JP3513112B2 - Height adjustment device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a vehicle equipped with an air suspension. The present invention is a vehicle height adjusting device in which a vehicle height supported by an air suspension is kept constant by automatically controlling the air pressure supplied to the air suspension. The present invention relates to improvement of a device that can be changed by operation.

[0002]

2. Description of the Related Art Air suspensions having an air spring between an axle and a chassis have been widely used in large vehicles. The vehicle height adjustment device for vehicles equipped with an air suspension is equipped with a vehicle height sensor between the axle on which the air suspension is arranged and the chassis, and the detection output of this vehicle height sensor is input to the control device as an input signal to determine the vehicle height. The air pressure of each air suspension is automatically adjusted so as to be maintained at the set target value.

A vehicle equipped with such a device can always maintain a constant vehicle height even when the weight of the load or the number of passengers changes. However, for example, when performing cargo handling work, it is necessary to make the height of the loading platform of the vehicle equal to the height of the platform of the loading / unloading base. At this time, it is possible to temporarily change the vehicle height by operation. Devices which are designed to be capable are known. In a vehicle equipped with such a device, for example, an operation switch that can be operated from the outside is provided at the rear part of the vehicle, and the driver stops the vehicle at the platform position, then leaves the driver's seat and operates this operation switch. Can be operated to adjust the height of the bed to exactly the height of the platform.

In such an apparatus, the vehicle height adjusting device is operated even while the vehicle is stopped or the engine is stopped, and the control target value of the vehicle height adjusting device can be temporarily changed. (See Japanese Patent Laid-Open No. 10-166830). That is, the operation switch can be operated “up” or “down” with a small lever, and while the lever is being operated, the automatic control operation is temporarily stopped and the operation is performed according to the operation. Increases or decreases the air pressure in the air suspension. Along with this, the height of the loading platform slowly changes upward or downward. When the operation switch operation is completed and the lever is returned to the neutral (OFF) position, the control device reads the vehicle height value immediately after that from the detection output of the vehicle height sensor and sets this value as a new target value for control. It is configured to continue the vehicle height adjustment control. Here, the vehicle height value immediately after that is, but in reality, since there is a fine vertical vibration in the vehicle height, the average value of the detection output of the vehicle height sensor for a very short time t ₀ (for example, 1 second) is calculated immediately after that. Then, this is set as a target value.

In this state, automatic control of the air suspension is continued even when the vehicle is stopped or the engine is stopped. For example, when the vehicle height decreases as the weight of the load increases due to the cargo handling work, the air pressure of the air suspension is increased to maintain the vehicle height at the target value. Therefore, the height of the loading platform can be kept equal to the height of the platform over the period of the cargo handling work. When the loading operation is completed, the driver releases the target value of the vehicle height set in this vehicle height adjusting device by operating the driver's seat, and the standard value set before the loading operation is read from the memory. Then, this is automatically set as a new target value, and automatic adjustment is executed so that the vehicle height becomes a standard value.

[0006]

The following problems have been experienced with such a device. That is, for the purpose of cargo handling work, the driver temporarily operates the operation switch to temporarily adjust the height of the loading platform to the height of the platform to gently raise (or lower) the loading platform. At this time, when the upper surface of the platform matches the height of the platform, the operation switch UP (or DOW)
When the button N) is released, the height of the loading platform immediately after that is automatically set as the control target value of the new vehicle height. Then, when the operation switch is released, the flow of air pressure supplied (or exhausted) to the air suspension to change the height of the loading platform stops, so the lifting (or lowering) of the loading platform should stop here. Is. However, there is a certain volume in the air line of the air pressure control system of the air suspension, and the air pressure in the air line changes slightly until it converges to the final equilibrium state. Along with this change, the height of the bed also slightly rises (or falls).

Then, the control device controls the vehicle height according to the new target value that has been set, so that this is automatically adjusted if the height of the bed is too high or too low. In other words, if the control target value is set at the position where the height of the platform coincides with the height of the platform, the adjustment operation will be performed again after passing the position where the control coincides. This is an overshoot. If the change in the height of the bed after releasing the operating switch is relatively small and this is an allowable amount as a control error, the control device does not respond. However, there are cases where the vehicle height is adjusted for the overshoot all the time due to some small shock. In such a case, the driver and the person who performs the cargo handling work will feel uncomfortable.

The present invention has been made against such a background, and an object thereof is to provide a vehicle height adjusting device which does not cause overshoot when the vehicle height of the vehicle height adjusting device is changed by operation. And The present invention does not cause an unexpected adjustment operation by the operator due to the time required for the air pressure in the pneumatic line of the control system to reach an equilibrium state after the control valve is displaced to the final state. The purpose is to provide a device.

As a related technique, Japanese Laid-Open Patent Publication No. 11-123920 discloses a technique for preventing the vehicle height from rising too high when the vehicle height is returned to the original state. This is not intended to reduce the above-mentioned overshoot, and the method of the countermeasure is also different. Japanese Unexamined Patent Publication No. 10-278533 discloses a technique for reducing the inclination of the chassis when the vehicle height is adjusted by an operation.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a vehicle height sensor for a vehicle height sensor when a certain time t elapses when the vehicle height is adjusted by operating the operation switch, not immediately after the hand is released from the operation switch. It is characterized in that a value is captured and this is set as a new set value.

This time t is different from the short time t ₀ for averaging the detection values of the vehicle height sensor described as the operation of the above-mentioned prior art. It is also possible to design to provide a short time t ₀ for this averaging after the time t has elapsed.

That is, according to the present invention, the air suspension (1) for supporting the chassis (10) on the axle (11), the air valve (2) for adjusting the air pressure supplied to the air suspension (1), and the axle (11). ) To the chassis (10) as a vehicle height, and the air valve so that the vehicle height is maintained at a target value by using a detection output of the vehicle height sensor (3) as an input. A control device (4) for automatically controlling the vehicle, and an operation switch (5) for vehicle height adjustment connected to the control device (4),
The control device (4) temporarily suspends the operation of the automatic control means when the operation switch (5) is operated, and changes the air pressure according to the input of the vehicle height adjustment switch. In the adjusting device,
When the vehicle height is changed according to the operation input of the operation switch (5), the vehicle height sensor after a predetermined time t (however t ≠ 0) has passed after the operation input of the operation switch (5) has disappeared. It is characterized in that it includes means for setting the detection output of 1 as a new target value. The time t is preferably 3 seconds to 7 seconds.

The numbers in the above parentheses are reference numbers in the embodiment drawings described later. This is a supplementary description for easy understanding of the configuration of the invention, and is not for limiting the understanding of the invention to the embodiments.

With this configuration, it takes a certain amount of time for the atmospheric pressure in the piping of the air pressure control system to reach an equilibrium state, and even if the vehicle height may change slightly during that time, the time t
When elapses, the atmospheric pressure of the control system becomes equilibrium or almost equilibrium. Therefore, the detection output of the vehicle height sensor is taken in after the vehicle height becomes stable, and this is set as a new target value. After that, the control device automatically adjusts the vehicle height so as to reach this newly set target value, so the control starts from a stable state, and as described above, unnatural control is always caused. It will never happen.

In this device, when the vehicle height is adjusted by an operation, the operator does not release the operation switch when the vehicle height reaches a target height, but rather slightly releases the operation switch. Good to operate. For example, it is better to operate the operation switch to turn off the operation switch at a timing just before the moment when the platform is at the height of the platform. When a test was conducted on a large number of drivers, it was found that such an operation is a natural operation for the driver, and is apt to become accustomed by practicing a few times, and there is no problem at all.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an air suspension control system according to an embodiment of the present invention. FIG. 2 is a structural diagram of the air suspension for the left rear wheel. Air pressure used for the air suspension system is supplied to the air tank 10 from an air pressure source (not shown) via a check valve. The air pressure of the air tank 10 is supplied to the left and right air suspensions 1 via the left and right air valves 2, respectively. Each air valve 2 is controlled by an electric signal from the control device 4. Controller 4
Includes a program control circuit.

As shown in FIG. 2, one air suspension 1 is composed of a pair of air springs 6. The axle 12 is connected to the chassis 11 via the air suspension 1.
Support. The air suspension 1 is provided with a vehicle height sensor 3 which mechanically detects the distance between the axle 12 and the chassis 11 in parallel. The vehicle height sensor 3 is a mechanical-electrical conversion element, for example, converts mechanical displacement into a change in the resistance value of a resistor, and the current value passing through this resistor becomes the detection output. The shock absorber 13 absorbs a sudden displacement between the axle 12 and the chassis 11.

Returning to FIG. 1, the detection output of the vehicle height sensor 3 is taken into the control device 4 and becomes control input information of the program control circuit via an interface (not shown). The control device 4 is arranged in the cab of the truck, and an indicator lamp 7 and a main switch 8 are provided in the driver's seat. An operation switch 5 is provided in the vicinity of the loading / unloading port of the luggage of the truck outside the cab. Further, the output information of the rotation sensor 9 for detecting the vehicle speed is taken into the control device 4.

In the system thus constructed, when the vehicle is traveling, the driver sets the main switch 8 to the normal position, so that the control unit controls the vehicle height sensor 3 to operate.
According to the detection output of, the air valve 2 is controlled so that the vehicle height becomes a standard set target value, and the air pressure of the air suspension 1 is adjusted. As a result, the vehicle height is controlled to a constant value.

A case will now be described in which the vehicle arrives at the position of the loading platform for loading and unloading luggage and the height of the loading platform is adjusted to the upper surface of the platform. The driver brings the vehicle closer to the platform to stop the vehicle and switches the main switch 8 of the vehicle height adjusting device to the manual side. As a result, the operation switch 5 to be operated outside the vehicle becomes effective. Then, the driver gets out of the cab, grasps the operation switch 5, and pushes the push button "U
The vehicle height is raised or lowered by operating "P" or "DOWN". If the operation of the operation switch 5 is stopped shortly before the height of the platform becomes just the height of the platform, the change in the height of the platform becomes gradual and the platform stops just at the height of the platform. As described above, when to stop the operation of the operation switch 5 can be easily learned by several trainings.

FIG. 3 is a schematic diagram of an apparatus according to an embodiment of the present invention.
It is a part control flowchart. That is, the driver operates
When the operation of the switch 5 is started, the control device is
Temporarily stop automatic control. And operation switch 5
Air pressure to the air suspension 1 according to the instructions
By supplying or exhausting air pressure,
Increase or decrease the height. Is the driver operating switch 5?
When you release your hand and the operation switch turns off,
The timer set inside the storage unit is t seconds (in this embodiment,
For 4 seconds), from the moment this timer times out
t₀ Vehicle height sensor for one second (one second in this embodiment)
Capture the detection output of 3. And this t ₀ Flatten the value of seconds
Performs averaging calculation and controls this as a new target value
Set to the device. This makes the platform height
Cargo handling work is performed in a state where it matches the height of the home. load
In principle, this control device works effectively during the service work period,
For example, the weight of the load is high and the height of the loading platform is low.
Then, the air pressure is automatically supplied to the air suspension.
The height of the loading platform is adjusted.

The time t of the timer can be set to an appropriate value depending on the structure of the air suspension control system. This is a matter of design choice.
If the time t is set long, the control target value can be set in a more stable state of vehicle height adjustment. However, the time t is the time when the driver or the like is about to start loading and unloading work of the luggage, and if it is too long, it may cause another situation such as the worker getting on the luggage carrier. However, it is not appropriate to make the length too long. Further, if the time t is short, the effect of the present invention is small, but even if this time t is shortened, a corresponding effect can be expected. Therefore, the time is set to a relatively short time before the change in the vehicle height completely subsides. Doing is also an option. From the results of various tests, it was appropriate to set the time t between 3 seconds and 5 seconds in the device of the present invention.

[0023]

As described above, in the apparatus of the present invention, the vehicle height is adjusted by the operation switch, and when the operation is completed, the air pressure in the pipeline of the air control system is stabilized after the time t has elapsed. In this state, the detection output of the vehicle height sensor is taken in, so phenomena such as overshoot are avoided, and the vehicle height suddenly changes at an unexpected time after entering adjustment control. The phenomenon disappears.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a structural diagram of an air suspension on the left side of the rear shaft.

FIG. 3 is a control flowchart of a main part of the apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1 air suspension 2 Air valve 3 height sensor 4 control device 5 operation switch 6 Air spring 7 Indicator light 8 main switch 9 Rotation sensor 10 air tanks 11 chassis 12 axles 13 Shock hub soba

Claims (2)

(57) [Claims] 1. An air suspension for supporting a chassis on an axle, an air valve for adjusting an air pressure supplied to the air suspension, a vehicle height sensor for detecting a distance of the chassis to the axle as a vehicle height, and this vehicle height sensor. A control device for automatically controlling the air valve so that the vehicle height is maintained at a target value by using the detection output of the control device, and an operation switch for vehicle height adjustment connected to the control device, wherein the control device is A vehicle height adjusting device including means for temporarily stopping the operation of the means for automatically controlling when the operation switch is operated and changing the air pressure according to an input of the vehicle height adjusting switch, wherein the control device is the When the vehicle height is changed according to the operation input of the operation switch, the operation height of the operation switch will be Vehicle height adjusting device, characterized in that it comprises means for setting the detection output of the vehicle height sensor after passage between t as a new target value. 2. The vehicle height adjusting device according to claim 1, wherein the time t is 3 to 7 seconds.