JPH01248010A - Throttle sensor and temperature compensation - Google Patents

Abstract

PURPOSE:To realize a highly accurate throttle sensor with limited dependence on temperature, by combining a permanent magnet of a magnetic flux source with a Hall element for detecting a magnetic flux in such a manner as to be opposite to each other in the polarity of temperature coefficient. CONSTITUTION:A silicon based Hall IC (a) with a positive temperature coefficient as Hall element 10 and a rare earth permanent magnet (b) with a negative temperature coefficient as permanent magnet 8 of a magnetic flux generation source are combined in such a manner as to be opposite to each other in the polarity of temperature efficient. In this manner, both temperature coefficients cancel each other to obtain a highly accurate sensor with a temperature compensation. To deal with separate variations, values obtained in the full closure at the startup, and in the full closure at the stoppage after the startup are utilized to computer respective temperature coefficients so that a compensation is accomplished by the temperature coefficients. This enables the realization of a highly accurate sensor with limited dependence on temperature.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the detection of the throttle valve opening of an internal combustion engine.
In particular, it relates to improving the accuracy of non-contact throttle sensors.

[Conventional technology]

The throttle sensor converts the rotation angle of the valve into an electrical signal, and most of the throttle sensors use a potentiometer type. However, this method has problems with reliability, such as poor contact due to abrasion of the resistive coating, and malfunction due to vibration when mounted on a vehicle.

As a countermeasure to this problem, contactless methods are being tried.

For example, a rotary encoder method using a photo sensor,
There is a method using a Hall element. In the former case, the structure becomes complicated because a plurality of photosensors are required for each code.

An example of the latter is, for example, Japanese Patent Application Laid-open No. 58-211603 ``
There is an angle sensor. This is a method in which two magnetic circuits are provided and the difference in magnetic flux density in one magnetic circuit is converted into voltage by a Hall IC, but it is necessary to provide two magnetic circuits with opposite polarities. There is also an example that mentions temperature drift compensation (Japanese Unexamined Patent Publication No. 140103/1983), but this is still a system in which two magnetic circuits are provided.

[Problems to be Solved by the Invention] The above-mentioned conventional technology using a Hall element is an example in which two magnetic circuits with opposite polarities are used, and the problem is that the more complicated the structure, the larger the volume. there were.

An object of the present invention is to provide a throttle sensor that can compensate for temperature drift, variation, etc. even in one magnetic circuit.

[Means to solve the problem]

The above object can be achieved by a selected combination of permanent magnets and Hall ICs constituting the magnetic circuit. Furthermore, since the temperature coefficient is determined each time and temperature compensation is performed to compensate for variations in the permanent magnet and Hall IC and changes over time, more accurate characteristics can be obtained.

[Effect]

Temperature coefficient of permanent magnet used as magnetic circuit and Hall IC
Temperature compensation is performed by combining factors that cancel out their own temperature coefficients. Furthermore, regarding individual variations, individual temperature coefficients are calculated using values such as full open at start and full open at stop after start, and compensation is performed using the temperature coefficient. By performing these compensations, a throttle sensor with a simple structure and high accuracy can be realized.

〔Example〕

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

FIG. 2 is a schematic diagram of the structure of the sensor of the invention.

In FIG. 2, numeral 3 denotes a valve shaft connected to a throttle valve (not shown), and numeral 6 denotes a magnetic field source holding member, which is made of, for example, iron-aluminum material. 7 is a magnetic field generation source with a permanent magnet 8;
It consists of a yoke 9 which has approximately the same radius as the permanent magnet 8 and is joined to the magnet 8.

The yoke 9 is made of a ferromagnetic material, and the permanent magnet 8 is magnetized in a direction along the valve axis. The surface 7a of the yoke 9 opposite to the joint surface with the permanent magnet 8 has a structure such that its height changes from hl to h2 along the circumferential direction of rotation. A Hall element (Hall IC) 10 is provided at a position facing the surface 7a.

The magnetic flux Φ from the magnetic field generation source 7 passes through the Hall element 10. Since the height of the yoke having the surface 7a changes from hl to h2, the interval equivalently changes with respect to the Hall element 1o. The valve shaft 3 rotates according to the valve opening degree, and the gap between the yoke 9 and the Hall element 10 changes according to the rotational displacement θTH, so a Hall output voltage is obtained according to the change in the magnetic flux Φ passing through the Hall element.

Next, individual characteristics will be explained. Figure 3 (A)-(D
) shows an example of the characteristics of a Hall element. 3(A) shows a change in the output voltage with respect to a change in the magnetic flux density B of the Hall element 10, and FIG. 3(B) shows a change in the magnetic flux density B due to a change in the rotation angle θTH of the valve shaft 3. Similarly, FIG. 3(C) shows the output voltage Vo of the Hall element 10 as a result of changes in the rotation angle/Jru of the valve shaft 3. Figure 3 (D) shows the ambient temperature Ta
The voltage V proportional to the internal temperature of the Hall element with respect to the change in
Indicates T. This VT is the voltage measured at the terminal provided on the Hall IC. Figure 3 (E) is Hall I
Indicates C.

Here, a typical example of the temperature characteristics of a permanent magnet and a Hall IC is shown in the fourth example.
As shown in the figure. (a) is the output voltage V of silicon-based Hall IC
In most cases, the temperature characteristic of o exhibits a positive temperature coefficient. - For example, it has a magnitude of about +-0.05%/'C. In addition, FIG. 3B shows changes in magnetic flux density with respect to temperature changes of the rare earth permanent magnet. An example of the temperature coefficient is about -0.04%/'C, and its variation is small compared to the temperature coefficient of silicon-based Hall ICs. The present invention focuses on the polarity and magnitude of this temperature coefficient, and attempts to realize a throttle sensor with low temperature dependence by combining these. FIG. 1 shows the overall configuration of these devices. The sensor having the configuration shown in FIG. 2 is protected by the sensor cover 20 shown in FIG.
r is derived to the outside. Also, 16 and 18 are the ignition switches respectively. Fully open throttle switch, 35
3 represents a pass line, and 30 represents an electronic control unit that performs various calculation processes.

The present invention is based on the temperature coefficient of the permanent magnet and the Hall IC as described above.
The objective is to obtain a throttle sensor with good temperature characteristics, such as the one shown in Figure 4 (C), by combining the sensors so that the temperature coefficients of I can't afford it. Temperature coefficient correction is required. The correction will be described below.

FIGS. 5(A) and 5(B) show an explanatory flow of a method for calculating and correcting the temperature coefficient at the fully closed position of the valve shaft by the MPU 36.

First, in step 52, the ignition key is turned from OFF to ON.
Determine whether it has become. Specifically, the signal from the ignition switch 16 shown in FIG. 1 is taken in through the digital input port 34 and judged. Step 5
When it is determined in step 2 that the ignition switch is OFF→ON, in step 54, the voltage VT representing the internal temperature of the Hall IC and the output voltage VO of the Hall IC are immediately read through the analog input port 32. VTI here.

V o i generally represents the i-th 0FF-+ON operation of the ignition key switch (hereinafter this suffix will be used with the same meaning).
. Conversion calculations are performed from VTI and Vot, respectively, to determine the internal temperature TI of the Hall IC and the valve shaft opening 0Tlll.

The engine enters the operating state and the temperature rises. If the internal temperature of the IC at that time (converted from VT) is TI, the temperature compensation amount can be expressed as Votcomp in step 64. Here, α(a-,) is the temperature coefficient determined in the previous operation. This is shown in FIG.

Then, as shown in step 70, until the ignition key changes from ON to FF, the output voltage VO of the Hall IC is the output voltage (Vo
w) is obtained.

On the other hand, when the i-th ignition key FF→N is determined, the temperature coefficient α1 is calculated, and the calculation flow will be explained below.

In step 56, θdTH is calculated. θT)+(1-1
) is the (i-1)th key switch OF F-I
This is the valve shaft opening degree when ON. The deviation between that and the valve shaft opening degree oTI11 obtained in step 54 this time (ith time) is &
I'm playing dru. This is based on the premise that there will not be much deviation in the ambient temperature or the internal temperature of the Hall IC when the key switch is OFF.

Therefore, as shown in step 58, the magnitude of θdru is determined. oe is a predetermined value, and the magnitude relationship with the deviation 1 (ldrol in step 56 is determined. If 1θd7Hl≧Oe, the valve shaft opening degree when the i-th key switch changes from OFF to ON is determined in step 6o.
It is calculated as OT old=Odr++θT)+(mu−1). Therefore, θT)l+ in step 60 is the corrected valve shaft opening degree.

Further, when 1θdtH1<oe in step 58, as shown in step 62, the current valve shaft opening θTH+ is the previous valve opening θTl+(1−1)
1). Therefore f? in step 62? THi can also be said to be the corrected valve shaft opening degree. The valve shaft opening degree θTh at this step 60°62 is used to calculate the temperature coefficient and is used for the next time ((i
For example, the RAM 38
The calculation program is stored in the ROM 37.

Next, in step 66, the ignition key switch is turned on.
-+OF When detecting the change to F, step 6
8, read the Hall IC internal temperature voltage vTic and output voltage V o + c immediately after that, and calculate the temperature T r
c, θTH+c. Further, the determination in step 66 may be made by logically multiplying the signal from the fully open switch 18 to determine that the key switch has changed from ON to OFF.

This has the advantage of improving the accuracy of fully open state determination.

In step 72, the i-th temperature coefficient α1 is calculated. α
, after all, are the temperature and opening signals (T Ic
, θTHIC). And α is the temperature coefficient for correction during the (i+1)th operation. At step 74, α1 is stored in place of α(a-,) that has been stored so far.

This method is a method for determining the temperature coefficient using the temperature and opening degree when the valve is fully opened, and is a simple and excellent method for determining the temperature coefficient for correction. Note that the temperature coefficient described here is the temperature coefficient when a permanent magnet, a yoke, and a Hall IC are combined.

Therefore, the temperature characteristics that appear as a result of canceling out the temperature characteristics of the permanent magnet constituted by the rare earth magnet and the silicon-based Hall IC are corrected by the temperature coefficient determined as described above.

In addition, in Fig. 5 (A), vT and Vo are read after determining that the ignition key 〇FF-) is turned on, but conversely, the temperature coefficient is calculated by reading the values immediately before the key 0FF-) is turned on. You may. An example thereof is shown in FIG. 5(C). The other steps are the same and have been omitted.

Further, in the above embodiment, the temperature coefficient was determined at the fully closed position of the valve shaft, but the temperature coefficient can be similarly determined at the fully open position. An example of this case is shown in FIG.

This is shown with the suffix S indicating the fully open position in the portion corresponding to FIG. 5(A). Each step was then marked with a dash to indicate its correspondence.

In step 54', the valve stem is fully opened just before the key switch 0FF-) is turned on, and V T3 and V os at that time are read. In some cases, a full-open switch may be provided corresponding to the full-open switch shown in FIG. 1 to more accurately determine the full-open position. Following steps 52', 56' to 6
Since the process corresponding to step 4' in FIG. 5(A) is omitted, a supplementary explanation will be provided regarding the process corresponding to step 68 in FIG. 5(B).

To read the voltages corresponding to V T t c and V ot c, after turning the key from ON to OFF, the valve opening degree is operated to the fully open position and the value at that time is read. Then, αts is calculated by the process corresponding to step 72, and (i+1
) is used as the temperature coefficient for the second calculation. The other processes corresponding to steps 70 and 74 are the same and will not be described here.

α1 mentioned above. When both αts are calculated, the average value of αi and αts may be used as the average temperature coefficient in the temperature change range.

Furthermore, in consideration of the non-linearity of the temperature coefficient, the following method may be used to obtain temperature coefficients in a plurality of temperature ranges, store them, and use the corresponding temperature coefficients. An example of the relationship between temperature coefficient α and T is shown in Table 1. Vr
The temperature T converted from is the predetermined temperature 'rl, T
2 (however, T t < T2) is T 1 < T <
When at T2, select the fully closed temperature coefficient αl or the fully open temperature coefficient α1s.

When T z < T < Ta (each predetermined value for T z < Ta), α■ or αI
ts is selected. T I"a is a predetermined value, and T1 to T4 may be set at equal intervals or may be set at unequal intervals. For the range that shows nonlinearity, α changes too much. In the range in which the temperature is not increased, the temperature range may be set broadly.An example of a flow diagram when the relationships shown in Table 1 shown below are stored in the storage device 82 is shown in FIG.

In step 8o of table 1, it is determined in which region T is located, and the corresponding temperature coefficient of table 1 is read out from the storage device 82, and step 8
In step 4, temperature compensation is performed using the selected α. Also α
may be fully open or the average value when fully open. According to this method, it is possible to perform compensation that also takes into account the nonlinearity of the temperature coefficient.

In addition, in Fig. 8, α is stored in advance in a table format in the storage device, but α is calculated according to T by approximating the function and storing the function form (α=f(r)). It may be a method. In this case, if the approximation of the function is good, highly accurate compensation is possible.

Further, the valve opening degree is frequently used in a relatively low opening degree range. Therefore, in addition to the temperature coefficient based on the fully open state described in Figures 5 (A) and (B), by determining the temperature coefficient in the low opening range and using that temperature coefficient, even more accurate temperature compensation is possible. becomes. This can be determined, for example, as follows.

Figure 9 shows the valve stem opening and the output voltage V of the Hall IC.

It shows the relationship between It is often done that the detection sensitivity is made different between the low opening range from the fully open position to θT and the subsequent range. This is hole I of yoke 9 in Figure 2.
This can be achieved by changing the shape of the C facing surface. In other words, the shape from h to h2 may be changed.

The first method of calculating the temperature coefficient is the temperature coefficient at the fully open position (
For example, the method according to FIGS. 5(A) and (B)) and θTl(
This method calculates the temperature coefficient at position 4 and uses the average value to perform temperature compensation.

At the temperature Two, the opening degree is fixed to θTH4 and Vo is read in. Then, when the temperature is set to T'tao, V o la o is read and αL is calculated.

α = (θT) 14″θT old δo) / (Ttao−
T2O). Furthermore, θTH1e θTH2,
A similar method is used to calculate each OTH3 and α1. Find α2°α3, αl, α1~8. If low opening degree compensation is performed using the average value of αL, more accurate characteristics can be obtained.

The second method is αl between full throttle and oTH4.

α1. α2. α8. This is a method in which αL is switched and used. For example, V as shown in the second example below.

In this method, the corresponding temperature coefficient is selected and used in accordance with the magnitude of the valve shaft opening degree θTH determined from the above.

Table 2 Table 2 may be stored in advance and α may be selected using the method shown in FIG. In this case, the selection of θTH is determined using the temperature-compensated value.

Also, in this example, the method is to select α for θTH, but α1. If the maximum and minimum deviations among αl−8 and α are smaller than predetermined values, any value of α in Table 2 may be used. Further, in that case, it may be decided to use a specific α. For example, a method such as α1 may be determined and the selection is made according to Table 2 only when the maximum and minimum deviations are large.

The compensation method described above can be called a soft compensation, and can sufficiently cope with variations in the permanent magnet and the hole (c). Furthermore, with the method shown in Figures 5 (A) and (B) or Figure 7, which calculates the temperature coefficient each time, it is possible to sufficiently compensate for changes over time, etc. The shaft opening can be detected.

In addition, more optimal temperature compensation can be achieved by combining the method of using the temperature corresponding to the opening degree shown in Table 2 with the method shown in Figures 5 (A), (B) or Figure 7. It is possible to do so.

Furthermore, in the above embodiments, an example has been described in which the magnetic circuit and the Hall element are combined so that the temperature coefficients of the magnetic circuit and the Hall element have different polarities so that changes in characteristics due to temperature are canceled out. However, the method of calculating the temperature coefficient and performing temperature compensation using the calculated temperature coefficient only requires a smaller amount of compensation when combined as described above. Therefore, the temperature compensation method described in the present invention is not limited to the combinations thereof.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a throttle sensor that is highly accurate even with respect to temperature changes, element variations, and changes over time.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the configuration of the present invention, Figure 2 is a schematic diagram of the sensor structure, Figures 3 (A) to (E) are examples of partial characteristics and terminal diagrams of the Hall IC, and Figure 4 is the temperature characteristic. Qualitative illustrations, Figures 5 (A) and (B). (C) and Figure 7 are flow diagrams of temperature coefficient calculation examples, Figure 6 is an explanatory diagram of compensation components, Figure 8 is an example of the selection flow in Table 1, and Figure 9 is temperature in the low opening range. Examples of explanations of coefficient calculations are shown below. 8...Permanent magnet, 9...Yoke, 1o...Hall IC. House 2 Zu Akira 1 draw A) Period 3rd base (F3) Prisoner mo 3 diagram (C)
State also Figure 3 (D) Certain 3 Taku Kamita S Figure (A) Figure S (C) 6th Ti T Tame'1 Figure 8 Figure q

Claims (14)

