JPS627008B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a part-time four-wheel drive vehicle that is normally two-wheel drive using one of the front and rear wheels, but which runs in four-wheel drive when necessary, to solve the problem of drive wheel slippage during two-wheel drive. The present invention relates to a two- and four-wheel drive switching control device that automatically switches to four-wheel drive when the vehicle is in use.

In such part-time 4-wheel drive vehicles, switching between 2- and 4-wheel drive is left to the driver's operation, so if the vehicle slips when driving on a road with a low friction coefficient, it is recommended to switch to 4-wheel drive. Even though it is desirable because it improves handling and fuel efficiency, there are cases where the original performance of a four-wheel drive vehicle is not fully demonstrated because the switch to four-wheel drive is not made.

In order to improve this point, the applicant has already filed a patent application for a system that constantly senses the occurrence of slip in the drive wheels during two-wheel drive, and automatically switches to four-wheel drive when slip occurs. 1980-
No. 88331 (see Japanese Unexamined Patent Publication No. 15019/1988). However, this system focuses on the fact that slippage can be determined based on the rotational difference between the front and rear wheels, and switches to four-wheel drive based on this rotational difference. Therefore, at least two rotation sensors for detecting the rotational speeds of the front and rear wheels, a subtractor for subtraction, etc. are required, making the structure complicated. In addition, it is not possible to obtain the exact rotational difference value necessary for determining slippage until after the wheels have rotated to a certain extent, so it takes time to determine slippage and switch to four-wheel drive, and the responsiveness may be affected. It's bad.

The present invention has been developed in view of the above circumstances.When a slip occurs, a rotational fluctuation occurs in the drive wheel that is much larger than that in the case of acceleration. By focusing on the fact that the rotational angular acceleration of the two-wheel drive system can be detected and determining the slip occurrence state based on this, and switching to four-wheel drive, we have improved the responsiveness and reliability of switching. It is an object of the present invention to provide a two-wheel drive and four-wheel drive switching control device that is simplified in terms of its structure.

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, the transmission system of a part-time four-wheel drive vehicle to which the present invention is applied will be explained with reference to FIG. 1. It is based on a FF two-wheel drive system, and reference numeral 1 indicates the crankshaft from the engine;
2 is a clutch, and 3 is a manual transmission. The transmission 3 is of a constant mesh type, with an output shaft 6 disposed parallel to an input shaft 4, and a first speed gear 7, which meshes with the input and output shafts 4, 6. 1
1 Gears 8 and 12 for second speed, gear 9 for third speed,
Gears 10 and 14 for the 13th and 4th speeds are provided. Each of these gears is connected to two sets of synchronization mechanisms 1
5 and 16, and is integrally connected to one of the output shafts 4 and 6 to perform a shift from 1st speed to 4th speed. Furthermore, the reverse gear 17 of the input shaft 4
is engaged with a gear 18 on the sleeve side of one of the synchronizing mechanisms 16 via an idler gear (not shown) to obtain a reverse gear.

A drive pinion 5a is integrally formed at the front end of the output shaft 6 of the transmission 3, and the drive pinion 5a is connected to the crown gear 5b of the front wheel final reduction device 5 disposed below the input shaft 4 between the clutch 2 and the transmission 3. are meshing together. As a result, the power from the transmission 3 is directly transmitted to the front wheels via the front wheel final reduction device 5, and two-wheel drive driving using the front wheels is performed.

Further, the side of the output shaft 6 of the transmission 3 opposite to the drive pinion 5a extends rearward, and is gear-coupled to the transfer drive and driven gears 19, 20 of the transfer device 22 mounted at the rear of the transmission 3. The shaft 21 of this gear 20 is connected to a rear drive shaft 23 via, for example, an electromagnetic clutch 32 for switching between two and four wheel drive.
Further, transmission is configured to be transmitted via the propeller shaft 24 to a rear wheel final reduction gear 25 and the rear wheel side. The electromagnetic clutch 32 includes a drive member 27 coupled to the driving shaft 21 via a drive plate 26, and a driven member 27 coupled to the driven shaft 23 and disposed with a slight gap inside the drive member 27. It has a coil 29 assembled inside the member 28 and the drive member 27, and electromagnetic powder is housed in the gap between the members 27 and 28. The brush 30 and the slip ring 31 that are in sliding contact with each other cause the coil 29 to have a predetermined position. By supplying a clutch current, magnetic lines of force are generated, electromagnetic particles are integrated, and the members 27 and 28 are integrated by magnetically coupling, so that the clutch engages the members 27 and 28. In this way, when the clutch current is zero, no lines of magnetic force are generated and there is no coupling by electromagnetic particles, so the electromagnetic clutch 3
2 is in a released state and the power transmission to the rear wheels is cut off, and when the electromagnetic clutch 32 is engaged by supplying a predetermined clutch current, the power is also transmitted to the rear wheels and four-wheel drive running is possible. It will be done.

Next, referring to FIG. 2, the control system for switching between 2 and 4 wheel drive using the electromagnetic clutch 32 will be explained. It has a rotation sensor 33 that generates pulses, and the pulse signal from the rotation sensor 33 according to the rotation speed is converted into DA. The analog value is converted into an analog value in the circuit 34 to determine the angular velocity, and further differentiated in the differentiating circuit 35 to calculate the angular acceleration. Here, the angular acceleration also occurs in the case of sudden acceleration, although the value is small, so in order to exclude this case, the comparator 36 compares it with the set value corresponding to the acceleration at this time using the reference voltage generation circuit 37. If a value larger than this is detected, it is determined that a slip has occurred. and comparator 36
are the hold circuit 38 and the clutch current control circuit 39.
It is electrically connected to the brush side of the electromagnetic clutch 32 through. The hold circuit 38 holds the state when a signal is input from the comparator 36.
The hold is released by a release signal from a hold release signal generation circuit 40 that determines whether the accelerator is off, the brake is on, the vehicle speed is zero, etc. The clutch current control circuit 39 also receives a signal from a manual changeover switch 41, and when a signal is input from the hold circuit 38 or the manual changeover switch 41, a predetermined clutch current is supplied.

To explain the operation of the device of the present invention constructed in this way, even if angular acceleration is sensed during acceleration without causing slip or during normal running, it is removed and no signal is output from the comparator 36. Therefore, the input signal to the clutch current control circuit 39 is only the signal from the manual changeover switch 41. When the switch 41 is off, there is no input signal to the circuit 39, so the clutch current becomes zero, and the electromagnetic clutch 3
2 is released, and two-wheel drive driving is performed. When the switch 41 is turned on by the driver's will and a signal is input to the circuit 39, the circuit 39
As a result, a predetermined clutch current is supplied to the electromagnetic clutch 32 to engage it, thereby switching to four-wheel drive.

Next, when a slip occurs when starting or running, the slip is immediately sensed by the comparator 36 because the angular displacement of the wheel is small, that is, at the beginning of the slip, a large rotational angular acceleration occurs, and the hold circuit 38 is sensed. A signal is then input to the clutch current control circuit 39. Therefore, this circuit 39
In this case, a predetermined clutch current is supplied when no signal is input from the manual changeover switch 41, thereby automatically switching from two-wheel drive to four-wheel drive. This state continues as long as the accelerator pedal is pressed by the hold circuit 38 and the vehicle accelerates, and after acceleration, it is released by a release signal from the hold release signal generation circuit 40 and returns to two-wheel drive. Four-wheel drive driving is performed only when the vehicle is substantially slipping.

The present invention provides a two-wheel drive system for a four-wheel drive vehicle that directly transmits power to one of the front and rear wheels, and also transmits power to the other of the front and rear wheels by engaging a clutch as necessary. , a current control circuit to which a signal is output when the rotational angular acceleration exceeds a predetermined value is inputted via a hold circuit, the clutch is engaged and disengaged by a clutch current from the current control circuit, and a signal is output from a hold release signal generation circuit. and a circuit for inputting a release signal to the hold circuit, and is configured to automatically switch to four-wheel drive when a slip occurs due to rotational angular acceleration of the two-wheel drive system, and return to two-wheel drive again in response to a predetermined release signal. Therefore, compared to systems that determine the occurrence of slip based on the difference in rotation between the front and rear wheels, the structure of the control system is simpler, the response is better, and there is less risk of malfunction. When a slip is detected in the control system, it is temporarily held in that state and then released by a release signal, so four-wheel drive performance can be reliably demonstrated without being affected by slip fluctuations.

Note that the present invention can be similarly applied to cases where a hydraulic clutch is used in place of the electromagnetic clutch in the transfer device 22.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a four-wheel drive vehicle to which the present invention is applied, and FIG. 2 is a circuit diagram showing an embodiment of the device according to the present invention. 3...Transmission, 5...Front wheel final reduction gear, 22...
...transfer device, 25...rear wheel final reduction device,
32... Electromagnetic clutch (clutch), 33... Rotation sensor, 34... DA conversion circuit, 35... Differential circuit, 36... Comparator, 38... Hold circuit,
39...Clutch current control circuit, 40...Hold release signal generation circuit, 41...Manual changeover switch.

Claims (1)

[Scope of Claims] 1. A two-wheel drive system in a four-wheel drive vehicle that directly transmits power to one of the front and rear wheels, and also transmits power to the other of the front and rear wheels by engaging a clutch as necessary. A current control circuit to which a signal is output when the rotational angular acceleration exceeds a predetermined value is inputted via a hold circuit, the clutch is engaged and disengaged by a clutch current from the current control circuit, and a signal is output from a hold release signal generation circuit. and a circuit for inputting a release signal to the hold circuit, so that when a slip occurs due to rotational angular acceleration of the two-wheel drive system, the drive is automatically switched to four-wheel drive, and the drive is returned to two-wheel drive again by a predetermined release signal. A two- and four-wheel drive switching control device characterized by the following configuration.