JPH02176263A - Speed change control device for automatic transmission - Google Patents

Abstract

PURPOSE:To reduce a speed change shock in a kickdown control area by providing an operating condition detecting means of engine torque and a means less controlling an offset amount to a high car speed side of a speed change line in specific operation condition time. CONSTITUTION:A control means 8 inputs an engine load signal in accordance with opening of a throttle valve 13 from an engine load sensor 14, car speed signal from a car speed sensor 15 provided in a torque converter 3 and an operative condition signal from an atmospheric air sensor 16 in an operative condition detecting means. A speed change line is set to a low car speed side in highland operation time (specific operation condition), obtaining a line pressure in a low pressure side. In this way, a speed change shock in a kickdown control area can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a shift control device for an automatic transmission.

(Prior Art) Generally, an automatic transmission is composed of a torque converter and a speed change gear mechanism, and a desired gear position can be obtained by a combination of each fastening element of the speed change gear mechanism. Further, each engagement element of this transmission gear mechanism is actuated by a hydraulic actuator, and the engagement pressure thereof is defined by transmission control hydraulic pressure (hereinafter referred to as line pressure) supplied to each actuator. This line pressure is normally set to a predetermined constant pressure that can transmit the maximum torque generated at each load throughout the entire load range of the engine (see, for example, the line PL in FIG. 7).

Furthermore, the shift control of this automatic transmission is controlled based on a shift line that is set in advance based on the engine load (i.e., throttle opening) and vehicle speed. In order to improve the performance, the shift line in the high load area is set to a high vehicle speed so that kickdown control is executed in which the gear is downshifted by at least one gear during acceleration in the high load area where the engine load is above a predetermined value. Generally, it is offset to the side.

On the other hand, the engine torque changes with the engine load, that is, the engine throttle opening, and the engine speed, and the state of the change is, for example, in the low and medium speed range as shown by the diagram TL in Fig. 7. The torque changes in a curve that reaches the highest torque and then rapidly decreases as the rotation speed increases.

However, this torque characteristic is not constant, and if we consider, for example, when driving a vehicle at low altitudes and when driving at high altitudes, we find that the torque characteristic at a predetermined throttle opening at low altitudes, for example, when driving at full throttle, is In the case of the diagram TL in the figure, when driving at high altitudes, the atmospheric pressure is lower than at low altitudes, and the amount of intake air charged into the engine is lower, so for example, as shown in the diagram TH in Figure 6, Torque value decreases overall.

In this case, for example, if the above-mentioned line pressure is kept constant at the line pressure during low-altitude operation (diagram PL in Figure 6), the difference between the line pressure and engine torque during high-altitude operation will be the same as that during low-altitude operation. In the friction elements of the automatic transmission, the engagement force becomes excessive compared to the engine torque, causing the engagement to occur suddenly, resulting in a problem in which a large shift shock occurs. Such a shift shock is noticeable in a kickdown control range where the absolute value of the engine generated torque is large and the shift occurs in a high engine speed range.

In order to alleviate the shift shock that occurs due to changes in engine torque due to changes in the engine operating environment, it is necessary to reduce the difference between the line pressure (i.e., the coupling horn of the friction element of the automatic transmission) and the engine torque. All you have to do is make it smaller,
From this point of view, for example, the line pressure during high-altitude operation can be adjusted to a constant pressure compared to the line pressure during low-altitude operation (diagram PL) in response to the decrease in engine torque, as shown by the line P o in Figure 6. This reduces the difference between line pressure and engine torque when driving at high altitudes to the same level as when driving at low altitudes.

Furthermore, Japanese Patent Application Laid-Open No. 60-23662 discloses a system in which the shift line of the automatic transmission is changed from the one used when driving at low altitudes to the high vehicle speed side when driving at high altitudes, thereby improving acceleration performance when driving at high altitudes. ing.

(Problem to be Solved by the Invention) In this way, by lowering the line pressure for shift control when driving at high altitudes than when driving at low altitudes, it is possible to alleviate the shift shock of the automatic transmission when driving at high altitudes. However, if the engine torque changes between driving at high altitudes and driving at low altitudes, the following problems occur. That is, as shown in FIG. 6, when the line pressure P o during high-altitude operation is lowered than the line pressure PL during low-altitude operation, the ratio of engine torque b to line pressure a during low-altitude operation at a predetermined engine speed is On the other hand, the ratio of engine torque d to line pressure C during high-altitude operation is smaller,
This tendency becomes more pronounced as the engine speed increases. For this reason, as a countermeasure against shift shock in the kickdown control range, when driving at high altitudes, even if the line pressure is lower than when driving at low altitudes, the absolute amount of torque generated by the engine is high, and since the shift occurs at high engine speed, the engine torque and line pressure are There will be a difference between the pressure and the shift shock will still remain, so other effective measures are required.

Although it is theoretically conceivable to match the line pressure PLPl to the shape of the engine torques T L and TH in order to eliminate the above problem, it is extremely difficult in practice.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a shift control device for an automatic transmission that can reduce shift shock in a kickdown control range under operating conditions in which engine torque decreases throughout the entire load range by a simpler means. It was done for a purpose.

(Means for Solving the Problems) In the present invention, as a means for solving such problems, the speed change is controlled based on a speed change line that is set according to the engine load and the vehicle speed, and the engine load is controlled to a predetermined value. In the above range, in an automatic transmission in which the shift line is offset to the high vehicle speed side and kickdown control is performed, a specific driving state in which the engine torque is lower than that during steady operation throughout the entire load range is detected. a driving state detecting means; and a control means for setting an offset amount of the shift line toward a higher vehicle speed to be smaller when a specific driving state is detected by the driving state detecting means than when the said state is not detected. It is characterized by the fact that it is equipped with

(Function) In the present invention, with such a configuration, in the kickdown control range under specific driving conditions where the engine torque decreases throughout the entire load range, the shift line is shifted to the lower vehicle speed side than that during steady driving. Since the gear shift is shifted to , the shift is performed at a relatively low engine speed with little drop in torque in the kickdown control region, so the difference with the line pressure can be effectively reduced and shift shock can be alleviated.

Note that if this is combined with control to lower the line pressure, the shift shock can be more effectively alleviated due to the synergistic effect.

(Effects of the Invention) Therefore, according to the automatic transmission shift control device of the present invention,
This is because the shift operation during kickdown control under specific driving conditions is performed under conditions where the difference between the engine torque and the shift control line pressure, that is, the engagement force of the friction element of the automatic transmission, is as small as possible. , it is possible to obtain the effect that the shock accompanying gear shifting is more effectively reduced.

In addition, because the shift line is shifted to the low vehicle speed side only during kickdown control where the shift shock is more pronounced under specific driving conditions, the shift line is shifted to the low vehicle speed side, so even though the engine torque is reduced, the shift line is shifted to the low vehicle speed side. By changing gears within the vehicle speed range, it is possible to prevent the driving force from decreasing and the driving performance to deteriorate.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 1 to 6.

FIG. 1 shows a power unit Z for an automobile with an automatic transmission equipped with a speed change control device according to an embodiment of the present invention. The engine torque output from the engine is transmitted to the transmission gear device 4 via the torque converter 3, and after being shifted by the transmission gear device 4 at a predetermined gear ratio. ,
It is transmitted from the output shaft 5 to the wheels.

The speed change gear device 4 has a known structure, and is composed of a plurality of transmission gear mechanisms (not shown) and a plurality of friction elements (not shown), and each of the friction elements is selectively operated by a fluid actuator 7. The gear shift switching means 6 is adapted to obtain a predetermined gear stage by operating the friction elements to suitably change the combination of these friction elements. and,
The speed change control of the speed change gear device 4 is carried out by controlling the fluid actuator 7 using electromagnetic means 9 which operates in response to a control signal outputted from the control means 8. This is done by performing switching control based on a speed change pattern set as follows. Further, the control of the engagement force of each friction element of the speed change switching means 6 is controlled by the hydraulic pressure supplied to the fluid actuator 7.
That is, this is done by adjusting the line pressure using the line pressure control means 10. Note that this line pressure control means 1
0 can be arbitrarily set by controlling the duty of a constant pressure valve provided in the discharge line of a hydraulic pump using a duty solenoid valve, as is conventionally known (for example, see Japanese Patent Application Laid-Open No. 62-246652). There is. The duty rate of this duty solenoid valve is set by the control means 8.

The control means 8 also includes an engine load sensor 1 as a control element for performing speed change control and line pressure control.
4 to an engine load signal corresponding to the opening degree of the throttle valve 13, and a vehicle speed sensor 1 provided in the torque converter 3.
A vehicle speed signal corresponding to the turbine rotation speed is inputted from the engine 5, and an engine operation signal corresponding to the atmospheric pressure is inputted from the atmospheric pressure sensor 16, respectively. This atmospheric pressure sensor 16 corresponds to the driving state detecting means in the claims, and detects the current driving state of the vehicle from the atmospheric pressure, specifically, the current atmospheric pressure as described below. Depending on whether the value is higher or lower than the set value, it is determined whether the vehicle is currently in a high-altitude driving state or a low-altitude driving state. Based on this discrimination signal, line pressure control and shift line shift control are performed as described later.

Next, a method of controlling the speed change gear device 4 will be specifically explained with reference to FIGS. If dedicated line pressure is set and kickdown control is performed during steady-state operation) and high-altitude operation (during specific operating conditions in the scope of claims), the Dedicated shift lines have been set up, and these are used differently for each driving operation. Specifically, regarding the shift lines, a first shift pattern shown in FIG. 2 is set as a shift pattern for low-altitude driving, and a second shift pattern shown in FIG. 3 is set as a shift pattern for high-altitude driving. Both of these two shift patterns have a kickdown control region in which the shift line is shifted to the high vehicle speed side in a high throttle opening range (high load range). In this embodiment, the 2-3 shift line and the 3-4 shift line are both shift patterns and have the same characteristics, but for the I-2 shift line, the shift line in the kickdown region is set better during high-altitude driving. The vehicle speed is lower than that when driving in lowlands (1st shift pattern 1 → 2 kickdown vehicle speed ■ 1 > 2nd shift pattern 1-2 kickdown vehicle speed Vt), and the characteristics are the same in the lower load region than the kickdown region. It is set so that

To explain this shift control in more detail based on the flowchart shown in FIG. 5, first, the current vehicle speed, throttle opening, and atmospheric pressure signal are read (step R). Then, depending on whether the atmospheric pressure is higher or lower than a set value, it is determined whether the vehicle is currently being driven at a high altitude or a low altitude (step R3). As a result of this determination, if the atmospheric pressure is higher than the set value, that is, if you are driving at a low altitude, the shift pattern should be set to the first shift pattern. In other words, when driving at a high altitude, the shift pattern is set to the second shift pattern (step R5), and a control signal is output to the electromagnetic means 9 (see FIG. 1) to determine the current operating state. Shift control of the automatic transmission 2 is performed according to a shift pattern corresponding to the shift pattern.

As a result, when driving at high altitudes and in the kickdown control area, the gear shift is performed at a lower vehicle speed, that is, at a higher engine torque side, than when driving at low altitudes and in the kickdown control area.

On the other hand, regarding line pressure control, as shown in Fig. 7, the line pressure is set according to the engine load, and as shown in Fig. 6, the line pressure is set in upper and lower stages (diagram PL , PI(), and when operating at high altitude, the line pressure on the low pressure side PH is adopted, and when operating at low altitude, the line pressure on the high pressure side PL is adopted. That is, as shown in Fig. 4, after starting the control, first the current atmospheric pressure and throttle opening are read (
Then, the current operating state of the vehicle is determined from these two signals, and line pressures corresponding to the respective operating states are set. (See Figure 1).

By performing the shift control and line pressure control in this manner, the difference between the line pressure (i.e., the engagement force of the friction element of the automatic transmission 2) and the engine torque is large, and a large shift shock is likely to occur. Even when driving at high altitudes and in the kickdown control region, the synergistic effect of setting the line pressure to the low pressure side and shifting the transmission line to the low speed side (i.e., an increase in engine torque) reduces the engagement force of the friction element and the engine. The difference in torque is reduced as much as possible, and the shift shock is effectively reduced accordingly.

In this embodiment, of the three shift lines, 1-2
Although only the gear shift line is shifted to the low speed side when driving at high altitudes, the present invention is not limited to this. For example, the 2-3 gear shift line and the 3-4 gear shift line are also shifted to the low speed side when driving at high altitudes. It can also be migrated.

[Brief Description of the Drawings] Fig. 1 is a system diagram of an automobile power plant equipped with a shift control device for an automatic transmission according to an embodiment of the present invention;
3 and 3 are shift pattern diagrams of the automatic transmission shown in FIG. 1, FIGS. 4 and 5 are control flowcharts, and FIG. 6 is a comparison of line pressure during high-altitude operation and low-altitude operation. FIG. 7 is a correlation characteristic diagram between engine torque and line pressure with respect to engine load. ■...Engine 2...Automatic transmission 3...Torque converter 4...Transmission gear device Fig. 2 (Second shift pattern: when driving at high altitude) Fig. 3 Figure 6 71m

Claims (1)

[Claims] 1. Automatic gear shifting is controlled based on a gear shifting line set according to the engine load and vehicle speed, and when the engine load is above a predetermined value, the gear shifting line is offset to the high vehicle speed side and kickdown control is performed. The machine includes an operating state detection means for detecting a specific operating state in which the engine torque is lower than that during steady operation throughout the entire load range, and when the specific operating state is detected by the operating state detection means, the operating state detecting means detects the specific operating state. A shift control device for an automatic transmission, comprising: control means for setting an offset amount of the shift line toward a higher vehicle speed to be smaller than when the state is not detected.