JP2000344076A - Braking device for dump truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the slip of front wheels during steering operation. SOLUTION: This braking device which has front and rear brakes 1, 2 for braking the front and rear wheels 3, 4 of a dump truck and a brake controller 13 for controlling the front and rear braking forces BF, BR of the front and rear brakes 1, 2 includes a turning angular speed detector 6 for detecting an angular speed (w) in steering a hand wheel 5. The brake controller 13 reduces the front braking force BF, when the angular speed (w) is a preset angular speed (w1) or over, with the greater angular speed (w) leading to the more reduction amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake device for a dump truck.

[0002]

2. Description of the Related Art It has been known that a wheel slips when a turning operation is performed while a vehicle is braking. An example of a technique for preventing this is disclosed in, for example, JP-A-10-203333.
According to the publication, when braking is performed during a sharp turn, the lateral force of the inner rear wheel, which is dominant with respect to the rotation moment of the vehicle, decreases. Then, the decrease in the lateral force greatly affects the rotation moment, and oversteering occurs. In order to prevent this, in this publication, the slip ratio of the wheels is measured, and the brake pressure applied to the rear wheels is reduced based on the slip ratio.

[0003]

However, the prior art disclosed in the above publication has the following problems.

[0004] A concept of a friction circle, which is determined by a wheel and a condition of a road surface, is known as an expression of the friction capability of a wheel. FIG. 4 shows an example of the friction circle 18 of the front wheel. Note that the friction circle 18 is generally not necessarily a perfect circle, but is here represented by a perfect circle for the sake of explanation. At this time, the friction circle 18
Of the friction circle 18 from the center of the friction circle 18 is represented as a radius m of the friction circle 18. In driving a dump truck, a retarder brake is applied for a long time to reduce the speed when traveling on a downhill. As a result, the front brake force B indicated by an arrow in the drawing is applied to the front wheels.
F is applied. When the vehicle is turned by operating the steering wheel during the braking, a turning force S by the steering is applied to the front wheels, and the turning force S and the front braking force BF are applied.
Is applied to the front wheels. When the resultant force T becomes larger than the radius m of the friction circle 18 and the leading end of the resultant force T exceeds the outer circumference 19, a force exceeding the friction performance acts on the front wheel, and the front wheel slips. Therefore, there is a problem that slip cannot be prevented even if the brake pressure on the rear wheels is reduced.

If the brake pressure on the rear wheels is reduced while the retarder brake is being applied, the total braking force (sum of the front braking force and the rear braking force) applied to the vehicle is reduced. Truck speed increases. In addition, there is a problem that a slip easily occurs.

The present invention has been made in view of the above problems, and has as its object to provide a brake device for a dump truck in which the front wheels do not slip during steering operation.

[0007]

Means for Solving the Problems, Functions and Effects In order to achieve the above object, a first invention is to provide a front and rear brake for braking the front and rear wheels of a dump truck, respectively, and a front and rear braking force of the front and rear brakes. In a brake device for a dump truck having a brake controller for controlling a steering wheel, a turning angular velocity detector for detecting an angular velocity when operating a steering wheel is provided, and the brake controller is configured to apply a pre-braking force when the angular velocity is equal to or higher than a predetermined angular velocity. Has been reduced.

According to the first aspect, the pre-braking force is reduced when the angular velocity is equal to or higher than the predetermined angular velocity.
When the steering operation is performed at a speed higher than a certain angular velocity (that is, a steep operation), the magnitude of the turning force cannot be ignored relative to the magnitude of the front braking force, and the resultant force becomes larger than the radius of the friction circle. Slip is likely to occur.
Therefore, by reducing the pre-braking force at the time of steering operation larger than the predetermined angular velocity, it is possible to prevent the slip by making the resultant force smaller than the radius of the friction circle.

According to a second aspect of the present invention, in the brake device for a dump truck according to the first aspect, the brake controller increases the amount of decrease in the front braking force as the angular velocity ω increases.

According to the second aspect, the larger the angular velocity, the larger the amount of decrease in the front braking force. That is, as the driver performs the steering operation more quickly, the turning force applied to the front wheels increases, and the resultant force also increases. Therefore, in order to prevent the slip by making the resultant force smaller than the radius of the friction circle at this time, the amount of decrease in the front braking force must be increased. Thereby, the slip of the front wheels can be reliably prevented.

According to a third aspect of the present invention, there is provided the dump truck brake device according to the first or second aspect, further comprising an operation amount detector for detecting an operation amount of a brake operation means for operating the front and rear brakes. The total braking force is determined based on the manipulated variable, and the rear braking force is increased so that the sum of the front and rear braking forces always becomes the total braking force as the front braking force decreases. .

According to the third aspect, the total braking force is determined based on the operation amount of the brake (for example, the operation angle of the retarder lever), and the sum of the front and rear braking forces becomes the total braking force. The front and rear braking force is determined. That is, since the amount of decrease in the front braking force is increased by increasing the rear braking force so that the total braking force is constant, slip can be prevented while always performing the deceleration intended by the driver, Driving the vehicle increases stability.

[0013]

FIG. 1 shows a configuration diagram of a dump truck according to an embodiment. In the figure, the dump truck includes a front wheel 3 that can be turned within a predetermined range, a rear wheel 4 that is driven, a handle 5 that turns the front wheel 3, a turning angular speed detector 6 that detects an operating angular speed of the handle 5, and ,
And a braking device. The brake device of the dump truck supplies brake oil to the front brake 1 and the rear brake 2 for braking the front wheel 3 and the rear wheel 4, respectively, and the front and rear hydraulic cylinders (not shown) of the front and rear brakes 1 and 2. A hydraulic pressure source 7, a retarder lever 8 for operating a retarder brake, a brake pedal 9 for operating a service brake, and a brake controller 13 for controlling a brake device.

The retarder lever 8 and the brake pedal 9 are connected to angle detectors 17, 17 for detecting their operation angles θr, θs, respectively.
Reference numeral 17 is electrically connected to the brake controller 13. The turning angular velocity detector 6 is also electrically connected to the brake controller 13. The hydraulic power source 7 and the front and rear brakes 1 and 2 are connected by front and rear brake pipes 14 and 15, respectively. Each of the front and rear brake pipes 14 and 15 is bifurcated and merges at the shuttle valve 16 via the front and rear retarder proportional operation valves 10 and 11 and the front and rear service proportional control valves 22 and 23, respectively. Has been reached.

The front and rear retarder proportional control valves 10 and 11 and the front and rear service proportional control valves 22 and 23 are electrically connected to a brake controller 13. The front and rear retarder proportional control valves 10 and 11 output brake oil having a front and rear retarder brake pressure substantially proportional to the front and rear retarder currents iF and iR output from the brake controller 13. Further, the front and rear service proportional control valves 22 and 23 output the brake oil of the front and rear service brake pressure substantially proportional to the front and rear service currents JF and JR output from the brake controller 13. The brake fluid output from the front and rear retarder proportional control valves 10 and 11 and the front and rear service proportional control valves 22 and 23 is
After passing through the front and rear brake pipes 14 and 15, respectively, they merge at the shuttle valves 16 and 16. Then, the brake oil of the larger one of the front and rear retarder brake pressure and the front and rear service brake pressure is applied to the front and rear brakes 1 and 2 by the shuttle valves 16 and 16.

At this time, hydraulic pressure detectors 21 and 21 are provided in the front and rear brake pipes 14 and 15 to monitor the front and rear brake pressures, and the detection signals are input to the brake controller 13. Therefore, the brake controller 13 can control the front and rear brake pressure applied to the front and rear brakes by controlling the front and rear retarder currents iF and iR based on the detection signals of the hydraulic pressure detectors 21 and 21. The braking forces BF and BR applied to the front and rear brakes 1 and 2 are proportional to the front and rear brake pressures, respectively.
Are the front and rear braking forces BF, B applied to the front and rear brakes
It is possible to control R to a substantially desired value.

Hereinafter, when the steering operation is performed while decelerating while operating the retarder lever 8, the brake controller 13 controls the front-rear braking force BF, BR.
Will be described with reference to the flowchart shown in FIG. Hereinafter, in the flowchart, each step number is denoted by adding S. In the following description, for simplicity, a case where the driver does not operate the brake pedal 9 but operates only the retarder lever 8 will be described. That is, the front-rear brake pressure is equal to the front-rear retarder brake pressure.

First, the brake controller 13 detects an operation angle θr at which the driver operates the retarder lever 8 based on a detection signal of the angle detector 17 (S1). Then, the total braking force BN is determined by a predetermined calculation based on the operation angle θr (S2), and the total braking force BN becomes the front-rear braking force BF, BR based on a predetermined distribution ratio. It is distributed to the front and rear brakes 1 and 2 (S3). Next, the brake controller 13 determines whether or not the steering wheel 5 is operated based on the output signal of the turning angular velocity detector 6 (S4), and if not, returns to S1.

If the steering wheel 5 has been operated in S4, the brake controller 13 calculates an angular velocity ω for operating the steering wheel 5 based on the output signal of the turning angular velocity detector 6 (S5). And this angular velocity ω
The predetermined front-rear turning coefficients KF, KR to be multiplied by the front-rear braking forces BF, BR are determined based on (S6). Then, the front and rear braking forces BF and BR are changed to be the front braking force (KF · BF) during turning and the rear braking force (KR · BR) during turning, respectively, and these are changed to the front and rear brakes 1 and 2. It is allocated (S7). Then, the process returns to S1.

The braking force before and after this turning (KF · B
F), front and rear turning coefficient KF for deriving (KR / BR),
KR is determined, for example, as follows. FIG. 3 shows an example of a graph of the relationship between the angular velocity ω and the front-rear turning coefficients KF and KR. In the figure, the vertical axis represents the front-rear turning coefficient KF,
KR, and the horizontal axis is the angular velocity ω. As shown in the figure, when the angular velocity ω is equal to or less than the first predetermined angular velocity ω1, the front-rear turning coefficients KF and KR are both 1. When the angular velocity ω becomes equal to or more than the first predetermined angular velocity ω1, the rear turning coefficient KR is increased substantially linearly and the front turning coefficient KF is decreased substantially linearly with respect to the angular velocity ω. When the angular velocity ω becomes equal to or more than the second predetermined angular velocity, the rear turning coefficient KR = KR
1 (constant), and the front turning coefficient KF = KF1 (constant).

The front turning coefficient KF and the rear turning coefficient K
When determining R, the relationship as shown in the following Expression 1 is always satisfied. BN = BF + BR = KF · BF + KR · BR (1) That is, the total braking force BN determined based on the operation amount θr of the retarder lever 8 is not changed, and the predetermined total braking force BN is changed. I always try to get it. At this time, KF1 may be 0 in some cases. That is,
The braking force before turning (KF · BF) may be set to 0, and the braking force after turning (KR · BR) = the total braking force BN.

As described above, according to the present embodiment,
When the steering wheel 5 is operated at an angular velocity equal to or higher than the first predetermined angular velocity ω1 during braking, the front braking force BF is reduced and the rear braking force BR is increased. As a result, the resultant force T of the turning force S applied to the front wheel 3 and the front braking force BF during turning becomes smaller than the radius m of the friction circle 18 of the front wheel 3, so that the front wheel 3 can be prevented from slipping. Further, the distribution ratio of the front and rear braking forces BF and BR during turning is determined based on the angular velocity ω of the steering wheel 5, and the higher the angular velocity ω, the lower the front braking force BF. In other words, as the driver performs a steer steering operation, a larger turning force is applied to the front wheel 3 and the possibility that the front wheel 3 slips increases. Therefore, in such a case,
Since the front braking force BF is made smaller so that the resultant force T does not exceed the radius m of the friction circle 18 of the front wheel 3,
Slip can be reliably prevented.

Further, the turning distribution ratio is determined without changing the total braking force BN determined based on the operation angle of the retarder lever. Therefore, the total braking force BN is always ensured, so that the braking force intended by the driver can be obtained, and the required deceleration can be obtained.

In the above description, the operation of the retarder brake has been described, but the present invention is similarly effective for the service brake. Further, although the drive wheels are rear wheels, the present invention is similarly effective for front-wheel drive and four-wheel drive vehicles.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a dump truck according to an embodiment.

FIG. 2 is a flowchart of a procedure for controlling a longitudinal braking force.

FIG. 3 is a graph showing a relationship between an angular velocity and a front-rear turning coefficient.

FIG. 4 is an explanatory diagram showing an example of a friction circle of a front wheel.

[Explanation of symbols]

1: front brake, 2: rear brake, 3: front wheel, 4: rear wheel, 5: steering wheel, 6: turning angular velocity detector, 7: hydraulic pressure source, 8: retarder lever, 9: brake pedal, 10:
Front retarder control valve, 11: Rear retarder control valve, 12: Body, 13: Brake controller, 14: Front brake piping, 15: Rear brake piping, 16: Shuttle valve, 1
7: Angle detector, 18: Friction circle, 19: Outer circumference, 21: Oil pressure detector, 22: Front service proportional control valve, 23: Rear service proportional control valve.

Claims (3)

[Claims] 1. A front-rear brake (1,2) for braking front and rear wheels (3,4) of a dump truck, and a front-rear braking force (BF, BR) of the front-rear brakes (1,2) are controlled. In a brake device for a dump truck having a brake controller (13), a turning angular velocity detector (6) for detecting an angular velocity (ω) for operating a handle (5) is provided, and the brake controller (13) A brake device for a dump truck, wherein the front braking force (BF) is reduced when (ω) is equal to or higher than a predetermined angular velocity (ω1). 2. The dump device according to claim 1, wherein the brake controller (13) increases the amount of decrease in the front braking force (BF) as the angular velocity (ω) increases. Truck braking device. 3. An operation amount detector for detecting an operation amount (θr, θs) of a brake operation means (8) for operating a front-rear brake (1, 2) in the brake device for a dump truck according to claim 1 or 2. (17, 17), and the brake controller (13) controls the detected operation amount (θr,
θs), the total braking force (BN) is determined, and the front-back braking force (BF,
A braking device for a dump truck, wherein the rear braking force (BR) is increased so that the sum of the braking force (BR) always becomes the total braking force (BN).