GB2304902A

GB2304902A - Detecting engine accessory torque

Info

Publication number: GB2304902A
Application number: GB9617972A
Authority: GB
Inventors: Hirohito Matsui; Mitsuo Inagaki; Yoshiaki Takano; Mikio Matsuda; Hisanaga Matsuoka
Original assignee: Nippon Soken Inc; NipponDenso Co Ltd
Current assignee: Denso Corp; Soken Inc
Priority date: 1995-08-28
Filing date: 1996-08-28
Publication date: 1997-03-26
Also published as: DE19634619A1; GB9617972D0; JPH09257613A; JP3648857B2

Description

0 0 2304902 ACCESSORY TORQUE DETECTOR The present invention relates to

accessory torque detectors.

Recently, in an internal combustion engine mounted in a vehicle such as an automobile, accessories such as the compressor of an air conditioner of the vehicle, the hydraulic pump of a power steering unit of the vehicle, an alternator and the cooling fan for a vehicle radiator are simultaneously driven by a crankshaft pulley provided on the crankshaft of the internal combustion engine via a chain or belt.

If the total load torque (hereinafter referred to as "torque") of two accessories varies depending upon the operating z 0 0 1 0 states of the accessories, as in the case of the air conditioner compressor and the power steering hydraulic pump, and can be precisely measured, the rotational speed when an engine idles can be controlled with higher precision and can be reduced and the vehicle automatic transmission can be controlled more finely.

A method of measuring the torque of each accessory separately can be used to measure the total torque of, for example, the air conditioner compressor and the power steering hydraulic pump, in a system in which multiple accessories are simultaneously driven by a belt; however, since the number of mounted accessories has increased in recent times, the cost of torque detection is increased because of the resultant increase in the complexity of torque detection.

Various respective aspects of the invention are defined in the appended claims. Embodiments of the present invention can provide a simple and inexpensive accessory torque detector for detecting the total torque of multiple accessories driven by a belt.

Embodiments of the invention make use of the discovery that the rotational speed of a drive shaft pulley and the rotational speed of an idle pulley or an accessory pulley are closely related to the total torque of accessories in a system in which multiple accessories are simultaneously driven via a belt.

To explain this relationship for exemplary embodiments of the invention, FIG. 1 shows a belt transmission including two pulleys, a driving pulley 100 and a 0 ' a driven (accessory) pulley 200. When the driving pulley 100 is driven, the distribution of the tension of a belt 300 is shown by the width of the belt in FIG. 1. The tension on the tense side located in the lower part in FIG. 1 is T1 and the tension on the loose side is T2. The tension in a portion corresponding to an angle 6 - 0, that is, a portion from C to B in FIG. 1 of a portion in which the driven pulley 200 is in contact with the belt 300 is the same as the tension T2 on the loose side.

In other words, motive power is transmitted in a portion from A to C in FIG. 1 and the driven pulley 200 is thereby turned. In a portion from C to B in FIG. 1, the belt 300 and the driven pulley 200 are rotated together.

When transmitted horsepower (hereinafter called accessory torque) is increased, a portion from C to B in FIG. 1 disappears, motive power is transmitted in a state in which the belt 300 and the driven pulley 200 are fully in contact. That is, when accessory torque is increased, the tension T1 is increased and the tension T2 is reduced, and the difference between T1 and T2 is increased as accessory torque is increased.

Slip occurs between the driven pulley 200 and the belt 300, and this slip can be divided into a normal slip and an elastic slip. That is, a slip when 0 > 6, accessory torque is increased and motive power is transmitted in a state in which the belt 300 and the driven pulley 200 are fully in contact is called a normal slip. i f e: o, the driven pulley 200 is slid in a portion from A to C in which tension varies, and this slip is called an elastic slip.

0 1 0 Normally, such a belt transmission can be operated in a state in which elastic slip occurs as long as no excessive accessory torque is created. That is, when accessory torque is increased, the difference between Tl and T2 is increased and a Jag of the driven pulley 200 from the belt 300 is increased.

In the meantime, similarly, the tension of the driven pulley 100 in a portion corresponding to an angle e. - 0', that is, a portion from G to F in FIG. 1, is the same as the tension Tl on the tense side. In other words, motive power is transmitted in a portion from G to H and in this portion, the belt 300 is behind the driven pulley 100. In a portion from F to G in FIG. 1 the belt 300 and the driven pulley 100 are rotated together.

In such a belt transmission, the above accessory torque (Trq) is expressed by the following Equation (l):

Trg = Rle(T1 - T2) .. (1) where Rl is the radius of the driving pulley. If K is a constant showing the elasticity of the belt 300, el is the distortion of the belt on the tense side and ú2 is the distortion of the belt on the loose side, Tl and T2 are expressed by the following Equations (2) and (3).

Tl = Kel T2 = K.E2 (2) (3) when a belt transmission shown in FIG. 1 is steadily rotated (in a state of elastic slip), the following relational expression comes into effect according to the law of conservation of mass.

and thus:

Mass which passes through a point D in unit time = mass which passes through a point E in unit time.

If the linear density of the belt when no tension is applied to the belt 300 is po, the length of the belt 300 on the tense side is extended by a factor of (1 + cl), and the linear density is pO/(1 + cl) when the tension Tl is applied.

Similarly, when the tension T2 is applied, the length of the belt 300 on the loose side is extended by a factor of (1 + cl), and the linear density is pO/(1 + e2).

