JP4609650B2 - Brake clearance detector - Google Patents

Description

  The present invention relates to a brake clearance detection device that detects a state of a brake clearance in a brake mechanism.

In the brake mechanism 20 used in a vehicle or the like, as shown in FIG. 6, the braking lining 23 and the brake drum are fixed by fixing the braking lining 23 to the outer peripheral surface of the brake shoe 22 disposed on the inner peripheral side of the brake drum 21. When the brake shoe 22 is moved to the brake drum 21 side and the braking lining 23 is pressed against the brake drum 21 when necessary, the braking force is obtained and the braking force is released. The brake shoe 22 is moved away from the brake drum side.
The separation and movement of the brake shoe 22 is performed by the movement of an operation piston 28 provided in the brake chamber 25. The movement of the operating piston 28 is performed by following a rod 27 connected to a piston 26 that moves pneumatically within the brake chamber 25.

The air pressure applied to the brake chamber 25 is supplied from the air tank 30. Air pressure is supplied from the air tank 30 by a control valve 31, and a command pressure for the control valve 31 is output by a brake valve 33 having an operation pedal 32.
That is, in the brake mechanism 20, when the brake valve 33 is operated via the operation pedal 32, an air pressure (command pressure) corresponding to the operation amount is output to the control valve 31, and the control valve 31 responds to the command pressure. The pressure outputs air pressure to the brake chamber 25 through the air pressure line 34.
In the brake chamber 25, the piston 26 is pushed by the operating air pressure, the brake shoe 22 moves through the rod 27 and the operation piston 28, and the braking lining 23 is pressed against the brake drum 21 to operate the brake.

By the way, when the brake is used, the brake lining gradually wears out and the lining clearance increases. Originally, the lining clearance should be checked and adjusted on a daily basis, but if this is neglected, the lining clearance will eventually become excessive, and the piston stroke in the brake chamber will become large in order to obtain the required braking force, Every time the brake is operated, a large amount of air is consumed from the air tank. As a result, there is a problem that the pressure in the air tank is lowered to the extent that a necessary braking force cannot be obtained even if the brake is operated several times, resulting in insufficient braking effectiveness. In addition, an increase in the piston stroke means that the time from the operation of the brake valve to the start of braking becomes longer, and there is a problem that braking is delayed. In an extreme case, the brake lining does not sufficiently hit the brake drum even if the piston makes a full stroke, and no braking force is generated even if the brake is operated.
In recent years, a pneumatic brake with an auto adjuster that automatically adjusts the lining clearance has been used to prevent the trouble.

In addition, as shown in FIG. 7, a stroke switch 25a is attached to the bottom surface of the brake chamber 25 on the rod 27 side, and when the piston stroke becomes excessive, the piston 26 operates the stroke switch 25a to give an alarm. Has been proposed (see Patent Document 1).
Japanese Patent No. 2737579

  However, the above-described apparatus with an auto adjuster tends to neglect daily checking of the lining clearance. It is only necessary that all brake devices used are updated with auto adjusters, but there are still many pneumatic brakes without auto adjusters. In addition, it is not rare to use an old device and a new device together, and there is a problem that inspection is not performed.

Further, in the method of providing the stroke switch as described above, since the stroke switch is pushed with a strong force by the piston, it is not possible to attach only the stroke switch to the existing brake chamber, and the entire brake chamber assembly can be replaced. Necessary. For example, when a device using a pneumatic brake is a large truck, it is necessary to replace six brake chambers, resulting in a high cost burden. Therefore, in many cases, no measures are taken.
In the case of the heavy trucks mentioned as examples, such a situation is not desirable because of the equipment life of more than 10 years. Particularly in developing countries, it is serious because the replacement of the equipment for a longer period is not performed and the cost of replacing the brake chamber is small.

  The present invention has been made against the background of the above circumstances, and provides a brake clearance detection device that can accurately detect the state of brake clearance with a simple device configuration and can therefore be provided at low cost. With the goal.

That is, among the brake clearance detection devices of the present invention, the invention according to claim 1 is a device that detects the brake clearance of a brake system in which a fluid pressure source and a brake mechanism are connected by a fluid pressure line via a control valve. And a first pressure detecting means provided in the fluid pressure line for detecting a first pressure value which is not more than a jumping pressure value in the control valve, and a second pressure value which is not more than the jumping pressure value is detected. Second pressure detecting means for determining the state of the brake clearance based on the time difference at which the respective pressure values are detected.

