JPH0463266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a four-wheel drive vehicle, and more particularly to a four-wheel drive vehicle having a two-wheel drive switching mechanism.

Traditionally, in two-wheel drive vehicles, vehicle speed and throttle opening are detected, and the signals are input to a transmission control device such as a microcomputer. When the vehicle speed and throttle opening reach a set value, the transmission is activated to upshift or Some vehicles are equipped with an automatic transmission that controls the transmission by commanding a downshift.

By the way, while four-wheel drive vehicles have excellent traversal performance on rough roads and can obtain strong hill-climbing power, on flat roads, loss of driving force due to slipping of one of the tires is unavoidable. Therefore, in order to solve this problem, four-wheel drive vehicles equipped with a two-wheel drive switching mechanism have been provided.

Therefore, if an attempt is made to simply apply the automatic transmission described above to such a four-wheel drive vehicle, there will be a large difference in driving feeling since various characteristics are different between two-wheel drive and four-wheel drive.

In view of these problems, the purpose of the present invention is to
To provide a four-wheel drive vehicle that can provide almost the same running feeling regardless of whether it is two-wheel drive or four-wheel drive.

In order to achieve this object, the present invention detects whether the vehicle is in a two-wheel drive state or a four-wheel drive state, and causes the transmission control device to perform shift control according to shift characteristics corresponding to each state. There is a particular thing.

The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows a power transmission device for a four-wheel drive vehicle according to the present invention. This power transmission device is equipped with a torque converter 1 having a lock-up clutch 1a, and a parallel two-shaft auxiliary transmission 2 that automatically changes gears using hydraulic pressure. is transmitted to the main shaft 2a of the auxiliary transmission 2 via the torque converter 1, transmitted to the counter shaft 2b via a selected gear from the main shaft, and further transmitted to the differential case via the output gear 4 of the counter shaft. 5 is transmitted to the final gear 6 integrated with the final gear 5. The power of the auxiliary transmission 2 transmitted to the final gear 6 in this way drives the pinion gear 8 of the differential 7, which rotates the side gear 9 to rotate the first drive axle (for example, the front axle). axis).
On the other hand, the power of the auxiliary transmission 2 transmitted to the final gear 6 is also transmitted to the power extraction pinion gear 12 via the crown gear 11 integrated with the final gear 6. Further, in this power transmission device, a clutch 15 is disposed between the pinion gear shaft 13 and the propeller shaft 14, and the clutch 15 is connected and disconnected by a shifter shaft 16. Note that power is transmitted to a second drive axle (for example, a rear wheel drive shaft) (not shown) by a propeller shaft.

In the four-wheel drive vehicle shown in Fig. 1, the vehicle speed detector 2
1. In addition to the throttle opening degree detector 22, a switching operation detector 23 is installed to confirm whether the state is two-wheel drive or four-wheel drive, and each of these signals 21a, 22a,
23a is input to the microcomputer 24, and based on the shift characteristics stored in advance in the computer (see Fig. 2), the microcomputer 24 outputs a shift command signal A, and the auxiliary transmission is controlled by this signal. 2 shift valve is operated to automatically perform upshift or downshift. That is, when performing transmission control based on the transmission diagram shown in FIG. 2, during acceleration, L can be used up to a higher speed in four-wheel drive than in two-wheel drive even at the same throttle opening. Therefore, the acceleration feeling overcomes the circulating torque during four-wheel drive,
It feels the same as when driving on two wheels. Additionally, in four-wheel drive during deceleration, the downshift shift point moves to the lower speed side than in two-wheel drive, keeping engine rotations low and improving fuel efficiency. Note that in such a case, the efficiency of engine braking deteriorates, but this is canceled out by the circulating torque. In addition, the first
Reference numeral 25 in the figure is a kick-down switch, which is activated when the accelerator pedal 26 is depressed by about 90%, and inputs its signal 25a to the microcomputer 24 to adjust the appropriate speed change characteristics for two-wheel drive or four-wheel drive. Make the gear change depending on the position.

Furthermore, this four-wheel drive vehicle has a built-in control system that operates the lock-up clutch 1a of the torque converter 1, and has the shift characteristics in two-wheel drive shown in FIG. 3a or as shown in FIG. 3b. In the hatched area of the shift characteristics during four-wheel drive, the lock-up command signal B is sent from the microcomputer 24.
is output, thereby actuating the lock-up clutch 1a to directly connect the engine 3 and the main shaft 2a of the auxiliary transmission 2. In this way, in this embodiment, the lock-up operating range of the torque converter 1 is varied between two-wheel drive and four-wheel drive,
The feeling is improved by shifting the jerky feeling characteristic of four-wheel drive and the vibration during lock-up.

In the above embodiment, the auxiliary transmission 2 employs a constant meshing system with two parallel shafts, but the present invention is not limited to such an auxiliary transmission, and may be a planetary gear type. Further, although the above embodiment employs the torque converter 1 having the lock-up clutch 1a, if only the transmission control is performed in accordance with the shift characteristics shown in FIG.
It is sufficient to simply adopt a normal torque converter that is not equipped with a lock-up clutch 1a. Furthermore, although the microcomputer 24 is employed as the transmission control device in the embodiment described above, the present invention does not necessarily use a computer, but rather controls the vehicle speed signal, throttle opening signal, and whether it is two-wheel drive or four-wheel drive. Other signal circuits may be used to process the confirmation signal and output a command signal to the transmission as a result. Further, in the embodiment, the vehicle speed is detected from the speedometer, but the vehicle speed may be detected directly from the output shaft or the like, or may be detected via a governor or the like. In addition, in the example,
Although the throttle opening degree is detected via a potentiometer that is operated in accordance with the amount of depression of the accelerator pedal 26, it may also be obtained by detecting negative pressure in an intake manifold or the like. .

It should be noted that the shift characteristics shown in the above embodiments are shown by way of example, and it goes without saying that they may be modified and implemented as appropriate depending on the type of vehicle.

As described above, in the four-wheel drive vehicle according to the present invention, the transmission is controlled according to different shift characteristics in two-wheel drive mode and four-wheel drive mode, so it is possible to realize a vehicle with extremely good driving feeling. It is also possible to improve fuel efficiency.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram showing a power transmission device for a four-wheel drive vehicle according to the present invention, Fig. 2 is a shift diagram showing its shifting characteristics, and Figs. 3 a and b are shift diagrams of Fig. 2. It is a shift diagram in which a lock-up range is further added to the above. 1... Torque converter, 1a... Lock-up clutch, 2... Auxiliary transmission, 3... Engine, 1
5...Clutch, 16...Shifter shaft, 21
...Vehicle speed detector, 22...Throttle opening degree detector, 23...Switching operation detector, 24...Microcomputer.

Claims (1)

[Claims] 1. A four-wheel drive vehicle having a two-wheel drive switching mechanism, which is equipped with a vehicle speed detection means, a throttle opening detection means, and a switching operation detection means of the switching mechanism, and inputs the signals obtained from each of the detection means, A four-wheel drive vehicle characterized by being equipped with a transmission control device that provides a transmission with a shift command based on different shift characteristics during drive and two-wheel drive.