Therefore.. the above expressions are related by Equation (4):

-PO VI= -PO V2 1 +cl 1 +e2 V1 1 +cl V2 1 +e2 .. (4) .. (5) That is, the speed of the belt 300 is increased by the quantity of extension and Equation (6) can be obtained:

V1 -1 = el -e2 =el-e2 72- l+el .. (6) assuming that el (( 1.

Substituting Equations (2) through (6) into Equation (1), accessory torque is as follows:

Trq = Rlo(T1 T2) = RloK(E1 e2) =Rl V' - I) V2 .. (7) and it can be seen that accessory torque Trq and the velocity ratio V1/V2 of the belt are linear.

The above expression may be further transformed as follows:

Tra=Rl V2 - .. (8) However, if the term (V1/V2 - 1) in the expression is transformed, the portion is (V1 - V2)/V2 and the difference in velocity V1 - V2 is magnified as accessory torque is increased and a lag of the driven pulley 200 from the belt 300 is increased as described above.

6 - Therefore, (V1 - V2)/V2 can be regarded as slip ratio in an elastic slip caused between the driven pulley 200 and the belt 300 and as a result, accessory torque Trq is considered to be linear with respect to slip ratio. Similarly, it can be also regarded as the slip ratio between the driving pulley 100 and the belt 300. Therefore, if velocity V1 and V2 are obtained, a correlation between velocity and accessgry torque Trq is known and the process will be described below.

If an idle pulley is provided on the loose side of the belt 300, the idle pulley is rotated together with the loose side of the belt 300 if its accessory torque is regarded as zero and therefore, if the rotational speed wl of this idle pulley is obtained, V1 (R3owl if the radius of the idle pulley is R3) can be obtained. As an idle pulley is rotated together with the tense side of the belt 300 if it is provided on the tense side of the belt 300, V2 (R4-w2 if the radius of the idle pulley is R4) can be obtained if the rotational speed w2 of the idle pulley is obtained. According to this results, if an idle pulley is provided, V1 and V2 can be readily obtained.

Further, the above (V1 - V2)/V2 can be regarded as slip ratio between the driving pulley 100 and the driven pulley 200 in the above state of an elastic slip. That is, V1 is the rotational speed of the driving pulley 100, V2 is the rotational speed of the driven pulley 200 in a state of an elastic slip as described above, and a correlation exists between the rotational speed of the driving pulley 100 and the driven pulley 200 and accessory torque.

7 0 0 0 Further, the above rotational speeds V1 and V2 are respectively expressed by Equations (9) and (10) if the rotational speed of the driving pulley 100 is Wl and that of the driven pulley 200 is W2:

V1 = R1OW1 V2 = R2 0 W2 and accessory torque is expressed by Equation (11).

7, R1 ( W1 _1 12- W2)] ..

.. (11) . (9) (10) Therefore, as Rl and R2 are fixed values and accessory torque Trq is linear to rotational speed ratio (corresponding to the difference in rotational speed) between the driving pulley 100 and the driven pulley 200.

In a belt transmission shown in FIG. 2 in which multiple accessories 101 104 and an idle pulley 105 are driven via a belt 300 by a driver (the driving pulley 100), if the rotational speed WO of the driving pulley (for example, the crankshaft pulley of an engine) 100 and that W5 of the idle pulley 105 are obtained as shown in FIG. 3, the total torque of all accessories can be obtained. The torque of a desired accessory can be detected by detecting rotational speed WO and the rotational speed (any of W1 to W4) of one of accessories 101 to 104. Further, for example,. the total torque of the 8 - 0 1 ' 0 accessories 2 and 3 can be detected by detecting the rotational speed of the accessories I and 3.

Tl to T5 in FIG. 2 denote the tension of the belt 300 between the accessories where Tl > T2 > T3 > T4 > T5, and if the torque of the idle pulley 105 is assumed to be zero, tension is unchanged before and after the idle pulley.

Using these properties, the above-described object is achieved according to embodiments of the present invention by proving a torque detection system in which the total torque of multiple accessories is detected based on a rotational speed detected by a first rotational speed detector for detecting the rotational speed of the drive shaft pulley and a second rotational speed detector for detecting the rotational speed of an idle pulley. If three or more accessories are provided, the total torque of two or more accessories can be determined with high precision depending upon a position at which an idle pulley is located. Since only a rotational speed detecting device is provided, an accessory torque detector for detecting the torque of each accessory is not necessary, and accessory torque can be detected easily and inexpensively.

The above-described object is achieved according to further embodiments of the present invention by proving a torque detection system using a map showing the relationship between rotational speed ratio or the difference in rotational speed and total torque, where the magnitude of the torque of one accessory is substantially fixed and known and multiple accessories are intermittently operated and total torque before and after 0 to 0 3 0 -1 ' 0, intermittent operation is predetermined. This system includes a correction unit for correcting a map based on a rotational speed ratio before operation and that after operation is provided. Thus, even if the constant of elasticity of a belt varies or the engine is operated under an abnormal environmental condition, the precision of detecting total torque can be enhanced.

Preferably, idle or accessory pulleys whose rotational speeds are detected by a second rotational speed detector are arranged adjacent to and ahead of the direction of movement of the belt.

