JPH0471911A - Tire pressure detecting device - Google Patents

Abstract

PURPOSE:To obtain a highly reliable tire pressure detecting device by contriving the device in such a way that when a tire pressure detecting means that have been once judged to have failed is again returned to the normal condition, artificial reset operation can be dispensed with, and also the memory of the failure condition cannot be reset by noise or the like. CONSTITUTION:Tire pressure detecting means A by which tire pressure detecting signals are output while synchronizing with the rotation of wheels are provided to respective wheels, and when the output of any of the tire pressure detecting means is stopped and the outputs of the remaining tire pressure detecting means are continued, the tire pressure detecting means whose output has been stopped is judged by a failure judging means B to have failed. And, the periods or wheel velocities are calculated by a calculating means C on the basis of the respective tire pressure detecting signals, and the respective calculated periods or wheel velocities are compared by means of a comparison means D, and when the between respective periods or wheel velocities becomes within a prescribed value, it is judged by a return judging means E that the tire pressure detecting means A that has been judged by the failure judging means B to have failed has been returned to the normal condition.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a tire air pressure detection device for detecting tire air pressure.

``Prior art'' A tire pressure detection device installed in a vehicle detects a decrease in air pressure in the tire and notifies the driver.
This is to avoid danger when driving at high speeds and to improve fuel efficiency by normalizing tire pressure.
Since the vehicle runs on wheels, it is equipped with at least four tire pressure detection means. Based on the premise that the four tire pressure detection means do not fail at the same time, if there is a tire pressure detection means that outputs a tire pressure detection signal, the remaining tire pressures that do not output a tire pressure detection signal are A tire low pressure warning device that determines that the detection means is malfunctioning is disclosed in Japanese Patent Application Laid-Open No. 72409/1983. In such a case, there is a need to store the failure determination result in a memory using a backup power source when the power is turned off, and to immediately report the failure state when the power is turned on next time for repair. If this need is met, it is necessary to reset the memory state normally after failure repair.

[ff that the invention tries to solve! fiJHowever,
When resetting manually, it is necessary to add a reset switch, new parts, etc. For this reason, when the failed tire pressure detection means starts outputting a tire pressure detection signal again, it may be possible to unconditionally determine that the detection means has returned to normal. There is a problem that the memory of a failure state may be reset inadvertently even though it is not normal, and safety is not completely ensured.

The present invention has been made in view of the above-mentioned problems, and has the following features: - When the tire pressure detection means that has been determined to be malfunctioning returns to normal again, a manual reset operation is not required, and the malfunction state is memorized by noise or the like. It is an object of the present invention to provide a tire pressure detection device that does not reset the tire pressure.

[Means for solving the problem] As a specific means for achieving the above object, as shown in Fig. 1, tire air pressure detection means for outputting a tire air pressure detection signal in synchronization with the rotation of the wheels is provided for each wheel. In preparation for this, if one of the tire pressure detection means stops outputting and the remaining tire pressure detection means continues outputting, the tire pressure detection means that has stopped outputting is determined to be malfunctioning. In the tire air pressure detection device, a calculation means calculates the period or wheel speed based on each tire air pressure detection signal, a comparison means that inputs and compares each calculated period or wheel speed, and the comparison means recovery determining means for determining that the tire pressure detecting means determined to be malfunctioning by the failure determining means has returned to normal when the difference between each cycle or each wheel speed becomes within a predetermined value as a result of the comparison; Provided is a tire air pressure detection device comprising:

"Made by MJ The operation of the tire air pressure detection device described above is as follows.

The calculation means calculates the signal period or the wheel speed based on the tire pressure detection signal including the output from the tire pressure detection means that is determined to be malfunctioning by the failure determination means. The calculated periods or wheel speeds are input to the comparing means and compared, and when the error between the periods or wheel speeds falls within a predetermined value, the return determining means determines whether the tire pressure detecting means determined to be malfunctioning is detected. It is determined that the system has returned to normal.

"Example" Embodiments of the present invention will be described based on the accompanying drawings.

FIG. 2 is a schematic block diagram of a tire empty voltage detection device to which the present invention is applied. The tire air pressure detection means 1-1d detect whether the air pressure of each tire is normal. 2
is a controller, and includes tire pressure detection means 1a to 1a.
Waveform shaping circuits 3-3d which input the tire pressure detection signal outputted by 1d and shape the waveform, RAM and R (not shown)
It is composed of a CPU 4 and a lamp drive circuit 5 including an OM, an input/output interface, etc. Waveform shaping circuit 38
The outputs of ~3d are connected to the interrupt request terminal of the CPU 4. The interrupt request terminal is, for example, a CPU manufactured by Motorola.
Like the ICI terminal of MC6801, it detects the rising or falling edge of the input signal and records the time of occurrence.
The CPU 4 has a function of making a catch using the 7 Lee running timer value inside the PU and generating an interrupt to the program at the same time.Furthermore, the CPU 4 has a function of determining tire pressures 6a to 6Gd and wheels, which are realized by processing a predetermined program. It has a speed calculating means 6a' - Gd', a determination means 7, a return H constant means 8, and a ramp control means 9. Wheel speed operator stage 6a
The outputs from ' to 6d' are input to the failure determination means 7 and the recovery determination means 8. The failure determination means 7 determines failure of the tire air pressure detection means 1a to 1d. The return determination means 8 is
It is determined that the functions of the tire pressure detection means 1a to 1d, which were determined to be malfunctioning, have returned to normal. Air pressure determination means 6
The lamp control circuit y, 9 which inputs the outputs of a to 6d and the output of the failure determination means 7 outputs 1 or O to each output port of the CPU 4 based on each output, and turns on or off the lamps 10a to 10d. The system is controlled to display a warning to the driver of a drop in tire air pressure, a failure of the tire air pressure detection means 1a to 1d, etc.

3 to 8 show the tire air pressure detection means 1a to 1.
d shows an example of the arrangement position and specific configuration. Since the tire pressure detection means 18 to 1d have the same configuration, the tire pressure detection means 1a will be explained below. In FIG. 3, 11 is a tire, and a rim 13 is fixed to a wheel shaft 17 with a hole nut 15. The brake drum 19 is welded to a plate 21, and the plate 21 is fixed to the wheel axle 17 with bolts (not shown).

The inner ring of the bearing 23 and the wheel shaft 17 are fixed by a nut 25. The bearing housing song 27 and the cover plate 29 are connected to the bearing 23 by bolts (not shown).
It is fixed to the hub 31 together with the outer ring. The lower end of the shock absorber 33 is fixed to the hub 31 with a bolt 35, and the upper end (not shown) of the shock absorber 33 is fixed to the vehicle body. One end of the suspension arm 37 is supported by the hub 31 by a bolt 38 so as to be rotatable about the bolt 38, and the suspension arm 37
The other end (not shown) is supported by the vehicle body.

The tire pressure detecting means 1a includes a pressure detecting section 39 fixed inside the tire by a fixing means 40 and the pressure detecting section 3.
9, and a tire air pressure detection sensor (hereinafter simply referred to as sensor) 41 disposed on the cover plate 29. Details of the pressure detection section 39 will be described later. The sensor 41 detects a change in the direction of the magnetic pole due to the reciprocating motion of the first and second magnets, which will be described later, and converts it into an electrical signal.
3 to the controller 2. This 1IS
In Figure 3, tire 11. Rim 13. Wheel nut 15. Wheel axle 17. Brake drum 19, plate 2
1. Natsu 25. The inner ring of the pressure sensing portion 39° bearing 23 rotates while the vehicle is running, but the other parts are supported by the vehicle body and do not rotate.

FIG. 4 is a detailed sectional view of the pressure sensing section 39.

101 is a cylindrical housing made of non-magnetic metal such as aluminum, and both ends 103 and 105 are formed at right angles. 107 and 109 are bases made of stainless steel or aluminum, and each housing 101
O-rings 111 are provided at both ends of the
113 and copper or aluminum gI. It is sealed in two stages by the sockets 115 and 117. base 107
An air pressure relief means 119 is provided at the end of the air pressure relief means 119 .

This air pressure relaxation means 119 is constituted by a filter made of sintered metal, and prevents the air pressure in the interior 121 of the base 107 from changing rapidly even if the air pressure of the tire changes suddenly. Reference numeral 123 denotes a check valve, one end of which discharges from inside the base, and the other end biased by a coil spring 127 via a circular tail 125. This coil spring 127 always urges the air pressure relief means 119 and the check valve 123 in a direction in which they are pressed together. 129 is a chamfered portion of the check valve 123, and this chamfered portion 129 forms a communication hole 131 of the base 107, through which air enters and exits the base. The distal end 124 of the check valve 123 is chamfered and is in contact with a displacement hand rri 135, which is, for example, a bellows.
23 in the right direction in FIG. 4 is the displacement means 135, and it is the fill spring 127 that urges the check valve 123 in the left direction in FIG.

A rubber grommet 133 is provided on the check valve 123, and when the tire air pressure increases abnormally and exceeds the reference value, the displacement means 135 moves to the left in FIG. Chie 7 Riben 1
23, the grommet 133 also moves to the left to close the communication hole 131 and prevent the air inside the tire from passing through the communication hole 131. This coil spring 127. Check valve 123. The grommet 7) 133 constitutes a blocking means. The displacement means 135 is a bellows made of metal such as nickel, and has a bag shape.
a is fixed to the base 107 with an airtight fixing means such as adhesive, and the communicating hole 13 is fixed by this displacement means 135.
This maintains airtightness between the air inside the tire that enters through the pressure chamber 163 and the gas inside the pressure chamber 163, which will be described later. Reference numeral 137 is a connecting member for interlocking the displacement means 135 and the shaft 7) 139, and its detailed shape is shown in FIGS. 5(a) and 5.
Shown in Figure (b). This connecting member 137 is made of a non-magnetic metal such as stainless steel, and has a shape like a cylinder covered with a lid, and has a notch 137a and a protrusion 13 inside the cylinder.
7b. Here, FIG. 5(,) is a perspective view of the connecting member 137 viewed from the notch 137a, and FIG. 5(b) is a perspective view viewed from the opposite direction.

As can be seen from Figure #S4, the displacement means 135 is fixed to the convex portion 137b of the connecting member 137 by means of fixing means such as adhesive.

The resin mold 151 is formed by molding Sha 7) 139 with 01 resin, and is made of stainless steel balls 1.
Grooves 151a and 151b for inserting 53 and 155
have. 157 is a first magnet, 159 is a second magnet, and the permanent magnet on the ring is molded with resin 151.
It is fixed to the shaft 139 by. Here, the directions of the magnetic poles of the first magnet 157 and the second magnet 159 are different from each other. For example, as shown in FIG.
is the north pole, and the second magnet 159 is the south pole. The magnetic amplification means 161 has the shape of two stacked cylinders of two sizes, and is made of iron.

The small diameter portion 161a is the first magnet 157 or the second magnet 1.
On the other hand, the large diameter portion 161b is provided so as to face the detection means 31.

Note that this magnetic amplification means 161 is not limited to this shape,
Any shape is sufficient as long as the area facing the first or second magnet 157, 159 is small and the area facing the sensor 41 is large, thereby making it possible to amplify the magnetism of the first or second magnet. .

The pressure chamber 163 is a sealed space formed by the housing 101, the base 109, and the displacement means 135, and has a pressure that determines a decrease in tire air pressure and a pressure that is the center value of the normal pressure (in this example, 1.7 kgr/ cv12G)
is filled with air or inert gas. Magnetic material 165
and 167 are the first magnet 157 and the second magnet 159
The stator is provided within the housing 101 at a predetermined distance from the end face of the stator, and may be made of any magnetic material, but iron is used in this embodiment.

FIG. 16 shows a perspective view of a plate spring 141 made of stainless steel. As can be seen from FIG. 6, a hole 143 is provided in the center of the plate spring 141, and the shaft 7)
The tip 139a of the leaf spring 139 is slidably inserted, and the leaf spring 141 is in a flexed state, as shown in FIG.

FIG. 7 shows a shaft 7) 139 and a first magnet 157 fixed to the shaft 139 by a resin mold 151.
and a perspective view showing a second magnet 1599. This seventh
In the figure, grooves 151a and 151b are provided at three to four locations each, and a stopper portion 151e is formed by resin molding near the tip 139a of the shutter 7) 139. When assembling, this stopper part 151C is inserted into the notch part 137a, and then the stopper part 151C is inserted into the notch part 137a.
By rotating the shaft 7), the shaft 7) 139 is prevented from coming off from the connecting member 137.

In FIG. 4, the cylinder 145 is made of aluminum;
The purpose of assembly is to improve performance. That is,
The assembly is sometimes carried out after the magnetic body 167 is assembled into the housing 101, and then the connecting member 1 is assembled into the cylinder 145.
37. Displacement means 135, check valve 123. base 10
7. Insert the O-ring 111 etc. together with the cylinder 145 into the housing 101 from the right side in FIG. 4, and then
The shaft shown in FIG. 7 is inserted from the left side in FIG. 4, and the connecting member 137 and the sleeve portion 151C are engaged.

Next, the detailed structure of the sensor 41 is shown in FIG. 8. In FIG. 8, 61 is a case made of a non-magnetic metal such as an aluminum alloy, and 63 is a magnetic material core, which is made of iron or excited metal as the magnetic material. Uses 7 elites that are not available. The coil 65゛ is
An insulated conductive wire is wound around a magnetic material 63 via a resin bobbin 67, and both ends of the conductive wire are multi-patterned with metal fittings 69 together with two wire harnesses 43. electrically connected to the harness. With the above configuration, the sensor 41 can detect external magnetic changes and convert them into electrical signals.

Further, both ends of the conductive wire may be electrically connected together with the two wire harnesses 43 by a connecting means such as soldering using metal terminals fixed to the resin bobbin.

Next, the operation of the tire air pressure detection means 1a having the above structure will be explained. If the tire pressure is normal (e.g. 1
, 8 kgf/cm2G), the shaft 7) 139 moves to the left in FIG. 4, and the first magnet 157 and the magnetic body 165 are attracted to each other, as shown in FIG. It has become. In this state, the magnetic amplifying means 16
Since magnet 1 faces the south pole of the second magnet 159, the magnetic pole detected by the sensor 41 is the south pole.

Next, when the tire air pressure decreases, the determination pressure for tire air pressure decrease (in the case of this example, 1, G kgf/e+
++2G) or less, the thrust of the displacement means 135 due to the differential pressure between the gas pressure in the pressure chamber 163 and the tire air pressure acting on the displacement means 135 through the communication hole 131 causes the first magnet 157 and the magnetic body 165 to The mutual attraction force is exceeded, and the first magnet 157 and the magnetic body 165 separate. first magnet 1
57 and the magnetic body 165 are separated, the displacement means 135 rapidly moves to the right in FIG. 4 due to the spring force of the displacement means 135 and the differential force between the pressure in the pressure chamber 163 and the tire air pressure. As the displacement means 135 rapidly moves to the right, the shaft 7) 139 also moves to the right, and the second magnet 159 attracts the magnetic body 167. In this state, the magnetic amplification means 161 is in a state facing the north pole of the first magnet, and the magnetic pole detected by the sensor 41 changes to the north pole. By detecting this change in magnetic pole, the air pressure determining means 5a determines whether the air pressure of the tire has decreased. That is, when the air pressure of the tire is normal, the sensor 41 operates as shown in FIG.
The tire pressure detection signal shown in , ) is output.

Figure (b) shows a waveform obtained by shaping the output with a waveform shaping circuit.
Since the magnetic pole detected by changes from S pole to N pole, Fig. 9 (
As shown in c) and (d), a waveform obtained by inverting the output waveform in the normal state is output as a tire pressure detection signal. In addition, ΔTs in the figure is the time required for one rotation of the wheel,
ΔT I+ is the time the output waveform was at high level,
ΔTL is the time during which the output waveform was at Low level.

The air pressure relaxation means 119 is a means for directly displacing the pulsation of tire air pressure that occurs when a vehicle runs on a bumpy road, that is, when the tire air pressure suddenly fluctuates. 135 so as not to be transmitted.

As a result, even when the vehicle runs on a bumpy road,
Misjudgment, that is, it is not determined that the tire air pressure is normal when the tire air pressure is normal, or it is not determined that the tire air pressure is normal when the tire air pressure is decreased.

Next, a check valve 123 serving as a shielding means. Coil spring 127. The function of the grommet 133 will be explained. Even if the tire pressure is normal or has fallen below the judgment pressure for low tire pressure,
The coil spring 127 pushes the air pressure relief means 119 and the check valve 123 together, and the tip 1 of the check valve 123
24 is pressed against the displacement means 135, the grommet 133 is separated from the communication hole 131, so the air pressure inside the tire is J! ! Displacement means 13 through through hole 131
5. Here, if you accidentally overinflate the tire when refilling the air, and as a result, the tire air pressure becomes, for example, 10 atmospheres, the tire air pressure will directly act on the displacement means 135 if there is no blocking means. As a result, problems such as damage to the displacement means 135 and a decrease in the restoring force of the spring member occur. However, in this embodiment, when the air pressure inside the tire becomes high, such as 10 atmospheres, the shutter in FIG. 7) The shaft 139 moves to the left and the magnetic body 165 and the first magnet 157 attract each other, and the shaft cannot move further to the left, but the displacement means 135
moves to the left, and the connecting member 137 moves to the left while further bending the leaf spring 141. As a result, the check valve 1
23 also moves to the left, but when the check valve 123 reaches the position where the grommet 133 closes the communication hole 131, it does not move to the left any further and moves the grommet 133 to the base 1.
07 and closes the communication hole 131 to prevent tire air pressure from acting on the displacement means 135, the above-mentioned problem does not occur.

In the above, the air pressure of the tire decreases and the second magnet 1
59 is attracted to the magnetic body 167, and after the air pressure determination means 6a determines that the air pressure has decreased,
When the driver refills the air in the tire, the air pressure reliever $1
119 and the communication hole 131, the air pressure inside the tire acts on the displacement means 135, so that the air pressure of the tire is 1,
When it exceeds 8 kgr/cea'G, the displacement means 13
Since the differential pressure between the tire air pressure and the pressure chamber 163 is much smaller than the sum of the biasing force of 5 and the attractive force of the second magnet 159 and the magnetic body 167, the second magnet 159 and the magnetic body 167 are After being separated, the shaft 7) 139 moves to the left in FIG. 4 together with the displacement means 135, bringing the first magnet 157 and the magnetic body 165 into contact with each other, returning them to the initial state when the tire air pressure is normal. Can return. In this embodiment, the displacement means 135 is configured such that the tire air pressure is 1
, 7 kgf/cm2G, that is, when the tire air pressure and the pressure in the pressure chamber 163 are equal, the biasing amount of the spring is set to be 0.

