Hybrid vehicle powertrain

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a hybrid vehicle of the type driven by a combination of an internal combustion engine (hereinafter referred to as “engine”) and an electric motor (hereinafter referred to as “motor”).

2. Description of the Related Art

Conventional hybrid vehicles can be generally classified into two groups, the first being a series-type hybrid vehicle in which an engine drives an electric generator and a motor is driven by the electricity to drive the wheels and the second being a parallel-type hybrid vehicle in which the wheels are directly driven by an engine and/or a motor. The hybrid vehicle of the series type is characterized in that the engine is installed separate from the drive train to allow the engine to be run at peak efficiency.

The parallel-type hybrid vehicle can attain an effective energy transmission with a minimum of energy conversion from mechanical to electrical, since the main portion of the drive torque is generated by an engine and an auxiliary torque is obtained from a motor. However, it has been known in the art that engine speed in the parallel-type hybrid vehicle naturally deviates from the most efficient speed because it corresponds to the vehicle speed.

Japanese Utility-molded Application No. Hei 2-7702 proposes a modified hybrid vehicle wherein the engine and generator are optionally disconnected from an output shaft by means of a clutch. When the clutch is engaged the vehicle operates as a parallel-type hybrid vehicle, and when the clutch is released the vehicle operates as a series-type hybrid vehicle. It is therefore possible to release the clutch when the vehicle travels on city streets and to engage the clutch when the vehicle moves at high speed.

However, in such conventional hybrid vehicles, the engine and the motor are arranged on one single axis, so that the whole drive system tends to require a long space along that axis. In a FF-type hybrid vehicle, such a long drive train reduces space for the steering angle and thereby increases the minimum turning radius. Furthermore, because rotary power from both the engine and the motor is output to a common output shaft, the gear ratio for the engine should be the same as that for the motor. Therefore, optimum gear ratios for the engine and the motor cannot be independently determined in designing.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a hybrid vehicle which allows for independent selection of the optimum gear ratio for the engine and for the motor, within a minimum axial length for the drive train, to thereby overcome the problems presented by the above-mentioned conventional hybrid vehicle.

A hybrid vehicle according to the present invention has an internal combustion engine, a generator for generating electricity, an electric motor driven by the generated electricity and a differential gear unit having at least three elements, the first connecting to the generator, the second connecting to a first gear and the third connecting to the internal combustion engine. A second gear is connected to an output shaft extending from the electric motor. A counter shaft carries a third gear which is meshed with both the first and second gears and the differential gear unit is connected to the counter shaft. The internal combustion engine, differential gear system and generator are aligned on a first axis, the electric motor is aligned on a second axis parallel to the first axis, the counter shaft is aligned on a third axis parallel to the first and second axes, and the differential gear system is aligned on a fourth axis parallel to the first, second and third axes. The third axis is disposed inside of a triangle formed first, second and fourth axes as viewed on end.

The counter shaft carries a fourth gear which meshes with a fifth gear in the differential gear unit to drive the differential gear unit.

In one embodiment the first, second and third elements of the differential gear unit are, respectively, a sun gear, a ring gear and a carrier.

In another embodiment, the first, second and third elements of the differential gear system are, respectively, a sun gear, a carrier and a ring gear.

The generator is preferably a magneto-generator or an excitation generator.

The first axis further aligns with a resolver located on the opposite side of the internal combustion engine.

The first and third gears provide a gear ratio different from the gear ratio provided the second and third gears.

The output shaft of the internal combustion engine is rotatably supported at one end by a case, which houses the differential gear unit, generator and electric motor, and has a second end connected to the drive shaft of the generator.

The generator is axially aligned with the output shaft of the engine, as is the first gear meshes with the second element.

