JPH08159907A - Tire-balance measuring apparatus - Google Patents

Abstract

PURPOSE: To obtain a tire-balance measuring apparatus by which the amount and the position of an imbalance due to the front and rear vibration changed by the interference of a right-wheel tire and, a left-wheel tire are measured and corrected with good accuracy. CONSTITUTION: The rotation of a tire is detected by optical fiber sensors 10, 10'. The front and rear vibration of the tire is detected by accelerometers 7, 7'. On the basis of values of their detection signals, the amount and the position of an a imbalance between a right-wheel tire and a left-wheel tire are operated by an analytical-device body 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire balance measuring device for measuring the unbalance of left and right tires, and more particularly to a device for measuring the balance in the actual vehicle state in which the tires are mounted on a vehicle, so-called tire on the tire. It concerns car balancers.

[0002]

2. Description of the Related Art As a conventional tire balance measuring device, there is a technique for measuring the balance by detecting the longitudinal vibration of the suspension due to the tire unbalance, as described in JP-A-63-266331. . The left and right wheels of the front tire are connected via a steering linkage such as a knuckle arm and side rods, and vibration due to unbalance between the left and right wheels causes an interference phenomenon. For example, as shown in FIG. 4, when the tire is rotated when the unbalanced position angle of the right wheel is at 0 °, an unbalanced front-back exciting force F _R is generated. There is also an imbalance in the left wheel, and the relative position angle of the unbalance of the left wheel with respect to the right wheel is 0 °, that is,
If imbalance of the left and right wheels are the same phase, the excitation force F _L of the longitudinal direction to the left wheel is caused. When the unbalanced position angles of both the left and right wheels are both 0 °, that is, when the phases are the same, the exciting forces F _R and F _L both pull through the linkage, so the accelerations G _R and G _L generated on the left and right wheels Becomes smaller, and the fluctuation of the power spectrum of the front-back vibration in FIG. 5 indicates the value P _min of the valley portion. Further, when the relative position angle of the unbalance between the left and right wheels becomes 180 °, for example, in FIG. 4, when the unbalanced position angle of the left wheel is 180 °, the forces on the opposite sides are received, and therefore the left and right wheels are generated. The accelerations G _R and G _L become large, and the fluctuation of the power spectrum of the longitudinal vibration in FIG. 5 indicates the peak value P _max .

[0003]

As described above, in the prior art, the frequency of the primary component of the rotation signal generated in the tire due to the change in the relative position angle of the unbalance between the left and right tires (hereinafter referred to as the primary rotation frequency). The power spectra of the front and rear signals and the phase difference between the rotation signal and the vibration signal in (1) are changed. Further, in synchronization with this fluctuation, the steering shimmy, that is, the lateral vibration of the steering, which is an automatic excitation phenomenon around the kingpin of the control wheel, also fluctuates and beats. As described above, in the conventional tire balancer, the front-rear vibration fluctuates due to the interference, so that the amount of unbalance cannot be obtained accurately. In particular, in a front-wheel drive vehicle, the vibration of the drive system accompanying the drive of the front wheels is input as noise to the longitudinal acceleration, so it has been more difficult to improve the measurement accuracy. The present invention solves the above problems,
Tire balance measurement suitable for calculating the unbalance from the front-rear vibration that fluctuates due to the interference of the left and right wheels, and reducing the influence of the vibration of the opposite tire to improve the measurement accuracy of the tire unbalance amount and unbalance position. The purpose is to provide a device.

[0004]

FIG. 1 is a block diagram showing the configuration and function of an embodiment of the present invention. In FIG.
The rotation state detecting means 100 detects the number of rotations of both the left and right tires mounted on the vehicle, and corresponds to, for example, the reflection tapes 8 and 8'and the optical fiber sensors 10 and 10 'shown in FIG. It has a function of outputting a rotation signal and a rotation value (rpm) accompanying the rotation of the tire. The front-rear vibration detecting means 101 is attached to the rotation supporting portions of the left and right tires and detects the front-rear vibration of the rotation supporting portions. The front-back vibration detecting means 101 corresponds to, for example, the acceleration sensors 7 and 7'shown in FIG. The rotation power spectrum calculation means 102 calculates the rotation primary frequency from the rotation signal detected by the rotation state detection means 100. Rotation primary vibration spectrum calculation means 10
3 is rotation 1 detected by the rotation state detecting means 100.
The power spectrum of the front and rear vibration at the primary rotation frequency of the tire is calculated from the next frequency and the front and rear vibration detecting means 101. Further, the phase difference calculating means 104 calculates the phase difference between the front and rear vibrations from the power spectrum at the rotation primary frequency and the front and rear vibration power spectrum by the rotation primary vibration spectrum calculating means 103. The calculation of the front-rear vibration power spectrum and the calculation of the phase difference are performed by a phase difference calculation means in order to smooth the signal value using a procedure such as a moving average method when a noise component is large like an FF vehicle. 104
The first smoothing means 105 is provided in the latter stage, and the second smoothing means 10 is provided in the latter stage of the rotation primary vibration spectrum calculation means 103.
6 is preferably provided, but when the noise component is small enough to be ignored, the first and second smoothing means 104,
It is possible to omit 105. Subsequently, an unbalance calculation means 108 for calculating the amount of unbalance and a display means 109 are provided through the relative position calculation means 107 for calculating the unbalanced relative position angles of the left and right wheels.

Regarding another block diagram shown in FIG.
As in FIG. 1, a first smoothing means 105 and a second smoothing means 106 are provided. The difference from FIG. 1 is that after the smoothing process is performed, the peak portion of the longitudinal vibration power spectrum fluctuation by the rotation primary vibration spectrum calculation means 103,
This is a portion provided with a midpoint vector determination unit 109 for oscillating power spectrum variation for synthesizing the vectors of the valleys to obtain the midpoint. After that, the unbalance amount is calculated from the vibration vector and the phase vector at the midpoint in the same manner as in FIG. 1 and displayed.

The rotation power spectrum calculation means 102 and the rotation primary vibration spectrum calculation means 10 shown in FIG.
3, phase difference calculation means 104, first smoothing means 105, second smoothing means 106, relative position angle calculation means 107, unbalance calculation means 109, display means 110, and vibration power spectrum fluctuation shown in FIG. The midpoint vector determination means 108 corresponds to, for example, the portion of the analyzer body 13 shown in FIG.

[0007]

In FIG. 4, when the right wheel unbalance is at the 0 ° position, the left wheel unbalance relative position angle is 90 degrees.
In the case of °, the right wheel produces an exciting force of F _{R in} the 0 ° direction,
Meanwhile, the left wheel produces a excitation force F _L in the direction of 90 °. The longitudinal acceleration sensor of the right wheel in the normal state, resulting acceleration G _R is the acceleration in the right wheel which is transmitted from the left wheel (interference amount)
Occurs. That is, the longitudinal acceleration G _R of the right wheel because there is no interference from the left wheel, by detecting the longitudinal acceleration at this time, it is possible to accurately detect the tire unbalance of the right wheel. As for the left wheel, the longitudinal acceleration of the left wheel may be detected when the relative position angle of the right wheel becomes 90 ° at 0 °. When the unbalanced positions of the left and right wheels are known in advance, it is possible to detect when the left and right unbalanced position angle reaches 90 ° from the rotation signals of the left and right wheels. Thus, the detection is performed.

First, in FIG. 5, a peak portion and a valley portion are detected from the fluctuation of the longitudinal acceleration power spectrum, and an intermediate point between the peak portion (relative position angle 180 °) and the valley portion (relative position angle 0 °). That is, it is determined that P _mid is the relative position angle of 90 °, and the unbalance amount is calculated from the values of the phase difference θ _mid and P _mid at this position. Second, when the true acceleration due to unbalance acting on the left and right wheels in FIG. 4 G _R, and G _L, position of imbalance of the left and right wheels longitudinal acceleration including interference detected by the longitudinal acceleration sensor is the same phase , G _AR , G _AL ,
G _BR when the reverse phase, and G _BL. Further, when the influence coefficient of the interference between the left and right wheels is α, the following equation holds.

When the phase is the same, G _AR = G _R -αG _L (Equation 1) G _AL = G _L -αG _R (Equation 2) When the reverse phase is G _BR = G _R + αG _L (Equation 3) ) G _BL = G _L + αG _R (Equation 4) From the sum of (Equation 1) and (Equation 3), 2G _R = G _AR + G _BR (Equation 5) (Equation 2) Equation (Equation 4) Equation 2G from the sum of _{L = G AL + G BL ...} ( 6) (5) to detect the true longitudinal acceleration G _R due to unbalance of the right wheel from equation the same phase of the acceleration detected by the longitudinal acceleration sensor The sum of G _AR and antiphase G _BR should be calculated. Here, G _AR is the valley P _min phase θ _min in FIG.
Of a vector V _min with a magnitude and direction, G because _BR is a vector V _max with the magnitude and direction of P _max and theta _max, the vector obtained by combining the vector V _max, V _min as shown in FIG. 6 A vector V _mid whose magnitude is 1/2
Therefore, if the unbalance amount is calculated using this vector, it can be obtained accurately.

[0010]

2 and 3 show an embodiment of the present invention.
Is a perspective view showing a mechanical portion of an embodiment of the present invention, and FIG. 3 is a block diagram of an analysis device 13 of an embodiment of the present invention. In the following, the configuration in FIG. 2 mainly shows the left wheel side, but the right wheel side (the tire is not shown) is shown by adding “′”. In FIG. 2, a wheel 2 to which a tire 1 (left wheel) is attached is fastened to a hub 3 attached to a spindle 6 by bolts and nuts. The spindle 6 is connected to and supported by the strut 4 and the suspension lower arm 5. And the spindle 6
An acceleration sensor 7 is attached to the vehicle by adhesion or the like. The acceleration sensor 7 detects longitudinal vibration caused by an imbalance of the tire 1 or the like, and outputs an acceleration detection signal corresponding to the detected value. That is, the vibration signal generated by the imbalance can be detected as an acceleration sensor signal. Further, a reflection tape 8 is attached to the tire 1 or the wheel 2, and the reflected light from the reflection tape 8 is incident on an optical fiber sensor 10 arranged so as to face the reflection tape 8, and this optical fiber sensor An ON / OFF electric signal (rotation signal) of 1 pulse per one rotation of the wheel is output from 10. The acceleration sensor signal is amplified by the amplifier 11 and input to the analyzer body 13. The rotation signal output by the optical fiber sensor 10 is amplified by the optical fiber sensor amplifier 12 and input to the analyzer body 13. Also,
A remote switch 9 including a plurality of switch groups and display lamps is connected to the analyzer body 13. Although the left wheel has been described above, the right wheel is also provided with the acceleration sensor 7'and the optical fiber sensor 10 'as in the above, and the detection signal from the acceleration sensor 7'is transmitted through the amplifier 11' to the optical fiber sensor. The rotation signal from 10 'is input to the analyzer body 13 via the optical fiber sensor amplifier 12'.

Further, in FIG. 3, in the analysis device main body 13, a microcomputer 201 for performing main operations, recording and reading, and an A / D converter 20 for A / D converting a signal input to the microcomputer 201.
2. An anti-aliasing filter 20 that cuts high-frequency components of the acceleration detection signals from the acceleration sensors 7 and 7'and the rotation signals from the optical fiber sensors 10 and 10 '.
3, remote switch 9 and the microcomputer 2
Interface circuit 204 for performing waveform shaping and the like with 01, and liquid crystal display 2 for displaying calculation information, calculation results, etc.
05, a printer 206, and the like. The remote switch 9 includes a start switch 22 for instructing the start of sampling, a cancel switch 23 for canceling sampling and calculation, a reset switch 24 for returning the analysis program to the initial state, a lamp 25 lit at the end of the measurement, and an FF / FR. Car changeover switch 2
7 (details will be described later) and the like.

In the following, the operation and measurement by the above-mentioned device are carried out by the two-point method, that is, the dummy weight is not added and the position where the reflection tape 8 is attached (hereinafter referred to as 0 ° position) or the reflection tape 8 is used. A method will be described in which dummy weights are added to the positions opposite to the positions where they are attached (hereinafter referred to as 180 ° positions), respectively.

<First Embodiment> FIGS. 7 to 9 are flowcharts showing the contents of calculation in the above-described two-point method of the first embodiment. In this program, only the left wheel is displayed, but the right wheel is also measured and processed in the same manner. In FIG. 7, when the start switch 22 is turned on, measurement or calculation processing of rotation and vibration without a dummy weight and a phase difference between the rotation signal and the vibration signal is started. First, the rotation signal value of the left wheel and the acceleration sensor signal value are A / D converted at a predetermined sampling cycle, for example, every 7.8 msec, and reading is repeated until a predetermined sampling number, for example, 256 is reached (steps S1 to S1). S4). Next, the 256 sampled rotation signal values of the left wheel are read from the memory,
Fast Fourier transform (hereinafter referred to as FFT transform)
The primary rotation frequency f ₁ is detected from the power spectrum. Next, the acceleration signal of the left wheel is subjected to FFT conversion, and rotation 1
The value P _LN of the power spectrum at the next frequency f ₁ is calculated (steps S5 to S8). Next, rotation 1 of the rotation signal
From the power spectrum value at the next frequency f ₁ and the power spectrum value at the rotation primary frequency f ₁ of the acceleration sensor signal,
The phase difference θ _LN between the rotation signal and the vibration signal is calculated (step S9).

