JPH0252139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shift control device for reducing shift shock by controlling hydraulic pressure during gear shifting in an automatic transmission equipped with an electronically controlled hydraulic control device.

Hydraulic control devices are often used to automate and control various mechanical devices, but instead of inputting input directly mechanically to control the hydraulic control device, electrical signals are used to control the input. An electronic control method is being considered in which the hydraulic control device is controlled by arithmetic processing using a computer or the like.

For example, in recent years, hydraulic control devices for vehicle automatic transmissions perform delicate hydraulic control depending on driving conditions, and in order to simplify the hydraulic control device,
It electrically detects various signals necessary for automatic gear shifting, such as the amount of accelerator pedal depression, engine speed, vehicle speed, and engine load, and controls the opening and closing of solenoid valves using output signals controlled by a computer, etc. However, an electronically controlled hydraulic control device that performs various hydraulic controls is employed.

Vehicles equipped with the electronically controlled hydraulic control system described above control the hydraulic pressure according to the vehicle's driving conditions, such as the load, so gear changes can be performed more smoothly than with conventional hydraulic control systems. Although things are getting better, there are still some areas that are lacking. In particular, shift shock may occur during power-on upshifts, that is, when shifting while the accelerator is depressed.

Here, a power-on upshift operation from 1st speed to 2nd speed in a vehicle automatic transmission equipped with an electronically controlled hydraulic control device will be explained based on the hydraulic circuit of the electronically controlled hydraulic control device shown in FIG. In this figure, only a part of the rotation circuit is shown.
A shift control valve that supplies each shift valve etc. through the
6 and 7 are shift control solenoid valves that are commanded and operated by a computer 8, and 9 is a pressure reducing valve that controls the duty of the hydraulic pressure supplied through the oil passage 10, that is, the opening/closing time ratio for communicating the oil passage 10 with the oil drain hole 11. Pressure control solenoid valve (hereinafter referred to as PC solenoid valve) that is controlled by changing the
12 is a hydraulic control valve that controls the line pressure from the oil passage 2; 13 is an N-D control valve; and 14 is a 1-2 shift valve, which communicates with the hydraulic control valve 12 through an oil passage 15 and which also communicates with the oil passage 16. , 17 are connected to a brake 18 and a kickdown servo (brake) 19 that is engaged when achieving second gear. 20 is a rear clutch, and 21 is a rear clutch control valve.

In the 1st speed state, the solenoid valves 6 and 7 are conductive (ON), but when the computer 8 issues a 2nd speed command, the current in the solenoid valve 6 changes.
As a result, the oil passage 3 of the shift control valve 1 is connected to the line pressure oil passage 2, the spool 14a of the 1-2 shift valve 14 moves to the right, and the oil passage 15 is connected to the kick-down servo 19. It is opened to the connecting oil passage 17. Then, the line pressure that passes through the oil passage 2 and reaches the hydraulic control valve 12 is pressure-controlled here,
The oil passes through the oil passage 15 to the 1-2 shift valve 14, and is further supplied to the kickdown servo 19 through the oil passage 17, where it is engaged. Note that in order to achieve the second speed, other frictional engagement devices are also attached and detached, but their explanation will be omitted here.

In the above hydraulic circuit, the oil pressure in the oil passage 15 of the 1-2 shift valve 14 is regulated by the oil pressure control valve 12. It is determined in proportion to the oil pressure. Hydraulic pressure in oil passage 15 and
As shown in FIG. 2, there is a relationship between the duty rate of the PC solenoid valve 9 and the hydraulic pressure decreases as the duty rate increases. Therefore, by controlling the duty rate, the hydraulic pressure pattern applied to the kickdown servo 19 can be controlled.

Until now, when power-on upshifts from 1st gear to 2nd gear, the duty rate of the PC solenoid valve 9 has been controlled as shown in FIG. 3. That is, when a shift signal from 1st gear to 2nd gear is issued from the computer 8, the duty rate is first lowered to zero or close to it, the oil pressure in the oil passage 10 is increased (point A in Figure 2), and the kick-down servo is activated. 19 to the initial engagement state (A-B in the figure),
After the initial engagement, increase the duty rate and
The hydraulic pressure is lowered, the frictional engagement elements enter a sliding contact state, and then the duty rate (after point D in the diagram) is lowered at a constant rate and the hydraulic pressure is increased at a constant rate to complete the engagement (Figure middle, point E). In this control method, the duty rate at the time of initial engagement (point B') was changed according to the engine speed and load, but the rate of change in the duty rate after that changed depending on the engine speed and load. It remained constant regardless. In other words, the rate of change α (%/sec) at which the duty rate is lowered and the oil pressure is increased remains constant. However, if this change rate α is constant, the oil pressure change gradient becomes steep at low throttle (low load), and the engagement time (shift time) of the frictional engagement element in the kickdown servo 19 becomes abnormal. If the length becomes too short, a shift shock will occur, and if the oil pressure is reduced, control will be lost.
Also, when the throttle is high (high load), the shift time becomes longer, but if you increase the oil pressure and set the appropriate shift time (about 0.5 seconds) to ensure the durability of the friction material, As shown in FIG. 3, the output shaft torque fluctuation becomes steep, the shift shock becomes large, and the feeling is significantly impaired.

The present invention has been made in view of the above-mentioned situation, and the duty rate of the control hydraulic pressure of the pressure regulating valve that adjusts the hydraulic pressure to the frictional engagement device for the clutch, brake, etc., is adjusted at the initial engagement of the frictional engagement device. but also
The purpose is to control even during engagement, smooth out torque fluctuations during gear shifts, and reduce shift shock.

The gist of the present invention to achieve the above object is to provide a hydraulic pressure source that generates a constant line hydraulic pressure, a hydraulic control valve that regulates the line pressure to a hydraulic pressure below the line pressure, and guides the same as supplied hydraulic pressure to a friction engagement device. and a solenoid valve that is duty-controlled to regulate the hydraulic pressure that controls the hydraulic control valve, and the duty rate is changed at a predetermined rate of change in order to switch the friction element of the friction engagement device from a released state to an engaged state during gear shifting. In an automatic transmission configured to increase the supplied hydraulic pressure, when shifting from a relatively low speed gear to a relatively high speed gear with the accelerator pedal depressed, the friction element engages. When the throttle opening of the engine is relatively small, the rate of change in the duty rate during the process is made gradual, and the hydraulic pressure supplied to the frictional engagement device is gradually increased, and when the throttle opening is relatively large, the rate of change in the duty rate is gradually increased. The present invention resides in a shift control device characterized by comprising a control device that increases the rate of change to rapidly increase the oil pressure supplied to the frictional engagement device.

Hereinafter, a shift control device according to the present invention will be explained based on one embodiment. The embodiment described below shows an example in which the duty rate of the PC solenoid valve 9 is changed depending on two cases: a low throttle opening degree and a high throttle opening degree.

As mentioned earlier, when shifting from 1st to 2nd speed under low load, the duty ratio is reduced and the oil pressure supplied to the friction engagement device (the kickdown servo 19 in the hydraulic circuit shown in Figure 1) is increased. Then, since the transmitted torque is small, the friction element will engage immediately, causing a shift shock. Therefore, when the load is low, if the hydraulic pressure applied to the friction element is lowered, a so-called slipping state will occur, the time required for engagement will become longer, and there will be no shift shock. However, if an attempt is made to reduce the initial engagement oil pressure and then change it to the oil pressure required for final engagement, the oil pressure gradient will become steep because the starting pressure is low, resulting in a shift shock. Therefore, in the present invention, when the load is low, the duty rate at the time of initial engagement is set based on the engine load and engine speed, and even after the initial engagement, the duty rate is changed according to the throttle opening to generate output fluctuation torque. I made it so that it was smooth. This change in duty rate is shown by the dotted line in FIG. Ba' is the time of initial engagement.