The generator is provided with a brake to regulate the rotation thereof, which brake is preferably a wet multiple disk type brake.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a complete drive unit of a hybrid vehicle according to a first embodiment of the present invention;

FIG. 2 is a lateral sectional view of the drive unit of the hybrid vehicle according to the first embodiment of FIG. 1;

FIG. 3 is a first axial sectional view of the drive unit of the hybrid vehicle according to the first embodiment of FIG. 1;

FIG. 4 is a second axial sectional view of the drive unit of the hybrid vehicle according to the first embodiment of FIG. 1; and

FIG. 5 is a fragmentary axial view of the drive unit of a hybrid vehicle according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The above-mentioned and other objects of the present invention will become more fully understood from the following specification, read in light of the drawings which show several preferred embodiments of the present invention. Certain terminology will be used in the following description for convenience in referring to the drawings and should not be considered limiting. For example, the words “up”, “down”, “right” and “left” will designate directions in the drawings to which reference is made.

The words “in” and “out” will refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. Such terminology will include derivatives and words of similar import.

The main components of the drive unit, as shown in FIG. 1, include an engine (E/G) <b>11</b> aligned on a first axis SH<b>1</b> (also see FIG. 2) an output shaft <b>12</b> which is arranged on/the first axis SH<b>1</b> and which serves to transmit power from the engine <b>11</b>, a planetary gear unit <b>13</b> which is aligned on the first axis SH<b>1</b> and which serves as a differential gear unit to change speed of rotation received from the output shaft <b>12</b>, an output shaft <b>14</b> which is also aligned on the first axis SH<b>1</b> and which receives the output from the planetary gear unit <b>13</b>, a first gear <b>15</b> aligned on the first axis SH<b>1</b> and secured to the output shaft <b>14</b>, and a generator (G) <b>16</b> which is arranged on the first axis SH<b>1</b> and which is connected with the planetary gear unit <b>13</b> through the drive shaft <b>17</b>. The output shaft <b>14</b> is in the form of a sleeve which surrounds the output shaft <b>12</b>. The first gear <b>15</b> is arranged adjacent the planetary gear unit <b>13</b> and the engine <b>11</b>.

The planetary gear unit <b>13</b> consists of a sun gear S as a first element, a pinion P meshing with the sun gear S, a ring gear R as a second element meshing with the pinion P, and a carrier CR as a third element carrying the pinion P.

The sun gear S is connected to the generator <b>16</b> through the drive shaft <b>17</b>, the ring gear R is connected to the first gear <b>15</b> through the output shaft <b>14</b>, and the carrier CR is connected to the engine <b>11</b> through the output shaft <b>12</b>.

The generator <b>16</b> is secured on the drive shaft <b>17</b> and consists of a rotor <b>21</b>, a stator <b>22</b> arranged around the rotor <b>21</b>, and a coil <b>23</b> wound around the stator <b>22</b>. Accordingly, the generator <b>16</b> is adapted to generate electricity using the power received from the drive shaft <b>17</b>. The coil <b>23</b> is connected to a battery (not shown) which stores the generated electricity.

A motor (M) <b>25</b> is aligned on a second axis SH<b>2</b> parallel to the above-mentioned first axis SH<b>1</b> (also see FIG. 2) receives electricity from the battery, generates rotary power and outputs the generated power through an output shaft <b>26</b> aligned on the second axis SH<b>2</b>. A second gear <b>27</b> is aligned on the second axis SH<b>2</b> and secured to the output shaft <b>26</b>. The motor <b>25</b> includes rotor <b>37</b>, a stator <b>38</b> arranged around the rotor <b>37</b>, and a coil <b>39</b> wound around the stator <b>38</b>. The coil <b>39</b> is connected with the battery (not-shown) to receive electricity.

A counter shaft <b>31</b> is arranged on a third axis SH<b>3</b> parallel to the first and second axes SH<b>1</b>, SH<b>2</b> to rotate the wheels (not-shown) in the same direction as the engine <b>11</b>. The counter shaft <b>31</b> carries, securely connected thereto, a third gear <b>32</b>. Accordingly, the third gear <b>32</b> is meshed with both the first gear <b>15</b>, which rotates in one direction, and the second gear <b>27</b> which rotates in the opposite direction. The counter shaft <b>31</b> further carries a fourth gear <b>33</b> having a smaller diameter and less teeth than the third gear <b>32</b>.

