JPH0126423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic transmission, and more particularly to an automatic transmission that automatically selects a shift pattern for engine braking when traveling downhill.

Automatic transmissions usually use a combination of vehicle speed equivalent signals and engine load (throttle opening, etc.) signals to
For example, it is configured to automatically shift gears according to a shift pattern as shown in FIG.

By the way, if such a shift is performed even when driving downhill, the automatic transmission will continue to select the highest gear (3rd gear in Figure 2) because the engine load is small.
Due to the gear ratio, sufficient engine braking effect cannot be achieved. When driving in this way, the driver should set the manual valve to 2nd gear engine braking ().
It was necessary to manually operate the automatic transmission to maintain the second gear or first gear by setting the automatic transmission to the range or first gear engine brake traveling () range, thereby obtaining the engine brake.

In order to eliminate the hassle of conventional manual operation, the applicant has developed an automatic transmission that automatically selects a shift pattern for engine braking when engine braking is required when driving downhill. This has already been proposed in Japanese Patent Application Laid-Open No. 50-109362.

By the way, in conventional automatic gear shifting as typified by this, when determining whether or not engine braking is necessary, it is determined whether the accelerator pedal is released and the brake pedal is depressed during braking, or in conjunction with this, vehicle speed conditions, road surface slope, etc. It was determined that engine braking was necessary when these conditions were satisfied.

However, engine braking is really necessary to prevent vapor lock due to overheating of the brakes, and in this sense, the conventional judgment of whether or not engine braking is necessary is not always accurate, and unnecessary engine braking may reduce vehicle speed. You may have to adjust the vehicle speed by operating the accelerator.

In the above context, the present invention attempts to solve the above-mentioned problem by determining that the time when the brake temperature exceeds a set value during brake operation is a necessary condition for engine braking.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 indicates an automatic transmission, and 2 indicates a shift pattern changing actuator. When energized, the automatic transmission 1 is automatically shifted along an engine braking shift pattern in which the shift line is shifted to a higher vehicle speed side than the normal driving shift pattern as shown in Fig. 3. do.

The actuator 2 is provided with a brake operation switch 3, a brake temperature switch 4, a select switch 5, and a battery 6 connected in series. Brake operation switch 3 is activated when the brake pedal is depressed.
It is a normally open switch that closes only when the brake is activated in response to the generation of brake fluid pressure, etc., and the brake temperature switch 4 controls the temperature of the brake friction elements, that is, the brake rotor, brake drum, brake pad, brake shoe, etc., or the temperature of the air in the vicinity thereof. The select switch 5 is a normally open switch that closes only when the brake temperature exceeds a set value in response to the engine brake temperature, and the select switch 5 is a manual switch that is closed when the automatic engine brake shift pattern selection function of the present invention is desired and opened when it is not desired. Switch.

In this configuration, when the driver closes the select switch 5, the automatic transmission of the present invention automatically selects a shift pattern for engine braking as follows. That is, when the brakes are applied while driving downhill and this brake operation is continued for a certain length of time, that is, when driving downhill where engine braking is required, the brake activation switch 3 is closed and the brakes are then turned off. The brake temperature switch 4 closes due to the rise in brake temperature due to continued operation. At this time, since the select switch 5 is closed, the shift pattern changing actuator 2 is energized by the battery 6, and the automatic transmission 1
selects the engine brake shift pattern shown in Figure 3 from the normal running gear shift pattern shown in Figure 2,
By automatically shifting gears according to the latter pattern, engine braking can be applied automatically.

However, the brake does not operate and the switch 3
is open, or if the brake temperature switch 4 is open to stop this operation immediately even if the brake is applied, that is, when driving without engine braking, the actuator 2 continues to be deenergized and the automatic gear shift is stopped. The machine 1 can perform automatic gear changes according to the normal driving gear change pattern shown in FIG.

Note that if the driver leaves the select switch 5 open, the actuator 2 is not energized, and therefore the automatic transmission 1 is always in the state shown in FIG. Automatic gear shifting can be performed according to the normal driving gear shifting pattern.

Thus, as described above, the automatic transmission of the present invention operates the brakes and performs gear shifting during driving when the brake temperature rises above the set value due to long-term brake operation, that is, during driving when engine braking is really required. Since the pattern is configured to automatically switch from the normal driving pattern shown in Figure 2 to the engine braking pattern shown in Figure 3, you can drive while applying engine braking without having to manually switch the manual valve. This makes it possible to eliminate the hassle of operation, and to apply engine braking only when it is really necessary.
This can prevent unnecessary engine braking from forcing the vehicle speed to be adjusted by operating the accelerator.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the automatic transmission of the present invention, Fig. 2 is a shift pattern diagram for normal driving of the automatic transmission, and Fig. 3 is a schematic diagram of the automatic transmission of the present invention.
The figure is also a diagram of the gear change pattern for engine braking. DESCRIPTION OF SYMBOLS 1... Automatic transmission, 2... Gear shift pattern change actuator, 3... Brake operation switch, 4
...Brake temperature switch, 5...Select switch, 6...Battery.

Claims (1)

[Claims] 1. In an automatic transmission that changes gears based on a normal driving shift pattern defined by a combination of a vehicle speed equivalent signal and an engine load signal,
When the brake is operating and the brake temperature is higher than the set value according to the brake operation signal and brake temperature signal,
An automatic transmission characterized in that the automatic transmission is configured to change gears along an engine braking shift pattern in which a shift line is shifted to a higher vehicle speed side than the normal driving shift pattern.