Also, when the load is high, the transmitted torque is large, so
If a sliding contact state is created in the friction element and the duty rate is changed at a predetermined change rate α, the shift time will become longer, but if the shift time has an appropriate shift time and is adjusted to the above shift time, the shift time will become longer. , it is necessary to supply high oil pressure (low duty rate in terms of duty rate) to the friction element from the beginning, and in that case, the output shaft torque fluctuation becomes large as shown in FIG. Therefore, in the present invention, when the load is high, the initial engagement oil pressure is lowered, the rise of the oil pressure during engagement is increased, and the duty rate is changed so that the oil pressure can reach a predetermined oil pressure in a predetermined time. be. For example, in the past, when the load was high, the initial engagement pressure had to be maintained at 5 kg/ ^cm2 in order to be able to meet the shift time obtained at a constant gradient. 〜3Kg/cm ² and change rate α
If it is made steep, the output shaft torque fluctuation curve becomes smooth as shown in FIG. In FIG. 4, the change in duty rate under high load is shown by a solid line. B _b ′ is the time of initial engagement.

Next, the above duty control will be explained based on FIG. 5, which is a flowchart showing actual numerical values as an example. The throttle opening voltage is input. The computer determines the state by comparing it with a memory map created in advance, and if the gear is being shifted from 1st to 2nd gear and it is a power-on shift, the throttle opening will be lower than 42%. It is determined whether it is large or small. When the throttle opening is 42% or less, the throttle opening is considered to be in a low throttle opening state, and the duty rate change rate α after initial engagement is set to 19%/sec, the initial engagement pressure is also selected, and the duty rate is adjusted accordingly. The PC solenoid valve 9 is duty-controlled.
On the other hand, when the throttle opening is larger than 42%, the duty rate change rate α is set to 38%/sec as a high throttle opening state, and the initial engagement pressure is also lower than before. The duty rate at the time of initial engagement (point Bb' in FIG. 4) is selected.

In the above embodiment, the engine throttle opening is divided into two cases, low throttle opening and high throttle opening, and the hydraulic pressure is duty-controlled. The duty rate at initial engagement and the duty rate change rate α may be changed depending on the throttle opening, or the duty rate at initial engagement and the duty rate change rate α may be changed analogously according to the throttle opening degree. Good too.

In the above embodiment, the present invention is applied to the shift from 1st speed to 2nd speed, but it is of course applicable to shifts at other stages.

As described above in detail with examples,
According to the shift control device according to the present invention, the hydraulic pressure to the friction engagement device that is engaged at the time of power-on shift of an automatic transmission is controlled both during the initial engagement of the friction element and during the engagement, and the output shaft Since the torque fluctuation is made smoother, the shift shock during shifting is reduced.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a part of the hydraulic circuit of an electronically controlled hydraulic control device to which the present invention is applied, and Figure 2 is the relationship between the control pressure by the hydraulic control valve and the duty rate of the pressure control solenoid valve in Figure 1. A graph showing,
FIG. 3 is a graph showing a conventional duty control method and output shaft torque fluctuations, FIG. 4 is a graph showing a duty control method and output shaft fluctuations by the shift control device according to the present invention, and FIG. 5 is a flowchart according to an embodiment of the present invention. In the drawing, 1 is a shift control valve, 8 is a computer, 9 is a pressure control solenoid valve, 12 is a hydraulic control valve, 14 is a 1-2 shift valve, and 19 is a kickdown servo (brake).

Claims (1)

[Claims] 1 A hydraulic pressure source that generates a constant line hydraulic pressure, a hydraulic control valve that regulates the line pressure to a hydraulic pressure below the line pressure and guides it as supplied hydraulic pressure to the friction engagement device, and a hydraulic control valve that regulates the hydraulic pressure that controls the hydraulic pressure control valve. and a solenoid valve whose duty is controlled as much as possible, and configured to increase the supplied hydraulic pressure by changing the duty rate at a predetermined rate of change in order to switch the friction element of the friction engagement device from a released state to an engaged state during gear shifting. In a conventional automatic transmission, when shifting from a relatively low speed gear to a relatively high speed gear with the accelerator pedal depressed, the rate of change in the duty rate during the engagement process of the friction element is calculated. ,
When the throttle opening of the engine is relatively small, the hydraulic pressure supplied to the frictional engagement device is gradually increased, and when the throttle opening is relatively large, the rate of change is increased to increase the hydraulic pressure supplied to the frictional engagement device. A shift control device comprising: a control device that rapidly increases the hydraulic pressure supplied to the shifting device.