Arranged on a fourth axis SH<b>4</b>, which is parallel to the above-mentioned first axis SH<b>1</b>, second axis SH<b>2</b>, and third axis SH<b>3</b>, is a fifth gear <b>35</b> meshing with the fourth gear <b>33</b>. The fifth gear <b>35</b> is securely connected to a differential gear unit <b>36</b> so that rotation received by the fifth gear <b>35</b> is transmitted to and changed into differential motion in the differential gear unit <b>36</b> to thereby drive the wheels.

Thus, the third gear <b>32</b> is arranged to receive power not only from the engine <b>11</b> but also from the motor <b>25</b>. Accordingly, the hybrid vehicle of the present invention can be driven in three modes, the first being an engine drive mode limited to use of the engine, the second being a motor drive mode limited to use of the motor, and the third being an engine-motor drive mode using both the engine and the motor.

The generator <b>16</b> regulates the rotational speed of the drive shaft <b>17</b>, controlling the electricity generated in order to operate the engine <b>11</b> and the motor <b>2</b>B under the most efficient conditions. The generator <b>16</b> may be a starter for the engine <b>11</b> on occasion.

As has been described above, the engine <b>11</b> and the motor <b>25</b> are respectively arranged on different axes, so that the axial length of the drive system can be decreased. In a FF-type hybrid vehicle utilizing such arrangement, the drive system allows room for a sufficient steering angle to minimize the turning radius.

The rotation of the engine <b>11</b> is output through the output shaft <b>12</b> to the first gear <b>15</b> and that of the motor <b>25</b> is output through the output shaft <b>26</b> to the second gear <b>27</b>, whereby the gear ratio of the first gear <b>15</b> and the third gear <b>32</b> and the gear ratio of the second gear <b>27</b> and the third gear <b>32</b> can be different from each other. This allows for flexibility in design of the drive system, especially the engine <b>11</b> and motor <b>25</b>, to minimize size.

Since the third gear <b>32</b> on the fourth axis is rotatably driven by both the first gear <b>15</b> and the second gear <b>27</b> and the rotation of the fourth gear <b>33</b> is transmitted to the fifth gear <b>35</b>, as can be seen from FIG. 2, a radial force F<b>1</b> is imparted from the first gear <b>15</b> to the third gear <b>32</b>, a radial force F<b>2</b> is imparted from the second gear <b>27</b> to the third gear <b>32</b> and a radial reaction force F<b>3</b> is imparted from the fifth gear <b>35</b> to the fourth gear <b>33</b>. However, because the third axis SH<b>3</b> is located within a triangle defined by the first axis SH<b>1</b>, second axis SH<b>2</b> and fourth axis SH<b>4</b>, when viewed on end, the radial forces F<b>1</b>, F<b>2</b> and F<b>3</b> are counterbalanced as a whole, which counterbalancing reduces the stress on bearings supporting the counter shaft <b>31</b>.

The details of the hybrid vehicle of the first embodiment will now be described with reference to FIGS. 3 and 4.

As seen in FIG. 3, the engine output shaft <b>12</b> is coupled to a flywheel <b>51</b>. The rotational power of the flywheel <b>51</b> is input to the planetary gear unit <b>13</b> which includes a sun gear S, a pinion P meshing with the sun gear S, a ring gear R meshing with the pinion P, and a carrier CR rotatably supporting the pinion.

The carrier CR is securely connected to the drive shaft <b>53</b> and rotates the pinion P. One end (hereinafter the “Forward end”) of the drive shaft <b>53</b> near the engine <b>11</b> is rotatably supported by the casing <b>55</b> through bearing <b>54</b> and the other end (hereinafter the “Rearward end”) of the shaft <b>53</b>, remote from the engine <b>11</b>, is supported by the drive shaft <b>17</b> through the bearing <b>57</b>.

The hollow output shaft <b>14</b> is fitted over and supported by the drive shaft <b>53</b> through the bearing <b>58</b>. The output shaft <b>14</b> is formed as a sleeve and its forward end abuts to a flange <b>60</b> formed on the drive shaft <b>53</b> via thrust bearing <b>59</b> and its rearward end abuts the carrier CR via a thrust bearing <b>61</b>.

The rearward end of the output shaft <b>14</b> carries a ring gear flange <b>62</b> which is securely connected to the ring gear R. Incidentally, the first gear <b>15</b> is integrally formed on output shaft <b>14</b>.

The drive shaft <b>17</b> has an opening at its forward end which receives the rearward end of the drive shaft <b>53</b> rotatably supported therein by bearing <b>57</b>. Furthermore, the drive shaft <b>17</b> is supported by the casing <b>56</b> at its forward end through the bearing <b>65</b>. The drive shaft <b>17</b> extends forward beyond the bearing <b>65</b>, to where it is splined to the sun gear S. The rearward end of the drive shaft <b>17</b> is rotatably supported by the casing <b>67</b> through bearing <b>66</b>. The drive shaft <b>17</b> also extends rearward beyond the bearing <b>66</b> to where it couples with a resolver <b>70</b>. The resolver <b>70</b> is connected with the drive shaft <b>17</b> without any gearing to avoid the problem of backflash and to ensure positional accuracy. The resolver <b>70</b> itself is isolated from the engine by the generator <b>16</b> on the drive shaft <b>17</b>, so that it can be easily detached for maintenance.

The generator <b>16</b> is centrally located on and securely coupled to the drive shaft <b>17</b>. The generator <b>16</b> is composed of a rotor <b>21</b>, a stator <b>22</b> provided around the rotor <b>21</b> and mounted on the casing <b>56</b>, and a coil wound around the stator <b>22</b>. The generator <b>16</b> is a magneto-generator in which the rotor <b>21</b> is a permanent magnet <b>71</b> with alternating N- and S-poles. The generation of electricity by the generator <b>16</b> is by conversion of rotational energy received from the drive shaft <b>17</b>. The coil <b>23</b> is electrically connected through a conventional power control system to a battery for storing the generated electricity.

The sun gear S of the planetary gear unit <b>13</b> is connected to the generator <b>16</b> and the carrier CR is connected to the engine <b>11</b>. Accordingly, if the number of teeth on the ring gear R is twice the number on the sun gear, the torque of the generator <b>16</b> can be controlled at ⅓ that of the engine <b>11</b> to thereby minimize the size of the generator <b>16</b>.

When generation of electricity is not required of the generator <b>16</b>, rotation of the rotor <b>21</b> will naturally decrease the rotational speed of the first gear <b>15</b>. It is therefore preferred to additionally provide a wet multiple disk type brake B, assisted by a hydraulic servo <b>73</b>, between the rotor <b>21</b> and the casing <b>67</b>. The activation of the brake B is by feed of oil pressure to the hydraulic servo <b>73</b> and release is by draining the oil pressure.

The counter shaft <b>31</b> is rotatably supported at its forward and rearward ends by the casing <b>56</b> through the bearings <b>75</b> and <b>76</b>, respectively. The counter shaft <b>31</b> carries the third gear <b>32</b> at its rearward end which, in turn, is meshed with the first gear <b>15</b>.

The motor <b>25</b> includes an output shaft <b>26</b>, rotor <b>37</b>, stator <b>38</b> arranged around the rotor <b>37</b> and coil <b>39</b> wound around the stator <b>38</b>. The forward end of the output shaft <b>26</b> is supported by the bearing <b>78</b> for rotation relative to the casing <b>55</b> and its rearward end is supported by the bearing <b>79</b> for rotation relative to the casing <b>67</b>.

The above-mentioned motor <b>25</b> produces rotational power from electricity received by the coil <b>39</b> which is electrically connected to the power control system including a battery. The output shaft <b>26</b> extends through a supporting bearing <b>78</b> to a resolver <b>80</b> located near the engine <b>11</b>.

The forward end of the output shaft <b>26</b> carries the second gear <b>27</b> which is meshed with the third gear <b>32</b>. Accordingly, the rotation generated by the motor <b>25</b> is transmitted to the counter shaft <b>31</b> through the output shaft <b>26</b>, the second gear <b>27</b> and the third gear <b>32</b>.

As can be seen from the drawings, the forward end of the counter shaft <b>31</b> is integral with the fourth gear <b>33</b> to which the differential gear unit <b>36</b> is connected. The differential gear unit <b>36</b> consists of a differential case <b>81</b> having the fifth gear <b>35</b> on its outer periphery, a pinion shaft <b>82</b> mounted on the differential case <b>81</b>, a pinion <b>83</b> rotatably supported on the pinion shaft <b>82</b> and right and left side gears <b>84</b> (only the left side gear is shown in the drawing) meshing with the pinion <b>83</b> so that the rotation received by the fifth gear <b>35</b> is differentially transmitted to the side gears <b>84</b>. Since the side gear <b>84</b> is securely mounted on the drive shaft <b>85</b>, the differentially transmitted rotation is finally transmitted through drive shaft <b>85</b> to a wheel (not shown).

A second embodiment of the present invention will be described with reference to FIG. <b>5</b>. Since the motor <b>25</b>, the differential gear system <b>36</b> and the related components have the same or similar structure as those of the first embodiment, their description is omitted here and FIG. 4 should be referred to for their explanation.

As shown in FIG. 5, an output shaft <b>12</b> outputs rotational power from the engine <b>11</b> to a flywheel <b>51</b>. The rotational power received by flywheel <b>51</b> is input to a planetary gear unit <b>113</b> through a damper device <b>52</b> and a drive shaft <b>153</b>. The planetary gear unit <b>113</b> consists of a sun gear S as the first element, a pinion P meshing with the sun gear S, a ring gear R as the third element meshing with the pinion P, and a carrier CR as the second element supporting the pinion P.

A flange portion <b>160</b> is formed at the rearward end of the drive shaft <b>153</b> and fixed thereto is a ring gear flange <b>162</b> on which the ring gear R is mounted. The rearward end of the drive shaft <b>153</b> is rotatably supported by the casing <b>55</b> through a bearing <b>54</b> and has a central recess which receives the drive shaft <b>117</b> rotatably supported therein by bearing <b>157</b>.

The drive shaft <b>117</b> is centrally and rotatably supported by the case <b>56</b> through the bearing <b>65</b>. The drive shaft <b>117</b> is splined to the sun gear S rearward of and adjacent to the bearing <b>157</b>. The rearward end portion of the drive shaft <b>117</b> is rotatably supported by the casing <b>67</b> through bearing <b>66</b>. The end of the drive shaft <b>117</b> extending rearward of the bearing <b>66</b> carries a brush <b>170</b>. The brush <b>170</b> is disposed on the drive shaft <b>117</b> on the opposite side of the engine <b>11</b> with the generator <b>16</b> in between to facilitate maintenance of the brush <b>170</b>.

The outer periphery of the drive shaft <b>117</b> rotatably supports output shaft <b>14</b> via a bearing <b>158</b>. The output shaft <b>14</b> is formed as a sleeve with its forward end abutting the sun gear S via a thrust bearing <b>159</b> and its rearward end abutting the casing <b>56</b> via thrust bearing <b>161</b>. The first gear <b>15</b> is integrally formed on the output shaft <b>14</b>.

As seen in FIG. 5, the generator <b>16</b> is located at the rearward end of drive shaft <b>117</b>. The generator <b>16</b> is securely connected to the drive shaft <b>117</b> and includes rotor <b>21</b>, stator <b>22</b> arranged around the rotor <b>21</b> and mounted on the casing <b>56</b>, coil <b>171</b> wound around the rotor <b>21</b> and coil <b>23</b> wound around the stator <b>22</b>. The generator <b>16</b> is a magneto-generator with its coil <b>171</b> electrically connected to receive excitation power through the brush. The generator <b>16</b> generates electricity from the rotational energy received from the drive shaft <b>117</b>. The coil <b>23</b> is electrically connected to a battery for supplying and storing electricity in the battery.

Since the sun gear S of the planetary gear unit <b>113</b> is connected to the generator <b>16</b> and the ring gear R is connected to the engine <b>11</b>, if the number of teeth on the ring gear R is twice the number on the sun gear, the torque of the generator <b>16</b> will be ½ that of the engine <b>11</b>, thus minimizing the size of the generator <b>16</b>.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.