JPH051167B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a four-wheel drive switching device for a part-time four-wheel drive vehicle that is capable of switching between two-wheel drive and four-wheel drive. be.

Prior Art Part-time four-wheel drive vehicles that can be switched between two-wheel drive and four-wheel drive by manual operation of a four-wheel drive select switch, etc. have been developed in the past (for example, Japanese Utility Model Publication No. 55-54573). ) is already in general use.

As mentioned above, when switching to four-wheel drive is performed manually, the driver may not be able to recognize the road surface or driving conditions that require switching to four-wheel drive, or may not be able to switch even if the driver recognizes it. If the switching operation is not performed due to the troublesome operation, the functions of the part-time four-wheel drive vehicle cannot be utilized.

Therefore, a vertical acceleration sensor that detects the vertical acceleration of the wheel support member or the vehicle body, etc. and converts the vertical acceleration into an electrical signal amount is provided, and the frequency with which the electrical signal amount exceeds a predetermined value within a set time is determined. When the set value is exceeded, a four-wheel drive switching actuator is activated to automatically switch to four-wheel drive.The applicant has developed and has already filed a patent application (see Japanese Patent Application No. 14611-1982). .

Problems to be Solved by the Invention In a part-time four-wheel drive vehicle having the above-mentioned configuration, the amount of electrical signal emitted by the vertical acceleration sensor exceeds a predetermined value within a certain predetermined time with a frequency that exceeds the predetermined value. Since the system is designed to automatically switch to 4-wheel drive when the vehicle is running at low speeds, if the above setting time is determined according to the low vehicle speed side, the system will automatically switch to 4-wheel drive when driving at high speeds. There is a problem of switching to wheel drive, or picking up a seam that exists at a relatively long distance on a paved road and switching to four-wheel drive.

The present invention automatically switches to four-wheel drive at a timing appropriate to the vehicle speed when driving on rough roads at low speeds, and when driving over relatively short distances on a paved road while driving at high speeds, or over relatively long distances. The object of the present invention is to provide a device that does not unnecessarily switch to four-wheel drive by picking up existing joints and the like.

Means for Solving the Problems The present invention provides a vertical acceleration sensor that detects vertical acceleration of a wheel support member or a vehicle body, etc., and converts the vertical acceleration into an electrical signal. A part-time four-wheel drive vehicle equipped with a road condition identification circuit that automatically issues a signal to switch from two-wheel drive to four-wheel drive when the frequency of acceleration exceeding a predetermined value exceeds a preset value. A vehicle speed sensor is provided for emitting a vehicle speed signal, and as the vehicle speed increases, the set time for calculating the frequency of vertical acceleration exceeding a predetermined value by the road condition identification circuit is reduced. This is characterized by the provision of a timer circuit for control.

Effects By adopting the above-described configuration, the present invention makes the set time required to account for the frequency at which the electrical signal amount based on vertical acceleration exceeds a predetermined value during high-speed driving on a highway, etc., shorter than when driving at low speed. This prevents the frequency of electrical signals based on vertical acceleration from exceeding a set value during shocks caused by picking up joints on paved roads, and prevents the system from accidentally switching to four-wheel drive mode on roads with good surface conditions, such as paved roads. You can prevent it from getting hot.

Embodiments Examples of the present invention will be described above with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a vertical acceleration sensor, and the vertical acceleration sensor 1 is configured to detect vertical acceleration of a wheel support member or a vehicle body of a part-time four-wheel drive vehicle, and output this as, for example, a voltage signal. has been done.

2 is a vehicle speed sensor that detects the vehicle speed and issues a vehicle speed signal; 3 is a timer circuit that issues a set time signal that gradually decreases as the vehicle speed signal from the vehicle speed sensor 2 increases, as shown in FIG. .

The voltage signal of the vertical acceleration sensor 1 and the set time signal of the timer circuit 3, which gradually decreases as the vehicle speed increases, are input to a road condition identification circuit 6 composed of a vehicle body vibration number counter 4 and a comparison circuit 5. Then, the number of voltage signals counted by the vehicle body vibration number counter 4 during the set time of the timer circuit 3 is compared with a reference value by the comparator circuit 5, and the counted value exceeds the reference value. A road condition identification circuit 6 outputs an output, and the output of the road condition identification circuit 6 includes a relay drive circuit 7, an electromagnetic relay 8 having a normally open contact, a four-wheel drive automatic changeover switch 9, and two sets of transfer contacts. A solenoid valve 11 is actuated via an electromagnetic relay 10, and a negative pressure actuator 12 automatically switches to four-wheel drive.

In the above, the common contact C of the electromagnetic relay 8 driven by the relay drive circuit 7 is connected to the automobile power supply, and the normally open contact NO is connected to the four-wheel drive changeover switch 9 and the electromagnetic relay 10 having two sets of transfer contacts. It is connected to the ground terminal through a series circuit with the excitation coil.

The two common contacts C of the electromagnetic relay 10 are connected to the automotive power supply and ground terminal, respectively, the two normally closed contacts NC are connected to the excitation coil on the two-wheel drive side of the solenoid valve 11, and the two normally closed contacts open contact
NO is connected to the excitation coil on the four-wheel drive side of the solenoid valve 11.

In the solenoid valve 11, when the electromagnetic relay 10 is de-energized, the excitation coil on the two-wheel drive side is energized, opening the valve to the intake negative pressure source on the two-wheel drive side and closing the valve to the atmosphere side. Negative pressure from the negative pressure source is introduced into the chamber on the two-wheel drive side of the negative pressure actuator 12 to switch to two-wheel drive, and when the electromagnetic relay 10 is energized, switch to four-wheel drive is performed, contrary to the above. is now being carried out.

In the above, when the four-wheel drive automatic changeover switch 9 is turned on, for example, when driving on a good road at normal speed and entering a bad road at the same speed, the vertical acceleration of the wheels increases and
The frequency with which the vertical acceleration exceeds a certain predetermined value within the set time also increases.

Therefore, as mentioned above, the output signal of the vertical acceleration sensor 1 that exceeds the input setting level of the vehicle body vibration number counter 4 is counted within a set time period that gradually decreases as the vehicle speed increases, and the The comparison circuit 5 compares this value with a reference value, detects that the vehicle is running on a rough road, and the road condition identification circuit 6 outputs an output.The output of the road condition identification circuit 6 drives the relay. The solenoid valve 11 is actuated via the circuit 7, electromagnetic relay 8, and electromagnetic relay 10 to automatically switch to four-wheel drive.

Also, when driving at high speed on a good road such as a paved road, the time set in the timer circuit 3 is short, so it is difficult to pick up irregularities at relatively short intervals on the pavement or seams that are located at relatively long distances. You won't have to switch to four-wheel drive when it's unnecessary.

If the integral value obtained by integrating the output signal of the vertical acceleration sensor 1 that exceeds the threshold setting value over a certain period of time using a threshold voltage setting circuit and an integrating circuit instead of the vehicle body vibration number counter exceeds the reference value, The road condition identification circuit 6 outputs an output, and the output of the road condition identification circuit 6 causes the solenoid valve 11 to be activated via the relay drive circuit 7 and the like.
may be activated.

In the illustrated embodiment, the relay drive circuit 7 maintains a constant state even if the output from the road condition identification circuit 6 disappears after the automatic switching to four-wheel drive is performed by the output from the road condition identification circuit 6. The time has a function to maintain the four-wheel drive state, which prevents too frequent switching from two-wheel drive to four-wheel drive and from four-wheel drive to two-wheel drive. be.

In addition, by configuring the input setting level of the vehicle body vibration number counter 4 to be variably controllable, the driver can arbitrarily change the input setting level depending on the presence or absence of cargo or the driver's preference, improving driving performance on rough roads and Safety can be improved.

Although the above embodiment shows an example in which the vertical acceleration is converted into a voltage signal, it may be converted into a current signal.

In addition to the intake negative pressure, any actuator such as a hydraulic type or an electric type can be used as the actuator.

Effects of the Invention As described above, according to the present invention, when the frequency of vertical acceleration signals exceeding a predetermined value exceeds a predetermined value within a predetermined time period that gradually decreases as the vehicle speed increases, the By switching to wheel drive, when driving at low speeds on rough roads, the vehicle can automatically switch to four-wheel drive at a timing appropriate to the vehicle speed.
To provide a device that prevents unnecessary switching to four-wheel drive by picking up unevenness at relatively short intervals on a paved road while traveling at high speed, or joints existing over a relatively long distance. This allows you to fully utilize the functions of a four-wheel drive vehicle, etc.
This can bring about great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing the relationship between the vehicle speed of the timer circuit and the timer setting time. 1...Vertical acceleration sensor, 2...Vehicle speed sensor,
3...Timer circuit, 4...Vehicle body vibration number counter,
5... Comparison circuit, 6... Road condition identification circuit, 7...
...Relay drive circuit, 8...Electromagnetic relay, 9...4
Wheel drive automatic changeover switch, 10...electromagnetic relay,
11... Solenoid valve, 12... Negative pressure actuator.

Claims (1)

[Claims] 1. A vertical acceleration sensor is provided that detects the vertical acceleration of the wheel support member or the vehicle body, etc., and converts the vertical acceleration into an electrical signal, and the frequency with which the vertical acceleration exceeds a predetermined value within a set time is set to a set value. In a part-time four-wheel drive vehicle equipped with a road condition identification circuit that automatically issues a signal to switch from two-wheel drive to four-wheel drive when the vehicle speed exceeds
A timer circuit is provided for controlling the set time for counting the frequency of vertical speeds exceeding a predetermined value by the road condition identification circuit to become shorter as the vehicle speed increases according to the vehicle speed signal from the vehicle speed sensor. A four-wheel drive switching control device for part-time four-wheel drive vehicles.