JPS5851499B2 - Anti-skid device for tractors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid device for a tractor that controls the braking force of the wheels to an optimum value so as to prevent the wheels from locking during braking of the vehicle.

This type of anti-skid device adjusts the wheel speed to a slip ratio of 2 to the vehicle body speed to prevent the wheels from locking during sudden braking.
The purpose is to decelerate around 0 (%).

FIG. 1 is a block diagram of a conventional anti-skid device applied to this type of pneumatic brake system.

In the figure, 1 is a speed detector such as a signal generator that generates a signal with a frequency proportional to the rotational speed of the wheel, 2 is an f-V converter that generates a DC voltage proportional to the rotational speed of the wheel, and 3 is a differential circuit. , 4 and 5 are comparators, 6 and 7 are amplifiers for amplifying the output signals of the comparators 4 and 5, and 8 is a braking pressure reducing solenoid valve installed in a braking pressure regulating device (not shown). When excited, the braking pressure is reduced at a predetermined rate.

Reference numeral 9 denotes a pressure recovery control solenoid valve installed in the brake pressure adjustment device. When the solenoid valve 9 is energized, the brake pressure rapidly returns to the brake pedal pressure, and when the excitation is cut off, the brake pressure gradually returns to the brake pedal pressure. is pressurized.

Next, the operation of the conventional device having the above structure will be explained with reference to the operation diagram shown in FIG.

In Fig. 2, 10 is a diagram showing the vehicle speed, 11 is f
- Diagram showing the wheel speed signal with the output signal of the V converter 2, 12
is a diagram showing the ideal wheel speed signal, which is approximately 20% relative to the vehicle speed.
13 is a diagram showing the output signal of the differential circuit 3, 14 is a diagram showing the brake pedal pressure, and 15 is a diagram showing the control braking pressure.

When the braking pressure increases during braking and reaches a road reaction force determined by the friction coefficient between the wheel cart, the wheels, and the road surface, the wheels tend to lock at a large deceleration.

When the wheel deceleration reaches point A, which is the set deceleration of the comparator 4, a pressure reduction signal is generated from the comparator 4, the pressure reduction signal is amplified by the amplifier 6, the pressure reduction solenoid valve 8 is energized, and the braking pressure is set in advance. Begin to depressurize at the same speed.

Here, the wheel deceleration decreases due to the decrease in the braking pressure, and at point B, when the deceleration reaches the set deceleration or less, the reduction in the braking pressure is stopped, and the braking pressure gradually increases toward the brake pedal pressure.

Thereafter, the wheel speed accelerates toward the vehicle body speed, and when the wheel speed reaches point C, which is the acceleration set by the comparator 5, a sudden pressurization signal is generated from the comparator 7, and the sudden pressurization signal is amplified by the amplifier 7. Then, the sudden pressurization solenoid valve 9 is energized and the braking pressure starts to be suddenly pressurized at a predetermined speed.

The wheel acceleration decreases due to the increase in the braking pressure, and the sudden increase in the braking pressure stops at point D where the wheel acceleration reaches the set acceleration or less.

The purpose of sudden pressurization is to compensate for over-decreasing of braking pressure, and while repeating the above operations, the wheel speed is adjusted to a slip rate close to the ideal deceleration speed of 12, which corresponds to a slip rate of approximately 20% at a vehicle speed of 10. The purpose was achieved by moving it back and forth.

However, when controlling the rear wheels of a tractor using this method, there are problems as described below.

When a tractor is traveling by towing a loaded trailer, the load on the rear wheels of the tractor is very large, but when the tractor is traveling alone, the load on the rear wheels of the tractor is extremely small, and the ratio is 10. The ideal braking force when towing a trailer and when the anti-skid device is activated when a single tractor is used is very different.

Therefore, wheel deceleration in response to excessive braking pressure and wheel acceleration due to a decrease in braking pressure during control are significantly different when a single tractor is used and when a trailer is being towed, and the f-V converter 2 reduces the braking pressure without a time delay. The speed is also limited by the capacity of the brake pressure line and the capacity of the brake pressure regulator, and there is a restriction that it cannot be increased too much.

For this purpose, various setting values such as the delay characteristic of the f-V converter and the comparator 4 are used to reduce the wheel speed to around 20 @
, 5. When determining the deceleration setting value and braking pressure depressurization or pressurization speed, etc. in 5, the slip ratio of the wheel speed under control to the vehicle body speed becomes larger than the ideal value when a single tractor is used, and the wheels may lock during control, or Due to the sudden increase in braking pressure during control, the vibration cycle of one control resonates with the vehicle body, resulting in poor riding comfort.

Conversely, if the set value is determined so that the wheels are decelerated in a range close to the ideal braking range when the tractor is on its own, the slip rate of the wheels will be smaller when the tractor is connected, and the braking distance will be longer than when the wheels are locked. Ta.

