JP2003170720A - Lift axle device of front two-axle car - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase running fuel consumption by increasing grounding load of a driving wheel of a front two-axle car, improving starting performance, and suppressing rolling resistance of a wheel against a road surface. <P>SOLUTION: Relating to a lift axle device of the front two-axle car having a front front axle 6a, a front rear axle 6b, and at least one rear axle, a shock absorber 12 having a lift function capable of exhibiting a vibration buffer function using flow resistance of working fluid during normal running and suitably operating as a hydraulic cylinder by changing a hydraulic system is employed as a shock absorber to be disposed between the front rear axle 6b and a frame 2 side. The shock absorber 12 is operated by the working fluid distributed and guided from an oil pressure source for steering. The shock absorber 12 is contracted as the hydraulic cylinder in a light load state, thereby lifting up the front rear axle 6b on the frame 2 side. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lift axle device for a front two-axle vehicle.

[0002]

2. Description of the Related Art Generally, a front two-shaft / three-axle vehicle having a front front shaft and a front / rear shaft, and a rear shaft to which driving force is transmitted is applied to a large vehicle such as a truck.

FIG. 3 shows an example of a suspension device of a front two-shaft / three-axle vehicle having a front front shaft, a front / rear shaft, and a rear shaft. Reference numeral 1 in FIG. Axle wheel 2 indicates a frame of the front two-axle three-axle wheel 1, and a frame 2
The front end portion of the trailing leaf spring 4a is wound around the pin 5a and connected to the bracket 3a fixed to the front end portion of the front end portion of the trailing leaf spring 4a, and the front front shaft 6a is attached to the middle portion of the trailing leaf spring 4a. An air spring 7a is interposed between the upper surface of the rear end of the trailing leaf spring 4a and the lower surface of the frame 2.

The front end of a trailing leaf spring 4b is connected to a bracket 3b fixed to a position rearward of the bracket 3a at the front end of the frame 2 by winding a pin 5b around the front end of the trailing leaf spring 4b. A front and rear shaft 6b is attached to the middle portion, and an air spring 7b is interposed between the upper surface of the rear end portion of the trailing leaf spring 4b and the lower surface of the frame 2. There is.

Further, a front end of a trailing leaf spring 4c is wound around a pin 5c and connected to a bracket 3c fixed to the rear end of the frame 2, and a rear shaft is provided in the middle of the trailing leaf spring 4c. 6c is attached, and an air spring 7c is interposed between the upper surface of the rear end of the trailing leaf spring 4c and the lower surface of the frame 2.

By the trailing leaf springs 4a, 4b and 4c described above, the front front shaft 6a is provided.
And supports the front-rear, left-right, and torsional loads applied to the front-rear shaft 6b and the rear shaft 6c, and also supports the air springs 7
The a, 7b, and 7c support the vertical load applied to the front front shaft 6a, the front-rear shaft 6b, and the rear shaft 6c.

Incidentally, reference numerals 8a, 8b and 8c in FIG. 3 are sub-leaf springs which are superposed on the lower surface side of the trailing leaf springs 4a, 4b and 4c to form a double structure, and 9a is a front wheel. 9b is front and rear wheels, 9c
Is a rear wheel, 10a, 10b and 10c are shock absorbers, and 11a, 11b and 11c are lateral rods, respectively.

[0008]

However, in the front two-axle three-axle vehicle 1 as described above, traveling is always performed using all the front front wheels 9a, the front and rear wheels 9b, and the rear wheels 9c regardless of the load conditions. Therefore, in the case of the light load state, the load applied to the rear shaft 6c to which the driving force is transmitted becomes small, and the ground load of the rear wheel 9c as the driving wheel becomes small, especially at the time of starting the vehicle. There is a risk that the rear wheels 9c may slip and become unable to run.

Further, since the vehicle always travels using all the front wheels 9a, front and rear wheels 9b, and rear wheels 9c, there is a drawback that the rolling resistance of the wheels with respect to the road surface increases and the traveling fuel efficiency deteriorates. It was

The present invention has been made in view of the above-mentioned circumstances, and it is possible to improve the starting performance by increasing the ground load of the drive wheels and suppress the rolling resistance of the wheels with respect to the road surface to improve the running fuel consumption. The purpose of the present invention is to provide a lift axle device for a front two-axle vehicle.

[0011]

SUMMARY OF THE INVENTION The present invention is a lift axle device for a front two-axle vehicle comprising a front front shaft and a front and rear shaft, and at least one rear shaft, the space between the front and rear shafts and the frame side. As a shock absorber that should be installed in the vehicle, a shock absorber with a lift function that exhibits a vibration damping function that utilizes the flow resistance of hydraulic oil during normal traveling and that can be appropriately operated as a hydraulic cylinder by switching the hydraulic system is adopted. It is characterized in that the shock absorber is operated by operating oil which is branched from a hydraulic pressure source for steering.

When the vehicle is in a lightly loaded state and the hydraulic pressure from the steering hydraulic source is applied to the shock absorber to cause the contraction operation, the contraction operation of the shock absorber causes the front and rear shafts to move toward the frame side. As a result, the load applied to the axle to which the driving force is transmitted is increased, the ground load of the drive wheels is increased, slipping of the drive wheels at the time of starting, etc. is avoided, and the starting performance is improved. It will be.

Further, since the front and rear wheels are lifted up to the frame side together with the front and rear shafts, the rolling resistance of the wheels with respect to the road surface is reduced, so that the running fuel consumption is improved and the wear of the front and rear wheels is also reduced. Become.

Further, a shock absorber with a lift function, which can be appropriately operated as a hydraulic cylinder by switching the hydraulic system, is adopted, and the shock absorber with the lift function is diverted from a steering hydraulic power source for operation. Since it is operated by oil,
It is not necessary to separately install a mechanism or hydraulic power source for lifting up the front and rear axes.

Further, in practicing the present invention more concretely, for example, the hydraulic oil introduced between the engine-driven oil pump and the steering gear box via the flow dividing valve is constantly flowed and returned to the oil tank. In addition to providing a circulation line, a hydraulic control valve capable of switching between three positions of a hydraulic pressure supply state, a hydraulic pressure lock state, and a hydraulic pressure free state is provided in the middle of the hydraulic oil circulation line so that the shock absorber can contract when the hydraulic pressure is supplied. It is possible to employ a configuration in which the shock absorber and the hydraulic oil circulation line are connected via the hydraulic control valve.

With this configuration, when the vehicle is in a lightly loaded state, if the hydraulic control valve is switched to the hydraulic pressure supply state and hydraulic pressure is applied from the hydraulic oil circulation line to the shock absorber, the contraction operation is performed. The front and rear shafts are lifted up to the frame side due to the contraction operation of the shock absorber, and when the hydraulic control valve is switched to the hydraulic lock state in the lifted state, the front and rear shafts are lifted up to the frame side. When the hydraulic control valve is held, and then the hydraulic control valve is switched to the hydraulic free state, the shock absorber is extended by the weight of the front and rear axles and the front and rear wheels to lower the front and rear axles, whereby the normal front and rear wheels are grounded on the road surface. After returning to the running state, the shock absorber operates so as to exert its original vibration damping function using the flow resistance of hydraulic oil. That.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show an example of an embodiment for carrying out the present invention, and the parts denoted by the same reference numerals as those in FIG. 3 represent the same things.

The basic construction of this embodiment is substantially the same as that of the conventional front two-shaft / three-axle vehicle 1 shown in FIG. 3, except that the front-rear shaft 6b and the frame 2 side are characterized. As a shock absorber that should be provided between the shock absorber and the shock absorber, a shock absorber with a lift function that exerts a vibration damping function utilizing the flow resistance of hydraulic oil during normal traveling and can be appropriately operated as a hydraulic cylinder by switching the hydraulic system. 12 is adopted, and the shock absorber 12 is configured to be operated by the hydraulic oil that is branched from the hydraulic pressure source for steering and guided.

Here, the shock absorber 12 with a lift function is already well known in the art, and a valve mechanism in which the front and rear cylinder chambers partitioned by a piston are closed when a hydraulic pressure is applied. The valve mechanism is opened by the elastic force of the spring when the hydraulic pressure is set to a free state.
The front and rear cylinder chambers partitioned by the piston are in communication with each other.

Further, in the example shown here,
An engine driven oil pump 13 circulates hydraulic oil between a steering gear box 14 and an oil tank 15, and the oil tank 1
5 between the steering gear box 14 and the steering valve 1
The oil tank 1 is provided by constantly flowing the hydraulic oil introduced through 6.
A hydraulic oil circulation line 17 for returning to 5 is provided.

A hydraulic control valve 18 is provided in the middle of the hydraulic oil circulation line 17 and can be switched between three positions of a hydraulic pressure supply state, a hydraulic pressure lock state, and a hydraulic pressure free state. The hydraulic oil circulation line 17 and the shock absorber 12 are connected to each other.

Here, when the hydraulic control valve 18 is switched to the hydraulic pressure supply state (the right side position in FIG. 1), the hydraulic pressure is applied to the side where the shock absorber 12 contracts. When the valve 18 is switched to the hydraulic lock state (the central position in FIG. 1), the entry and exit of the hydraulic oil in the shock absorber 12 is locked, and the hydraulic oil on the hydraulic oil circulation line 17 side passes through the shock absorber 12. When the hydraulic control valve 18 is switched to the hydraulic free state (the left side position in FIG. 1),
All the flow passages on the hydraulic oil circulation line 17 side and the flow passages on the shock absorber 12 side are in communication with each other, and excess hydraulic oil is guided to the oil tank 15 side where the pressure is lowest.

Regarding switching of the hydraulic control valve 18, an engine control computer (ECU: Electr) is used.
onic control unit), which is appropriately performed by a switching command signal 19 from a control device 20. From this control device 20, the air springs 7a, 7b, 7
An air supply / discharge command signal 21 for instructing discharge and supply of air toward the air supply / discharge system of c (see FIG. 3 for the air spring 7c) is also output.

Further, to the control device 20, a vehicle speed signal 23 from a vehicle speed sensor 22 for detecting a vehicle speed and a pressure signal 25 from a pressure sensor 24 for detecting the air pressure of each of the air springs 7a, 7b, 7c. ON from the lift axle switch 26 that is manually operated by the driver
An OFF signal 27 and a stroke signal 29 from a stroke sensor 28 that detects the stroke of the shock absorber 12 are input (each sensor in the drawing is a model regardless of its original mounting position for convenience of description). Indicated).

A specific control procedure in the control device 20 will be described with reference to the flowchart of FIG. 2. First, in step S1, the vehicle speed of the front two-shaft / three-axle vehicle 1 and the air pressure of each of the air springs 7a, 7b, 7c. Each data regarding ON / OFF of the lift axle switch 26 and the stroke of the shock absorber 12 is grasped,
Next, in step S2, it is determined whether the stroke of the shock absorber 12 is extended or contracted, and in step S3, it is determined whether the lift axle switch 26 is on or off. Is to be done.

In the next step S4, it is determined whether or not the vehicle speed is equal to or lower than the set value, and it is determined whether or not the vehicle is substantially stopped (it is difficult to signal zero vehicle speed). Has become.

Here, the determination in step S4 is "N
In the case of "O", the procedure is returned to the start and the procedure from step S1 is repeated. However, in the case of "YES", the process proceeds to the next step S5, and the loading rate is set below the set value. The judgment is made whether the value is greater than or equal to the value.

Regarding the loading ratio, the loading load is estimated based on the pressure signal 25 from the pressure sensor 24 which detects the air pressure of each air spring 7a, 7b, 7c, and based on the estimated loading load. It is designed to be calculated in the control device 20.

Based on the results of the determination in steps S2 to S5, the stroke of the shock absorber 12 is extended, the lift axle switch 26 is on, the vehicle is stopped, and the load factor is less than the set value. If it is determined that the suspension function is stopped in step S6, specifically, the air discharge to the air supply / discharge system of each air spring 7a, 7b, 7c is instructed. The air supply / discharge command signal 21 is output.

In this way, each air spring 7a,
As soon as air begins to be discharged from 7b and 7c, the hydraulic pressure control valve 1 is activated by the switching command signal 19 in the next step S7.
8 is switched to the hydraulic pressure supply state, whereby the shock absorber 12 contracts as a hydraulic cylinder, and in the next step S8, it is confirmed that the stroke of the shock absorber 12 has reached the upper limit (target value). Then, the control ends in step S9, and the switching command signal 1
The hydraulic control valve 18 is switched to the hydraulic lock state by 9 and the stroke of the shock absorber 12 is locked.

On the other hand, based on the determination results of steps S2 to S5, the stroke of the shock absorber 12 is shortened, the lift axle switch 26 is off, the vehicle is stopped, and the loading ratio is equal to or greater than the set value. If it is determined that there is, a step S6 is taken to restore the suspension function, and specifically, the supply of air toward the air supply / discharge system of each air spring 7a, 7b, 7c is instructed. The air supply / discharge command signal 21 is output.

In this way, each air spring 7a,
As soon as air starts to be supplied to 7b and 7c, the hydraulic pressure control valve 18 is activated by the switching command signal 19 in the next step S7.
Is switched to the hydraulic pressure free state, and the shock absorber 12 which lost the action of the hydraulic pressure by this is moved to the front and rear shafts 6.
b and the weight of the front and rear wheels 9b and the air springs 7a, 7
It is lowered by the return of b and 7c, and in the next step S8,
When it is confirmed that the stroke of the shock absorber 12 has reached the lower limit value (target value) corresponding to the standard vehicle height (step S8 can be skipped when the shock absorber 12 descends), the control ends in step S9,
The hydraulic free state of the hydraulic control valve 18 is maintained as it is.

The determination that the loading rate is equal to or greater than the set value in step S5 has priority over the condition that the lift axle switch 26 is on. Switch 26
Even if is turned on, if the load factor is equal to or greater than the set value, a step S6 is taken to restore the suspension function, and the switching command signal 19 is used to bring the hydraulic control valve 18 into the hydraulic free state in step S7. Is switched,
The shock absorber 12 is lowered.

When the lift axle device is driven by the control device 20 as described above, the control is performed when the driver turns on the lift axle switch 26 while the vehicle is in a lightly loaded state and the vehicle is stopped. By the air supply / discharge command signal 21 from the device 20, each of the air springs 7a, 7a
While the air is discharged from b and 7c, the hydraulic control valve 18 is switched to the hydraulic pressure supply state by the switching command signal 19 from the control device 20, and the hydraulic pressure is applied from the hydraulic oil circulation line 17 to the shock absorber 12, The shock absorber 12 is contracted so that the shock absorber 1
The front-rear shaft 6b is lifted up to the frame 2 side by the contraction operation of 2, and the hydraulic control valve 18 is switched to the hydraulic lock state in the lift-up state, and the front-rear shaft 6b is lifted up to the frame side. Retained.

As a result, the rear shaft 6c to which the driving force is transmitted
(See FIG. 3) The load applied to the rear wheels 9c (see FIG. 3) as a drive wheel is increased, and the ground load of the rear wheels 9c (see FIG. 3) is increased. The starting performance will be improved.

Further, since the front and rear wheels 9b are lifted up to the frame 2 side together with the front and rear shafts 6b, the rolling resistance of the front and rear wheels 9b with respect to the road surface is reduced, so that the running fuel consumption is improved and the front and rear wheels 9b are worn. Will also be reduced.

Further, when the vehicle is stopped with the loading rate exceeding the set value due to a new load or the like, the air supply / discharge command signal 21 from the control device 20 causes the respective air springs 7a,
While the air is supplied to 7b and 7c, the hydraulic control valve 18 is switched to the hydraulic free state by the switching command signal 19 from the control device 20, and the shock absorber 12 causes the weight of the front and rear shafts 6b and the front and rear wheels 9b and each air spring. 7a, 7
By the return of b and 7c, it extends and the front and rear shaft 6b is lowered,
As a result, the front and rear wheels 9b return to the normal traveling state in which they are in contact with the road surface, and the shock absorber 12 operates so as to exert its original vibration damping function utilizing the flow resistance of the hydraulic oil.

Therefore, according to the above embodiment, the ground load of the rear wheel 9c as the drive wheel can be increased, so that the starting performance can be greatly improved as compared with the conventional case and the front and rear wheels 9b with respect to the road surface. The rolling resistance can be reduced to improve the running fuel efficiency and the wear of the front and rear wheels 9b can be reduced.

Further, a shock absorber 12 with a lift function, which can be appropriately operated as a hydraulic cylinder by switching the hydraulic system, is adopted, and the shock absorber 12 with a lift function is diverted from the hydraulic pressure source for steering and guided. Since it is operated with the hydraulic oil, it is not necessary to separately install a mechanism or hydraulic power source for lifting up the front-rear shaft 6b, and the cost required for implementing the lift axle device can be significantly reduced. it can.

The lift axle device for a front two-axle vehicle according to the present invention is not limited to the above-mentioned embodiment, but includes front and rear shafts and a rear shaft to which driving force is transmitted. The present invention is not limited to the front two-shaft three-axle vehicle provided, but can be similarly applied to the front two-axis four-axle vehicle in which the front two-axis and the rear two-axis are arranged. It goes without saying that various changes can be made without departing from the scope.

[0042]

According to the lift axle device for a front two-axle vehicle of the present invention described above, various excellent effects as described below can be obtained.

(I) Since the ground load of the drive wheels can be increased, the starting performance can be greatly improved as compared with the conventional one, and the rolling resistance of the front and rear wheels with respect to the road surface can be reduced to improve the running fuel consumption. It is possible to reduce wear on the front and rear wheels.

(II) A shock absorber with a lift function, which can be appropriately operated as a hydraulic cylinder by switching the hydraulic system, is adopted, and the shock absorber with a lift function is diverted from the hydraulic pressure source for steering. Since it is operated by hydraulic oil, it is not necessary to separately install a mechanism or hydraulic power source for lifting up the front and rear shafts, and the cost required for implementing the lift axle device can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a system diagram schematically showing an example of an embodiment for carrying out the present invention.

FIG. 2 is a flowchart showing a specific control procedure by the control device of FIG.

FIG. 3 is an overall side view showing an example of a conventional suspension device for a front two-axle three-axle vehicle.

[Explanation of symbols]

1 front two-axis three-axis vehicle (front two-axis vehicle) 2 frames 6a front front axis 6b Front-rear axis 6c rear axle 12 Shock absorber with lift function 13 Oil pump 14 Steering gear box 15 oil tank 16 shunt valve 17 Hydraulic oil circulation line 18 Hydraulic control valve

Claims (2)

[Claims] 1. A lift axle device for a front two-axle vehicle comprising a front front shaft and a front and rear shaft, and at least one rear shaft, the shock absorber being provided between the front and rear shafts and the frame side. A shock absorber with a lift function that exhibits a vibration damping function that utilizes the flow resistance of hydraulic oil during normal running and that can be operated appropriately as a hydraulic cylinder by switching the hydraulic system is adopted, and the shock absorber is used for steering hydraulic pressure. A lift axle device for a front two-axle vehicle, characterized in that it is configured to be operated by hydraulic oil that is diverted from the source. 2. A hydraulic oil circulation line for constantly flowing hydraulic oil introduced between an engine-driven oil pump and a steering gear box via a diversion valve to return the hydraulic oil to an oil tank, and in the middle of the hydraulic oil circulation line. A hydraulic control valve capable of switching between three positions of a hydraulic pressure supply state, a hydraulic pressure lock state, and a hydraulic pressure free state is provided, and the shock absorber and the hydraulic oil circulation line are connected to the hydraulic control valve so that the shock absorber can contract when hydraulic pressure is supplied. The lift axle device for a front two-axle vehicle according to claim 1, wherein the lift axle device is connected via