JP2017101564A - Engine starter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine starter capable of reducing energy to be required for starting an engine, reducing noise during cranking, and improving durability.SOLUTION: When energy accumulated in the engine from the time when cranking is started exceeds energy to be required up to the time of the initial combustion of the engine, a motor control device 4 generates reverse torque in a motor 2 to reduce the rotating speed of the motor 2. Thus, the rotating speed of the motor 3 can be reduced at a timing before the initial combustion, and so starting energy to be required for starting the engine can be reduced. Besides, the rotating speed of the motor 3 can be reduced at a timing when the engine is estimated to go beyond the compression top dead center of an initial combustion cycle with the inertial revolution, and so tooth hammering noise of a pinion 5 and a ring gear 8 can be reduced in comparison with a normal starter and friction between gears can be suppressed, therefore improving the durability of the pinion 5 and the ring gear 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine starter capable of reducing energy required for starting an engine by a starter.

Patent Document 1 is known as a conventional technique.
The document 1 predicts a combustion cycle in which the first air-fuel mixture in the cylinder is burned from the engine stop state, and releases the starter pinion from the engine ring gear during the predicted first combustion cycle. A method is disclosed. According to this method, it is not necessary to engage the pinion with the ring gear until the engine is completely exploded, and the pinion can be quickly detached from the ring gear. As a result, it is possible to reduce starter deterioration, current consumption, clutch deterioration due to overrun, engine noise and vibration.

Japanese Patent Application Laid-Open No. 2011-127591

However, in the prior art of Patent Document 1, the pinion is detached from the ring gear during the expansion stroke of the cylinder where combustion is predicted to occur. That is, the pinion does not leave the ring gear until at least the compression top dead center in the first combustion cycle is exceeded.
On the other hand, if it is possible to estimate the timing at which the engine can exceed the compression top dead center in the first combustion cycle by inertial rotation, the pinion can be detached from the ring gear at that timing. In this case, even if cranking by the starter is stopped at the above timing, it is possible to reach the first explosion by inertial rotation of the engine.

However, in the prior art of Patent Document 1 that does not have a means for estimating the timing, cranking by the starter cannot be stopped until at least the compression top dead center in the first combustion cycle is exceeded. In other words, since the starter is not turned off before the compression top dead center in the first combustion cycle, there is a point to be improved in order to reduce the starting energy.
The present invention has been made to solve the above problems, and an object of the present invention is to provide an engine starter capable of reducing energy required for starting the engine.

  The present invention according to claim 1 includes a starter having a clutch for transmitting the rotation of the motor to the pinion, and a motor control device for controlling the operation of the motor, and the ring gear connected to the crankshaft of the engine is connected to the ring gear. An engine starter that engages a pinion and transmits the rotational force generated in the motor to the pinion to rotate the ring gear to crank the engine. The motor control device starts the cranking The energy stored in the engine and the energy required until the first explosion of the engine are calculated, and when the energy stored in the engine exceeds the energy required until the first explosion, the rotation of the motor The speed is reduced.

If the energy stored in the engine after the cranking is started exceeds the energy required for the first explosion, then the first explosion will occur due to the inertial rotation of the engine even if the engine is not cranked by the starter. Can do.
In the present invention, when the energy stored in the engine exceeds the energy required before the first explosion, the motor rotation speed is reduced even before the engine first explosion, so the engine can be started with the minimum starting energy. Can be done. For this reason, compared with the prior art of patent document 1 which performs cranking of the engine by a starter continuously after the first explosion, the starting energy required in order to start an engine can be reduced.

1 is an overall configuration diagram of an engine starter according to Embodiment 1. FIG. It is a flowchart which shows the process sequence of a motor control apparatus. It is an engine stroke diagram. It is a graph which shows the relationship between a volume and a pressure. It is a graph of the engine speed and the motor speed when a reverse torque is generated in the motor. It is a graph which shows an engine speed and motor speed when a clutch connects, when reverse torque is generated in a motor.

  The mode for carrying out the present invention will be described in detail with reference to the following examples.

[Example 1]
As shown in FIG. 1, the engine starting device 1 according to the first embodiment includes a starter 2 that cranks the engine by the rotational force of the motor 3 and a motor control device 4 that controls the operation of the motor 3. In addition to the motor 3, the starter 2 includes a pinion 5, a reduction gear (not shown), a clutch 6, a solenoid (not shown), and the like described below.
The pinion 5 is helically splined on the shaft of the output shaft 7 driven by the motor 3 and arranged so as to be movable on the shaft of the output shaft 7, and the output shaft 7 is moved in the counter-motor direction (left direction in the figure). It can move and mesh with the ring gear 8 connected to the crankshaft of the engine.

The speed reducer is constituted by, for example, a planetary gear device, and decelerates the rotation speed of the motor 3 at a predetermined reduction ratio.
The clutch 6 is disposed between the motor 3 and the pinion 5 and is connected when torque is transmitted from the motor 3 to the pinion 5, and is disconnected when the pinion 5 is rotated by the engine to transmit torque. It is a one-way clutch that shuts off.
The solenoid has a function of pushing the pinion 5 in the direction opposite to the motor by electromagnetic force.
The motor 3 is an AC motor in which a three-phase alternating current is applied to the stator winding 3a to generate a rotating magnetic field, and a rotor (not shown) rotates in accordance with the rotating magnetic field.

The motor control device 4 is a known inverter that converts the DC voltage of the battery V into an AC voltage and applies the AC voltage to the motor 3. The switching element 4a such as a MOSFET or IGBT and the current flowing to the motor 3 are fed back to switch the switching element. And a control circuit 4b for controlling the on / off operation of 4a.
The motor control device 4 receives an engine start signal output from an engine ECU (not shown), starts energization of the motor 3, and then rotates the motor 3 when a predetermined condition (described later) is satisfied. Perform motor speed control to reduce the speed.
Hereinafter, the procedure of motor speed control by the motor control device 4 will be described based on the flowchart shown in FIG.

The following steps S1 to S12 correspond to S1 to S12 attached to each step of the flowchart shown in FIG.
In step S1, an initial crank angle θ ₀ is acquired. For example, as shown in FIG. 3, when the ignition sequence is performed in the order of cylinder 1 → cylinder 3 → cylinder 4 → cylinder 2 in a four-cylinder four-cycle engine, the initial position θ ₀ = 50 [deg] in the compression stroke of cylinder 1 To get.
In step S2, the rotational speed ωm, the rotational angle θm, and the torque Tm of the motor 3 are acquired.
In step S3, the output energy Pm of the motor 3 and the kinetic energy Pke_m of the motor 3 are calculated. The output energy Pm of the motor 3 may be obtained by integrating the motor torque Tm at an angle from the initial position θ ₀ to the calculation timing θ ₁ as shown in the equation (1).
Formula (1)

The kinetic energy Pke_m of the motor 3 can be calculated from the inertia Jm of the motor 3 and the rotational speed ωm, as shown in Equation (2).
Formula (2): Pke_m = 1/2 · Jm × ωm ²
In step S4, engine input energy Pe is calculated. The output energy Pm of the motor 3 obtained by the previous equation (1) can be converted into its own kinetic energy Pke_m and the engine input energy Pe as shown in the following equation (3). Therefore, the input energy Pe of the engine can be obtained by subtracting the kinetic energy Pke_m from the output energy Pm of the motor 3 as shown in Equation (4).
Formula (3): Pm = Pke_m + Pe
Formula (4) ... Pe = Pm-Pke_m

It calculates a current crank angle theta ₁ at step S5. The crank angle theta ₁ is a rotation angle variation Δθm of the motor 3 changes during steps S2 to step S5 is divided by the gear ratio of the reduction gear, adds that value to the initial crank angle theta ₀ obtained in step S1 Can be obtained.
In step S6, the cylinder internal volume v in the compression stroke is calculated. Here, it can be obtained using a map in which the crank angle θ and the cylinder internal volume v are related.
In step S7, gas energy Pc in the cylinder and engine kinetic energy Pke_e in the compression stroke are calculated.

P gas energy Pc in the cylinder, when described in the graph of FIG. 4 showing a relationship between a volume v and pressure P, the gas pressure p ₀ in the cylinder while the cylinder volume is reduced from v ₀ to v _{1 When} increased to _1, it is represented by the area of the hatched portion in the figure. That is, as shown in Equation (5), it can be calculated by integrating the gas pressure in the cylinder by the volume. Note that the cylinder pressure at the initial position is the atmospheric pressure p ₀ and the specific heat ratio of air is γ.
Formula (5)

The kinetic energy Pke_e of the engine can be calculated from the inertia Je of the engine and the rotational speed ωe, as shown in Equation (6).
Formula (6) Pke_e = 1/2 · Je × ωe ²
In step S8, the engine friction Tl is calculated from equation (7). α is a friction weighting coefficient, and the initial value is “1”.
Formula (7) ... Tl = αPl / (θ ₁ −θ ₀ )
Pl included in the equation (7) is the energy loss of the engine load. As shown in the following equation (8), the engine input energy Pe, the engine kinetic energy Pke_e, and the gas energy Pc in the cylinder It can be calculated.
Formula (8): Pl = Pe-Pke_e-Pc

In step S9, the engine target rotational speed at the time of the first explosion is ωe_ref, and the required energy Pn until the first explosion at the current calculation timing (position of θ ₁ = 120 [deg] in FIG. 3) is calculated from Equation (9). . In the stroke diagram of FIG. 3, the ▽ mark given to the compression top dead center of the cylinder 3 indicates the timing of the first explosion.
Formula (9)