As described above, the conventional system has the disadvantage that it cannot be fully controlled when the wheel load fluctuates greatly.

This drawback can be overcome to some extent if the speed of the vehicle body during braking can be accurately detected, but at present it is very expensive in terms of cost and is not very practical due to its accuracy.

This invention solves the above-mentioned drawbacks by providing a switch that detects when a trailer is being towed, and using the switch to change various setting values, the rear wheels of the tractor are decelerated in the ideal slip range both when the tractor is traveling alone and when towing a trailer. An embodiment of the present invention shown in FIG. 3 will be explained below.

In FIG. 3, reference numeral 16 denotes a traction detection switch for detecting that the trailer is being towed, and the traction detection switch is configured as shown in FIG. 4, for example.

In FIG. 4, 17 is a battery loaded on a tractor;
18 is a brake switch, 19 is a brake lamp of the tractor, 20 is a brake lamp of a trailer, 21 is a coupling that is connected when towing the trailer, and the traction switch 16 is connected to a coil 22 inserted in the middle of the brake lamp circuit of the trailer. It is composed of a reed switch 23 that is activated by magnetic flux generated by a coil 22.

Next, a circuit having the above configuration will be explained.

First, when towing a trailer, the coupling 21 is connected, and when braking, the brake switch 18 is turned ON and the brake lamps 19 and 20 are turned on.

The current of the brake lamp 20 of the trailer flows through the coil 22, and the reed switch 24 is turned on by the magnetic flux generated by the coil 22.

The impedance of the coil 22 is set to be sufficiently smaller than the impedance of the brake lamp 20.

When the tractor is traveling alone without towing a trailer, the coupling 21 is naturally not connected, so the reed switch 23 remains OFF even during braking.

That is, when braking, the output of the reed switch 23 is O when the vehicle is on a single vehicle.
Turns on when FF is towing.

In the embodiment shown in FIG. 3, the towing detection switch 16 changes the setting value of the deceleration of the comparators 4 and 5 so that when a new tractor is being used, the ideal braking pressure is lower than when towing a trailer, so excessive braking pressure is quickly removed. The brake pressure is brought closer to the ideal brake pressure, and the wheel speed is decelerated to a slip ratio of around 20 (%) relative to the vehicle speed.

Furthermore, when the tractor is on a single vehicle, the deceleration setting value of the comparator 4 is made smaller than when towing a trailer, the generation timing of the braking pressure reduction signal is advanced and the release timing is delayed, and the excessive braking pressure is quickly brought closer to the lower ideal braking pressure, while the comparator 5 Increase the acceleration set value for the brake to a value greater than when towing a trailer, shorten the generation time of the sudden braking pressure signal, or suppress the occurrence of the sudden braking pressure signal, and avoid increasing the wheel slip rate due to sudden braking pressure and reducing the number of control cycles. A meaningful increase can be prevented.

In the embodiment in FIG. 3, comparators 4, 5
Although the method of switching is explained next, there is no problem in switching other control factors or control methods.

In the embodiment shown in FIG. 4 above, the traction switch is explained as an electrical means, but it is also possible to provide a pressure switch in the brake pipe installed on the tractor side and connected to the trailer and use it as a traction switch. It is possible.

In addition, by providing this towing switch, anti-
It is also possible to use it for devices other than skid devices.

For example, it has the advantage that it can be used as a tire load sensor for a tire pressure detection device that warns of abnormal decreases in tire pressure.

As explained above, by providing a trailer towing switch, the present invention changes the control factor or control method of the anti-skid device between when a single tractor is being towed and when towing a trailer, and decelerates the wheels at an ideal slip rate in both conditions. It has the advantage of providing a device that can do this in a simple manner.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional device, FIG. 2 is an explanatory diagram of the operation of FIG. 1, and FIGS. 3 and 4 are configuration diagrams showing an embodiment of the present invention. In the figure, 1 is a signal generator, 2 is an f-V converter, and 3
is a differential circuit, 4 and 5 are comparators, 6°7 is an amplifier,
8 and 9 are solenoid valves, and 16 is a traction detection switch. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A speed detector that detects the rotational speed of the wheels, and a braking force control that detects the deceleration of the wheels by differentiating the output of the detector and generates a braking force reduction signal when the wheel deceleration has decelerated to a predetermined value or more. A signal generating device, a braking force release device that is activated by the output signal of the braking force control signal generating device and operates in a direction to release the braking force, and a switch that detects that a trailer is being towed; is input to the braking force control signal generating device, and when the trailer is being towed, the wheel speed when the anti-skid device is in operation is controlled so that the slip ratio relative to the vehicle body speed is greater than when the trailer is not being towed. Anti-skid device for tractors.