the relative balance of the hydraulic pressure (primary pressure) to the primary pulley with respect to the hydraulic pressure (secondary pressure) to the secondary pulley. Is changed, the groove width of the primary pulley is changed, and the pulley ratio is changed. In addition, a select lever is provided to enable selection of a plurality of range positions such as a D range for normal running, an engine brake and an L range for obtaining a high driving force at medium to low speeds. Is changed on the basis of the speed ratio. A similar V-belt type continuously variable transmission is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-217712.
[0003]
[Problems to be solved by the invention]
In such a belt CVT, when the input torque from the engine increases during operation, the contact friction force is increased to prevent slippage between the V-belt and the pulley and to transmit the torque reliably. The secondary pressure is also increased to increase the torque capacity.
In particular, when the speed ratio is changed stepwise by sudden depression of the accelerator pedal, the secondary pressure also rises in a stepwise manner.
[0004]
However, as shown in FIG. 4, in response to the step-like rise of the throttle opening TVO due to the depression of the accelerator pedal, the hydraulic pressure instruction value PT of the secondary pressure is changed to a value for obtaining the necessary torque capacity at the target gear ratio. Even if it rises, the actual secondary pressure Prsec does not rise according to the hydraulic pressure instruction value PT. When the secondary pressure hydraulic sensor detects the actual secondary pressure Prsec and performs feedback control in this transient state, the deviation s between the hydraulic pressure instruction value PT and the actual secondary pressure Prsec is accumulated on the hydraulic pressure increasing side, and as a result, the hydraulic pressure instruction value PT Overshoot A of the hydraulic pressure exceeding.
Such a phenomenon occurs not only when the accelerator pedal is suddenly depressed but also when the gear ratio is changed stepwise, for example, when switching from the D range to the L range.
If the overshoot exceeds the strength of the V-belt, the V-belt may be damaged.
[0005]
Therefore, in view of the above-mentioned conventional problems, the present invention provides a hydraulic control device for a belt-type continuously variable transmission that prevents an overshoot of hydraulic pressure from occurring in a transient state in which the gear ratio changes stepwise, such as when suddenly stepping on. The purpose is to provide.
[0006]
[Means for Solving the Problems]
Therefore, the present invention provides a transmission mechanism in which a belt is stretched between a primary pulley and a secondary pulley, a contact friction force for transmitting power between the belt and each pulley, and a hydraulic pressure to the primary pulley for controlling a gear ratio. In a belt-type continuously variable transmission having control means for controlling hydraulic pressure to a secondary pulley, the control means calculates a target secondary pressure calculation unit that calculates a target secondary pressure corresponding to an input torque or a target gear ratio; An actual oil pressure estimation target value setting unit that sets an actual oil pressure estimation target value substantially in line with the course of the actual secondary pressure up to the target secondary pressure, and feeds back oil pressure to the secondary pulley based on the actual oil pressure estimation target value. It was controlled.
[0007]
【The invention's effect】
According to the present invention, the actual hydraulic pressure estimation target value is set substantially in accordance with the course of the actual secondary pressure up to the attained target secondary pressure corresponding to the input torque or the target gear ratio, and the secondary hydraulic pressure is set based on the actual hydraulic pressure estimation target value. Since the hydraulic pressure to the pulley is feedback-controlled, unlike the case where feedback control is performed based on the target secondary pressure that rises stepwise in response to, for example, sudden depression of the accelerator pedal, the secondary pressure is accumulated by accumulating the deviation. Does not overshoot the secondary pressure. Therefore, it is possible to prevent the hydraulic pressure from exceeding the belt strength and causing the damage.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a block diagram showing a system configuration according to the embodiment.
The belt CVT 2 includes a torque converter 3 having a lock-up clutch 4 and a transmission mechanism 5 having a forward / reverse switching mechanism (not shown), and is connected to the engine 1. The transmission mechanism 5 includes a primary pulley 10 on the input shaft side and a secondary pulley 11 connected to the output shaft 13 as a pair of variable pulleys. The pair of variable pulleys 10 and 11 are connected by a V-belt 12.
[0009]
The primary pulley 10 of the transmission mechanism 5 is disposed at a position facing the fixed conical plate 10b, which rotates integrally with the input shaft, and the V-shaped pulley groove. It comprises a movable conical plate 10a that can be displaced in the axial direction according to the hydraulic pressure acting on the cylinder chamber 10c (hereinafter, primary pressure Ppri).
The secondary pulley 11 is disposed at a position facing the fixed conical plate 11b that rotates integrally with the output shaft 13 and the fixed conical plate 11b to form a V-shaped pulley groove, and to the secondary pulley cylinder chamber 11c. It is composed of a movable conical plate 11a that can be displaced in the axial direction according to the hydraulic pressure that acts (hereinafter, secondary pressure Psec).
[0010]
The transmission mechanism 5 is controlled by the hydraulic control unit 30 based on a command from the CVT control unit 20. The hydraulic control unit 30 regulates the hydraulic pressure from a hydraulic pump (not shown) by an internal hydraulic control valve (not shown).
In other words, the secondary pressure Psec adjusted using the line pressure as the original pressure is always supplied to the secondary pulley cylinder chamber 11c, and the primary pressure Ppri similarly adjusted using the line pressure as the original pressure is supplied to the primary pulley cylinder chamber 10c. .
[0011]
The primary pressure Ppri applied to the primary pulley cylinder chamber 10c is controlled to change the groove width of the primary pulley 10, while the secondary pressure Psec is supplied to the secondary pulley cylinder chamber 11c to control the nipping pressure on the V-belt 12 to shift. Is performed, and the driving force is transmitted in accordance with the contact friction force between the V belt 12 and each of the pulleys 10 and 11.
In terms of the number of revolutions, when the groove width of the primary pulley 10 is increased and the contact radius of the V-belt 12 is small and the contact radius of the secondary pulley 11 side is large, the gear ratio becomes large and the engine speed becomes large. The side rotation speed is reduced and output to the axle side. At the reverse pulley ratio Hi, output is at a small gear ratio. During this time, the gear ratio continuously changes according to the contact radius ratio between the primary pulley 10 and the secondary pulley 11.
[0012]
On the other hand, the engine 1 is controlled by the engine control unit 21. The engine control unit 21 is connected to a throttle sensor 24 for detecting an opening of a throttle valve (throttle opening TVO) operated by an accelerator pedal (not shown) and an engine rotation sensor 15.
The engine control unit 21 controls the fuel injection amount and the ignition timing based on the throttle opening TVO from the throttle sensor 24 and the current engine speed Ne from the engine speed sensor 15.
The engine control unit 21 sends to the CVT control unit 20 a throttle opening TV0 during running and an engine torque signal value calculated based on the throttle opening TV0 and the engine speed Ne.
[0013]
The CVT control unit 20 includes a primary pulley speed sensor 26 for detecting an input rotation speed of the primary pulley 10 (primary pulley rotation speed Npri) and a secondary pulley speed for detecting an output rotation speed of the secondary pulley 11 (secondary pulley rotation speed Nsec). The sensor 27 is connected.
Since the output shaft 13 of the secondary pulley 11 is connected to the axle, the vehicle speed Ns can be obtained from the secondary pulley rotation speed Nsec.
[0014]
The CVT control unit 20 has a primary pulley rotation speed Npri determined in advance corresponding to a traveling state represented by a throttle opening TVO and a vehicle speed Ns, in addition to a range position signal from an inhibitor switch 23 attached to a select lever (not shown). A target value is set, and a target gear ratio (target pulley ratio) is determined based on a ratio between the target value and the secondary pulley rotation speed Nsec.
[0015]
The CVT control unit 20 also calculates the thrust (contact friction force) of the primary pulley 10 and the secondary pulley 11 from the input torque information, the gear ratio based on the primary pulley rotation speed Npri and the secondary pulley rotation speed Nsec, and the oil temperature. Is converted to a hydraulic pressure to determine a target value of the line pressure, and a command is sent to the hydraulic control unit 30. Further, a target value of the secondary pressure Psec is determined, and the secondary pressure Psec is controlled by feedback control using a detection value of the secondary pressure hydraulic sensor 33.
[0016]
FIG. 2 is a control block diagram relating to the control of the secondary pressure Psec.
The transmission control unit 40 sets a target transmission ratio based on the throttle opening TVO, the vehicle speed Ns, and the range position.
The arrival target secondary pressure calculation unit 42 receives, from the engine control unit 21, the required torque due to the rapid depression of the accelerator pedal as the input torque information, and receives the target speed ratio from the speed change control unit 40, and calculates the required torque or the target speed ratio. The target secondary pressure PTsec required to secure the corresponding torque capacity is calculated. This attained target secondary pressure PTsec corresponds to the conventional hydraulic pressure instruction value PT.
[0017]
The target value deviation determination unit 44 determines whether the difference between the attained target secondary pressure PTsec and the secondary pressure Psec at the time of setting the target gear ratio is equal to or greater than a predetermined value. When the deviation of the secondary pressure is equal to or more than the predetermined value, the actual hydraulic pressure estimation target value setting unit 46 obtains the hydraulic pressure target in the course of reaching the target secondary pressure PTsec.
[0018]
The actual oil pressure estimation target value setting unit 46 gives a first order time constant with the engine speed as a parameter as the oil pressure target in the course of the course, and sets the actual oil pressure approximately in line with the actual secondary pressure Prsec as shown in FIG. An estimated target value PSsec is set. The actual secondary pressure Prsec indicated by the broken line is the same as that shown in FIG.
FIG. 3 shows a case where the throttle opening TVO changes stepwise due to sudden depression of the accelerator pedal.
[0019]
When the target value deviation determination unit 44 determines that the difference between the attained target secondary pressure PTsec and the actual secondary pressure Prsec is equal to or greater than a predetermined value, the secondary pressure control unit 48 outputs the actual pressure from the secondary pressure hydraulic sensor 33 at unit time intervals. The secondary pressure Prsec is read, and the secondary pressure is feedback-controlled based on the actual hydraulic pressure estimation target value PSsec.
On the other hand, when the target value deviation determination unit 44 determines that the difference between the target secondary pressure PTsec and the actual secondary pressure Prsec is smaller than a predetermined value, the secondary pressure control unit 48 determines the secondary pressure based on the target secondary pressure PTsec. Feedback control.
[0020]
As a result, even if the target value of the secondary pressure is stepped up to the target secondary pressure PTsec in order to secure a required torque capacity against a sudden change in the required torque or the gear ratio, the feedback control is performed in the actual secondary pressure Prsec. Is executed based on the actual hydraulic pressure estimation target value PSsec which is substantially the same as that of the conventional hydraulic pressure instruction value and the actual secondary pressure Prsec. Therefore, the phenomenon that the hydraulic pressure overshoot occurs at the final stage of the feedback control is prevented.
[0021]
The present embodiment is configured as described above, and the actual hydraulic pressure estimation target value PSsec setting unit 46 substantially follows the course of the actual secondary pressure Prsec up to the attained target secondary pressure PTsec corresponding to the required torque or the target gear ratio. Since the hydraulic pressure estimation target value PSsec is set and the hydraulic pressure to the secondary pulley 11 is feedback-controlled based on the target value, it is possible to cope with a step change in the gear ratio caused by sudden depression of the accelerator pedal or range position switching. Even if the attained target secondary pressure PTsec is stepped up, the deviation between the actual feedback target value and the actual secondary pressure Prsec is kept small, so that the secondary pressure Psec can overshoot the attained target secondary pressure PTsec. Absent. Therefore, it is possible to prevent the hydraulic pressure from exceeding the belt strength and causing the damage.
[0022]
The actual oil pressure estimation target value setting section 46 sets the actual oil pressure estimation target value PSsec with a first-order lag time constant using the engine speed as a parameter. It is possible to approach the process of the pressure Prsec.
[0023]
In particular, the feedback control based on the actual hydraulic pressure estimation target value PSsec is performed when the difference between the target secondary pressure PTsec and the actual secondary pressure Prsec is equal to or greater than a predetermined value. Since the hydraulic pressure to the secondary pulley is feedback-controlled based on the pressure PTsec, the setting of the actual hydraulic pressure estimation target value PSsec is limited only when necessary, and the control processing load when there is no possibility of hydraulic overshoot can be reduced.
[0024]
The actual oil pressure estimation target value PSsec in the actual oil pressure estimation target value setting section 46 has a first-order lag time constant with the engine speed Ne as a parameter. In addition to the parameters, the actual hydraulic pressure estimation target value PSsec can be set.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a system configuration according to an embodiment of the present invention.
FIG. 2 is a control block diagram relating to control of a secondary pressure.
FIG. 3 is a diagram showing an actual hydraulic pressure estimation target value.
FIG. 4 is a diagram showing a relationship between a hydraulic pressure instruction value and an actual secondary pressure.
[Explanation of symbols]
1 engine 2 belt CVT
Reference Signs List 3 Torque converter 5 Transmission mechanism unit 10 Primary pulley 10a Movable conical plate 10b Fixed conical plate 10c Primary pulley cylinder chamber 11 Secondary pulley 11a Movable conical plate 11b Fixed conical plate 11c Secondary pulley cylinder chamber 12 V belt 13 Output shaft 15 Engine rotation sensor 20 CVT control unit 21 Engine control unit 24 Throttle sensor 26 Primary pulley speed sensor 27 Secondary pulley speed sensor 23 Inhibitor switch 30 Hydraulic control unit 33 Secondary pressure hydraulic sensor 40 Shift control unit 42 Target secondary pressure calculation unit 44 Target value deviation determination unit 46 Actual oil pressure estimation target value setting unit 48 Secondary pressure control unit

Claims (3)

A transmission mechanism with a belt stretched between the primary pulley and the secondary pulley, and a hydraulic pressure to the primary pulley and a hydraulic pressure to the secondary pulley to control the contact friction force and the gear ratio for power transmission between the belt and each pulley Control means for controlling the belt type continuously variable transmission,
The control means includes:
A target secondary pressure calculation unit that calculates a target secondary pressure corresponding to the input torque or the target gear ratio,
An actual oil pressure estimation target value setting unit that sets an actual oil pressure estimation target value substantially in line with the course of the actual secondary pressure up to the attainment target secondary pressure,
A hydraulic control device for a belt-type continuously variable transmission, wherein feedback control of a hydraulic pressure to a secondary pulley is performed based on the actual hydraulic pressure estimation target value. The belt type according to claim 1, wherein the actual oil pressure estimation target value setting section sets the actual oil pressure estimation target value with a first-order time constant having an engine speed as a parameter. Hydraulic control device for continuously variable transmission. The control means includes:
When the difference between the attained target secondary pressure and the actual secondary pressure is equal to or greater than a predetermined value, performs feedback control based on the actual oil pressure estimation target value,
The belt according to claim 1, wherein when a difference between the target secondary pressure and the actual secondary pressure is smaller than a predetermined value, feedback control of a hydraulic pressure to a secondary pulley is performed based on the target secondary pressure. Hydraulic control device for a continuously variable transmission.

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