In step S10, the energy Pe_t stored in the engine at the current calculation timing is calculated from Equation (10).
Formula (10): Pe_t = Pke_e + Pc
In step S11, it is determined whether or not a predetermined condition defined by the mathematical formula (11) is satisfied. If satisfied (determination result YES), the process proceeds to step S12. X included in Equation (11) is a threshold value, and the initial value is “0”.
Formula (11) ... Pe_t-Pn> X
In step S12, the rotational speed of the motor 3 is reduced. Specifically, power supply to the motor 3 is stopped. Alternatively, a torque opposite to the rotation direction of the motor 3 is generated, that is,
The motor 3 is decelerated by applying a braking torque.

[Operation and Effect of Example 1]
The engine starter 1 according to the first embodiment estimates the timing at which the engine exceeds the compression top dead center of the first combustion cycle due to inertial rotation, and decelerates the rotational speed of the motor 3 at that timing. That is, the energy Pe_t stored in the engine after the cranking is started and the energy Pn required until the first explosion of the engine are calculated, and when Pe_t exceeds Pn, the rotational speed of the motor 3 is decelerated. Thereby, since the rotational speed of the motor 3 can be decelerated at the timing before the first explosion, the engine is started as compared with the conventional technique of Patent Document 1 in which the cranking of the engine by the starter 2 is continuously performed after the first explosion. The starting energy required to do this can be reduced.

Further, since the rotational speed of the motor 3 is decelerated at the timing when the engine is estimated to be able to exceed the compression top dead center of the first combustion cycle due to inertial rotation, the teeth of the pinion 5 and the ring gear 8 are compared with those of a normal starter. The hitting sound can be reduced. Further, since the friction between the gears can be suppressed, the durability of the pinion 5 and the ring gear 8 is also improved.
Further, when generating torque in the direction opposite to the rotation direction of the motor 3, the coupling period of the clutch 6 can be shortened compared to when the energization to the motor 3 is stopped. Therefore, the rattling noise between the pinion 5 and the ring gear 8 Can be further reduced, and the durability is further improved. Further, by generating reverse torque in the motor 3, the kinetic energy of the motor 3 can be converted into electric energy and returned to the battery V, which contributes to energy saving.

When obtaining the energy Pn required until the first explosion in step S9, for example, the engine friction Tl that changes depending on the oil viscosity is included in the equation (9), so that the calculation accuracy of the energy Pn is improved.
In step S7, when calculating the gas energy Pc in the cylinder, the calculation error due to the change in atmospheric pressure can be corrected by adding the atmospheric pressure p ₀ to the equation (5), so the calculation accuracy of the gas energy Pc is improved. To do.

Hereinafter, other embodiments according to the present invention will be described.
Note that components and configurations that are common to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted.
[Example 2]
In the second embodiment, it is estimated that the clutch 6 is connected after the energization to the motor 3 is stopped in order to decelerate the rotation speed of the motor 3 in step S12 described in the first embodiment, and the rotation speed of the motor 3 is also increased. This is an example in which energization of the motor 3 is started again when the motor speed decreases to a predetermined rotational speed. The predetermined rotational speed is the lowest rotational speed at which the engine can complete explosion.

In the second embodiment, since the motor 3 is not energized until the rotational speed of the motor 3 decreases to a predetermined rotational speed, the generation period of the rattling noise between the pinion 5 and the ring gear 8 can be shortened. Friction can also be reduced. As a result, noise can be reduced and durability can be improved. In addition, since the cranking by the starter 2 can be resumed by starting energization of the motor 3 when the rotational speed of the motor 3 is reduced to a predetermined rotational speed, the engine can be reliably started.
When the clutch 6 is connected from a non-connected state, the rotational speed of the motor 3 changes, so that the connection of the clutch 6 can be estimated from the change in the rotational speed of the motor 3.

Example 3
In this third embodiment, in step S12 described in the first embodiment, in order to decelerate the rotation speed of the motor 3, a torque opposite to the rotation direction of the motor 3 is generated, and then the target engine speed at the first explosion is generated. This is an example in which the motor 3 is driven using a lower predetermined rotational speed as a command value.
Specifically, as shown in FIG. 5, the motor 3 is driven by changing the rotational speed command value of the motor 3 from A to B (A> B) at time t1. The rotational speed command value B is a predetermined rotational speed that is lower than the engine target rotational speed ωe_ref at the time of the first explosion. As a result, the motor 3 is driven at the rotation speed command value A from time t0 (start of energization) to time t1, and then decelerated between the time t1 and t2, and thereafter (after t2), the rotation speed command value B It is driven by.

In the third embodiment, after the rotational speed command value of the motor 3 is changed from A to B and the rotational speed of the motor 3 is decelerated, the clutch 6 of the starter 2 is not connected. Therefore, the pinion is compared with a normal starter. 5 and the ring gear 8 can be reduced. Further, since the friction between the gears can be suppressed, the durability of the pinion 5 and the ring gear 8 is also improved.
By the way, if the actual friction is larger than the estimated friction, the engine speed at the compression top dead center may be lower than the rotational speed command value B of the motor 3 as shown in FIG. Therefore, when the engine is next started, the weighting coefficient α included in Equation (7) is increased to calculate the friction Tl. In addition, when IG (ignition) is turned off by the driver's key operation, that is, when the power supply to the motor control device 4 is cut off, α is initialized.

  As a result, the energy Pn required until the first explosion increases, and in order for the condition of Equation (11) to be satisfied, it is necessary to delay the timing for decelerating the rotational speed of the motor 3 (hereinafter referred to as the deceleration timing). is there. That is, since the energy Pe_t stored in the engine is increased by delaying the deceleration timing of the motor 3, the engine rotational speed at the compression top dead center is increased and exceeds the rotational speed command value B of the motor 3, whereby the clutch 6 Can be avoided. The threshold value X included in Equation (11) described in the first embodiment is set according to the rotational speed difference between the engine target rotational speed ωe_ref at the first explosion and the rotational speed command value B of the motor 3.

[Modification]
The motor 3 described in the first embodiment is an AC motor that varies the rotational speed according to the frequency of the AC voltage, but the present invention can also be applied to a DC motor. For example, the motor control device 4 can adjust the rotational speed of the DC motor by converting the DC voltage applied to the DC motor to an arbitrary voltage by PWM control of the on / off operation of the switching element 4a.
In the first embodiment, the calculations of the formulas (1) to (11) are performed by the motor control device 4, but another ECU may perform the calculations. For example, the engine ECU performs calculations and sends the speed command value of the motor 3 and the voltage DUTY command value to the motor control device 4 by communication or the like, whereby similar control can be realized.
In the first embodiment, the case where the motor control device 4 configures an inverter has been described. However, the motor control device 4 may be configured separately from the inverter.

1 Engine starter 2 Starter 3 Motor 4 Motor controller 5 Pinion 6 Clutch 8 Ring gear

Claims (9)

A starter (2) having a clutch (6) for transmitting the rotation of the motor (3) to the pinion (5);
A motor control device (4) for controlling the operation of the motor;
An engine starter for cranking the engine by meshing the pinion with a ring gear (8) connected to the crankshaft of the engine, transmitting the rotational force generated in the motor to the pinion and rotating the ring gear ( 1)
The motor control device calculates energy (Pe_t) stored in the engine after the cranking is started and energy (Pn) required until the first explosion of the engine, and the energy stored in the engine is An engine starter characterized by decelerating the rotational speed of the motor when the energy required before the first explosion is exceeded. The engine starter according to claim 1,
The engine control device is characterized in that the motor control device decelerates the rotation speed of the motor by stopping energization of the motor. The engine starter according to claim 1,
The engine control device according to claim 1, wherein the motor control device reduces the rotational speed of the motor by generating a torque in a direction opposite to the rotational direction of the motor. In the engine starting device according to any one of claims 1 to 3,
The motor control device takes into account an energy loss due to the friction (Tl) of the engine when calculating the energy required until the first explosion after energizing the motor. apparatus. In the engine starting device according to claim 2,
The motor control device resumes energization to the motor when it is estimated that the clutch is engaged after the energization to the motor is stopped and the rotation speed of the motor has decreased to a predetermined rotation speed. An engine starter characterized by. In the engine starting device according to claim 3,
The motor control device generates torque in the direction opposite to the rotation direction of the motor, and then drives the motor using a predetermined rotation speed lower than the target rotation speed (ωe_ref) of the engine at the first explosion as a command value. An engine starting device. The engine starter according to claim 6, wherein
The motor control device takes into account the energy loss due to the friction (Tl) of the engine when calculating the energy required until the first explosion after energization of the motor, and before the first explosion, An engine starter characterized in that, when it is estimated that the clutch is engaged, the weighting coefficient (α) given when calculating the friction is increased. In the engine starting device according to any one of claims 1 to 7,
The motor control device calculates the energy stored in the engine by adding the kinetic energy (Pke_e) of the engine and the gas energy (Pc) in the cylinder, and changes the gas energy in the cylinder to a change in atmospheric pressure. An engine starter characterized in that correction is made accordingly. The engine starting device according to claim 5 or 7,
The engine control device, wherein the motor control device estimates that the clutch is engaged from a change in the rotation speed of the motor.

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