Engine balancer

1. An internal combustion engine comprising:

a crankshaft including a first end and a second end opposite the first end, the crankshaft defining a crank axis, the crankshaft rotatable about the crank axis;

a camshaft defining a camshaft axis, the camshaft rotatable about the camshaft axis;

a cam drive assembly operable to transfer rotation from a first end of the crankshaft to the camshaft;

a balance mass rotatable around the crank axis at the first end of the crankshaft; and

a balancer drive assembly operable to drive the balance mass through the cam drive assembly.

2. The internal combustion engine of claim 1 , wherein the cam drive assembly includes a first toothed wheel that is rotatable with the crankshaft about the crank axis, and a second toothed wheel driven by the first toothed wheel.

3. The internal combustion engine of claim 2 , wherein the balancer drive assembly includes a third toothed wheel concentric with the second toothed wheel, and a fourth toothed wheel driven by the third toothed wheel and concentric with the balance mass.

4. The internal combustion engine of claim 3 , wherein the third toothed wheel is integrally rotatable with the second toothed wheel.

5. The internal combustion engine of claim 4 , wherein the fourth toothed wheel is integrally rotatable with the balance mass in an opposite direction of rotation as the crankshaft.

6. The internal combustion engine of claim 2 , wherein the cam drive assembly further includes a camshaft drive wheel that is rotatable with the second toothed wheel to drive the camshaft.

7. The internal combustion engine of claim 1 , wherein the camshaft, the cam drive assembly, the balance mass, and the balancer drive assembly are supported by a frame, and wherein the camshaft, the cam drive assembly, the balance mass, the balancer drive assembly, and the frame define a balancer module.

8. The internal combustion engine of claim 7 , wherein the balancer module is removably coupled to the first end of the crankshaft and wherein the balancer module is a first balancer module and the internal combustion engine includes a second balancer module coupled to the second end of the crankshaft, the second balancer module including a camshaft, a cam drive assembly, a balance mass, and a balancer drive assembly.

9. The internal combustion engine of claim 7 , wherein the balancer module further includes a variable valve timing unit operable to adjust rotation phasing of the camshaft relative to the crankshaft.

10. The internal combustion engine of claim 1 , wherein the cam drive assembly is a down-speed device that drives the camshaft at a reduced speed relative to the crankshaft, and the balancer drive assembly is an up-speed device that drives the balance mass at an increased speed relative to the camshaft.

11. The internal combustion engine of claim 1 , wherein the balance mass is rotatably supported on the first end of the crankshaft such that the balance mass and the crankshaft rotate concentrically, in opposite directions, with a shared center of rotation at the crank axis.

12. The internal combustion engine of claim 1 , wherein the camshaft is a first camshaft and the internal combustion engine further comprises a second camshaft driven by the cam drive assembly.

13. An internal combustion engine comprising:

a crankshaft including a first end and a second end opposite the first end, the crankshaft defining a crank axis, the crankshaft rotatable about the crank axis in a first direction;

a camshaft defining a camshaft axis, the camshaft rotatable about the camshaft axis;

a balance mass rotatable around the crank axis in a second direction opposite the first direction; and

a drive member separated from the crankshaft and coupled to take power off the crankshaft, the drive member having a first output for driving the camshaft and a second output for driving the balance mass.

14. The internal combustion engine of claim 13 , wherein the drive member includes two separately formed toothed wheels fixedly secured to be integrally rotatable.

15. The internal combustion engine of claim 13 , further comprising a camshaft drive wheel to receive the first output from the drive member to drive the camshaft, and a toothed wheel that receives the second output from the drive member to integrally rotate with the balance mass.

16. The internal combustion engine of claim 13 , wherein the drive member drives the cam shaft at a reduced speed relative to the crankshaft, and drives the balance mass at an increased speed relative to the camshaft.

17. The internal combustion engine of claim 13 , further comprising a first toothed wheel rotatable with the crankshaft about the crank axis to drive the drive member and a second toothed wheel that receives the second output from the drive member to drive the balance mass.

18. The internal combustion engine of claim 17 , wherein the second toothed wheel is integrally rotatable with the balance mass.

19. The internal combustion engine of claim 13 , further comprising a camshaft drive wheel that receives the first output from the drive member to drive the camshaft.

20. The internal combustion engine of claim 19 , wherein the camshaft is a first camshaft and the internal combustion engine further comprises a second camshaft driven by the camshaft drive wheel.

21. The internal combustion engine of claim 13 , wherein the camshaft, the balance mass, and the drive member are supported by a frame, and wherein the camshaft, the balance mass, the drive member, and the frame define a balancer module that is removably coupled to one of the ends of the crankshaft.

22. The internal combustion engine of claim 13 , wherein the balance mass is rotatably supported on the crankshaft such that the balance mass and the crankshaft rotate concentrically with a shared center of rotation at the crank axis.

23. An internal combustion engine comprising:

a crankshaft including a first end and a second end opposite the first end, the crankshaft defining a crank axis, the crankshaft rotatable about the crank axis;

a camshaft defining a camshaft axis, the camshaft rotatable about the camshaft axis;

a cam drive assembly operable to transfer rotation from the crankshaft to the camshaft;

a balance mass rotatable around the crank axis; and

a balancer drive assembly operable to drive the balance mass,

wherein a rotatable drive member distanced from the crank axis forms part of a power transmission path from the crankshaft to the balance mass and forms part of a power transmission path from the crankshaft to the camshaft such that the drive member forms an integral part of both the balancer drive assembly and the cam drive assembly.