[Claims] 1. In a throttle sensor that uses a Hall element to detect changes in magnetic flux corresponding to throttle opening, the temperature coefficient of the permanent magnet that is the magnetic flux generation source and the Hall element that detects the change in magnetic flux have opposite polarities. A throttle sensor characterized by a combination of 2. The throttle sensor according to claim 1, characterized in that a rare earth permanent magnet is used as the permanent magnet, and a silicon-based Hall IC is used as the Hall element. 3. In a throttle sensor that uses a Hall element to detect changes in magnetic flux corresponding to throttle opening, temperature compensation is performed during the i-th starting operation using the temperature coefficient calculated during the (i-1)th starting operation. Features a throttle sensor temperature compensation method. 4. In claim 3, the temperature coefficient at the i-th starting operation is determined by the following step (a).
) to (c), (a) Calculate the valve stem opening from the Hall IC temperature and Hall output voltage when it is detected that the ignition key switch changes from OFF to ON, (b) The above Calculate the valve stem opening from the Hall IC temperature and Hall output voltage when it is detected that the ignition key switch has changed from ON to OFF during operation in step (a), and (c) step (a). Hole I calculated in (b)
The temperature coefficient is calculated from the values of the C temperature and the valve stem opening, and is set as the temperature coefficient at the i-th starting operation, and the (i+
1) A temperature compensation method for a throttle sensor, characterized in that it is used as a compensation temperature coefficient during the first starting operation. 5. Step (a) according to claim 4
, the ignition key switch is turned from OFF to ON.
A temperature compensation method for a throttle sensor, characterized in that a valve shaft opening degree is calculated from a Hall IC temperature immediately before changing to a Hall IC temperature and a Hall output voltage. 6. A temperature compensation method for a throttle sensor according to claim 4 or 5, characterized in that the Hall IC temperature is calculated from the IC voltage representing the Hall IC internal temperature. 7. In claim 4, the temperature coefficient at the i-th starting operation is determined by the following (a) to (c).
(a) Just before the ignition key switch changes from OFF to ON, the valve stem opening is fully opened, and the valve stem opening is calculated from the Hall IC temperature and Hall output voltage at that time; (b) Immediately after the ignition key switch is changed from ON to OFF in the operation in step (a) above, the valve shaft opening is fully opened, and the valve shaft opening is calculated from the Hall IC temperature and Hall output voltage at that time, (c) Hole I calculated in steps (a) and (b) above
A temperature compensation method for a throttle sensor, characterized in that a temperature coefficient is calculated from the values of the C temperature and the valve shaft opening, and is used as the temperature coefficient during the (i+1)th starting operation. 8. In the throttle sensor, which uses a Hall element to detect changes in magnetic flux corresponding to the throttle opening, the engine's operating temperature range is divided into multiple regions, and the temperature coefficient for each temperature range is calculated and stored in advance to determine the temperature during operation. A temperature compensation method for a throttle sensor, characterized in that a corresponding temperature coefficient is read out from the stored value in accordance with the stored value, and temperature compensation for each temperature range is performed using the read out temperature coefficient. 9. 9. A temperature compensation method for a throttle sensor, wherein the temperature coefficient according to claim 8 is a temperature coefficient when the valve shaft opening is fully closed or a temperature coefficient when the valve shaft opening is fully opened. 10. A temperature compensation method for a throttle sensor according to claim 8, wherein the temperature coefficient is an average value of temperature coefficients when the valve shaft is fully open and when the valve shaft is fully closed. 11. In a throttle sensor that uses a Hall element to detect changes in magnetic flux corresponding to throttle opening, the average value is calculated and stored in advance from the temperature coefficients at a fully closed position and a predetermined low opening position, and the temperature coefficient is stored in advance at the fully closed position. and the predetermined low opening position, temperature compensation is performed using the stored temperature coefficient. 12. In a throttle sensor that uses a Hall element to detect changes in magnetic flux corresponding to throttle opening, a fully closed position and a predetermined low opening position are divided into a plurality of opening positions, and temperature coefficients in the plurality of opening ranges are calculated. is calculated and stored in advance, and in the low opening range, the pre-stored temperature coefficient is read out according to the valve shaft opening, and temperature compensation is performed sequentially using the read out temperature coefficient. temperature compensation method. 13. As described in claim 11, the temperature coefficient in the low opening range is stored in advance as a function of the valve stem opening, and temperature compensation is performed using the temperature coefficient calculated according to the function. Temperature compensation method for throttle sensor. 14. In the claim 8, temperature coefficients for a plurality of predetermined temperature ranges are stored as a function approximation, and temperature compensation is performed using a temperature coefficient calculated from the stored functions according to the temperature. A temperature compensation method for a throttle sensor characterized by performing the following steps.