JP4135593B2 - Tire pressure alarm device - Google Patents

Description

  The present invention relates to a tire pressure alarm device that indirectly detects the state of tire pressure in a vehicle and warns of a decrease in tire pressure based on the detection result.

  As this type of tire air pressure warning device, there are wheel speed detecting means for detecting the wheel speed of each wheel of the vehicle, and determination value deriving means for deriving a determination value based on each wheel speed detected by the wheel speed detecting means. And an air pressure decrease determining means for determining a decrease in the tire pressure of the wheel based on the determination value derived by the determination value deriving means, and when a decrease in the tire air pressure of the wheel is determined by the air pressure decrease determining means. There is known one provided with alarm means for warning that effect (see, for example, Patent Document 1).

In this apparatus, as shown in FIG. 2 of Patent Document 1, it is determined in step S105 whether or not the calculated rolling wheel right / left ratio R is within an effective range. The effective range here corresponds to a region having a predetermined width Rw (R _AVE −Aw <R <R _AVE + Rw) centering on the average value R _AVE as described above. If a positive determination is made here, the process proceeds to step S106, and if a negative determination is made, the process returns to step S102. By this processing, data outside the effective range is removed, and only data within the effective range is selected. Thereby, the data regarding the wheel speed detected by the wheel speed detecting means is selected so as to remove the data during turning of the vehicle, and the rotation state value and the slip state value are calculated using the selected data. It is possible to prevent a decrease in linear regression accuracy due to variations in rotational state values caused by turning of the vehicle, and it is possible to eliminate variations in pressure that are alarmed when the tire air pressure decreases.
JP 2002-234322 A (paragraph numbers 0014 and 0048, FIG. 2)

  However, in the data selection in the above-described device, the vehicle is not in an unstable traveling state (for example, a drift traveling state) in which the vehicle travels obliquely with respect to the traveling direction, but in a stable traveling state in which the vehicle travels in the traveling direction. In other words, there is a case where the data is not used even though it is possible to use the data in this state to derive the determination value and determine the decrease in the tire air pressure. That is, even a judgment value that does not have an adverse effect on judging the decrease in tire air pressure has been rejected. According to this, since the number of data to be adopted and thus the number of determination values to be derived are reduced, there is a problem that the detection accuracy of the tire pressure drop cannot be improved.

  It is an object of the present invention to employ as much valid data as possible by determining whether the driving state of a vehicle is a stable driving state or an unstable driving state, and as a result, tires using as many determination values as possible. It is to improve the detection accuracy of the air pressure drop.

In order to solve the above problem, the structural feature of the invention according to claim 1 is that wheel speed detection means for detecting the wheel speed of each wheel of the vehicle, and each wheel speed detected by the wheel speed detection means. A determination value deriving means for deriving a determination value based on the determination value, an air pressure decrease determining means for determining a decrease in the tire air pressure of the wheel based on the determination value derived by the determination value deriving means, and In the tire pressure alarm device having a warning means for warning that a decrease in tire air pressure is determined, whether the vehicle is in an unstable driving state in which the vehicle runs while tilting with respect to the full length direction or further comprising a running state determining means determines whether the stable running state traveling direction entire length direction of the vehicle is traveling at the matched state, the running state determining means, preceding vehicle And a front / rear wheel left / right ratio change amount difference calculating means for calculating a difference between both changes in the wheel speed right / left ratio of the rear wheel, and the absolute value of the difference calculated by the front / rear wheel left / right ratio change amount difference calculating means is a predetermined value If it is above, it is determined that the vehicle is in an unstable driving state in which the vehicle is inclined with respect to the full length direction. If the absolute value of the difference is smaller than a predetermined value, the vehicle traveling direction and the full length are determined. When it is determined that the vehicle is in a stable traveling state in which the directions match, and the traveling state determining unit determines that the vehicle is in an unstable traveling state, each wheel speed detected by the wheel speed detecting unit is determined. If the running state judging means judges that the vehicle is in a stable running state, each wheel speed detected by the wheel speed detecting means is adopted and a judgment value is derived using these wheel speeds. Determine tire pressure drop It is.

The structural feature of the invention according to claim 2 is that wheel speed detecting means for detecting the wheel speed of each wheel of the vehicle, and determination for deriving a determination value based on each wheel speed detected by the wheel speed detecting means. A value deriving unit, a pressure reduction determining unit for determining a decrease in the tire pressure of the wheel based on the determination value derived by the determination value deriving unit, and a decrease in the tire pressure of the wheel by the air pressure decrease determining unit. In the case, in the tire air pressure alarm device provided with a warning means for warning that effect, the front-rear wheel left-right ratio change amount difference calculating means for calculating the difference between both the wheel speed right-left ratio of the front wheel and the rear wheel of the vehicle If the absolute value of the difference calculated by the front / rear wheel left / right ratio change difference calculating means is equal to or greater than a predetermined value, the vehicle is in an unstable driving state in which the vehicle is inclined with respect to the full length direction. And when the absolute value of the difference is smaller than the predetermined value, the vehicle further includes a traveling state determination unit that determines that the traveling state is a stable traveling state in which the traveling direction of the vehicle coincides with the full length direction. When the traveling state determining means determines that the vehicle is in a stable traveling state, the determination value deriving means derives a determination value, and based on this derived result, the air pressure determining means determines a decrease in the tire air pressure of the wheel, Based on the determination result, the alarm means warns of a decrease in tire air pressure, and when the traveling state determining means determines that the vehicle is in an unstable driving state, the determination value is derived by the determination value deriving means, and the air pressure determining means The determination of the decrease in the tire air pressure of the wheel due to the above and the processing of the alarm for the decrease in the tire air pressure by the alarm means are prohibited.

In the invention according to claim 1 configured as described above, the traveling state determination unit determines whether the vehicle is in an unstable driving state or a stable driving state, and the traveling state determination unit determines that the vehicle is in a non-stable driving state. When it is determined that the vehicle is in a stable running state, each wheel speed detected by the wheel speed detecting unit is not adopted, and when the driving state determining unit determines that the vehicle is in a stable running state, wheel speed detection is performed. Each wheel speed detected by the means is adopted, and a determination value is derived using these wheel speeds to determine a decrease in tire air pressure. Therefore, a large amount of effective data when the vehicle is in a stable running state is adopted, and a decrease in tire air pressure can be determined based on a number of effective judgment values derived from these data. Detection accuracy can be improved.
Further, the traveling state determination means includes front / rear wheel left / right ratio change amount difference calculating means for calculating a difference between both changes in the wheel speed right / left ratio of the front wheel and rear wheel of the vehicle, and the front / rear wheel left / right ratio change difference difference calculating means. When the absolute value of the difference calculated by the above is greater than or equal to a predetermined value, it is determined that the vehicle is in an unstable driving state, and when the absolute value of the difference is smaller than the predetermined value, it is determined that the vehicle is in a stable driving state. Therefore, the vehicle running state can be determined by using the wheel speed detecting unit originally provided in the vehicle without providing another detecting unit for detecting the running state. Cost reduction and downsizing of the apparatus can be achieved.

In the invention according to claim 2 configured as described above, the difference between both the front and rear wheel speed ratios between the front and rear wheels of the vehicle is calculated by the front / rear wheel left / right ratio change difference calculation means, and the running state determination means. If the absolute value of the difference calculated by the front-rear wheel left / right ratio change amount difference calculating means is greater than or equal to a predetermined value, it is determined that the vehicle is in an unstable driving state, and the absolute value of the difference is smaller than the predetermined value. In this case, when the vehicle is determined to be in a stable traveling state, and the traveling state determining unit determines that the vehicle is in a stable traveling state, the determination value deriving unit derives a determination value, and based on the derived result The air pressure determination means determines a decrease in the tire air pressure of the wheel, and the alarm means warns the decrease in the tire air pressure based on the determination result. On the other hand, when the traveling state determining means determines that the vehicle is in an unstable traveling state, the determination value is derived by the determination value deriving means, the determination of the decrease in the tire pressure of the wheel by the air pressure determining means, and the tire by the alarm means Prohibit each processing of the alarm of low air pressure. Therefore, since the determination value is derived based on the wheel speed when the vehicle is in the stable traveling state and the decrease in the tire air pressure is determined based on the determination value, conventionally, the vehicle is in the stable traveling state. Since the determination value that has not been derived is also derived, and a decrease in tire air pressure can be determined based on these many effective determination values that have been derived, it is possible to improve the detection accuracy of the decrease in tire air pressure.

  Hereinafter, an embodiment of a tire pressure alarm device according to the present invention will be described with reference to the drawings. A block diagram of this tire pressure alarm device is shown in FIG. The tire air pressure alarm device includes wheel speed sensors SFL, SFR, SRL, SRR, a control device 10, and an alarm device 20. Wheel speed sensors SFL, SFR, SRL, and SRR detect wheel speeds of the left and right front and rear wheels WFL, WFR, WRL, and WRR, and pick up rotations of the left and right front and rear wheels WFL, WFR, WRL, and WRR, respectively. As a result, a pulse train signal having a period inversely proportional to each rotation speed is output to the control device 10.

The control device 10 has a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected via a bus. The CPU executes a program corresponding to the flowchart of FIG. 2, derives a determination value based on the input wheel speed, determines a decrease in tire air pressure based on the determination value, and responds to the determination result. The alarm device 20 is controlled, the ROM stores the program, and the RAM temporarily stores calculation values related to control.

  The alarm device 20 is configured by a display (for example, a warning lamp, CRT, liquid crystal, etc.), and displays a tire whose air pressure has decreased in response to a command from the control device 10. Note that the alarm device may be constituted by a sound generating device such as a speaker. In this case, it is only necessary to announce the tire with reduced air pressure by sound.

  Next, the operation of the tire pressure alarm device configured as described above will be described with reference to the flowchart of FIG. The control device 10 executes a program corresponding to the flowchart when an ignition switch (not shown) of the vehicle M is in an on state.

  The control device 10 determines whether the vehicle is in a stable running state or an unstable running state after starting execution of the program in step 100 of FIG. 2 (steps 102 to 108). Specifically, in step 102, the control device 10 determines the wheel speeds VFL, VFR, VRL, VRR of the wheels WFL, WFR, WRL, WRR from the pulse train signals input from the wheel speed sensors SFL, SFR, SRL, SRR. The front wheel speed ratio RpL_F (t) is derived from the following formula 1 based on the wheel speeds VFL and VFR of the left and right front wheels, and the rear speed is determined based on the wheel speeds VRL and VRR of the left and right rear wheels. The wheel speed right / left ratio RpL_R (t) of the wheel is derived from the following formula 2, and the derived wheel speed right / left ratios RpL_F (t) and RpL_R (t) of the rear wheel are stored in the control device 10 or a storage device (not shown). .

(Equation 1)
RpL_F (t) = VFR / VFL
(Equation 2)
RpL_R (t) = VRR / VRL
In step 104, the control device 10 determines the wheel speed right / left ratio RpL_F (t−) of the front and rear wheels derived and stored last time from the wheel speed right / left ratios RpL_F (t) and RpL_R (t) derived this time. 1) By subtracting RpL_R (t−1), both changes ΔRpL_F and ΔRpL_R of the wheel speed left-right ratio of the front wheels and the rear wheels are derived. That is, the change amount ΔRpL_F of the front wheel speed / right / left ratio is derived from the following equation (3), and the change amount ΔRpL_R of the rear wheel wheel speed / left / right ratio is derived from the following equation (4).

(Equation 3)
ΔRpL_F = RpL_F (t) −RpL_F (t−1)
(Equation 4)
ΔRpL_R = RpL_R (t) −RpL_R (t−1)
In step 106, the control device 10 calculates the difference DS between both the change amounts ΔRpL_F and ΔRpL_R of the wheel speed left-right ratio of the front wheels and the rear wheels derived in step 104. That is, the difference DS is derived from Equation 5 below.

(Equation 5)
DS = ΔRpL_F−ΔRpL_R
In step 108, if the absolute value | DS | of the difference DS calculated in step 106 is greater than or equal to a predetermined value DS_th, the control device 10 determines that the vehicle is in an unstable driving state and determines the absolute value of the difference DS. If | DS | is smaller than the predetermined value DS_th, it is determined that the vehicle is in a stable running state. Here, the stable running state means that the vehicle M travels in the traveling direction A (the tangential direction of the turning circuit with the radius R indicated by the broken line, and indicated by the arrow) and the full length direction B as indicated by the broken line in FIG. A state where the vehicle M travels in a matched state, for example, a state where the vehicle M is gripping. Further, the unstable driving state refers to a state in which the vehicle M travels in a state inclined with respect to the full length direction B as shown by a solid line in FIG. A state where the vehicle travels in a state where the direction M is inclined, for example, a state where the vehicle M is drifting.

  When determining that the vehicle is in a stable running state in step 108, the control device 10 advances the program to step 110 and the subsequent steps, derives a determination value, that is, a wheel speed deviation D based on each wheel speed, and outputs the determination result. Based on this, a decrease in the tire air pressure of the wheel is determined (steps 110 to 122). If it is determined that the vehicle is in an unstable driving state, the program is returned to step 102 and the processes of steps 102 to 108 described above are executed again.

  In the present embodiment, the air pressure decrease is not determined based on only one wheel speed deviation D, and the air pressure decrease is based on the average value of the latest predetermined number (for example, L) of wheel speed deviations D. Is determined. Accordingly, by preventing the determination based on the inappropriate wheel speed deviation D, it is possible to accurately and reliably determine the decrease in air pressure based on the appropriate wheel speed deviation D. Specifically, in step 110, the control device 10 derives the wheel speed deviation D from the following equation 6 based on the wheel speeds VFL, VFR, VRL, and VRR previously derived in step 102.

(Equation 6)
D = VFR / VFL−VRR / VRL
In step 112, the control device 10 integrates the wheel speed deviation D derived this time into the integrated value Dsum integrated up to the previous time, and in step 114, counts up the number of integrations C by “1”. In step 116, it is determined whether or not the cumulative number C has reached a predetermined number (for example, L times). When the cumulative number C is less than the predetermined number L, the control device 10 returns the program to Step 102 and repeatedly executes the processing of Step 102 to Step 116 described above until the cumulative number C becomes equal to or greater than the predetermined number L. .

  When determining that the number of integrations C has reached a predetermined number (for example, L times) in step 116, the control device 10 executes the processing after step 118 to determine the decrease in air pressure. Specifically, in step 118, the control device 10 derives an average value Dave of the integrated values Dsum integrated L times by the processing of steps 110 to 116 from the following formula 7. In step 120, the number of integrations C is cleared to derive the next average value Dave.

(Equation 7)
Dave = Dsum / C
In step 122, when the absolute value | Dave | of the average value Dave of the wheel speed deviation D derived in step 118 is equal to or greater than the predetermined value Dth, the control device 10 determines that the tire air pressure has decreased, and the average When the absolute value | Dave | of the value Dave is less than the predetermined value Dth, it is determined that the tire air pressure has not decreased. If the control device 10 determines in step 122 that the tire air pressure has decreased, the control device 10 advances the program to step 124 and sends a command to the alarm device 20 to control the air pressure decrease. Thereafter, the program is advanced to step 126 to end the program once. If it is determined that the tire air pressure has not decreased, the program returns to step 102 to execute the above-described processing.

  For example, when the vehicle travels in a slalom, the wheel speeds VFL, VFR, VRL, VRR are detected every predetermined short time, and each time the detection is made, the difference between the change amounts ΔRpL_F, ΔRpL_R of the front wheel and rear wheel wheel speeds. DS and wheel speed deviation D (to be described later) are derived, and the relationship between these derived difference DS and wheel speed deviation D is shown in FIG. According to the present embodiment, when it is determined that the vehicle is in an unstable driving state, that is, when the difference DS is less than −DS_th or greater than DS_th, the wheel speed deviation D is not adopted. If it is determined that the vehicle is in a stable running state, that is, if the difference DS is greater than or equal to −DS_th and less than or equal to DS_th, the wheel speed deviation D is adopted.

  As is clear from the above description, in the present embodiment, it is determined whether the vehicle is in an unstable driving state or in a stable driving state by the driving state determination means composed of steps 102 to 108. When the traveling state determining means determines that the vehicle is in an unstable traveling state, the wheel speeds detected from the wheel speed sensors SFL, SFR, SRL, SRR are not adopted, and the traveling state determining means is the vehicle. If it is determined that the vehicle is in a stable running state, the wheel speeds detected from the wheel speed sensors SFL, SFR, SRL, SRR are adopted, and the wheel speed deviation (determination value) D is calculated using these wheel speeds. Derived (step 110), and in steps 110 to 122, a decrease in tire air pressure is determined. Therefore, a large amount of effective data when the vehicle is in a stable running state is adopted, and a decrease in tire air pressure can be determined based on a number of effective judgment values derived from these data. Detection accuracy can be improved.

  Further, the traveling state determining means includes front and rear wheel left / right ratio change amount difference calculating means (step 106) for calculating a difference DS between both wheel speed ratios ΔRpL_F and ΔRpL_R of the front wheel and rear wheels of the vehicle. When the absolute value | DS | of the difference DS calculated by the wheel left / right ratio change amount difference calculating means is equal to or larger than the predetermined value DS_th, it is determined that the vehicle is in an unstable driving state, and the absolute value | DS | If it is smaller than the value DS_th, it is determined that the vehicle is in a stable running state (step 108). Therefore, by using the wheel speed detecting means (wheel speed sensors SFL, SFR, SRL, SRR) originally provided in the vehicle without providing another detecting means for detecting the running state, the running state of the vehicle. Therefore, the cost of the device itself can be reduced and the size of the device can be reduced.

  Further, in step 106, a difference DS between both the change amounts ΔRpL_F and ΔRpL_R of the wheel speed right / left ratio of the front wheel and the rear wheel of the vehicle is calculated, and the absolute value | DS | of the difference DS calculated in step 106 by step 108 is predetermined. If the value DS_th is greater than or equal to the value DS_th, it is determined that the vehicle is in an unstable driving state. If the absolute value | DS | of the difference DS is smaller than the predetermined value DS_th, it is determined that the vehicle is in a stable driving state. If it is determined in step 108 that the vehicle is in a stable running state, a determination value is derived (steps 110 to 118), and a decrease in tire air pressure of the wheel is determined based on the derived result (step 122). Based on the determination result, the alarm means warns of a decrease in tire air pressure (step 124). On the other hand, if it is determined in step 108 that the vehicle is in an unstable driving state, derivation of the determination value (steps 110 to 118), determination of a decrease in tire air pressure of the wheel (step 122), and a tire by the alarm means Each process of the air pressure drop alarm (step 124) is prohibited. Therefore, since the determination value is derived based on the wheel speed when the vehicle is in the stable traveling state and the decrease in the tire air pressure is determined based on the determination value, conventionally, the vehicle is in the stable traveling state. Since the determination value that has not been derived is also derived, and a decrease in tire air pressure can be determined based on these many effective determination values that have been derived, it is possible to improve the detection accuracy of the decrease in tire air pressure.

1 is a block diagram showing an embodiment of a tire pressure alarm device according to the present invention. It is a flowchart showing the program run with the control apparatus shown in FIG. It is a figure for demonstrating the driving | running | working state of a vehicle. It is a figure which shows the data employ | adopted as a wheel speed deviation, and is employ | adopted.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Alarm apparatus, Sfl, Sfr, Srl, Srr ... Wheel speed sensor, Left and right front-rear wheels Wfl, Wfr, Wrl, Wrr.

Claims (2)

Wheel speed detecting means for detecting the wheel speed of each wheel of the vehicle;
Determination value deriving means for deriving a determination value based on each wheel speed detected by the wheel speed detecting means;
An air pressure decrease determining means for determining a decrease in tire air pressure of the wheel based on the determination value derived by the determination value deriving means;
In the tire pressure alarm device comprising a warning means for warning that a decrease in tire pressure of the wheel is determined by the pressure drop determination means,
Travel that determines whether the vehicle is in an unstable travel state in which the vehicle is tilted with respect to the full length direction, or whether the vehicle is in a stable travel state in which the travel direction of the vehicle coincides with the full length direction Further comprising a state determination means,
The traveling state determination means includes front / rear wheel left / right ratio change amount difference calculating means for calculating a difference between both changes in the wheel speed right / left ratio of the front and rear wheels of the vehicle,
When the absolute value of the difference calculated by the front / rear wheel left / right ratio change amount difference calculating means is equal to or greater than a predetermined value, the vehicle is in an unstable driving state in which the vehicle is inclined with respect to the full length direction. And when the absolute value of the difference is smaller than the predetermined value, it is determined that the vehicle is in a stable traveling state in which the traveling direction of the vehicle coincides with the full length direction,
If the traveling state determining means determines that the vehicle is in an unstable traveling state, the wheel speeds detected by the wheel speed detecting means are not adopted, and the traveling state determining means determines that the vehicle is in a stable traveling state. If it is determined that there is a wheel speed detected by the wheel speed detecting means, the wheel speed is used to derive the determination value, and a decrease in the tire air pressure is determined. Tire pressure alarm device. Wheel speed detecting means for detecting the wheel speed of each wheel of the vehicle;
Determination value deriving means for deriving a determination value based on each wheel speed detected by the wheel speed detecting means;
An air pressure decrease determining means for determining a decrease in tire air pressure of the wheel based on the determination value derived by the determination value deriving means;
In the tire pressure alarm device comprising a warning means for warning that a decrease in tire pressure of the wheel is determined by the pressure drop determination means,
Front / rear wheel left / right ratio change amount difference calculating means for calculating a difference between both changes in the wheel speed right / left ratio of the front wheel and rear wheel of the vehicle;
When the absolute value of the difference calculated by the front / rear wheel left / right ratio change amount difference calculating means is equal to or greater than a predetermined value, the vehicle is in an unstable driving state in which the vehicle is inclined with respect to the full length direction. And a traveling state determining means that determines that the traveling state is a stable traveling state in which the traveling direction of the vehicle coincides with the full length direction when the absolute value of the difference is smaller than the predetermined value. ,
When the traveling state determining means determines that the vehicle is in a stable traveling state, the determination value deriving means derives a determination value, and based on the derived result, the air pressure determining means reduces the tire air pressure of the wheels. The warning means warns of a decrease in tire air pressure based on the determination result, and when the traveling state determining means determines that the vehicle is in an unstable traveling state, the determination by the determination value deriving means A tire air pressure alarm device that prohibits each processing of derivation of values, determination of a decrease in tire air pressure of the wheel by the air pressure determining means, and alarm of a decrease in tire air pressure by the alarm means.

Images