Tle invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which:

FIGS. 1 and 2 show the operating principles of embodiments of the present invention; FIG. 3 is a graph of rotational speed ratios versus accessory torque; C FIG. 4 is a cross-sectional view of an idle pulley according to a first embodiment of the present invention; FIG. 5 is a bottom view of the idle pulley of FIG. 4; FIG. 6 is a block diagram of a belt transmission - 0 900 according to the first embodiment; FIGS. 7 - 9 are graphs of the relationship between rotational speed ratio and the total torque of accessories in the first embodiment; FIGS. 10 - 12 are flowcharts of a procedure for calculating the total torque of accessories according to the f irst embodiment and second and fourth embodiments, respectively; FIG. 13 is a partial cross-sectional view of an automatic tensioner in a fifth embodiment according to the present invention; FIG. 14 is a longitudinal cross-sectional view of the automatic tensioner shown in FIG. 13 taken along line XIV-XIV; FIG. 15 is a diagram of the relationship between the tension of a belt and the axle load of an automatic tensioner pulley in the fifth embodiment; FIG. 16 is a graph of the relationship between the change of the tension of the belt and the load torque of accessories in the fifth embodiment; FIG. 17 is a front view of an automatic tensioner according to a sixth embodiment of the present invention; FIG. 18 is a cross-sectional view of the automatic tensioner in the sixth embodiment taken along line XVIII-XVIII in FIG. 17; FIG. 19 is a perspective view showing a position detecting sensor according to the sixth embodiment; FIG. 20 is a graph of the relationship between the change of the turning angle of an arm and the load torque of 1 1 - 4 0 - 0 accessories in the sixth embodiment; FIG. 21 is a cross-sectional view of an idle pulley according to a seventh embodiment of the present invention; FIG. 22 shows a principle of operation of the seventh embodiment; FIG. 23 shows an eighth embodiment; and FIGS. 24 - 28 show variations on the above- illustrated embodiments.

As shown in FIG. 6, in an internal combustion engine 1 mounted in an automobile or other vehicle, multiple belt pulleys as a belt transmission for driving a variety of accessories such as a pulley 2 for a compressor of an air conditioner, a pulley 3 for a hydraulic pump of a power steering unit, a pulley 4 for an alternator and a pulley 5 for a cooling fan of a radiator are simultaneously driven by a crankshaft pulley 6 (generally a drive shaft pulley) via a belt 7.

In such a belt transmission, an idle pulley 8 may be used to wind one belt 7 around many pulleys as shown in FIG. 6, and an automatic tensioner 9 for automatically adjusting such that the tension of the belt 7 is fixed may also be provided on the loose side of the belt 7 together with one idle pulley 10.

As shown in FIGS. 4 and 5, the automatic tensioner 9 constitutes a part of an accessory torque detector.

0 a 0 A large number of teeth 12 made of a magnetic material are provided at equal intervals on the circular inner surface 11 of the idle pulley 10 of the automatic tensioner 9.

Practically, the entire idle pulley 10 is made of a material such as magnetic iron or steel and a large number of teeth 12 are machined in the shape of an internal gear on the circular inner surface 11. Alteratively, if the idle pulley 10 is molded by a method such as casting, it is desirable that the teeth 12 on the circular inner surface 11 are also simultaneously molded using the same cast.

The arm 13 of the automatic tensioner 9 is supported so that its base 14 can be turned by a shaft (not shown) through a limited range of movement. This arm 13 is pressed in the turning direction in which the belt 7 is strained by a spring (not shown) or a pressing device such as a hydraulic cylinder.

A bearing 16 is provided on a shaft 15 integrated with the free end of the arm 13, and the idle pulley 10 is supported by this bearing 16 so that the pulley 10 can be rotated.

An engine speed sensor such as an electromagnetic pickup 18 is attached to a projection 17 formed on the arm 13 and the detecting end the detecting end of the electrom agnetic pickup 18 protrudes toward the teeth 12 but is separated therefrom by a predetermined interval.

The electromagnetic pickup 18 may be a well-known device such as a permanent magnet or a core made of a magnetic material around which a coil is wound and which is magnetically 0 '00 % 1 0 0 connected to the permanent magnet, both ends of the coil being directly connected to the fixed terminal of an external device (not shown) via flexible lead wires 19 and 20. Alternatively, one end of the coil is connected to the arm 13 and the other end is taken out via a flexible lead wire and connected to the fixed terminal of an external device (again, not shown).

Since the range in which the arm 13 is moved is limited to a small angle, an output signal can be taken out outside merely by directly connecting the end of a flexible lead wire to the fixed terminal of an object without the need to use a sliding mechanism such as a slip ring.

Referring again to FIG. 6, the total torque detector 400 calculates the total torque based on the rotational speed Wl of a crankshaft 21 (the crankshaft pulley 6) and the rotational speed W2 of the idle pulley 10 measured by the electromagnetic pickup 18 and controls the speed of the engine 1 when it idles and at other appropriate times by outputting the calculated total torque to an engine controller 500.

A rotational speed sensor 50 is provided on the crankshaft pulley 6 as shown in FIG. 6. However, the rotational speed sensor 50 detects the rotational speed of the crankshaft 21 or a shaft which is driven at a fixed rotational ratio to the crankshaft 21 such as a cam shaft (not shown) even if the shaft is not the crankshaft 21 itself.

Normally, the engine speed Wl of an internal combustion engine or the rotational speed of an object rotating at a fixed ratio to the engine is used as a factor for controlling the - 14 0 0 operation of an engine and a large number of vehicles are provided with a rotational speed sensor on their crankshaft 21. Therefore, even if a rotational speed sensor is installed for another purpose, a signal outputted by it may be utilized for the object of the present invention. Otherwise, in an internal combustion engine which is not provided with a device for detecting the rotational speed Wl, a rotational speed detecting device as shown in FIGS. 4 and 5 may be provided on the crankshaft pulley 6.

As shown in FIG. 6, the pulleys 2, 3, 5, 8 and 10 are simultaneously rotated via the crankshaft pulley 6 and a belt 7 by rotating the crankshaft 21. The total torque operating on the crankshaft 21 to drive these pulleys and attached accessories not only varies depending upon the rotational speed of the crankshaft 21 itself but also because some. accessories as the compressor 2 are intermittently operated and therefore the total torque normally varies while the internal combustion engine 1 is operated.

If the varying total torque can be always detected precisely in real time, the operation of the internal combustion engine 1 (for example, the engine speed when it idles) can be controlled to a precise degree.

In this embodiment, the total torque is detected with high precision based on the rotational speed Wl detected by the rotational speed sensor 50 of the crankshaft 21 and the rotational speed W2 of the idle pulley 10 which is detected by the electromagnetic pickup 18 provided on the automatic tensioner is - 1 0 4 0 9 so that the automatic tensioner is adjacent to the crankshaft pulley 6 ahead of the direction of movement of the belt 7 as described above in connection with FIGS. 1 - 3.

The principle upon which the rotational speed W2 is detected by the electromagnetic pickup 18 will be described briefly. When the idle pulley 10 of the automatic tensioner is rotated via the belt 7 from the crankshaft pulley 6, the magnetic flux density of the permanent magnet forming the electromagnetic pickup 18 fixed on the arm 13 varies due to the movement of the magnetic teeth 12 of the pulley 10. As a result, pulse current with peaks at approximately even intervals is generated in the coil of the electromagnetic pickup 18. This pulse current is directly taken out to the fixed terminal of an external device via the lead wires 19 and 20 as an output signal corresponding to the rotational speed W2 and inputted to the total torque detector 400 provided with an arithmetic unit.

In the total torque detector 400, the rotational speed W2 of the idle pulley 10 of the automatic tensioner 9 is detected by counting the number of peaks of pulse current from the electromagnetic pickup 18 per unit time. Since this rotational speed W2 is reduced by an elastic slip between the crankshaft pulley 6 and the belt 7 if the crankshaft pulley 6 and the idle pulley 10 have the same diameter, the quantity of slippage of the idle pulley 10 to the crankshaft pulley 6 can be known from the ratio Wl/W2 of the rotational speeds W1 and W2. In this case, the idle pulley 10 is regarded as no load and slip between the belt 7 and the idle pulley 10 is ignored.

0 1 a 1 '0 0 - '00 The rotational speed ratio W11W2 showing the quantity of slippage (slip ratio) between the crankshaft pulley 6 and the idle pulley 10 is calculated based on detected rotational speeds W1 and W2 and the magnitude of the total torque operating on the crankshaft 21 at the time can be derived using FIG. 7.

Since this slip ratio is based on the ratio of speeds on the loose side and the tense side of the belt 7 as described above, that is, the rotational speed ratio of the crankshaft pulley 6 and the idle pulley 10, naturally the ratio R of respective radiuses of the crankshaft pulley 6 and the idle pulley 10 must be taken into account. That is, if W1 is the rotational speed of the crankshaft 21 and the crankshaft pulley 6; W2 is the rotational speed of the idle pulley 10 of the automatic tensioner 9; the slip ratio of the belt 7, i.e., the idle pulley 10, to the crankshaft pulley 6; S is the ratio of the radii of the pulleys (where the diameter of the idle pulley 10 is R and that of the crankshaft pulley 6 is Rl so that R = R1/R2); and the slip ratio S between the crankshaft pulley 6 and the belt 7, i.e., the idle pulley 10, is given by Equation (12), S= W' -R-WE - W' -R W2 u .. (12) then, since the ratio of the radii in Equation (12) is constant, the slip ratio S depends upon the value of rotational speed ratio W1/W2 when the crankshaft pulley 6 and the idle pulley 10 have the same radius.

0 0 1 0 1 Therefore, a graph as in FIG. 7 showing the relationship between the slip ratio and the total torque of accessories for obtaining the value of the total torque based on slip ratio S has the abcissa showing the rotational speed ratio W1/W2 and a slanted, positive slope straight line showing the proportional relationship between the vertical and horizontal axes.

As apparent from Equation (12), the value of W1 - R-W2 AW is equivalent to the decrease of the rotational speed of the idle pulley 10 caused by elastic slip between the crankshaft pulley 6 and the belt 7 which is calculated based on the rotational speed W2 of the idle pulley 10 as the reference rotational speed; however, the rotational speed W1 of the crankshaft pulley 6, the rotational speed of which seldom varies, may be used as the reference rotational speed.

If slip ratio in this case is S', the decrease of the slip ratio can be defined by Equation (13):

Sl W1-R-W2 =1-R W2 W1 W1 .. (13) FIG. 8 is a graph having its abcissa showing rotational speed ratio W1/W2 based on the rotational speed W1 of the crankshaft pulley 6 and the ordinate showing the total torque of accessories and showing measured values. FIG. 8 corresponds to FIG. 7 described above and shows the case where the crankshaft pulley 6 and the idle pulley 10 have the same diameter. Since - 18 0 - 0 the rotational speed W1 of the crankshaft pulley 6 is adopted as the reference in this case, a straight line in the graph showing the relationship between the rotational speed ratio and the total torque of accessories has a different slope than the line in FIG.

7.

Since some of the pulleys described below are not intermittently operated as is the air conditioner compressor pulley, but are instead continuously driven by a larger torque than a fixed value, such as the cooling fan pulley 5, it is impossible that the value of rotational speed ratio W1/W2 or W2/W1 at that time is one.

Accordingly, in FIGS. 7 and 8, the basic value of the torque of accessories which always operate and the quantity of minute change of rotational speed ratio corresponding to the value are omitted to simplify the graphs showing the relationship between rotational speed ratio and the total torque of accessories. That is, the ordinate shows the sum of the value of the changing torque of intermittently operated accessories and the value of the changing torque of always driven accessories and rotational speed ratio shown by the abcissa starts from unity.

As described above, as slip ratio S' is defined by the above expression (13) even if the crankshaft pulley 6 and the idle pulley 10 have different radii, the slip ratio can be calculated using the rotational speed ratio and the ratio R of the radii of the pulleys, and the value of the total torque of accessories operating at that time can be precisely detected by applying the value to the graph of measured values showing the - 19 relationship between slip ratio and the total torque of accessories shown in FIG. 9.

The graph showing the relationship between slip ratio and the total torque of accessories in FIG. 9 can be also obtained from the relationship between slip ratio S and the total torque of accessories with the rotational speed W2 of the idle pulley 10 as the reference.

If such a graph of measured values showing the relationship between slip ratio and the total torque of accessories in FIG. 9 is set beforehand as a map in, for example the engine controller 400 provided with an arithmetic unit, rotational speeds W1 and W2 can be always detected automatically by the above detecting means and the magnitude of the total torque of accessories can be automatically detected with high precision in real time based on the detected value.

In the above description, the magnitude of the total torque of accessories is set based on slip ratio, however, naturally, the total torque of accessories can be also directly calculated based on rotational speed ratio.

FIG. 10 shows a processing procedure summarizing the above procedure. In Step 201, a rotation sensor generates a pulse signal corresponding to the rotational speed of the crankshaft pulley 6, and in Step 202, a rotation sensor generates a pulse signal corresponding to the rotational speed of the idle pulley 10. In Steps 203 and 204, the rotational speeds per unit time W1 and W2 of the crankshaft pulley 6 and the idle pulley 10 are respectively determined. Finally, in Step 205, load torque 0 is is calculated based on the ratio W2/W1.

In the above-described f irst embodiment, the total torque of all accessories is calculated. However, according to a second preferred embodiment of the present invention, the torque of a desired accessory can be determined by detecting the rotational speed of the crankshaft pulley 6 and that of the desired pulley as described above.

That is, when a belt transmission shown in FIG. 6 is applied to FIG. 2, the accessory 1 is equivalent to the cooling fan pulley 5, the accessory 2 to the compressor pulley 2, the accessory 3 to the hydraulic pump pulley 3, the accessory 4 to the alternator pulley 4, and the accessory 5 to the idle pulley 10. The idle pulley 8, for which no load torque is considered to exist, is ignored.

Thus, if the rotational speed of, for example, the crankshaft pulley 6 and the compressor pulley 2 shown in FIG. 6 are detected, the total torque of the compressor pulley 2 and the cooling fan pulley 5 can be calculated based on the relationship shown in FIG. 3.

Since the torque of the cooling fan pulley 2 can be considered to be approximately fixed, the torque of the compressor pulley 2 can be calculated by subtracting the torque of the compressor pulley 2 from the above total torque.

FIG. 11 summarizes the processing procedure in this case. In Steps 301 and 302, the rotational speeds W1 and W2 of the crankshaft pulley 6 andcompressor pulley W2 are measured. in Step 303, the rotational speed ratio H is calculated.

0 '00 is Finally, in Step 304, the total torque Trq is calculated from the rotational speed ratio H.

If the torque of the compressor pulley 2 is calculated as described above, a rotational speed sensor must be provided on the compressor pulley 2; however, the sensor may already be provided on the compressor pulley 2 depending upon the type of vehicle.

That is, since some types of vehicles are provided with a lock sensor which determines whether the compressor is locked or not based on the rotational speed of the compressor pulley 2 to detect whether the compressor of an air conditioner is locked or not, the torque of the accessory of the compressor can be calculated if this lock sensor is utilized without providing a dedicated rotational speed sensor.

In the above first and second embodiments, the total torque of all accessories is calculated in a belt transmission in which multiple accessory pulleys are rotated by the belt 7, however, according to a third embodiment of the present invention, the total torque of two or more desired accessories can be calculated by respectively detecting the rotational speed of, for example, an accessory and an idle pulley.

That is, when FIG. 6 is applied to FIG. 2 as in the above-described second embodiment, the correlation between the rotational speed ratio of the compressor pulley 2 and the cooling fan pulley 5 shown in FIG. 6 and the torque of the compressor pulley 2 can be determined from the relationship shown in FIG. 3 if the above-described rotational speed ratio is known.

0 0 Therefore, if a graph as shown in FIG. 7 is set based on this correlation, the torque of the accessory of the compressor can be calculated.

Similarly, if the rotational speed ratio of the compressor pulley 2 and the alternator pulley 4 shown in FIG. 6 is known, the correlation between this rotational speed ratio and the total torque of two accessories including the hydraulic pump pulley and the alternator pulley can be determined. Therefore, if a graph as shown in FIG. 7 is set based on this correlation, the total torque of two accessories including the hydraulic pump pulley and the alternator pulley 4 can be calculated with high precision.

Similarly, if the rotational speed ratio of the idle pulley 8 and the alternator pulley 4 shown in FIG. 6 is known, the correlation between this rotational speed ratio and the total torque of two accessories including the hydraulic pump pulley and the alternator pulley 4 can be determined. Therefore, if a graph such as the one shown in FIG. 7 is set based on this correlation, the total torque of two accessories including the hydraulic pump pulley and the alternator pulley 4 can be also calculated with high precision.

As described above, if the rotational speed ratio of two pulleys except the crankshaft pulley 6 is known, the torque of a desired accessory can be calculated. To detect the rotational speed of two pulleys, the electromagnetic pickup 18 shown in FIGS. 4 and 5 may be used. The above sensor for detecting whether the compressor is locked or not may be used for 0 this purpose.

In the above-described first through third embodiments, the magnitude of the torque of accessories operating on the crankshaft pulley 6 can be detected precisely in real time; however, when the belt deteriorates due to environmental conditions or the effective radius of a pulley varies, the slopes of the graphs shown in FIGS. 7 - 9 showing values measured under predetermined condition are unsuitable. When, for example, the belt 7 is worn and the radius ratio R of pulleys substantially varies due to use for a long time, a graph showing the relationship between rotation speed ratio and the total torque of accessories may be unsuitable.

Accordingly, in this embodiment, a correction device for keeping the precision of detecting the total torque high by correcting the graphs shown FIGS. 7 to 9 which is set in the total torque detector 400 or the engine controller 500 for calculation at a predetermined time is provided to solve such problems.

For example, a hot-wire heater for defrosting on the glass face of a rear window is provided in many cars. While this hot-wire heater is energized by the alternator coupled to the alternator pulley 4, it functions as a fixed current sink for the alternator. Therefore, while the hot-wire heater is energized, a fixed increase is included in the torque required for driving the alternator.

The rotational speed ratio when the hot-wire heater is energized, i.e., when a hot-wire switch is turned on, and when 6 1 0 is 0 it is not energized, i.e., when the hot-wire switch is turned off, are detected, the relationship between predetermined total torque and the rotational speed ratio is plotted in a graph showing the relationship between rotational speed ratio and the total torque of accessories as shown in FIG. 7, and the straight line shown in FIG. 7 is replaced with a straight line formed by connecting these two points.

The predetermined total torque when the hot-wire switch is turned on and of f means measured total torque Tb and Ta respectively when the hot-wire switch is turned on and off under conditions that it has been only a short time since a belt 300 has been used, for example, after an engine idles, a compressor is turned off, i.e., no load torque is applied to the compressor pulley 2 and load torque applied to the hydraulic pump pulley 3 is fixed (for example, the vehicle steering wheel is in a center position so that the vehicle is moving straight). Since the current output of the alternator varies when the hot-wire switch is turned on and then turned off, these total torques Tb and Ta depend upon the current output of the alternator.

More specifically, the correction device whose operation is shown in the flowchart of FIG. 12 first detects the respective rotational speeds Wla and W2a of the crankshaft pulley 6 and the idle pulley 10 under the above conditions when the hotwire switch is turned off as shown in Step 101 and calculates the rotational speed ratio Wra = W2a/W1a thereof. It determines the coordinates (Ta and Wra at a point A at which the value of the total torque of accessories is the reference value in a graph 1 D 0 0 0 showing the relationship between rotational speed ratio and the total torque of accessories as shown in FIG. 7.

Next, Step 102 is executed shortly after the processing shown Step 101 is finished, the respective rotational speeds W1b and W2b of the crankshaft pulley 6 and the idle pulley 10 are detected when the hot-wire switch is turned on, and the rotational speed ratio Wrb = W2b/W1b thereof is calculated. The coordinates Tb and Wrb at a point B at which the value of the total torque of accessories is the reference value in a graph showing the relationship between rotational speed ratio and the total torque of accessories as shown in FIG. 7 are determined.

Since the points A and B in the graph showing the relationship between rotational speed ratio and the total torque of accessories are determined as described above, the map set beforehand in the total torque detector 400 or the engine controller 500 is replaced with a new graph formed by connecting the points A and B in Step 103. When initial maps shown in FIGS. 7 - 9 are set, a similar procedure may be also performed.

Step 102 must be performed a few seconds after Step 101 is finished so that the torque of other accessories does not fluctuate during the graph calculation process.

In a fifth preferred embodiment of the present invention, the total torque of accessories such as the alternator and a power steering pump (described later) is detected based on the change in state of the automatic tensioner pulley 11 differently from the above calculation of the total torque based on rotational speed, and the result of this detection is sent to - 26 0 ' 1k 0 0 the engine controller 500. In the engine controller 500, the horsepower of the engine is appropriately changed based on the fluctuation of the total torque to keep the rotational speed of the engine fixed.

FIG. 13 is a perspective drawing showing the automatic tensioner 9 and FIG. 14 is a corresponding cross-sectional view thereof. The peripheral surface of the flat idle pulley 10 is in contact with the back surface of the V-belt 7 and supported by a shaft 15 provided at the end of the arm 13 so the pulley can be rotated. A cylindrical thick boss ill is formed in the center of the body of the pulley 10 and this boss 111 is coupled to the shaft 15 via a bearing 16 so it can be rotated.

The arm 13 is supported by a supporting shaft 115, the end of which is attached to the side face of an engine block so that the arm 13 can be rotated, and the end of the arm 13 is pressed in the direction shown by the thick arrow in FIG. 13 by the force of coil springs 113 provided around the supporting shaft 115 so that approximately fixed tension is always applied to the belt 7 when it is on the pulley 10.

As shown in FIG. 14, the base end of the arm 13 is an umbrella-type holder 141 which is attached to the supporting shaft 115 on the side face of the engine E so that it can be rotated, and this holder 141 is pressed by the coil springs 113 provided around the holder so that the holder can be rotated around the supporting shaft 115. The pulley 10 is supported by the shaft 15 provided at the end of the above arm 13 via the bearing 16, and a strain gauges 73 is disposed at multiple is locations of the peripheral face of the base of this shaft 15.

The tension of the belt 7 is kept approximately fixed by the above pulley 10 of the automatic tensioner 9; however, when the load torque of any of the other accessories fluctuates, the tension of the belt 7 also varies a little. Since the change in tension appears as the axle load of the shaft 15 as shown in FIG. 15, the total torque of all accessories can be calculated based on the axle load detected by the strain gauge 73 as shown in FIG. 16. Therefore, sudden change in the rotational speed of the engine can be prevented by changing the horsepower of the engine based on the total torque.

FIG. 17 is a front view showing a automatic tensioner 9 according to a sixth embodiment of the present invention, and FIG. 18 is a crosssectional view thereof. The holder 141 at the base end of the arm 13 is coupled to the supporting shaft 115 of the base body 116 fixed on the side face of the engine so that the holder can be rotated, and the pulley 10 is supported by the shaft 15 formed at the end of the above arm 13 so that the pulley 10 can be rotated. The arm 13 is pressed by the coil springs 113 provided around the supporting shaft 115 so that the arm can be rotated counterclockwise in FIG. 17, and in this state, the V belt 7 is suspended from the left side of the drawing.

A light emitting diode (LED) 74 is disposed near the base body 116 on the face opposite the side on which the pulley 10 is located at the end of the arm 13, and a position detecting sensor 75 extending in a straight line horizontally in FIG. 17 is disposed on a supporting wall 161 at the lower edge of the 0 - 1P 0 base body 116 opposite the LED 74. The position detecting sensor 75 has slits 751 disposed at fixed intervals on a front face thereof as shown in FIG. 19, and a photodiode array 752 is disposed at positions corresponding to these slits 751.

When the tension of the belt 7 is increased as the total torque of accessori es is increased, the arm 13 is rotated counterclockwise in FIG. 17 by the force of the coil springs 113, and the end of the arm 13 and the pulley 10 provided there are moved to the right in FIG. 19 together with the change of rotational angle. This movement is detected by the photodiode array 752 for receiving light emitted from the light emitting diode 74, and the total load torque of all accessories according to the change of the rotational angle of the arm 13 (that is, the change of the position of the pulley 10) can be calculated based on the proportional relationship shown in FIG. 20.

In the above-described first through fourth embodiments, the electromagnetic pickup 18 is used as a rotational speed sensor; however, an optical element shown in FIGS. 21 and 22 may be used instead in a seventh preferred embodiment of the present invention. In FIG. 21, reference numeral 22 denotes a light emitting element such as an LED, and reference numeral 23 denotes a light receiving element such as a photodiode. The LED 22 and the photodiode 23 are attached to the arm 13 at the edge of the idle pulley 10 of the automatic tensioner 9 as in the first and second embodiments so that they oppose one another. Therefore, a projection 24 for supporting both the LED 22 and the photodiode 23 may be integrated with the 1 1 ' - 10 arm 13.

The LED 22 and photodiode 23 are positioned so that a turning slit 25 formed circularly at the edge of the idle pulley 10 lies between the LED 22 and the photodiode 23. The turning slit 25 is made by providing fine openings 27 transmitting light in the radial direction on a circular plate 26 as shown in FIG. 22 at an equal intervals when the openings are viewed from the direction of the outer periphery and may be directly formed on the skirt 28 of the idle pulley 10. The turning slit 25 may be formed apart from the idle pulley 10, and it may be attached to the skirt 28. A fixed slit 29 which is a plate is used as a mask and fixed on the light receiving face of the LED 23, and some openings 30 are formed on the fixed slit 29.

Thus, when the idle pulley 10 is driven and rotated by the belt 7, the turning slit 25 is also rotated and when the optical axis of the LED 22 corresponds to an opening 27 formed on the circular plate 26 of the turning slit 25 and an opening 30 formed on the fixed slit 29, light emitted from the LED 22 reaches the photodiode 23 and a pulse signal is output from the photodiode 23.

Therefore, this signal shows the rotational speed W2 of the idle pulley 10 as in the first and second embodiments and is processed together with the rotational speed W1 measured separately from the crankshaft 21. The magnitude of the total torque operating on the crankshaft 21 can be determined from a graph showing the relationship between the rotational speed ratio and the total torque of accessories as shown in FIG. 7.

- 30 is In the above-described embodiments, multiple accessories such as the compressor pulley 2, the hydraulic pump pulley 3, the alternator pulley 4 and the cooling fan pulley 5 are driven by one belt 7; however, according to an eighth preferred embodiment of the present invention, a belt transmission may be used as shown in FIG. 23.

That is, the belt transmission shown in FIG. 23 includes a crankshaft pulley 6, a compressor pulley 2 and a hydraulic pump pulley 3, and the automatic tensioner 9 and idle pulley 10 are not provided. if the rotational speed of the crankshaft pulley 6 and that of the hydraulic pump pulley 3 are detected in such a belt transmission, the total torque of two accessories can be calculated as in the above-described first and second embodiments. If the rotational speed of the crankshaft pulley 6 and that of the compressor pulley 2 are detected, the torque of the compressor (not shown) can be calculated.

The positions of the compressor pulley 2- and the hydraulic pump pulley 3 shown in FIG. 23 may be exchanged or replaced with any other appropriate accessory.

In the above-described first to third embodiments, a large number of teeth 12 are formed as internal gears on the circular inner surface 11 of the idle pulley 10; however, only one tooth need be formed as shown in FIGS. 24 and 25. In this case, the machining of the tooth 12 is simplified.

Slits 116 may be formed along the peripheral direction of the idle pulley 10 by casting as shown in FIGS. 26 - 28 to function as teeth 12. In this case, the electromagnetic pickup 1 c & 18 is disposed opposite to these slits.

In the above-described first embodiment, the rotational speed of the idle pulley 10 and the crankshaft pulley 6 are detected and the total torque of accessories is calculated based on these speeds; however, the total torque of accessories may be calculated by detecting the rotational speed of the crankshaft pulley 6 and the alternator pulley 4 shown in FIG. 6 and setting a graph showing the relationship between rotational speed and the total torque of accessories as shown in FIG. 7 based on these two rotational speeds. In this case, for a detection device for detecting the rotational speed of the alternator pulley 4, the electromagnetic pickup 18 and the teeth 12 shown in FIGS. 4 and 5 may be used or the above LED 22 and the photodiode 23 may be used.

In the above-described first to fourth embodiments, the total torque is calculated based on rotational speed ratio; however, the total torque may be naturally calculated based on the difference between rotational speeds.

Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the present invention as defined by the appended claims.

P ( 1 % CLAEMS An accessory torque detector for a belt transmission on an engine, said accessory torque detector comprising: a drive shaft pulley f or being rotated by said engine; an idle pulley mounted on said engine and rotatable thereon; a group of additional pulleys including a plurality of accessory pulleys for driving a plurality of accessories of said engine via a belt disposed around said drive shaft pulley and said idle pulley; first rotational speed detecting means for detecting a rotational speed of said drive shaft pulley and generating a signal representative thereof; second rotational speed detecting means for detecting a rotational speed of said idle pulley and generating a signal representative thereof; and a total torque detector for calculating a total torque of said plurality of accessories based on said signals.

2. The detector of claim 1, wherein: said group of additional pulleys further includes an idle pulley disposed on said engine and rotatable thereon; and said second rotational speed detecting means is for detecting a rotational speed of said idle pulley and generating a signal representative thereof.

1-:0 3. The detector of claim 2, wherein: said idle pulley is disposed ahead of said drive shaft pulley in a direction of travel of said belt.

4. The detector of claim 1, wherein: said second rotational speed detecting means is for detecting a rotational speed of one of said plurality of accessory pulleys and generating a signal representative thereof.

5. The detector of claim 4, wherein: said one of said plurality of accessory pulleys is disposed ahead of said drive shaft pulley in a direction of travel of said belt.

6. The detector of claim 4, wherein said idle pulley is part of an automatic tensioner for keeping tension of said belt fixed.

7. The detector of claim 1, wherein said total torque detector is for detecting said total torque of said plurality of accessories according to a slip ratio of said belt based on said signals.

8. The detector of claim 1, wherein said total torque detector is for detecting said total torque of said plurality of accessories based on a difference in rotational speed of said drive shaft pulley and said one of said additional pulleys.

9. The detector of claim 8, wherein: a torque of a particular one of said plurality of additional accessories is substantially fixed and known, said particular one of said plurality of accessories being intermittently operated; total torque before and after intermittent operation is set to predetermined values; and said total torque detector includes a map indicative of a relationship between said difference in rotational speed and said total torque.

10. The detector of claim 1, wherein said total torque detector is for detecting said total torque of said plurality of accessories based on a ratio of rotational speed of said drive shaft pulley and said one of said additional pulleys.

11. The detector of claim 10, wherein: a torque of a particular one of said plurality of accessories is substantially fixed and known, said particular one of said plurality of accessories being intermittently operated; total torque before and after intermittent operation is set to predetermined values; and said total torque detector includes a map indicative of a relationship between said rotational speed ratio and said total torque, and correction means for correcting said map based on said rotational speed ratio before and after operation.

- 0 -: 1 12. An accessory torque detector for a belt transmission on an engine, said accessory torque detector comprising: a drive shaft pulley for being rotated by said engine; at least three accessory pulleys for driving a plurality of accessories of said engine via a belt disposed around said drive shaft pulley; first rotational speed detecting means for detecting a rotational speed of one of said plurality of accessory pulleys and generating a signal representative thereof; and second rotational speed detecting means for detecting a rotational speed of a different one of said plurality of accessory pulleys and generating a signal representative thereof; and a total torque detector for calculating a total torque of said plurality of accessories based on said signals.

13. An accessory torque detector for a belt transmission on an engine, said accessory torque detector comprising: a drive shaft pulley for being rotated by said engine; an idle pulley; a plurality of accessory pulleys for driving a plurality of accessories of said engine via a belt disposed around said drive shaft pulley and said idle pulley; load detecting means for detecting an axle load of a supporting shaft of said idle pulley; and a total torque detector for calculating a total torque of said plurality of accessories based on a change of said axle load of said supporting shaft of said idle pulley.

14. An accessory torque detector for a belt transmission on an engine, said accessory torque detector comprising: a drive shaft pulley for being rotated by said engine; an automatic tensioner for keeping a tension of said belt fixed, said automatic tensioner including an idle pulley mounted at an end of an arm pressed by a spring member to bias said arm in a rotational direction; a plurality of accessory pulleys for driving a plurality of accessories of said engine via a belt disposed around said drive shaft pulley and said idle pulley; position detecting means for detecting a p osition of said idle pulley of said automatic tensioner; and a total torque detector for detecting a total torque of said plurality of accessories based on a positional change of said idle pulley of said automatic tensioner.

15. An accessory torque detector substantially as hereinbefore described with reference to the accompanying drawings.