JP3335376B2 - Starter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starter used for starting an internal combustion engine, and more particularly to a starter driven by a power supply voltage higher than 12 V which is usually used.

[0002]

2. Description of the Related Art As is well known, a general starter attracts a movable body such as a plunger by exciting an electromagnetic coil, and the movement of the movable body is transmitted to a sliding body such as a pinion gear via a transmission means such as a shift lever. The pinion gear is pushed into and meshed with a ring gear of the engine to perform a shift operation, and at the time of this meshing, the motor is driven to start the engine.

A typical example of a conventional starter is as follows.
For example, there is one disclosed in Japanese Utility Model Publication No. 60-87142. This consists of an armature rotatably supported in the housing, a field pole arranged around the armature, a commutator fixed coaxially to the armature, and a brush pressed slidably against the commutator. A magnet having a motor portion, an electromagnetic coil having a fixed core, a plunger as a movable body attracted to the fixed core when the electromagnetic coil is energized, and a spring for biasing the movable body in a direction opposite to the attraction force. A shift portion as a transmission means connected to the plunger and a shift portion having a pinion sleeve and a pinion gear forming a sliding body slidably mounted on the output shaft of the armature; I have. When the electromagnetic coil is excited (switched on) and demagnetized (switched off), the plunger reciprocates by the attraction force of the fixed iron core and the urging force of the spring, and this reciprocation is transmitted to the pinion sleeve via the shift lever. The pinion sleeve slides on the output shaft of the armature of the motor according to the reciprocating motion of the plunger, and the pinion gear attached to the pinion sleeve is pushed into and meshes with a ring gear provided in the engine. Thus, the output (rotation) of the armature is transmitted to the engine, and the engine is started. Generally, a DC motor is used as a motor of such a starter, and many motors have a brush for supplying a current to a commutator as described above.

A brush mounted on the conventional starter motor as described above includes a sliding contact body formed by firing a mixed powder of graphite powder and copper powder, and a brush which is embedded in and fixed to the sliding contact body for electrical connection. And a lead wire called a pigtail. The brush is slidably pressed by the commutator, and a leaf spring is used as the pressing means.

On the other hand, in the electric pump device disclosed in Japanese Patent Application Laid-Open No. 60-156242, the fluid pressure of a pump driven by a DC motor is guided to the brush side to control the pressure applied to the commutator of the brush. The brush pressure is changed according to the magnitude of the current flowing through the brush.

[0006]

In recent years, attention has been paid to the significant emission control of CO2 as a measure against environmental problems of automobiles. Therefore, it is important to improve fuel efficiency by reducing the weight and efficiency of the vehicle itself and the weight of the electrical components. Among them, as one method of reducing the weight of a vehicle, increasing the voltage of an on-vehicle power supply has been proposed to reduce the weight of a wire harness and improve workability. In general, increasing the voltage of an in-vehicle power supply means that power is represented by the product of voltage and current.If the power consumption of a car is the same, increasing the voltage can reduce the current by that amount. As a result, it is possible to use a thin electric wire to be wired to the vehicle, and to achieve weight reduction.

[0007] Even in a starter typified by Japanese Utility Model Application Laid-Open No. 60-87142, a high voltage system whose power supply voltage is usually higher than 12 V is required from the above viewpoint. Here, it is necessary to set the number of turns of the armature winding to four times by increasing the power supply voltage, which is conventionally 12 V, to, for example, 48 V. For this reason, the reactance voltage that affects the rectification performance is greatly increased, and the rectification performance may be degraded due to a spark or the like flying between the brush and the commutator. As a countermeasure, it is necessary to sufficiently study the rectifying performance in advance and select a material for the brush that can cope with the rectifying performance. Usually, a material having a higher specific resistance than the conventional one is used. Since a material having a high specific resistance generally has a high friction coefficient, the use of a material having a high specific resistance as a brush material results in a large friction loss of the brush. Therefore, an electric loss of the brush (contact voltage effect loss) is added. The total loss on the outer periphery of the commutator is increased. In general, in a starter, the total loss on the commutator circumference, i.e., the brush loss, accounts for about 40% of the total motor loss, and this brush loss causes a significant reduction in motor efficiency. There is a problem that the shaft torque is not generated until the load exceeds the% load. Further, there is a drawback that an increase in the brush loss causes an increase in the temperature of the commutator, which may lead to a thermal destruction of the commutator.

In the electric pump device disclosed in Japanese Patent Application Laid-Open No. Sho 60-156242, the brush pressure is changed according to the magnitude of the current flowing through the brush, so that the friction loss due to the brush is reduced. However, this is only applied at the start or end of operation of the DC motor, and as the present invention is directed to,
The power supply voltage itself is not actively increased by using a material having a high specific resistance as the material of the brush, and the motor efficiency is remarkably reduced due to the increase in the frictional loss during the steady operation as described above.

An object of the present invention is to provide a starter driven by a power supply voltage higher than 12 V which is generally used for reducing the weight of a vehicle body, even if a material having a higher specific resistance than a conventional material is used as a brush material. It is an object of the present invention to provide a starter in which the friction losses do not increase and thus the losses on the commutator circumference do not increase.

[0010]

According to the present invention, there is provided an armature and a field pole, a brush and a commutator for supplying a current to the armature, and a brush for sliding the brush to the commutator. A starter for starting the internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V which is normally used, wherein the brush is provided when the power supply voltage is 12 V. Used
The specific resistance and coefficient of friction are higher than that of the material used, and the specific resistance is 4
2,000 to 8000 μΩ · cm, and is made of a material having a specific resistance P2 (kg / c
m2) is set to be lower than when the power supply voltage is 12 V and to satisfy 0.45 ≦ P2 ≦ 1.6.

In order to achieve the above object, according to the present invention, an armature and a field pole, a brush and a commutator for supplying a current to the armature, and a brush for pressing the brush against the commutator in a slidable manner. A starter that starts the internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V, which is normally used, in which the brush is made of a material that is higher than a material used when the power supply voltage is 12 V. resistivity and the coefficient of friction is high material, pressure of the pressurizing means is set the power supply voltage is lower than at 12V, pressure of the pressurizing means is the due to a change in the material of the brush It is set low in inverse proportion to the increase in the friction coefficient of the brush.

In order to achieve the above object, according to the present invention, an armature and a field pole, a brush and a commutator for supplying a current to the armature, and a brush for pressing the brush against the commutator so as to be slidably contacted with the commutator. A starter that starts the internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V, which is normally used, in which the brush is made of a material that is higher than a material used when the power supply voltage is 12 V. resistivity and the coefficient of friction is high material, pressure of the pressurizing means is set the power supply voltage is lower than at 12V, the relative 12V is the pressure normally used the pressure means supply It is set low in inverse proportion to the increase in voltage.

In order to achieve the above object, according to the present invention, there are provided an armature and a field pole, a brush and a commutator for supplying a current to the armature, and a pressing means for pressing the brush slidably against the commutator. A starter that starts the internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V, which is normally used, in which the brush is made of a material that is higher than a material used when the power supply voltage is 12 V. It is a material having a high specific resistance and a high friction coefficient. The pressing force of the pressurizing means is set lower than when the power supply voltage is 12 V, the power supply voltage is V2 (V), and the friction coefficient of the brush is μ2. When the power supply voltage is V1 = 12 V, the pressure for sliding the brush into contact with the commutator is P1 (kg / cm).
2) When the power supply voltage is V1 = 12 V, the frictional coefficient of the brush is μ1, and the proportionality constant is k, and the pressing force P2 (kg / cm2) of the pressurizing means is represented by P2 = k · P1. The smaller of μ1 / μ2 and V1 / V2 is k
1, assuming that the larger one is k2, the proportionality constant k satisfies k1 ≦ k ≦ k2.

[0014]

In order to achieve the above object, according to the present invention, an armature and a field pole, a brush and a commutator for supplying a current to the armature, and a brush for slidably pressing the brush against the commutator are provided. A starter that starts the internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V, which is normally used, in which the brush is made of a material that is higher than a material used when the power supply voltage is 12 V. It is a material having a high specific resistance and a high coefficient of friction. The pressing force of the pressurizing means is set lower than when the power supply voltage is 12 V. The pressurizing means includes a spiral portion and a material change of the brush. And a flat portion partially cut away in proportion to an increase in the friction coefficient of the brush.

In order to achieve the above object, according to the present invention, an armature and a field pole, a brush and a commutator for supplying a current to the armature, and a pressing means for pressing the brush against the commutator in a slidable manner. A starter that starts the internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V, which is normally used, in which the brush is made of a material that is higher than a material used when the power supply voltage is 12 V. It is a material having a high specific resistance and a high friction coefficient. The pressing force of the pressing means is set lower than when the power supply voltage is 12V.
And a flat portion which is partially cut out in proportion to an increase in the power supply voltage with respect to V.

[0017]

In the present invention constructed as described above, the power source voltage is made higher than 12 V by using a material of the brush having a specific resistance higher than that used when the power source voltage is normal 12 V, Even if the reactance voltage is greatly increased, a sufficiently large contact voltage drop of the brush can be obtained, no spark flies between the brush and the commutator, and the rectification performance does not deteriorate. In general, when a material having a high specific resistance is used as the material of the brush, the friction coefficient of the brush also increases. However, in the present invention, the pressing force for sliding the brush to the commutator by the pressurizing means reduces the power supply voltage to 12 V.
By setting it lower than V, the frictional force, which is the product of the pressing force and the friction coefficient, does not increase, and the friction loss due to this frictional force does not increase. On the other hand, at this time, the contact voltage drop of the brush increases, but as described above, the current flowing through the brush (armature current) decreases with the same power consumption of the vehicle. Does not increase. Accordingly, the loss on the outer periphery of the commutator, which is the sum of the friction loss and the electric loss (contact voltage drop loss) of these brushes, does not increase.

The product of the brush pressure and the brush friction coefficient is the friction force. In other words, when the friction force is constant, the brush pressure and the friction coefficient of the brush are inversely proportional. That is. In the present invention, the frictional force acting on the brush can be kept constant by setting the pressing force by the pressurizing means low in inverse proportion to the increase in the friction coefficient of the brush due to the change in the material of the brush,
Friction loss does not increase.

In order not to increase the friction loss,
As a result, it is necessary to reduce the pressure applied by the pressurizing means in accordance with the increase in the power supply voltage. The relationship between the pressing force and the power supply voltage is not strict, but is considered to be approximately inversely proportional. In the present invention, the frictional force acting on the brush and hence the frictional loss do not increase for the same reason as described above, by setting the pressing force by the pressurizing means to be low in inverse proportion to the increase of the power supply voltage with respect to 12V.

Further, as described above, the pressure applied by the pressurizing means is set low in inverse proportion to the increase in the friction coefficient of the brush due to the change of the material of the brush or the increase in the power supply voltage with respect to 12 V, thereby providing the power supply voltage. Is V2 (V), the friction coefficient of the brush is μ2, and the pressing force for sliding the brush to the commutator when the power supply voltage is V1 = 12V is P1.
(Kg / cm ² ), when the power supply voltage is V1 = 12 V, the friction coefficient of the brush is μ1, the proportionality constant is k, and the pressing force P2 (kg / cm ² ) of the pressurizing means is P2 = k · P1 (1) k = μ1 / μ2 or k = V1 / V2 (2) This value of k is generally less than one. However, it is conceivable that the friction loss changes due to factors other than the friction coefficient and the pressing force, and the expression for making the pressing force inversely proportional to the power supply voltage as in the latter half of the expression (2) is an empirical expression as described above. Therefore, μ1 / μ2 generally does not coincide with V1 / V2. In the present invention, the smaller one of μ1 / μ2 and V1 / V2 is set to k1, and the larger one is set to k2, and the proportional constant k is set to have a range so as to satisfy k1 ≦ k ≦ k2 (3). By setting an appropriate value of k within this range,
From equation (1), an appropriate pressure P2 of the pressurizing means can be obtained.

At present, the pressing force of a brush of a motor used in industry or the like is about 0.45 (kg / cm ² ), while the pressing force of a brush of a starter is similar to that of an automobile engine. 1.6 to 2.0 (k) because it is directly connected to a device having a very large vibration and has a special use condition that the current density of the brush is as high as 300 (A / cm ² ).
g / cm ² ). When the pressure of the brush is increased in this manner, sparks are reduced and the rectification performance is improved. However, when the pressure is too high, frictional force on the brush sliding surface increases, which is contrary to the gist of the present invention in that frictional loss is not increased. . Therefore, in the present invention, it is preferable to reduce the pressing force within a range in which no spark is generated, and the upper limit thereof is 1.6 kg / c, which is about the lower limit value of the pressing force of a starter motor that is currently generally used.
m ² is preferred. Further, it is not preferable to reduce the pressing force of the brush extremely because it increases the generation of sparks from the brush, and the lower limit thereof is set to 0.45 kg / cm ² which is about the same as the pressing force of an industrial motor which is currently generally used. preferable.

Further, a leaf spring having a spiral portion and a flat portion is used as the pressurizing means, and the friction coefficient between the brush and the commutator is increased by changing the material of the brush, or the power supply voltage is increased in proportion to 12V. By notching a part of the flat part, the elasticity of the leaf spring is reduced, and the pressing force for bringing the brush into sliding contact with the commutator can be reduced in inverse proportion to the increase in the friction coefficient or the increase in the power supply voltage. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A starter according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a starter according to the present embodiment. In FIG. 1, the starter of this embodiment includes a motor unit 100, a magnet switch unit 101, and a shift unit 102, which are housed in a housing 1. The motor unit 100 is fixed to the armature 2 rotatably supported in the housing 1, a field pole (stator) 3 disposed around the armature 2 and configured by a permanent magnet, and coaxially to the armature 2. It has a commutator 4 and a brush 5 that is slidably pressed against the commutator 4. The armature 2 rotates around the output shaft 6 by the current supplied to the commutator 4 from the brush 5. The motor unit 100 is mounted inside a yoke 7 which forms a part of the housing 1.

FIG. 2 is a diagram schematically showing the brush 5 and the commutator 4 of the motor unit 100 according to this embodiment. The brush 5 of this embodiment includes a sliding member 5a formed by firing a mixed powder of graphite or copper, and a lead wire 5b called a pigtail which is embedded and fixed in the sliding member 5a and electrically connected thereto. You. The brush 5 is slidably pressed by the commutator 4, and the brush 5 has a helical portion 8 as a pressing means.
a and a flat spring 8b are fixed.
The leaf spring 8 is provided with a cutout 9 in a part of a flat portion of a conventionally used leaf spring for pressing a brush, so that the pressing force of the leaf spring 8 is reduced. The area of the notch 9 will be described later.

Returning to FIG. 1, the housing 1 has a magnet switch section 101 juxtaposed with the motor section 100. The magnet switch unit 101 includes the coil case 1
1, an electromagnetic coil 12 fixedly disposed inside a coil case 11, a fixed iron core 13 constituting a magnetic circuit when the electromagnetic coil 12 is energized, and a fixed iron core 13 when the electromagnetic coil 12 is energized.
Plunger 14 as a movable body that is attracted to the plunger, and a spring 1 that urges the plunger 14 in the opposite direction to the suction force applied
5

Commutator 4 of motor part 100 of housing 1
On the opposite side, a shift unit 102 is provided. The shift unit 102 has one end connected to the plunger 14 and
a pinion sleeve 22 connected to the other end of the shift lever 21 and slidably fitted to the output shaft 6 of the armature 2 by the movement thereof; and a pinion sleeve fixed to the pinion sleeve 22. 22 and a one-way clutch 23 and a pinion gear 24 fitted to the output shaft 6. The pinion gear 24 rotates in the drive direction together with the output shaft 6, while the output shaft 6 rotates in the opposite drive direction.
The pinion gear 24 is configured to engage with the ring gear 31 of the engine by sliding on the output shaft 6 together with the pinion sleeve 22.

When the electromagnetic coil 12 is switched off, that is, when the starter is not operated, the plunger 14 is separated from the fixed core 13 in the state shown in FIG.
The pinion sleeve 22, the one-way clutch 23, and the pinion gear 24 connected to the plunger 14 via 1 are in the state of FIG. 1 and do not mesh with the ring gear 31 of the engine. On the other hand, when the electromagnetic coil 12 is switched on, that is, when the starter operates, the electromagnetic coil 12 is energized, and the plunger 14 is attached to the stationary core 13 forming a magnetic circuit.
Is sucked. As a result, the shift lever 21 having one end connected to the plunger 14 rotates counterclockwise around the fulcrum 21a in the figure, and the pinion sleeve 22 and the pinion gear 24 connected to the other end of the shift lever 21 are broken lines in the figure. Move to the right as shown by
4 meshes with the ring gear 31 on the engine side. Thus, the output (rotation) of the armature is transmitted to the engine, and the engine is started.

In the starter having the above-described configuration, as described above, the power supply voltage of the motor is set to four times the conventional voltage of 12 V, that is, 48 V, in order to increase the electric power. Therefore, the reactance voltage which affects the rectification performance is greatly increased. In order to avoid the deterioration of the rectification performance between the brush and the commutator due to this, in this embodiment, a brush material having a high specific resistance is used. I do. That is, conventionally, an electric graphite material having a low specific resistance (several 100 μΩ · cm) has been used, but this is changed to a metal graphite material having a high specific resistance (4000 to 8000 μΩ · cm). By using such a material having a high specific resistance, the friction coefficient was conventionally 0.15 to 0.2, whereas the friction coefficient was 0.2 to 0.24 in the present embodiment.
(Usually 1.3 times the catalog value), which causes an increase in friction loss.

In this embodiment, as described with reference to FIG. 2, a notch 9 is provided in the leaf spring 8 for pressing the brush 5 against the commutator 4, and the pressing force of the leaf spring 8 is reduced. That is, the area of the notch 9 of the leaf spring 8 shown in FIG. 2 is determined according to the reduction of the pressing force of the brush 5. This pressing force is calculated by a method described later according to an increase in the friction coefficient of the brush 5 by changing the material of the brush 5 to a material having a high specific resistance as described above and an increase in the power supply voltage with respect to 12V. Is done. As a result, the pressing force of the leaf spring 8, that is, the pressing force of the brush 5 on the commutator 4 decreases in accordance with the increase in the friction coefficient,
The friction loss of the brush 5 does not increase. The method of reducing the pressing force of the leaf spring for pressing the brush is not limited to providing notches in the leaf spring as in the present embodiment. For example, the thickness or the number of turns of the leaf spring may be changed, or a single wire spring ( The pressing force may be reduced by using a helical spring and changing the wire diameter and the number of turns.

Next, a method of determining the pressing force of the brush 5 to be reduced as described above and its operation will be described.
Generally, the total loss Wt (w) on the outer periphery of the commutator 4 is represented by the sum of the brush friction loss Wm (w) and the brush electric loss (contact voltage drop loss) We (w). That is, Wt = Wm + We (4) Further, brush friction loss Wm (w) and brush electric loss (contact voltage drop loss) We (w) are expressed as follows. Wm = 9.8 · μ · Sb · P · v (5) We = Vb · Ia · N (6) where μ is a friction coefficient, Sb is a brush contact area, and P is a brush. , V is the commutator peripheral speed corresponding to the motor speed, Vb is the contact voltage drop, Ia is the armature current, and N is the number of brushes.

FIG. 3 shows a general starter loss configuration in the case where the power supply voltage is 12 V in the related art. As shown in FIG. 3, in the starter, the brush loss, that is, the total loss on the outer circumference of the commutator occupies about 40% at any motor output, and the reduction of the total loss on the outer circumference of the commutator is reduced. Contributes directly to the improvement of motor efficiency.

Now, in a motor whose power supply voltage is high (48 V), the brush contact area Sb, the number of brushes N and the commutator peripheral speed v are the same as those of the conventional motor, and the operating specifications of the motor are the same as those of the conventional motor. Think about it. This condition is often performed in a normal design. At this time, in the motor applied with a high voltage as in this embodiment, the material of the brush 5 is changed to a material having a high specific resistance, so that the contact voltage drop Vb becomes large. And the current (armature current) flowing through the brush becomes smaller, so that the brush electric loss (contact voltage drop loss) We of the formula (6) does not increase. However, when a material having a high specific resistance is used as the material of the brush, the friction coefficient μ of the brush generally increases, so that the brush friction loss Wm of the equation (5) is obtained.
If the pressure P of the brush is a conventional motor (for 12V)
If it is the same as, it will increase by that amount.
Therefore, the total loss Wt on the outer periphery of the commutator, which is the sum of the brush friction loss Wm and the brush electric loss (contact voltage drop loss) We, also increases. In the present embodiment, the brush pressure loss Pm is reduced in accordance with the increase in the friction coefficient μ in (5), so that the brush friction loss Wm can be suppressed to the same level as a conventional power supply voltage of 12 V motor. This does not increase the total loss Wt on the outer periphery of the commutator.

FIG. 5 is a diagram showing the relationship between the power supply voltage of the motor, the brush friction coefficient and the brush friction loss based on values actually measured in advance for the prototype motor. As shown in FIG. 5, when the power supply voltage of the motor is 12 V, the brush friction loss is 660 W.
Met. When the power supply voltage of the motor is increased to 48V, the material of the brush is changed to a material having a high specific resistance, and the pressure of the brush 5 is not changed from the conventional 12V, the friction loss is shown by a solid line in the figure. 1050W, which is a 1.6-fold increase. At this time, the friction coefficient of the brush material used was 0.1 when the power supply voltage of the motor was 12 V as shown by the broken line in the figure.
5. When the power supply voltage of the motor is 48 V, the value is also 0.24 (from the catalog value), which is 1.6 times, which is also 1.6 times. If the pressing force of the brush 5 is not reduced, the friction loss increases depending on the friction coefficient. Was confirmed. In the present embodiment, by reducing the pressing force of the brush 5, the power supply voltage of the motor is increased as shown by a dashed line in the figure, and even if the friction coefficient of the brush 5 increases, the friction loss does not increase. Be able to change at almost constant value.

A method of calculating the value of the pressure of the brush will be described. Assuming that the brush friction loss Wm is constant, that is, not increased, in the equation (5), the pressure P of the brush and the friction coefficient μ are inversely proportional. However, the brush contact area Sb and the commutator peripheral speed v are constant. This also means that the product of the pressing force P of the brush and the friction coefficient μ becomes a frictional force and causes a friction loss. In other words, when the frictional force is constant, the pressing force of the brush and the friction coefficient of the brush are inversely proportional. Therefore, the power supply voltage of the motor of this embodiment is V2 (= 48 V), the pressing force of the brush is P2 (kg / cm ² ), and the friction coefficient of the brush is μ.
2. Also, when the brush pressure when the power supply voltage of the motor is V1 (= 12V) is P1 (kg / cm ² ), the friction coefficient of the brush at that time is μ1, and the proportionality constant is k, P2 = k · P1 (7) k = μ1 / μ2 (8)

In order not to increase the friction loss,
As a result, it is necessary to lower the pressure of the brush in accordance with the increase in the power supply voltage of the motor, but the relationship between this pressure and the power supply voltage is not strict but is approximately inversely proportional. Conceivable. Therefore, k = V1 / V2 (9) can be expressed.

However, it is conceivable that the brush friction loss Wm changes due to factors other than the brush friction coefficient and the brush pressing force, and a formula for making the brush pressing force inversely proportional to the power supply voltage as shown in equation (9). Is an empirical formula,
μ1 / μ2 and V1 / V2 generally do not match. Therefore,
In the present embodiment, the smaller one of μ1 / μ2 and V1 / V2 is k1, and the larger one is k2, and the proportional constant k has a range so as to satisfy k1 ≦ k ≦ k2 (10). This (1
If an appropriate k value is set within the range defined by equation (0), an appropriate brush pressure P2 can be obtained from equation (7).

In the case of the prototype motor shown in FIG. 5, V1 = 12V,
Since V2 = 48V, μ1 = 0.15 and μ2 = 0.24, 0.25 <k ≦ 0.63 (11) Therefore, in this case, an appropriate brush pressure P2 may be set based on the equations (7) and (1), and the area of the notch 9 of the leaf spring 8 (see FIG. 2) may be determined accordingly. Good.

By the way, the pressure P2 of the brush is set within the range determined as described above. However, it is necessary to further limit the pressure P2 to the range according to the actual condition of use in consideration of use conditions and rectification performance. There is. This will be described below. At present, the pressing force (brush spring pressure) of a brush of a motor used in industry or the like is about 0.45 (kg / cm ² ), whereas the pressing force (brush spring pressure) of a brush of a motor for a starter is 1. 0.6 to 2.0 (kg / cm
² ) and high. This is due to the special use condition that the motor for the starter is directly connected to a very vibrating device such as an automobile engine, and the current density of the brush of the starter is as high as 300 (A / cm ² ). That is, if a spark is generated between the brush and the commutator, it directly affects the commutation performance of the motor and deteriorates the commutation. However, the generation of the spark can be reduced by increasing the pressing force of the brush as described above. Therefore, in a starter generally used for a high-speed machine or an application having a lot of external vibrations, the brush pressure is increased in advance. On the other hand, if the pressing force of the brush is too high, the frictional force on the brush sliding surface increases, the amount of mechanical wear increases, which is contrary to the gist of the present invention that the friction loss is not increased,
It is not good to increase this pressure force unnecessarily. Therefore,
In the present embodiment, it is preferable to reduce the pressing force within a range in which no spark is generated, and the upper limit thereof is 1.6 kg, which is about the lower limit value of the pressing force of a starter motor that is generally used now.
/ Cm ² . Further, it is not preferable to reduce the pressing force of the brush extremely because it increases the generation of sparks from the brush, and the lower limit thereof is set to 0.45 kg / cm ² which is about the same as the pressing force of an industrial motor which is currently generally used. preferable. This is represented by the following equation: 0.45 ≦ P2 ≦ 1.6 (12)

As described above, the pressure of the brush is set to P2
(Kg / cm ² ) satisfies the ranges of the expressions (7) and (11), and is determined so as to satisfy the expression (12) in consideration of use conditions and rectification performance.

As described above, according to the present embodiment, the material of the brush 5 is made to have a higher specific resistance than the material used when the power supply voltage is 12 V, and the smaller one of μ1 / μ2 and V1 / V2 is used. Assuming that k1, the larger one is k2, an appropriate value of k is set within a range satisfying k1 ≦ k ≦ k2, and an appropriate pressure P2 of the brush 5 is obtained from P2 = k · P1, and an area corresponding to this is obtained. Since the pressing force of the brush 5 provided with the notch 9 in the leaf spring 8 is set lower than that when the power supply voltage is 12 V, the friction loss due to the brush 5 does not increase, and the electric loss (contact And the total loss on the outer circumference of the commutator, which is the sum of the voltage drop loss). Therefore, the temperature of the commutator 4 rises due to abnormal friction between the brush 5 and the commutator 4,
A good commutation state can be maintained without fear that the commutator 4 is thermally broken.

Further, the upper limit of the pressure P2 of the brush is set to 1.6 kg / cm ² which is about the lower limit of the pressure of the starter motor which is generally used at present, and the lower limit of the pressure P2 of the industrial motor which is usually used at present. 0.45kg / cm ^{2 of} pressure level
Therefore, the pressing force of the brush can be adjusted to the use conditions and the rectification performance in accordance with the actual use.

[0042]

According to the present invention, since the brush is made of a material having a higher specific resistance than the usual brush used when the power supply voltage is 12 V, the rectification performance is deteriorated even if the power supply voltage is increased. Nothing.

Further, since the pressing force for sliding the brush against the commutator by the pressurizing means is set lower than when the power supply voltage is 12 V, the friction loss does not increase, and this and the electric loss (contact voltage drop loss). The loss on the outer periphery of the commutator is also not increased.

Further, since the pressing force by the pressurizing means is set low in inverse proportion to the increase in the friction coefficient of the brush due to the change of the material of the brush, the friction loss does not increase.

Further, since the pressing force by the pressurizing means is set to be low in inverse proportion to the increase of the power supply voltage with respect to 12 V, the friction loss does not increase.

The value of the pressing force of the appropriate pressurizing means is set to be such that the friction coefficient of the brush is increased by changing the material of the brush,
It can be determined in a range determined by an increase in the power supply voltage with respect to 2V.

The upper limit of the pressing force by the pressing means is set to 1.
Since the lower limit is 6 kg / cm ² and the lower limit is 0.45 kg / cm ² , the use conditions and the rectification performance can be adapted to the actual conditions of use.

Further, since the plate spring provided with the notch is used, the pressing force of the pressing means can be reduced according to the friction coefficient of the brush or the power supply voltage.

Further, there is no fear that the temperature of the commutator rises due to abnormal friction between the brush and the commutator, or that the commutator is thermally broken, and a good commutation state can be maintained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a starter according to an embodiment of the present invention.

FIG. 2 is a view schematically showing a brush and a commutator of the starter of FIG. 1;

FIG. 3 is a diagram showing a loss configuration of a general starter in a case where a power supply voltage is a conventional 12V.

FIG. 4 is a diagram showing a relationship between a power supply voltage of a motor, a brush friction coefficient, and a brush friction loss.

[Explanation of symbols]

 Reference Signs List 1 housing 2 armature 3 field pole (stator) 4 commutator 5 brush 6 output shaft 7 yoke 8 leaf spring 8a spiral portion 8b flat portion 9 notch 11 coil case 12 electromagnetic coil 13 fixed iron core 14 plunger 15 spring 21 shift lever 21a fulcrum 22 pinion sleeve 23 one-way clutch 24 pinion gear 100 motor unit 101 magnet switch unit 102 shift unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-243 (JP, A) JP-A-3-204360 (JP, A) Fully open 58-78784 (JP, U) Fully open 7665 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02N 11/00 H02K 13/00

Claims (6)

(57) [Claims] 1. A motor unit comprising: an armature and a field pole; a brush and a commutator for supplying a current to the armature; and a pressurizing means for pressing the brush against the commutator so as to be slidable. In a starter for starting the internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V which is usually used, the brush is made of a material used when the power supply voltage is 12 V.
Specific resistance and coefficient of friction higher than 4,000
It is made of a material having a specific resistance of 8000 μΩ · cm, and a pressure P2 (kg / cm2) of the pressurizing means.
Is lower than when the power supply voltage is 12 V and 0.45
A starter characterized by satisfying ≦ P2 ≦ 1.6. 2. A motor unit comprising: an armature and a field pole; a brush and a commutator for supplying a current to the armature; and a pressurizing means for pressing the brush so as to slidably contact the commutator. In a starter for driving an internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V which is usually used, the material of the brush is a material having a higher specific resistance and a higher friction coefficient than a material used when the power supply voltage is 12 V. The pressurizing force of the pressurizing means is set lower than when the power supply voltage is 12 V, and the pressurizing force of the pressurizing means is inversely proportional to an increase in the friction coefficient of the brush due to a change in the material of the brush. A starter characterized by being set low. 3. A motor unit comprising: an armature and a field pole; a brush and a commutator for supplying a current to the armature; and a pressurizing means for pressing the brush against the commutator so as to be slidable. In a starter for driving an internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V which is usually used, the material of the brush is a material having a higher specific resistance and a higher friction coefficient than a material used when the power supply voltage is 12 V. The pressurizing force of the pressurizing means is set lower than when the power supply voltage is 12 V, and the pressurizing force of the pressurizing means is set lower in inverse proportion to the increase of the power supply voltage with respect to 12 V which is normally used. A starter characterized in that: 4. A motor unit comprising: an armature and a field pole; a brush and a commutator for supplying a current to the armature; and a pressurizing means for pressing the brush so as to slidably contact the commutator. In a starter for driving an internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V which is usually used, the material of the brush is a material having a higher specific resistance and a higher friction coefficient than a material used when the power supply voltage is 12 V. The pressing force of the pressurizing means is set lower than when the power supply voltage is 12 V. When the power supply voltage is V2 (V), the friction coefficient of the brush is μ2, and the power supply voltage is V1 = 12 V, The pressing force for bringing the brush into sliding contact with the commutator is P1 (kg
/ Cm2), when the power supply voltage is V1 = 12V, the friction coefficient of the brush is μ1, the proportionality constant is k, and the pressure P2 (kg / cm2) of the pressurizing means is represented by P2 = k · P1. , Μ1 / μ2 and V1 / V2 are the smaller of k
1. A starter characterized in that the proportional constant k satisfies k1 ≦ k ≦ k2, where k2 is the larger one. 5. A motor unit comprising: an armature and a field pole; a brush and a commutator for supplying a current to the armature; and a pressurizing means for pressing the brush against the commutator in a slidable manner. In a starter for driving an internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V which is usually used, the material of the brush is a material having a higher specific resistance and a higher friction coefficient than a material used when the power supply voltage is 12 V. The pressurizing force of the pressurizing means is set lower than when the power supply voltage is 12 V, and the pressurizing means is proportional to the spiral portion and an increase in the friction coefficient of the brush due to a change in the material of the brush. A starter characterized in that the starter is a leaf spring having a flat portion partially cut away. 6. A motor unit comprising: an armature and a field pole; a brush and a commutator for supplying a current to the armature; and a pressurizing means for pressing the brush against the commutator so as to be slidable. In a starter for driving an internal combustion engine by driving the motor unit with a power supply voltage higher than 12 V which is usually used, the material of the brush is a material having a higher specific resistance and a higher friction coefficient than a material used when the power supply voltage is 12 V. The pressurizing force of the pressurizing means is set lower than when the power supply voltage is 12 V, and the pressurizing means is connected to the helical portion in proportion to an increase in the power supply voltage with respect to the normally used 12 V. A starter characterized by being a leaf spring having a flat portion with a notched portion.