The calculation of the phase difference is performed as follows. That is, the rotation signal output from the optical fiber sensor is F
After FT conversion, if the rotation speed is constant, a predetermined frequency fp
One peak in the power spectrum occurs at. Similarly, the output of the acceleration sensor is FFT-converted, and the FFT conversion result of the rotation signal is the following (Equation 7), and the FF of the acceleration sensor signal is
The result of the T conversion is shown by the following equation (8), and the phase difference θ between the rotation signal and the vibration signal can be obtained by the following equation (9) from both equations. Fx (ω) = a + jb | Fx (ω) | = √ (a ² + b ² ) ... (Equation 7) Fy (ω) = c + jd | Fy (ω) | = √ (c ² + d ² ) (Equation 8)

[0015]

[Equation 9]

Next, in step S10, it is determined whether the vehicle is an FF vehicle or an FR vehicle. When the vehicle is an FF vehicle, smoothing is performed to obtain a tire rotation primary longitudinal vibration power spectrum P _LN and a phase difference θ _LN of the rotational vibration signal. That is, the previous P _Lθ1 , the previous P _Lθ2 , and the phase differences θ _Lθ1 and θ _Lθ2 of the power spectrum for performing the moving average calculation process are read from the memory and the average value is calculated. Although it is based on the simple moving average in FIG. 7, calculation is performed based on a weighted average value if necessary. It is also possible to carry out the same processing for FR vehicles. After performing the smoothing process, the previous P
_LN, that is, the difference ΔP _L from P _Lθ is calculated and the process proceeds to the next step (S11 to S14).

Next, the process proceeds to step S15 shown in FIG. 8, and when ΔP _L <0, ΔP _L0 > 0, it corresponds to the peak portion of the vibration power spectrum curve, so the values of P _Lθ and θ _Lθ are maximum values. As P _max and θ _max, and N _max = 1 as a flag for detecting a mountain portion. N _max = 1 That is, after the peak portion is detected, the values of P _LN and θ _LN are sequentially stored in the memory from a predetermined address until the valley portion is detected (S15 to S20). Next, when ΔP _L > 0 and ΔP _L0 <0, since it is the valley portion of the vibration power spectrum curve, the values of P _Lθ and θ _Lθ are set to P _min and θ _min as the minimum values, and the values shown in FIG. Go to step. The values of P _max and P _min are read from the memory and the average value P _AV is calculated. P _max stored in memory ~
The P _LN value of P _min and the average value P _AV are compared, P _LN closest to P _AV and the phase θ _LN at that time are selected, and P is the center value.
_mid and θ _mid (S24 to S26). Step S27
Then, it is judged that the data necessary for the unbalance calculation are gathered, and the measurement end lamp 25 is turned on. here,
The inspector stops driving the wheels and finishes the measurement without the dummy weights. Next, in step S28, 1 is added to the counter C ₁ . This counter C ₁ is a counter that determines whether the measurement is performed without a dummy weight, a measurement with a dummy weight added at a position of 0 °, or a measurement with a dummy weight added at a position of 180 °. Yes, if C ₁ = 1 then measurement without dummy weight, if C ₁ = 2 then measure at 0 ° position, if C ₁ = 3 then measure at 180 ° position. Show. Then C
If it is "YES", it is determined whether or not ₁ = 1, and if "YES", the average value P _{mid of the} mountain portion and the average value P _{mid of the} mountain portion are stored in a predetermined memory for the values P _L and θ _L of the state without dummy weight. Phase difference average θ
_mid is stored (steps S29 to S30). Next, returning to FIG. 7, when the dummy weight is attached at the 0 ° position and the same number of tire rotations as the previous time is reached, the start switch 22 is pressed to start sampling at the 0 ° position. . Then, the same measurement as in the state without the dummy weight is performed. When this is completed, the counter C ₁ = 2 is set by the same logic as that described above, so step S31 of FIG. 9 becomes “YES”, and the process proceeds to step S32, where the P _L and θ _L obtained this time are at the position of 0 °. Can be put in the memory area. Similarly, when a dummy weight is attached at a position of 180 °, C ₁ = 3, so step S2
9 and S31 is both "NO" the process proceeds to next step S33, currently obtained P _L, θ _L is placed in the memory area of the position of 180 ° (S31~S33). After that, P _L and θ _L with no dummy weight, with the dummy weight attached at the 0 ° position, and with the dummy weight attached at the 180 ° position, are read from the memory, respectively, and the unbalance amount and The unbalanced position is calculated (S34 to S36). The calculation of the unbalance amount is, as shown in FIG. 10, a state without dummy weight: a state having a size of P _L and a dummy weight added at a position of a vector V _L 0 ° having a phase θ _L : P _L0 And a phase with a phase of θ _{L0 and} a vector V _{L0 of} 180 ° with a dummy weight added: P
The vector is calculated from three vectors V _L180 having a size of _{L180 and} a phase of θ _{L180. When} the size of the line connecting the _ends of the vectors of V _L0 and V _L180 is d, d is 0. ° ← → 180 ° Obtained by disassembling in the axial direction.
If the weight of the dummy weight is W, the unbalance amount U
_B is expressed by the following (Equation 10) formula.

[0018]

[Equation 10]

In FIG. 10, since the delay of the transmission system is omitted in FIG. 10, θ _L is in the unbalanced direction and the correction direction is on the opposite side of 180 °, that is, θ _LB = θ _L + 180 °.

<Second Embodiment> FIGS. 12 to 14 are flow charts showing the contents of calculation in the two-point method of the second embodiment. In this program, only the left wheel is displayed, but the right wheel is also measured and processed in the same manner. The process up to the smoothing process in step S14 is the same as in the first embodiment. Next, a step of detecting peaks and valleys of the vibration power spectrum fluctuation is performed. ΔP _L > 0, ΔP
_{When L0} <0, the values of P _L0 and θ _L0 are taken as P _max and θ
_max and flag N _max = 1 (steps S15 to S)
36). When ΔP _L > 0 and ΔP _L0 > 0, P as a valley
The values of _L0 and θ _L0 are set to P _min and θ _min , and the flag N _min is set to 1 (steps S37 to S38). N _max = 0, N _min =
When 0, sampling is repeated, N _max = 1 and N
_{When min} becomes 1 (step S39). First, P _max and θ _max are read, and P _{max is set} to a value, and θ _max
A vector V _max having a direction of is determined (step S4
0). Next, determine the vector V _min to P _min size, the theta _min direction (step S41). These vectors V _max and V _min are combined to form a vector V whose size is ½.
Obtain _mid (step S42). The size of this vector V _mid is set to P _mid and the direction is set to θ _mid , and the measurement is ended (step S43). The subsequent steps are in accordance with the first embodiment.

According to the tire balance measuring apparatus of the above-mentioned embodiment, the balance state of the tire can be measured from the left and right wheels simultaneously or from only one wheel. Further, for example, the tire balance amount can be similarly obtained from the vertical vibration of the tire. This gives at least 20
It is possible to improve the measurement accuracy by%.

[0022]

The present invention reduces the influence of the vibration from the tires on the opposite side by calculating the unbalance from the front and rear vibrations that fluctuate due to the interference of the left and right wheels, and reduces the unbalance amount of the tires on the left and right wheels. The accuracy of measuring the unbalanced position can be significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and function of an embodiment of the present invention.

FIG. 2 is a perspective view showing a mechanical portion of the embodiment of the present invention.

FIG. 3 is a block diagram of an analysis apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing phases of excitation force and acceleration of left and right wheels.

FIG. 5 is a diagram showing a power spectrum and a rotation-acceleration phase.

FIG. 6 is a diagram showing a combined vector of a maximum vector and a minimum vector and a 1/2 vector.

FIG. 7 is a part of a flowchart showing the arithmetic processing steps of the first embodiment of the present invention.

FIG. 8 is a part of a flowchart following FIG.

9 is a part of a flowchart following FIG.

FIG. 10 is a vector diagram showing an unbalance vector of the present invention.

FIG. 11 is a block diagram showing a configuration and a function of an embodiment different from FIG. 1 of the present invention.

FIG. 12 is a part of a flowchart showing the arithmetic processing steps of the second embodiment of the present invention.

13 is a part of a flowchart following FIG.

FIG. 14 is a part of the flowchart following FIG. 13;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tire 2 ... Wheel 3 ... Hub 4 ... Strut 5 ... Suspension lower arm 7, 7 '... Acceleration sensor 8, 8' ... Reflective tape 9 ... Remote switch 10, 10 '... Optical fiber sensor 11, 11' ...
Amplifier 12, 12 '... Optical fiber sensor amplifier 13 ...
Analysis device main body 22 ... Start switch 23 ...
Cancel switch 24 ... Reset switch 25 ...
Lamp 100 ... Rotational state detection means 101 ... Front-back vibration detection means 102 ... Rotational power spectrum calculation means 103 ... Rotation primary vibration spectrum calculation means 104 ...
Phase difference calculating means 105 ... First smoothing calculating means 106 ...
Second smoothing means 107 ... Relative position angle computing means 108 ... Midpoint vector determination means 109 of vibration power spectrum fluctuation ... Unbalance computing means 110 ...
Display means 111 ... Vehicle type discrimination means 201 ... Microcomputer 202 ...
A / D converter 203 ... Anti-aliasing filter 204 ...
Interface circuit 205 ... Liquid crystal display 206 ...
Printers S1 to S43 ... Processing steps

Claims (4)

[Claims] 1. A rotation state detection means for detecting rotation signals of left and right tires mounted on a vehicle, a rotation power spectrum calculation means for outputting a rotation signal representing a primary rotation state from the rotation signal, and the rotation state. Is attached to the rotation support member of the tire for detecting the front-rear vibration detection means for detecting the front-rear vibration state of the tire, and outputting a front-rear vibration signal representing the state, based on the rotation signal and the front-rear vibration signal. A primary rotation vibration spectrum calculation means for outputting a longitudinal vibration signal in the primary rotation, a rotation signal representing the primary rotation state detected by the rotation state detection means and the primary rotation vibration spectrum calculation means. Phase difference calculating means for calculating the phase difference based on the longitudinal vibration signal in the first rotation, and the rotation signal obtained by the phase difference calculating means. Means for calculating the unbalanced relative position angle of the left and right tires from the phase difference between the front and rear vibration signals, and the front and rear vibration signal values in the primary rotation with respect to a predetermined value of the relative position angle, and the rotation signal and the front and rear vibration signals. A tire balance measuring device, comprising: an unbalance calculation means for calculating an unbalance amount of the left and right tires to be corrected and a relative position angle from the phase difference. 2. The predetermined value of the relative position angle is about 90 °
The tire balance measuring device according to claim 1, wherein 3. A rotation state detection means for detecting rotation signals of left and right tires mounted on a vehicle, a rotation power spectrum calculation means for outputting a rotation signal representing a primary rotation state from the rotation signal, and the rotation state. Is attached to the rotation support member of the tire for detecting the front-rear vibration detection means for detecting the front-rear vibration state of the tire, and outputting a front-rear vibration signal representing the state, based on the rotation signal and the front-rear vibration signal. A primary rotation vibration spectrum calculation means for outputting a longitudinal vibration signal in the primary rotation, a rotation signal representing the primary rotation state detected by the rotation state detection means and the primary rotation vibration spectrum calculation means. And a phase difference calculating means for calculating a phase difference based on the longitudinal vibration signal in the first rotation, and means for calculating the relative position angle. A vector in which the value of the peak portion of the spectrum fluctuation of the front-back vibration signal in the first rotation of the tire is the magnitude of the vector, and the phase difference in the peak portion is the direction of the vector; The value of the valley portion of the spectrum fluctuation of the vibration signal is set as the magnitude of the vector, and the vector having the phase difference in the valley portion as the vector direction is combined, and the unbalance amount and the position of the tire are calculated from these combined vectors. A tire balance measuring device having an unbalance calculating means for 4. A vehicle type discriminating means for discriminating between front wheel drive and rear wheel drive, and a smoothed arithmetic value of a phase difference between a rotation signal and a longitudinal vibration obtained by the phase difference arithmetic means based on the vehicle type discrimination information. First smoothing means, smoothing means for smoothing the power spectrum value of the longitudinal vibration obtained by the rotational primary vibration spectrum calculating means based on the vehicle type discrimination information, and the first smoothing means. Means for calculating the unbalanced relative position angle of the left and right tires from the phase difference between the rotation signal smoothed by the means and the longitudinal vibration, and the power spectrum value of the longitudinal vibration smoothed by the second smoothing means. The tire balance measuring device according to claim 1 or 3, further comprising: