JPS5820820B2 - Vehicle brake control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake control device for a vehicle, mainly for automobiles, particularly trucks, etc., which distributes braking force to front wheels and rear wheels as best as possible according to the load on the vehicle.

Generally, when braking a car, if only the front wheels are locked by 7% (the wheels slide on the road without rotating), the vehicle will flow in the direction of the tangential force when turning, and if only the rear wheels are locked, the car will turn irregularly. This is extremely dangerous as it may cause the vehicle to become inoperable.

That is, it is ideal that the braking force be distributed to the front wheels and the rear wheels so that all four wheels are always locked at the same time.

However, in an automobile, the distribution ratio of the load applied to the front and rear wheels usually varies depending on various conditions, so it is generally extremely difficult to set the braking force so that all four wheels are always locked at the same time.

In particular, in trucks, the load distribution ratio varies dramatically between when the vehicle is empty and when it is loaded, so if the distribution of braking force is adjusted in advance to the loaded condition, early rear wheel lock occurs when the truck is empty, and it is adapted to the condition when the truck is empty. This is inconvenient because the front wheels rank early and the braking force is insufficient.

Conventionally, in passenger cars with small load fluctuations, when the oil pressure to the rear wheel cylinder reaches a predetermined value (this is called the oil pressure control point) in order to prevent the highly dangerous rear wheel from locking, the oil pressure is stopped. A relatively simple pressure control valve is used to reduce the rate of climb, but on trucks with extreme load fluctuations a mechanism is used to further vary the hydraulic control point of the pressure control valve in response to the load on the rear wheels. load-responsive hydraulic control device (hereinafter referred to as Load Sensing)
Pr.

Portioning is abbreviated as LSP control device.
This valve is called an LSP valve.

) is used. However, this LSP control device does not directly utilize the vehicle load, but rather applies the relative displacement that occurs between the rear axle and the frame due to that load to one end of a single rod dog spring with linear characteristics. Since the actuation force corresponding to the above-mentioned relative displacement is transmitted to the LSP valve via the dog spring to correct the hydraulic control point for rear wheel braking, the control action does not match the actual size and the effect is sufficient. There was a drawback that it was not.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide a vehicle brake control device that can always be expected to achieve good braking force distribution close to simultaneous locking of all four wheels in response to changes in payload.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a frame near the rear wheel of the vehicle, 2 is an LSP valve fixed to the frame 1 (details will be described later), and 38 is a piston pin protruding from LSPS2O2.

On the other hand, 3 is a rear axle housing, and the rear wheel 1
0 on the road surface, and is configured to be movable relative to the frame 1 via a rear suspension (not shown) consisting of stacked plates and the like.

A shackle bracket 4 is fixed to a part of the rear axle housing 3, and a rigid shackle 5 is pivotally attached to one end of the shackle bracket.

Reference numeral 6 denotes a slightly curved frame cutout for load response, one end of which is rotatably pivoted to a bracket 7 fixed to the frame 1 with a pin 8, and the other end is connected to the free end of the rigid shackle 5. It is connected to

For reference, in the above configuration, in the conventional hydraulic control mechanism, the load response spring 6 was in direct contact with the LSPS2O2 stomp pin 38 at a location near the pivot point □8 on the bracket 7. Then, a relative displacement H that occurs between the rear axle housing 3 and the frame 1 mainly in the vertical blade direction due to a change in the loaded weight is applied to one end of the spring 6, and an action corresponding to the displacement is caused by the linear spring characteristic of the spring 6. The power reached LSPS2O2.

In the embodiment of the invention described herein, LSPS2
In order to improve the spring characteristics of the transmission member for transmitting O2 to a non-linear type, an auxiliary member 9 is interposed between the spring 6 and the piston pin 38.

That is, this auxiliary member 9 has a U-shaped cross section so that the inner surface of its back portion 9a can be successively engaged with substantially the left half of the stick spring 6 in the drawing, and the auxiliary member 9 forms a dog with a U-shaped cross section so that it can be successively engaged with the substantially left half of the stick spring 6 in the drawing, and the base of the left end in the drawing is attached to the bracket 7. It is rotatably attached together with the spring 6 by the aforementioned pin 8, and a part of the outer surface of its back portion 9a is in contact with the piston pin 38.

Note that the curved shape of the back portion 9a of the auxiliary member 9, which should be successively engaged with the spring 6 as the spring 6 deflects, is different from that in the case where the spring 6 is deflected alone due to the above-mentioned relative displacement caused by a change in the load. In order to control the pushing force exerted on the piston pin 38 not in a directly proportional manner, but in an appropriate manner not only during light loads but also in all ranges where the load changes, the curvature is different from the curvature when the spring 6 deflects alone. It is formed.

Note that the shape of this auxiliary member 9 is determined depending on the specifications of the vehicle, so it is not limited to the shape illustrated in this embodiment.

Next, the structure and operation of the aforementioned LSPS2O2, that is, the load responsive hydraulic control valve, will be explained.

In FIG. 2, 21 is a LSPS2O2 cylindrical box-shaped casing, the interior of which is separated by a partition plate 22 between an upper chamber 23 and a main chamber 2.
It is divided into 4 parts.

Reference numeral 25 denotes a valve body whose valve leg 26 is inserted into a valve hole 27 at the center of the partition plate 22, and the upper side thereof is pressed by a coil spring 28 to close the valve.

29 is a large-diameter piston that fits into the upper inner circumferential surface of the main chamber 24, and 30 is a small-diameter piston, which is a concentric cylindrical wall body 3 that protrudes into the main chamber 24 from the bottom plate portion 21a of the casing 21.
It fits into the inner peripheral surface of No.3.

Reference numeral 31 denotes an intermediate stem connecting the large-diameter piston 29 and the small-diameter piston 30, and these three members can move up and down in the main chamber 24 as a unit (hereinafter, these three members are collectively referred to as the piston body 32).

) Now, in the main chamber 24, the space above the large diameter piston 29 is called the middle chamber 24a, and the space below the large diameter piston 29 is called the lower chamber 24b.
In other words, 34 is a flow path that communicates the upper chamber 23 and the lower chamber 24b, 35 is an oil inlet/output path in the middle chamber 24a and is connected to a rear wheel cylinder (not shown), and 36 is a flow path that communicates the upper chamber 23 and the lower chamber 24b.
It is connected to a mask cylinder (not shown) through an oil inlet/outlet passage at 4b.

A coil 37 is installed between the large-diameter piston 29 and the casing bottom plate 21a and acts to push the piston body 32 toward the upper blade shown in the figure. The passage 35 is not closed, and when the large diameter piston 29 reaches a position close to the uppermost position, it contacts the valve foot 26 and pushes up the valve body 25, thereby opening the valve 25.

38 is the aforementioned piston, which is fixed to the lower surface of the small-diameter piston 30, penetrates the bottom plate portion 21a of the casing 21, projects to the lower blade shown in the figure, and is connected to the spring 6 via the auxiliary member 9.
maintain contact with.

Now, in order to make this LSPS2O2 application easier to understand, the ideal distribution line of braking force will be described.

If no hydraulic control valve is installed in the hydraulic conduit from the mask cylinder to the front and rear brake cylinders, the front wheel braking force (or the same oil pressure) Ff and the rear wheel braking force (or the same oil pressure) Fr is equal, and the relationship is usually expressed by a straight line with a slope of 45°, as shown by the OD line in FIG.

However, in reality, applying the brakes while the vehicle is moving produces an effect similar to that of moving the center of gravity of the vehicle, including its cargo, forward, and the front wheel load during deceleration is proportional to the total weight and deceleration. The rear wheel load increases by the same amount of load movement compared to when it is at rest, and conversely, the rear wheel load decreases by the same amount of load movement.

If we draw the ideal braking force distribution line for the front and rear wheels, that is, the four-wheel simultaneous lock curve, in Figure 3, assuming such an event and simultaneous locking of all four wheels, for example, when the car is empty, curve a, when the load is constant, curve b, and in the middle. When loading the amount, the curve c (-fl
J) is known to occur.

In other words, the braking force distribution according to the above-mentioned OD straight line does not suit the actual situation, and at least this straight line is
BF, refracted like CG line to ideal distribution lines a, b, c
required to be close to.

In short, a hydraulic control device including an LSP valve performs this function.

Subsequently, the operation and effects of the embodiment will be explained with reference to figures.

First, in the LSP valve 2 shown in FIG. 2, the cross-sectional areas of the large-diameter piston 29, stem 31, and small-diameter piston 30 are respectively set as So and S2°S3, and the elastic force of the coil spring 37 is applied to F2 and the piston pin 38. Let Fl be the pushing force acting from the external spring 6 or the like.

Here, if it is assumed that there is no vertical displacement between the frame 1 and the rear axle housing 3 when the vehicle is empty, and that Fl-0, then this LSP valve 2 will act as a valve body when the oil pressure in its casing 21 is lower than a certain set value. 25 is in the open position.

When the brake pedal is started to be depressed under this condition, the hydraulic pressure Pm of the mask cylinder is transmitted from the lower chamber 24b through the flow path 34 to the upper chamber 23, and from the upper chamber 23 via the middle chamber 24b, it is directly transmitted to the wheel cylinder. .

At this time, in order to maintain the valve body 25 in the open state, the push-up force acting on the piston body 32 (the left side of the equation below) is greater than or equal to the push-down force (the right-hand side of the equation below), so the following equation holds true.

pm (St S 2 ) + F 2 ≧ Pm S 1
+ Pm (S, -Sρ) Putting this in order, in other words, when the car is empty, the oil pressure Pm for which formula (1) holds true is
The valve body 25 is open in the range of , and the oil pressure Pm of the mask cylinder directly acts on the rear wheel cylinder.

When the brake pedal is depressed even more strongly and the oil pressure Pm rapidly rises to reach the condition described below, the piston body 32 moves downward, the valve body 25 is pushed by the coil spring 28, and the valve passage 27 is closed. The following relational expression holds true.

Here, Pw is the hydraulic pressure that communicates from the middle chamber 24a to the rear wheel cylinder.

PwS1+Pm(S3-82)=Pm(SI S2)
+F2 By rearranging and differentiating this, when the oil pressure Pm of the mask cylinder reaches a value that satisfies the equation (2) set for the empty vehicle state and the valve passage 21 is closed, from then on, equation (4) is shown. Thus, the rear wheel cylinder oil pressure Pw is equal to the mask cylinder oil pressure Pm - which is equal to the front wheel cylinder oil pressure.

In FIG. 3, the oil pressure distribution line 1-S for the empty car condition distributes the oil like the AE line that connects the set oil pressure control points A to 3 with the slope.

The AE line is much closer to the ideal distribution line a than the AD line without LSP.

Next, when in a loaded state, the external spring 6 is added to the above relational expression.
Pushing force F1 transmitted to the piston 38 from etc. is applied, and the valve body 2
The conditional expressions before and after the hydraulic control point where 5 closes are as follows for equations (1) and (2) when the vehicle is empty.

Before the valve is closed After the valve is closed, that is, the hydraulic pressure at the hydraulic control point (at the hydraulic control point) changes according to the relative displacement due to the increase in the loaded weight, and according to the increase in the pushing force F1 transmitted from the rear axle housing 3 to the piston pin 38 via the spring 6 etc. In FIG. 3, the bending point of the hydraulic pressure distribution line rises above the AD line.

The term of the pushing force F1 is also added to the relational expression after the hydraulic control point where the equation (2)' holds true, resulting in the following equation (3)'.

If we differentiate and compare Equation (4) and Equation (4)' and -, we can see that the hydraulic pressure distribution ratio Pw after the hydraulic pressure control point is the same when loaded as when empty. The slope of the distribution line does not change, so the hydraulic pressure distribution line for the constant volume state is expressed by equation (1)'
From point B, where the equation is satisfied, it is refracted parallel to the AE line like the BF line, and the state is close to the ideal distribution line.

In other words, the values of the inflection points A and B for an empty vehicle and a constant volume prison can be set as extreme values based on the specifications of the vehicle;
For loading conditions with intermediate loads that change, the value of the intermediate bending point cannot be uniquely determined and compensated for with the conventional single spring 6, so it is optimally approximated to the ideal distribution line for simultaneous locking of four wheels. Not necessarily.

On the other hand, in the embodiment of the present invention, the right end joint portion 6a of the spring 6 in the drawing changes relative to the frame 1 together with the rear axle housing 3 due to a change in the loaded weight, and the spring 6 moves to the upper blade in the drawing. When the spring 6 is deflected, the left part of the spring 6 in the figure gradually adapts to the inner surface of the back part 9a of the auxiliary member 9, and the right end of the engaging part of both moves to the right in the figure.
The pushing force F1 received by the piston pin 38 does not change in direct proportion to the above-mentioned relative displacement of the rear axle housing 3, and the curved shape of the auxiliary member 9 relative to the spring 6 is changed to 17 at the same time on all four wheels.
9. By appropriately determining the change in the curve, it is possible to take the inflection point C that is optimally close to the ideal distribution line C in Fig. 3 even for an intermediate amount of loaded dog. .

That is, by intervening the auxiliary member 9, if the spring characteristics of the transmission member that absorbs the effect of relative displacement on the LSPS2O2 are improved to an appropriate curved shape, the pushing force F1 exerted on the LSPS2O2 stompin 38 will be as close to the ideal as possible. The relationship between the relative displacement amount H and the inflection point oil pressure P becomes a smooth curve like the line i in FIG. It is possible.

Incidentally, the straight line ii in FIG. 4 shows the same relation line based on a conventional single spring, which lacks compatibility.

In short, the present invention provides a hydraulic control valve (LSP valve) provided in the frame of the vehicle to control the braking hydraulic pressure applied to the rear wheel cylinder in correlation with the load received by the rear wheels in a vehicle such as a truck. A load with an auxiliary member having a non-linear spring characteristic so that the acting force corresponding to the relative displacement occurring between the frame and the rear axle housing varies with a curved characteristic as smooth as possible. Since it is transmitted by a response transmission member, conventional hydraulic control devices could only properly determine hydraulic control points under load conditions at two points, but it is possible to determine hydraulic control points under many load conditions as much as possible under many load conditions. Since it is possible to set hydraulic control points suitable for This makes the operation of the hydraulic control valve even more effective especially in vehicles such as trucks where the load often changes.

Furthermore, the brake control device of the present invention can be particularly effectively applied to vehicles equipped with a fluid suspension in which the load-deflection relationship changes continuously in a curvilinear manner.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1A is a front view of the embodiment, the opening of the figure is a cross-sectional view taken along line X-X in FIG. 4 is an explanatory diagram showing the relationship between the front wheel braking force and the rear wheel braking force, and FIG. 4 is an explanatory diagram showing the relationship between the relative displacement of the rear axle housing with respect to the frame and the oil pressure at the hydraulic control point. 1... Frame, 2... Oil field control valve (
LSP') valve, 3...Rear axle housing, 6...Load response spring, 9...Auxiliary member.

Claims (1)

[Claims] 1. For a hydraulic control valve that is installed to control the control hydraulic pressure of the rear wheel cinder in a vehicle such as a truck in relation to the load that the rear wheel receives, one end is connected to a sprung member such as the frame of the vehicle as a load response transmission member. In a brake control device that is connected to a substantially straight rod-shaped spring member that is pivotally mounted and whose other end is connected to an unsprung member such as a rear axle (r') rank, the other end of the rod-shaped spring member is connected to the rear axle no. a curved auxiliary member articulated to the unsprung member, coaxially pivoted to the pivot portion at the one end of the rod-shaped spring member, and extending substantially along the surface of the rod-shaped spring member on the hydraulic control valve side; and the contact area between the auxiliary member and the rod-shaped spring member is configured to continuously change toward the free end of the auxiliary member in correlation with the deformation of the rod-shaped spring member as the load applied to the rear wheel increases. A vehicle brake control device characterized by comprising: