JPH0249947B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dual-system braking device used in large vehicles, etc., and is mainly concerned with a brake system that can be made smaller and lighter in weight, and that can detect failures before they occur and issue a warning. Regarding equipment.

In braking devices for large trucks and the like, the front wheel and rear wheel are separated into separate systems, and the braking force is boosted by separate boosters for each.

Incidentally, in recent years, brake devices have been pursued to be smaller and lighter, and as a booster for such dual-system brake devices, diaphragms commonly used in conventional air brake devices have not been used. If it were possible to use a booster that combines a power chamber (brake chamber) and a hydraulic cylinder,
Compared to the air-hydraulic servo-type booster commonly used in conventional hydraulic brake devices, the long air cylinder part unique to this device is not required, making the entire device smaller and lighter. It can be done.

However, in a normal dual-system brake system, the rear wheel cylinder diameter is different between the front wheel and the wheel, and the brake shoes have different shoe gaps, so the stroke amount of the pistons, etc. of both boosters is different. There was a significant difference.

On the other hand, in the power chamber using the above diaphragm, since the diaphragm is flexible, the effective pressure receiving area (effective diameter) changes depending on the stroke position, and due to the shape change, the diaphragm moves in conjunction with the diaphragm. The output from the piston plate and push rod changes as shown in FIG.

That is, Figure 1 shows the relationship between the output pressure (P) on the vertical axis and the stroke length (l) on the horizontal axis. In the diagram, the L curve is for a large power chamber, and the S curve is for a large power chamber. It represents the change in each output pressure (P) in the case of a small power chamber. However, in both cases, as the stroke length (l) of the diaphragm increases, the output pressure (P) decreases, but the smaller the diaphragm, the smaller the initial effective pressure receiving area, so the change in output pressure (P) becomes more rapid. .

When a power chamber with such characteristics is applied to the booster of the above-mentioned two-system brake system, since there is an inherent difference in the required stroke length between the two systems, the output of both boosters will be reduced as shown in Figure 1. A differential pressure (ΔP) occurs between the pressures.

Moreover, the smaller the power chamber is, the wider the stroke range used is, so the maximum differential pressure (ΔP ₂ max) becomes larger as shown in the figure.

However, in a two-system brake system, if there is a pressure difference between the output pressures of both systems, the system with higher pressure will be used more than the system with lower pressure, causing problems such as premature wear of the brake linings. There is.

Therefore, if it is applied to the above two systems of boosters, the range of stroke length (l) will be narrower by using a larger power chamber, and the differential pressure (ΔP ₁ , It was necessary to make ΔP ₂ ) as small as possible.

However, this would lead to an increase in the size of the device, which would go against the original intention.

In addition, when the wear of the brake linings in one system has reached a permissible level, a means is needed to notify the driver. A differential pressure detection device has been proposed that detects a brake pressure differential and issues an alarm when the differential pressure exceeds an allowable value.

However, such conventional differential pressure detection devices are intended to detect only a large differential pressure ΔP between systems, such as when one circuit is damaged.
It was not intended to detect wear of the lining or differential pressure (2 to 10 Kg/cm ² ) that would affect braking stability.

Furthermore, there is a considerable difference in the magnitude of the brake pressure, that is, the input pressure to the booster or the operating pressure of the power piston, between gentle braking and sudden braking, and this variation in brake pressure causes a significant difference in the allowable differential pressure. Although this is subject to change, there has not been a device that takes this point into consideration.

In other words, when the power chamber described above is applied, the original pressure difference (ΔPi) between both systems is
Therefore, it has been impossible for conventional detection devices to distinguish between the differential pressure (ΔPi) and the differential pressure (ΔPx) caused by the failure.

What should be detected is differential pressure and input pressure (Pa)
(ΔP/Pa). For example, if the brake lining of one system is worn out,
The differential pressure (ΔP) between both systems increases even if the input pressure (Pa) is the same, and the above-mentioned ΔP/Pa also changes. Therefore, alarm means should be activated only when this ratio exceeds an allowable set value, but conventional differential pressure detectors do not detect changes in this ratio (ΔP/Pa). Rather, the system was configured to operate uniformly, regardless of the brake operation conditions, if the differential pressure (ΔP) changes and exceeds a set value.

Therefore, when the input brake pressure is small, the above ΔP/Pa exceeds the allowable value, which means that an alarm should be issued, but the alarm system is not activated because the differential pressure itself between the two systems is small. On the other hand, when the brake pressure is high, the differential pressure also increases in proportion to this, so even though the above value of ΔP/Pa is within the allowable range, the alarm system will not activate. I had a problem with it.

Further, for the above reasons, the critical value of the differential pressure that activates the alarm device is set to a very high value, so that in many cases only the occurrence of a large differential pressure between systems, such as damage to a circuit, can be detected.

In view of such conventional problems, the present invention applies the above-mentioned diaphragm type power chamber to the booster of a dual-system brake system to achieve weight reduction and miniaturization, and uses the small-sized power chamber. The purpose is to provide a dual-system brake system equipped with a new differential pressure detection device that can eliminate the conventional drawbacks of conventional systems. A diaphragm type power chamber and a hydraulic The reason is that it is equipped with a booster made up of a combination of cylinders.

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

FIG. 2 is a circuit diagram showing an embodiment of a dual-system brake device equipped with a booster according to the present invention,
This embodiment shows a so-called air-over-hydraulic type brake device.

In the figure, 1 is a compressor, and compressed air generated by the compressor 1 is stored in an air reservoir 2. The air reservoir 2 is connected to a dual brake valve 4 through a pair of passages 3, 3, and the dual brake valve 4 is connected to the input of a pair of boosters 6 through a pair of passages 5, 5 corresponding to the passages 3, 3. The openings 61 are communicated with each other.

Further, the output ports 62 of the pair of boosters 6 are connected to the front wheel 8 and the rear wheel 9 through passages 7 and 7, respectively, and when the driver depresses the pedal 4a of the dual brake valve 4,
Compressed air in the air reservoir 2 is supplied to the booster 6 from the input port 61 via the passages 3 and 5 in accordance with the depression pressure.

The booster 6 converts the depression pressure of the pedal 4a into hydraulic pressure via compressed air pressure, boosts the pressure, and sends brake pressure to the front wheel 8 and rear wheel 9 through the output port 62 and passage 7. , predetermined braking is performed.

FIG. 3 is a longitudinal sectional side view showing details of the booster 6, which includes a diaphragm type power chamber 10 and a hydraulic cylinder 11.
It is composed of a combination of.

The power chamber 10 has an upper cover 12
and a lower cover 13, and is airtightly defined by a diaphragm 14 into a first chamber 15 and a second chamber 16. The first chamber 15 communicates with the input port 61, and the second chamber 16 communicates with the atmosphere through a port 161. Further, oil and the like are supplied into the hydraulic cylinder 11 from reservoirs 17 (see FIG. 1) and 18.

When compressed air at a predetermined pressure is introduced into the first chamber 15 from the input port 61, the diaphragm 14 moves to the right in FIG. , moves to the right against the urging force of the spring 21, and due to the propulsive force of the push rod 20, the tip of the rod 20 presses the piston 22 in the hydraulic cylinder 11, generating increased hydraulic pressure. let The hydraulic pressure is transmitted from the output port 62 to the front wheel 8 and the rear wheel 9 via the passage 7 to perform predetermined braking.

In addition, in the figure, 23 is a ring that covers the upper and lower covers 12, 13 and the periphery of the diaphragm 14, 24 is a seat ring, 25 is an O-ring, 2
6 is a connector hose, 27 is a connector, 28
29 is a metal gasket, 29 is a hydraulic pressure supply and return adjustable check valve, 30 is a compression spring, 31 is a retainer, 32 is a packing cup, 33 is a stopper for the piston 22, and 34 is a ring retaining.

The booster 6 is equipped with a differential pressure detection device 35 shown in FIGS. 2 and 4.

In this embodiment, the differential pressure detection device 35 is a cylinder 3 formed in a body 36 as shown in FIG.
A piston 38 is disposed at 7 so as to be slidable in the axial direction of the cylinder 37 (horizontal direction in FIG. 4).

A first chamber 39 and a second chamber 40 formed on both sides of the piston 38 are equipped with compression springs 41 and 42, respectively.
8 is biased from both sides with equal predetermined spring forces (f ₁ ) and (f ₂ ).

A guide groove 43 having a generally V-shaped cross section is formed in the approximate center of the piston 38, and an operating pin 44a of an alarm switch 44 comes into elastic contact with the guide groove 43 with a predetermined biasing force (fs). The engaged terminals 44b, 44b of the alarm switch 44 are connected to a power source 45 and an alarm lamp 46, and when the alarm switch 44 is closed by moving the operating pin 44a upward in FIG. A warning lamp 46 is turned on.

The differential pressure detection device 35 is also provided with a braking mechanism 47 that applies a predetermined load to the piston 38 from the side, and the mechanism 47 is configured as follows.

That is, a protrusion 48 is provided approximately at the center of the body 36.
is provided, and a sub-cylinder 49 formed within the protrusion 48 communicates with the cylinder 37.

A ball 50 as a braking member is engaged with the guide groove 43 of the piston 38, and the ball 50 is connected to a compression spring 52 via a retainer 51.
It is brought into elastic contact with the guide groove 43 with a predetermined biasing force (ft).

The other end of the spring 52 is attached to a sub-piston 53 that can freely slide in the vertical direction in FIG.
A third pressure introduction hole 54 is formed at the lower end of the cylinder 8 so as to communicate with the sub cylinder 49 .

The pressure introduction hole 54 of the braking mechanism 47 of the piston 38 is connected to the passage 5 near the input port 61 of the first booster 6a by a branch passage 55 as shown in FIG.
When the dual brake valve 4 is operated, a predetermined compressed air pressure from the air reservoir 2 acts on the sub-piston 53.

Also, pressure introduction holes 56 and 57 are formed at both ends of the body 36, as shown in FIG. 4, to communicate with the first chamber 39 and the second chamber 40, respectively, and as shown in FIG. The first pressure introduction hole 56 is connected to the passage 7 of the first booster 6a through a first branch passage 58, and the second pressure introduction hole 57 is connected to the passage 7 of the first booster 6a through a second branch passage 59. It is connected to the passage 7 of the
The output pressures of a and 6b are respectively introduced, and the piston 3
8 in the sliding direction.

In addition, in this example, as shown in FIG.
The pressure receiving areas at both ends of the piston 38 are equal to B, the pressure receiving area of the sub-piston 53 is A, the biasing force of the compression spring 52 is ft, the pressure introduction hole 54,
Assuming that the compressed air pressure and liquid pressure introduced from 56 and 57 are Pa, Pb, and Pc, respectively, and the angle of the V-shaped guide groove 43 is Θ, when a differential pressure occurs between the output pressures Pb and Pc, Differential pressure ΔP=|Pb−Pc|·B, and if Pb>Pc, the piston 38 tends to move rightward in FIG. 5 due to the differential pressure (ΔP). On the other hand, as a force for braking the movement of the piston 38, the sub-piston 53 presses the ball 50 by the urging force (fs) of the operating pin 44, the urging force (ft) of the spring 52, and the input pressure (Pa). Each of the above guide grooves 43 of pressure (PaA)
Total force T = (PaA) determined by the angle (Θ) of
+ft+fs)·α [α is a constant] acts in the left direction in FIG. Here, the above ft, fs are Pa, Pb,
Since it is sufficiently small compared to Pc, it is considered that the piston 38 starts to move when the differential pressure (ΔP) becomes larger than the braking force (T=PaA·α). In this embodiment, the limit value of the permissible amount of wear of the brake lining is determined based on the performance of the booster 6 and the correlation between the amount of wear of the brake lining and the magnitude of the differential pressure (ΔP) generated thereby. The critical value of the ratio (ΔP/Pa) between the differential pressure (ΔP) and the input pressure (Pa) corresponding to is set in advance, and the pressure receiving area (A ), the pressure receiving area (B) of the piston 38, and the angle (Θ) of the guide groove 43 are set.

In other words, the piston 38 is activated only when the ratio of the differential pressure (ΔP) to the input pressure (Pa) exceeds the critical value, regardless of variations in the differential pressure (ΔP) due to variations in the input pressure (Pa). It is configured to move in the left and right direction to activate the alarm switch 44, and when the critical value is exceeded, the braking force (T=PaA・α) is activated.
This is when the differential pressure (ΔP) becomes larger than .

Next, the operation of this embodiment will be explained.

In this example, since a diaphragm type booster is used, the output pressures (Pb) and (Pc) of both systems of the brake system are maintained even during normal operation.
A differential pressure (ΔPi) has been generated between the two from the beginning. The original differential pressure (ΔPi) is determined by the setting conditions of the brake device, and the ratio of both input pressures (Pa) and the differential pressure (ΔPi) is determined by the input pressure (Pa) and Regardless of the accompanying fluctuations in the differential pressure (ΔPi), it remains constant because both are approximately proportional.

However, if some kind of failure occurs in the output system of one of the two systems, for example, if only one system's brake lining wear has progressed, there will be problems other than the original pressure difference (ΔPi) caused by the failure. Differential pressure (ΔPx) occurs between both systems, and input pressure (Pa)
Even if is constant, the differential pressure (ΔP=ΔPi+ΔPx) fluctuates by a considerable amount, so the ratio (ΔP/Pa) between the differential pressure (ΔP) and the input pressure (Pa) fluctuates.

Even in this case, for example, if the amount of wear on the brake lining has not reached the allowable limit,
As mentioned above, the ratio between the differential pressure (ΔP) and the input pressure (Pa) does not exceed the preset critical value, so under this condition, the differential pressure when Pb>Pc in FIG. ΔP=(Pb-Pc)・B is the braking force due to the above input pressure (Pa); it is never larger than T=Pa・A・α, the piston 38 does not move to the right, and the alarm switch 44 doesn't work.

However, when the wear of the brake lining of the above system progresses and exceeds the permissible value, the relative magnitude of the differential pressure (∆P) to the input pressure (Pa) increases and exceeds the above critical value. Therefore, the fifth
In the figure, since the differential pressure (ΔP) becomes larger than the braking force (T), the piston 38 moves and the guide groove 4
3, the operating pin 44a of the alarm switch 44 moves upward to close the switch 44 and turn on the alarm lamp 46 to notify the driver that inspection or repair is required.

That is, in this embodiment, the means for activating the alarm switch 44 is not based only on the magnitude of the differential pressure (ΔP) between the output pressures of the booster 6, but also detects the differential pressure (ΔP). At the same time, a braking force is applied to the piston 38 by the input pressure (Pa) corresponding to the differential pressure, so for example, if only the lining of one brake system is worn and the amount of wear exceeds the allowable value. If the amount of wear is a certain value within the allowable value, the input pressure (Pa) will fluctuate due to slow and fast brake pedal operation under that condition, and the system will respond accordingly. Even if the differential pressure (ΔP) between the output pressures fluctuates, the above-mentioned alarm switch will not operate, and there is no risk of issuing a false alarm to the driver.

For this reason, the conventional diaphragm type power chamber 10 was not compatible with the two-system brake boosting mechanism, but by equipping it with the differential pressure detection device according to this embodiment, such a differential pressure can be naturally generated. In the case of brake equipment, if the differential pressure is incorporated into the differential pressure/input pressure critical value setting conditions in advance, the above-mentioned condition can be set only when a situation requiring inspection or repair occurs, regardless of the existence of the differential pressure. Alarm means can be activated.

However, the diaphragm type booster 6
Therefore, it can be made lighter and smaller than a commonly used air-over-hydraulic brake system that uses a power piston booster.

In this embodiment, the braking member 50 in the piston braking mechanism 47 is engaged with the guide groove 43 common to the drive pin 44a, but this engagement position is arbitrary, and the piston 38 can be It is sufficient if it can be braked from the side. Furthermore, the cross-sectional shape of the guide groove 43 is not limited to the above-mentioned V-shape, but may be any shape that generates a component force in the direction opposite to the direction of the differential pressure (ΔP) due to the braking force (T) from the side surface of the piston. .

As detailed above, in the dual-system brake system for vehicles according to the present invention, only when the ratio of the differential pressure between both output pressures of the booster and the input pressure exceeds an allowable critical value. Since it is equipped with a differential pressure detection device configured to activate an alarm means, a booster consisting of a diaphragm type power chamber and a hydraulic cylinder can be applied.
Moreover, even if the booster is miniaturized, it does not have the same disadvantages as in the conventional case.
If a repair or the like is required, a warning can be issued without any malfunction, and the driver can be informed of this.

Therefore, the dual-system brake device can be made smaller and lighter.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between output pressure and stroke length of a diaphragm type power chamber, Figs. 2 to 5 show an embodiment of the present invention;
The figure is a circuit diagram of a two-system brake system, Figure 3 is a vertical cross-sectional side view of a booster, Figure 4 is a conceptual diagram of a differential pressure detection device, and Figure 5 is an explanation showing the force relationship when differential pressure occurs. It is a diagram. 6...Boosting device, 10...Power chamber,
11... Hydraulic cylinder, 14... Diaphragm, 20... Push rod, 21...
Piston, 35... Differential pressure detection device, 38... Piston, 43... Guide groove, 44... Alarm switch,
47... Braking mechanism, 50... Braking member.

Claims (1)

[Claims] 1. Compressed air is introduced into each booster through the output port of the dual brake valve, and the front wheel cylinder and rear wheel cylinder are operated by the output hydraulic pressure from the hydraulic cylinder of the booster. In the two-system brake system for vehicles to be operated, (a) a power chamber having a diaphragm provided on the back of a piston plate, and a hydraulic chamber having a hydraulic piston slidably arranged in conjunction with a push rod connected to the piston plate; (b) a body in which first and second pressure introduction holes are formed at both ends and a third pressure introduction hole is formed in a side surface; a piston that is slidably disposed in the cylinder and has a guide groove that is inclined in the axial direction on the side surface facing the third pressure introduction hole; and a piston that is slidably disposed in the third pressure introduction hole. a braking member having a sub-piston whose one end is brought into elastic contact with the guide groove by air pressure; and an alarm means for detecting sliding of the piston and issuing an alarm, Hydraulic pressure is applied to both end surfaces of the piston through the introduction hole, and air pressure is applied to the other end surface of the sub-piston through the third pressure introduction hole, thereby applying a braking load to the piston based on the air pressure. and a differential pressure detection device that moves the piston and activates the alarm means when the ratio of the hydraulic pressure to the differential pressure acting on both end surfaces of the piston exceeds an allowable critical value, c) Introducing the respective output hydraulic pressures of the boosters into the first and second pressure introduction holes of the differential pressure detection device, and introducing either of the two boosters into the third pressure introduction hole. A two-system brake system for a vehicle, characterized in that one input pressure is introduced.