Here, the attraction force between the first or second magnet and the magnetic body is g
, the stroke F of the connecting member 137 is x mm, and the displacement means 13
5 and the thrust of the connecting member 137 as F, the relationships between the case where the tire air pressure is 1.8 kgf/em2G and the case where the tire air pressure is 1.6 kgr/em2G are shown in Figs. 10 and 10. It is shown in Figure 11.

The operation of the tire pressure detection device of this embodiment described above is as follows:
Since this is realized by executing a predetermined processing program in the PU4, the processing is shown in Figs.
This will be explained with reference to the 70-chart shown in FIG. 17 and the timing chart shown in FIG. 18.

When the power is turned on, the CPU 4 executes the main routine shown in FIG. 12. In step 11, various registers, interrupt conditions, peripheral circuits, memory contents, etc. in the CPUJ are initialized, and then a loop from steps 112 to 114 is repeatedly executed. In step 112, a failure determination process is performed, followed by a recovery determination process in step 113, and the process proceeds to step 114, where the results of each determination process are output. The processing contents of steps 112 to 114 will be described later.

Here, the sensor 41 attached to the right front wheel is shown in Fig. 18 (
It is assumed that the tire pressure detection signal shown in , ) is outputted and input to the CPU 4 after being waveform-shaped as shown in FIG. It is assumed that the tire air pressure detection signal shown in FIG. 4(b) is outputted from one of them, and is input to the CPU 4 after being waveform-shaped as shown in FIG. 4(d). Of course, similar tire pressure detection signals are output from the sensors 41 of the remaining two wheels, but in order to simplify the explanation, these outputs are omitted in the timing chart of FIG. 18.

Based on the above waveform shaping output (Fig. 18(d)), CP
The various interrupt processes executed by U4 will be explained below.

At time t5 shown in FIG. 18, the CPU 4 receives
) When a rising edge of a waveform like that shown in FIG. 13 is input, a rising edge interrupt shown in the chart 70 in FIG.

In the rising interrupt processing, first, in step 121, the rising time t5 of the waveform is read from the value of the timer counter.Next, the process proceeds to step 122, where the value of tn stored in the memory is subtracted from t, and the waveform is at a low level. The time at which ΔTL was reached is calculated and stored in a memory named ΔTL. (Here, tn stores the time t2 at which the falling edge of the waveform occurred before t5.) Next, in step 123, the current time t is stored in tn. Next, in step 124, the interrupt generation condition of the corresponding bin of the CPU 4 is reset to the falling edge of the waveform, this rising edge interrupt processing is completed, and the process returns to the main routine.

Next, at time t6, the falling edge of the waveform is input to the bin of the CPU 4 corresponding to the same wheel, and a falling interruption shown in the 70-chart in Figure @14 occurs.

In the falling interrupt processing, in step 131, the falling time t6 of the waveform is read from the value of the timer counter.

Next, the process proceeds to step 132, where the value of tn is subtracted from t6 to calculate the time period during which the waveform was at the High level, and ΔT H
Store it in memory named . (As mentioned above, at this point tn=t, and ΔT II = ta −
t5). Next, in step 133, the current time t6
is stored in tn. Next, in step 134, the wheel speed is calculated to determine how many kte/h the wheel is currently rotating and stored in V on the RAM.

The calculation of the wheel speed is performed in step 12 of the rising interrupt processing.
ΔTL calculated in step 2 and step 1 of falling interrupt processing
ΔTs (−ΔT
L+ΔTH). Since the tire air pressure detection signal of the sensor 41 is inputted once for each rotation of the wheel, that is, the tire 11, the time ΔTs required for one rotation of the tire 11, ie, ΔTs, becomes the output cycle of the tire air pressure detection signal. If the diameter or outer circumference of the tire 11 is known, the speed of the wheel can be calculated based on the ΔTs. Said step 132
In step 135, the air pressure of the tires is determined. When the air pressure is above a predetermined value, the output waveform of the sensor 41 becomes as shown in FIG. 9 (,), and the waveform after waveform shaping becomes ΔT L >> ΔT as shown in FIG.
It is H. On the other hand, when the air pressure is below a predetermined value, the output waveform of the sensor 41 becomes as shown in FIG.
The waveform after waveform shaping is ΔT 11 as shown in the same figure (d).
>>ΔTL.

Therefore, the determination of tire air pressure is performed in step 12.
△TL obtained in step 2 and ΔTH obtained in step 132 above
If ΔTL>ΔT)I, the air pressure is normal, Δ
If TH>ΔTL, it is determined that the air pressure has decreased. Time t,
Since ΔTL>ΔT II at the time point, the air pressure is determined to be normal. The step 135 constitutes the tire air pressure determining means 6a to 6d.

Next, the process proceeds to step 136, where the interrupt counter is incremented by [1]. This interrupt counter is set for each wheel, and is used during the main routine and the scheduled interrupt processing routine (described later) to check whether a tire pressure detection signal from the sensor 41 is input and how many times the signal has been input. used in Next, in step 137, the interrupt generation condition of the corresponding bin of the CPU 4 is reset to the rising edge of the waveform, this falling interrupt processing is completed, and the process returns to the main routine.

Each of the above interrupt processes is performed by a sensor 41 arranged for each wheel.
This is performed for each input bin of the CPU 4 to which the tire pressure detection signal is input. Regarding the right front wheel, as shown in FIG. 18(C), side-turning processes are executed at times htt*+ty+t@ and ts+t1°.

FIG. 15 is a flowchart showing scheduled interrupt processing. The periodic interrupt process is executed by periodically generating an interrupt at regular intervals using a timer of the CPU 4, and is set so that the interrupt occurs every 6, for example, 20+*Sec. First, in step 141, the value of the interrupt counter set for each wheel is read.Next, in step 142, the value of the interrupt counter read at the previous scheduled interrupt stored in another RAM is compared. Determine whether there is a change. If there is a change, step 14
3, the value of the fixed time counter corresponding to that wheel is cleared to zero, and the fixed time interrupt is ended. If there is no change, the process proceeds to step 144, where the value of the fixed time counter corresponding to that wheel is incremented. Next, proceed to step 145,
It is determined whether the counter value of the regular counter is 100 or more, and if it is less than 100, the regular interrupt is terminated. If it is 100 or more, the wheel speed of the corresponding wheel is set to OK/h in step 146, and the regular time counter is set to 100 in step 147, and the interruption ends. By doing this, 20m 5
If no signal is generated from the sensor 41 for ecX100=2 seconds, the wheel speed can be set to Okm/l+. For example, as shown in FIGS. 18(a) and 18(c), in the case of the right front wheel where the sensor 41 fails and stops outputting the tire pressure detection signal No. 1 at time t, the time when the last interrupt occurred is ,. The wheel speed of the right front wheel is set to 0 kLIl/b due to a scheduled interruption that occurs at time t14, two seconds after the start. On the other hand, the other 3] 1! The correct wheel speed is calculated by the interruption at time t13.

The main routine process is also repeatedly executed between executions of each of the above interrupt processes.

Figure 16 shows the failure determination process (step 1) of the main routine.
12) is a flowchart showing details of step 12).

First, in step 401, it is determined whether three out of four sensors 41 are out of order. If it is malfunctioning, the wheel speed cannot be compared using only the remaining sensor 41, so the process immediately exits the failure determination processing routine and returns. sensor 4
If three sensors 1 are not faulty, the process advances to step 402, and the number of faulty sensors 41 is determined in order to change the process depending on the number of faulty sensors 41. Faulty sensor 41
If the number is 0, steps 403 to 407 are performed. In step 403, it is determined whether there is a wheel with a wheel speed of 0. Determination of wheel speed 0 is performed by the above-mentioned periodic interrupt processing. 11 If there are wheels with wheel speed 0,
Proceeding to step 404, it is determined whether the other 3]11 wheels are all at a predetermined wheel speed S, +a/h or higher. If the predetermined wheel speed S+kn+/h or more, step 405
It is determined whether the variation in wheel speed among the three wheels is within ±32 kmZ h. If the variation is within 32 km/h, the sensor 41 attached to the wheel whose wheel speed was determined to be 0 in step 406 is determined to be faulty, and the sensor 41 is stored in a predetermined memory in step 407. If a negative determination is made in each of the steps 403, 404, and 405, the process returns without performing failure determination processing.

Further, if it is determined in step 402 that the number of failed sensors 41 is 1, steps 408 to 41 are performed.
Process 2 is performed. Here, steps 403 to
Almost the same process as the process in step 407 is performed, but in step 409 it is determined that the predetermined wheel speed S is greater than or equal to km/h, and in step 410 the wheel speed variation is within ±82.
The difference is that the determination within 11 is compared between the wheel at wheel speed O and the remaining two wheels excluding the wheel in which the sensor 41 has failed. Then, in step 411, the sensor 41 attached to the wheel newly determined to have a wheel speed of O is determined to be malfunctioning, and in step 412, it is stored in a predetermined memory.

If the number of failed sensors 41 is determined to be 2 in step 402, steps 413 to 416 are performed. If there are wheels with wheel speed O, in step 414, the sensor 41 has failed and the two wheels have wheel speed O.
The wheel speed of the remaining wheel excluding the wheel is the predetermined wheel speed S,
It is determined whether the speed is equal to or greater than km/h. Predetermined wheel speed S l
km+/h or more, the wheel speed is set to O in step 415.
The sensor 41 attached to the wheel is determined to be malfunctioning, and is stored in a predetermined memory in step 416. For the sensor 41 that is determined to be malfunctioning through the above processing, the lamp control means 9 controls the lamp drive circuit 5 in step 114 of the main routine, and lights up the corresponding lamp among the lamps 10a to 10d to display a warning. .

FIG. 17 is a 70-chart showing details of the return determination process (step 113) of the main routine.

In step 501, it is determined whether or not there is a failed sensor 41. If there is no sensor 41, there is no need to perform recovery determination processing, and the process immediately returns. If there are any failed sensors 41, the number is determined in step 502. If the number of failed sensors 41 is 1, steps 503 to 508 are performed. In step 503, it is determined whether the wheel speeds of all the wheels to which non-faulty and normally functioning sensors 41 are attached are equal to or higher than a predetermined wheel speed S = kmZ l+. It is determined whether the speed variation is within S, km/h. If the variation is within ±S, plow/h, the process proceeds to step 505, and the wheel speed calculated based on the tire pressure detection signal output again from the sensor 41 determined to be malfunctioning and the wheel whose wheel speed is 53 ka/h or more is determined. The difference from the speed is ±6
5 to determine whether it is within +n/b. Then, in step 506, it is determined whether the affirmative judgments in steps 503, 504 and 505 have been made three times in a row.
If the failure occurs twice in a row, it is determined that the function of the sensor 41 that was determined to be malfunctioning in step 507 has returned to normal, and in step 508, the memory indicating that it is a malfunction is reset.

The appropriate value of S is approximately 2 to 5 km/h.

S2. It is appropriate that S is about the same as S. S, ,S, depends on the capability of the sensor 41, but - for example, 15ks/h
Good condition.

Note that if a negative determination is made in steps 503, 504, 505, and 506, the process returns without performing the return determination process.

If it is determined in step 502 that the number of failed sensors 41 is 2, steps 509 to 514 are performed. Here, the wheels subjected to the determination of the predetermined wheel speed S, +s/h or more in step 509 and the wheels subjected to the determination of wheel speed dispersion in step 510 are both two wheels, A recovery determination is made for each failed sensor 41, and in step 514, the memory indicating the failure is reset individually. The rest of the process is the same as the processing in steps 503 to 508 above.

Further, if it is determined in step 502 that the number of failed sensors 41 is 3, steps 515 to 519 are performed. Here, the normally functioning sensor 41 is 1
Since only one wheel is used for determining whether the wheel speed is equal to or higher than the predetermined wheel speed S3 km/h, the step for determining the dispersion between wheel speeds is omitted. The rest of the process is the same as the processing in steps 509 to 514 above. and,
Regarding the sensor 41 that has been determined to have recovered through the above process, the lamp control means 9 controls the lamp drive circuit 5 in step 114 of the main routine to
The corresponding lamp of 0d is turned off to notify that the sensor 41 has recovered from the failure. Step 503 above
~505. Steps 509-511 and step 515
-516 constitute the comparison means of the present invention.

Here, referring again to the timing chart of FIG. 18, the operation after time L14 will be described. Since the sensor 41 attached to the right front wheel malfunctions at time t1, the generation of waveforms stops after time t11 ((,), (e) in the same figure).Therefore, neither rising nor falling interrupts occur.
The wheel speed of the right wheel is the last falling interrupt time before time t. The value calculated by is maintained. and,
Time t. At time t14, two seconds after the start, the scheduled interrupt process is executed, and the wheel speed of the right wheel is set to OK/h. Therefore, in the failure determination processing routine in the main routine, if an affirmative determination is made in step 403 and the conditions in subsequent steps 404 and 405 are satisfied, it is determined that the sensor 41 attached to the right front wheel is malfunctioning. Then, one of the lamps 10a to 10d is turned on,
A warning is displayed to the driver that the front right wheel sensor 41 is out of order. On the other hand, as shown in FIGS. 18(b) and 18(d), the tire air pressure detection signal continues to be input to the other three wheels even after time tn, and the predetermined processing continues. In such a state, if a signal due to noise is output from the sensor 41 of the failed right front wheel between times t2 and t31, then at time t
Rising interrupt processing and falling interrupt processing are respectively executed in response to the rising and falling edges of waveform (c) between 2° and t3. The falling interrupt processing calculates the wheel speed of the right front wheel or the difference from the time when the immediately preceding falling interrupt occurred. The noise signal is input at a cycle shorter than the cycle of a normal tire pressure detection signal, and the calculated wheel speed is extremely high. Therefore, in the return determination processing routine of the main routine, the speed difference between the right front wheel and the remaining three wheels is greater than the predetermined speed S, km/h, and the condition of step 505 is not satisfied, so the return determination is made. At time t32, when the front right wheel sensor 41 returns to normal and outputs a tire air pressure detection signal for each rotation of the wheel, at time L33. Rise and fall interrupt processing are executed at L34 and time t3sft3G, respectively.

This time t1. The wheel speed of the right front wheel calculated in the falling interrupt process at time t31 is approximately equal to the wheel speed of the remaining three wheels calculated in the falling interrupt process at time t31.

In this way, step 503 of the return determination processing routine is performed based on each wheel speed calculated for each falling interrupt processing.
If the conditions 505 to 505 are met three times in a row, it is determined that the sensor 41 attached to the right front wheel has recovered from the failure.

As described above, when the sensor 41 that once stopped outputting a tire pressure detection signal due to a failure outputs a tire pressure detection signal again, the sensor 41 detects the wheel speed of the failed wheel and the wheel speed of the other wheel. When the difference between
・As a result, a sensor that has not recovered from a failure will not be mistakenly determined to have recovered.

In the above embodiment, the wheel speed of each wheel was used to determine sensor failure and recovery, but Δ
Ts=ΔTL+ΔTH (・Failure and recovery can be determined by using the time width data as is.

In addition, in the return determination processing routine, in order to determine the return of a failed sensor, it is necessary to calculate whether the wheel speed is approximately equal to that of the remaining wheels three times in a row in the falling interrupt processing for calculating the wheel speed. However, it is possible to use this as a time parameter (for example, each wheel speed is within a predetermined difference for 3 consecutive seconds), or to make a return determination by repeating the main routine loop a predetermined number of times. You can also do it.

"Effects of the Invention" The present invention has the above-described configuration, and inputs each period or each wheel speed calculated by the calculation means based on the tire pressure detection signal to the comparison means and compares the period or wheel speed between each period or wheel speed. When the error falls within a predetermined value, the return determination means determines that the tire pressure detection means that was determined to be malfunctioning has returned to normal, so it is assumed that the tire pressure detection means that was determined to be malfunctioning has returned to normal due to noise or the like. To prevent erroneous judgments such as
Our goal is to provide a highly reliable tire pressure detection device.

[Brief explanation of the drawing]

V-side i@1 Figure 1 is a diagram corresponding to complaints, Figure 2 is a schematic block diagram, Figure 3 is a sectional view showing the arrangement position of the tire air pressure detection means, and Figure 4 is the pressure detection unit constituting the tire air pressure detection means. 5(a) and 5(b) are perspective views of the connecting member of the pressure detection section, FIG. 6 is a perspective view of the leaf spring, and FIG. 7 is a perspective view of the main parts constituting the pressure detection section. , FIG. 8 is a sectional view of the tire air pressure detection sensor, FIG. 9 is a waveform diagram, FIGS. 10 and 11 are characteristic diagrams for explaining the thrust of the connecting member, etc., and FIG. 12 shows the main routine. 70-chart, FIG. 13 is a flowchart showing rising interrupt processing, FIG. 14 is a flowchart showing falling interrupt processing, FIG. 15 is 70-chart showing scheduled interrupt processing,
FIG. 16 is a flowchart showing the failure determination process.
FIG. 7 is a flowchart showing the return determination process, and FIG. 18 is a timing chart F. 1a to 1d...Tire air pressure detection means, 2...Controller, 4...CPU, 6a to 6d...Wheel speed calculation means, 7...Failure determination means, 8...Return determination means, 11... Tire, 39... Pressure detection unit, 41...
・Tire pressure detection sensor. 7p, 1 Figure 3 Figure 5 Figure 10 Figure 11 Return 120 Measures 13 Figure 1412 Return

Claims (1)

[Scope of Claims] Each wheel is provided with a tire pressure detection means that outputs a tire pressure detection signal in synchronization with the rotation of the wheel, and when one of the tire pressure detection means stops outputting, the remaining tire pressure detection means If the tire pressure detection means that has stopped outputting continues to output, the tire pressure detection device is equipped with a failure determination means that determines that the tire pressure detection means that has stopped outputting has failed, and the tire pressure detection device determines the cycle or wheel speed based on each of the tire pressure detection signals. a calculating means for calculating, a comparing means for inputting and comparing each calculated period or each wheel speed, and when the difference between each period or each wheel speed becomes within a predetermined value as a result of the comparison between the comparing means, A tire air pressure detecting device comprising: a return determining means for determining that the tire air pressure detecting means determined to be malfunctioning by the failure determining means has returned to normal.