  According to a second aspect of the present invention, in the first aspect of the present invention, the first pressure detecting means comprises a first pressure switch that uses the first pressure value as an operating pressure, and the second pressure detecting means comprises the first pressure switch. The pressure detecting means includes a second pressure switch having a second pressure value as an operating pressure, and a brake clearance state is determined based on a time difference in which each pressure switch is operated.

According to a third aspect of the present invention, there is provided a brake clearance detecting device according to the first or second aspect of the present invention, further comprising a NO-type terminal that is closed when the first pressure detecting means detects the first pressure value. 1 switch means and turn-on time adjusting means are interposed between the power supply and the control line of the switching element, and capacitor means is connected between the control line and the ground side, and in parallel with the capacitor means, NO type which becomes closed with the detection of the second pressure value by the second switching means and said second pressure detecting means having a by NC-type terminal is opened in accordance with the detection of the first pressure value the first pressure detecting means The third switch means having these terminals are connected to each other, and the brake clearance notifying means is connected to the output line of the switching element.

That is, according to the brake clearance detection device of the present invention, the first pressure value of the fluid pressure line that changes with the operation of the brake is detected by the first pressure detection means, and the second pressure value is detected by the second pressure detection means. The difference in time at which each value is detected is embodied. With respect to the time difference, by predetermining the value that the brake clearance is normal and the value that is abnormal, by comparing these and the above-mentioned difference in time, It is possible to determine whether the brake clearance at that time is normal or abnormal. The determination result is desirably notified so that a driver, a maintenance inspector, an administrator, and the like can recognize it, and may be notified only in the case of an abnormality determination.

The first pressure value and the second pressure value are equal to or less than the jumping pressure value of the control valve, and values suitable for determining the clearance state are determined in advance .
In general, a valve for operating a brake has a predetermined command pressure (or operation stroke, operation force, etc., hereinafter simply referred to as command pressure) as shown in FIG. 8A in order to prevent malfunction due to vibration or the like. Does not generate an output pressure, but outputs a pressure corresponding to the indicated pressure at a predetermined indicated pressure or higher. The predetermined output pressure at the predetermined indicated pressure is a jumping pressure (hereinafter referred to as Pj).

  When the command pressure exceeds a predetermined pressure corresponding to Pj, the load side pressure (brake chamber rod side) between the output pressure 0 and Pj is not dependent on the rate of change of the command pressure, and the load side volume and piping It is uniquely determined by the resistance. In other words, a constant rate of pressure change is shown as shown in FIG. On the other hand, the rate of change of output exceeding Pj differs depending on the rate of change of the operation pedal or the like, that is, the rate of change of the command pressure. That is, a rapid braking force is generated with a large output change rate during sudden braking, and a braking force is generated with a small output variation rate and small impact during slow braking.

Therefore, when two pressure values are detected and the time difference is obtained, the pressure difference below the jumping pressure value is obtained and the time difference is obtained. The piston stroke of the chamber can be accurately identified. On the other hand, when the time difference is obtained using a pressure value exceeding the jumping pressure, the moving position of the piston differs at the same time depending on the rate of change of the indicated pressure, so that the measurement accuracy is lowered. From the above points, the first and second pressure values are set to be not more than the jumping pressure value . The first, second pressure value except at most jumping pressure value, can each define an arbitrary value. However, if the values are too close to each other, it is difficult to clarify the difference in time, so it is desirable that both values be separated to some extent.

Further, as the pressure detection means for detecting the fluid pressure, for example, a pressure switch using the first pressure value as the operating pressure is used as the first pressure detecting means, and a pressure switch using the second pressure value as the operating pressure is used as the second pressure detecting means. Can be used as Moreover, it is good also as what detects both a 1st pressure value and a 2nd pressure value with one pressure sensor. However, if the pressure switch is used, the detection of the pressure appears as a switch operation, which can be used for realizing a time difference or determining the state of the brake clearance, thereby simplifying the apparatus.
The time difference between detection of the first and second pressure values may be embodied as the operation interval of the pressure switch, may be measured by a timer, or measured by a control unit having a CPU. You can also.
The determination of the brake clearance state based on the time difference is performed by, for example, storing the time difference data during normality and abnormality in a memory in advance in a control unit having a CPU and comparing it with the measurement data. Also good. Further, as described in claim 3 of the present application, the clearance state may be determined by an analog circuit.

In the analog circuit, the first switch means by the detection of the first pressure value by the first pressure detecting means becomes closed, FET, the power supply voltage to the control line, such as a thyristor is applied. Further, since the second switch means and the third switch means are opened at that time, the capacitor means constituted by a capacitor or the like is charged. The turn-on time of the switching element is adjusted by a turn-on time adjusting means composed of a variable resistor, etc., and the switching element is turned on when the turn-on time after voltage application is reached based on the adjusted value. do. If the detection of the second pressure value is earlier than the turn-on time, the third switch means is closed before the charging of the capacitor means is completed, and the capacitor means is discharged through the third switch means. Thereafter, even if the switching element tries to turn on, the current from the power source flows out of the switching element through the switching means 3, and the driving current in the switching element is insufficient, so that the switching element cannot be turned on. Therefore, the brake clearance notifying means is not energized. This state is a state in which the clearance is normal.

On the other hand, when the detection of the second pressure value by the second pressure detecting means is later than the turn-on time, the charging of the capacitor means is completed, so that the driving current from the power source is given to the switching element, and the switching element is turned on. To do. As a result, the brake clearance notifying means is energized to perform a desired notification operation. The notification operation can be performed by sound, light, vibration, display on a display, or the like. This state is a state in which the clearance is determined to be abnormal.
Therefore, the time when the fluid pressure becomes the second pressure value at the boundary where the clearance shifts from the normal region to the abnormal region is obtained in advance, and the turn-on time is adjusted so that the switching element is turned on at or immediately before this time. By setting, clearance abnormality can be accurately detected.
A simpler configuration is possible by providing the first pressure switch with the first and second switch means and the second pressure switch with the third switch means.

As described above, according to the brake clearance detection device of the present invention, the fluid pressure source, the brake mechanism connected to the fluid pressure source via the control valve, and the control valve and the brake mechanism are connected. A first pressure detecting means for detecting a first pressure value which is not more than a jumping pressure value in the control valve, and a second pressure value which is not more than the jumping pressure value. And a second pressure detecting means for detecting the brake clearance, and the state of the brake clearance is determined based on the time difference at which each pressure value is detected. Therefore, the abnormality of the clearance can be detected with a simple configuration for measuring the pressure. In addition, it can be installed in an existing apparatus at low cost.

Below, one Embodiment of this invention is described based on FIGS.
In addition, the same code | symbol is attached | subjected about the structure similar to a conventional structure, and the description is abbreviate | omitted or simplified.
The brake mechanism 20 of this embodiment has the same structure as that of the conventional device, and the brake shoe 22 with the braking lining 23 attached to the brake drum 21 is moved toward and away by the movement of the operation piston 28. By doing so, the braking force is generated and released.
The operation piston 28 is moved by the operation of the brake chamber 25, and the configuration of the brake chamber 25 is the same as that of the conventional structure.

An air tank 30 that applies air pressure to the brake chamber 25 is connected to a control valve 31 and a brake valve 33, and an operation pedal 32 is coupled to the brake valve 33.
The air pressure output through the control valve 31 is output to the brake chamber 25 through the pneumatic line 34.
The pneumatic line 34 is provided with a first pressure switch 1 having a first pressure value as an operating pressure as first pressure detecting means, and a second pressure switch 2 having a second pressure value as an operating pressure as second pressure detecting means. It is provided as. The first pressure value and the second pressure value thereof is set to Jean ping pressure values following values defined in the control valve 31, and a relationship between the first pressure value <second pressure value . For example, the first pressure value can be set to about 30 kPa, and the second pressure value can be set to about 50 kPa.

The first pressure switch 1, and a N C-type terminals SW1 N O type terminal SW1 as a first switch means and (NO) as a second switch means (NC). The second pressure switch 2 has a NO-type terminal SW2.
The SW1 and SW2 are connected to the circuit shown in FIG.

That is, the terminal SW1 (NO) has one terminal connected to the ignition power supply and the other terminal connected to one end of the resistors R1 and R2 and the source of the FET serving as a switching element. The resistor R1 is provided for current adjustment, and the other side is grounded. Therefore, the resistor R1 has a low resistance value, for example, several kΩ.
The other side of the resistor R2 is connected to one end of a variable resistor VR corresponding to the turn-on time adjusting means. The variable resistor VR can adjust the turn-on time of the switching element by changing the resistance value. For example, a variable resistor VR having a maximum resistance of 1 MΩ can be used. The adjustment of the turn-on time is suitable for reducing the measurement error.

In addition, since the determination time difference (time difference between the first pressure value detection and the second pressure value detection) differs depending on the target device, the brake is adjusted to the amount of clearance to be detected when the detection device is mounted, and the variable resistor VR The time difference to be detected can be determined by operating the brake while changing the value.
Further, when applied to a plurality of brake devices, the detection time difference between the first pressure value and the second pressure value differs depending on the load-side capacity, so that it is also necessary to adjust this. That is, it can be applied to a plurality of types of brake devices by adjusting the turn-on time, and is excellent in versatility. For example, in the case of a large truck, the time difference to be detected varies depending on the number of axles and the wheelbase, but any variation can be accommodated by providing a turn-on time adjusting means.

The other end of the variable resistor VR is connected to one end of a capacitor C, which is capacitor means, one end of a resistor R3, and the input side of the amplifier AP. The other end of the capacitor C is grounded, and the other end of the resistor R3 is connected in parallel with one end of the terminal SW1 (NC) and one end of the SW2, and the other end of the terminal SW1 (NC) and the other end of the SW2 are Grounded. As the capacitor C, a capacitor having a storage capacity for supplying a driving current to the switching element is used. For example, about 10 μF is used. The resistor R2 determines the resistance value in consideration of the adjustment range of the variable resistor VR. For example, about 100 kΩ can be used. For R3, for example, about 1 kΩ can be used.
The FET gate is connected to the output side of the amplifier AP. That is, the control line extends from the ignition power source to the resistor R2, the variable resistor VR, the amplifier AP, and the gate. Also, an alarm device 40 is connected to the drain of the FET as a notification means, and the other end of the alarm device is grounded. A line including the source and drain of the FET and the alarm device 40 constitutes an output line.

Hereinafter, the operation of the above apparatus will be described with reference to FIGS.
When the operation pedal 32 is operated by a driver or the like, the command pressure is applied to the control valve 31 by the brake valve 33 according to the operation amount of the operation pedal 32. In the control valve 31, when the command pressure does not reach a predetermined pressure (pressure corresponding to the jumping pressure), it is determined as an error and air pressure output control is not performed . On the other hand, when the command pressure exceeds a predetermined pressure, up to Jean ping pressure increases the output pressure by a predetermined rate of change, then the change rate according to the rate of change of finger pressure To increase fluid pressure. By the way, in the initial state where there is no lining wear, as shown in FIG. 3, the load-side pressure also increases early in a short time. Therefore, the change line L0 having the largest inclination is shown in the graph shown in FIG. On the other hand, as the lining wears out, the increase in load pressure gradually delays, and the above change line also becomes a change line L having a small inclination. Further, when the lining wears up and reaches an abnormal state, the change line L1 has a smaller inclination. In these change lines, the difference in time for detecting the first and second pressures determined in advance also becomes longer as the piston stroke increases as the lining is consumed. Here, the time difference when shifting to the abnormal state is set to N in advance, and the following brake lining state determination procedure will be described. This time difference N corresponds to the turn-on time in the switching element, and the turn-on time in the circuit is adjusted by a variable resistor as necessary.

Along with the operation of the brake, the pressure of the pneumatic line 34 is measured by the first pressure switch 1 and the second pressure switch 2. The first pressure switch has terminals SW1 (NO) and SW1 (NC). The terminal SW1 (NO) is normally open, and SW1 (NC) is normally open. Closed.
In the above brake operation, when the first pressure value is detected by the first pressure switch 1, the first pressure switch 1 is operated, SW1 (NO) is closed, and SW1 (NC) is opened. Thereby, in the circuit shown in FIG. 2, the voltage of the ignition power supply is applied to the gate of the FET and the capacitor C, and the capacitor C is charged. Further, in the FET, the drive current through the gate does not flow due to the action of the current adjustment resistor R1.

Thereafter, when the air pressure is continuously measured by the second pressure switch 2 and the second pressure value is detected, the second pressure switch 2 is activated.
When the lining clearance is less than the abnormal value, the piston stroke of the brake chamber is small, and the difference between the second pressure value detection time n2 and the first pressure detection time n1 is smaller than the set time difference N. That is, the second pressure value is detected by the second pressure switch 1 before the FET is turned on. Then, the second pressure switch 1 operates, and SW2 is closed as shown in FIG. As a result, the capacitor C is discharged through the resistor R3 and the terminal SW2. Thereafter, the drive current necessary for turning on the FET cannot be obtained, and the FET does not turn on. For this reason, no warning signal is output from the alarm device 40.

  On the other hand, if the lining wears out and the clearance is larger than the abnormal value, the piston stroke of the brake chamber increases, and the difference between the second pressure value detection time n2 and the first pressure detection time n1. Becomes larger than the set time difference N. That is, the second pressure value is detected by the second pressure switch 1 before the FET is turned on. Then, as shown in FIG. 5B, since the capacitor C ends charging, current does not flow into the capacitor C, but current flows between the gate and drain of the FET. The FET is turned on using this as a drive current, the output line is energized, and the alarm device 40 operates. The alarm device generates a warning signal and notifies the driver or the like of abnormality by turning on / off sound or light. Thereby, it can be known at an early stage that an abnormality has occurred in the clearance of the brake mechanism. In addition, if the set time is set early and a margin is provided, it is possible to warn and perform maintenance before an abnormality occurs.

As described above, in the present invention, the state of the brake clearance is detected by the pressure switch and the analog circuit, but the method is not limited to the above, and the time difference between the pressure values is actually measured, It is also possible to make a determination by performing calculations, comparisons, etc. with a control unit including a CPU. However, the above configuration makes it possible to detect excessive lining gaps in the pneumatic brake by using two inexpensive pressure switches and a detection circuit without replacing expensive brake chambers for each brake, thereby preventing insufficient braking effectiveness. Can do.
As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to the said content, In the range which does not deviate from this invention, a change is possible.

It is a figure showing a brake system in one embodiment of the present invention. It is a figure which similarly shows the circuit for determining the state of clearance. Similarly, it is a figure which shows the relationship between the change of the pressure in a brake, and time passage. It is a flowchart which similarly shows the procedure which determines the state of clearance. It is a figure which similarly shows the energization state of the circuit at the time of the state determination of clearance. It is a figure which shows the conventional brake system. It is a figure which similarly shows the brake chamber which enabled abnormality detection. It is a figure which similarly shows the change of the air pressure output with respect to the operation amount at the time of brake operation, and operation speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st pressure switch 2 2nd pressure switch 20 Brake mechanism 21 Brake drum 22 Brake shoe 23 Brake lining 25 Brake chamber 26 Piston 27 Rod 28 Operation piston 30 Air tank 31 Control valve 32 Operation pedal 33 Brake valve

Claims (3)

A device for detecting a brake clearance of a brake system in which a fluid pressure source and a brake mechanism are connected by a fluid pressure line via a control valve, the device being provided in the fluid pressure line and having a jumping pressure value or less at the control valve. A first pressure detecting means for detecting a certain first pressure value; and a second pressure detecting means for detecting a second pressure value that is equal to or less than the jumping pressure value. A brake clearance detecting device, wherein a state of a brake clearance is determined based on the determination.   The first pressure detecting means comprises a first pressure switch that uses the first pressure value as an operating pressure, and the second pressure detecting means comprises a second pressure switch that uses the second pressure value as an operating pressure. 2. The brake clearance detecting device according to claim 1, wherein a state of the brake clearance is determined based on a time difference in which each pressure switch is operated. The first switch means having a NO-type terminal that is closed when the first pressure value is detected by the first pressure detecting means, and the turn-on time adjusting means are interposed between the power source and the control line of the switching element. Capacitor means is connected between the control line and the ground side, and in parallel with the capacitor means, there is an NC type terminal that opens when the first pressure detection means detects the first pressure value. Third switch means having NO-type terminals that are closed in accordance with detection of the second pressure value by the second switch means and the second pressure detection means are respectively connected, and brake clearance notification means is connected to the output line of the switching element. The brake clearance detection device according to claim 1, wherein the brake clearance detection device is connected.

Images