JPS6246733B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electromagnetic clutch for transmitting power,
In particular, it relates to electromagnetic clutches with low power consumption. A conventional electromagnetic clutch engages an input side rotary body and a load side rotary body in order to transmit power and power to drive a load side rotary body connected to a driven body.
Electric power was required to maintain this state. Figure 1 is a sectional view of the main part of a conventional electromagnetic clutch, Figure 2 is a right side view of Figure 1, and A-B in Figure 2.
The cross section is shown in Figure 1. When looking at the electromagnetic clutch functionally, it consists of an input rotating body 6 driven via a V-belt 14, an excitation section consisting of a coil 4 and a coil case 5 attached to the fixed body 1 of the electromagnetic clutch, and a covered part. It is composed of three elements: a rotating shaft 2 connected to a driving body and an output rotating section consisting of a load-side rotating body 3. The input side rotating body 6 is an annular body rotatably supported by the main body 1 via a bearing 9 and can rotate independently of other elements. A cylindrically wound coil 4 is housed in a soft iron coil case 5 and inserted into the recess of the input side rotating body 6.
It is also fixed to the main body 1. In addition, the rotating shaft 2
is connected to the main body 1 via a rotating bearing part not shown in the figure.
A load-side rotating body 3, which is installed at the center of the vehicle and has a movable piece 7 attached to its right end, is fixed by a key 10. That is, the key 10 fixed to the rotary shaft 2 is inserted into the key groove of the load-side rotary body 3, and the nut 12 is screwed onto the screw provided at the right end of the rotary shaft 2, and the load-side rotary body 3 is tightened and integrated. It is said that Leaf springs 13 fixed by rivets 11b are attached to the load-side rotating body 3 at three locations.
An annular movable piece 7 is attached to the tip of the leaf spring 13 with a rivet 11a. An example of the electrical characteristics and operation of the conventional electromagnetic clutch constructed in this manner will be described below. The average diameter D of the coil is 86.8 mm, and the number of turns N of the coil is
12V, 3A, into a coil such that is 350 turns
If a current of 36W flows, the number of excitation amperes
NI will be 1050 ampere turns, and the resistance value of coil 4 will be R = E / I will be 4Ω. Also, since the length of the conducting wire is L=DπN, it is 95.5 m, and its weight is about 382 gr. If the diameter of the conductor of coil 4 is 0.75mm, the total resistance of this conductor is 4Ω, so 1km
It becomes 41.8Ω per hit. That is, it is approximately 40Ω/Km. The cross-sectional area of the space that accommodates coil 4 is 14 mm x 12 mm.
Considering the coil exterior, insulation treatment layer, etc.
Assuming that 350 turns are wound in 15 stages and 24 rows, (0.75×
15) × (0.75 × 24) = 11.25 × 17 (mm ² ), but if you look at the margin around the coil 4, it becomes 12 × 18 mm ² . In other words, 18mm is the coil width and 12mm is the coil thickness, so the diameter of coil 4 is 86.8±6mm and the width is 18mm.
It becomes a circular coil. In FIG. 1, if the average length of the magnetic path 8 consisting of the coil case 5, the movable piece 7, and the input rotating body 6 is l ₂ = 35 mm and l ₂ = 24 mm, the average magnetic path shown by the broken line is The length l is l=2l ₁ +2l ₂ =2(35+24)=118(mm). This length l determines the efficiency of the magnetizing force. Let the current density of the conductor be d, and the cross-sectional area of the conductor be s
mm ² and the diameter of the conductor wire is 0.75 mm, then d=I/s=4I/π ² =4×3/0.75 ² π=6.8A/mm ² , and the heat generation amount H of the coil 4 is When the resistance is R ohm and the coil rating is 1 hour, and the time t is expressed in sec, H = 1/jI ² Rt = 1/4.1852 x 3 ² x 4 x 60 ² = 30966 (cal). . j is the work equivalent of heat. According to an example of an induction motor, which has a large heat dissipation effect due to rotation like this electromagnetic clutch, the current density is generally 4 to 5 A/mm ² (continuous rating), but the conventional electromagnetic clutch has a d is
6.8A/mm ² , and it is difficult to further reduce the wire diameter, increase the current density, and reduce the dimensions of the coil 4. That is, the coil 4 of the conventional electromagnetic coil
had the disadvantages of generating a large amount of heat and being large in size. FIG. 3 is a diagram showing the relationship between the magnetizing force H and the magnetic flux density B of the coil case shown in FIG. 1, and the hysteresis phenomenon is greatly expressed. Generally, when the magnetic flux required for the coil 4 to generate the required electromagnetic attraction force is φ, the magnetic permeability is μ, the length of the magnetic path is l, and the cross-sectional area of the magnetic path is S, then the magnetizing force H =4πNI/l, so it is expressed as φ=BS=μHS=μ4πNI/l. Therefore, in order to make the coil 4 smaller and lighter, it is necessary to reduce S and increase the magnetic flux density B.
It will be a good thing if we increase it. However, since the cross-sectional area S is selected so that the magnetic permeability μ is as large as possible, the cross-sectional area S tends to become large and it is difficult to reduce the magnetic material. That is, even when considering this relationship, it has the disadvantage that it is difficult to downsize the electromagnetic coil. Figure 4 is a diagram showing the relationship between the magnetizing force H, magnetic permeability μ, and magnetic flux density B of the coil case in Figure 3, where the magnetic permeability μ is the magnetizing force H
is maximum at a relatively low point and then decreases. On the other hand, the magnetic flux density B increases rapidly where the magnetizing force H is relatively low, but the rate of increase rapidly decreases beyond that range. The purpose of the present invention is to provide an electromagnetic clutch that is small, lightweight, and consumes little energy. a movable piece that is attached to the body and can be electromagnetically and detachably engaged with the input side rotating body; and a movable piece that is fixed to the body and inserted into the recess of the input side rotating body and housed therein. A coil case that forms a magnetic path with the input-side rotary body and the movable piece by excitation of a coil to engage the input-side rotary body and the movable piece, and a control device for controlling the current flowing through the coil. In the electromagnetic clutch for rotating or stopping the load-side rotating body, the coil case is made of a magnetic material with a large residual magnetism, and the control device for controlling the current flowing through the coil is configured to magnetize and demagnetize the magnetic material. A capacitor that stores and supplies charge,
In the process of discharging the charge accumulated in the capacitor, the coil case is magnetized by the current flowing through the coil, and the movable piece is engaged with the input rotating body, and the residual magnetism of the coil case causes the movable piece to engage with the input rotating body. During the charging process in which charge is accumulated in the capacitor, the residual magnetism in the coil case is canceled by a current flowing through the coil in the opposite direction to that in the discharging process, thereby causing the movable piece and the input side to rotate. The device is characterized by having a circuit for breaking the engagement state with the body. FIG. 5 is a sectional view of an electromagnetic clutch according to an embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. In this case, the coil 4 is housed in a coil case 15 made of a permanent magnetic material such as carbon steel, and is inserted into a recess of the input rotating body 6. Therefore, after the coil 4 is energized to form the magnetic path 8 and the movable piece 7 is attracted to the input rotating body 6 and driven,
Since the residual magnetism of the coil case 15 can maintain the attracted state, power is required only during excitation, and power can be saved. Assuming that the time required for the movable piece 7 to attract and engage with the input rotating body 6 is 0.1 sec, the magnetization of the coil case 15 is completed during this time. If the length of the conductor wire of the coil 4 is shortened to 1/10 of the conventional case, the coil 4 will be made smaller, and the current I at this time will be 3 x 10 = 30 A, but the input power amount will be 360 W x 0.1 sec = 36Wsec, which requires only a small amount of electricity. Therefore, coil 4
Even if it is made small, there is no risk of overheating and burnout. Now, assuming that the required electromagnetic attraction force is the same as in Figure 1, the number of turns of coil 4 is N', and the current is I',
Since NI=N'I', N'=NI/I'. Therefore, N' = 350 x 3/30 = 35 turns, and the length l' of the conductor of coil 4 is l' = 86.8 x 3.14 x 35 x 10 ^-3 = 9.54 (m), that is, 9.54 m. It is now 1/10 the length of the previous model and weighs approximately 67gr. The diameter of the conductor wire of the coil 11 is 1 mm, and the conventional
If it is larger than 0.75mm, you can wind it in 12 stages and 3 rows.
There are 36 turns, and the cross-sectional area of the coil 4 at this time is 12×1×1×3=12×3=36 (mm ² ). Furthermore, the resistance R' of the coil 4 has a wire diameter of 1
In the case of mm, the resistance value for 1 km is 21Ω, so R′=21×9.544/1000=0.2(Ω). The amount of heat generated by the coil 4 is as follows: H=1/jI′ ² R′t=1/4.1852×30 ² ×0.2×0.1=4.3 (cal) That is, the amount of heat generated is only 0.01% of the conventional value. Note that when the resistance value of coil 4 is 0.2Ω, the current I' is 60A when the power supply voltage is 12V, but the total of the relay contact resistance of the control circuit, the conductor resistance of the circuit, etc.
If we estimate it to be 0.2Ω, the total resistance seen from the power supply will be 0.4Ω, so the required current will be 30A. The average magnetic path length l' is given by the cross-sectional area of coil 4 being 12 x 3 mm ²
Therefore, the axial length is reduced by 18-3=15 (mm). As a result, l′=2(l′ ₁ −15)+2l′ ₂ =2(35
−15)+2×24=88 (mm), and the magnetic path length l′ is 30
mm shortened. As a result of the above, as shown in Fig. 5, the coil 4
Since the width of the coil case 15 is shortened by 15 mm, the coil case 15 is also shortened by 15 mm. Therefore, the length of the electromagnetic clutch in the axial direction is also reduced by 15 mm, making it possible to significantly reduce the size. Note that the portion of the coil case 15 that is attached to the main body 1 may be separated from the surrounding portion of the coil 4. Furthermore, instead of carbon steel, tungsten steel, chrome steel, cobalt steel, nickel aluminum steel, etc. can also be used as the permanent magnet material. FIG. 6 is an electrical circuit diagram for controlling the electromagnetic clutch of FIG. 5. When the contact piece 17 of the switch 16 is in contact with the terminal a, the current of the power source 18 flows through the current limiting resistor 20, the terminal a, the contact piece 17, the capacitor 19, and the coil 4;
The battery is charged to a voltage of Q=C×V, and a charge of Q=C×V is accumulated. Next, the contact piece 17 of the switch 16
When inputted to the terminal b side, a circuit passing through the terminal b and the coil 4 is formed, and a discharge current flows in the direction of the broken line arrow, and the charge Q accumulated in the capacitor 19 disappears. During this discharge process, the coil case 15 of the electromagnetic clutch is magnetized, and after the magnetic flux φ reaches φ _nax , it decreases over time. At this time, the mover 7 attracts and engages the input-side rotating body 6 to rotate the load-side rotating body 3 and the rotating shaft 2, and even after the magnetizing force disappears, the residual magnetism brings them into close contact and continues power transmission. . To cancel the power transmission, switch the switch 16 shown in Fig. 6 and put the contact piece 17 on the terminal a side.
Charging current flows in the direction shown by the solid line with an arrow,
A magnetizing force in the opposite direction is generated in the coil case 15 to erase the residual magnetism, and the movable piece 7 is separated from the input-side rotating body 6 by the spring force of the leaf spring 13, so that power transmission stops. Note that the current limiting resistor 20 is a resistor that sets the optimum excitation current for providing a reverse magnetic force that eliminates the coercive force od that maintains the residual magnetism oc shown in FIG. Fig. 7 is a diagram showing changes over time in the current and magnetic flux of the control circuit in Fig. 6. The broken line 21 is the case where the discharge current flows in the direction of the broken line with the arrow in Fig. The parallel flat part is the residual magnetic flux φ _r
It shows. Moreover, the solid line 22 is the case where the current flows in the direction of the solid line with the arrow in FIG.
While charging the capacitor 19, a current in the opposite direction flows through the coil 4, canceling the residual magnetic flux _φr , separating the movable piece 7, and stopping the rotation of the rotating shaft 2. Table 1 shows a comparison between the electromagnetic clutch of this embodiment described above and a conventional electromagnetic coil.

[Table] The electromagnetic clutch of this embodiment is configured such that a small coil is housed in a coil case made of a permanent magnet material and inserted into a recess of the input rotating body, and when the electromagnetic clutch is put into operation. By discharging the charge accumulated in the capacitor of the control electric circuit, the movable piece attached to the output side rotating body is engaged with the input side rotating body, and when the state is to be separated, the switch of the control electric circuit is turned on. By switching and passing a current in the opposite direction through the coil that cancels the magnetic force of the coil case, it is possible to obtain a small, power-saving electromagnetic clutch that only consumes current during switching. FIG. 8 is another electrical circuit diagram for controlling the electromagnetic clutch shown in FIG. 5, in which the same parts as in FIG. 6 are denoted by the same reference numerals. When the contact piece 17 of the switch 16 is switched to the b terminal, the charge accumulated in the capacitor 19 is discharged from the positive terminal of the capacitor 19 through the terminal b and the current relay 24, and the current relay 24 is temporarily activated by this discharge current. It operates normally and returns when the discharge is completed. This current relay 24 has normally open contacts 28, 29 and a normally closed contact 30, and when the current relay 24 is activated, the normally open contacts 2
8, 29 are closed and the normally closed contact 30 is opened. On the other hand, the current relay 23 has a normally closed contact 25 and normally open contacts 26 and 27.
When activated, the normally closed contact 25 is opened and the normally open contacts 26 and 27 are closed. This current relay 23 is activated when the contact piece 17 comes into contact with the terminal a and the current from the power source 18 is stored in the capacitor 19, and the capacitor 19 stores charge and returns to its original state after a predetermined period of time has elapsed. Now, when the contact piece 17 is connected to terminal b and the current relay 24 is activated, the normally open contacts 28 and 29 are closed and the normally closed contact 30 is opened. 4. Pass an upward current through the normally open contact 29 to the coil 4 as shown by the broken line. This current is the current I _b shown in FIG.
5 is magnetized to generate a magnetic flux φ _nax , which causes the input side rotating body 6 and the movable piece 7 to engage with each other. Further, after time t _b , the current relay 24 returns to its original state, but the engaged state of the movable piece 7 is maintained by the residual magnetic flux φ _r . Next, when the contact piece 17 is connected to the terminal a as shown in FIG. 8, the capacitor 19 is charged and the current relay 23 is operated to open the normally closed contact 25 and close the normally open contacts 26 and 27. Therefore, the current of the power source 18 is limited by the current limiting resistor 20, and the normally open contact 26 and the normally closed contact 3 are limited by the current limiting resistor 20.
0, a downward current shown by a solid line is applied to the coil 4 through the normally open contact 27. This reverse current I _a shown in FIG. 9 cancels the residual magnetism φ _r and the current relay 23 returns to its reset state after a time _{t a} . Note that the current I _a is a current sufficient to cancel out the residual magnetism φ _r and is an amount that does not reverse excite the coil case 15 , and this is set by the current limiting resistor 20 . In addition, the normally closed contacts 25 and 30 are used as an interlock to give priority to the command of the current relay which has been commanded to operate first.
It has the effect of preventing short circuit accidents. FIG. 9 is a diagram showing changes over time in the current and magnetic flux of the control circuit shown in FIG. 8, and the explanation thereof is given together with the explanation of the operation of the circuit shown in FIG. The electromagnetic clutch control circuit of this embodiment uses a pair of current relays to control the current flowing through the coil, so it clearly distinguishes between the power transmission state and the release state of the electromagnetic clutch, and prevents short-circuit accidents of the power supply. The effect is that it can be prevented. The control circuit of the electromagnetic clutch shown in FIGS. 6 and 8 above includes the charging/discharging current of the charge accumulated in the capacitor 19, the inductance of the control circuit, the capacitance of the capacitor 19, and the resistance value R of the current limiting resistor 20.
It is possible to magnetize and demagnetize the electromagnetic clutch by simply using short-term electrical energy that flows according to a time constant determined by the above equation, making it possible to transmit and release power with a small amount of electric power. The electromagnetic clutch of the present invention is small and lightweight, and
This has the effect of significantly reducing power consumption.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main part of a conventional electromagnetic clutch, Fig. 2 is a right side view of Fig. 1, and Fig. 3 is a diagram showing the relationship between magnetizing force and magnetic flux density of the coil case of Fig. 1. 4 is a diagram showing the relationship between the magnetizing force, magnetic permeability, and magnetic flux density of the coil case in FIG. 1, FIG. 5 is a sectional view of an electromagnetic clutch that is an embodiment of the present invention, and FIG. Figure 5 is an electrical circuit diagram for controlling the electromagnetic clutch, Figure 7 is a diagram showing changes over time in the current and magnetic flux of the control circuit in Figure 6, and Figure 8 is a diagram showing other electrical circuits for controlling the electromagnetic clutch in Figure 5. The circuit diagram, FIG. 9, is a diagram showing changes over time in the current and magnetic flux of the control circuit shown in FIG. 8. 1... Body, 2... Rotating shaft, 3... Load side rotating body, 4... Coil, 5, 15... Coil case,
6... Input side rotating body, 7... Movable piece, 8... Magnetic path, 9... Bearing, 10... Key, 11...
Rivet, 13... leaf spring, 14... V-belt,
16... Switch, 17... Contact piece, 18... Power source, 19... Capacitor, 20... Current limiting resistor, 23, 24... Current relay, 25, 30...
Normally closed contacts, 26, 27, 28, 29... normally open contacts.

Claims (1)

[Claims] 1. An input-side rotating body rotated by a drive source, and a load-side rotating body installed at the center of rotation of this input-side rotating body, and electromagnetically and detachably engaged with the input-side rotating body. A magnetic path is formed with the input side rotor and the movable piece by excitation of a coil that is inserted into a recess of the input side rotor and housed therein while being fixed to the main body. The electromagnetic clutch has a coil case for engaging the input-side rotating body and the movable piece, and a control device for controlling a current flowing through the coil, and rotates or stops the load-side rotating body, wherein the coil case is configured to rotate or stop the load-side rotating body. A control device for controlling the current flowing through the coil is made of a magnetic material with a large residual magnetism, and a capacitor that stores and supplies electric charge for magnetizing and demagnetizing the magnetic material, and a capacitor that stores and supplies electric charge for magnetizing and demagnetizing the magnetic material, and in the process of discharging the electric charge accumulated in this capacitor, the electric current flowing through the coil The coil case is magnetized by the current flowing through the coil case, the movable piece is engaged with the input rotating body, and the engaged state is maintained by the residual magnetism of the coil case, so that electric charge is accumulated in the capacitor. a circuit that cancels the residual magnetism of the coil case and releases the engagement state between the movable piece and the input-side rotating body by a current flowing through the coil in a direction opposite to that in the discharging process during the charging process. An electromagnetic clutch characterized by: