JPS5849415B2 - The basics of the construction of the building - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for detecting the rate of increase of vehicle wheels in an anti-skid brake system.

Many anti-skid brake systems have a first circuit that causes a reduction in braking in response to a value for the wheel's angular acceleration that indicates a tendency to skid, and a second circuit that causes a reduction in braking when the wheel has regained attachment to the ground. The circuit has a control device that causes brake reuse.

The most advantageous moment for reusing the brakes occurs shortly after the moment when the wheel acceleration passes through its maximum value during a period of speed increase followed by a period of speed decrease.

The known device has a peak detection device that generates a signal to start reusing the brakes when the maximum acceleration is reached.

However, this circuit requires a circuit that generates an acceleration signal from a speed signal constantly provided by the wheel speed sensing device.

Other known circuits use similar devices to probe portions of acceleration curves.

Although these circuits ensure that the brakes are reused at advantageous times, these circuits are difficult to adjust and require an acceleration signal.

The use of acceleration signals is inconsistent with the current trend toward anti-skid braking systems that rely on speed signals directly.

The object of the invention is to provide a circuit that uses the speed signal directly to detect the rate of increase in wheel speed at particularly advantageous moments.

According to the invention, a circuit has a device for detecting the rate of increase in speed of a wheeled vehicle in an anti-skid braking system, said circuit having a differential amplifier, said circuit having a first input of said amplifier. is connected to a voltage source that provides a signal representative of the peripheral speed of the wheel, and a second input is connected to a voltage source that provides a signal that tends to increase in direct proportion to time; The circuit has a unidirectional conducting device with a limit connected between a first input end and a second input end, the unidirectional conducting device being connected from the second input end to the first input end. The output terminal of the differential amplifier is the first
is connected to the second input of the amplifier when the signal at the input of the amplifier tends to be larger than the signal at the second input.

At the output of the circuit according to the invention, a signal with straight edges appears when the voltages at the two inputs of the amplifier become equal with an increase in rate greater than the rate of increase of the voltage source of the speed signal. , and ends when the rate of increase of the speed signal becomes lower than the rate of increase of the voltage source.

The end of this signal corresponds to a distinct point on the velocity curve.

In this way, the green after the signal is used to limit the recovery of brake pressure.

Since the beginning of the signal corresponds to a relatively distinct point on the speed curve, the leading edge of the signal can be used to interrupt the cycle of gradual relief of brake pressure.

One of the advantages of this circuit is that it is very simple and easily adjusted.

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

The circuit shown in FIG. 1 has a differential amplifier 28 whose first input 1 receives the speed signal and whose output is connected by a resistor 30 and the base/emick junction of an NPN transistor 32. It is connected to the input terminal 2 of 2.

The collector of transistor 32 is connected to a PNP transistor 34, the emitter of which is connected to a voltage source, but whose collector is grounded by a resistor 36 and connected to conductor A.

The second input terminal of the differential amplifier 28 is also connected to a capacitor 38.
and a diode 40.

A diode 40 is connected between the two inputs of the amplifier 28 and conducts towards the first input 1 .

The capacitor 38 is a voltage source and a transistor/! 44, is coupled to a conventional constant current charging circuit 42 formed by resistors 46.4B, 50 and a diode 52.

Resistor 46 may be adjusted to allow adjustment of the current provided by circuit 42.

The constant current charging circuit 42 tends to supply a voltage to the capacitor 38 that increases linearly as a function of time, but unless the speed signal has a rate of increase higher than this voltage, the voltage is It stabilizes at a value U equal to the level plus the direct threshold U of the diode 40 that starts conducting.

The amplifier 28 is preferably configured such that the level of the speed signal applied to the first input 1 occurs at the second input 2 U=v+
Preferably, it is a unity gain difference amplifier that delivers a zero signal when the level of u is below.

Transistors 32,34 are then not conducting and no signal is transmitted to conductor A.

The charging voltage across the capacitor 38 is such that the voltage V corresponding to the wheel speed increases rapidly enough to cause the potential at the first input 1 to reach the potential at the second input 2; continues to increase at a rate greater than the rate of increase of V, the amplifier provides an output signal with a level equal to the level of the velocity signal V.

Transistors 32, 34 then begin conducting and conductor A carries a straight edge signal.

The output signal from the amplifier 28 is applied by means of the base/emitter connection of the transistor 32 and by means of the resistor 30 to the second input 2 at the potential of the first input 1, ultimately fixing the capacitor charging voltage equal to this potential. .

Next, the curves for the speed signal {circle around (2)} distributed over time and supplied to the first input of the amplifier 28, the curve for the potential U at the two previous inputs 2, and the control transmitted by the conductor A. The operation will be described in more detail with reference to FIG. 2 which shows a diagram of the signal T.

Time t.

corresponds to the start of brake operation. This time t.

From then on, the speed signal V begins to decrease, and when the decrease becomes so rapid that it shows a tendency to skid, the anti-skid device operates to reduce the brake pressure.

The speed signal then decreases less rapidly, then stops decreasing and starts increasing.

Time t.

, the signal U received at the second input 2 of the amplifier 28 is equal to the level of the speed signal received at the first input of the amplifier plus the threshold voltage U of the diode 40.

From this potential value, the current from constant current source 42 actually passes through diode 40 .

The difference between the level of the signal U and the level of the speed signal ■ remains equal to the conduction threshold U of the diode 40 as long as the speed signal decreases, and when the speed signal begins to increase, the constant current source 4
2 increases until time t1 when the rate becomes greater than the rate at which the capacitor 38 can be charged.

From time t1, the signal U increases linearly with a slope equal to the increase in voltage transmitted to the capacitor 38 by the constant current source 42, but the speed signal ■ increases even faster, and the level between the signals U and ■ increases. The difference will disappear.

When the level of signal U is between times t1 and 12, the level of signal V is
No current flows through diode 40 even though the level of .

This is because the level difference between the signals U and ■ is lower than the conduction threshold of the diode.

Time t. and t2, differential amplifier 28 does not provide a signal.

This is because the signal (2) supplied to the first input terminal is weaker than the signal U supplied to the second input terminal.

At time t2, signal U becomes equal to signal ■, and amplifier 28 provides an output signal at the same level as signal ■.

This output signal causes transistor 32 to conduct.

The signal at the collector of transistor 32 is then amplified to produce signal T, which is carried by conductor A.

The output from amplifier 28 is connected to the second output of this amplifier, so that signal U is practically equal to signal V as long as the output signal lasts.

The output signal from amplifier 28 is canceled at time t3 when constant current source 42 no longer increases at a rate greater than the rate at which capacitor 38 can be charged.

From time t3, signal U can again increase with the same slope as before, leading to time t4, when it stabilizes at a level equal to the speed signal V plus the threshold voltage of diode 40.

FIG. 3 shows that a circuit embodying the invention responds to the leading edge of signal T to terminate a period of brake pressure relief and
2 shows a control system for an anti-skid brake system used to terminate a brake pressure cut-off period in response to a trailing edge of a brake;

In the control system shown in FIG. 3, conductor A of the circuit for detecting the speed increase rate is connected to a solenoid shutoff valve 10 by a diode D1.

A logic control element 12 responsive to a particular value of speed reduction is connected to the solenoid shutoff valve 10 by a diode D2;
It is also connected to the solenoid relief valve 14 through a diode D3.

The logic control element 12 is also a monostable multi-bibreak 16
connected to the input end of the

The output terminal of the monostable multi-bi break 16 is a diode D.
4 is connected to the shutoff valve 10, and is also connected to the diode D5.
It is connected to the relief valve 14 by.

The monostable multi-bibreak 16 primarily consists of an NPN transistor 18, whose emitter is grounded and whose base and collector are connected by respective resistors 20, 22 to the positive pole of the voltage source.

Logic control element 12 is connected to the base of transistor 18 by a capacitor 24.

Transistor 18 is always conductive and stops conducting for the charging time of capacitor 24 at the moment the output signal from control element 12 ends.

Transistor 18 conducts again at the end of the charging time of capacitor 24, or in response to a signal related to the rate of increase in speed carried by conductor A, which is connected to the base of transistor 18 by diode D6 and resistor 26. It becomes conductive again.

The arrangement of diodes D1 to D5 is such that the solenoid shutoff valve 10 continuously receives the output signal from the logic control element 12;
The solenoid relief valve 14 continuously receives the output signal from the control element 12 while being able to receive the output signal from the monostable multi-bi break 16 and the signal T for the rate of speed increase transmitted by the diversion A. and the output signal from the monostable multi-pie break 16.

This manner of operation is illustrated in FIG. 4, which shows how the output signal C from the control element 12 occurs between times ta and tb in the monostable multi-by-break 16.
The output signals from are at times tb and t.

How can the signal T for the speed increase occur at time t?

and td.

Under these conditions, the cut-off period ■ occurs between times ta and td and thus ends in response to the trailing edge of signal T for the rate of speed increase.

The relief period D is at times ta and t.

and therefore ends in response to the leading edge of signal T.

The distribution of the cut-off and relief periods makes it possible to control very long anti-skid periods in which the wheel speed rapidly increases to the arrest point, where it lasts for a certain amount of time.

However, no short period of time will be used against you.

This only shortens the operating period of the monostable multi-bibreak.

As shown by the broken line, the signal M from the monostable vibration brake 16 would be as follows if no acceleration of the wheels occurred.
The cut-off period ■ could be extended until the time te, which is the end of the relaxation period of the monostable multibibreak.

The above description indicates that a circuit embodying the present invention can be incorporated into an anti-skid brake control circuit to detect a predetermined rate of increase in wheel speed.

Any value can be chosen for this percentage.

This is because this value is determined to be the rate at which the constant current source 42 transmits to the voltage increasing capacitor 38.

In the parts of the graph where U=V 10, the curve U follows the curve ■ very closely.

This is because the conduction threshold is between 0.22 and 1 volt, depending on the nature of the diode 40 used.

These conditions apply to the curve U at time t.

It intersects the curve ■ at the time td and leaves the curve ■ at the time td, and these times t.

and td are in the acceleration part of the curve ■, which are on both sides of the curve corresponding to the maximum wheel acceleration, but within the minimum acceleration part, and are within the range of the curve ■ which is very convenient for adhesion of the wheel to the taiji. As a result, the braking distance is considerably shortened.

Also, the time t in the rising portion of the speed curve ■.

The point defined as is satisfactorily defined such that this time can determine the end of the 1,1 J-f period during which the brake pressure is gradually reduced.

Time t in velocity curve V.

If the point corresponding to is well defined, the conduction threshold U of the diode 40 will be lowered accordingly.

[Brief explanation of drawings]

Figure 1 is a wiring diagram showing an embodiment of the present invention, Figure 2 is an explanatory diagram of the operation of the circuit shown in Figure 1, and Figure 3 is for a skid prevention device using the circuit shown in Figure 1. A wiring diagram of the control device and FIG. 4 are explanatory diagrams of the operation of the device shown in FIG. 3. 10... Solenoid shutoff valve, 12...
・Logic control element, 14... Solenoid relief valve, 16... Monostable multi-bi break, 28
... Differential amplifier, 42 ... Constant current charging circuit, ■ ... Speed signal.

Claims (1)

[Claims] 1. In a vehicle speed increase detection circuit in a skid prevention device, the detection circuit has a differential amplifier 28, the first input 1 of which is connected to a voltage source conveying a signal representative of the peripheral speed of the wheels. the second input 2 of said amplifier is connected to a voltage source 42 conveying a signal that increases linearly with time; a unidirectional conducting device 40 having a limit connected between the terminal 2 and the unidirectional conducting device 40 conducting from the first input terminal to the second input terminal and the output terminal of the differential amplifier 28; is connected to the second input 2 of the amplifier when the signal at the first input tends to be higher than the signal at the second input. .